Showing papers on "Receptive field published in 1975"

The contribution of inhibitory mechanisms to the receptive field properties of neurones in the striate cortex of the cat.

Abstract: 1 The iontophoretic application of the GABA antagonist bicuculline to simple and complex cells in the striate cortex of the cat produced extensive modifications of receptive field properties These modifications appear to relate to a block or reduction of GABA-mediated intracortical inhibitory influences acting on the cells examined 2 For simple cells the effects of bicuculline on receptive field properties involved a loss of the subdivision of the receptive field into antagonistic "on" and "off" regions, a reduction in orientation specificity and a reduction or elimination of directional specificity 3 The effect on the "on" and "off" subdivisions of the simple cell receptive field was such that all stationary flashing stimuli, whether covering the whole receptive field, or located within the receptive field over a previously determined "on" or "off" region, resulted in an "on and off" response 4 The orientation specificity of complex cells was reduced during the application of bicuculline such that in many cases the original specificity of the cell was virtually lost with the response to the orientation at 90 degrees to the optimal being of similar magnitude to the optimal The directional specificity of complex cells was generally less affected than that of simple cells Often when large changes in orientation specificity were observed the directional specificity was relatively unaffected 5 For some cells apparently showing to all visual stimuli only inhibitory responses, the application of bicuculline resulted in the appearance of excitatory responses 6 In all cases receptive field properties reverted to the original state after termination of the bicuculline application It was not generally possible to duplicate the effects of bicuculline by raising neuronal excitability with iontophoretically applied glutamate 7 On the basis of these results it is suggested that the normal subdivision of the simple cell receptive field into separate "on" and "off" regions and its directional specificity are dependent on intracortical inhibitory processes that are blocked by bicuculline The orientational tuning of simple cells conversely appears to be largely determined by the excitatory input but normally enhanced by lateral type inhibitory processes acting in the orientation domain 8 It also appears that the excitatory input to some complex cells is not orientation specific This suggests that for these cells it is extremely unlikely that they receive an orientation specific excitatory input from simple cells

Functional properties of ganglion cells of the rhesus monkey retina.

Abstract: Three general classes of cells were identified in a sample of 460 cells recorded from all areas of the retina subserving the central 40 degrees of vision in the rhesus monkey. 2. One class (colour-opponent) had sustained colour-opponent responses and concentrically organized receptive fields, in which usually one cone mechanism mediated the centre response and one or two different cone mechanisms mediated the antagonistic surround. A few cells of this class had non-concentric (co-extensive) receptive field organization. 3. A second class (broad-band) had transient responses and concentrically organized receptive fields, in which usually two cone mechanisms mediated the centre response. In most cells, the surround had the same spectral sensitivity as the centre and the cells had non-colour opponent responses. In other cells, the surround had a spectral sensitivity different to that of the centre and the cells had colour-opponent responses. 4. The third class (non-concentric) did not have concentrically organized receptive fields. One group of cells had extremely phasic on-, off- or on-off responses and no spontaneous activity, another group had characteristically regular spontaneous activity and was responsive only to moving stimuli. 5. Cells of the colour-opponent class with concentric receptive fields had the smallest centre-sizes, which did not vary markedly from cell to cell (mean 15 mum); cells of the non-concentric class with phasic responses had the largest centre-sizes, which varied from cell to cell. 6. Colour-opponent cells comprised the highest proportion of cells near the foveola; broad-band cells comprised the highest proportion in the more peripheral areas of the retina; non-concentric cells were equally represented in all areas.

Innate and environmental factors in the development of the kitten's visual cortex.

Abstract: 1. This is a study of the receptive fields of 771 cells recorded in the visual cortex of twenty-five kittens reared normally or subjected to various kinds of visual deprivation or environmental manipulation. 2. Kittens deprived of patterned visual experience, by dark rearing or diffuse occlusion of the eyes, have a majority of cirtical neurones with little or no specificity for the orientation or axis of movement of visual stimuli. However, in such deprived animals, especially those younger than 3 weeks, there are a number of genuinely orientation selective cells. They are broadly "turned" (by adult standards), they are almost always of the simple type, are heavily dominated by one eye, and are found mainly in the deeper layers of the cortex, especially layer IV. 3...

Cognitron: A self-organizing multilayered neural network

Abstract: A new hypothesis for the organization of synapses between neurons is proposed: "The synapse from neuron x to neuron y is reinforced when x fires provided that no neuron in the vicinity of y is firing stronger than y". By introducing this hypothesis, a new algorithm with which a multilayered neural network is effectively organized can be deduced. A self-organizing multilayered neural network, which is named "cognitron", is constructed following this algorithm, and is simulated on a digital computer. Unlike the organization of a usual brain models such as a three-layered perceptron, the self-organization of a cognitron progresses favorably without having a "teacher" which instructs in all particulars how the individual cells respond. After repetitive presentations of several stimulus patterns, the cognitron is self-organized in such a way that the receptive fields of the cells become relatively larger in a deeper layer. Each cell in the final layer integrates the information from whole parts of the first layer and selectively responds to a specific stimulus pattern or a feature.

