Showing papers on "Receptive field published in 1982"

Visual Neurones Responsive to Faces in the Monkey Temporal Cortex

Abstract: Of 497 single neurones recorded in the cortex in the fundus of the superior temporal sulcus (STS) of three alert rhesus monkeys, a population of at least 48 cells which were selectively responsive to faces had the following response properties: (1) The cells' responses to faces (real or projected, human or rhesus monkey) were two to ten times as large as those to gratings, simple geometrical stimuli or complex 3-D objects. (2) Neuronal responses to faces were excitatory, sustained and were time-locked to the stimulus presentation with a latency of between 80 and 160 ms. (3) The cells were unresponsive to auditory or tactile stimuli and to the sight of arousing or aversive stimuli. (4) The magnitude of the responses of 28 cells tested was relatively constant despite transformations, such as rotation, so that the face was inverted or horizontal, and alterations of colour, size or distance. (5) Rotation to profile substantially reduced the responses of 21 cells (31 tested). (6) Masking out or presenting parts of the face (i.e. eyes, mouth or hair) in isolation revealed that different cells responded to different features or subsets of features. (7) For several cells, responses to the normal organisation of cut-out or line-drawn facial features were significantly larger than to jumbled controls. These findings indicate that explanations in terms of arousal, emotional or motor reactions, simple visual feature sensitivity or receptive fields are insufficient to account for the selective responses to faces and face features observed in this population of STS neurones. It appears that these neurones are part of a system specialised to code for faces or features present in faces, and it is suggested that damage to this system is related to prosopagnosia, or difficulty in face recognition, in man and to the tameness and social disturbances which follow temporal lobe damage and are part of the Kluver-Bucy syndrome in the monkey.

Predictive Coding: A Fresh View of Inhibition in the Retina

Abstract: Interneurons exhibiting centre--surround antagonism within their receptive fields are commonly found in peripheral visual pathways. We propose that this organization enables the visual system to encode spatial detail in a manner that minimizes the deleterious effects of intrinsic noise, by exploiting the spatial correlation that exists within natural scenes. The antagonistic surround takes a weighted mean of the signals in neighbouring receptors to generate a statistical prediction of the signal at the centre. The predicted value is subtracted from the actual centre signal, thus minimizing the range of outputs transmitted by the centre. In this way the entire dynamic range of the interneuron can be devoted to encoding a small range of intensities, thus rendering fine detail detectable against intrinsic noise injected at later stages in processing. This predictive encoding scheme also reduces spatial redundancy, thereby enabling the array of interneurons to transmit a larger number of distinguishable images, taking into account the expected structure of the visual world. The profile of the required inhibitory field is derived from statistical estimation theory. This profile depends strongly upon the signal: noise ratio and weakly upon the extent of lateral spatial correlation. The receptive fields that are quantitatively predicted by the theory resemble those of X-type retinal ganglion cells and show that the inhibitory surround should become weaker and more diffuse at low intensities. The latter property is unequivocally demonstrated in the first-order interneurons of the fly's compound eye. The theory is extended to the time domain to account for the phasic responses of fly interneurons. These comparisons suggest that, in the early stages of processing, the visual system is concerned primarily with coding the visual image to protect against subsequent intrinsic noise, rather than with reconstructing the scene or extracting specific features from it. The treatment emphasizes that a neuron's dynamic range should be matched to both its receptive field and the statistical properties of the visual pattern expected within this field. Finally, the analysis is synthetic because it is an extension of the background suppression hypothesis (Barlow & Levick 1976), satisfies the redundancy reduction hypothesis (Barlow 1961 a, b) and is equivalent to deblurring under certain conditions (Ratliff 1965).

Auditory and visual maps of space in the optic tectum of the owl

Abstract: The receptive field properties and functional organization of visual and auditory responses were studied in the optic tectum of the barn owl (Tyto alba). Most units throughout the depth of the tectum responded to both visual and auditory stimuli. The entire visual field of each eye was represented topographically in the contralateral tectum. In the portion of the tectal map representing the zone of binocular vision, 50% of the superficial layer units and 100% of the deep; layer units were driven binocularly. The representation of the frontal binocular region of space was greatly expanded in the map; the average magnification factor was 3 times greater for the frontal binocular zone than for the monocular zone. The responses of the superficial and deep tectal units to auditory stimuli were space specific; they responded only when a sound source was located in a particular region of space, or receptive field, regardless of the intensity or type of sound used. Most auditory receptive fields contained a distinct "best area" where a sound source was most effective in driving the unit. Auditory space, as defined by receptive fields and best areas, was represented topographically in the tectum. The auditory and visual maps of space had the same orientations, positions, magnification factors, and termination coordinates at the anterior and dorsal edges of the tectum. Yet the maps lost their registry near the posterior and ventral margins where the most peripheral regions of space were represented. These characteristics suggest that the spatiotopic organization in the tectum is a compromise between a tendency for the space representations of different modalities to align and for the representation of each modality to fill the entire tectum.

