Showing papers on "Receptive field published in 1981"

Visual properties of neurons in a polysensory area in superior temporal sulcus of the macaque.

Abstract: 1. We recorded from single neurons in the dorsal bank and fundus of the anterior portion of the superior temporal sulcus, an area we term the superior temporal polysensory area (STP). Five macaques were studied under anesthesia ( N20) and immobilization in repeated recording sessions. 2. Almost all of the neurons were visually responsive, and over half responded to more than one sensory modality; 21% responded to visual and auditory stimuli, 17% responded to visual and somesthetic stimuli, 17% were trimodal, and 41% were exclusively visual. 3. Almost all the visual receptive fields extended into both visual half-fields, and the majority approached the size of the visual field of the monkey, including both monocular crescents. Somesthetic receptive fields were also bilateral and usually included most of the body surface. 4. Virtually all neurons responded better to moving visual stimuli than to stationary visual stimuli, and almost half were sensitive to the direction of movement. Several classes of directional neurons were found, including a) neurons selective for a single direction of movement throughout their receptive field, b) neurons selective for directions of movement radially symmetric about the center of gaze, and c) neurons selective for movement in depth. 5. The majority of neurons (70%) had little or no preference for stimulus size, shape, orientation, or contrast. The minority (30%) responded best to particular stimuli. Some of these appeared to be selective for faces. 6. The properties of most STP neurons, such as large receptive fields, sensitivity to movement, insensitivity to form, and polymodal responsiveness, suggest that STP is more involved in orientation and spatial functions than in pattern recognition.

The middle temporal visual area in the macaque: Myeloarchitecture, connections, functional properties and topographic organization

Abstract: The location, topographic organization, and function of the middle temporal visual area (MT) in the macaque monkey was studied using anatomical and physiological techniques. MT is a small, elliptically shaped area on the posterior bank of the superior temporal sulcus which can be identified by its direct inputs from striate cortex and by its distinctive pattern of heavy myelination. Its average surface area is 33 mm2, which is less than 3% of the size of striate cortex. It contains a complete, topographically organized representation of the contralateral visual hemifield. There are substantial irregularities in the detailed pattern of topographic organization, however, and the representation is significantly more complex than that found for MT in other primates. Much of MT is devoted to the representation of central visual fields, with the emphasis on central vision being similar to that found in striate cortex. Electrophysiological recordings have confirmed previous reports of a high incidence of direction selective cells in MT. The transition in functional properties, from cells lacking direction selectivity outside MT to direction selective cells within, occurs over a distance of 0.1–0.2 mm or less along the lateral border of MT. Such a transition does not occur along the medial border, however, as the cortex medial to MT contains many cells with strong direction selectivity. Nevertheless, this region differs from MT in its myeloarchitecture, its lack of inputs from striate cortex, and the large size of its receptive fields. These results demonstrate the existence of three distinct visual areas on the posterior bank of the superior temporal sulcus which can be distinguished on the basis of both physiological and anatomical criteria.

Visual Topography of V2 in the Macaque

Abstract: The representation of the visual field in the area adjacent to striate cortex was mapped with multiunit electrodes in the macaque. The animals were immobilized and anesthetized and in each animal 30 to 40 electrode penetrations were typically made over several recording sessions. This area, V2, contains a topographically organized representation of the contralateral visual field up to an eccentricity of at least 80 degrees. The representation of the vertical meridian is adjacent to that in striate cortex (V1) and forms the posterior border of V2. The representation of the horizontal meridian in V2 forms the anterior border of V2 and is split so that the representation of the lower visual field is located dorsally and that of the upper field ventrally. As in V1, the representation of the central visual field is magnified relative to that of the periphery. The area of V2 is slightly smaller than that of V1. At a given eccentricity, receptive field size in V2 is larger than in V1. The myeloarchitecture of V2 is distinguishable from that of the surrounding cortex. The location of V2 corresponds, at least approximately, to that of cytoarchitectonic Area OB. V2 is bordered anteriorly by several other areas containing representations of the visual field.

Magnification factor and receptive field size in foveal striate cortex of the monkey.

