Showing papers on "Receptive field published in 2002"
TL;DR: It is found that monosynaptic horizontal connections within area V1 are of an appropriate spatial scale to mediate interactions within the SF of V1 neurons and to underlie contrast-dependent changes in SF size, which could represent an anatomical substrate for contextual modulation and global-to-local integration of visual signals.
Abstract: Contrast-dependent changes in spatial summation and contextual modulation of primary visual cortex (V1) neuron responses to stimulation of their receptive field reveal long-distance integration of visual signals within V1, well beyond the classical receptive field (cRF) of single neurons. To identify the cortical circuits mediating these long-distance computations, we have used a combination of anatomical and physiological recording methods to determine the spatial scale and retinotopic logic of intra-areal V1 horizontal connections and inter-areal feedback connections to V1. We have then compared the spatial scales of these connectional systems to the spatial dimensions of the cRF, spatial summation field (SF), and modulatory surround field of macaque V1 neurons. We find that monosynaptic horizontal connections within area V1 are of an appropriate spatial scale to mediate interactions within the SF of V1 neurons and to underlie contrast-dependent changes in SF size. Contrary to common beliefs, these connections cannot fully account for the dimensions of the surround field. The spatial scale of feedback circuits from extrastriate cortex to V1 is, instead, commensurate with the full spatial range of center-surround interactions. Thus these connections could represent an anatomical substrate for contextual modulation and global-to-local integration of visual signals. Feedback projections connect corresponding and equal-sized regions of the visual field in striate and extrastriate cortices and cover anisotropic parts of visual space, unlike V1 horizontal connections that are isotropic in the macaque. V1 isotropic connectivity demonstrates that anisotropic horizontal connections are not necessary to generate orientation selectivity. Anisotropic feedback connections may play a role in contour completion.
801 citations
TL;DR: A receptive field model based on the ratio of signals from Gaussian-shaped center and surround mechanisms is developed that offers a parsimonious explanation of a variety of phenomena involving changes in apparent receptive field size and accounts for these phenomena purely in terms of two receptive field mechanisms that do not themselves change in size.
Abstract: Information is integrated across the visual field to transform local features into a global percept. We now know that V1 neurons provide more spatial integration than originally thought due to the ...
799 citations
TL;DR: Using stimuli designed to tease apart differences in retinotopic organization and receptive field size, a double dissociation is established between two distinct MT+ subregions in 8 of the 10 hemispheres studied.
Abstract: We performed a series of functional magnetic resonance imaging experiments to divide the human MT+ complex into subregions that may be identified as homologs to a pair of macaque motion-responsive visual areas: the middle temporal area (MT) and the medial superior temporal area (MST). Using stimuli designed to tease apart differences in retinotopic organization and receptive field size, we established a double dissociation between two distinct MT+ subregions in 8 of the 10 hemispheres studied. The first subregion exhibited retinotopic organization but did not respond to peripheral ipsilateral stimulation, indicative of smaller receptive fields. Conversely, the second subregion within MT+ did not demonstrate retinotopic organization but did respond to peripheral stimuli in both the ipsilateral and contralateral visual hemifields, indicative of larger receptive fields. We tentatively identify these subregions as the human homologues of macaque MT and MST, respectively. Putative human MT and MST were typically located on the posterior/ventral and anterior/dorsal banks of a dorsal/posterior limb of the inferior temporal sulcus, similar to their relative positions in the macaque superior temporal sulcus.
623 citations
TL;DR: It is suggested that V1 intrinsic horizontal connections provide a more likely substrate for contour integration in primary visual cortex than V2 to V1 feedback.
469 citations
TL;DR: Specific mechanistic asymmetries in retinal On and OFF circuits and differences in visual performance on the basis of the activity of ON and OFF parasol cells are suggested.
