Showing papers on "Receptive field published in 1978"

Spatial summation in the receptive fields of simple cells in the cat's striate cortex.

Abstract: 1. We have examined the responses of simple cells in the cat's atriate cortex to visual patterns that were designed to reveal the extent to which these cells may be considered to sum light-evoked influences linearly across their receptive fields. We used one-dimensional luminance-modulated bars and grating as stimuli; their orientation was always the same as the preferred orientation of the neurone under study. The stimuli were presented on an oscilloscope screen by a digital computer, which also accumulated neuronal responses and controlled a randomized sequence of stimulus presentations. 2. The majority of simple cells respond to sinusoidal gratings that are moving or whose contrast is modulated in time in a manner consistent with the hypothesis that they have linear spatial summation. Their responses to moving gratings of all spatial frequencies are modulated in synchrony with the passage of the gratings' bars across their receptive fields, and they do not produce unmodulated responses even at the highest spatial frequencies. Many of these cells respond to temporally modulated stationary gratings simply by changing their response amplitude sinusoidally as the spatial phase of the grating the grating is varied. Nonetheless, their behavior appears to indicate linear spatial summation, since we show in an Appendix that the absence of a 'null' phase in a visual neurone need not indicate non-linear spatial summation, and further that a linear neurone lacking a 'null' phase should give responses of the form that we have observed in this type of simple cell. 3. A minority of simple cells appears to have significant non-linearities of spatial summation. These neurones respond to moving gratings of high spatial frequency with a partially or totally unmodulated elevation of firing rate. They have no 'null' phases when tested with stationary gratings, and reveal their non-linearity by giving responses to gratings of some spatial phases that are composed partly or wholly of even harmonics of the stimulus frequency ('on-off' responses). 4. We compared simple receptive fields with their sensitivity to sinusoidal gratings of different spatial frequencies. Qualitatively, the most sensitive subregions of simple cells' receptive fields are roughly the same width as the individual bars of the gratings to which they are most sensitive. Quantitatively, their receptive field profiles measured with thin stationary lines, agree well with predicted profiles derived by Fourier synthesis of their spatial frequency tuning curves.

Intracortical connectivity of architectonic fields in the somatic sensory, motor and parietal cortex of monkeys

Abstract: Anterograde and retrograde transport methods were used to study the corticocortical connectivity of areas 3a, 3b, 1, 2, 5, 4 and 6 of the monkey cerebral cortex. Fields were identified by cytoarchitectonic features and by thalamic connectivity in the same brains. Area 3a was identified by first recording a short latency group I afferent evoked potential. Attempts were made to analyze the data in terms of: (1) routes whereby somatic sensory input might influence the performance of motor cortex neurons; (2) possible multiple representations of the body surface in the component fields of the first somatic sensory area (SI). Apart from vertical interlaminar connections, two types of intracortical connectivity are recognized. The first, regarded as "non-specific," consists of axons spreading out in layers I, III and V-VI from all sides of an injection of isotope; these cross architectonic borders indiscrimininately. They are not unique to the regions studied. The second is formed by axons entering the white matter and re-entering other fields. In these, they terminate in layers I-IV in one or more mediolaterally oriented strips of fairly constant width (0.5--1 mm) and separated by gaps of comparable size. Though there is a broadly systematic topography in these projections, the strips are probably best regarded as representing some feature other than receptive field position. Separate representations are nevertheless implied in area 3b, in areas 1 and 2 (together), in areas 3a and 4 (together) and in area 5; with, in each case, the representations of the digits pointed at the central sulcus. Area 3b is not connected with areas 3a or 4, but projects to a combined areas 1 and 2. Area 1 is reciprocally connected with area 3a and area 2 reciprocally with area 4. The connectivity of area 3a, as conventionally identified, is such that it is probably best regarded not as an entity, but as a part of area 4. Areas identified by others as area 3a should probably be regraded as parts of area 3b. Parts of area 5 that should be more properly considered as area 2, and other parts that receive thalamic input not from the ventrobasal complex but from the lateral nuclear complex and anterior pulvinar, are also interconnected with area 4. More posterior parts of area 5 are connected with laterally placed parts of area 6. A more medial part of area 6, the supplementary motor area, occupies a pivotal position in the sensory-motor cortex, for it receives fibers from areas 3a, 4, 1, 2 and 5 (all parts), and projects back to areas 3a, 4 and 5.

The retinotopic organization of area 17 (striate cortex) in the cat.

Abstract: The location and retinotopic organization of visual areas in the cat cortex were determined by systematically mapping visual cortex in over 100 cats. The positions of the receptive fields of single neurons or small clusters of neurons were related to the locations of the corresponding recording sites in the cortex to determine the representations of the visual field in these cortical areas. In this report, the first of a series, we describe the organization of area 17. A single representation of the cat's entire visual field corresponds closely to the cytoarchitectonically defined area 17. This area has the largest cortical surface area (380 mm2) and the highest cortical magnification factor (3.6 mm2/degree2 at area centralis) of all the cortical areas we have studied. There was perfect agreement between the borders of area 17 determined electrophysiologically and cytoarchitecturally. This area contains a first order transformation of the visual hemifield in which every adjacent point in the visual field is represented as an adjacent point in the cortex. Some variability exists among cats in the extent and retinotopic representation of the visual field in area 17.

