Showing papers on "Receptive field published in 1992"
TL;DR: Parietal cortex both anticipates theretinal consequences of eye movements and updates the retinal coordinates of remembered stimuli to generate a continuously accurate representation of visual space.
Abstract: Every eye movement produces a shift in the visual image on the retina. The receptive field, or retinal response area, of an individual visual neuron moves with the eyes so that after an eye movement it covers a new portion of visual space. For some parietal neurons, the location of the receptive field is shown to shift transiently before an eye movement. In addition, nearly all parietal neurons respond when an eye movement brings the site of a previously flashed stimulus into the receptive field. Parietal cortex both anticipates the retinal consequences of eye movements and updates the retinal coordinates of remembered stimuli to generate a continuously accurate representation of visual space.
1,902 citations
TL;DR: The results indicate that the topographic reorganization within the cortex was largely due to synaptic changes intrinsic to the cortex, perhaps through the plexus of long-range horizontal connections.
Abstract: THE adult brain has a remarkable ability to adjust to changes in sensory input. Removal of afferent input to the somatosensory, auditory, motor or visual cortex results in a marked change of cortical topography1–10. Changes in sensory activity can, over a period of months, alter receptive field size and cortical topography11. Here we remove visual input by focal binocular retinal lesions and record from the same cortical sites before and within minutes after making the lesion and find immediate striking increases in receptive field size for cortical cells with receptive fields near the edge of the retinal scotoma. After a few months even the cortical areas that were initially silenced by the lesion recover visual activity, representing retinotopic loci surrounding the lesion. At the level of the lateral geniculate nucleus, which provides the visual input to the striate cortex, a large silent region remains. Furthermore, anatomical studies show that the spread of geniculocortical afferents is insufficient to account for the cortical recovery. The results indicate that the topographic reorganization within the cortex was largely due to synaptic changes intrinsic to the cortex, perhaps through the plexus of long-range horizontal connections.
830 citations
TL;DR: Adult owl monkeys were trained to detect differences in the frequency of a tactile flutter-vibration stimulus above a 20-Hz standard and the cortical representations of the trained hands were substantially more complex in topographic detail than the representations of unstimulated hands or of passively stimulated control hands.
Abstract: 1. Adult owl monkeys were trained to detect differences in the frequency of a tactile flutter-vibration stimulus above a 20-Hz standard. All stimuli were delivered to a constant skin site restricted to a small part of a segment of one finger. The frequency-difference discrimination performance of all but one of these monkeys improved progressively with training. 2. The distributed responses of cortical neurons ("maps") of the hand surfaces were defined in detail in somatosensory cortical area 3b. Representations of trained hands were compared with those of the opposite, untrained hand, and to the area 3b representations of hands in a second set of monkeys that were stimulated tactually in the same manner while these monkeys were attending to auditory stimuli (passive stimulation controls). 3. The cortical representations of the trained hands were substantially more complex in topographic detail than the representations of unstimulated hands or of passively stimulated control hands. 4. In all well-trained monkeys the representations of the restricted skin location trained in the behavioral task were significantly (1.5 to greater than 3 times) greater in area than were the representations of equivalent skin locations on control digits. However, the overall extents of the representations of behaviorally stimulated fingers were not larger than those of control fingers in the same hemisphere, or in opposite hemisphere controls. 5. The receptive fields representing the trained skin were significantly larger than receptive fields representing control digits in all but one trained monkey. The largest receptive fields were centered in the zone of representation of the behaviorally engaged skin, but they were not limited to it. Large receptive fields were recorded in a 1- to 2-mm-wide zone in the area 3b maps of trained hands. 6. Receptive-field sizes were also statistically significantly larger on at least one adjacent, untrained digit when compared with the receptive fields recorded on the homologous digit of the opposite hand. 7. There was an increase in the percent overlaps of receptive fields in the cortical zone of representation of the trained skin. A significant number of receptive fields were centered on the behaviorally trained skin site. 8. The effects of increased topographic complexity, increased representation of the trained skin location, increased receptive-field size, and increased receptive-field overlap were not observed in the representations of the untrained hands in these same monkeys. Only modest increases in topographic complexity were recorded in the representations of passively stimulated hands, and no effects on receptive-field size or overlap were noted.(ABSTRACT TRUNCATED AT 400 WORDS)
791 citations
TL;DR: A functional link between the activity of direction selective neurons and perceptual judgements of motion direction is demonstrated, and monkeys indicated that motion was in the neurons' preferred direction more frequently on stimulated trials than on nonstimulated trials.
Abstract: Physiological and behavioral evidence suggests that the activity of direction selective neurons in visual cortex underlies the perception of moving visual stimuli. We tested this hypothesis by measuring the effects of cortical microstimulation on perceptual judgements of motion direction. To accomplish this, rhesus monkeys were trained to discriminate the direction of motion in a near-threshold, stochastic motion display. For each experiment, we positioned a microelectrode in the middle of a cluster of neurons that shared a common preferred direction of motion. The psychophysical task was then adjusted so that the visual display was presented directly over the neurons’ receptive field. The monkeys were required to discriminate between motion shown either in the direction preferred by the neurons or in the opposite direction. On half the trials of an experiment, we applied electrical microstimulation while monkeys viewed the motion display. We hypothesized that enhancing the neurons’ discharge rate would introduce a directionally specific signal into the cortex and thereby influence the monkeys’ choices on the discrimination task. We compared the monkeys’ performance on “stimulated” and “nonstimulated” trials in 139 experiments; all trials within an experiment were presented in random order. Statistically significant effects of microstimulation were obtained in 89 experiments. In 88 of the 89 experiments with significant effects (97%), the monkeys indicated that motion was in the neurons’ preferred direction more frequently on stimulated trials than on nonstimulated trials. The data demonstrate a functional link between the activity of direction selective neurons and perceptual judgements of motion direction.