Abstract: Functional asymmetries in the ON and OFF pathways of the primate visual system were examined using simultaneous multi-electrode recordings from dozens of retinal ganglion cells (RGCs) in vitro. Light responses of RGCs were characterized using white noise stimulation. Two distinct functional types of cells frequently encountered, one ON and one OFF, had non-opponent spectral sensitivity, relatively high response gain, transient light responses, and large receptive fields (RFs) that tiled the region of retina recorded, suggesting that they belonged to the same morphological cell class, most likely parasol. Three principal functional asymmetries were observed. (1) Receptive fields of ON cells were 20% larger in diameter than those of OFF cells, resulting in higher full-field sensitivity. (2) ON cells had faster response kinetics than OFF cells, with a 10-20% shorter time to peak, trough and zero crossing in the biphasic temporal impulse response. (3) ON cells had more nearly linear light responses and were capable of signaling decrements, whereas OFF cells had more strongly rectifying responses that provided little information about increments. These findings suggest specific mechanistic asymmetries in retinal ON and OFF circuits and differences in visual performance on the basis of the activity of ON and OFF parasol cells.
448 citations
TL;DR: It is concluded that NK1-positive spinal projection neurons, activated by primary afferent input, project to higher brain areas that control spinal excitability—and therefore pain sensitivity—primarily through descending pathways from the brainstem.
Abstract: The increase in pain sensitivity that follows injury is regulated by superficially located projection neurons in the dorsal horn of the spinal cord that express the neurokinin-1 (NK1) receptor. After selective ablation of these neurons in rats, we identified changes in receptive field size, mechanical and thermal coding and central sensitization of deeper dorsal horn neurons that are important for both pain sensations and reflexes. We were able to reproduce these changes by pharmacological block of descending serotonergic facilitatory pathways. Using Fos histochemistry, we found changes in the activation of serotonergic neurons in the brainstem as well as evidence for a loss of descending control of spinal excitability. We conclude that NK1-positive spinal projection neurons, activated by primary afferent input, project to higher brain areas that control spinal excitability--and therefore pain sensitivity--primarily through descending pathways from the brainstem.
427 citations
TL;DR: The surround has complex effects on responses from the classical receptive field and it is suggested that the underlying mechanism of this complexity may involve interactions between relatively simple center and surround mechanisms.
Abstract: The responsiveness of neurons in V1 is modulated by stimuli placed outside their classical receptive fields. This nonclassical surround provides input from a larger portion of the visual scene than...
418 citations
TL;DR: Results indicate that extrastriate visual areas are involved in the process of remapping, and show that remapping was very rare in striate cortex.
Abstract: Neurons in the lateral intraparietal area, frontal eye field, and superior colliculus exhibit a pattern of activity known as remapping. When a salient visual stimulus is presented shortly before a saccade, the representation of that stimulus is updated, or remapped, at the time of the eye movement. This updating is presumably based on a corollary discharge of the eye movement command. To investigate whether visual areas also exhibit remapping, we recorded from single neurons in extrastriate and striate cortex while monkeys performed a saccade task. Around the time of the saccade, a visual stimulus was flashed either at the location occupied by the neuron's receptive field (RF) before the saccade (old RF) or at the location occupied by it after the saccade (new RF). More than half (52%) of V3A neurons responded to a stimulus flashed in the new RF even though the stimulus had already disappeared before the saccade. These neurons responded to a trace of the flashed stimulus brought into the RF by the saccade. In 16% of V3A neurons, remapped activity began even before saccade onset. Remapping also was observed at earlier stages of the visual hierarchy, including in areas V3 and V2. At these earlier stages, the proportion of neurons that exhibited remapping decreased, and the latency of remapped activity increased relative to saccade onset. Remapping was very rare in striate cortex. These results indicate that extrastriate visual areas are involved in the process of remapping.
414 citations
TL;DR: Measurements of the spatial structure of simple-cell receptive fields in macaque primary visual cortex show a tendency for neurons that are well tuned in orientation and spatial frequency to have odd-symmetric receptive fields, and a population analysis reveals that the distribution of spatial profiles inPrimary visual cortex lies approximately on a one-parameter family of filter shapes.
Abstract: I present measurements of the spatial structure of simple-cell receptive fields in macaque primary visual cortex (area V1). Similar to previous findings in cat area 17, the spatial profile of simple-cell receptive fields in the macaque is well described by two-dimensional Gabor functions. A population analysis reveals that the distribution of spatial profiles in primary visual cortex lies approximately on a one-parameter family of filter shapes. Surprisingly, the receptive fields cluster into even- and odd-symmetry classes with a tendency for neurons that are well tuned in orientation and spatial frequency to have odd-symmetric receptive fields. The filter shapes predicted by two recent theories of simple-cell receptive field function, independent component analysis and sparse coding, are compared with the data. Both theories predict receptive fields with a larger number of subfields than observed in the experimental data. In addition, these theories do not generate receptive fields that are broadly tuned in orientation and low-pass in spatial frequency, which are commonly seen in monkey V1. The implications of these results for our understanding of image coding and representation in primary visual cortex are discussed.