Spatial and temporal contrast sensitivity of neurones in areas 17 and 18 of the cat's visual cortex.

Abstract: 1. We have examined the spatial and temporal tuning properties of 238 cortical neurones, recorded using conventional techniques from acutely prepared anaesthetized cats. We determined spatial and temporal frequency tuning curves using sinusoidal grating stimuli presented to each neurone's receptive field by a digital computer on a cathode ray tube. 2. We measured tuning curves either by determining response amplitude as a function of spatial or temporal frequency, or by measuring contrast sensitivity (the inverse of the contrast of the grating that just elicited a detectable response). The two measures give very similar tuning curves in all cases. 3. We recorded from 184 neurones in area 17; of these 156 had receptive fields within 5 degrees of the area centralis. The range of preferred spatial frequency for these neurones was 0.3--3 c/deg, and their spatial frequency tuning band widths varied from 0.7 to 3.2 octaves at half-amplitude. The most common band width was roughly 1.3 octaves. Simple and complex cells in area 17 did not differ in their distributions of preferred spatial frequency, although complex cells were, on average, slightly less selective for spatial frequency than simple cells. 4. We recorded from fifty-four neurones from area 18, and performed several experiments in which we recorded from corresponding portions of both area 17 and area 18 in the same electrode penetration. Neurones in area 18 preferred spatial frequencies that were, on average, one third as high as those preferred by area 17 neurones at the same retinal eccentricity. Thus the range of preferred spatial frequency in area eighteen cells having receptive fields within 5 deg of the area centralis was between less than 0.1 and 0.5 c/deg. The distributions of optimum spatial frequency in the two areas were practically non-overlapping at eccentricities as high as 15 deg, the greatest eccentricity we examined. Neurones in area 18 were about as selective for spatial frequency as were neurones in area 17. 5. We determined temporal frequency tuning characteristics for some neurones from each area, using gratings that moved steadily across the screen. Neurones from area 17 all responded well to low temporal frequencies, and less well to higher frequencies (in excess of, usually, 2 or 4 Hz). In contrast, neurones recorded from area 18 sometimes had similar tuning properties, but more commonly showed a pronounced reduction in response as the temporal frequency was moved either above or below some optimum value (usually 2--8 Hz). 6. We conclude from these results that areas 17 and 18 act in parallel to process different aspects of the visual information relayed from the retina via the lateral geniculate complex. Some or all of the differences between the areas may be attributable to the predominance of Y cell input to area 18 and the predominance of X cell input to area 17...

Receptive field organization of complex cells in the cat's striate cortex.

Abstract: 1. All complex cells in the cat's striate cortex exhibit gross non-linearities of spatial summation when tested with sinusoidal grating stimuli. Their responses to moving gratings of all but the lowest spatial frequencies are usually dominated by a component that is not modulated by the passage of the bars of the grating across the receptive field. They give responses to temporally modulated stationary gratings that consist mostly of even harmonics of the stimulus frequency and that vary little in amplitude or wave form as the spatial phase of the grating is varied. 2. We compared complex cells' receptive fields with their sensitivity to sinusoidal gratings of different spatial frequencies. Qualitatively, the receptive fields are usually two to five times wider than the bars of the gratings that stimulate them most effectively. Quantitatively, the receptive field profiles of complex cells are invariably broader than those predicted by Fourier synthesis of their spatial frequency tuning curves, and in particular lack predicted spatially antagonistic regions. 3. We further examined the receptive field organization of these cells, using pairs of stationary lines flashed synchronously on their receptive fields. If both lines are of the same polarity (bright or dark), complex cells respond to the paired stimulus much less well than they do to either of its component bars, unless the bars are separated by less than about one quarter of the width of the receptive field. If the lines are of opposite polarity, one bright and one dark, the opposite situation obtains: closely spaced bars elicit small responses, while paired bars of larger separation are much more effective. In either case, the results are independent in general character of the absolute positions of the stimuli within the receptive field; rather, they depend in a manner characteristic of each cell on the relative positions of the two bars. 4. The two-line interaction profile that plots the change in a complex cell's response to one bar as a function of the position of a second added bar corresponds closely to the receptive field profile predicted from Fourier synthesis of the cell's spatial frequency tuning curve. These profiles may thus reveal the spatial characteristics of subunits within complex cell-receptive fields. We examined the nature of the interaction between these subunits by performing several two-line interaction experiments in which the onset of the second bar was delayed some time after the onset of the first. The results suggest that neighbouring subunits interact in a facilitatory fashion: for an interval after the presentation of one bar, responses to neighbouring bars are enhanced. 5. The subunits of a complex receptive field may, by their spatial properties, determine the spatial selectivities of complex cells, while the nature of the interaction among the subunits may determine these cells' sensitivity and selectivity for moving visual stimuli...

