Showing papers on "Receptive field published in 1989"

Oscillatory responses in cat visual cortex exhibit inter-columnar synchronization which reflects global stimulus properties.

Abstract: A FUNDAMENTAL step in visual pattern recognition is the establishment of relations between spatially separate features. Recently, we have shown that neurons in the cat visual cortex have oscillatory responses in the range 40–60 Hz (refs 1,2) which occur in synchrony for cells in a functional column and are tightly correlated with a local oscillatory field potential. This led us to hypothesize that the synchronization of oscillatory responses of spatially distributed, feature selective cells might be a way to establish relations between features in different parts of the visual field2,3. In support of this hypothesis, we demonstrate here that neurons in spatially separate columns can synchronize their oscillatory responses. The synchronization has, on average, no phase difference, depends on the spatial separation and the orientation preference of the cells and is influenced by global stimulus properties.

Stimulus-specific neuronal oscillations in orientation columns of cat visual cortex

Abstract: In areas 17 and 18 of the cat visual cortex the firing probability of neurons, in response to the presentation of optimally aligned light bars within their receptive field, oscillates with a peak frequency near 40 Hz. The neuronal firing pattern is tightly correlated with the phase and amplitude of an oscillatory local field potential recorded through the same electrode. The amplitude of the local field-potential oscillations are maximal in response to stimuli that match the orientation and direction preference of the local cluster of neurons. Single and multiunit recordings from the dorsal lateral geniculate nucleus of the thalamus showed no evidence of oscillations of the neuronal firing probability in the range of 20-70 Hz. The results demonstrate that local neuronal populations in the visual cortex engage in stimulus-specific synchronous oscillations resulting from an intracortical mechanism. The oscillatory responses may provide a general mechanism by which activity patterns in spatially separate regions of the cortex are temporally coordinated.

Mechanisms of contour perception in monkey visual cortex. I. Lines of pattern discontinuity

Abstract: We have studied the mechanism of contour perception by recording from neurons in the visual cortex of alert rhesus monkeys. In order to assess the relationship between neural signals and perception, we compared the responses to edges and lines with the responses to patterns in which human observers perceive a contour where no line or edge is given (anomalous contour), such as the border between gratings of thin lines offset by half a cycle. With only one exception out of 60, orientation-selective neurons in area V1 did not signal the anomalous contour. Many neurons failed to respond to this stimulus at all, others responded according to the orientation of the grating lines. In area V2, 45 of 103 neurons (44%) signaled the orientation of the anomalous contour. Sixteen did so without signaling the orientation of the inducing lines. Some responded better to anomalous contours than to the optimum bars or edges. Preferred orientations and widths of tuning for anomalous contour and bar or edge were found to be highly correlated, but not identical, in each neuron. Similar to perception, the neuronal responses depended on a minimum number of lines inducing the contour, but not so much on line spacing, and tended to be weaker when the lines were oblique rather than orthogonal to the border. With oblique lines, the orientations signaled were biased towards the orientation orthogonal to the lines, as in the Zollner illusion. We conclude that contours may be defined first at the level of V2. While the unresponsiveness of neurons in V1 to this type of anomalous contour is in agreement with linear filter predictions, the responses of V2 neurons need to be explained. We assume that they sum the signals of 2 parallel paths, one that defines edges and lines and another that defines anomalous contours by pooling signals from end-stopped receptive fields oriented mainly orthogonal to the contour.

Mechanisms of contour perception in monkey visual cortex. II. Contours bridging gaps

Abstract: We have studied the mechanism of contour perception by recording from neurons in the visual cortex of alert rhesus monkeys. We used stimuli in which human observers perceive anomalous contours: A moving pair of notches in 2 bright rectangles mimicked an overlaying dark bar. For control, the notches were closed by thin lines so that the anomalous contours disappeared or half of the figure was blanked, with a similar effect. Orientation-selective neurons were studied. With the receptive fields centered in the gap, 23 of 72 (32%) neurons tested in area V2 responded to the moving “bar” even though the stimulus spared their response fields, and when the notches were closed, their responses were reduced or abolished. Likewise, when half of the figure was removed, the neurons usually failed to respond. Neurons with receptive fields within 4 degrees of the fovea signaled anomalous contours bridging gaps of 1 degree-3.5 degrees. The anomalous-contour responses were compared quantitatively with response field profiles and length-summation curves and found to exceed the predictions by linear-summation and summation- to-threshold models. Summation models also fail to explain the effect of closing lines which add only negligible amounts of light. In V1, only one of 26 neurons tested showed comparable responses, and only with a narrow gap. The others responded only when the stimulus invaded the response field and did not show the effect of closing lines, or failed to respond at all. The contour responses in V2, the nonadditivity, and the effect of closure can be explained by the previously proposed model (Peterhans et al., 1986), assuming that the corners excite end-stopped fields orthogonal to the contour whose signals are pooled in the contour neurons.