Motion sensitive interneurons in the optomotor system of the fly

Abstract: The functional properties of the three horizontal cells (north horizontal cell, HSN; equatorial horizontal cell, HSE; south horizontal cell, HSS) in the lobula plate of the blowflyCalliphora erythrocephala were investigated electrophysiologically. 1. The receptive fields of the HSN, HSE, and HSS cover the dorsal, equatorial and ventral part of the ipsilateral visual field, respectively. In all three cells, the sensitivity to visual stimulation is highest in the frontal visual field and decreases laterally. The receptive fields and spatial sensitivity distributions of the horizontal cells are directly determined by the position and extension of their dendritic fields in the lobula plate and the dendritic density distributions within these fields. 2. The horizontal cells respond mainly to progressive (front to back) motion and are inhibited by motion in the reverse direction, the preferred and null direction being antiparallel. The amplitudes of motion induced excitatory and inhibitory responses decline like a cosine function with increasing deviation of the direction of motion from the preferred direction. Stimulation with motion in directions perpendicular to the preferred direction is ineffective. 3. The preferred directions of the horizontal cells show characteristic gradual orientation changes in different parts of the receptive fields: they are horizontally oriented only in the equatorial region and increasingly tilted vertically towards the dorsofrontal and ventrofrontal margins of the visual field. These orientation changes can be correlated with equivalent changes in the local orientation of the lattice of ommatidial axes in the pertinent compound eye. 4. The response amplitudes of the horizontal cells under stimulation with a moving periodic grating depend strongly on the contrast frequency of the stimulus. Maximal responses were found at contrast frequencies of 2---5 Hz. 5. The spatial integration properties of the horizontal cells (studied in the HSE) are highly nonlinear. Under stimulation with extended moving patterns, their response amplitudes are nearly independent of the size of the stimuli. It is demonstrated that this response behaviour does not result from postsynaptic saturation in the dendrites of the cells. The results indicate that the horizontal system is essentially involved in the neural control of optomotor torque responses performed by the fly in order to minimize unvoluntary deviations from a straight flight course.

The Parietal Cortex of Monkey and Man

Abstract: I. Introduction.- II. Anatomy and Evolution of the Parietal Lobe in Monkeys and Man.- A. Anatomy.- B. Evolution.- III. Functional Properties of Neurones in the Primary Somatosensory Cortex.- A. Comments About Methods.- B. Movement and Orientation Selective Neurones in SI.- C. Receptive Field Integration and Submodality Convergence in SI.- D. Influence of Attention on Neuronal Function in SI.- IV. Neural Connections in the Posterior Parietal Lobe of Monkeys.- A. Connections of Area 5.- B. Connections of Area 7.- C. Summary of Connections.- V. Symptoms of Posterior Parietal Lesions.- A. Humans.- 1. Visuo-Spatial Disorientation.- 2. Defects in Eye Movements.- 3. Misreaching.- 4. Constructional Apraxia.- 5. Unilateral Neglect.- 6. Gerstmann Syndrome.- B. Monkeys.- 1. Visuo-Spatial Disorientation.- 2. Defects in Eye Movements.- 3. Misreaching.- 4. Unilateral Neglect.- 5. Somatic Deficits.- C. Comparison of Monkeys and Man.- VI. Electrical Stimulation of Posterior Parietal Lobe.- A. Monkey.- B. Man.- VII. Neuronal Activity in Area 5.- A. Sensory Properties.- B. Motor Properties.- C. Sensorimotor Interaction in Area 5.- VIII.Neuronal Activity in Area 7.- A. Visual and Oculomotor Mechanisms.- 1. Visual Fixation Neurones.- 2. Visual Tracking Neurones.- 3. Saccade Neurones...- 4. Visual Sensory Neurones.- B. Somatic Mechanisms.- 1. Cutaneous Responses.- 2. Kinaesthetic Responses.- 3. Activity Related to Somatic Movements.- C. Convergence of Somatic and Visual Functions.- D. Behavioural Mechanisms.- E. Effects of Drugs.- IX. Vestibular and Auditory Responses in the Parietal Lobe.- A. Vestibular Responses.- B. Auditory Responses in Area Tpt.- X. Regional Distribution of Functions in Area 7.- A. Mapping Methods.- B. Distribution of Responses.- 1. Visual Responses.- 2. Somatic Responses.- 3. Combined Responses from Several Modalities.- C. Somatotopy in Area 7.- D. Functional Differentiation.- XI. Modification of Area 7 and Functional Blindness After Visual Deprivation.- A. Visual Deprivation.- B. Deprivation Effects on the Visual Pathways.- C. Deprivation Effects on Area 7.- XII. Functional Role of Parietal Cortex.- A. Somatosensory Cortex.- B. Parietal Association Cortex.- 1. Sensory Functions.- a) Visual Functions.- b) Somaesthetic Functions.- c) Vestibular and Auditory Functions.- 2. Motor Functions.- a) Eye Movements.- b) Somatic Movements.- c) The Command Hypothesis.- d) The Corollary Discharge Hypothesis.- 3. Behavioural Functions.- a) Sensorimotor Interaction.- b) Spatial Schema.- c) Motivation-Intention-Attention.- d) Plasticity, Learning, Memory.- 4. Cellular Machinery.- a) Functional Organization.- b) Methodological Difficulties.- c) Factors That Influence Cellular Activity.- C. Parietal Lobe as a Whole.- References.