397 citations
TL;DR: In the spinal dorsal horn, multireceptive neurones are found to be projection neurones and/or interneurones for polysynaptic reflexes as mentioned in this paper, which can be inhibited from most of the remaining parts of the body via supraspinal mechanisms.
375 citations
TL;DR: It is found that there is no correlation between spectral and temporal integration properties, suggesting that the excitatory-inhibitory interactions underlying preference in each domain are largely independent.
Abstract: Receptive fields have been characterized independently in the lemniscal auditory thalamus and cortex, usually with spectrotemporally simple sounds tailored to a specific task. No studies have emplo...
TL;DR: It is concluded that PSPs in ensembles of barrel cells represent dynamically the deflection of a single whisker with high temporal and spatial acuity, initially by the excitation in a single PW‐barrel followed by multi-barrel excitation.
Abstract: The elaborate morphology of cortical neurons has been established for a long time (Ramon y Cajal, 1893), yet the functional significance of the differences in the architecture of the dendritic and axonal arbors of cells located in the same or different cortical layers is still unclear. Layer 4 of rodent somatosensory cortex is divided cytoarchitectonically into barrels with a high density of neurons, and septa between barrels with a lower density (Woolsey & Van der Loos, 1970). Barrel cells are targeted by thalamic inputs from the ventral posterior medial nucleus (VPM; for review see Diamond, 1995) while septum cells are innervated by thalamic afferents projecting from the posterior medial nucleus (PoM; for review see Kim & Ebner, 1999). A functional equivalent of the cytoarchitectonically defined barrels are the barrel-columns, ensembles of cells in the different cortical layers which share functional properties such as a response preference for the deflection of a particular whisker. The receptive fields (RFs) of barrel-column cells are characterised by a dominant input from a principal whisker (PW) and weaker inputs from surround whiskers (SuW). In L4 the barrel-columns correspond in their dimensions roughly to barrels (Welker, 1976). Barrel borders can be visualised simultaneously with the dendritic morphology of individual cells (Ito, 1992), and both the laminar location of a cell's soma and the spread of dendrites and axon collaterals can be determined relative to the barrel borders. Thus possible anatomical determinants of RF structure, such as the geometry of the dendritic and axonal arbor can be delineated.
Spiny stellate cells are confined to the borders of barrels and their dendritic arbor is asymmetric (Woolsey et al. 1975; Simons & Woolsey 1984; Feldmeyer et al. 1999; Lubke et al. 2000). They relay thalamic output to other cortical layers via axon collaterals projecting to L2/3 and to L5 or L6. Although most anatomical studies on L4 neurons have focused on spiny stellate cells, pyramidal neurons have also been described in somatosensory (Lorente de No, 1922; Elston et al. 1997; Lubke et al. 2000) and in visual cortex (Martin & Whitteridge, 1984). In the somatosensory cortex neurons in layer 4 are selective in their responses to the direction of whisker deflection and they respond with short latency. Their RF structure is somewhat controversial, however. Intracellular recordings with microelectrodes (Carvel & Simons, 1988) and more recently, whole-cell voltage recordings have demonstrated afferent inputs from several whiskers and large subthreshold RFs (Moore & Nelson, 1998; Zhu & Connors, 1999). Most (Simons, 1995) but not all (Armstrong-James, 1995) extracellular unit-recording studies report small, often single-whisker RFs. In addition multielectrode unit recordings indicate that RF properties are time dependent (Petersen & Diamond, 2000).
We report in vivo whole-cell voltage recordings combined with morphological reconstruction of the recorded neurons and determination of their columnar position. The aim was to establish firstly the dependency of RF structure on the geometry of dendritic and axonal arborisation of the different classes of neurons to identify possible constraints of RF structure given by cell morphology. Secondly we wanted to determine possible relationships between a cell's location and morphology and the time dependent structure of sub- and suprathreshold RFs. Such relations are essential to elucidate how different tactile object cues are represented at the input (PSPs) and the output stage (APs) of specific ensembles of cells in the cortical input layer.