Uniformity and diversity of structure and function in rhesus monkey prestriate visual cortex.

Abstract: 1. Recordings were made from single neurones, or small clusters of cells, in five prestriate visual areas of rhesus monkey cortex. The cells were studied for their binocularity, as well as for their orientational, motion and colour preferences. In all, 1500 cells were studied, 250 cells for each of the areas V2, V3, V3A and the motion area of the posterior bank of the superior temporal sulcus, and 500 cells for V4. All the cells referred to in this study can be placed in one prestriate area or another unambiguously. 2. The great majority of cells in all areas were binocularly driven, without monocular preferences. Within each area, there were cells that either preferred binocular stimulation markedly, or were responsive to binocular stimulation only. The ocular interaction histograms for all areas are remarkably similar when tested at a fixed disparity. 3. Over 70% of the cells in areas V2, V3 and V3A were selective for orientation. The receptive fields of cells were larger in V3 and V3A than in V2. By contrast, less than 50% of the cells in V4 and the motion area of the superior temporal sulcus were orientation selective. 4. Directionally selective cells were found in all areas. But they were present in small numbers (less than 15%) in areas V2, V3, V3A and V4. By contrast, 90% of the cells in the motion area of the superior temporal sulcus were directionally selective. 5. 8% of the cells in V2 had opponent colour properties. Cells with such properties were not found in V3, V3A or in the motion area of the superior temporal sulcus. By contrast, 54% of the cells in the V4 complex had opponent colour properties. 6. It is argued that despite its uniformity in cytoarchitectural appearance and in ocular interaction patterns, there is a functional division of labour within the prestriate cortex. Evidence for this is seen not only in the different concentrations of functional cell types in distinct areas of the prestriate cortex, but also in the differential anatomical and callosal connexions of each area.

Functional specificity of lateral geniculate nucleus laminae of the rhesus monkey

Abstract: 1. This study investigated the functional specificity of the lateral geniculate mucleus (LGN) of the rhesus monkey using microelectrode-recording techniques. 2. The parvocellular laminae of the LGN receive input predominantly from medium-conduction-velocity optic tract fibers, while the magnocellular laminae receive fast-conducting axons from the retina. 3. Cells projecting from the parvocellular layers to area 17 have medium-conduction velocities, while those from the magnocellular layers are fast conducting. 4. The majority of cells in the parvocellular layers have a concentric color-opponent receptive-field organization. The receptive fields of magnocellular layers cells are also concentrically organized, but their center-surround organization is independent of wavelength. 5. Responses in the parvocellular layers are more sustained than in the magnocellular layers. 6. Cells in the dorsal pair of parvocellular layers are predominantly on-center. In the ventral pair of parvocellular layers, most cells are off-center. 7. Blue-selective cells are found predominantly in the ventral pair of parvocellular layers. All of these found gave on-responses to blue stimuli.

The topographic organization of rhesus monkey prestriate cortex.

Abstract: 1. The topographic organization of prestriate visual cortex in the rhesus monkey has been studied both anatomically, by determining the pattern of termination of fibres passing through the corpus callosum, and physiologically, in the same animals, by plotting receptive field positions for different recording sites. Results are displayed on two-dimensional, "unfolded" maps of the cortex in the dorsal half of the occipital lobe. 2. Transcallosal fibres terminate in a narrow strip of cortex along the boundary between striate and prestriate areas and in a separate, broader, zone occupying much of the anterior bank of the lunate sulcus, the annectant gyrus, and the parietooccipital sulcus. The detailed pattern of inputs is highly complicated but shows considerable similarities from one animal to the next. 3. Physiological recordings confirmed earlier reports that regions where transcallosal fibres terminate correspond to representations of the vertical meridian in the visual field. This relationship is most precise along the striate-prestriate boundary and along the boundary of area V3 farthest from V1; it is less precise within area V4, where the pattern of transcallosal inputs is more complex. 4. A distinct, topographically organized visual area, named V3A, was found in the region between areas V3 and V4 in the lunate and parieto-occipital sulci. Area V3A differs from V2 and V3 in that both superior and inferior visual quadrants are represented in a single region of the dorsal occipital lobe. 5. The contralateral visual field is represented in a suprisingly complex fashion in areas V3A and V4. Within each area there are multiple representations of some, but perhaps not all, parts of the visual hemifield. It is unclear whether V3A and V4 should be more appropriately considered as sets of distinct sub-areas, each representing only a portion of the hemifield, or as larger areas with complicated internal topographies. 6. Most cells in areas V2, V3 and V3A are orientation selective but not selective for stimulus colour or direction of movement. In contrast, area V4 contains a higher incidence of colour selective cells and a lower incidence of orientation selectivity. These results support the notion of a functional division of labour within the prestriate cortex.