Pharmacological analysis of directionally sensitive rabbit retinal ganglion cells.

Abstract: 1. Cholinergic drugs were infused into the retinal circulation of the rabbit while we analysed the receptive field properties of directionally sensitive retinal ganglion cells. Physostigmine eliminated the trigger feature, directional specificity, of both types (on-centre and on—off) of these cells. In this respect the action of physostigmine (an ACh potentiator) was very like that of picrotoxin (a GABA antagonist). Therefore, a detailed analysis of the receptive field properties of directionally sensitive ganglion cells was made to analyse the effects of physostigmine and picrotoxin. 2. Size specificity and radial grating inhibition were not abolished by physostigmine, but were often affected by picrotoxin. The optimal velocity in the preferred direction (as measured by maximum firing frequency) was not much changed by physostigmine, but was higher during infusion of picrotoxin. Infusion of nicotine, a depolarizing ACh agonist which increases the activity of retinal ganglion cells, revealed the presence of inhibition to movement in the null direction. The null direction response during picrotoxin started slightly later than this inhibition. The null direction response during physostigmine was weaker and started later still. Mecamylamine and dihydro-β-erythroidine, nicrotinic receptor antagonists, totally blocked the effect of physostigmine and reduced the control light response by about half. 3. From this analysis, it appears that on—off ACh release onto directionally sensitive cells provides a substantial excitation which, when potentiated by physostigmine, overcomes or outlasts the null direction GABA inhibition within the receptive field. The spatial extent of GABA inhibition is asymmetric to and larger than the spatial extent of ACh excitation. Similar pathways appear to be involved in both the on-centre and on—off directionally sensitive ganglion cells, yet the on-centre cell pathway may receive an additional input which suppresses the ACh excitation at light offset. Possible schemes for the cellular mechanism of directional sensitivity are discussed in light of these results and recent anatomical and pharmacological findings.

Motion sensitive interneurons in the optomotor system of the fly II: The horizontal cells: Receptive field organization and response characteristics

Abstract: The functional properties of the three horizontal cells (north horizontal cell, HSN; equatorial horizontal cell, HSE; south horizontal cell, HSS) in the lobula plate of the blowflyCalliphora erythrocephala were investigated electrophysiologically. 1. The receptive fields of the HSN, HSE, and HSS cover the dorsal, equatorial and ventral part of the ipsilateral visual field, respectively. In all three cells, the sensitivity to visual stimulation is highest in the frontal visual field and decreases laterally. The receptive fields and spatial sensitivity distributions of the horizontal cells are directly determined by the position and extension of their dendritic fields in the lobula plate and the dendritic density distributions within these fields. 2. The horizontal cells respond mainly to progressive (front to back) motion and are inhibited by motion in the reverse direction, the preferred and null direction being antiparallel. The amplitudes of motion induced excitatory and inhibitory responses decline like a cosine function with increasing deviation of the direction of motion from the preferred direction. Stimulation with motion in directions perpendicular to the preferred direction is ineffective. 3. The preferred directions of the horizontal cells show characteristic gradual orientation changes in different parts of the receptive fields: they are horizontally oriented only in the equatorial region and increasingly tilted vertically towards the dorsofrontal and ventrofrontal margins of the visual field. These orientation changes can be correlated with equivalent changes in the local orientation of the lattice of ommatidial axes in the pertinent compound eye. 4. The response amplitudes of the horizontal cells under stimulation with a moving periodic grating depend strongly on the contrast frequency of the stimulus. Maximal responses were found at contrast frequencies of 2–5 Hz. 5. The spatial integration properties of the horizontal cells (studied in the HSE) are highly nonlinear. Under stimulation with extended moving patterns, their response amplitudes are nearly independent of the size of the stimuli. It is demonstrated that this response behaviour does not result from postsynaptic saturation in the dendrites of the cells. The results indicate that the horizontal system is essentially involved in the neural control of optomotor torque responses performed by the fly in order to minimize unvoluntary deviations from a straight flight course.