TL;DR: The smaller, more directionally selective RFs of excitatory neurons may be a consequence of their weaker net thalamic drive, their more nonlinear firing characteristics and pervasive feedforward inhibition provided by strongly driven, broadly tuned inhibitory neurons.
Abstract: Excitatory and inhibitory cortical layer IV neurons have distinctive response properties. Thalamocortical connectivity that may underlie differences was examined using cross-correlation analyses of pairs of thalamic and cortical neurons in the rat whisker/barrel system. Cortical layer IV cells discharging fast spikes, presumed inhibitory neurons, were distinguished from regular-spike units, presumed excitatory neurons, by the extracellular waveform shape. Regular-spike neurons fired less robustly and had smaller receptive fields (RFs) and greater directional tuning than fast-spike cells. Presumed excitatory neurons were less likely to receive thalamocortical connections, and their connections were, on average, weaker. RF properties of thalamic inputs to both cell types were equivalent, except that the most highly responsive thalamic cells contacted only fast-spike neurons. In contrast, the size and directional tuning of cortical RFs were related to the number of detectable thalamocortical inputs. Connected thalamocortical pairs were likely to have matching RF characteristics. The smaller, more directionally selective RFs of excitatory neurons may be a consequence of their weaker net thalamic drive, their more nonlinear firing characteristics and pervasive feedforward inhibition provided by strongly driven, broadly tuned inhibitory neurons.
TL;DR: The findings suggest that nearby inhibitory neurons are more tightly synchronized than excitatory ones and account for much of the correlated discharges commonly observed in undifferentiated cortical networks.
Abstract: Neurophysiological recordings have revealed that the discharges of nearby cortical cells are positively correlated in time scales that range from millisecond synchronization of action potentials to much slower firing rate co-variations, evident in rates averaged over hundreds of milliseconds The presence of correlated firing can offer insights into the patterns of connectivity between neurons; however, few models of population coding have taken account of the neuronal diversity present in cerebral cortex, notably a distinction between inhibitory and excitatory cells We addressed this question in the monkey dorsolateral prefrontal cortex by recording neuronal activity from multiple micro-electrodes, typically spaced 02-03 mm apart Putative excitatory and inhibitory neurons were distinguished based on their action potential waveform and baseline discharge rate We tested each pair of simultaneously recorded neurons for presence of significant cross-correlation peaks and measured the correlation of their averaged firing rates in successive trials When observed, cross-correlation peaks were centered at time 0, indicating synchronous firing consistent with two neurons receiving common input Discharges in pairs of putative inhibitory interneurons were found to be significantly more strongly correlated than in pairs of putative excitatory cells The degree of correlated firing was also higher for neurons with similar spatial receptive fields and neurons active in the same epochs of the behavioral task These factors were important in predicting the strength of both short time scale (<5 ms) correlations and of trial-to-trial discharge rate covariations Correlated firing was only marginally accounted for by motor and behavioral variations between trials Our findings suggest that nearby inhibitory neurons are more tightly synchronized than excitatory ones and account for much of the correlated discharges commonly observed in undifferentiated cortical networks In contrast, the discharge of pyramidal neurons, the sole projection cells of the cerebral cortex, appears largely independent, suggesting that correlated firing may be a property confined within local circuits and only to a lesser degree propagated to distant cortical areas and modules
TL;DR: Investigation of how the nonclassical receptive field affects information transmission by V1 neurons during simulated natural vision in awake, behaving macaques demonstrates that the nCRF increases the sparseness of the stimulus representation in V1, suggesting that thenCRF tunes V 1 neurons to match the highly informative components of the natural world.
Abstract: We have investigated how the nonclassical receptive field (nCRF) affects information transmission by V1 neurons during simulated natural vision in awake, behaving macaques. Stimuli were centered over the classical receptive field (CRF) and stimulus size was varied from one to four times the diameter of the CRF. Stimulus movies reproduced the spatial and temporal stimulus dynamics of natural vision while maintaining constant CRF stimulation across all sizes. In individual neurons, stimulation of the nCRF significantly increases the information rate, the information per spike, and the efficiency of information transmission. Furthermore, the population averages of these quantities also increase significantly with nCRF stimulation. These data demonstrate that the nCRF increases the sparseness of the stimulus representation in V1, suggesting that the nCRF tunes V1 neurons to match the highly informative components of the natural world.
