Showing papers on "Receptive field published in 1977"

Ferrier Lecture: Functional Architecture of Macaque Monkey Visual Cortex

Abstract: Of the many possible functions of the macaque monkey primary visual cortex (striate cortex, area 17) two are now fairly well understood. First, the incoming information from the lateral geniculate bodies is rearranged so that most cells in the striate cortex respond to specifically oriented line segments, and, second, information originating from the two eyes converges upon single cells. The rearrangement and convergence do not take place immediately, however: in layer IVc, where the bulk of the afferents terminate, virtually all cells have fields with circular symmetry and are strictly monocular, driven from the left eye or from the right, but not both; at subsequent stages, in layers above and below IVc, most cells show orientation specificity, and about half are binocular. In a binocular cell the receptive fields in the two eyes are on corresponding regions in the two retinas and are identical in structure, but one eye is usually more effective than the other in influencing the cell; all shades of ocular dominance are seen. These two functions are strongly reflected in the architecture of the cortex, in that cells with common physiological properties are grouped together in vertically organized systems of columns. In an ocular dominance column all cells respond preferentially to the same eye. By four independent anatomical methods it has been shown that these columns have the from of vertically disposed alternating left-eye and right-eye slabs, which in horizontal section form alternating stripes about 400 $\mu $m thick, with occasional bifurcations and blind endings. Cells of like orientation specificity are known from physiological recordings to be similarly grouped in much narrower vertical sheeet-like aggregations, stacked in orderly sequences so that on traversing the cortex tangentially one normally encounters a succession of small shifts in orientation, clockwise or counterclockwise; a 1 mm traverse is usually accompanied by one or several full rotations through 180 degrees, broken at times by reversals in direction of rotation and occasionally by large abrupt shifts. A full complement of columns, of either type, left-plus-right eye or a complete 180 degrees sequence, is termed a hypercolumn. Columns (and hence hypercolumns) have roughly the same width throughout the binocular part of the cortex. The two independent systems of hypercolumns are engrafted upon the well known topographic representation of the visual field. The receptive fields mapped in a vertical penetration through cortex show a scatter in position roughly equal to the average size of the fields themselves, and the area thus covered, the aggregate receptive field, increases with distance from the fovea. A parallel increase is seen in reciprocal magnification (the number of degrees of visual field corresponding to 1 mm of cortex). Over most or all of the striate cortex a movement of 1-2 mm, traversing several hypercolumns, is accompanied by a movement through the visual field about equal in size to the local aggregate receptive field. Thus any 1-2 mm block of cortex contains roughly the machinery needed to subserve an aggregate receptive field. In the cortex the fall-off in detail with which the visual field is analysed, as one moves out from the foveal area, is accompanied not by a reduction in thickness of layers, as is found in the retina, but by a reduction in the area of cortex (and hence the number of columnar units) devoted to a given amount of visual field: unlike the retina, the striate cortex is virtually uniform morphologically but varies in magnification. In most respects the above description fits the newborn monkey just as well as the adult, suggesting that area 17 is largely genetically programmed. The ocular dominance columns, however, are not fully developed at birth, since the geniculate terminals belonging to one eye occupy layer IVc throughout its length, segregating out into separate columns only after about the first 6 weeks, whether or not the animal has visual experience. If one eye is sutured closed during this early period the columns belonging to that eye become shrunken and their companions correspondingly expanded. This would seem to be at least in part the result of interference with normal maturation, though sprouting and retraction of axon terminals are not excluded.

Laminar differences in receptive field properties of cells in cat primary visual cortex