Reorganization of raccoon somatosensory cortex following removal of the fifth digit.

Abstract: The organization of part of the primary somatosensory cortex was examined in anesthetized raccoons at 2, 8, or 16 weeks after the normal peripheral input to this region of cortex had been removed by amputation of the fifth digit. Electrophysiological recordings were made in and around the cortical area representing the fifth digit. Eight intact animals were used to verify that this specific area could be accurately localized on the basis of the sulci and to determine the normal response characteristics of this area. The results from nine animals with the fifth digit removed provided evidence for a gradual reorganization of the cortical area which had been functionally denervated. At 2 weeks postamputation the field was almost totally unresponsive to sensory input. At 8 weeks many sites were responsive to high intensity stimulation of rather extensive regions of the hand. At 16 weeks the cells fired more readily to peripheral stimulation than at 8 weeks and tended to have smaller, more restricted receptive fields. The location of receptive fields in this latter group suggested that the fifth digit area was taken over primarily by input from the fourth digit. The time course of this reorganization is suggestive of extensive anatomical changes either within the cortex itself or at subcortical levels.

Theory of spatial position and spatial frequency relations in the receptive fields of simple cells in the visual cortex

Abstract: Striate cells showing linear spatial summation obey very general mathematical inequalities relating the size of their receptive fields to the corresponding spatial frequency and orientation tuning characteristics. The experimental data show that, in the preferred direction of stimulus motion, the spatial response profiles of cells in the simple family are well described by the mathematical form of Gabor elementary signals. The product of the uncertainties in signalling spatial position (?x) and spatial frequency (?f) has, therefore, a theoretical minimum value of ?x?f=1/2. We examine the implications that these conclusions have for the relationship between the spatial response profiles of simple cells and the characteristics of their spatial frequency tuning curves. Examples of the spatial frequency tuning curves and their associated spatial response profiles are discussed and illustrated. The advantages for the operation of the visual system of different relationships between the spatial response profiles and the characteristics of the spatial frequency tuning curves are examined. Two examples are discussed in detail, one system having a constant receptive field size and the other a constant bandwidth.

Long axons within the striate cortex: their distribution, orientation, and patterns of connection.

Abstract: Rockland and Lung [Rockland, K. S. & Lung, J. S. (1982) Science 215, 1532-1534] have recently observed that an injection of horseradish peroxidase into the striate cortex of the tree shrew produces a patchy distribution of label adjacent to the injection site. They proposed that this pattern might be due to populations of neurons with long-range cortico-cortical connections that are interspersed with populations having no such connections. We suggest here an alternative explanation. We can account for the pattern by supposing that the label is carrier by a system of oriented axons. We suppose that these axons link cells with similar orientation preferences and make their connections within a narrow strip of cortex whose direction is related to the orientation of the cells in question. We suggest that such connections could be involved in generating complex receptive fields from simple ones. Other possibilities are that they are used to generate very elongated receptive fields, inhibitory flanks, or end-stopping. We suggest a number of experimental tests of these ideas.

The influence of temporal frequency and adaptation level on receptive field organization of retinal ganglion cells in cat.