TL;DR: It is suggested that normal PF receptive fields are established by CF-specific plasticity, and that the receptive field changes were due to bidirectional PF synaptic plasticity in Purkinje cells and interneurons.
TL;DR: It is found that SF and orientation tuning are largely separable over time in single neurons, and the observed relationship between stimulus SF and latency represents a dynamic shift in SF tuning, and suggests that single V1 neurons might receive convergent input from the magno- and parvocellular processing streams.
Abstract: Spatial frequency (SF) and orientation tuning are intrinsic properties of neurons in primary visual cortex (area V1). To investigate the neural mechanisms mediating selectivity in the awake animal, we measured the temporal dynamics of SF and orientation tuning. We adapted a high-speed reverse-correlation method previously used to characterize orientation tuning dynamics in anesthetized animals to estimate efficiently the complete spatiotemporal receptive fields in area V1 of behaving macaques. We found that SF and orientation tuning are largely separable over time in single neurons. However, spatiotemporal receptive fields also contain a small nonseparable component that reflects a significant difference in response latency for low and high SF stimuli. The observed relationship between stimulus SF and latency represents a dynamic shift in SF tuning, and suggests that single V1 neurons might receive convergent input from the magno- and parvocellular processing streams. Although previous studies with anesthetized animals suggested that orientation tuning could change dramatically over time, we find no substantial evidence of dynamic changes in orientation tuning.
TL;DR: In this paper, the authors found that exposure to pulsed white noise at moderate intensity during P9-P28 resulted in a disrupted tonotopicity and degraded frequency-response selectivity for neurons in the primary auditory cortex.
Abstract: In the primary auditory cortex (AI), the development of tone frequency selectivity and tonotopic organization is influenced by patterns of neural activity. Introduction of synchronous inputs into the auditory pathway achieved by exposing rat pups to pulsed white noise at a moderate intensity during P9–P28 resulted in a disrupted tonotopicity and degraded frequency-response selectivity for neurons in the adult AI. The latter was manifested by broader-than-normal tuning curves, multipeaks, and discontinuous, tone-evoked responses within AI-receptive fields. These effects correlated with the severe impairment of normal, developmental sharpening, and refinement of receptive fields and tonotopicity. In addition, paradoxically weaker than normal temporal correlations between the discharges of nearby AI neurons were recorded in exposed rats. In contrast, noise exposure of rats older than P30 did not cause significant change of auditory cortical maps. Thus, patterned auditory inputs appear to play a crucial role in shaping neuronal processing/decoding circuits in the primary auditory cortex during a critical period.
TL;DR: Analysis of neural activity generated by microsaccades in the lateral geniculate nucleus (LGN), and in the area V-1 of the awake monkey, for various functionally relevant stimulus parameters suggested burst size as a neural code for stimuli optimality (and not solely stimuli visibility).
Abstract: When images are stabilized on the retina, visual perception fades. During voluntary visual fixation, however, constantly occurring small eye movements, including microsaccades, prevent this fading. We previously showed that microsaccades generated bursty firing in the primary visual cortex (area V-1) in the presence of stationary stimuli. Here we examine the neural activity generated by microsaccades in the lateral geniculate nucleus (LGN), and in the area V-1 of the awake monkey, for various functionally relevant stimulus parameters. During visual fixation, microsaccades drove LGN neurons by moving their receptive fields across a stationary stimulus, offering a likely explanation of how microsaccades block fading during normal fixation. Bursts of spikes in the LGN and area V-1 were associated more closely than lone spikes with preceding microsaccades, suggesting that bursts are more reliable than are lone spikes as neural signals for visibility. In area V-1, microsaccade-generated activity, and the number of spikes per burst, was maximal when the bar stimulus centered over a receptive field matched the cell's optimal orientation. This suggested burst size as a neural code for stimuli optimality (and not solely stimuli visibility). As expected, burst size did not vary with stimulus orientation in the LGN. To address the effectiveness of microsaccades in generating neural activity, we compared activity correlated with microsaccades to activity correlated with flashing bars. Onset responses to flashes were about 7 times larger than the responses to the same stimulus moved across the cells' receptive fields by microsaccades, perhaps because of the relative abruptness of flashes.