Responses to visual stimulation and relationship between visual, auditory, and somatosensory inputs in mouse superior colliculus.

Abstract: The superior colliculus was studied in anesthetized mice by recording from single cells and from unit clusters. The topographic representation of the visual filed was similar to what has been found in other mammals, with the temporal part of the contralateral visual field projecting posteriorly and the inferior visual field projecting laterally. At the anterior margin of the tectum receptive fields recorded through the contralateral eye and invaded the ipsilateral visual hemifield for up to 35 degrees, suggesting that the entire visual field through one eye is represented on the contralateral superior colliculus. Cells located closest to the tectal surface had relatively small receptive fields, averaging 9 degrees in center diameter; field sizes increased steadily with depth. The prevailing cell type in the stratum zonal and superficial gray responded best to a small dark or light object of any shape moved slowly through the receptive-field center or to turning a small stationary spot on or off. Large objects or diffuse light were usually much less effective. Less than one-quarter of superficial layer cells showed directional selectivity to a moving object, the majority of these favoring up and nasal movement. The chief visual cell type in the stratum opticum and upper part of the intermediate gray resembled in the newness neurons described for many other vertebrates: they had large receptive fields and responded best to up and nasal movement of a small dark or light object, whose optimal size was similar to the optimum for upper-layer cells. If the same part of the receptive field was repeatedly stimulated there was a marked tendency to habituate. Only very few cels responded to the ipsilateral eye. Intermixed with visual cells in the upper part of the intermediate gray were cells that responded to somatosensory or auditory stimuli. Here bimodal and trimodal cells were also seen. In deeper layers somatosensory and auditory modalities tended to take over. These two modalities were not segregated into sublayers but rather seemed to be arranged in clusters. Responses to somatosensory and auditory stimuli were brisk, showing little habituation to repeated stimulation.

Receptive fields of single cells and topography in mouse visual cortex.

Abstract: The visual cortex was studied in the mouse (C57 Black/6J strain) be recording from single units, and a topographic map of the visual field was constructed. Forty-five percent of the neurons in striate cortex responded best to oriented line stimuli moving over their receptive fields; they were classified as simple (17%), complex (25%) and hypercomplex (3%). Of all preferred orientations horizontal was most common. Fifty-five percent of recpetive fields were circularly symmetric: these were on-center (25%), off-center (7%) and homogeneous on-off in type (23%). Optimal stimulus velocities were much higher than those reported in the cat, mostly varying between 20 degrees and 300 degrees/sec. The field of vision common to the two eyes projected to more than one-third of the striate cortex. Although the contralateral eye provided the dominating influence on cells in this binocular area, more than two-thirds of cells could also be driven through the ipsilateral eye. The topography of area 17 was similar to that found in other mammals: the upper visual field projected posteriorly, the most nasal part mapped onto the lateral border. Here the projection did not end at the vertical meridian passing through the animal's long axis, but proceeded for at least 10 degrees into the ipsilateral hemifield of vision, so that at least 20 degrees of visual field were represented in both hemispheres. The magnification in area 17 was rather uniform throughout the visual field. In an area lateral to area 17 (18a) the fields were projected in condensed mirror image fashion with respect to the arrangement of area 17. Medial to area 17 a third visual area (area 18) was again related to 17 as a condensed mirror image.

Segmental and supraspinal actions on dorsal horn neurons responding to noxious and non-noxious skin stimuli.

Abstract: 1. (1) Single dorsal horn neurons have been recorded extracellularly in 8 anesthetized (pentobarbital-Na) cats and in 1 unanesthetized decerebrated cat. The animals were either spinalized by transection of the cord at L 1 (6 experiments) or a cold block was used for reversible spinalization at L 1 (3 experiments). 2. (2) Sixty-five units were recorded in the dorsal horn and in the dorsolateral funiculus which could be excited by electrical stimulation of the ipsilateral plantar nerves and by natural stimulation of the skin in the foot region. The recording position of the microelectrode was verified histologically. 3. (3) According to their excitability by electrical stimulation of the afferent nerve fibers and by natural stimulation of the receptive fields, 2 major classes of units could be distinguished in the spinalized cat. Class 1 cells were excited by electrical stimulation of myelinated axons (group II) in the plantar nerves. Four out of 9 could be excited by low threshold cutaneous mechanoreceptors; 5 had input probably from deep receptors. Class 2 cells , which were more than twice as common as class 1 cells, could, like the latter, be excited by electrical stimulation of group II myelinated afferent fibers in the plantar nerves, but in addition, were excited by electrical stimulation of C-fibers. 4. (4) When stimulated naturally, virtually all of the class 2 cells received an excitatory input from low threshold cutaneous mechanoreceptors and also from receptors excited by noxious radiant heat stimulation in their receptive fields. They responded to noxious heating in a quantitatively similar manner as the primary C-heat nociceptors.

The representation of the visual field in the lateral geniculate nucleus of Macaca mulatta.