Abstract: 1. Cells in area 17 of the cat visual cortex were studied with a view towards correlating receptive field properties with layering. A number of receptive field parameters were measured for all units, and nearly every unit was marked with a microlesion to determine accurately the layer in which it was found. 2. Cells were defined as simple or complex by mapping with stationary stimuli, using the criteria of Hubel & Wiesel (1962). Complex cells fell into two groups: those that showed summation for increased slit length (standard complex) and those that did not (special complex). 3. The simple cells were located in the deep part of layer 3, in layer 4, and in layer 6. This corresponds to the distribution of afferents from the dorsal layers of the lateral geniculate nucleus. In these cortical layers the simple cells differed primarily with respect to their receptive field size, cells in layer 4 having the smallest, layer 3 intermediate, and layer 6 the largest fields. Layer 4 was the only layer in which simple cells showed end-inhibition (a reduction in response to slits extending beyond the excitatory portion of the receptive field). 4. The standard complex cells were found in all layers, but were quite scarce in layer 4. As with the simple cells, field size varied with layer: in layer 2+3 they had small to intermediate field sizes, in layer 5 intermediate, and in layer 6 very large. Layer 6 cells showed summation for slits of increased length up to very large values, and responded best when the slits were centred in the receptive field. The only standard complex cells that showed end-inhibition were those in layer 2+3, and these were similar to the layer 4 simple cells in terms of proportion of end-inhibited units and degree of end-inhibition. 5. The special complex cells, originally described by Palmer & Rosenquist (1974), were found in two tiers: the upper one at the layer 3/layer 4 border and the lower one in layer 5. They were different from the standard complex cells in having a high spontaneous activity, high velocity preference, and large fields which were similar in size (at a given eccentricity) from one cell to the next. Many showed reduced response to slits of increasing length, even for slits that did not extend beyond the borders of the responsive region. 6. Cells in layer 6 (the origin of the corticogeniculate projection) were antidromically activated from the lateral geniculate nucleus. The antidromically activated units included both simple and complex cells, and they had the long receptive fields characteristic of the overall population of cells in layer 6. 7. The results showed that there are different types of simple and complex cells, and that cells in different layers have different properties. Taken together with their differences in site of projection, this demonstrates that the anatomical lamination pattern is reflected in functional differences between cells in different layers.

Spatial mapping in the primate sensory projection: Analytic structure and relevance to perception

Abstract: The retinotopic mapping of the visual field to the surface of the striate cortex is characterized as a longarithmic conformal mapping. This summarizes in a concise way the observed curve of cortical magnification, the linear scaling of receptive field size with eccentricity, and the mapping of global visual field landmarks. It is shown that if this global structure is reiterated at the local level, then the sequence regularity of the simple cells of area 17 may be accounted for as well. Recently published data on the secondary visual area, the medial visual area, and the inferior pulvinar of the owl monkey suggests that same global logarithmic structure holds for these areas as well. The available data on the structure of the somatotopic mapping (areaS-1) supports a similar analysis. The possible relevance of the analytical form of the cortical receptotopic maps to perception is examined and a brief discussion of the developmental implications of these findings is presented.

Inhibitory processes underlying the directional specificity of simple, complex and hypercomplex cells in the cat's visual cortex

Abstract: 1. The iontophoretic application of bicuculline, an antagonist of GABA, the putative inhibitory transmitter in the visual cortex, has been used to examine the contribution of post-synaptic inhibitory processes to the directional selectivity of simple, complex and hypercomplex cells in the cat's striate cortex. 2. The directional selectivity of simple cells was significantly reduced or eliminated during the iontophoretic application of bicuculline. This supports the view that the selectivity is derived from the action of a GABA-mediated post-synaptic inhibitory input modifying their response to a non-directionally specific excitatory input. 3. Complex cells were subdivided into three categories on the basis of the action of iontophoretically applied bicuculline on their directional selectivity, receptive field characteristics and distribution in terms of cortical layer. They are referred to as type ‘1’, ‘2’ and ‘3’ complex cells. 4. The directional specificity of type ‘1’ complex cells was eliminated during the iontophoretic application of bicuculline. It seems likely, therefore, that they receive a non-directionally specific excitatory input and that, as for simple cells, the directional specificity derives from the action of a GABA-mediated post-synaptic inhibitory input. No type ‘1’ complex cells were recorded below layer IV. 5. The directional specificity of type ‘2’ complex cells was unaffected by the iontophoretic application of bicuculline, despite increases in response magnitude, a block of the action of iontophoretically applied GABA and, in some cases, changes in other receptive field properties. It is suggested that these cells receive a directionally specific excitatory input. The type ‘2’ complex cells were found both superficial and deep to layer IV with the majority in layer V. 6. Type ‘3’ complex cells appear to have very similar receptive field properties to those of the cells described by other workers as projecting to the superior colliculus. They were found predominantly in layer V. Their directional specificity was not eliminated by the iontophoretic application of bicuculline. However, they exhibited a powerful suppression of the resting discharge in response to stimulus motion in the non-preferred direction. Iontophoretic application of ammonium ions revealed a small excitatory response in place of the suppression. It appears from these observations that the directional specificity of the type ‘3’ complex cells could be determined, at least in part, by an inhibitory process which is not GABA-mediated. 7. The directional specificity of hypercomplex cells found in layers II and III was unaffected by the iontophoretic application of bicuculline, and they showed no suppression of their background discharge level in response to stimulus motion in the non-preferred direction. This evidence is consistent with the view that they receive a directionally specific excitatory input.