A Neural Map of Auditory Space in the Owl

Abstract: Auditory units that responded to sound only when it originated from a limited area of space were found in the lateral and anterior portions of the midbrain auditory nucleus of the owl (Tyto alba). The areas of space to which these units responded (their receptive fields) were largely independent of the nature and intensity of the sound stimulus. The units were arranged systematically within the midbrain auditory nucleus according to the relative locations of their receptive fields, thus creating a physiological map of auditory space.

Effects of picrotoxin and strychnine on rabbit retinal ganglion cells: lateral interactions for cells with more complex receptive fields.

Abstract: 1. The effects of picrotoxin and strychnine were tested on the receptive fields of direction sensitive cells, orientation sensitive cells, local edge detectors, uniformity detectors and large field units in the rabbit retina. 2. Picrotoxin eliminated the direction specificity and size specificity of 'on-off' and 'on' directionally sensitive cells for both black and white objects. Picrotoxin also made 'on' directionally sensitive cells responsive to faster velocities. 3. Picrotoxin eliminated the orientation specificity of orientation sensitive cells, and changed the bar-flank arrangement of the receptive field into a centre surround arrangement. Thus, the orientation specificity is due to inhibitory rather than excitatory mechanisms. 4. Picrotoxin altered the speed sensitivity of large field units so that they responded to slow speeds as well as fast ones, like centre surround Y cells. 5. Strychnine abolished the size specificity of local edge detectors and changed their speed specificity so that they responded to faster speeds. 6. Picrotoxin changed a uniformity detector into a sustained on centre cell. 7. Strychnine did not effect the direction specificity of directionally sensitive cells, the orientation specificity of orientation sensitive cells, or the speed specificity of large field units. Picrotoxin did not affect the size specificity of local edge detectors. 8. Picrotoxin and strychnine usually had opposing effects on the transient responses of these units to spots and annuli. In general picrotoxin prolonged and enhanced these responses at both on and off, and strychnine shortened them. 9. The effect of these drugs for every type of ganglion cell with complex receptive field properties was to make the receptive field more simple. The orientation selective cells, large field cells, 'on' direction selective cells and uniformity detectors seem to be centre surround cells with special properties that are abolished by these drugs. The 'on-off' direction selective cells and local edge detectors still on-off receptive fields, but in each case one of the drugs abolished the feature that was the basis for the cell's name.

Space and frequency are represented separately in auditory midbrain of the owl.

Abstract: 1. The influence of sound location and sound frequency on the responses of single units in the midbrain auditory area (MLD) of the owl (Tyto alba) were studied using a movable sound source under free-field conditions. With this technique, two functionally distinct regions in MLD have been identified: a tonotopic region and a space-mapped region. 2. MLD units were classified according to their receptive-field properties: 1) limited-field units responded only to sound from a small, discrete area of space; 2) complex-field units exhibited two to four different excitatory areas separated by areas of reduced response or inhibition: 3) space-preferring units responded best to a certain area of space, but their fields expanded considerably with increasing sound intensities; 4) Space-independent units responded similarly to a sound stimulus regardless of its location in space. 3. Limited-field units were located exclusively along the lateral and anterior borders of MLD. These units were tuned to sound frequencies at the high end of the owl's audible range (5-8.7 kHz). They usually responded only at the onset of a tonal stimulus; but most importantly, the units were systematically arranged in this region according to the azimuths and elevations of their receptive fields, thus creating a physiological map of auditory space. Because of this latter, dominant aspect of its functional organization, this region is named the space-mapped region of MLD. 4. The receptive fields of units in the larger, medial portion of MLD were of the space-independent, space-preferring, or complex-field types. These units tended to respond in a sustained fashion to tone and noise bursts, and these units were arranged in a strict frequency-dependent order. Based on this last property, this region is named the tonotopic region of MLD. 5. Because of the salient differences in the response properties of their constituent units, it is argued that the space-mapped region and the tonotopic region are involved in different aspects of sound analysis.

New properties of rabbit retinal ganglion cells.

Abstract: 1. Receptive fields of centre surround cells in the rabbit retina were investigated. There is a clear distinction between cells with sluggish responses, low spontaneous activity and slow conduction velocity (centre surround sluggish cells) and cells with brisk responses, higher spontaneous activity and faster conduction velocity (X and Y cells). The sluggish cells can be divided into sustained and transient types. X and Y cells can be distinguished from each other by their responses to a moving linear grating, a large rapidly moving object and whether or not there is a response to the alternation of certain stimuli. Some times the response to a rotating radial grating, the rate of spontaneous activity, and whether or not the response to spots and annuli was sustained or transient could also be used to distinguish these two types. The antidromic latency from electrical stimulation of the optic chiasm and the periphery effect did not distinguish X from Y. 2. Eleven colour coded units were investigated. They all gave on responses to blue light in the centre of their receptive field and off responses to green light in the periphery of their receptive field. The blue pigment had a spectral sensitivity peaking at about 465 nm. The other pigment peaked near 500 nm, like the rods but gave a response at high mesopic and probably photopic levels. In some cases there was evidence for excitatory input from the green receptors to the centre of the receptive field. All the colour coded cells had rapidly conducting axons and were on centre X cells by all criteria. 3. Eighty-five cells various types other than colour coded were tested for their thresholds at 420 nm and 590 nm. In all cases the results were explained by a pigment peaking close to 500 nm, even at high mesopic and low photopic levels, which suggests the existence of cones with a cyan pigment in them. 4. Conduction latency from stimulation at the optic chiasm was measured for cells with centre surround receptive fields and cells with more complex receptive fields. Both 'on-off' and 'on' directionally sensitive cells have short conduction latencies, overlapping X and Y cells. Orientation selective cells and local edge detectors have long conduction latencies, overlapping centre surround sluggish cells. The sample of uniformity detectors was too small to characterize...