Abstract: Microelectrode recording techniques were used to investigate the projection of the visual field into the lateral geniculate nucleus (LGN) of Macaca mulatta. The data were used to construct charts plotting visual direction, designated in terms of azimuth and elevation, onto sections of the nucleus cut in coronal, sagittal and horizontal Horsley-Clarke planes. The projection of the horizontal meridian divides the LGN along its plane of symmetry into a medial-superior half having negative elevations and a lateral-inferior half having positive elevations. Elevations become more positive or negative with distance from this plane. Azimuths closest to the vertical meridian are located posteriorly, while the most peripheral azimuths are found at the anterior pole. Two families of surfaces representing visual directions of constant azimuth and elevation are described. Visual field zones of increasing eccentricity are represented serially along the posterior-anterior axis of the LGN, with the foveal area restricted to the posterior pole and the monocular crescent projecting to the anterior pole. The mapping is completely continuous across the horizontal meridian. The edges of the stacked cell laminae exposed around the periphery of the LGN form an oval band which receives the projection of the perimeter of the contralateral hemifield. The vertical meridian is represented by the posterior two-thirds of this band, while the periphery of the hemifield projects to the anterior third. The central visual field out to the optic disc is represented by six cell layers, while the rest of the binocular field projects to four layers only (2 parvocellular and 2 magnocellular). The monocular crescent is represented by one parvocellular and one magnocellular layer. Features associated with the projection column of the optic disc are integrated into the transition from six to four layers. Details of the receptive field topography in the vicinity of the optic disc discontinuities indicate that these gaps are produced by intralaminar mechanisms. The magnification factor (mm3/steradian) increases monotonically from peripheral visual fields to the foveal center, varying over a range of three decades. This range is intermediate between those derived from data reported in the literature for the retina and the striate cortex. The ratio of LGN magnifications at any two angular eccentricities is a power function, with an exponent of 1.34, of the corresponding ratio of retinal ganglion cell densities. Similarly, the ratio of cortical magnifications (mm2/steradian) at any two eccentricites is a power function, with an exponent of 1.35, of the corresponding ratio of LGN magnifications.

Receptive-field characteristics of single neurons in lateral suprasylvian visual area of the cat.

Abstract: The visual receptive fields of 213 cells in the lateral suprasylvian visual cortex (LS, or Clare-Bishop area) were studied in cats anesthetized with nitrous oxide. Eighty-one percent of the cells were directionally selective. They responded poorly to stationary stimuli flashed on or off, but gave a directionally selective response to stimuli moving through the receptive field. Most of these had a single preferred direction and an opposite null direction. They typically responded to a range of directions of stimulus movement from 45 to 90 degrees to either side of the preferred direction. Small stimuli (1-2 degrees or smaller) typically were effective and 87% of the directionally selective cells showed spatial summation. About 32% had inhibitory mechanisms which decreased the response of the cell if the stimulus exceeded a maximum size. There was little or no evidence that LS area cells were orientation selective or sensitive to variations in stimulus shape independent of size.

Organization of cat striate cortex: a correlation of receptive-field properties with afferent and efferent connections.

Abstract: The purposes of this study were 1) to relate the receptive-field characteristics of area 17 cells to their afferent and efferent connections, and 2) to obtain quantitative data from area 17 neurons for later comparison with area 18 cells. Intra- and extracellular recordings were obtained in paralyzed preparations which were anesthetized with nitrous oxide. The connectivities of the recorded cells were determined from responses to electrical stimulation of afferent and efferent pathways. In parallel to the classification of units as simple and complex cells, the receptive fields were grouped in four classes according to the spatial arrangement of on- and off-areas; class I, fields with exclusive on- or off-areas; class II, fields with spatially separate on- and off-areas; class III, fields with mixed on-off areas; class IV, fields which could not be mapped with stationary stimuli. The results from electrical stimulation suggest two major classes of cells: cells in the first group are driven mainly or exclusively by LGN afferents. They rarely receive additional excitation from intrinsic or callosal afferents and rarely possess corticofugal axons. Cells in the second group receive either converging inputs from LGN afferents and further intrinsic afferents or only from intrinsic afferents. They frequently received additional input from callosum and from recurrent collaterals of corticofugal axons. They project subcortically more often than cells in the first group. Cells in both groups can be driven either by X- or Y-type afferents. Cells in the first group have mainly class I and class II fields or simple fields, whereas the neurons in the second group have mainly class III and class IV fields or complex fields. Thus, simple and complex cells differ in their connectivity patterns, but the discriminative parameter is neither the selective connection to the X- or the Y-system nor, in a strict sense, the synaptic distance from subcortical input. From the combined consideration of receptive-field properties and connectivity patterns it is concluded that class I and class II cells or simple cells are concerned mainly with the primary analysis of subcortical activity, whereas class III and class IV cells or complex cells perform a correlative analysis between highly convergent activity from extrinsic and intrinsic afferents.

The velocity tuning of single units in cat striate cortex.