Behavioral indices of multisensory integration: Orientation to visual cues is affected by auditory stimuli

Abstract: Physiological studies have demonstrated that inputs from different sensory modalities converge on, and are integrated by, individual superior colliculus neurons and that this integration is governed by specific spatial rules. The present experiments were an attempt to relate these neural processes to overt behavior by determining if behaviors believed to involve the circuitry of the superior colliculus would show similar multisensory dependencies and be subject to the same rules of integration. The neurophysiological-behavioral parallels proved to be striking. The effectiveness of a stimulus of one modality in eliciting attentive and orientation behaviors was dramatically affected by the presence of a stimulus from another modality in each of the three behavioral paradigms used here. Animals trained to approach a low intensity visual cue had their performance significantly enhanced when a brief, low intensity auditory stimulus was presented at the same location as the visual cue, but their performance was significantly depressed when the auditory stimulus was disparate to it. These effects were independent of the animals' experience with the modifying (i.e. auditory) stimulus and exceeded what might have been predicted statistically based on the animals' performance with each single-modality cue. The multiplicative nature of these multisensory interactions and their dependence on the relative positions and intensities of the two stimuli were all very similar to those observed physiologically for single cells. The few differences that were observed appeared to reflect the fact that understanding integration at the level of the single cell requires reference to the individual cell's multisensory receptive field properties, while at the behavioral level populations of receptive fields must be evaluated. These data illustrate that the rules governing multisensory integration at the level of the single cell also predict responses to these stimuli in the intact behaving organism.

Expansion of receptive fields of spinal lamina I projection neurons in rats with unilateral adjuvant-induced inflammation: the contribution of dorsal horn mechanisms.

Abstract: We have physiologically characterized the receptive field properties of lamina I projection neurons with cutaneous input in the lumbar spinal cords of control rats and rats with unilateral adjuvant-induced inflammation of the hindlimb. The majority of cells recorded in rats with inflamed limbs demonstrated properties uncharacteristic of this cell population in control rats, including large receptive fields, discontinuous receptive fields, responsiveness to deep as well as cutaneous tissues and ongoing or bursting spontaneous activity. Cells with complex receptive fields were encountered from less than 6 h to 5 days after induction of inflammation. This time course correlates with the occurrence of hyperalgesia to thermal stimuli. The contributions of nociceptive afferent sensitization and alterations in the physical environment of peripheral receptors to the observed enlargement of receptive fields were examined by testing the responses of cells to localized electrical and thermal stimuli in the absence and presence of local anesthesia. Nociceptive primary afferents did not demonstrate enlarged receptive fields in this model of inflammation. The results imply that the enlargement of receptive fields cannot be accounted for by peripheral sensitization of peripheral nociceptors or physical changes in the environment of peripheral receptors and must therefore involve changes within the central nervous system.

Underlying mechanisms of the response specificity of expansion/contraction and rotation cells in the dorsal part of the medial superior temporal area of the macaque monkey.

Abstract: 1. The dorsal part of medial superior temporal area (MST) has two unique types of visually responsive cells: 1) expansion/contraction cells, which selectively respond to either an expansion or a contraction; and 2) rotation cells, which selectively respond to either a clockwise or a counterclockwise rotation. In addition to selectivity for the mode of motion, both types of cells respond preferentially to movements over a wide field rather than over a small field. With the aim of understanding the underlying mechanisms of these selectivities, we carried out experiments on immobilized monkeys anesthetized with N2O. 2. Expansion/contraction and rotation of a pattern extending over a wide field contain three stimulus factors: 1) the spatial arrangement of different directions of movement, 2) the gradient in the speed of regional movement from the center to the periphery of the stimulus, and 3) the size change of texture components of the pattern in the expansion/contraction and the acceleration of movement of texture components toward the center of the stimulus in the rotation. The contribution of each factor to the activation of the cells was evaluated by comparing the response before and after removing the factor from the stimulus. The moving stimuli that lacked one or two of the factors were produced by the use of a cinematographic animation technique. 3. Withdrawal of the first factor, the spatial arrangement of different directions of movement, reduced the response of both Expansion/contraction and Rotation cells much more severely than either of the other two factors. We concluded that the first factor is far more important for activation than the other two. 4. These results are consistent with the model that Expansion/contraction and Rotation cells receive converging inputs from many directional cells with relatively small receptive fields in different parts of the visual field. Because MST receives strong fiber projections from MT, MT cells are candidates for the input cells. According to the model, if the convergence is organized so that the preferred directions of the input cells are arranged radially, the target cell will be an Expansion/contraction cell; if the input cells are arranged circularly, a Rotation cell will result.