Cat cones have rod input: A comparison of the response properties of cones and horizontal cell bodies in the retina of the cat

Abstract: The responses of horizontal cell bodies and cones in the retina of the cat have been studied by means of intracellular recording and Procion dye injection in an isolated, arterially perfused eyecup preparation. Comparison of the hyperpolarizing responses of these units to red and blue stimuli of different intensities indicated that all morphological varieties of horizontal cells and, additionally, cones themselves, had mixed rod and cone input. The rod input into horizontal cell bodies is thus explained on the basis of cone physiology. The half-saturating intensity of 441 nm stimuli for the rod input into cones and horizontal cells was about 400 quanta/mum2/sec and about 160,000 quanta/mum2/sec for the cone input. Little of this difference can be related to the different quantum catching abilities of rods and cones. The spatial properties of horizontal cell bodies and cones have been characterized using stimuli consisting of long slits in conjunction with a continuous cable model. Space constants for horizontal cells ranged from 210 mum to 410 mum, whereas those for cones ranged from 50 mum, or possibly less, to 180 mum. It is argued that horizontal cell bodies of the cat retina form electrical networks, and that the sizes of the receptive fields generated in these networks may be limited by the diameters of the primary and secondary dendrites of horizontal cells. The rod and cone fields of horizontal cell bodies were found to be nearly coextensive in space, arguing against the notion that substantial rod input came from distant, rod-dominated terminal arborizations.

Organization of visual inputs to interneurons of lateral geniculate nucleus of the cat

Abstract: 1. Two groups of interneurons that are involved in the organization of the lateral geniculate nucleus (LGN) are described. The cell bodies of one group lie within the LGN; these units are referred to as intrageniculate. The cell bodies of the other group are found immediately above the LGN at its border with the perigeniculate nucleus; these units are referred to as perigeniculate. 2. Intrageniculate interneurons have center-surround receptive fields that resemble those of relay (principal) cells. They can be subdivided into brisk or sluggish and sustained or transient categories. They are stimulated transsynaptically from the visual cortex and have a characteristic variation in the latency of their spike response to such stimulation both at threshold and for suprathreshold stimuli. The pathway for this stimulation appears to be via cortical efferents to the LGN. Intrageniculate interneurons receive direct, monosynaptic retinal inputs, as determined by recording simultaneously from such interneurons and from the ganglion cells which provide excitatory input to them. Similar to relay cells, they are shown to have one or two major ganglion cell inputs. 3. Perigeniculate interneurons are generally binocularly innervated and give on-off responses to small spot stimuli throughout their receptive field. They respond well to rapid movement of large targets. They respond to electrical stimulation of the retina with a spike latency that falls between that of brisk transient and brisk sustained relay cells. This latency is one synaptic delay longer than that of brisk transient relay cell activation and suggests that they are excited by axon collaterals of these relay cells. Electrical stimulation of the visual cortex is also consistent with this model; the latency of the response of perigeniculate interneurons is approximately one synaptic delay longer than the latency of the response of brisk transient relay cells. 4. The interneuronal pathways described are consistent with proposed circuits that subserve the generation of IPSPs that arise in response to optic nerve and visual cortical stimulation. We now show that such inhibition has feed-forward (intrageniculate) and feed-back (perigeniculate) components that are mediated by two different classes of geniculate interneurons. It is suggested that the intrageniculate interneurons are involved in precise, spatially organized inhibition and that the perigeniculate interneurons are part of a more general, diffuse inhibitory system that modulates LGN excitability.

The neural representation of visual space

Abstract: THE approximate form of the projection of visual space on the striate cortex in man has long been established from neurological evidence1–3 and estimates of cortical magnification M (the extent of striate cortex in millimetres corresponding to a degree of arc in visual space) have been derived from studies on cortical phosphenes and visual acuity4, and migraine scotoma dimensions5. The possibility that M could be estimated from the density of retinal ganglion cells which provide the output from the eye to the brain has received support from studies on monkeys6–8. It has been shown that M is proportional to √Dc (where Dc is the projected ganglion cell density in cells per solid degree of visual space) for peripheral angles (θ) greater than 10°. More centrally, where Dc is maximal, this relationship breaks down because the cells are displaced from their receptive fields by an amount which is difficult to determine8. If data on ganglion cell receptive field density, Dr (in receptive fields per solid degree) were available, they might be expected to relate to M at every point in the visual field. I report here that I have obtained such estimates of Dr and examined their usefulness as predictors of M. The results are summarised in three basic equations.