Abstract: Receptive field size and magnification have been studied in striate cortex of awake, behaving rhesus monkeys at visual eccentricities in the range of 5–160 min. The major findings that emerge are (1) magnification in the foveola achieves values in the range of 30 mm/deg, (2) mean field size is not proportional to inverse magnification in contrast with previous reports, and (3) the product, magnification X aggregate field size, is greater in central vision than in peripheral vision. Thus, a point of light projected onto foveal retina is “seen” by larger numbers of striate cortical cells than a point of light projected onto peripheral retina. Implications of these findings for visual localization and two-point discrimination are discussed.

Neuronal and behavioral sensitivity to binaural time differences in the owl

Abstract: We demonstrated that ongoing time disparity (OTD) was a sufficient cue for the azimuthal component of receptive fields of auditory neurons in the owl (Tyto alba) midbrain and that OTDs were sufficient to mediate meaningful behavioral responses. We devised a technique which enabled us to change easily between free field and dichotic stimuli while recording from single auditory neurons in the owl mesencephalicus lateralis pars dorsalis (MLD). MLD neurons with restricted spatial receptive fields (“space-mapped neurons”) showed marked sensitivity to specific ongoing time disparities. The magnitudes of these disparities were in the behaviorally significant range of tens of microseconds. The ongoing time disparities were correlated significantly with the azimuthal center of receptor fields. Space-mapped neurons were insensitive to transient disparities. MLD neurons which were not space- mapped, i.e., were omnidirectional, did not show any sensitivity to specific OTDs. We confirmed the behavioral relevance of OTD as a cue for localizing a sound in azimuth by presenting OTD differences to tame owls. Using head turning as an assay, we showed that OTD was a sufficient cue for the azimuth of a sound. The relationship between azimuth and OTD obtained from our neurophysiological experiments matched closely the relationship obtained from our behavioral experiments.

A comparison of binocular depth mechanisms in areas 17 and 18 of the cat visual cortex

Abstract: 1. The retinal disparity sensitivity of neurones in areas 17 and 18 of the cat visual cortex was examined. The response of each cell to an optimally oriented slit was measured as disparity was varied orthogonally to the receptive field orientation. Eye movements were monitored with a binocular reference cell simultaneously recorded in area 17 (Hubel & Wiesel, 1970). 2. Two types of disparity-sensitive cells were found, similar to those observed in the monkey by Poggio & Fischer (1977). The first type, tuned excitatory cells, were usually binocular and had a sharp peak in their disparity—response curve. They responded maximally at the disparity that brought their receptive fields into superposition on the tangent screen. This disparity closely coincided with the disparity at which the reference cell's receptive fields were also superimposed. By analogy with the monkey this point was taken to be the fixation point, or 0°. The second type, near and far cells, were most often monocular. They gave their weakest response (which was usually no response at all) at 0°. On one side of 0° the response grew linearly for up to 4° and then remained at the maximum. On the other side of zero, it remained at the minimum for up to several degrees before rising towards the maximum. 3. The receptive field organization of several disparity-sensitive cells was examined using the activity profile method of Henry, Bishop & Coombs (1969). The size and strength of the discrete excitatory and inhibitory regions of the receptive fields of a cell could quantitatively account for the shape of its disparity—response curve. 4. The laminar distribution of disparity sensitivity as well as of several other receptive field properties in areas 17 and 18 was studied. The organization of the two areas was remarkably similar in many respects. There was a difference, however, in the proportions of the two types of disparity-sensitive cells in the two areas. Area 17 contained many more tuned excitatory cells than near and far cells, while area 18 had the reverse distribution. In addition, the cells in area 18 were sensitive to a much broader range of disparities. While both areas contain disparity-sensitive neurones, these differences suggest that they play different roles in depth vision. 5. Recent psychophysical and neurophysiological evidence has led to a new model of stereopsis in which depth is signalled by the pooled activity of large groups of cells (Richards, 1971). The current results are consistent with this model.

Plasticity in the spinal cord sensory map following peripheral nerve injury in rats.