603 citations
TL;DR: The results suggest that principal vibrissa data are relayed radially in a column of neurons before parallel relay to adjacent columns, and surround receptive fields of barrel cells in rat S1 cortex appear to be constructed intracortically.
Abstract: 1. Extracellular spike recordings were made from single cells in various layers of barrel cortex in adult rats anesthetized with urethan. Response magnitude and latency differences to brief 1.14 degrees deflections of mystacial vibrissae of center (principal) and surround receptive-field vibrissae were measured. Latency differences for pairs of cells in the same penetration to stimulation of the principal vibrissa were also collected. In separate experiments the domains of layer IV cells were mapped for their influence by a single vibrissa and their latencies to this vibrissa were recorded. In all experiments precise locations of layer IV cells in each penetration were identified using dye-lesioning and cytochrome oxidase staining of tangential sections. 2. The results suggest that principal vibrissa data are relayed radially in a column of neurons before parallel relay to adjacent columns. To the principal vibrissa, layers IV and Vb neurons discharged earliest, with layers II and III on average 2 and 3 ms later, respectively. Serial relay from layers IV to III to II was suggested to be the most common event. Although layer Va cells fired next, a single-column organization is not suggested for them because differences in latency or response magnitude to their principal and immediate surround vibrissae were not significant. Layer II, III and IV cells showed no statistical difference in latency to the nearest surround vibrissa but fired significantly later than to their principal input. 3. Because, from our previous studies, surround receptive fields of barrel cells in rat S1 cortex appear to be constructed intracortically, these data suggest a parallel column-column relay for their construction. Horizontal relay between barrels occurred first within the septae between barrels. Mean intracortical transmission velocities were calculated at approximately 0.05 m/s for column-column information transfer.
415 citations
TL;DR: The response to an optimally oriented stimulus of both simple and complex cells in the cat's striate visual cortex can be suppressed by the superposition of an orthogonally oriented drifting grating, referred to as cross-orientation suppression, whose spatial organization and tuning characteristics are examined.
Abstract: 1. The response to an optimally oriented stimulus of both simple and complex cells in the cat's striate visual cortex (area 17) can be suppressed by the superposition of an orthogonally oriented drifting grating. This effect is referred to as cross-orientation suppression. We have examined the spatial organization and tuning characteristics of this suppressive effect with the use of extracellular recording techniques. 2. For a total of 75 neurons, we have measured the size of each cell's excitatory receptive field by use of rectangular patches of drifting sinusoidal gratings presented at the optimal orientation and spatial frequency. The length and width of these grating patches are varied independently. Receptive-field length and width are determined from the dimensions of the smallest grating patch required to elicit a maximal response. 3. The extent of the area from which cross-orientation suppression originates has been measured in an analogous manner. Each neuron is excited by a patch of drifting grating the same size as the receptive field. The response to this stimulus is modulated by a superimposed patch of grating having an orthogonal orientation. After selecting the spatial frequency that produces maximal suppression, the response of each cell is examined as a function of the length and width of the orthogonal (suppressive) grating patch. Results from 29 cells show that the dimensions of the orthogonal grating patch required to elicit maximal suppression are similar to, or smaller than, the dimensions of the excitatory receptive field. Thus cross-orientation suppression originates from within the receptive field. 4. For some cells the spatial frequency tuning of the suppressive effect is much broader than the spatial frequency tuning for excitation. In these cases it is possible to find a spatial frequency that produces suppression but not excitation. With the use of a suppressive stimulus having this spatial frequency, we examined the strength of suppression as a function of orientation for 11 cells. These tests show that suppression occurs at all orientations, including the preferred orientation for excitation. In some cases, suppression is somewhat stronger at the preferred orientation for excitation than at any other orientation. 5. For 12 cells we varied the relative spatial phase between the optimally oriented and orthogonal gratings. In all cases the magnitude of suppression is largely independent of the relative spatial phase. 6. For three binocular cells we examined whether the suppressive effect of a grating oriented orthogonal to the optimum could be mediated dichoptically.(ABSTRACT TRUNCATED AT 400 WORDS)
359 citations
TL;DR: It is found that further subspecialization occurs within the motion processing stream of the owl monkey, where neurons representing two different kinds of information about visual motion are segregated in columnar fashion within the middle temporal area.
Abstract: THE early stages of primate visual processing appear to be divided up into several component parts so that, for example, colour, form and motion are analysed by anatomically distinct streams1–3. We have found that further subspecialization occurs within the motion processing stream. Neurons representing two different kinds of information about visual motion are segregated in columnar fashion within the middle temporal area of the owl monkey. These columns can be distinguished by labelling with 2-deoxyglucose in response to large-field random-dot patterns. Neurons in lightly labelled interbands have receptive fields with antagonistic surrounds: the response to a centrally placed moving stimulus is suppressed by motion in the surround. Neurons in more densely labelled bands have surrounds that reinforce the centre response so that they integrate motion cues over large areas of the visual field. Interband cells carry information about local motion contrast that may be used to detect motion boundaries or to indicate retinal slip during visual tracking. Band cells encode information about global motion that might be useful for orienting the animal in its environment.
351 citations
TL;DR: By behaviorally training adult owl monkeys to discriminate the temporal features of a tactile stimulus, distributed spatial and temporal response properties of cortical neurons are altered.