Colour Coding in the Superior Temporal Sulcus of Rhesus Monkey Visual Cortex

Abstract: In the rhesus monkey, the posterior bank of the superior temporal sulcus forms part of the prestriate visual cortex and has two regions, a medial one and a lateral one, which have their own separate callosal connections. The afferent input to these two regions was studied in experiments where the corpus callosum was sectioned, and labelled amino acids were injected into other visual areas. By this method, it was found that area 17 projects to that part of the superior temporal sulcus occupied by the more medial of the two callosal inputs. By contrast, the part of the sulcus occupied by the more lateral callosal input was found to receive a strong projection from the fourth visual complex, an area rich in colour-coded cells. Recordings were made from single cells in the superior temporal sulcus in animals in which the corpus callosum had been sectioned previously. The degeneration produced by this procedure was used to provide anatomical landmarks enabling us to assign cells to the lateral or the medial regions of the sulcus. Such recordings revealed that receptive fields were topographically organized in the lateral part of the sulcus and that most cells were colour specific. By contrast, cells recorded from in the region of the more medial callosal patch within this sulcus were directionally selective, without any obvious colour coding. It was concluded from these combined anatomico-physiological experiments that there are at least two distinct regions in the superior temporal sulcus which have different afferent connections and functional properties.

Maturation of function in the developing rabbit retina.

Abstract: Retinas isolated from rabbits aged less than eight hours to adult were maintained in a flowing physiological medium. The electroretinogram or activity of single ganglion cells were recorded, and receptive fields were studied using stimulation of the retina with focused light. Retinal activity was stable for at least eight hours of incubation. Retinal ganglion cells are electrophysiologically active on the first day of life. They generate spontaneous bursts of action potentials at rates of 10 to 30 spikes/ sec, separated by silent intervals of one to six minutes. Maintained trains of action potentials follow elevation of the concentration of K+ in the incubating medium to 10 mM. Ganglion cells are also stimulated by acetylcholine, with apparent threshols equal to or lower than those of ganglion cells in adult retinas. The first response of the retina to light is a small cornea-negative transretinal potential at day 6, presumably PIII of the electroretinogram. Responses of the ganglion cells are seen at eight days, but the responses are weak and adapt quickly to repeated stimulation. Many unresponsive cells are present. By ten days 60% of ganglion cells respond to light, and examples of mature receptive fields are present. Immature receptive fields at ten days fall into two rough classes, one characterized by a large responsive area with no antagonistic surround, and a second in which the surround can suppress the response to illumination of the center but can not itself cause a discharge. Immature fields are progressively replaced by mature ones, and by 20 days the qualitative organization of receptive fields is indistinguishable from adult.

The organization of thalamocortical relay neurons in the rat ventrobasal complex studied by the retrograde transport of horseradish peroxidase

Abstract: The organization of thalamocortical relay neurons in the thalamic ventrobasal complex (VB) of the rat was investigated by the use of the retrograde axonal transport of horseradish peroxidase (HRP). Injections of HRP into somatosensory cortex (SI) resulted in a distinctive gradient of neuronal and non-neuronal HRP reaction product. Electrophysiologically characterized points of SI injected with small volumes of HRP labeled a sector of neurons in VB ipsilateral to the injection. This zone of labeled neurons consisted of a complex curvilinear array or lamina with a rostral hollow or solid expansion of densely packed HRP positive neurons which continues caudally as a less dense tapering wing. Despite this complex arrangement, an approximate pattern of somatotopy was determined indicating the direction of shifts in peripheral receptive fields moving in any axis of VB. The number of labeled neurons projecting upon a point in SI was also determined. Injections of the cortical vibrissae, face and forepaw representations labeled a greater number of neurons in VB per unit area of cortex than did injections in the hindlimb or body representations. The total number of HRP positive neurons in VB increased proportionately with areal increase of the HRP injections into overlapping cortical representations. The number of HRP positive neurons in the rostral half of the laminae increased almost linearly with the area of injection, while the number of HRP positive neurons in the caudal half of the laminae showed relatively smaller increases.