Abstract: The medial part of the L4 and 5 dorsal horn in adult rats is dominated by afferents from the toes and foot. After transection of the sciatic and saphenous nerves, virtually all cells in this region are left without any peripheral receptive field. Beginning 4 to 5 days after nerve section, however, many peripherally deafferented cells take on a novel receptive field on the thigh, lower back, or perineum. The new receptive fields are served by intact nerves ending in proximal skin rather than by misdirected sprouts of cut toe-foot nerves. Thus, peripheral axotomy results in synaptic reorganization in the spinal cord proper. Receptive field reorganization occurs after nerve transection, ligation, or ligation with distal transection but does not occur if the nerve is crushed. If a cut nerve is sutured and regeneration is permitted, spinal reorganization is reversed and the toe-foot afferents regain exclusive dominance of the medial dorsal horn.

Spatial summation and contrast sensitivity of X and Y cells in the lateral geniculate nucleus of the macaque

Abstract: Study of parallel processing in the visual pathway1 of the cat has revealed several classes of retinal ganglion cells which are physiologically distinct and which project to various locations in the brain2,3. Two classes have been studied most extensively: X cells, which sum neural signals linearly over their receptive fields, and Y cells, in which the spatial summation is nonlinear1,4. In the cat's lateral geniculate nucleus (LGN) cells also can be classified as X or Y, a result of the parallel projection of retinal X and Y inputs to different geniculate neurones5–9. We report here our study of parallel signal processing in the LGN of the macaque monkey. We find that (1) monkey LGN cells can be classified as X or Y on the basis of spatial summation; (2) X-like cells are found in the four parvocellular and the two magnocellular laminae, whereas Y-like cells are found almost exclusively in the magnocellular laminae; and (3) the cells of the magnocellular laminae have high sensitivity and the parvocellular cells low sensitivity for homochromatic patterns. This implies that in macaque monkeys the magnocellular cells and their cortical projections may be the neural vehicle for contrast vision near threshold. The cells of the parvocellular laminae seem to be primarily concerned with wavelength discrimination and patterns of colour. As the human visual system is similar to that of the macaque in structure and behavioural performance, our findings are probably also applicable to man.

The representation of the auditory and somatosensory systems in the external nucleus of the cat inferior colliculus

Abstract: Parallel single unit and retrograde tracing experiments were carried out in the anesthetized cat to elucidate the representation of the auditory and somatosensory systems in the external nucleus of the inferior colliculus (ICX). Units responding to tonal stimuli were more commonly encountered in ICX and the adjacent intercollicular area (ICA) than were units with identified tactile receptive fields. Concomitantly, a larger number of retrogradely labeled cells were identified in midbrain auditory structures, following injections of horseradish peroxidase (HRP) into CRX, than were found in the combined dorsal column nuclei. Microelectrode recording revealed that the entire accessible body surface was represented in ICX, and receptive fields of individual units were usually large and mostly located on the contralateral side. HRP-labeled cells were scattered throughout the contralateral cuneate, gracile, and spinal trigeminal nuclei. tations of tone pips. Responses to complex sound were commonly observed. Binaural stimuli influenced the firing of the majority of auditory units. Labeled auditory neurons following ICX injections were found mainly in the inferior colliculus of both sides. Spread of tracer into the central and pericentral nuclei was associated with labeling of many neurons in hind brain auditory structures. Only vague suggestions of somatotopy or tonotopy were observed in the electrophysiological experiments; similarly, no topographical relationship between HRP injection site and locus of retrograde label in a given projecting nucleus could be discerned. Speculations were made, in the light of the dual convergent sensory representation in ICX, about the role of this structure in acoustico-motor mechanisms.

Morphological identification of on- and off-centre brisk transient (Y) cells in the cat retina.

Abstract: Brisk transient (Y) cells were recorded extracellularly in the cat retina. The position and shape of their receptive field centres were plotted on a tangent screen, together with retinal landmarks, such as blood vessels adjacent to the recording area. After recording the retina was processed as a whole mount and stained with a reduced-silver method (see appendix). This technique stains the entire alpha cell population including the dendritic trees. Alpha cells are the morphological correlate of the brisk transient cells (Boycott & Wassle 1974; Cleland et al. 1975). Maps of the screen plot and the histological preparation could be accurately superimposed by means of the retinal landmarks and each recorded brisk transient unit could unequivocally be attributed to a particular alpha cell. Alpha cell dendritic trees are unistratified in either of two laminae within the inner plexiform layer: (1) close to the inner nuclear layer border, 'outer alpha cells', or (2) about 10 micrometers further towards the ganglion cell layer, 'inner alpha cells'. This stratification difference can be observed in whole mounts for large populations of cells (Wassle et al. 1981). Of the recorded brisk transient cells, all on-centre units were inner alphas and all off-centre units outer alphas.