Properties of concentrically organized X and Y ganglion cells of macaque retina.

Abstract: 1. Macaque retinal ganglion cells having concentrically organized receptive fields were classified as X- or Y-cells on the basis of the linearity or nonlinearity of their spatial summation to a "null" test of alternating contrast and drifting gratings. 2. When an alternating-phase, bipartite field positioned at the middle of the receptive field was used as a stimulus, X-cells had a null position, whereas Y-cells showed a doubling of the response frequency. When drifting sine-wave gratings of low contrast were used as a stimulus, X-cells showed a periodic modulation of their discharge having the same mean value for different spatial frequencies, whereas Y-cells showed a large increase in the mean value of their discharges. 3. X-cells had opponent-color responses that received cone-specific signals, i.e., center and surround responses were mediated by input from spectrally different types of cone, whereas Y-cells had broad-band spectral responses receiving mixed-cone signals, i.e., center and surround responses were totally or partly mediated by input from the same type(s) of cone. In most Y-cells, the spatially opponent responses from the center and the surround were mediated by the same types of cone and were thus spectrally nonopponent; other Y-cells showed spectral opponency, since one of the types of cone mediating responses of one region of the receptive field (e.g., center) was absent in the responses of the other region (e.g., surround). 4. X- and Y-cells projected to the lateral geniculate body. Opponent-color X- and Y-cells did not project to the superior colliculus, whereas a fraction of spectrally non-opponent Y-cells projected to this structure. 5. X-cells tended to have longer conduction latencies, less transient responses to small stimuli, and a more central retinal distribution than Y-cells; these differences, however, represented tendencies and not invariant properties. 6. The results show that the X/Y dichotomy of ganglion cells is present in the retina of macaques and indicate that the degree of the linearity of spatial summation of incoming cone signals to the cells is related to the degree of cone specificity of spectral inputs to the receptive-field mechanisms.

Functional organization of the corticofugal system from visual cortex to lateral geniculate nucleus in the cat (with an appendix on geniculo-cortical mono-synaptic connections).

Abstract: 1. In the cat visual cortex (VC), electrophoretic glutamate application at a depth corresponding to layer VI may have excitatory or inhibitory effects on relay cells of the lateral geniculate nucleus (LGN). Corticofugal excitation was seen, if the receptive field centers (RFCs) of the VC neurons recorded at the application site were within 2.3 ° of the RFCs of the LGN neurons under test. Inhibitory effects were seen if the RFCs of both cells were further apart up to 3.1 °. Glutamate application at more superficial cortical sites had no effect on LGN-neuron activity. 2. Cross-correlation analysis between spontaneous activities of simultaneously recorded VC and LGN neurons revealed excitatory cortico-geniculate connections in 18 pairs with RFCs separated by less than 1.7 °. In 15 pairs the peak latency of the excitation was 2–5 msec (3.4 msec in the average), 3 pairs showed long cortico-geniculate latencies (13–18 msec). The existence of a fast and slow cortico-geniculate system is suggested. 3. Inhibitory cortico-geniculate interaction was demonstrated with cross-correlation analysis in 8 pairs of which 4 had RFCs separated by more than 1.7 °. The onset latency of the inhibition was 2–7 msec except for 2 pairs with about 20 msec latency. 4. Most of the LGN neurons which were affected by cortical glutamate application or which showed an excitatory or inhibitory connection with a VC neuron were sustained cells, while the majority of VC neurons which were recorded in the effective glutamate application sites or which showed a significant interaction with LGN neurons in the cross-correlogram were binocularly driven and complex, with mostly large RFCs (mean diameter 3.5 °). They responded briskly to moving small spots as well as to moving slits. 5. It is concluded that the corticofugal excitatory effect is transmitted through monosynaptic links from VC neurons located in layer VI (complex cell) to LGN relay neurons (mostly sustained-cell) and this system is organized in a precise topographical manner. 6. In an Appendix neuron pairs which showed a positive correlation in the geniculo-cortical direction were described. The findings may support the view that complex as well as simple cells are driven monosynaptically from geniculo-cortical afferents of the sustained or transient type.

The third visual complex of rhesus monkey prestriate cortex.