Afferent basis of visual response properties in area MT of the macaque. I. Effects of striate cortex removal

Abstract: The middle temporal area (MT) of the macaque monkey is a region of extrastriate cortex involved in the analysis of visual motion. MT receives strong projections from striate cortex and from area V2, which is dependent on striate for visual responsiveness. Accordingly, the visual properties of MT neurons have been thought to reflect the further processing of its input from striate cortex. We examined the dependence of MT activity on pathways deriving from striate cortex by recording from MT neurons following removal of their striate input. Repeated recordings in area MT were made in 4 hemispheres of anesthetized macaques following either partial or total ablations of striate cortex. Cells in MT were tested for responsiveness, selectivity for direction of motion and direction tuning, and ocular dominance. Receptive fields were also plotted. In an additional animal, we recorded from MT neurons during reversible cooling of the central representation in striate cortex. We found that striate cortex removal or inactivation did not abolish the visual responsiveness of the majority of MT cells. Although the residual responses were generally much weaker than in the intact animal, direction selectivity and binocularity were still present. Moreover, receptive field size and overall topography appeared unaltered.

Cortical Circuits: Synaptic Organization of the Cerebral Cortex Structure, Function, and Theory

Abstract: I Anatomy.- 1 General Organization of the Cerebral Cortex.- Cortical Areas.- Summary.- Lamination.- Summary.- Vertical Arrangements.- Summary.- Neurotransmitters and Receptors in the Cerebral Cortex.- Summary.- Summary of Chapter 1.- 2 Cell Types.- Pyramidal Cells.- Dendrites and Their Relationships With Cortical Laminae.- Collateral Axonal Branches.- Laminar Relationships of Cortical Efferent Cells.- Neurotransmitters of Pyramidal Cells.- Summary.- Nonpyramidal Cells.- Chandelier Cells.- Basket Cells.- Vertically Oriented Neurons.- Spiny Stellate Cells.- Smooth and Sparsely Shiny Local Plexus Neurons.- Cross-Species Correlations of Nonpyramidal Neuronal Types.- Other Morphological Cell Types.- Summary.- Summary of Chapter 2.- 3 Synaptic Connections Between Identified Elements.- Intrinsic Connections of Pyramidal Neurons.- Local Projections of Superficial Pyramids.- Local Projections of Deep Pyramids.- Summary.- Intrinsic Connections of Nonpyramidal Neurons.- Summary.- Synapses of Extrinsic Afferents With Cortical Neurons.- Summary.- Quantitative Aspects of Circuitry Involving Extrinsic Cortical Afferents.- Summary.- Summary of Chapter 3.- General Aspects of Brain Circuitry.- References for Part I.- II Functional Aspects of Cortical Circuitry.- 4 Functional Properties of Cortical Neurons.- Functional Columns.- Physiological Identification of Functional Columns.- Anatomical Demonstration of Functional Columns.- Receptive Field Properties of Cortical Neurons.- Receptive Field Properties of Somatosensory Neurons.- Receptive Field Properties of Visual Neurons.- Laminar Distribution of Functionally Defined Neurons.- Functional Properties of Morphologically Identified Neurons.- Receptive Field Properties of Identified Neurons.- Pyramidal Neurons.- Nonpyramidal Neurons.- Shape of the Dendritic Tree.- Biophysical Properties of Identified Neurons.- Summary of Chapter 4.- 5 Synaptic Circuitry Revealed by Electrophysiology.- Extrinsic Afferents.- Intrinsic Pathways.- Excitatory Interactions.- Inhibitory Interactions.- Summary of Chapter 5.- 6 GABAergic Inhibition in the Cerebral Cortex.- GABA-Mediated Inhibition.- Anatomical Demonstration of GABAergic Neurons.- Physiological Basis of GABA-Mediated Inhibition.- GABAergic Inhibition and Receptive Fields.- Summary of Chapter 6.- General Aspects of Brain Circuitry (Continued).- References for Part II.- III Facts, Theories, and Models.- 7 An Integrative View of Cortical Circuitry.- Synaptic Triads.- Hierarchical Versus Parallel Processing.- Specificity of Synaptic Connections.- Nonselectivity of Synaptic Connections: The Basis for a Selection Process.- Epilogue.- References for Part III.

Gaze-dependent visual neurons in area V3A of monkey prestriate cortex

Abstract: Extracellular recordings from single neurons of the prestriate area V3A were carried out in awake, behaving monkeys, to test the influence of the direction of gaze on cellular activity. The responsiveness to visual stimulation of about half of the studied neurons (88/187) was influenced by the animal's direction of gaze: physically identical visual stimuli delivered to identical retinotopic positions (on the receptive field) evoked different responses, depending upon the direction of gaze. Control experiments discount the possibility that the observed phenomenon was due to changes in visual background or in depth, depending on the direction in which the animal was looking. The gaze effect modulated cell excitability with different strengths for different gaze directions. The majority of these neurons were more responsive when the animal looked contralaterally with respect to the hemisphere they were recorded from. Gaze-dependent neurons seem to be segregated in restricted cortical regions, within area V3A, without mixing with non-gaze-dependent cells of the same cortical area. The most reliable differences between V3A gaze-dependent neurons and the same type of cells previously described in area 7a (Andersen and Mountcastle, 1983) concern the small receptive field size, the laterality of gaze effect, and the lack of straight-ahead facilitated or inhibited neurons in area V3A. Since the present results show that V3A gaze-dependent neurons combine information about the position of the eye in the orbit with that of a restricted retinal locus (their receptive field), we suggest that they might directly encode spatial locations of the animal's field of view in a head frame of reference. These cells might be involved in the construction of an internal map of the visual environment in which the topographical position of the objects reflects their objective position in space instead of reflecting the retinotopic position of their images. Such an objective map of the visual world might allow the stability of visual perception despite eye movement.