Abstract: 1. The discharges of single X and Y ganglion cells (distinguished by a test of linearity of spatial summation) were recorded in the optic tract of anaesthetized, paralysed cats. 2. Fourier techniques were used to analyse the distribution of amplitudes of several component temporal frequencies in the maintained discharge. X and Y cells were distinguished by their mean rates, but not by the amplitude or variability of other component frequencies. 3. Sensitivities to moving sinusoidal gratings were measured by an automatic procedure in which stimulus contrast was adjusted to give the smallest modulation of discharge that reliably exceeded that of the relevant component frequency in the maintained discharge. 4. Spatial contrast sensitivity curves of X cells and of on-centre Y cells could be described by a model of the receptive field as two concentric Gaussian sensitivity profiles representing the centre and the antagonistic surround. 5. Changes in temporal frequency altered the shapes of the spatial contrast sensitivity curves of most units. For X cells sensitivity at the optimum spatial frequency was greater at a temporal frequency of 10·4 Hz than at lower or higher temporal frequencies. The relative sensitivity to low spatial frequencies improved as temporal frequency was raised from 0·16 to 20·8 Hz. The shapes of the contrast sensitivity functions of Y cells were less affected by changes in temporal frequency: at all spatial frequencies sensitivity was greater at 2·6 Hz than at lower or higher frequencies. 6. The effect of temporal frequency upon the shape of the spatial contrast sensitivity curve could be explained by assuming that the centre and surround changed their sensitivities without changing their characteristic radii. A simple model, using a temporal R—C filter in the surround pathway, predicted qualitatively similar changes in the shape of contrast sensitivity curves but failed to provide acceptable fits to the observations. A second model, which assumed that surround signals are delayed by a fixed amount before being combined with those from the centre, fitted the observations of most, but not all, X cells. 7. Dark adaptation produced changes in the shape of the spatial contrast sensitivity curve consistent with a reduction in the relative sensitivity of the surround, but did not bring about systematic changes in the space constants of the best-fitting theoretical curves. 8. The effects of adaptation level upon contrast sensitivity were expressed as plots of increment—threshold against mean illumination. The shallowest of these curves, obtained for the optimum spatial stimulus moving at about 10 Hz, had slopes averaging 0·77. Decreases in spatial or temporal frequency increased the slopes of the curves.

Horizontal cells in the retina of the rabbit

Abstract: The light responses, morphology, and connections of horizontal cells (HCs) were studied in the retina of the rabbit using intracellular recordings and the injection of visible markers. Two types of HCs were identified, axonless and axon-bearing HCs. Axonless HCs and the somatic end of axon-bearing HCs respond to white light of varying intensity with graded hyperpolarizations; both display a transient superimposed on the sustained hyperpolarization at stimulus initiation and a small rod aftereffect at the cessation of high intensity stimuli. Anatomically, both are connected to cones, but their responses also suggest rod influence. Both summate stimuli from a retinal area which is much larger than their respective fields. However, only axonless HCs transfer a fluorescent, low molecular weight dye to adjoining, homologous cells. The axon terminal of axon-bearing HCs has response properties different from those of the cell body: the transient at stimulus initiation is absent; furthermore, at high levels of illumination, the rod aftereffect becomes equal in amplitude to the primary hyperpolarization. Anatomically, it is connected to rods, but its responses also suggest cone influence. Its receptive field approximates in diameter its anatomical spread and it does not transfer fluorescent dye to its neighbors.

Effects of cholinergic drugs on receptive field properties of rabbit retinal ganglion cells.

Abstract: 1. Retinal ganglion cells were recorded extracellularly from the rabbit's eye in situ to study the effects of cholinergic drugs on receptive field properties. Physostigmine, an acetylcholinesterase inhibitor, and nicotine increased the spontaneous activity of nearly all retinal ganglion cell types. The effectiveness of physostigmine was roughly correlated with the neurone's inherent level of spontaneous activity. Brisk cells, having high rates of spontaneous firing, showed large increases in their maintained discharge, whereas sluggish cells, with few or no spontaneous spikes, showed small and sometimes transient increases in spontaneous activity during physostigmine. 2. The sensitivity of ganglion cells to spots of optimal size and position did not change substantially during the infusion of physostigmine. However, the responsiveness to light (number of spikes per stimulus above the spontaneous level) increased. This effect occurred with sluggish and more complex cells, rarely with brisk cells. 3. Another effect of physostigmine on sluggish and more complex cells was to make these cells `on—off'. The additional response to the inappropriate change in contrast had a long latency and lacked an initial transient burst. 4. Complex receptive field properties such as orientation sensitivity, radial grating inhibition, speed tuning and size specificity were also examined. These inhibitory properties were still present during infusion of physostigmine and, in most cases, the trigger feature of each cell type remained. 5. These results are consistent with pharmacological results on ACh release from the retina. There appear to be two types of release of ACh, having their most powerful influences on separate classes of cells. One release (transient), occurs at light onset and offset and acts primarily on sluggish and more complex ganglion cells; the other release (tonic) is not light-modulated and acts primarily on brisk cells. A wiring diagram for the ACh cells is suggested.