Functional organization of catfish retina

Abstract: 1. The basic organization of the biphasic (or concentric) receptive field is established in the bipolar cells as the result of an interaction between two signals, one local representing the activity of a small number of receptors, and the other integrating (19, 20) or global (28) coming from the S space or a lamina formed by the horizontal cells (8, 14, 22, 29). 2. Bipolar-ganglion cell pairs are segregated into two types; A (on center) and B (off center) pairs. A depolarization of a bipolar cell produces spike discharges from ganglion cells of the same type and a hyperpolarization depresses their discharges. I haven9t detected any cross talk between the types A and B pairs. Bipolar and ganglion cells must be interfaced by the classical chemical synapses, the only such kind in the catfish retina. 3. Horizontal and type N neurons form two lateral transmission systems, one distal and the other proximal (19, 20). Signals in the lateral systems are shared by the two receptive-field types and are not excitatory or inhibitory in themselves; it is incumbent upon the postsynaptic neurons to decide the polarity of the synaptic transmission. The horizontal cell participates directly in the formation of biphasic receptive fields of bipolar cells by providing their surrounding, whereas type N neuron seems to modify the receptive-field organization established in the bipolar cells. 4. Type N neurons are amacrine cells because they do not produce spike discharges (2, 18, 21) and because they influence the activity of both A and B receptive fields. 5. The function of the type C neuron is as unique as its structure (21) and is not fully clear as yet. It is not a conventional amacrine cell as the type N appears to be, nor is it a classical ganglion cell which forms either a type A or B receptive field (2). 6. Type Y neurons are a class of ganglion cells which forms either a type A or B receptive field.

Demonstration of bilateral projection of the central retina of the monkey with horseradish peroxidase neuronography.

Abstract: In the primate, ganglion cells of the temporal retina project ipsilaterally and those of the nasal retina, contralaterally into the optic tract. The vertical meridian passing through the fovea defines the border between these two populations of ganglion cells and has been demonstrated in four Macaque monkeys after unilateral injection of horseradish peroxidase into the dorsal lateral geniculate nucleus and examination of the pattern of retrograde labeling of those ganglion cells projecting to the injected side. A median 1 degree vertical strip in which ipsi- and contralaterally projecting ganglion cells intermingle was found, confirming the report by Stone et al. ('73). In addition, occasional extrafoveal labeled ganglion cells were found as far as 2 degrees from the vertical midline in the otherwise unlabeled hemiretinae. These ganglion cells were not numerous and had somata of all sizes, suggesting that they do not constitute a separate class of ganglion cells as found in the temporal retina of the cat. In contrast to the description by Stone et al. ('73), the strip of vertical overlap did not show a constant width through the fovea, since mixing of labeled and unlabeled ganglion cells was found in a band approximately 1/2 degree wide along both the nasal and temporal rims of the foveal pit which is 500 mum (2 degrees) in diameter. Beyond these 1/2 degree arcs, the appropriate hemiretina was either completely unlabeled, or contained virtually every ganglion cell labeled on the side projecting to the injected dorsal lateral geniculate nucleus. The scattered labeled ganglion cells rimming an otherwise unlabeled hemifovea represent a possible anatomical basis for the phenomenon of "macular" or "foveal sparing" in which unilateral damage to the occipital cortex produces homonymous hemianopsia with sparing of a small island of centralmost vision extending about 1 degree from the foveal center. From this study, it is not possible to define the receptive fields or specific photoreceptor connections of the ganglion cells labeled with horseradish peroxidase, so that at the present time quantitative correlations cannot be made between the numbers of ganglion cells remaining on the affected side of the fovea and the extent of preservation of visual function in the spared zone. The presence of labeled ganglion cells rimming the fovea in its entirety is compatible with the sequence of foveal development in late prenatal life. After lateral displacement both nasally and temporally of ganglion cells which initially lay in the median vertical overlap strip of 1 degree, in the adult retina a strip approximately 1/2 degree wide around the perimeter of the foveola should contain a mixture of ipsi- and contralaterally projecting ganglion cells. The total population of ganglion cells beyond this 1/2 degree band should be completely ipsi- or contralateral in their projection patterns, as is observed...

Some visual and other connections to the cerebellum of the pigeon.