Abstract: 1. The activity of single units was recorded from the striate cortex (area 17) of anaesthetized, paralysed cats. Responses to stimuli moving at different velocities were examined. 2. Peak evoked firing frequency, rather than fotal evoked spikes, is used throughout as a measure of response. The former mea-ure gives curves of response vs. velocity that correlate well with curves of contrast sensitivity vs. velocity, wheras the latter does not. 3. Cortical receptive fields were classified according to the criteria of Hubel & Wiesel. Simple cells were found to prefer lower velocities (mean 2-2 deg sec-1) than complex cells (mean 18–8 deg sec-1). The response of simple cells to stimuli moving faster than 20 deg sec-1 is generally poor; complex cells usually discharge briskly to these speeds. 4. Cells classified as hypercomplex by the end-inhibition criterion were further chara-terized as type I or type II, according to the suggestion of Dreher (1972). Type I units are indistinguishable from simple cells in their velocity tuning, and type II units equally clearly resemble complex cells. These results are therefor consistent with Dreher's sbudivision. 5. Teh selectivity of cells for velocity is variable but can be quite marked. The average selectivities of simple and complex cells are not significantly different. There is an inverse correlation between preferred velocity and the sharpness of velocity selectivity for simple cells; no trend is apparent for other cell types. 6. No clear correlation is observed between the velocity preferances of units and their degree of direction selectivity, or receptive field arrangement. Simple cells with ‘sustainef’ temporal responses to flashed stimuli tend to prefer slower rates of movement than ‘transient’ ones, and to be less selective for velocity. 7. The results for different cortical cell-types are compared with the velocity tuning of X- and Y-cells in the lateral geniculate nucleus.

The control of retinal ganglion cell discharge by receptive field surrounds.

Abstract: 1. This paper describes the behaviour of the receptive field surround, and how surround signals combine with those from the centre to generate the discharge of the retinal ganglion cells of the cat. 2. A small test spot is flashed upon the middle of the receptive field of an on-centre X-cell, alone, or together with a concentric annulus of fixed luminance. The reduction in discharge brought about by the annulus is independent of spot luminance. From this it is inferred that centre and surround signals combine additively. 3. Knowing that the combination of signals is additive, the surround signal can be estimated by comparing the ganglion cell's response to diffuse illumination of its receptive field with that to an equiluminous spot which optimally stimulates the centre while encroaching minimally upon the periphery. 4. Application of this technique to X-cells shows that although the surround seems to have a threshold, it is at its most sensitive in the dark-adapted eye, and typically is only 0.3-0.5 log units less sensitive than the centre. 5. Centre and surround sensitivities are decreased from their dark-adapted levels by increasing background illumination, but the decline of surround sensitivity is initially less rapid than that of the centre. Thus with increasing light-adaptation the surround becomes relatively more sensitive. In the light-adapted eye centre and surround are about equally sensitive to diffuse illumination. 6. Although, in the dark-adapted eye, illumination of the receptive field periphery of an on-centre unit depresses firing, removal of that illumination produces no off-discharge. Off-discharges appear only when background illumination exceeds about 104 quanta (507)/deg 2 sec. This confirms Barlow & Levick (1969b). 7. In the dark-adapted eye surround latency is longer than that of the centre. With increasing background illumination the latency difference is reduced. 8. For X-cells, the rate of the maintained discharge depends to some extent on the balance of centre-surround antagonism. But this antagonism is not the major factor accounting for the relative constancy of mean rate at high background luminances, for the rate then can be almost independent of the size of a steady pot. 9. The mean rate of discharge of Y-cells seems to depend even less upon the balance of centre-surround antagonism. 10. Y-cell surrounds could not properly be isolated with the optimal spot-diffuse illumination technique, so detailed measurements of their behaviour were not made. However, the dark-adapted surround appear to be as sensitive as those of X-cells.

Directionally sensitive ganglion cells in the rabbit retina: specificity for stimulus direction, size, and speed.

Abstract: The receptive fields of directionally sensitive ganglion cells in the rabbit retina were analyzed. Several types of experiment showed that each point within the receptive field of the cell is inhibited by a fairly wide area of points around it, lying on each side of the preferred-null axis as well as along the preferred-null axis in the preferred direction. The excitatory or responsive receptive field of these cells has an inhibitory surround: this inhibitory surround appears to be simply an extension of the inhibition that occurs within the center of the receptive field. Points toward the edge of the responsive receptive field are inhibited from an area around them which extends into the center of the receptive field and also into the inhibitory surround. Directionally sensitive retinal ganglion cells respond to moving spots better than to moving bars. This is particularly true for objects moved perpendicularly to the preferred-null axis. In some cells a spot moved perpendicularly to the preferred-null axis will give a substantial response, whereas a bar moved in the same direction will give no response at all. This phenomenon can be explained by the inhibitory area which surrounds each point within the receptive field; since this inhibitory area is asymmetrical, it is also responsible for the cell's directional sensitivity. When two bars oriented perpendicular to the preferred null axis are flashed, one after the other, the response to the second bar is nearly always reduced by the presentation of the first bar. This is true for many temporal and spatial sequences corresponding to movement in the preferred direction, as well as those corresponding to movement in the null direction. However, there are temporal and spatial sequences, corresponding to movement in the preferred direction, for which the response to the second bar is unaffected by the presentation of the first bar. The time delay for this does not vary from cell to cell--it is always approximately 20 ms for on-off directionally sensitive cells and approximately 180 ms for on directionally sensitive cells. The spatial separation does vary from cell to cell, between 0.13 degrees and 1.2 degrees in 11 on-off directionally sensitive cells. This spatial separation, which gives linear summation of the response to two bars flashed 20 ms apart in the preferred direction, is correlated with the speed of movement which gives the best response for a bar moved through the receptive field in the preferred direction.