Abstract: 1. Temporal response characteristics of neurons were sampled in fine spatial grain throughout the hand representations in cortical areas 3a and 3b in adult owl monkeys. These monkeys had been trained to detect small differences in tactile stimulus frequencies in the range of 20-30 Hz. Stimuli were presented to an invariant, restricted spot on a single digit. 2. The absolute numbers of cortical locations and the cortical area over which neurons showed entrained frequency-following responses to behaviorally important stimuli were significantly greater when stimulation was applied to the trained skin, as compared with stimulation on an adjacent control digit, or at corresponding skin sites in passively stimulated control animals. 3. Representational maps defined with sinusoidal stimuli were not identical to maps defined with just-visible tapping stimuli. Receptive-field/frequency-following response site mismatches were recorded in every trained monkey. Mismatches were less frequently recorded in the representations of control skin surfaces. 4. At cortical locations with entrained responses, neither the absolute firing rates of neurons nor the degree of the entrainment of the response were correlated with behavioral discrimination performance. 5. All area 3b cortical locations with entrained responses evoked by stimulation at trained or untrained skin sites were combined to create population peristimulus time and cycle histograms. In all cases, stimulation of the trained skin resulted in 1) larger-amplitude responses, 2) peak responses earlier in the stimulus cycle, and 3) temporally sharper responses, than did stimulation applied to control skin sites. 6. The sharpening of the response of cortical area 3b neurons relative to the period of the stimulus could be accounted for by a large subpopulation of neurons that had highly coherent responses. 7. Analysis of cycle histograms for area 3b neuron responses revealed that the decreased variance in the representation of each stimulus cycle could account for behaviorally measured frequency discrimination performance. A strong correlation between these temporal response distributions and the discriminative performances for stimuli applied at all studied skin surfaces was even stronger (r = 0.98) if only the rising phases of cycle histogram were considered in the analysis. 8. The responses of neurons in area 3a could not account for measured differences in frequency discrimination performance. 9. These representational changes did not occur in monkeys that were stimulated on the same schedule but were performing an auditory discrimination task during skin stimulation. 10. It is concluded that by behaviorally training adult owl monkeys to discriminate the temporal features of a tactile stimulus, distributed spatial and temporal response properties of cortical neurons are altered.(ABSTRACT TRUNCATED AT 400 WORDS)
313 citations
TL;DR: The findings support the idea that even in adult animals RFs are dynamic, capable of being altered by the sensory context, and propose that the expansion may account for visual illusions, such as perceptual fill-in of stabilized images and illusory contours.
Abstract: Immediately after focal retinal lesions, receptive fields (RFs) in primary visual cortex expand considerably, even when the retinal damage is limited to the photoreceptor layer. The time course of these changes suggests that mere lack of stimulation in the vicinity of the RF accompanied by stimulation in the surrounding region causes the RF expansion. While recording from single cells in cat area 17, we simulated this pattern of stimulation with a pattern of moving lines in the visual field, masking out an area covering the RF of the recorded cell, thereby producing an "artificial scotoma." Over approximately 10 min this masking resulted in a 5-fold average expansion in RF area. Stimulating the RF center caused the field to collapse in size, returning to near its original extent; reconditioning with the masked stimulus led to RF reexpansion. Stimulation in the surrounding region was required for the RF expansion to occur--little expansion was seen during exposure to a blank screen. We propose that the expansion may account for visual illusions, such as perceptual fill-in of stabilized images and illusory contours and may constitute the prodrome of altered cortical topography after retinal lesions. These findings support the idea that even in adult animals RFs are dynamic, capable of being altered by the sensory context.
302 citations
TL;DR: Comparing the sensory responses of POm and VPM cells in urethane‐anesthetized rats is compared as a first step in determining how cortex integrates multiple sensory pathways.
Abstract: The rodent barrel field cortex integrates somatosensory information from two separate thalamic nuclei, the ventral posterior medial nucleus (VPM) and the rostral sector of the posterior complex (POm). This paper compares the sensory responses of POm and VPM cells in urethane-anesthetized rats as a first step in determining how cortex integrates multiple sensory pathways. A complete representation of the contralateral body surface was identified in POm. Trigeminal receptive fields (RFs) of POm and VPM cells were mapped by computer-controlled displacement of individual whiskers; responses were quantified by using peristimulus time histograms. Average RF size was similar in POm (5.1 whiskers) and VPM (4.4 whiskers), but evoked responses in the two nuclei differed significantly according to all other measures. VPM cells were maximally responsive to one single whisker--the "center RF." Stimulating this whisker evoked, on average, a response of 1.4 spikes/stimulus at a latency of 7 ms; surrounding whiskers evoked responses of less than 1 spike/stimulus at latencies of greater than 8 ms. In contrast, POm cells were nearly equally responsive to several whiskers. Quantitative criteria allowed us to designate a single whisker as the "center RF" and stimulating this whisker evoked, on average, a response of 0.5 spikes/stimulus at a latency of 19 ms. VPM cells, but not POm cells, were able to "follow" repeated whisker deflection at greater than 5 Hz. We conclude that, when a single whisker is deflected, VPM activates the related cortical barrel-column at short latency--before the onset of activity in POm. The timing of activation could allow POm cells to modulate the spread of activity between cortical columns.
300 citations
TL;DR: In this article, the responses of cortical neurons evoked by cutaneous stimulation were investigated in the hand representation of cortical area 3a in adult owl monkeys that had been trained in a tactile frequency discrimination task.
Abstract: 1. The responses of cortical neurons evoked by cutaneous stimulation were investigated in the hand representation of cortical area 3a in adult owl monkeys that had been trained in a tactile frequency discrimination task. Cortical representations of the hands in these experimental hemispheres were compared with those representing the opposite, untrained hand, as well as with those representing a passively stimulated hand in a second class of control monkeys. 2. A large cutaneous representation of the hairy and glabrous skin surfaces of the hand emerged in area 3a in each trained hemisphere. 3. With the emergence of cutaneous responses recorded for neurons at many area 3a locations, the normally recorded deep receptor inputs were no longer evident at most of these locations. 4. There was a greater territory of representation of the small area of skin that was stimulated in the behavioral task in trained monkeys, when compared with the representations of corresponding skin sites in the opposite hemisphere of the same monkeys, or to the representations of equivalent skin sites stimulated in passively stimulated control monkeys. 5. There was great variability in the receptive-field properties of neurons responsive to cutaneous inputs among trained monkeys. In most recording sites within the representations of the behaviorally engaged hands, the cutaneous receptive fields were large, extending over a significant part of the glabrous or hairy surfaces of the hand. However, in one monkey, very small, topographically ordered cutaneous receptive fields were recorded over a wide zone of area 3a. 6. The physiologically defined borders between areas 3a and 3b were in register with the cytoarchitectonically defined borders between these two cortical areas in trained and in control monkeys. 7. This study demonstrates that there is a reorganization of the cutaneous and "deep" representation of hand in cortical area 3a, with the main change being an emergence of a large cutaneous representation and the parallel disappearance of a large part of the normal deep representation in this field. These changes are discussed in light of the possible functional roles of cortical area 3a.