Abstract: By anatomical techniques it has been shown that folia VIc-IXc of the pigeon cerebellum receive inputs from the following groups of neurons: the medial and lateral pontine nuclei, the superficial synencephalic nucleus, the medial spiriform nucleus, the inferior olive, and the deep cerebellar nuclei. From all but the last of these, the projection is mainly crossed, though the uncrossed component from the lateral pontine nucleus is not insubstantial. The input from the superficial synencephalic nucleus provides a direct pathway from the retina to the cerebellum (folia VIc, VII, VIII and IXc). Less direct visual pathways reach the cerebellum via the following routes: (i) the superficial synencephalic nucleus projects ipsilaterally to the lateral pontine nucleus and sparsely to the inferior olive; (ii) the tectum projects ipsilaterally to the lateral and medial pontine nuclei, though the latter connection is sparse. In electrophysiological experiments, the importance of the tecto-pontine component of the projection has been demonstrated by cooling the tectum while recording visual responses from the cerebellum. The visual receptive fields of pontine cells have been analysed. They vary in extent from 10 degrees to the whole monocular field. They respond best to moving targets, preferring speeds of 20 to 60 degrees/second, and are usually direction-selective.

Visual responses of area 18 neurons in awake, behaving monkey.

Abstract: : The mechanisms underlying effects of ionizing radiation on visual-motor tasks in combat are not understood but definitely involve some disruption of visual perception. The degree of involvement is not known and must be studied and quantified in animal models. It is possible to identify those parts of the central nervous system necessary for visual perception. Once these areas have been identified, their sensitivity to irradiation can be studied more precisely. Visual responses of area 18 neurons were studied in the awake, behaving monkey. Cells were divided into six different classes on the basis of their stimulus preferences and spatial characteristics. Orientation cells were sensitive to the orientation of elongated stimuli. Color cells had nonoriented receptive fields with spatially coextensive opponent color inputs. Direction cells preferred moving stimuli, giving the greatest response to movement in some direction and no response or inhibition to movement in the opposite direction. Spot cells preferred a properly positioned small spot of light and responded equally well to all directions of stimulus movement. Border cells responded best to a stimulus that filled an excitatory region without encroaching on a powerful suppressive flank. Lightinhibited cells had high maintained spontaneous activity that was reduced or abolished by light.

Responses of single units in cat visual cortex to moving bars of light as a function of bar length.

Abstract: 1. The responses of single units in the cat's primary visual cortex to moving bars have been examined quantitatively as a function of bar length.2. For about half the cells studied, very long bars evoked weaker responses than short bars, implying that there were inhibitory regions flanking the receptive field centre. In another quarter of the cell sample, there was evidence of flanking regions which were facilitatory in effect.3. The strength of the flanking regions was found to vary from cell to cell and there was no sudden transition between cells which were ;hyper-complex' and those which were not.4. Within the central region of the receptive field, the responses of most (but not all) cells increased with bar length. About half the cells responded to very short bars or spots of light, but about one in six would not respond at all to short bars.5. Correlations were sought between the properties of cells as simple or complex, their responsiveness to moving spots of light, the size of their receptive field centre and the polarity, strength and size of their receptive field flanks. Simple and complex cells with small receptive fields were more likely to respond well to spots, and to have strong inhibitory flanks.6. Correlations were also sought between the above properties and several other parameters of cell behaviour. Cells with strong inhibitory flanks were found to be more broadly tuned for orientation. Individual cells were also more broadly tuned for the orientation of short bars than of long bars.7. Evidence was obtained that spatial summation can be linear or non-linear for different cells.

Responses and receptive-field organization of cones in perch retinas

Abstract: 1. Cones in the retinas of two closely related species of perch, the walleye and sauger (S, vitreum vitreum and S. canadense), are remarkably large. This paper reports a first series of intracellular recordings obtained from 77 of these cones. 2. A small spot of light evokes a sustained hyperpolarizing response from perch cones which may exceed 10 mV in amplitude, is graded with stimulus intensity, and is markedly reduced when the spot is decentered. Most cones seem to be orange sensitive with peak sensitivity at about 600 nm. 3. Enlarging the stimulus diameter from 0.04 to 0.25 mm produces a modest increase in the hyperpolarizing response. However, larger stimuli which illuminate surrounding regions of the retina often evoke a delayed depolarizing potential which antagonizes the sustained phase of the cone's hyperpolarizing response to central illumination. 4. The outer diameter of the region of the antagonistic surround is at least 2.2 mm in extent. An annulus evokes a depolarizing response only if the central region of the receptive field is simultaneously activated. 5. The present results provide the first direct evidence that the receptive fields of cones in fish retinas have an antagonistic center-surround organization. Luminosity-type horizontal cells probably serve as the interneurons which mediate the depolarizing influence of the surround.