How the contrast gain control modifies the frequency responses of cat retinal ganglion cells.

Abstract: 1. A model is proposed for the effect of contrast on the first-order frequency responses of cat retinal ganglion cells. The model consists of several cascaded low pass filters ('leaky integrators') followed by a single stage of negative feed-back. 2. Values of time constants and gain of the components in this model were chosen to approximate (with least-squared deviation) experimentally measured first-order frequency responses. In the experiments used for the analysis, the visual stimulus was a sine grating modulated by a sum of sinusoids. 3. For both X cells and Y cells, the over-all gain and the time constants of the cascade of low pass filters were insensitive to contrast. 4. In all cells, the gain-bandwidth product of the negative feed-back loop was markedly increased with increasing contrast. 5. The effect of stimulation in the periphery of the receptive fields on the first-order frequency response to a centrally placed spot was identical to the effect of increasing contrast in the grating experiments. In all cases, the gain-bandwidth product of the negative feed-back loop was the only model parameter affected by peripheral stimulation. 6. A similar effect of non-linear summation was investigated for two bars located in the receptive field periphery. 7. This analysis of the contrast gain control mechanism is compared with other models of retinal function.

A quantitative analysis of the direction-specific response of Neurons in the cat's nucleus of the optic tract.

Abstract: All cells in the nucleus of the optic tract (NOT) of the cat, that Bcould be activated antidromically from the inferior olive, were shown to be direction-specific, as influenced by horizontal movements of an extensive visual stimulus. Cells in the left NOT were activated by leftward and inhibited by rightward movement, while those in the right NOT were activated by rightward and inhibited by leftward movement. Vertical movements did not modulate the spontaneous activity of the cells. The mean spontaneous discharge rate in 50 NOT cells was 30 spikes/s. This direction-specific response was maintained over a broad velocity range ( 100 °/s). Velocities over 200 °/s could inhibit NOT cells regardless of stimulus direction. All cells in the NOT were driven by the contralateral eye, about half of them by the ipsilateral eye also. In addition, activation through the contralateral eye was stronger in most binocular units. Binocular cells preferred the same direction in the visual space through both eyes. An area approximately corresponding to the visual streak in the cat's retina projected most densely onto NOT cells. This included an extensive ipsilateral projection. No clear retinotopic order was seen. The most sensitive zone in the very large receptive fields (most diameters being >20 °) was along the horizontal zero meridian of the visual field. The retinal input to NOT cells was mediated by W-fibers. The striking similarities between the input characteristics of NOT-cells and optokinetic nystagmus are discussed. The direction selectivity and ocular dominance of the NOT system as a whole can provide a possible explanation for the directional asymmetry in the cat's optokinetic nystagmus when only one eye is stimulated.

Fine structure of myelinated mechanical nociceptor endings in cat hairy skin

Abstract: High-threshold mechanoreceptors (mechanical nociceptors) with myelinated axons were electrophysiologically identified in hairy skin of the cat as described by Burgess and Perl ('67). Such elements possess receptive fields consisting of a number of punctate areas from which maximal firing can be elicited by intense (skin-damaging) mechanical stimuli. The spots of the receptive field are separated from each other by unresponsive regions, i.e., by skin areas from which responses cannot be evoked by stimuli effective at the spots. Fine steel pins were inserted to bracket closely a number of the spotlike responsive areas for each of several units. After aldehyde perfusion of the animal, osmification of the tissue and embedding in plastic, the marked skin zones were examined in semithin and ultrathin sections at the light and electron microscopic level. Near each delineated area, a thinly myelnated axon was fond that could be traced to the papillary layer where it loses its myelin sheath. Unmyelinated axons accompanied by thin Schwann cell processes were then traced and found to penetrate the epidermal basal lamina in one of the papillae. At the epidermal penetration site, the axons contained both clear round, and large, dense core vesicles; at this level, the surrounding Schwann cell cytoplasm exhibited numerous pinocytotic vesicles. The zone of pentration may constitute the receptive apparatus. Some of these axons have been traced within the basal epidermal layer where they become surrounded by keratinocytes, lose their Schwann sheath, and apparently terminate. This overall morphological pattern was consistently present in the demarked areas of focal responsiveness, and was rare in the surrounding skin; this and its difference from other cutaneous neural endings suggest that the intraepidermal axon-Schwann cell complex constitutes the receptive structure for myelinated mechanical nociceptors. It is suggested that such complexes are the sense organs responsible for initiating the sensation of pricking pain produced by localized mechanical injury of the skin.