TL;DR: Of 265 neurons tested, 95 showed spike activity that was related to some aspects of the visuooculomotor tasks, whereas 66 neurons responded to active or passive limb or body movements, which indicated that visually responsive neurons responded best to parafoveal stimulation.
Abstract: 1 Single-unit recordings were obtained from the subthalamic nuclei of three monkeys trained to perform a series of visuooculomotor tasks The monkeys were trained to fixate on a spot of light on the screen (fixation task) When the spot was turned off and a target spot came on, they were required to fixate on the target quickly by making a saccade Visually guided saccades were elicited when the target came on without a time gap (saccade task) Memory-guided saccades were elicited by delivering a brief cue stimulus while the monkey was fixating; after a delay, the fixation spot was turned off and the monkey made a saccade to the remembered target (delayed saccade task) 2 Of 265 neurons tested, 95 showed spike activity that was related to some aspects of the visuooculomotor tasks, whereas 66 neurons responded to active or passive limb or body movements The task-related activities were classified into the following categories: eye fixation-related, saccade-related, visual stimulus-related, target- and reward-related, and lever release-related 3 Activity related to eye fixation (n = 22) consisted of a sustained spike discharge that occurred while the animal was fixating on a target light during the tasks The activity increased after the animal started fixating on the target and abruptly ceased when the target went off The activity was unrelated to eye position It was not elicited during eye fixation outside the tasks The activity decreased when the target spot was removed 4 Activity related to saccades (n = 22) consisted of a phasic increase in spike frequency that was time locked with a saccade made during the tasks The greatest increases occurred predominantly after saccade onset This activity usually was unrelated to spontaneous saccades made outside the task The changes in activity typically were optimal in one direction, generally toward the contralateral side 5 Visual responses (n = 14) consisted of a phasic excitation in response to a visual probe stimulus or target Response latencies usually were 70-120 ms The receptive fields generally were centered in the contralateral hemifield, sometimes extending into the ipsilateral field The receptive fields included the foveal region in seven neurons; most of these neurons responded best to parafoveal stimulation Peripheral stimuli sometimes suppressed the activity of visually responsive neurons 6 Activity related to target and reward (n = 29) consisted of sustained spike discharge that occurred only when the monkey could expect a reward by detecting the dimming of the light spot that he was fixating(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: The results of this study show that the different receptive fields of multisensory neurons in the cortex of the cat anterior ectosylvian sulcus were in spatial register, and it is this register that determined the manner in which these neurons integrated multiple sensory stimuli.
Abstract: The results of this study show that the different receptive fields of multisensory neurons in the cortex of the cat anterior ectosylvian sulcus (AES) were in spatial register, and it is this register that determined the manner in which these neurons integrated multiple sensory stimuli. The functional properties of multisensory neurons in AES cortex bore fundamental similarities to those in other cortical and subcortical structures. These constancies in the principles of multisensory integration are likely to provide a basis for spatial coherence in information processing throughout the nervous system.
TL;DR: Measurements contradict the mixed-surround hypothesis and imply cone specificity in both centre and surround and the development of new stimuli to measure spatial maps of the linear L-, M- and S-cone inputs to test the hypothesis definitively.
Abstract: Human colour vision depends on three classes of cone photoreceptors, those sensitive to short (S), medium (M) or long (L) wavelengths, and on how signals from these cones are combined by neurons in the retina and brain. Macaque monkey colour vision is similar to human, and the receptive fields of macaque visual neurons have been used as an animal model of human colour processing. P retinal ganglion cells and parvocellular neurons are colour-selective neurons in macaque retina and lateral geniculate nucleus. Interactions between cone signals feeding into these neurons are still unclear. On the basis of experimental results with chromatic adaptation, excitatory and inhibitory inputs from L and M cones onto P cells (and parvocellular neurons) were thought to be quite specific (Fig. 1a). But these experiments with spatially diffuse adaptation did not rule out the 'mixed-surround' hypothesis: that there might be one cone-specific mechanism, the receptive field centre, and a surround mechanism connected to all cone types indiscriminately (Fig. 1e). Recent work has tended to support the mixed-surround hypothesis. We report here the development of new stimuli to measure spatial maps of the linear L-, M- and S-cone inputs to test the hypothesis definitively. Our measurements contradict the mixed-surround hypothesis and imply cone specificity in both centre and surround.
TL;DR: Findings indicate that the transmission of sensory information through the lemniscal pathway occurs independently of the state of cortex, whereas transmission through the paralemniscal pathway depends upon theState of the cortex itself.
Abstract: The projection from the whiskers of the rat to the S-I (barrel) cortex is segregated into two separate pathways--a lemniscal pathway relayed by the ventral posterior medial nucleus (VPM) to cortical barrels, and a paralemniscal pathway relayed by the rostral sector of the posterior complex (POm) to the matrix between, above, and below barrels. Before investigating how the barrel cortex integrates these sensory pathways, it is important to learn more about the influence of the various inputs to the two thalamic nuclei. Based on the greater density of descending versus ascending projections to POm, it seemed likely that corticofugal inputs play an important role in the sensory activity of POm. To test this, the responses of POm and VPM cells to sensory stimuli were measured before, during, and after suppression of the S-I cortex. S-I was suppressed by application of magnesium or by cooling; the status of the barrel cortex was assessed continuously by an electrocorticogram. All VPM cells (n = 8) responded vigorously to whisker movement even when the barrel cortex was profoundly depressed. In contrast, all POm cells (n = 9) failed to respond to whisker movement once the barrel cortex became depressed, typically about 25 minutes after the start of cortical cooling or magnesium application. POm cells regained responsiveness about 30 minutes after the cessation of cortical cooling or the washoff of magnesium. These findings indicate that the transmission of sensory information through the lemniscal pathway occurs independently of the state of cortex, whereas transmission through the paralemniscal pathway depends upon the state of the cortex itself.