The nature of the excitatory transmitter mediating X and Y cell inputs to the cat dorsal lateral geniculate nucleus

Abstract: 1. In experiments examining the possibility that an excitatory amino acid may be an optic nerve transmitter in mammals, excitatory amino acid antagonists have been ionophoretically applied to cells in layers A and A1 of the cat dorsal lateral geniculate nucleus and their effect on the excitatory response to visual stimulation of the receptive field centre has been assessed. 2. The antagonists used were D-α-aminoadipate (D-α-AA), DL-α-e-diaminopimelic acid (DAP), 1-hydroxy-3-amino-2-pyrrolidone (HA-966) and L-glutamate diethyl ester (GDEE). The antagonist effects on the visual response were compared with their effect on similar magnitude responses evoked by ionophoretic pulses of selected agonists and a control excitant, generally acetylcholine. 3. Both D-α-AA and HA-966 would selectively block or depress the visual response with respect to the response to the control excitant. At the stage the visual input was blocked, responses to the agonists N-methyl-D-aspartate (NMDA), DL-homocysteic acid (DLH) and glutamate were also greatly reduced or blocked. At dose levels below those causing a significant reduction in the visual response, D-α-AA and HA-966 would selectively depress responses to NMDA and DLH with respect to the response to glutamate. 4. GDEE was relatively ineffective in blocking either agonist responses or the visual response and only produced a significant reduction in either at dose levels that caused a similar depression in the response to acetylcholine. DAP would block responses to DLH but produced no significant effect on the visual response or the responses to glutamate and acetylcholine. 5. The cholinergic antagonists atropine and dihydro-β-erythroidine (DHβE) blocked responses to acetylcholine without significantly reducing either visual driving or the response to DLH. 6. The effects were the same for X and Y cells in the dorsal lateral geniculate nucleus (dLGN). There was also no distinctions between ‘on’ and ‘off’ centre types of each of the two groups. 7. The significance of these results is discussed. It is argued that they reintroduce the possibility that either L-aspartate, L-glutamate or a similar substance may be the transmitter mediating the optic nerve input to the cat dLGN.

Single cell responses in cat visual cortex to visual stimulation during iontophoresis of noradrenaline.

Abstract: We studied how iontophoresis of noradrenaline (NA) changes responsiveness of individual cells in the feline visual cortex when their visual receptive fields are stimulated with the appropriate visual stimulus. We found three populations of cortical cells which either increased, decreased or did not change their visual responsiveness during NA iontophoresis. About equal numbers of cells belonged to each of these three groups. In the majority of such cells that changed visual responsiveness during NA iontophoresis and that had measurable amounts of spontaneous activity, the ratio of visually evoked to spontaneous activity (signal-to-noise ratio) improved during NA iontophoresis. This improvement was independent of the direction of changes in the response magnitude to visual stimulation. There was a differential effect of NA on simple and complex visual cortical cells: Although most simple cells (86%) clearly changed their responsiveness during NA iontophoresis, the effects were seen in only one-third of complex cells. Furthermore, the effects on complex cells were usually weak compared to those typically seen in simple cells. In some cases the effects of NA were more complicated than an overall enhancement or suppression of the cortical cell's responses to visual stimulation. The possible dual role of NA in the visual cortex is briefly discussed.

A physiological and morphological study of the horizontal cell types of the rabbit retina

Abstract: A perfused, isolated retina-eyecup preparation of the rabbit was utilized to correlate the physiology and morphology of horizontal cells. Neurons were physiologically characterized by intracellular recording techniques and subsequently stained with intracellular iontophoretically injected horseradish peroxidase for morphological identification. Three types of rabbit horizontal cell recordings have been differentiated, based on variations in response waveform, amplitude-intensity properties, and area summation characteristics. These three types have been unequivocally associated with the axonless A-type horizontal cells and the somatic and axon terminal endings (each displaying its own distinct physiology) of B-type horizontal cells first described in studies using Golgi-impregnation techniques (Fisher and Boycott, 1974). In addition, the sizes of A-type horizontal cells were found to be directly related to their retinal eccentricities from the optic disk. However, a unique subclass of A-type cells has been discovered (elongated or Ae type) which displayed the largest dendritic field of any cells studied here, yet had the smallest eccentricities—within 1.4 mm of the optic disk. Moreover, elongated A-type cells exhibited long asymmetrical dendritic fields which were oriented parallel with the visual streak. The unique asymmetry and orientation of these cells suggests that they may have orientation-biased receptive field properties. Physiological evidence for an orientation-biased horizontal cell is presented in support of this notion.