Abstract: 1. Two independent but neighbouring visual areas, V3 and V3A, sharing a common cytoarchitectural plan, but in each one of which the visual fields are separately represented, have been studied anatomically, functionally, and in combined anatomico-physiological experiments. 2. The properties of single cells in the two areas are so similar, judged by the techniques used in this study, that it is often impossible to tell whether any one penetration was sampling from cells in V3 or V3A. This is especially so if the cells have receptive fields in the lower hemi-quadrants, since the vertical meridian of the lower visual fields is represented along the V3-V3A boundary and since a transition from V3 to V3A along this border is not accompanied by a shift in receptive field positions of cells. 3. Since the visual fields, including the vertical meridian, are separately represented in these two areas, and since regions of vertical meridian representation are callosally connected, a simple and certain method of specifying the boundary between V3 and V3A is to examine the degeneration following section of the callosal splenium. A heavy patch of degeneration then marks the V3-V3A boundary. Within this patch, however, is a sub-patch containing fewer callosal fibres, or none at all. The boundary between V3 and V3A was taken to be at this subpatch. 4. Since the horizontal meridian is represented at the V2-V3 boundary, and since V1 projects to both these areas, sending coarse fibres to V3 and fine fibres to V2, it was found that the boundary between V2 and V3 could be precisely drawn by making a lesion in the horizontal meridian representation in V1 and noting where, in the prestriate cortex, fine fibres give way to coarse ones, without an intervening gap. 5. Double tracer anatomical experiments, in which tritiated proline was injected into V1 of animals whose callosal splenium had been sectioned, showed that whereas V3 receives a direct input from V1, V3A does not. V3A, instead, was found to receive an input from V3. Double tracer anatomical experiments were undertaken to study a possible input from V2 to V3A. Although such experiments did not reveal a direct input from V2 to V3A, they were not entirely conclusive. 6. The vast majority of cells in V3 and V3A were binocularly driven, without obvious monocular preferences. Some cells, however, though responding to stimulation of the individual eyes, summated their responses to binocular stimulation. Others responded only when both eyes were simulataneously stimulated. In any oblique penetration, cells preferring binocular stimulation only occurred either singly or in groups. 7. In an oblique penetration, the shift from a cell responding to binocular stimulation only to one responding equally well to stimulation of either eye was not necessarily accompanied by a shift in orientational preferences, shifts in the former...

Merging of modalities in the optic tectum: infrared and visual integration in rattlesnakes

Abstract: The optic tectum of pit vipers (Crotalinae) contains a layer of infrared-sensitive neurons subjacent to the visual layer; these indirectly receive input from the facial pit organs. They respond transiently to the appearance or motion of warm objects within their 25 degrees to 70 degrees excitatory receptive fields (some have inhibitory regions) and presumably allow the snake to orient or strike toward prey. The infrared and visual spatiotopic tectal maps have similar but not identical axes; the infrared magnification is greater than that for vision. Bimodal neurons have receptive fields for each modality that reflect the disparity of the two maps. This finding suggests that (i) during development the infrared and visual fibers spread out independently to fill available tectal sites and (ii) bimodal neurons form local connections without regard to establishing spatial correspondence between the two modalities.

Color vision mechanisms in monkey striate cortex: dual-opponent cells with concentric receptive fields

Abstract: 1. I have recorded with tungsten microelectrodes from single cells in the monkey's visual cortex and have specifically studied those neurons which were sensitive to the color of the stimulus. In the primate striate cortex there are four classes of color-coded cells. The cells described in this paper have concentric receptive fields with one red-green opponent-color system in the field center and the opposite organization in the surround. These dual-opponent cells were nost sensitive to the simultaneous presentation of two different colors, one covering the field center and the other illuminating the surround. They are probable involved in the perception of simultaneous color-contrast phenomena. 2. Spectral sensitivity curves revealed that both the field centers and the surrounds received opposite types of inputs from red-sensitive and green-sensitive cones. None of the cells tested had inputs from rods. 3. Area-sensitivity curves showed that peripheral suppression was present for both phases of the center opponent-color system. The boundary between the center and the surround was the same for both sets of opponent systems. Some cells had "silent" surrounds, which did not respond to annular stimuli. 4. Multiple-unit recordings from a concentric cell and one of its presumed afferents yielded information regarding its possible synaptic inputs. In some cases the cells appeared to receive contacts from red/green opponent-color geniculated fibers with circular receptive fields that lacked an antagonistic surround (similar to Wiesel and Hubel's (37) type II class). In other instances the afferents had on-center, off surround receptive fields or the reverse, but received inputs from only one cone type, either red or green (similar to Wiesel and Hubel's type III class). 5. Concentric cells were always driven by only one eye. 6. The laminar distribution of these cells was limited almost entirely to layer IV and its subdivisions. 7. The cumulative evidence presented in this paper indicates that the concentric cells probably received direct geniculate inputs and, therefore, they are the first cortical stage in the integration of color-contrast information.

Receptive field integration and submodality convergence in the hand area of the post-central gyrus of the alert monkey.