Morphologies of rabbit retinal ganglion cells with complex receptive fields.

Abstract: Ganglion cells that had complex receptive field properties, namely, On-Off and On direction-selective cells, orientation-selective cells, local edge detectors, and uniformity detectors (suppressed by contrast cells) were recorded in an isolated superfused rabbit eyecup preparation. Cells were first classified by their characteristic extracellular responses to manually controlled stimuli similar to those which have been used in previous in vivo studies. Ganglion cells were then impaled, confirmed in identity by intracellular recording, and iontophoretically injected with horseradish peroxidase for staining. Twenty-two ganglion cells, which included members of all the major classes mentioned above, were recovered from the visual streak or near periphery. All recovered cells were drawn in camera lucida from flat-mounted retinas and entered into a computer as two-dimensional stick figures; nearly all were three-dimensionally reconstructed to determine the level and manner of dendritic ramification in the inner plexiform layer (IPL). The location of ganglion cell dendrites in sublaminar regions of the IPL was found to be consistent with the hypothesis of a division of the IPL into excitatory On (proximal) and Off (distal) sublaminae, with some qualifications for particular classes. Each of the complex receptive field ganglion cell classes exhibited a distinctive three-dimensional dendritic arborization pattern uniquely associated with that physiological class.

Functional properties of monkey caudate neurons. II. Visual and auditory responses

Abstract: 1. Visual responses of caudate neurons were studied in monkeys trained to fixate on a small spot of light. A visual stimulus (another spot of light) was presented in various contexts of behavior using different behavioral paradigms. Visual receptive fields were usually large and centered on the contralateral hemifield. Among 217 neurons with visual responses, 184 were further classified into subtypes. 2. Visual responses in 64 neurons were not modulated by changing the paradigms (unconditional visual responses). In the other neurons, visual responses were dependent on the behavioral contexts in which the stimulus was presented. Three types of behavioral modulation were found. 3. A saccade-enhanced visual response (n = 37) was the one that was enhanced if the monkey made a saccade to the stimulus on its appearance. The enhancement was spatially selective: the response was depressed if the saccade was directed away from the stimulus. 4. Memory-contingent visual responses (n = 36) were present preferentially when the monkey remembered the location of the stimulus and a few seconds later made a saccade to the remembered location. Responses were greater when the location of the stimulus was randomized between trials. 5. Expectation-contingent visual responses (n = 46) were present preferentially when the stimulus came on while the monkey was not fixating another spot, and the stimulus was related directly to a reward. Unlike the other types, its receptive field included both contralateral and ipsilateral hemifields without a particular preference. 6. A small number of neurons (n = 16) showed a visual response that easily habituated. 7. Latencies of visual responses were usually between 100 and 200 ms. The latencies of the memory-contingent, expectation-contingent, and habituated visual responses tended to be longer than the others and tended to be more variable between trials. 8. Among auditory responsive neurons only a small proportion were related to the tasks. The response was greater to a contralateral sound. It was enhanced if the monkey used the sound as the cue for the future target location. 9. The results suggest that sensory responses of caudate neurons could be used to guide a subsequent sequence of learned behaviors by confirming predicted environmental states, renewing memory, or establishing a motor set.

Efferent neurons and suspected interneurons in S-1 vibrissa cortex of the awake rabbit : receptive fields and axonal properties

Abstract: 1. The behavioral tractability of the rabbit was exploited and enabled, in the fully awake state, receptive-field analysis of antidromically identified efferent neurons within the vibrissa represen...

Visual activity in area V2 during reversible inactivation of area 17 in the macaque monkey.