TL;DR: The properties of IT neurons are reviewed and it is considered how these properties may underlie the perceptual and mnemonic functions of IT cortex.
Abstract: In primates, inferior temporal (IT) cortex is crucial for the processing and storage of visual information about form and colour. This article reviews the properties of IT neurons and considers how these properties may underlie the perceptual and mnemonic functions of IT cortex. The available evidence suggests that the processing of the facial image by IT cortex is similar to its processing of other visual patterns. Faces and other complex visual stimuli appear to be represented by the pattern of responses over a population of IT neurons rather than by the responses of specific \`feature detectors' or \`grandmother' cells. IT neurons with adult-like stimulus properties are present in monkeys as young as six weeks old.
TL;DR: The results show that MST cells, but not MT cells, are selective for elementary flow components (EFCs) alone or their combination with translation, and that position invariance as observed in MST is compatible with an input arrangement from MT cells matching the selectivity of MST neurons.
Abstract: Optical flow is a rich source of information about the three-dimensional motion and structure of the visual environment Little is known of how the brain derives this information One possibility is that it analyzes first-order elementary components of optical flow, such as expansion, rotation, and shear Using a combination of physiological recordings and modeling techniques, we investigated the contribution of the middle superior temporal area (MST), a third-order cortical area in the dorsal visual pathway that receives inputs from the medial temporal area (MT) The results show (i) that MST cells, but not MT cells, are selective for elementary flow components (EFCs) alone or their combination with translation, (ii) that MST cells selective for an EFC do not extract this component from a more complex motion pattern, and (iii) that position invariance as observed in MST is compatible with an input arrangement from MT cells matching the selectivity of MST neurons
TL;DR: Neurons recorded with extracellular micropipettes in and around the nucleus centralis of the amygdala (Ce) of anesthetized rats were excited or inhibited exclusively or preferentially by noxious stimuli, and these neurons responded to intense transcutaneous electrical stimulation with one or several components of activation or inhibition.
Abstract: 1. Neurons (n = 177) were recorded with extracellular micropipettes in and around the nucleus centralis of the amygdala (Ce), in anesthetized rats. The spontaneous activity of these neurons was variable (0.25 less than 3 less than 35 Hz, n = 175; 10th percentile less than median less than 90th percentile). A majority (80%) of these neurons were excited or inhibited exclusively or preferentially by noxious stimuli. These units were separated into two groups: 1) a group of neurons excited by noxious stimuli (46% of the whole population) and 2) a group of neurons inhibited by noxious stimuli (34% of the whole population). 2. The receptive fields of both groups of neurons were very large: in about one-half the cases the neurons responded similarly from all parts of the body, and in the other cases the responses were greater when the stimuli were applied to a restricted part of the body. 3. Seventy-seven percent of the excited neurons had responses of relatively high magnitudes. In this group, most cells (75%) were exclusively driven by noxious stimuli; the others (25%) were preferentially activated by noxious stimuli. These neurons responded to mechanical (pinch or squeeze) and/or thermal (water bath or water jet greater than 44 degrees C) noxious stimuli with a marked and sustained activation. 4. Sixty percent of the inhibited neurons had a marked decrease of activity in response to noxious stimuli. In this group, most of them (81%) were exclusively inhibited by noxious stimuli, whereas the remainder (19%) were preferentially inhibited by noxious stimuli. These neurons responded to mechanical (pinch or squeeze) and/or thermal (water bath or waterjet greater than 44 degrees C) noxious stimuli with a suppression or a marked and sustained decrease in activity. 5. All of the nociceptive neurons responded to intense transcutaneous electrical stimulation with one or several components of activation or inhibition. According to their latencies, three types of components were distinguished: early, intermediate, and late components. We estimate that the early and the intermediate components would be triggered by the activity of peripheral fibers in the 6- to 20-m/s range and therefore could be in the A delta fibers range, whereas the late component would be triggered by fibers in the 0.5- to 1-m/s range and therefore could be in the C fibers range. 6. The neurons excited or inhibited by noxious stimuli were not homogeneously distributed in and around the Ce.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: Most inferior area 6 visual neurons code the stimulus position in spatial and not in retinal coordinates, which suggests that these visual neurons are involved in generating the stable body-centered frame of reference necesary for programming visually guided movements.
Abstract: Many neurons in inferior area 6, a cortical premotor area, respond to visual stimuli presented in the space around the animal. We were interested to learn whether the receptive fields of these neurons are coded in retinotopic or in body-centered coordinates. To this purpose we recorded single neurons from inferior area 6 (F4 sector) in a monkey trained to fixate a light and detect its dimming. During fixation visual stimuli were moved towards the monkey both within and outside the neurons's receptive field. The fixation point was then moved and the neuron retested with the monkey's gaze deviated to the new location. The results showed that most inferior area 6 visual neurons code the stimulus position in spatial and not in retinal coordinates. It is proposed that these visual neurons are involved in generating the stable body-centered frame of reference necesary for programming visually guided movements.
TL;DR: It is shown that cells in AL exhibit a wide range of auditory tuning properties and suggest that information processing in the amygdala might be fruitfully studied as a direct extension of processing in sensory afferent structures.