Vision and electroreception: Integration of sensory information in the optic tectum of the weakly electric fishApteronotus albifrons

Abstract: The responses of single neurons to visual and electrosensory stimulation were studied in the optic tectum of the weakly electric fishApteronotusalbifrons. Most of the cells recorded in the region of the tectum studied, the anterior medial quadrant, were poorly responsive or completely insensitive to flashes of light or to bursts of AC electrical stimuli applied to the entire fish. However, these cells gave vigorous responses to moving visual or electrosensory stimuli. Most cells showed differences in their response contingent upon the direction of the stimulus movement and most received input from both the visual and electrosensory systems. Electrosensory responses to moving stimuli were depressed by jamming stimuli, 4 Hz amplitude modulation of the animal's electric organ discharge, presented simultaneously with the moving stimulus. However, the jamming signal presented alone typically evoked no response. Moving visual stimuli, presented simultaneously with the electrosensory, were usually able to restore the magnitude of a response toward its value in the unjammed situation. For most of the cells studied the receptive fields for vision and electroreception were in register. In some cases the visual and electrosensory components could be separated by presenting the two types of stimuli separately, or by presenting both simultaneously but with some amount of spatial separation, which causes the two to be misaligned relative to the fish. In other cases the individual responses could not be separated by spatial manipulations of the two stimuli and in these cases differences in the alignment of the two types of stimuli could cause changes in the intensity of the cells' responses.

Abnormal development of kitten retino-geniculate connectivity in the absence of action potentials

Abstract: Action potentials were silenced in one eye of neonatal kittens by repeated intraocular injections of tetrodotoxin for 5 to 8 weeks. After tetrodotoxin blockade was allowed to wear off, receptive field properties of individual relay cells in the lateral geniculate nucleus were examined. The many ON-OFF and binocular fields found in the layers that receive input from the treated eye suggest that these cells had extremely abnormal retino-geniculate synaptic connections. These effects were different in kind from those seen after deprivation rearing that does not silence action potentials. Lack of action potential activity was concluded to lead to abnormal development in the central nervous system.

A model for the temporal organization of X- and Y-type receptive fields in the primate retina.

Abstract: A model is proposed for the temporal characteristics of X- and Y-type responses of ganglion cells in the primate retina. The main suggestions of the model are: (I) The X-type temporal response is determined primarily by the delay between center and surround contributions. (II) The Y-type response is generated in the inner plexiform layer by a derivative-like operation on the bipolar cell's input, followed by a rectification in the convergence of these inputs onto the Y-ganglion-cell. (III) The derivative-like operation is obtained by recurrent inhibition in the dyad synaptic structure. The X- and Y-type responses predicted by the model, for a variety of stimuli, were examined and compared with available electrophysiological recordings. Finally, certain predictions derived from the model are discussed.

Second somatic sensory area in the cerebral cortex of cats: Somatotopic organization and cytoarchitecture

Abstract: The cortex of the anterior ectosylvian gyrus and adjoining ectosylvian and suprasylvian sulci was explored with tungsten microelectrodes to determine the distribution of responses to light cutaneous stimulation in barbiturate-anesthetized cats. Recordings were spaced between 125 and 250 micrometers and, in several cases, nearly all of the somatic areas in this cortex were explored in the same brain. Four somatic sensory areas were identified on the basis of responses properties, sequences of receptive fields, and cytoarchitecture. The largest area, which occupied the rostral and medial two-thirds to three-fourths of the exposed, relatively flat portion of the anterior ectosylvian gyrus, was called the second somatic sensory area (SII). Receptive fields in SII were primarily from the contralateral side of the body; they were well defined and somatotopically organized into an erect representation of the body. The top of the head was located next to a similar representation of the periphery in a portion of the first somatic sensory area (SI). Individual distal digits and toes occupied discrete components of the SII map. Another representation for the distal forelimb and hindlimb was noted medially along the lateral bank of the anterior suprasylvian sulcus. Receptive fields and response properties in this region were equivalent to those seen in SII proper. However, only a crude anteroposterior, fore- to hindlimb topographical organization was noted, but with more distal parts of the limbs generally located closer to the fundus of the sulcus in this medial representation. As the cytoarchitecture in this medial region was similar to the rest of SII it was considered a medial subdivision of SII. A third, topographically organized zone was located lateral to SII largely within the upper bank of the anterior ectosylvian sulcus and adjoining lateral crest of the anterior ectosylvian gyrus. Large, stockinglike, contralateral receptive fields were common; ipsilateral components to the receptive fields were present. Some individual digit receptive fields were located in the rostral part of the forelimb zone within the anterior ectosylvian sulcus. This lateral somatic area is probably equivalent to a fourth somatic sensory area (SIV) recently identified by Clemo and Stein ('82). Posterior to the hindlimb zones of SII and medial to SIV was another region that responded to cutaneous plus auditory stimulation. There was no detectable topography in this area; nearly all of the receptive fields were large, frequently bilateral, and often involved the whole body or all four extremities. This area's cytoarchitecture was comparable to previous descriptions of the suprasylvian fringe (Rose, '49). The location and physiology of these four areas were discussed in reference to previous controversies regarding the topography of the body representation in SII and the location of an acallosal zone in this region of cortex.