Abstract: 1. An exploration of the occurrence of different functional cell types was made in the three cytoarchitectural subdivisions (areas 3, 1 and 2) of the hand area of the post-central gyrus of the monkey. The functional properties of 632 cells were studied using the transdural micro-electrode recording method. 2. Over half of the neurones studied (57%) belonged to the class of simple skin neurones that were related either to rapidly adapting (272 neurones) or slowly adapting (seventeen neurones) cutaneous receptors or to both (seventy-one neurones). The simple skin neurones were particularly common in the anterior part of S I where they constituted 60% of the cells. More complicated cutaneous neurones made up 10% of the total sample. They were more common in the posterior part of the gyrus. 3. Altogether ninety-two neurones (15%) were related to subcutaneous or deeper receptors. Another seventy-one neurones (11%) exhibited convergence of skin input and input from deep receptors. A smaller group of forty-seven undamaged neurones (7%) were unrelated to stimuli of the types described above. 4. In tangential electrode penetrations made along the anterior and posterior banks of the gyrus, functional columns were found to be 500 micrometers wide on the average; this width is comparable with that of ocular dominance columns and visual orientation hypercolumns. 5. Correlation of the functional types of cells with cytoarchitecture showed that the complexity of the functional properties of the neurones increased posteriorly. The receptive field size also increased toward posterior. The changes that take place in the functional properties of cells when moving across different cytoarchitectural areas suggests intracortical information processing which leads to handling of larger body regions and more complex combinations of information in the cellular elements of the posterior part of the post-central gyrus.

Properties of ganglion cells with atypical receptive-field organization in retina of macaques.

Abstract: 1. About 10% of a sample of 436 cells recorded in the retina of macaques had receptive fields lacking a center-surround organization. These cells had a diffuse extrafoveal distribution, they were l...

Movement-sensitive and direction and orientation-selective cutaneous receptive fields in the hand area of the post-central gyrus in monkeys.

Abstract: 1. In the hand area of the post-central gyrus of three alert Macaca speciosa monkeys neurones related to cutaneous receptors but not activated by simple touch on the receptive field were recorded using the transdural micro-electrode recording technique. Thirty-six cells were found to have complex cutaneous receptive field properties. These neurones were subdivided into the following three groups. 2. Nine neurones were not activated by punctate stimuli on the receptive fields but responded well to movement along the skin. The activity of these neurones was not affected by the direction of movement; nor was it sensitive to different textures of the moving surface. 3. Eighteen neurones responded to cutaneous movement along the skin surface in a particular direction giving no response to stimulation in the opposite direction and intermediate responses to intermediate directions. Similar responses were evoked from different subparts of the receptive field. 4. Nine neurones responded well to an edge placed on the skin in an optimal orientation or moved along the skin in a direction perpendicular to the edge. A maximal response was produced by stimuli of the same optimal orientation in different parts of the receptive field. The significance of the stimuli to the monkey had only a minor influence on the magnitude of the responses of these neurones and no influence on the receptive field properties. 5. The occurrence of the complex cutaneous cells increased from anterior to posterior within the post-central gyrus and most of them were found in Brodmann's area 2. Thus we postulate that the complex receptive field properties arise as a consequence of cortical processing in a network in which postsynaptic one-way lateral inhibition generates the directional properties of the neurones. 6. The complex cutaneous neurones constituted only 6% of the neurones studied in the hand area of the post-central gyrus. Thus the prevalence of neurones with elongated and direction-selective receptive fields is low in the primary somatosensory cortex in comparison with the visual cortex. These neurones may, however, serve the sterognostic capcity of the hand by contributing information about stimulus motion, orientation and direction of movement on the skin.

The representation of facial temperature in the caudal trigeminal nucleus of the cat.

Abstract: 1. In cats anaesthetized with urethane, extracellular micro-electrode recordings were made in the marginal layer of the trigeminal nucleus caudalis between the level of the obex and the Cl rootlets. 2. Nearly 300 neurones were found whose discharge rate increased with a reduction of facial temperature and a few which were excited by an increase in temperature. Over half of the neurons in each group were specifically sensitive to temperature and the remainder had a weak input from mechanical stimulation of the face. 3. Thermal receptive fields were all ipsilateral and found most frequently on the nose, lips, lower eyelid and pinna. There was a somatotopic organization of the receptive fields according to the three divisions of the trigeminal nerve. 4. On quantitative thermal testing, the neurones showed responses which were similar to those of the skin temperature sensors. 5. The thermal neurones could be antidromically fired by a stimulating electrode in the thalamus.