Visual and presaccadic neuronal activity in thalamic internal medullary lamina of cat: a study of targeting.

Abstract: 1 Visual responses and eye movement-related activities were studied in single neurons of the thalamic internal medullary lamina (IML) of alert cats The animals faced a tangent screen on which stationary or moving spots of light were presented Of 95 units, 26% discharged in relation to photic stimuli but not eye movement, 6% in relation to eye movement but not photic stimuli, and 68% in relation to both These units were intermixed in the same region 2 Visual responses varied from transient to sustained IML units were not found particularly sensitive to stimulus movement when the eyes were fixed Strong and consistent responses could be elicited by extremely dim and weakly contrasted stationary stimuli (eg) 34 mcd/m2, 26% of illumination background) binocularly viewed Receptive fields (from 250 to 800 deg2) were determined, in absence of eye movements, by computing the position of effective stimuli relative to the point of fixation of the gaze An area of greatest responsiveness in the receptive field of most units could be detected on the basis of either higher probability of response, minimum latency, greater number of spikes in initial transient burst, or stronger sustained activity Whole fields or their areas of greatest responsiveness were located on the side toward which saccades were accompanied by increased firing of the unit 3 On trials in which a delay occurred between stimulus presentation and the cat's targeting saccade, the majority of the units studied changed their activity twice: after the stimulus and before the eye movement In 16 units, the presaccadic activation occurred only with targeting, not with spontaneous saccades 4 These results suggest that cells in the IML region of the cat play a significant role in the control of visually elicited eye movements The resemblance of these cells to the monkey's tectual cells is discussed and hypotheses are proposed a) to relate the receptive field characteristics to the targeting operation, and b) to account for the double activation--sensory and motor--of many IML cells

Differential effects of early monocular deprivation on binocular and monocular segments of cat striate cortex

Abstract: 1. Receptive-field properties were studied for 156 cells in 15 mqnocularly deprived cats. Particular emphasis was placed on comparisons between receptive fields located in the deprived monocular segment (i.e., far from the vertical meridian) and more centrally located fields. 2. Between 0” and 30’ of visual-field eccentricity from the vertical meridian, 36 of 37 cells were influenced, both for the excitatory and inhibitory components, exclusively by the nondeprived eye. Also, se.veral of these cells had abnormal receptive-field properties. At eccentricities greater than 30”, we found 40 cells which responded to stimuli presented to the deprived eye; of these, 4 were influenced binocularly. An additional 43 cells with fields between 30’ and 45’ eccentricity responded only to stimulation of the nondeprived eye, and 17 cells were studied in the nondeprived monocular segment. About one-third of the cells influenced by the deprived eye had abnormal fields. At least 18 other cells did not respond to any visual stimulus presented to either eye. 3. While the cortical monocular segment related to the nondeprived eye had normal percentages of cell types, the deprived monocular segment had a significant reduction in the ratio of normal complex to normal simple cells. Simple cells in the deprived monocular segment appeared to be normal in every respect we measured. 4. No gross anatomical changes were found which might account for this complex cell loss. That is, we found no differences in cell size or packing density between the deprived and nondeprived monocular segments, 5. The following conclusions were drawn from these results: a) in agreement with previous studies, these data suggest that binocular com-

Convergence of rod and cone signals in the cat's retina.