A quantitative study of the projection area of the central and the paracentral visual field in area 17 of the cat. II. The spatial organization of the orientation domain.

Abstract: Cells in cat's area 17 respond optimally if elongated contrasts are presented at a certain angle or orientation with respect to the retina, or to the visual field, respectively (Hubel and Wiesel, 1962). The preferred orientation and the range of orientation sensitivity of cells in close proximity to one another have been determined in order to investigate the spatial arrangement of the orientation domain in area 17. 1. A slight overrepresentation of vertical and horizontal orientations is seen in cells with complex receptive fields, whereas in cells with simple fields all orientations are represented to an equal degree. The orientation selectivity, defined as the halfwidth of tuning curves constructed from the cells response to a moving stimulus, is less than 60 degrees in more than 80% of all cells investigated, and is on the average 20-30 degrees smaller in cells with simple than in cells with complex receptive fields. 2. In 80% of all cases considered the difference in the preferred orientation between two cells less than 200 mum horizontally distant in area 17 is less than 30 degrees, which is of the order of an individual cells orientation selectivity. Each cell, therefore, will respond to some extent to that orientation which is preferred by the cells in the immediate surroundings. 3. Sequential changes in the preferred orientation between cells successively recorded are observed as the postlateral gyrus is explored from anterior to posterior and from medial to lateral. On these general trends a random variation in the preferred orientation between neighbouring cells of the order of 5-10 degrees is superimposed. One orientation sequence (180 degrees) occupies 700-1200 mum, so that on the average a change in the preferred orientation of the order of 10 degrees is complete after 50 mum distance in the cortex measured parallel to the pial surface. Assuming that 18 different orientations (+/- 5 degrees) functionally represent one complete orientation sequence it is found that 'all' orientations are functionally represented by the cells contained in a cortical cylinder of 300-700 mum in diameter. 4. Cells having the same preferred orientation are grouped together in cortical regions which appear in crossection as a band or a spot. These regions have been termed iso-orientation bands or spots. The diameter of the spots and the small diameter of the bands do not exceed 100 mum. Taking an average orientation selectivity of 40 degrees for cells vertically aligned in area 17 it is calculated that cells situated 100 mum to either side of an iso-orientation band or around an iso-orientation spot still respond with 50% of the discharge to their own optimal orientation ...

Spatial and temporal properties of ‘sustained’ and ‘transient’ neurones in area 17 of the cat's visual cortex

Abstract: Receptive field properties of cells in area 17 of the visual cortex in the cat have been studied by quantitative methods The cortical cells were classified as ‘sustained’ or ‘transient’ according to their response to a stationary, optimal bar at the receptive field centre, this being analogous to the classification of retinal ganglion cells according to their response to a stationary, optimal spot Evidence is presented that the ‘sustained/transient’ classification is independent of the ‘simple/complex’ classification ‘Sustained’ cells of both ‘simple’ and ‘complex’ types had spatial frequency tuning curves with a sharp low-frequency cut, whereas ‘transient’ cells, both ‘simple’ and ‘complex’, had tuning curves with a shallow low-frequency cut, and on average were tuned to lower spatial frequencies than ‘sustained’ cells ‘Sustained’ cells of both ‘simple’ and ‘complex’ types, had temporal frequency tuning curves with a shallow low-frequency cut, whereas ‘transient’ cells had curves with a sharp low-frequency cut, and on average were tuned to higher temporal frequencies than ‘sustained’ cells The results indicate that ‘sustained’ and ‘transient’ cortical cells retain the spatial and temporal properties of ‘sustained’ and ‘transient’ retinal ganglion cells, respectively, and thus the two groups of neurones are organised in parallel throughout the visual system, the ‘sustained’ channel providing high spatial resolution and the ‘transient’ channel, high temporal resolution

The functional status and columnar organization of single cells responding to cutaneous stimulation in neonatal rat somatosensory cortex S1.