Intracortical arborizations and receptive fields of identified ventrobasal thalamocortical afferents to the primary somatic sensory cortex in the cat.

Abstract: The intracortical arborizations of neurons from the ventroposte- rolateral thalamic nucleus (VPL) in the cat were studied by intraaxonal injections of horseradish peroxidase (HRP) following identification of their receptive fields. In the primary somatic sensory cortex (SI) VPL cells terminated in different cyto- architectonic areas according to their receptive field modality. Fibers excited by deep tissues or joint rotation arborized preferentially in area 3a. Those responding tonically to cutaneous stimuli were located in the anterior part of area 3b; hair- driven cells terminated in area 3b and in the rostra1 pole of area 1. All fibers had a similar laminar distribution within SI. Axons terminated mostly in layers VI, IV, and the lower part of layer 111. None terminated in layers I and 11. Most terminal arbors were oriented along the mediolateral axis of the brain. The main arboriza- tion of a single VPL cell formed a bush of about 500 pm in diameter. Some fibers generated two such bushes with an uninvaded region of about 300 pm between them. It is proposed that this patchy organization underlies in part the columnar organization of area SI. Many VPL cells had secondary projection sites in SI. These were issued from smaller-sized collaterals and were located in a different cyto- architectonic area than that ofthe main terminal plexuses. A significant number of these collaterals projected to area 4. Insufficient filling of the collaterals by HRP prevented a more complete characterization of the secondary arbors. The cortical column is a concept that has proved useful in understanding the cerebral cortex. The existence of columns was first sug- gested by Mountcastle ('57). He showed that cells recorded along a perpendicular tract in the primary somatic sensory (SI) cortex had over- lapping receptive fields and that they all re- sponded to the same modality of stimulation. Later, Hubel and Weisel ('62, '69) demon- strated the existence of orientation and ocular dominance columns in the primary visual area. The radial arrangement of nerve cells in many cortical regions often suggests columnar arrangements. Lorente de NO ('38) pointed out that the cortical unit is a narrow cylinder of cells stretching from layer I1 to layer V1 and having roughly columnar shape. Colonnier ('66) stressed the preferential vertical orienta- tion of axons of many cortical cells and sug- gested that they are for processing inputs into vertical chains of neurons. He also emphasized that if the cortical circuitry has the necessary wiring for supporting the existence of cortical columns "the anatomical columns are not dis- tinct separate morphological entities." This implicitly suggested that the territorial limits of the functional columns were determined by the connectivity of thalamocortical afferents and by the tangential spread of inhibition within the cortex. In the primary visual area, ocular dominance columns have their morpho- logical basis in the alternating patches of ter- minal ramifications of geniculocortical afferents (Huber and Weisel, '69; Ferster and LeVay, '78; Gilbert and Weisel '79). More re- cently, the patchy nature of the cortical projec- tion from the ventroposterolateral (VPL) nu- cleus of the thalamus has also been demon- strated by autoradiography (Friedman and Jones, '80). Since the topographic charac- teristics of cortical columns appear to be deter- mined by thalamocortical input, we injected single VPL afferents below SI after identifica- tion of their receptive fields. The aim of this

The visual claustrum of the cat. III. Receptive field properties.