Abstract: The lateral amygdaloid nucleus (AL) is anatomically connected with sensory processing structures in the thalamus and cortex and is believed to be critically involved in emotional processing by virtue of these connections. In order to understand further how auditory projections to AL contribute to emotional processing, acoustic response properties of single AL neurons were characterized in rats. Recordings were also made in the posterior striatum dorsal to AL. Many cells in AL and the striatum could be driven by broad-band auditory stimulation with white noise or clicks. Initial onset latencies were typically between 12 and 25 msec. Most cells also had later responses (60–150 msec), and a few only had late responses. In frequency receptive field tests, different classes of cells were identified. One group had relatively clear frequency preferences. Thresholds for these relatively tuned cells tended to be somewhat higher in AL than in the striatum. Frequency preferences for AL cells were always above 10 kHz. Although most striatal cells had preferences for frequencies above 10 kHz, some cells were found with frequencies below 10 kHz as well. A second group of acoustically responsive neurons, much more common in AL than in the striatum, showed no frequency specificity (untuned cells). These responded to a wide range of frequencies, even at intensities near threshold. A third group, found mainly in AL (approximately 60% of the total population of cells examined in AL), exhibited rapid habituation to auditory stimuli. These tended to have high thresholds (80–100 dB). Because these cells habituated so quickly, frequency specificity could not be determined. Responses in AL and the striatum were compared with responses in the “specific” auditory relay nucleus of the thalamus, the ventral division of the medial geniculate body, where cells had shorter onset latencies, narrower tuning functions, and lower-intensity thresholds than cells in AL and striatal areas. These findings show that cells in AL exhibit a wide range of auditory tuning properties and suggest that information processing in the amygdala might be fruitfully studied as a direct extension of processing in sensory afferent structures.
TL;DR: The contribution of the LT spike on the transmission of visually evoked signals through geniculate relay cells to visual cortex and the effects of membrane voltage, and thus the presence or absence of LT spikes, on responses to drifting sine-wave gratings are studied.
Abstract: 1. Thalamic relay cells, including those of the lateral geniculate nucleus, display a low-threshold spike (LT spike), which is a large depolarization due to an increased Ca2+ conductance. Typically riding the crest of each LT spike is a burst of from two to seven action potentials, which we refer to as the LT burst. The LT spike is voltage dependent, because if the cell's resting membrane potential is more depolarized than roughly -60 mV, the LT spike is inactivated, but if more hyperpolarized, the spike is deinactivated and can be activated by a depolarization, such as from an afferent excitatory postsynaptic potential (EPSP). Thalamic relay cells thus display two response modes: a relay or tonic mode, when the cell is depolarized and LT spikes are inactivated, leading to tonic firing of action potentials; and a burst mode, when the cell is hyperpolarized and tends to respond with LT spikes and their associated bursts of action potentials. 2. We were interested in the contribution of the LT spike on the transmission of visually evoked signals through geniculate relay cells to visual cortex. We recorded intracellularly from geniculate cells in an anesthetized, paralyzed, in vivo cat preparation to study the effects of membrane voltage, and thus the presence or absence of LT spikes, on responses to drifting sine-wave gratings. We monitored the visually evoked responses of 14 geniculate neurons (6 X, 7 Y, and 1 unclassified) at different membrane potentials at which LT spikes were inactivated or deinactivated. 3. Changing membrane voltage during visual stimulation switched the response mode of every cell between the relay and burst modes. In the burst mode, LT spikes occurred in phase with the visual stimulus and not at rhythmic intervals uncorrelated to visual stimuli. To any given stimulus cycle, the cell responded usually with an LT burst or a tonic response, and rarely was more than one LT burst evoked by a stimulus cycle. Occasionally a single cycle evoked both an LT burst and tonic response, but always the LT burst occurred first. 4. The spatial tuning characteristics of the cells did not differ dramatically as a function of membrane potential, because the tuning of the LT bursts was quite similar to that of the tonic response component. Although we did not obtain complete temporal tuning properties, we did note that hyperpolarized cells responded reliably with LT bursts at several temporal frequencies. 5. A consistent difference was seen between the LT burst and tonic response components in terms of response linearity.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: The medial division of the medial geniculate body projects to the lateral amygdala and the upper layer of auditory cortex and develops physiological plasticity rapidly during classical conditioning and the effects of learning on frequency receptive fields in the MGm of the guinea pig have been determined.
Abstract: The medial division of the medial geniculate body (MGm) projects to the lateral amygdala and the upper layer of auditory cortex and develops physiological plasticity rapidly during classical conditioning. The effects of learning on frequency receptive fields (RFs) in the MGm of the guinea pig have been determined. Classical conditioning (tone-footshock), as indexed by rapid development of conditioned bradycardia, produced conditioned stimulus (CS)-frequency specific RF plasticity: increased response at the CS frequency with decreased responses at other frequencies, both immediately and after a 1-hr retention period. Sensitization training produced only general changes in RFs. These findings are considered with reference to both the elicitation of amygdala-mediated, fear-conditioned responses and the mechanism of retrieval of information stored in the auditory cortex during acquisition.
TL;DR: The response of macaque ganglion cells to sinusoidally modulated red and green lights was measured as the relative phase, theta, of the lights was varied to provide an account of response phase as a function of theta.