Abstract: 1 An investigation was carried out on single cells in 7 day old rat primary somatosensory cortex, which responded to cutaneous stimulation using mechanical pulses 3 percent of cells encountered showed stable spontaneous activity, whereas 88 percent were silent in the absence of intentional stimulation The remainder showed unstable spontaneous activity In contrast, the great majority of adult cells were spontaneously active in the absence of stimulation, under similar conditions of urethane anaesthesia 2 The distribution within cortical layers of cutaneously driven cells was similar in adult and 7 day old rats, and similar to that found in adult mammalian cortex by other workers 3 7 day old cells showed diminished excitability to cutaneous stimulation with stimuli at intervals below 10-15 sec, whereas adult cells could be successfully repetitively driven with stimuli at intervals of 500 msec The low ability of the immature cells to follow repetitive cutaneous stimulation is not due to an overall depression of these cells excitability per se Latencies of unitary responses in these immature cells were about sixfold those found in equivalent cells at maturity 4 Columnar organization at seven days of age was similar in outline to that of the adult, but much less discrete Receptive fields were considerably larger at 7 days and evidence is given that this may be due to inadequate surround inhibition Immature vibrissae-driven units were directionally selective 5 At 7 days of age, long inter-spike intervals were rare in spontaneously active cells with the result that inter-spike interval histogram distributions (ihs) were approximately normal Corresponding ihs of adult cells invariably showed skew distributions 6 Tactile stimulation of centre receptive fields produced an increase in short and long intervals from spontaneously active cells at each age In contrast to adult cells, the immature cells commonly responded cyclically, with alternating phases of increased and decreased firing rate for periods of up to 3 sec following punctate stimulation 7 Decrease in spontaneous firing rate, following the first phase of excitation, was profound in 7 day old cells, and implied that inhibitory mechanisms operate at an early age in the rat somatosensory system These mechanisms also appear to contribute to cyclical activity of 7 day old cells when driven by punctate cutaneous stimulation

Visual receptive fields and their images in superior colliculus of the cat.

Abstract: 1. The receptive fields of collicular neurons in the cat, recorded in a single microelectrode penetration, were not centered on a point in visual space, but nested eccentrically with the smaller fields displaced toward the area centralis. The eccentric nesting was not eliminated by correcting the fields for the tangent screen distortion or by making penetrations normal to the collicular surface in coronal and parasagittal planes. These findings do not support the idea that collicular cells form topographically organized columns oriented normal to the collicular surface. 2. When the receptive fields were plotted in the visual coordinate system of the collicular map, the nesting became much more concentric, suggesting that the eccentric nesting of the receptive fields in visual space was largely a product of the retinotectal coordinate transformation. 3. The profile of a collicular receptive field, plotted in the collicular visual coordinate system is called the receptive-field image. Receptive-field images tended to have oval shapes with the long axis oriented mediolaterally. Clusters of receptive-field images, plotted for single penetrations, appeared similar wherever they occurred in the collicular map, suggesting that a common pattern of neural convergence determines the geometry of the receptive-field images in all parts of the colliculus. 4. The neural substrate of the receptive-field images was examined by tracing the theoretical patterns of neural activity which a point stimulus would produce in the retinotectal system. This analysis suggested that the shape and dimensions of the receptive-field images, and consequently the receptive fields, might be accounted for in large part by the geometry of collicular dendritic fields, the dimensions of the visual receptive fields of afferent fibers, and the retinotectal coordinate transformation. 5. Because it adjusts for the retinotectal distortion of visual space, the receptive-field image may be used to outline the distribution of collicular cells excited by a point stimulus. This makes it possible to show that a point stimulus activates large-field cells in the superficial gray layer over an area of about 2.5 by 1.5 mm in the central parts of the colliculus. It is suggested that such cells may organize the directional signals required by the oculomotor system for visual orienting behavior.

Visual activation of neurons in inferotemporal cortex depends on striate cortex and forebrain commissures.

Abstract: Neurons in inferotemporal cortex respond only to visual stimuli and a majority have receptive fields that extend well into both visual half-fields. After bilateral removal of striate cortex, no inferotemporal neurons responded to visual stimuli. After unilateral removal of striate cortex, inferotemporal neurons in both hemispheres responded only to stimuli in the hemifield contralateral to the intact striate cortex. After section of the corpus callosum and anterior commissure, inferotemporal neurons in both hemispheres responded only to stimuli in the hemifield contralateral to the recording site. These results indicate that inferotemporal cortex visual information from striate cortex and that the pathway from striate cortex to the contralateral inferotemporal cortex includes the forebrain commissures. This same striate-temporal pathway is also necessary for normal discrimination learning. We suggest that the converging input onto single inferotemporal neurons from widely separated retinal areas may provide a mechanism for stimulus equivalence over different parts of the visual field, and it may be the absence of such a mechanism that contributes to the visual discrimination deficit that follows inferotemporal lesions.

Receptive field characteristics and plastic properties of visual cortical cells in kittens reared with or without visual experience.

Abstract: The functional organization of visual cortical cells was studied in two groups of five week old kittens: one group normally reared, the other reared in total darkness from the third day after birth. The following results were obtained: 1. The cells of the normally reared kittens were similar to adult cells except for some aspects of immaturity. In contrast, the cells of the dark-reared kittens were totally non-specific. Their receptive field showed neither orientational nor directional properties. 2. The distribution of cells according to the ocular dominance was not different in either group and was similar to that previously described for ‘adult’ cells. 3. A few hours of visual experience was sufficient to provide specific receptive field properties to the cortical cells of a dark-reared kitten. 4. Conditioning exposure with an oriented grating induced changes in orientational sensitivity in normally reared kittens but not in dark-reared kittens.