Abstract: 1. The presence of a direct lateral geniculate nucleus (LGN) input to area V2 raises the possibility that some neurons in this area remain active when area 17 is inactivated. It is also known that many neurons in area MT are visually responsive in the absence of input from area 17. Because MT sends a strong projection to V2, it appears likely that visual activity could be transferred to V2 through this feedback connection when the V1 afferents are disabled. For these reasons, we decided to reexamine the residual visual activity of neurons in V2 during inactivation of area 17. A circular region 16 mm in diameter on the opercular part of area 17 was cooled by a thermoelectric Peltier device, and single- and multiunit activity was recorded in the retinotopically corresponding region of area V2. 2. Because of the proximity of areas V1 and V2, it was necessary to make sure that neurons in V2 could not be directly blocked by cooling applied to V1. Temperature gradients within cortex were measured with a specially designed thermocouple at different heat flows imposed by the Peltier device. Gradients ranged between 2.3 and 5.5 degrees C/mm. Knowing the temperature gradients and the temperature of the cooling plate, it was possible to deduce the temperature at a given depth within cortex. With this method we measured the blocking temperatures of neurons in area 17, i.e., the temperature at which neurons completely ceased to respond to optimal visual stimulation. Blocking temperatures ranged between 4 and 18 degrees C, values that are substantially lower than those reported in previous papers. Knowing the blocking temperatures, it was possible to determine the cooling-plate temperature necessary to entirely block the region of V1 under the cooling plate. Using the temperature gradients, we then calculated the depth of recording for which V2 neurons could not be directly blocked by the cold. For this reason, all our recordings were made in or near the fundus of the lunate sulcus. 3. During cryoblocking of V1, we recorded 154 sites in penetrations normal to area V2. All these sites had receptive fields included within the visual-field region coded in the cooled zone. In addition, we recorded 55 sites in tangential penetrations aimed at traveling in V2 for long distances. Among these 209 sites, only 3 could be considered as unambiguously active when V1 was blocked. Two of these sites were located at or close to the V2-V3 border.(ABSTRACT TRUNCATED AT 400 WORDS)

Nonlinear summation of M- and L-cone inputs to phasic retinal ganglion cells of the macaque

Abstract: We have studied the responses of ganglion cells in the macaque retina to stimuli that alternate in color. With most color combinations, the phasic retinal ganglion cells, which sum input from M- and L-cones in both center and surround, showed a response with twice the alternation frequency at equal luminance. This frequency doubling was directly related to the degree to which the M- and L-cones were stimulated out-of-phase with one another, and thus varied with the wavelength combinations used. It was absent with wavelength combinations that lay along tritanopic confusion lines, when at equal luminance the M- and L-cones are not modulated. Such a frequency-doubled response is evidence for a nonlinearity at or before M- and L-cone summation. The effect became much smaller or was abolished when the receptive field center alone was stimulated, indicating that its mechanism lies in the surround or in a center-surround interaction. Also, it was much more marked at high luminance levels, being almost absent at retinal illuminances below 100 td. Its origin is not clear, but it seems to derive more from the L- than the M-cone. The results imply that phasic cells, through this nonlinearity, could respond to the red-green equal luminance borders used in some psychophysical experiments.

Participation of prefrontal neurons in the preparation of visually guided eye movements in the rhesus monkey.

Abstract: 1. We recorded from 257 neurons in the banks of the posterior third of the principal sulcus of two rhesus monkeys trained to look at a fixation point and make saccades to stimuli in the visual periphery. Sixty-six percent (220/257) discharged or were suppressed in association with one or more aspects of the tasks we used. 2. Fifty-eight percent (151/257) of the neurons responded to the appearance of a spot of light in some part of the contralateral visual field. Cells did not seem to have absolute requirements for stimulus shape, size, or direction of motion. 3. Thirty-six percent (29/79) of visually responsive neurons tested quantitatively gave an enhanced response to the stimulus in the receptive field when the monkey had to make a saccade to the stimulus when its appearance was synchronous with the disappearance of the fixation point (synchron task). Twenty-nine percent (19/57) of the neurons gave an enhanced response to the stimulus when the monkey had to make a saccade to the stimulus some time after it appeared (delayed-saccade task). In general, enhancement in the synchron task correlated well with enhancement in the delayed-saccade task. 4. Enhancement was spatially specific. It did not occur when the monkey made a saccade to a stimulus outside the receptive field even though there was a stimulus within the receptive field. 5. Twenty-three percent (27/117) of neurons studied in the delayed-saccade task gave two bursts, one at the appearance of the stimulus and a second one around the saccade. This second burst generally did not occur when the monkey made the same saccade to a remembered target, but instead required the presence of the visual stimulus, and so we describe it as a reactivation of the visual response. Reactivation was also spatially specific. 6. The latency from reactivation to the beginning of the saccade ranged from 160 ms before the saccade to the beginning of the saccade. Reactivation usually continued for several hundred milliseconds after the saccade, sometimes for the duration of the trial. 7. Reactivation and enhancement are not the same mechanism. Although some cells showed both phenomena there was no correlation between enhancement and reactivation. 8. Cells that showed reactivation in the saccade task also showed reactivation at a weaker level in a suppressed-saccade task. In this task the monkeys had to hold fixation despite the disappearance of the fixation point and the continued presence of the peripheral stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)

Entropy reduction and decorrelation in visual coding by oriented neural receptive fields