TL;DR: This work uses acoustic signals with a structurally rich time-varying spectrum to study linear and nonlinear spectrotemporal interactions in the central nucleus of the inferior colliculus (ICC), finding that ∼60% of ICC neurons meet this basic requirement for a linear integrating neuron.
Abstract: The auditory system of humans and animals must process information from sounds that dynamically vary along multiple stimulus dimensions, including time, frequency, and intensity. Therefore, to understand neuronal mechanisms underlying acoustic processing in the central auditory pathway, it is essential to characterize how spectral and temporal acoustic dimensions are jointly processed by the brain. We use acoustic signals with a structurally rich time-varying spectrum to study linear and nonlinear spectrotemporal interactions in the central nucleus of the inferior colliculus (ICC). Our stimuli, the dynamic moving ripple (DMR) and ripple noise (RN), allow us to systematically characterize response attributes with the spectrotemporal receptive field (STRF) methods to a rich and dynamic stimulus ensemble. Theoretically, we expect that STRFs derived with DMR and RN would be identical for a linear integrating neuron, and we find that ∼60% of ICC neurons meet this basic requirement. We find that the remaining neurons are distinctly nonlinear; these could either respond selectively to DMR or produce no STRFs despite selective activation to spectrotemporal acoustic attributes. Our findings delineate rules for spectrotemporal integration in the ICC that cannot be accounted for by conventional linear–energy integration models.
TL;DR: It is shown that a simple rectification model can predict the observed bimodal distribution of F(1)/F(0) in primary visual cortex when the distributions of the intracellular response modulation and mean are unimodal.
TL;DR: The results suggest that although all three cortical eye fields reflect attentional and intentional aspects of sensorimotor processing, SEF plays an earlier and perhaps more cognitive role in internally guided decision-making processes for saccades.
Abstract: To examine the role of three cortical eye fields during internally guided decision-making processes, we recorded neuronal activities in the frontal eye field (FEF), supplementary eye field (SEF), and lateral intraparietal cortex (LIP) using a free-choice delayed saccade task with two synchronized targets. Although the monkeys must perform the task in a time-locked manner, they were free to choose either the receptive field (RF) target or the nonreceptive field (nRF) target to receive reward. In all three areas we found neurons with stronger activation during trials when the monkey was going to make a saccade to the RF target (RF trials) than to the nRF target (nRF trials). Modulation occurred not only during target presentation (visual bias) but also before target presentation (anticipatory bias). The visual bias was evident as an attenuated visual response to the RF stimulus in nRF trials. The anticipatory bias, however, was seen as an enhancement of pretarget activity in the RF trials. We analyzed the activity during the 500 msec before target presentation and found that 22.5% of FEF and 31.3% of LIP neurons and 49.1% of SEF neurons showed higher activity during the RF trials. To more accurately determine when each neuron started to show preferential activity, we used a new inverse interspike interval analysis procedure. Our results suggest that although all three cortical eye fields reflect attentional and intentional aspects of sensorimotor processing, SEF plays an earlier and perhaps more cognitive role in internally guided decision-making processes for saccades.
TL;DR: By applying a population code, termed ‘isofrequency encoding’, it is demonstrated the capability of the recorded neuronal ensemble to retrieve the focus location from its population discharge and suggest an involvement of area VIP in the analysis and the encoding of heading.
Abstract: We recorded neuronal responses to optic flow stimuli in the ventral intraparietal area (VIP) of two awake macaque monkeys. According to previous studies on optic flow responses in monkey extrastriate cortex we used different stimulus classes: frontoparallel motion, radial stimuli (expansion and contraction) and rotational stimuli (clockwise and counter-clockwise). Seventy-five percent of the cells showed statistically significant responses to one or more of these optic flow stimuli. Shifting the location of the singularity of the optic flow stimuli within the visual field led to a response modulation in almost all cases. For the majority of neurons, this modulatory influence could be approximated in a statistically significant manner by a two-dimensional linear regression. Gradient directions, derived from the regression parameters and indicating the direction of the steepest increase in the responses, were uniformly distributed. At the population level, an unbiased average response for the stimuli with different focus locations was observed. By applying a population code, termed 'isofrequency encoding', we demonstrate the capability of the recorded neuronal ensemble to retrieve the focus location from its population discharge. Responses to expansion and contraction stimuli cannot be predicted based on quantitative data on a neuron's frontoparallel preferred stimulus direction and the location and size of its receptive field. These results, taken together with data on polymodal motion responses in this area, suggest an involvement of area VIP in the analysis and the encoding of heading.