Abstract: 1. We measured the response of macaque ganglion cells to sinusoidally modulated red and green lights as the relative phase, theta, of the lights was varied. 2. At low frequencies, red-green ganglion cells of the parvocellular (PC-) pathway with opponent inputs from middle-wavelength sensitive (M-) and long-wavelength sensitive (L-) cones were minimally sensitive to luminance modulation (theta = 0 deg) and maximally sensitive to chromatic modulation (theta = 180 deg). With increasing frequency, the phase, theta, of minimal amplitude gradually changed, in opposite directions for cells with M- and L-cone centres. 3. At high frequencies (at and above 20 Hz), phasic cells of the magnocellular (MC-) pathway were maximally responsive when theta approximately 0 deg and minimally responsive when theta approximately 180 deg, as expected from an achromatic mechanism. At lower frequencies, the phase of minimal response shifted, for both on- and off-centre cells, to values of theta intermediate between 0 and 180 deg. This phase asymmetry was absent if the centre alone was stimulated with a small field. 4. For PC-pathway cells, it was possible to provide an account of response phase as a function of theta, using a model involving three parameters; phases of the L- and M-cone mechanisms and a L/M cone weighting term. For red-green cells, the phase parameters were monotonically related to temporal frequency and revealed a centre-surround phase difference. The phase difference was linear with a slope of 1-3 deg Hz-1. If this represents a latency difference, it would be 3-8 ms. Otherwise, temporal properties of the M- and L-cones appeared similar if not identical. By addition of a scaling term, the model could be extended to give an adequate account of the amplitude of responses. 5. We were able to activate selectively the surrounds of cells with short-wavelength (S-) cone input to their centres, and so were able to assess L/M cone weighting to the surround. M- and L-cone inputs added linearly for most cells. On average, the weighting corresponded to the Judd modification of the luminosity function although there was considerable inter-cell variability. 6. To account for results from MC-pathway cells, it was necessary to postulate a cone-opponent, chromatic input to their surrounds. We developed a receptive field model with linear summation of M- and L-cones to centre and surround, and with an additional M,L-cone opponent input to the surround.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: It is suggested that distributed common-input cell assemblies are a means of overcoming sparse connectivity and achieving synaptic transmission in the pyramidal network and three different mechanisms are suggested to produce each of the three different degrees of observed spatial and temporal coherence.
Abstract: Visual cortical areas are richly but selectively connected by "patchy" projections. We characterized these connections physiologically with cross-correlograms (CCHs), calculated for neuron pairs or small groups located one each in visual areas 17 and 18 of the cat. The CCHs were then compared to the visuotopic and orientation match of the neurons' receptive fields (RFs). For both spontaneous and visually driven activity, most non-flat correlograms were centered; i.e. the most likely temporal relationship between spikes in the two areas is a synchronous one. Although spikes are most likely to occur simultaneously, area 17 spikes may occur before area 18 or vice versa, giving the cross-correlogram peak a finite width (temporal dispersion). Cross-correlograms fell into one of three groups according to their full-width at half peak height: 1-8 ms (modal width, 3 ms), 15-65 ms (modal width 30 ms), or 100-1000 ms (modal width 400 ms). These classificatory groups are nonoverlapping; the three types of coupling appeared singly and in combination. Neurons whose receptive fields (RFs) are nonoverlapping or cross-oriented may yet be coupled, but the coupling is more likely to be the broadest type of coupling than the medium-dispersed type. The sharpest type of coupling is found exclusively between neurons with at least partially overlapping RFs and mostly between neurons whose stimulus orientation preferences matched to within 22.5 deg. The maximum spatial dispersion observed in the RFs of coupled neurons compares well with the maximum divergence seen anatomically in the A18/A17 projection system. We suggest three different mechanisms to produce each of the three different degrees of observed spatial and temporal coherence. All mechanisms use common input of cortical origin. For medium and broad coupling, this common input arises from cell assemblies split between both sides of the 17/18 projection system, but acting synchronously. Such distributed common-input cell assemblies are a means of overcoming sparse connectivity and achieving synaptic transmission in the pyramidal network.
TL;DR: The findings indicate that modality-specific information is relayed from postcentral cortical areas to SII along parallel channels, with cutaneous inputs transmitted via areas3b and 1, and deep inputs via areas 3a and 2.
Abstract: 1. Selective ablations of the hand representations in postcentral cortical areas 3a, 3b, 1, and 2 were made in different combinations to determine each area's contribution to the responsivity and m...
TL;DR: The anatomical substrates of spatial and color vision in the primate retina are investigated by measuring the immunoreactivity and spatial density of bipolar, amacrine and horizontal cells in the inner nuclear layer of the macaque monkey retina.
Abstract: The anatomical substrates of spatial and color vision in the primate retina are investigated by measuring the immunoreactivity and spatial density of bipolar, amacrine and horizontal cells in the inner nuclear layer of the macaque monkey retina. Bipolar cells can be distinguished from amacrine and horizontal cells by their differential immunoreactivity to antisera against glutamate, glycine, GABA, parvalbumin, calbindin (CaBP D-28K), and the L7 protein from mouse cerebellum. The spatial density of bipolar cells is compared to the densities of photoreceptors and ganglion cells at different retinal eccentricities.
In the centralmost 2 mm, cone bipolar cells outnumber ganglion cells by about 1.4:1. The density of cone bipolar cells is thus high enough to allow for input to different (parasol and midget) ganglion cell classes by different (diffuse and midget) bipolar cell classes. The density gradient of cone bipolar cells follows closely that of ganglion cells in central retina but falls less steeply in peripheral retina. This suggests that the convergence of cone signals to the receptive fields of ganglion cells in the peripheral retina occurs in the inner plexiform layer. The density of cone bipolar cells is 2.5–4 times that of cones at all eccentricities studied, implying that cone connectivity to bipolar cells remains constant throughout the retina.
Different subgroups of bipolar cells are distinguished by their relative immunoreactivity to the different antisera. All rod and cone bipolar cells show moderate to strong glutamate-like immunoreactivity. The bipolar cells that show weak to moderate GABA-like immunoreactivity are also labeled with the antiserum to the L7 protein and are thus identified as rod bipolar cells. Nearly half of all cone bipolar cells showed glycine-like immunoreactivity. The results suggest that the inhibitory neurotransmitter candidates GABA and glycine are segregated respectively in rod and cone bipolar cell pathways. A diffuse, cone bipolar cell type can be identified by the anti-parvalbumin and the anti-calbindin antisera. All horizontal cells show parvalbumin-like immunoreactivity. Nearly all amacrine cells show GABA-like or glycine-like immunoreactivity; a variety of subpopulations also show immunoreactivity to one or more of the other markers used. © 1992 Wiley-Liss, Inc.
TL;DR: In this article, the authors examined the visual response properties of single cells in primary auditory cortex (A1) of rewired animals and compared the responses to those in primary visual cortex (V1).