Abstract: In biological visual systems, it is not obvious whether coding efficiency as measured by mutual information among the neurons is a factor that explains any of their properties. The center/surround receptive field profiles of neurons in the retina and geniculate are far from an orthogonal set, but a given neuron can still be regarded as a decorrelator of the incoming signal in the sense that it responds primarily to changes in the image. At the level of the brain's visual cortex, the introduction of the new variable of orientation selectivity can be regarded not only as a means for providing orientation labels for image structure, but also more basically as an effective decorrelator of the neural representation. The present image coding simulations, based on quantitative neurobiological data about the code primitives, provide measures of the bit-rate efficiency of such oriented, quadrature, neural codes. Demonstrations of data compression to below 1 bit/pixel in cortically-based, quadrature self-similar wavelet image codes are also provided. >

Quantitative measurements of receptive field changes during antagonism of GABAergic transmission in primary somatosensory cortex of cats.

Abstract: In cortical area 3b of cats, responses of 76 single neurons to punctate indentations were recorded before and during iontophoretic administration of bicuculline methiodide (BMI), a GABAergic antagonist, at levels that did not affect spontaneous activity. Constant amplitude indentations were applied to selected sites along distalproximal and radial-ulnar axes that intersected the most sensitive area in the receptive field. Profiles of response magnitudes were used to measure receptive field dimensions before and during antagonism of GABAergic inhibition. Blockade of GABAergic transmission caused receptive field dimensions of 48 rapidly-adapting neurons to increase an average 141%, or nearly 2.5 times their original size. Analysis of the spatial distribution of inhibition indicated that in-field inhibition was larger than surround inhibition. During BMI administration, response latency was significantly longer for response elicited from the expanded territory than for responses elicited from within the original receptive field, suggesting that receptive field expansion might be mediated by multisynaptic intracortical connections. The magnitude of receptive field expansion was independent of receptive field size or peripheral location. In a substantial number of neurons, however, BMI produced asymmetric expansions that extended only in the proximal direction. For 9 slowly-adapting neurons, BMI produced measureable increases in receptive field dimensions, but these changes were significantly smaller than the changes in rapidly-adapting neurons.

Alpha and delta ganglion cells in the rat retina

Abstract: In the rat retina a distinctive class of large ganglion cell was demonstrated by intracellular staining with Lucifer Yellow and with reduced silver staining. They are referred to as alpha cells because they resemble the alpha cells of other mammalian retinae. A second class, called delta cells, is also described. Both classes belong to the type I group defined by Perry (Proc. R. Soc. Lond. [Biol.] 204:363-375, '79). The dendritic trees of both classes stratify in either an inner or outer lamina of the inner plexiform layer which presumably corresponds to an on/off dichotomy in the response to light. Rat alpha cells constitute 2-4% of all ganglion cells, and their density, size, and detailed morphological appearance change with retinal location. Inner and outer stratifying alpha cells of the rat show significant differences compared to those of other mammals. In central retina (at the large cell density maximum) the densities and dendritic field sizes of inner and outer alpha cells are approximately equal. However, in peripheral retina outer alpha cells are up to three times more numerous and have dendritic field areas only one-third the size of those of the inner alpha cells. The maximal density is about 110 alpha cells/mm2; peripheral densities are about 30/mm2. The smallest central dendritic field diameters are 220 microns. Peripheral dendritic field diameters are 350-550 microns for outer and 570-790 microns for inner alpha cells. Each subpopulation is distributed in a regular mosaic, and the territorial arrangement of the dendritic fields provides a homogeneous coverage of the retina. The dendritic coverage is three- to 3.6-fold for each subpopulation, irrespective of their other quantitative differences. Eccentricity-dependent receptive field sizes of the alpha cells are predicted from the morphological data.

Interactions of visual stimuli in the receptive fields of inferior temporal neurons in awake macaques.

Abstract: Monkeys were trained to perform a fixation task and a visual discrimination task. During the fixation task, one or two light bars were presented at different positions in the receptive fields of TE neurons. During the discrimination task, the animal was required to detect the positive stimulus when one or two of the paired small colored spots or two-dimensional patterns were presented. In both behavioral conditions, when the two light stimuli were presented simultaneously, almost none of the TE neurons showed an increase in responding over the single stimulus condition; the response was usually similar or less than the stronger response in the single stimulus condition. In the neurons that responded selectively to the discriminanda during the discrimination task, various interactions between the two antagonistic stimuli occurred depending on the location or the effectiveness of the two stimuli. These results may be related to gain control mechanisms in the wide receptive fields of TE neurons.

Long-term changes in discharge behaviour of cat dorsal horn neurones following noxious stimulation of deep tissues.