Studies of visual function and its decay in mice with hereditary retinal degeneration

Abstract: Functional implications of mouse hereditary retinal degenera- tion have been studied at the level of the superior colliculus and visual cortex in the C57BL/6J-le rd strain. On autoradiography at a light-microscopic level, following eye injection with radioactive compounds, central visual structures appeared normal. A slight reduction in ipsilateral retinal projection was proba- bly related to reduced retinal pigmentation associated with the light ear (le) mutation. In recordings from visual cortex and tectum in rd mice older than five months the cells discharged with highly rhythmic maintained activity. This ongoing activity depended on retinal input, since temporary asphyxia of the eye stopped it immediately. The frequency of the rhythm was influenced by the anesthesia. In these older mice no visual receptive fields could be mapped, but in a few tectal recordings it was possible to suppress the maintained activ- ity by diffuse, very intense illumination. As in normal mice, no auditory or somatosensory responses were observed in the visual cortex or upper tectal layers. In recordings from tectum before the age of three weeks retinotopic to- pography and receptive fields were normal. By day 24 no receptive fields could be recorded from parts of the tectum representing the central 90-100" of the visual field, whereas within a peripheral ring responses were still roughly nor- mal under photopic conditions. Over the following four months these peripheral responses faded away slowly. Incremental thresholds, especially in the scotopic range, were elevated, rising slowly to unmeasurable values. Similarly during dark adaptation the thresholds fell to values several log units above those reached in normal mice; these values of dark adapted thresholds in rd mice rose with age. This is consistent with morphological changes known to occur in the retina as a consequence, of the rd mutation the rods degenerating before the cones.

Statistical dependence between neighboring retinal ganglion cells in goldfish

Abstract: Simultaneous recordings were made of the spontaneous discharge of neighboring retinal ganglion cells in goldfish. Crosscorrelation analysis indicates two types of correlation. Neighboring units with like receptive field organization tend to discharge together while units having complementary receptive field organization tend not to discharge together.

Projections to lateral vestibular nucleus from cerebellar climbing fiber zones.

Abstract: 1. The olivary projections to the lateral vestibular nucleus (LVN), direct and excitatory through climbing fiber collaterals and indirect and inhibitory through climbing fiber activated Purkinje cells, were investigated in cats with the spinal cord transected at C3 sparing only the contralateral ventral funiculus. In this preparation all spinocerebellar paths are interrupted except the ventral spino-olivocerebellar paths (VF-SOCPs). Three FV-SOCPs responding with different latencies and receptive fields on limb nerve stimulation project to different sagittal zones in the anterior lobe vermis: the a-zone medially and the b-zone laterally in the vermis and the c1-zone in the extreme lateral part of the vermis and the medial part of the pars intermedia. 2. The EPSPs evoked through climbing fiber collaterals and the following IPSPs evoked through climbing fiber activated Purkinje cells were recorded intracellularly from LVN neurons on limb nerve stimulation. Simultaneously the climbing fiber responses evoked in Purkinje cells located in the a-, b- and c1-zones were recorded as positive potentials from the cerebellar surface. 3. Three groups of LVN neurons were distinguished: X neurons (about 20%) which did not receive excitation or inhibition from the olivary paths, aCF neurons (about 5%) which received excitation and inhibition from the olivary path projecting to the a-zone, and bCF neurons (about 75%) which received excitation and inhibition from the olivary path projecting to the b-zone. No LVN neurons were related to the c1-zone. 4. The aCF and bCF neurons occurred intermingled throughout the LVN. The X neurons occurred predominantly in its ventral part. 5. The findings are discussed in relation to a hypothesis of cerebellar organization.

Center-surround organization of auditory receptive fields in the owl

Abstract: The spinal receptive fields of specialized auditory units in the midbrain of the barn owl (Tyto abla) contain two functionally antagonistic areas: an excitatory center and an inhibitory surround. The response of these units represents the balance of acoustic activation of the two areas, which in turn depends upon the location, intensity, and spectral content of the sound stimulus.

Receptive-field properties of neurons in different laminae of visual cortex of the cat.

Abstract: 1. Receptive-field properties of neurons in the different layers of the visual cortex of normal adult cats were analyzed quantitatively. Neurons were classified into one of two groups: 1) S-cells, which have discrete on- and/or off-regions in their receptive fields and possess inhibitory side bands; 2) C-cells, which do not have discrete on- and off-regions in their receptive fields but display an on-off response to flashing stimuli. Neurons of this type rarely display side-band inhibition. 2. As a group, S-cells display lower relative degrees of binocularity and are more selective for stimulus orientation than C-cells. In addition, within a given lamina the S-cells have smaller receptive fields, lower cutoff velocities, lower peak responses to visual stimulation, and lower spontaneous activity than do the C-cells. 3. S-cells in all layers of the cortex display similar orientation sensitivities, mean spontaneous discharge rates, peak response to visual stimulation, and degrees of binocularity. 4. Many of the receptive-field properties of cortical cells vary with laminar location. Receptive-field sizes and cutoff velocities of S-cells and of C-cells are greater in layers V and VI than in layers II-IV. For S-cells, preferred velocities are also greater in layers V and VI than in layers II-IV. Furthermore, C-cells in layers V and VI display high mean spontaneous discharge rates, weak orientation preferences, high relative degrees of binocularity, and higher peak responses to visual stimulation when compared to C-cells in layers II and III. 5. The receptive-field properties of cells in layers V-VI of the striate cortex suggest that most neurons that have their somata in these laminae receive afferents from LGNd Y-cells. Hence, our results suggest that afferents from LGNd Y-cells may play a major part in the cortical control of subcortical visual functions.