Abstract: 1. In an attempt to understand the convergence of rod and cone signals in the cat's retina, ganglion cells that received inputs from both rods and cones were stimulated using lights chosen to excite one or other receptor system or both together. 2. If a mesopic background was chosen to allow the ganglion cell to be excited by a blue-green test flash primarily through rods and a deep red flash primarily through cones, one light could not be alternated with the other without eliciting a response from the cell. 3. This appears to be a result of the different temporal properties of the scotopic and photopic systems. On the mesopic background responses to blue-green test flashes were transient. Responses to red test flashes arose with similar latency, but were more sustained. 4. Rod and cone systems responded with similar latencies in the presence of the mesopic background that substantially light-adapted the rod system but left the full sensitivity of the cone system undiminished. When equivalently light-adapted, the cone system was faster. 5. When brief flashes that acted through rods were presented with flashes that acted through cones the ganglion cell's response was the sum of the responses to the two flashes presented separately, as long as the flashes were weak. This linear relation ceased to hold when flashes were strong, but the breakdown appears not to be the result of mutual inhibition between rod and cone signals. 6. When a background light excited both rod and cone systems it appeared to reduce sensitivity independently in each. 7. The scotopic and photopic receptive fields of a given ganglion cell always were of the same type, on- or off-centre, and, within the limits of measurement, the central regions of the receptive fields were concentric and both the same size.

Effects of early experience upon orientation sensitivity and binocularity of neurons in visual cortex of cats.

Abstract: The class of neurons within the visual cortex of normal adult cats that has the smallest receptive fields (less than or equal to 2.25 degrees2) and that responds only to low rates of stimulus motion (less than or equal to 50 degrees / sec) responds preferentially to lines oriented about either the horizontal axis (+/-22.5 degrees) or the vertical axis (+/-22.5 degrees). In animals reared without exposure to patterned visual stimulation, many of these cells display orientation preferences but are activated monocularly. In contrast, in normal animals, neurons that have larger receptive fields or that respond to higher rates of stimulus motion do not exhibit a similar bias in the distribution of their orientation preferences. Cells of this type, studied in animals reared without exposure to patterned visual stimuli, are activated binocularly but do not display orientation preferences.

The effects of remote retinal stimulation on the responses of cat retinal ganglion cells.

Abstract: 1. Action potentials were recorded from optic nerve fibres of lightly anaesthetized cats while parts of the retina remote from the receptive field were stimulated by a shifting grating. 2. Vigorous responses can be obtained under these conditions, confirming McIlwain (1966), Kruger & Fischer (1973), and others. 3. These 'shift responses' are not caused by fluctuations of stray light because (a) they cannot be reduced by deliberately increasing or decreasing the light falling on the receptive field synchronously with the shifting grating; (b) a steady adapting light applied to the receptive field does not raise the threshold for the responses, whereas adapting light on the peripheral retina does, and (c) the threshold for the responses is elevated more following bleaching adaptation of the periphery than following bleaching adaptation of the centre. 4. Shift responses are strong, of short latency, and brief in duration in brisk-transient (Y-type) neurones. With few exceptions they are weak but long-lasting in brisk-sustained (X-type) neurones. 5. Shift responses are unlike responses from the main receptive field in having a distinct threshold; the magnitude of the response to weak gratings is not simply proportional to contrast, as is the case with weak stimuli applied to the receptive field. 6. It is thought that the excitatory pathway may involve amacrine cells, and that this mechanism may be concerned with the detection of the shifts of the image that occur with saccadic eye movements.

Visual receptive-field properties of single neurons in cat's ventral lateral geniculate nucleus.

Abstract: 1. Visual receptive-field characteristics were determined for 154 cells in the ventral lateral geniculate nucleus (VLG) of cats anesthetized with nitrous oxide. All cells were verified histological...

Sensory fibres in ventral roots L7 and S1 in the cat

Abstract: 1. Receptive fields were determined for ninety-eight unmyelinated and 132 myelinated axons in the L7 and S1 cat ventral roots. 2. Seventy of the ninety-eight unmyelinated axons had their receptive fields in somatic structures, the skin and deep tissues. 3. Of the seventy unmyelinated axons with somatic receptive fields, thirty-five were mechanical nociceptors, fifteen were mechanical and thermal nociceptors, eleven were deep nociceptors, six were thermal receptors, and three were low threshold mechanoceptors. 4. Twenty-four of the ninety-eight unmyelinated axons had their receptive fields in visceral structures: the intestine, bladder and vagina. 5. We confirm the work of others that myelinated fibres attached to peripheral receptive fields can be found in ventral roots and that the receptive fields and functional qualities of these fibres are as one would expect of dorsal root fibres for the same segments. 6. A previous study demonstrated that approximately 30% of the axons in the L7 and S1 cat ventral roots are unmyelinated and arise from dorsal root ganglion cells. The present study confirms that these axons are sensory and that the axons are predominantly cutaneous nociceptors and visceral afferents. Thus it is concluded that the L7 and S1 cat ventral roots have a major sensory component.