Abstract: Certain pathological types of afferent input are supposed to lead to long-term changes in the responsiveness of dorsal horn neurones. This mechanism might be of importance for the development of neurological disturbances such as chronic pain. The present study was undertaken in order to find out whether dorsal horn neurones— particularly those processing input from deep tissues— exhibit long-lasting changes in response behaviour after a short-lasting noxious stimulation of deep tissue. In anaesthetized cats, the impulse activity of single dorsal horn cells was recorded extracellularly with glass microelectrodes. In a small number of cells that had multiple receptive fields (RFs), the algesic agent bradykinin was injected into a muscle RF and the properties of all RFs retested at regular time intervals. Following noxious chemical stimulation of one RF, the injected and the other RFs of the same neurone often showed changes which consisted of an increase in size, a lowering of mechanical threshold and appearance of new RFs. In an attempt to assess the influence of a single noxious stimulus on the entire population of dorsal horn cells, the properties of a greater sample of neurones were compared before and after injection of bradykinin into the deep tissues of the hind limb. Every cell encountered was classified as being driven by (1) cutaneous receptors only, (2) deep receptors only, (3) both input sources, or (4) electrical stimulation only (cell without receptive field). Following injection of bradykinin, the proportion of cells with both deep and cutaneous input and of those having background activity rose, and the percentage of cells without a receptive field decreased. The data indicate that any noxious manipulation of the hind limb may elicit long-lasting changes in the response behaviour of dorsal horn neurones. This assumption was supported by the finding that in animals in which the hind limb had been operated on, the proportion of cells with deep and cutaneous input was significantly higher and that of cells with exclusively deep input lower than in animals with an intact hind limb. Transferring these findings to the clinical situation, the data suggest that the increase in size of the RFs and the appearance of new RFs after a noxious stimulus might reflect the spread or irradiation of deep pain. Likewise, the increase in convergence of deep and cutaneous afferents might be of relevance for the referral of deep pain to the skin, while the decrease in mechanical threshold of deep RFs remote to the location of the noxious stimulus might be the neurophysiological basis of referred tenderness.

Cholinergic modulation of frequency receptive fields in auditory cortex: I. Frequency‐specific effects of muscarinic agonists

Abstract: Previously we reported that acetylcholine (ACh) and acetyl-beta-meth- acholine (MCh) modify responses of neurons in auditory cortex to individual frequencies. The purpose of this study was to determine whether muscarinic agorists produce frequency-specific alterations or general changes in cellular responses. Frequency- specific modifications would be evident in alterations of frequency receptive fields (FRF) that differed across frequencies while general effects would be seen as changes that were more or less the same over frequencies. Responses of single neurons to designated sets of tones were recorded in the auditory cortex of chronically prepared awake cats before, during, and following ejection of ACh or MCh by iontophoresis or micropi.essure using multibarrel micropipettes. Frequency receptive fields were determined tiy presenting isointensity tones across a range of frequencies including the cell's best frequency (BF) to tone onset. FRF for "off" and "sustained (through)" responses were also determined quantitatively. The effects of ACh and MCh were predominantly frequency-specific (77%, 39/51 cells); general changes (19%, 10/51) and no effects (4%, 2/51) were less likely. Frequency-specific effects involved both facilitation and reduction of the same response component to different frequencies within the same neuron. For responses to tone onset (but not "through and "off responses), agonists were more likely to produce a decrease at the BF while simultaneously increasing responses to other frequencies. Agonists could increase or decrease frequency selectivity. Effects of agonists could be blocked by atropine, suggesting involvement of muscarinic receptors.

Centrifugal directional bias in the middle temporal visual area (MT) of the macaque.

Abstract: We have examined the distribution of preferred directions of motion for neurons in the middle temporal visual area (MT) of the macaque. We found a marked anisotropy favoring directions that are oriented away from the center of gaze. This anisotropy is present only among neurons with peripherally located receptive fields. This peripheral centrifugal directionality bias corresponds well to the biased distribution of motions characteristic of optic flow fields, which are generated by displacement of the visual world during forward locomotion. The bias may facilitate the processing of this common form of visual stimulation and could underlie previously observed perceptual anisotropies favoring centrifugal motion. We suggest that the bias could arise from exposure of modifiable cortical circuitry to a naturally occurring form of selective visual experience.

Quantitative analysis of visual receptive fields of neurons in nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract in macaque monkey.

Abstract: 1. The visual receptive field properties of neurons in the nucleus of the optic tract (NOT) in the pretectum and the dorsal terminal nucleus (DTN) of the accessory optic tract were analyzed quantit...

Morphologies of rabbit retinal ganglion cells with concentric receptive fields.