01 Jan 2002
TL;DR: These data provide the first detailed description of auditory receptive fields in the mouse and suggest that although neurons in areas AI and AAF share many response characteristics, area AAF may be specialized for faster temporal processing.
Abstract: The mouse is a promising model system for auditory cortex research because of the powerful genetic tools available for manipulating its neural circuitry. Previous studies have identified two tonotopic auditory areas in the mouse-primary auditory cortex (AI) and anterior auditory field (AAF)-but auditory receptive fields in these areas have not yet been described. To establish a foundation for investigating auditory cortical circuitry and plasticity in the mouse, we characterized receptive-field structure in AI and AAF of anesthetized mice using spectrally complex and temporally dynamic stimuli as well as simple tonal stimuli. Spectrotemporal receptive fields (STRFs) were derived from extracellularly recorded responses to complex stimuli, and frequency-intensity tuning curves were constructed from responses to simple tonal stimuli. Both analyses revealed temporal differences between AI and AAF responses: peak latencies and receptive-field durations for STRFs and first-spike latencies for responses to tone bursts were significantly longer in AI than in AAF. Spectral properties of AI and AAF receptive fields were more similar, although STRF bandwidths were slightly broader in AI than in AAF. Finally, in both AI and AAF, a substantial minority of STRFs were spectrotemporally inseparable. The spectrotemporal interaction typically appeared in the form of clearly disjoint excitatory and inhibitory subfields or an obvious spectrotemporal slant in the STRF. These data provide the first detailed description of auditory receptive fields in the mouse and suggest that although neurons in areas AI and AAF share many response characteristics, area AAF may be specialized for faster temporal processing.
TL;DR: The effect of ECRF stimulation on visual responsive cells in the lateral geniculate nucleus (LGN) of a diurnal New World primate, the marmoset, was quantified in this article.
Abstract: Descriptions of receptive fields at subcortical levels of the visual system have mostly considered only the classical receptive field (CRF). A suppressive extraclassical receptive field (ECRF) has been demonstrated in relay cells within the primate lateral geniculate nucleus (LGN), but the quantitative properties and specific influence of the ECRF on the distinct magnocellular (MC), koniocellular (KC), and parvocellular (PC) pathways are not known. Here we quantified the effect of ECRF stimulation on visually responsive cells in the LGN of a diurnal New World primate, the marmoset. We show that for all cells, visually evoked responses are reduced by stimulation of the ECRF. The magnitude of the suppression is greatest for MC cells and smallest for PC cells. The effect of ECRF stimulation on KC cells is variable but always suppressive. We refer to these effects as extraclassical inhibition (ECI). The contrast-response relationship of the ECI parallels that of CRF-induced excitation for each cell class: for MC cells, ECI contrast threshold is close to 10% and the ECI saturates at 50% contrast, but the contrast dependence of ECI on PC cells is more linear. The ECI also contributes to contrast-dependent changes in spatial summation: on average for all LGN cells the radius of the excitatory spatial summation field (measured from aperture-tuning curves) at low contrast is 1.31 times that at high contrast. No consistent effects of orientation on ECI were seen. The data suggest that the suppressive component of the ECRF seen in cortical neurons could primarily be inherited from subcortical input streams.
TL;DR: The results demonstrate that during natural viewing, thalamic response properties can vary dramatically, even over the course of a single fixation.
TL;DR: Differences in RGC intrinsic properties are striking and robust and may affect how each type responds to synaptic input and may help tune each cell type appropriately for their individual roles in visual processing.