Visual receptive-field properties of cells in area 18 of cat's cerebral cortex before and after acute lesions in area 17.

Abstract: 1. Receptive-field properties of single neurons in cat's cortical area 18 were studied before and after partial bilateral lesions of area 17. 2. The majority of cells recorded from animals with int...

Cat parastriate cortex: a primary or secondary visual area

Abstract: The purpose of this study was to determine to what extent the cat parastriate cortex processes afferent geniculate activity in a way similar to that in area 17. The area explored was located on the lateral gyrus between the Horsley-Clarke coordinates A1 to 4 and L3 to 4. The receptive-field properties of area 18 cells and their responses to electrical stimulation of afferent and efferent pathways were measured with the same methods as described previously in area 17. Mutual correlations among these items were calculated and compared with the respective data from area 17. The results of this correlative analysis revealed numerous similarities between the two areas with regard to their afferent and efferent connections and their intrinsic organization. Consequently, the structure of the receptive fields and their numerical distribution resembled those in area 17. The same was true for the correlations between receptive-field parameters and afferent and efferent connectivity. The main differences were that area 18 cells had larger receptive fields and responded to considerably higher stimulus velocities. It is suggest-d that these differences are caused by the fact that area 18 receives subcortical afferents of the Y-type, whereas the dominant input to area 17 comes from the X-system. It is concluded that the area investigated in this study is organized in parallel to area 17 and deals with other aspects of visual information than area 17.

Representation of head and face in postcentral gyrus of the macaque

Abstract: The receptive field and submodality characteristics of individual neurons within the cytoarchitectural and topographic subdivisions of the head and face areas of the postcentral gyrus (SI) were determined with the technique of extracellular recording. Correlation of the single-unit data with the intracortical location of the recording electrode provided a detailed description of the functional organization within each of the several cytoarchitecturally distinct regions contributing to the representation of the head and face in SI. The data indicate that the functional organization of the SI cortex which receives its principal input from trigeminal mechanoreceptors is comparable to the organization within those SI regions which receive their input from the mechanoreceptors of the limbs, trunk, and tail. In each topographic subdivision of the SI cortex 1) a single region in the periphery is represented several times in widely separated locations, each time in a context of different submodalities and peripheral receptive fields; and 2) neurons belonging to the different submodality classes are segregated so that projections from cutaneous afferents terminate mainly in cytoarchitectural area 3 in the adjacent anterior portion of area 1, while projections from the afferents innervating deep tissues terminate mainly in cytoarchitectural area 3a, area 2, and the posterior part of each 1. Although the mechanoreceptor input to SI is segregated according to submodality and the mechanoreceptors from most body regions project to multiple widely separated regions within SI, neurons with receptive fields confined to the ophthalmic division of the trigeminal peripheral innervation field are found within a restricted region of the anterior postcentral gyral crown which is positioned symmetrically about the junction of cytoarchitectural areas 1 and 3. Neurons with receptive fields confined to the maxillary division of the trigeminal innervation field are found within a ring of cortex which a) completely surrounds the representation of the ophthalmic field, and b) includes parts of cytoarchitectural area 2, 1, 3, and 3a. SI neurons with receptive fields restricted to the mandibular division of the trigeminal innervation field occupy the largest portion of the SI face area and form a ring of cortical cell columns which completely surrounds that cortical region which receives its input from the maxillary peripheral innervation field.

Pyramidal tract control over cutaneous and kinesthetic sensory transmission in the cat thalamus.

Abstract: In the thalamic ventrobasal complex (VB) of the cat, effects of electrical stimulation of the pyramidal tract (PT) upon activities of 112 relay cells and 18 internuncial cells were examined Single PT shocks to the cerebral peduncle elicited short-latency discharges in 31 relay cells (mean latency, 14±05 msec) When weak PT stimuli were employed as conditioning shocks, facilitatory effects upon responses to medial lemniscal (ML) stimulation were observed It was revealed that VB relay cells were excited monosynaptically via collaterals of the fast PT fibers Among 31 PT-excited cells 22 were fired by movements of joints (joint-movement units) and they made up 88% of all the joint-movement units A majority of the relay cells responding to stimulation of hairs (hair units) did not receive excitatory effects from PT, except some special ones which represented long hairs at the distal or proximal end of the forearm-forepaw In 44 relay cells repetitive PT shocks suppressed both evoked responses to ML stimulation and spontaneous discharges for 70–100 msec Of these, 34 were hair units The PT-induced inhibition in the hair units increased as their receptive fields shifted from the trunk towards the digits Some intracellular recordings showed that the PT-induced inhibition was due to IPSPs generated disynaptically Among 18 interneurons presumed to be inhibitory 10 responded with short latencies to PT stimulation These were mostly the interneurons which presumably subserve the recurrent collateral inhibition in VB

Reticulospinal neurons with and without monosynaptic inputs from cerebellar nuclei.