Abstract: Rabbit retinal ganglion cells with concentric receptive fields were intracellularly recorded and stained in the isolated superfused eyecup preparation to relate specific physiological response properties to dendritic morphology. Concentric ganglion cells, as traditionally defined, were those that had On or Off centers with antagonistic surrounds but lacked complex response properties such as direction or orientation selectivity. Concentric cells were classified into different groups by extracellular recordings of their On- or Off-center response sign, excitatory receptive field center size, linearity of spatial summation, and brisk vs. sluggish and transient vs. sustained responses to step changes in light intensity. The cells were then impaled, confirmed in identity during intracellular recording, and iontophoretically injected with horseradish peroxidase for histological analysis. Twenty-three concentric ganglion cells were recovered and morphometrically analyzed. Their physiological response properties were found to be related to a number of underlying two- and three-dimensional attributes of the cell's dendritic branching patterns. The dendrites of all 20 brisk concentric cells and two of the three sluggish cells were found to ramify narrowly in either the proximal or distal half of the inner plexiform layer, corresponding to whether they are On center or Off center, respectively. One of the sluggish concentric cells was found to have a more complex, partially bistratified ramification. Physiologically identified brisk-sustained-linear, brisk-transient-nonlinear, brisk-transient-linear, and at least two classes of sluggish concentric ganglion cells were stained. Each of these physiological classes appears to exhibit a distinct and identifiable dendritic branching pattern.

Structure-function relationships in rat brainstem subnucleus interpolaris: IV. Projection neurons

Abstract: In a companion paper (Jacquin et al., '89), the structure and function of local circuit (LC) neurons in spinal trigeminal (V) subnucleus interpolaris (Sp Vi) were described. The present report provides similar data for 44 projection neurons in Sp Vi. Of these, 25 thalamic, 16 cerebellar, 2 superior collicular, and 1 inferior olivary projecting neurons were studied. The majority responded to vibrissa(e) deflection, and all except 4 of these had multivibrissae receptive fields. The remainder were responsive to either guard hair deflection or indentation of glabrous skin. Latencies to V ganglion shocks were suggestive of monosynaptic activation from the periphery. SpVi projection neurons were topographically organized in a manner consistent with that of their primary afferent inputs. Nonvibrissa sensitive cells had diverse morphologies. Morphometric analyses of the more heavily sampled thalamic and cerebellar projecting, vibrissa(e)-sensitive cells indicated the following. (1) As compared to LC neurons, projection neurons had bigger receptive fields, cell bodies, dendritic trees, and axons; less circular dendritic trees; a greater preponderance of spiny dendrites and fewer axon collaterals in Sp Vi. (2) Dendritic tree extent correlated significantly with receptive field size, thus suggesting that dendritic tree size is one mechanism contributing to receptive field size in vibrissae-sensitive projection neurons. (3) V thalamic cells had significantly bigger receptive fields and dendritic trees, and also give off more local axon collaterals, than V cerebellar neurons. Collicular and inferior olivary projecting neurons shared structural and functional attributes with other Sp Vi long-range projecting cells. Structure-function relationships exist for vibrissa-sensitive projection neurons in Sp Vi. The relevant parameters correlating with projection neuron morphology are receptive field size and projection status, whereas for Sp Vi LC neurons the relevant correlative parameter is peripheral receptor association.

Organized arrangement of orientation-sensitive relay cells in the cat's dorsal lateral geniculate nucleus

Abstract: We studied the physiological orientation biases of over 700 relay cells in the cat9s dorsal lateral geniculate nucleus (LGNd). Relay cells were sampled at regular intervals along horizontally as well as vertically oriented electrode penetrations in a fashion analogous to that used previously in studies of visual cortex (Hubel and Wiesel, 1962). The strengths of the orientation biases and the distributions of the preferred orientations were determined for different classes of relay cells, relay cells in different layers of the LGNd, and relay cells subserving different parts of the visual field. We find that, at the population level, LGNd cells exhibit about the same degree of orientation bias as do the retinal ganglion cells providing their inputs (see also Soodak et al., 1987). Also, as in the retina (Levick and Thibos, 1982; Leventhal and Schall, 1983), most LGNd cells tend to prefer stimuli oriented radially, i.e., parallel to the line connecting their receptive fields to the area centralis projection. However, the radial bias in the LGNd is weaker than in the retina. Moreover, there is a relative overrepresentation of cells preferring tangentially oriented stimuli in the LGNd but not in the retina. As a result of the overrepresentation of cells preferring radial and tangential stimuli, the overall distribution of preferred orientations varies in regions of the LGNd subserving different parts of the visual field. Reconstructions of our electrode penetrations provide evidence that, unlike in the retina, cells having similar preferred orientations are clustered in the LGNd. This clustering is apparent for all cell types and in all parts of laminae A and A1. The tendency to cluster according to preferred orientation is evident for cells preferring radially, intermediately, and tangentially oriented stimuli and thus is not simply a reflection of the radial bias evident among retinal ganglion cells at the population level. It is already known that cells having inputs from different eyes, on-center, off-center, X-, Y-, W-type, and color-sensitive ganglion cells are distributed nonrandomly in the LGNd of cats and monkeys (for review, see Rodieck, 1979; Stone et al., 1979; Lennie, 1981; Stone, 1983). The finding that relay cells having similar preferred orientations are also distributed nonrandomly suggests that the initial sorting of virtually all properties segregated in visual cortex may begin in the LGNd.