Abstract: Retinal ganglion cells (RGCs) are the output neurons of the retina, sending their signals via the optic nerve to many different targets in the thalamus and brainstem. These cells are divisible into more than a dozen types, differing in receptive field properties and morphology. Light responses of individual RGCs are in large part determined by the exact nature of the retinal synaptic network in which they participate. Synaptic inputs, however, are greatly influenced by the intrinsic membrane properties of each cell. While it has been demonstrated clearly that RGCs vary in their intrinsic properties, it remains unclear whether this variation is systematically related to RGC type. To learn whether membrane properties contribute to the functional differentiation of RGC types, we made whole-cell current clamp recordings of RGC responses to injected current of identified cat RGCs. The data collected demonstrated that RGC types clearly differed from one another in their intrinsic properties. One of the most striking differences we observed was that individual cell types had membrane time constants that varied widely from approximately 4 ms (alpha cells) to more than 80 ms (zeta cells). Perhaps not surprisingly, we also observed that RGCs varied greatly in their maximum spike frequencies (kappa cells 48 Hz-alpha cells 262 Hz) and sustained spike frequencies (kappa cells 23 Hz-alpha cells 67 Hz). Interestingly, however, most RGC types exhibited similar amounts of spike frequency adaptation. Finally, RGC types also differed in their responses to injection of hyperpolarizing current. Most cell types exhibited anomalous rectification in response to sufficiently strong hyperpolarization, although alpha and beta RGCs showed only minimal, if any, rectification under similar conditions. The differences we observed in RGC intrinsic properties were striking and robust. Such differences are certain to affect how each type responds to synaptic input and may help tune each cell type appropriately for their individual roles in visual processing.
TL;DR: It is concluded that three pathways can provide the V1 neuron with access to information from the visual field and affect its response, and feedback from extrastriate cortex can provide a large and stimulus specific surround modulatory field.
Abstract: From the analyses of our own and others' anatomical and physiological data for the macaque visual system, we arrive at a conclusion that three pathways can provide the V1 neuron with access to information from the visual field and affect its response. First, direct thalamic input can determine the size of the initial activating RF at high contrast. Second, lateral connections can enlarge the RF at low contrast by pooling information from larger regions of cortex that are otherwise ineffective when high contrast thalamic input is driving the cortical neuron. Thirdly, feedback from extrastriate cortex (possibly together with overlap or interdigitation of coactive lateral connectional fields within V1) can provide a large and stimulus specific surround modulatory field. The stimulus specificity of the interactions between the center and surround fields, may be due to the orderly, matching structure and different scales of intra-areal and feedback projection excitatory pathways. The observed activity changes of single recorded excitatory neurons could be a result of the relative weight of excitation on the excitatory neurons themselves and on local inhibitory interneurons that synapse on them. Inhibitory basket neurons, driven by the local excitatory neurons, could govern local interactions between cortical patches of different tuning properties, resulting in more distant changes in excitatory input in the laterally connected intra-areal neuronal pools.
TL;DR: In visual cortex, auditory cortex and somatosensory cortex loss of input from a region of the peripheral receptor epithelium induces rapid expression of ectopic, or expanded, receptive fields of affected neurons and reorganization of topographic maps to fill in the representation of the denervated area, which rules out many possible explanations which involve synaptic plasticity.
TL;DR: In this paper, the authors studied neurons in the central visual field representation of the lateral geniculate nucleus (LGN) in macaque monkeys by mapping their receptive fields in space and time.
Abstract: We studied neurons in the central visual field representation of the lateral geniculate nucleus (LGN) in macaque monkeys by mapping their receptive fields in space and time. The mapping was performed by reverse correlation of a spike train of a neuron with pseudorandom, binary level stimuli (m-sequence grids). Black and white m-sequence grids were used to map the receptive field for luminance. The locations of receptive field center and surround were determined from this luminance map. To map the contribution of each cone class to the receptive field, we designed red-green or blue-yellow m-sequence grids to isolate the influence of that cone (long, middle, or short wavelength-sensitive: L, M, or S). Magnocellular neurons generally received synergistic input from L and M cones in both the center and the surround. A minority had cone-antagonistic (M-L) input to the surround. Red-green opponent parvocellular neurons received opponent cone input (L+M- or M+L-) that overlapped in space, as sampled by our stimulus grid, but that had somewhat different extents. For example, an L+ center parvocellular neuron would be L+/M- in both center and surround, but the L+ signal would be stronger in the center and the M- signal stronger in the surround. Accordingly, the luminance receptive field would be spatially antagonistic: on-center/off-surround. The space-time maps also characterized LGN dynamics. For example, magnocellular responses were transient, red-green parvocellular responses were more sustained, and blue-on responses were the most sustained for both luminance and cone-isolating stimuli. For all cell types the surround response peaked 8-10 msec later than the center response.