Visual receptive field properties of cells innervated through the corpus callosum in the cat.

Abstract: The present experiment examined the receptive field (R.F.) properties of cortical cells which receive part of their input from the contralateral hemisphere via the corpus callosum. Two groups of cats were used for recording unit activity: a normal control group, and an experimental group consisting of cats which had their optic chiasmas split across the midline prior to the recording sessions. Acute recordings were carried out in the conventional manner using tungsten microelectrodes and N2O: O2 anaesthesia. The recording site was the 17–18 border. The stimulus consisted of a thin bar generated on an oscilloscope screen by a computer. The bar, whose orientation was varied automatically from 0 ° to 345 ° in 15 ° steps, was swept across the screen at constant speed orthogonal to the orientation. Various R.F. properties were studied using both quantitative and qualitative criteria. Thus, in the normal cat, simple, complex and hypercomplex type R.F.'s were found, whereas no callosally activated cell was of the simple type. The ocular dominance distribution found in the split chiasma cat was skewed towards the ipsilateral eye, although a fairly large number of cells could be driven with the two eyes. The R.F.'s of the callosally activated neurons were all situated close to the vertical meridian, which they sometimes straddled. Both in the normal and in the chiasma sectioned cats, the complex cells had larger R.F.'s than the other cell types. However, the R.F.'s determined through the ipsilateral eye was essentially of the same dimensions as those obtained through the indirect interhemispheric pathway, and this irrespective of cell type. Orientation specificity was similar for the two eyes in the split chiasma cats as it was for the normal cats although in the former the orientation tuning curve was narrower for the callosal pathway than for the more direct thalamo-cortical pathway. The results are interpreted within the context of the different functions ascribed to the corpus callosum in vision.

Physiological and morphological identification of two types of on-center bipolar cells in the carp retina

Abstract: Two types of on-center bipolar cells, rod- and cone-dominant bipolars have been identified in the dark-adapted retina of the carp by means of intracellular recordings and Lucifer-yellow dye injection. They differ physiologically and morphologically in the following respects: 1) responses of rod-dominant cells to bright lights are characterized by a transient depolarization followed by a smaller sustained depolarization, while those of cone-dominant cells are approximately rectangular; 2) the cone-dominant cells are about 1.5 log units less sensitive to light than the rod-dominant cells; 3) the latency of the response is shorter in the cone-dominant cells than in the rod-dominant cells; 4) the mean diameters of the cone-dominant cell receptive field (0.7 mm) and dendritic field (90 micrometers) are larger than those of the rod-dominant cell receptive field (0.5 mm) and dendritic field (56 micrometers); 5) the mean diameter of the cone-dominant cell soma (8 micrometers) is smaller than that of the rod-dominant cell soma (13 micrometers); and 6) the terminations of the cone-dominant cell axons form a ramification (67 micrometers mean diameter) in contrast to a big terminal swelling of the rod-dominant cell axons (37 micrometers mean diameters). At least two ionic mechanisms are responsible for generating the depolarizing response of on-center bipolar cells, one having a reversal at a positive potential and the other at a negative potential. Responses with a negative reversal potential only are obtained from some of cone-dominant cells and responses with a positive reversal potential only are obtained from some other cone-dominant cells and the rod-dominant cells. There are a large number of bipolar cells that respond by both ionic mechanisms, although the ratio between them varied considerably in different cells.