Abstract: An account is given of the responses of 557 medial reticular neurons with axons projecting down the spinal cord. All 30 experiments were on decerebrated unanesthetized cats paralyzed by Flaxedil. Recording from single neurons was by extracellular glass microelectrodes. Identification was first by location (confirmed by subsequent histology) in the medial reticular nucleus of medulla or pons, and second by antidromic activation from cord stimulation at C2 and L2 segmental levels. Axonal conduction velocities were calculated from the latency differential between L2 and C2 antidromic responses, and were usually in the range of 90-140 m/s; but about 25% were slower, ranging down to 30 m/s. Stimulation by electrodes in the ipsilateral and contralateral fastigial nuclei differentiated reticulospinal neurons into two classes according to whether they did or did not receive monosynaptic inputs, the respective populations of fully investigated neurons being 270 and 174. The fastigioreticular neurons were distinguished by a higher background frequency with mean values of 28 as against 15/s. There were also significant diffences in both the excitatory and inhibitory responses to afferent volleys from forelimb and hindlimb nerves. Comparison of the respective latency histograms showed that the responses of neurons with a fastigial input had an excess of latencies in the ranges that can be correlated with the latency histograms observed for fastigial responses. Thus, there is evidence for the effectiveness of the fastigial input and so for the pathway with monosynaptic linkage: Purkinje cells of cerebellar vermis yields fastigial neurons yields medial reticular neurons projecting down the spinal cord. Adequate stimulation of cutaneous receptors by pad taps and air-jet stimulation of hairy skin in a disppointingly small action when compared with fastigical responses. Explanations of this deficiency are suggested. Another discrpancy from the fastigial responses is that the medial reticular neurons have much wider receptive fields with little discrimination between ipsilateral and contralateral and between forelimb and hindlimb. Stimulation of the ipsilateral tegmental tract was tested on 183 reticulospinal neurons, 112 being with fastigial inputs. In about half there was a powerful monosynaptic excitation, which would identify such neurons as being on the pathway from mesencephalic and diencephalic centers to the spinal cord. There is a general discussion of transmission across successive synaptic relays, where specificity is sacrificed to integration.

Differential responses of cat visual cortical cells to textured stimuli

Abstract: The responsiveness of primary visual cortical units to luminance edges or bars (Hubel and Wiesel, 1962) has encouraged the belief that they may serve as the elementary edgeor bar-'detectors' in a hierarchic pattern-recognition process. One possible objection to this view is that patterns can readily be reeognised when presented against a background of the same average luminance but different texture. Even an area of static visual 'noise' identieM in texture to its background, which is completely camouflaged when at rest, has its contours instantly recognizable if moved relative to the background. I t might be felt that this objection would be answered if the same units proved sensitive to such 'kinetic contours' as well as to contours of luminance.

Periodic excitability changes across the receptive fields of complex cells in the striate and parastriate cortex of the cat.

Abstract: 1. Complex cells in cortical areas 17 and 18 of the cat have been studied in response to narrow slits and edges moving across the receptive field in the preferred direction and also to stationary slits of different widths. 2. Average response histograms, recorded as a narrow slit was moved across the receptive field, displayed a periodic series of peaks above a base line level. The response histogram for most area 17 and 18 cells contained five principal peaks; sometimes one or two weaker peaks were present at receptive field borders. The histogram for one cell located at the area 17-18 border showed thirteen distinct peaks. Periodic response patterns were also generated as an extended edge was moved across the receptive field. Plots of cell responses versus slit width for stationary slits of different widths also indicated periodic response pattern. 3. The accuracy of determining the preferred slit orientation was the single most important requirement for demonstrating the periodic response pattern. Significant changes in the appearance of the periodic pattern occurred even upon 5 degrees rotations away from the preferred orientation. 4. Average response histograms were also studied over a wide range of moving slit velocities. The number of peaks across corresponding spacings within the recewptive field remained constant over a range of velocities. Response amplitudes, however, were velocity dependent. Thus the response peaks remain associated with fixed positions within visual space independent of stimulus velocity, even though temporal as well as spatial factors may be involved in response selectivity and the periodic modulation. The most striking periodic response histograms were generated at the velocities which produced the greatest cell firing rates. Area 17 complex cells responded well to velocities of less than 0-5 degrees to 6-0 degrees/sec, but cells in area 18 generally required higher velocities, sometimes as high as 20 degrees--30 degrees/sec, for a good response. 5. Spatial frequencies for the periodic component of the receptive field for area 17 cells in the central visual area covered a range of three octaves up to 5 cycles/degree, and area 18 cells included another octave on the low frequency side. The spatial frequency of a cell was found to be roughly inversely proportional to the receptive field width. Only a small sample of area 18 cells was studied, but these cells tended to represent low spatial frequencies and to respond selectively to high velocity stimuli...