Abstract: How does cortex that normally processes inputs from one sensory modality respond when provided with input from a different modality? We have addressed such a question with an experimental preparation in which retinal input is routed to the auditory pathway in ferrets. Following neonatal surgical manipulations, a specific population of retinal ganglion cells is induced to innervate the auditory thalamus and provides visual input to cells in auditory cortex (Sur et al., 1988). We have now examined in detail the visual response properties of single cells in primary auditory cortex (A1) of these rewired animals and compared the responses to those in primary visual cortex (V1) of normal animals. Cells in A1 of rewired animals differed from cells in normal V1: they exhibited larger receptive field sizes and poorer visual responsivity, and responded with longer latencies to electrical stimulation of their inputs. However, striking similarities were also found. Like cells in normal V1, A1 cells in rewired animals exhibited orientation and direction selectivity and had simple and complex receptive field organizations. Furthermore, the degree of orientation and directional selectivity as well as the proportions of simple, complex, and nonoriented cells found in A1 and V1 were very similar. These results have significant implications for possible commonalities in intracortical processing circuits between sensory cortices, and for the role of inputs in specifying intracortical circuitry.
TL;DR: Visual receptive fields were mapped inside and outside the cortical representation of the optic disk in the striate cortex of anesthetized and paralyzed Cebus monkeys, and most cells were found to be binocularly driven.
Abstract: Visual receptive fields (RFs) were mapped inside and outside the cortical representation of the optic disk in the striate cortex (area V1) of anesthetized and paralyzed Cebus monkeys. Unexpectedly, most cells were found to be binocularly driven, and the RFs mapped with contralateral-eye stimulation progressed in a topographically appropriate fashion as the optic disk sector was crossed. Activation of these neurons by the contralateral eye was shown to depend on stimulation of the parts of the retina around the optic disk. Outside the optic disk representation, a similar effect was demonstrated by obstructing the "classical" RF with masks 5-10 times larger in size. In all cases, visual stimuli presented around the mask could be used to accurately interpolate the position of the hidden RF. These properties reflect, at a cellular level, the process of "filling in" that allows for completion of the visual image across natural and artificially induced scotomas.
TL;DR: Evidence is provided that the responses of cortical neurons are subject to change by the introduction of locally coincident inputs into a single location, and a capacity for representational plasticity in the neocortex in the absence of peripheral stimulation is demonstrated.
Abstract: Intracortical microstimulation (ICMS) was applied to a single site in the middle cortical layers (III-IV) in the koniocortical somatosensory fields of sodium pentobarbital-anesthetized rats (Sml) and new world monkeys (area 3b). Low-threshold cutaneous receptive fields were defined in the cortical region surrounding the stimulation site prior to and following 2-6 hr of 5 microA ICMS stimulation. ICMS stimulation did not usually affect the receptive field location, size, or responsiveness to tactile stimulation of neurons at the stimulation site. However, the number of cortical neurons surrounding the stimulation site with a receptive field that overlapped with the ICMS-site receptive field increased in all studied animals, resulting in an enlarged cortical representation of a restricted skin region spanning several hundred microns. The mean size of receptive fields changed in some but not all cases. These results provide evidence that the responses of cortical neurons are subject to change by the introduction of locally coincident inputs into a single location, and demonstrate a capacity for representational plasticity in the neocortex in the absence of peripheral stimulation. These experimental observations are consistent with hypotheses that the cerebral cortex comprises radially oriented populations of neurons that share a common input, and that these inputs are shaped by coincident activity (see Edelman, 1978, 1987; Merzenich, 1987; Merzenich et al., 1990; von der Malsburg and Singer, 1988).
TL;DR: It appears that simple- and complex-spike to receptive fields are not always identical or even closely related, and the majority of Purkinje and unidentified neurons that responded to the perturbation had cutaneous receptive fields, although some had proprioceptive fields.
Abstract: 1. Two monkeys were trained to grasp, lift, and hold a device between the thumb and forefinger for 1 s. The device was equipped with a position transducer and strain gauges that measured the horizontal grip force and the vertical lifting or load force. On selected blocks of 20-30 trials, a force-pulse perturbation was applied to the object during static holding to simulate object slip. The animals were required to resist this displacement by stiffening the joints of their wrists and fingers to obtain a fruit juice reward. Single cells in the hand representation area of the paravermal anterior lobe of the cerebellar cortex were recorded during perturbed and unperturbed holding. If conditions permitted, the cell discharge was also recorded during lifting of objects of various weights (15, 65, or 115 g) or different surface textures (sandpaper or polished metal), and when possible the cutaneous or proprioceptive fields of the neurons were characterized with the use of natural stimulation. 2. On perturbed trials, the force pulse was always applied to the manipulandum after it had been held stationary within the position window for 750 ms. The perturbation invariably elicited a reflexlike increase of electromyographic (EMG) activity in wrist and finger muscles, resulting in a time-locked increase in grip force that peaked at a latency between 50 and 100 ms. 3. The object-slip perturbation had a powerful effect on cerebellar cortical neurons at a mean latency of 45 +/- 14 (SD) ms. Reflexlike increases or decreases in simple spike discharge occurred in 55% (53/97) of unidentified cells and 49% (21/43) of Purkinje cells recorded in the anterior paravermal and lateral cerebellar cortex. 4. The perturbation failed to evoke complex spike responses from any of the Purkinje cells examined. All the perturbation-evoked activity changes involved modulation of the simple spike discharge. The perturbations stimulated the simple-spike receptive field of most Purkinje cells recorded here, which suggests that the short-latency unit responses were triggered by afferent stimulation. Only one Purkinje cell was found with a distinct complex-spike receptive field on the thumb, but this neuron did not respond to the perturbation. It appears that simple- and complex-spike to receptive fields are not always identical or even closely related. 5. The majority of Purkinje and unidentified neurons that responded to the perturbation had cutaneous receptive fields, although some had proprioceptive fields. Seventy-seven neurons were examined for peripheral receptive fields and were also tested with the perturbation.(ABSTRACT TRUNCATED AT 400 WORDS)