Abstract: The visual response properties of cells in the cat's dorsocaudal claustrum were studied physiologically Quantitative observations were made of 55 cells, and qualitative observations were made on 228 others The claustral cells formed a physiologically homogeneous population The overwhelming majority were orientation selective, and most also showed a striking preference for long stimuli, their responses summating up to lengths of 40 degrees or more Moving stimuli were always much more effective than stationary ones In other respects, claustral cells were tolerant of wide variation in stimulus features Their responses were about equally brisk to either direction of movement of a properly oriented stimulus, and the velocity of movement was likewise not critical They appeared not to summate across the dimension of their receptive fields orthogonal to the preferred orientation so that narrow or broad slits, or edges, evoked similar responses Dark slits on light backgrounds were as effective as light slits on dark backgrounds Finally, a large majority of cells were driven equally well by either eye These properties of claustral cells differ in several respects from those of their principal targets, cells in layer IV of visual cortex

Object- and self-movement detectors in the ventral nerve cord of the dragonfly

Abstract: 1 Descending, movement-sensitive visual interneurons in the ventral nerve cord of the dragonfly,Anax junius, fall into two categories, based upon their responses to a variety of stimulus patterns One group (object-movement detectors) is sensitive only to movement of small patterns; the other (self-movement detectors) responds maximally to movement of very large patterns or to rotation of the animal in the lighted laboratory 2 Object-movement-detector responses to repeated identical stimuli habituate very rapidly The habituation is region specific; pattern movement elsewhere in the receptive field elicits a renewed response (Fig 3) The habituation is very long lasting and is not subject to dishabituation by mechanical or visual stimulation Self-movement detectors, in contrast, show little or no habituation (Fig 3) 3 Increasing the extent of the stimulus pattern in the direction of motion decreases responses of object-movement detectors slightly and greatly increases self-movement-detector responses (Fig 4) 4 Increasing the length of the advancing edges perpendicular to the line of motion dramatically reduces object-movement-detector responses (Fig 5) Such increases enhance self-movement-detector responses only slightly, unless they result in the pattern occupying especially sensitive regions of the receptive field (Fig 7) 5 Over a wide velocity range, self-movement-detector responses are not dependent on pattern wavelength (Fig 8) 6 These results indicate that the parameter upon which the object/world discrimination is based is different for the two groups of interneurons The critical parameter for the self-movement detectors is the extent of the pattern in the direction of motion, whereas for the object-movement detectors, the critical parameter is the extent of the pattern perpendicular to the direction of motion

The visual claustrum of the cat. II. The visual field map

Abstract: Physiological and anatomical methods were used to study the representation of the visual field in the cat's dorsocaudal claustrum In one set of experiments, the visual receptive fields of claustral neurons were plotted in multiple electrode penetrations In another set of experiments, the termination of the corticoclaustral pathway was examined autoradiographically after the injection of [3H]proline at retinotopically defined sites in the visual cortex Results obtained by the two methods were in close agreement The claustrum was found to contain a single, orderly map of the contralateral hemifield and a small part of the ipsilateral field High elevations are represented caudally and ventrally, low elevations rostrally and dorsally The surface of the claustrum represents the periphery of the visual field, while the vertical meridian lies more ventrally, where the visual claustrum abuts the non-visual part of the nucleus Visual field lines (isoazimuths or isoelevations) are represented as planes in the claustrum The map is unusual in that isoazimuth planes are strongly curved and nested within each other, with peripheral ones enclosing those closer to the vertical meridian This arrangement permits an expanded representation of the periphery compared with what is seen in visual cortex The inputs from areas 17, 18, 19, 21a, and PMLS (posteromedial lateral suprasylvian area) are convergent, each projection retinotopically to the entirety of the claustral map

Branching of sensory axons in the peripheral nerve of the rat

Abstract: The currently accepted concept of a primary sensory cell is a cell that gives rise to a central process which passes through the dorsal root to the spinal cord and a peripheral process which passes to the periphery via a peripheral nerve. If this is correct, then there should be equal numbers of sensory axons in the dorsal root, dorsal root ganglion cells, and sensory axons in the proximal peripheral nerve. The present study obtains these counts in animals in which extraneous axons have been removed from the peripheral nerve and root. The counts indicate that there are approximately 2.3 sensory axons in the dorsal root and proximal peripheral nerve for each ganglion cell in the sacral segments of the rat. We interpret these data as indicating that there is significant branching of sensory axons in the dorsal root and proximal peripheral nerve and thus the generally accepted picture of a dorsal root ganglion cell is not correct for some, perhaps all, of these cells. We offer the speculation that this peripheral branching may be an indication of single sensory neurons having receptive fields in two separate locations, and thus this may be an anatomical explanation for certain types of referred pain.

Receptive field organization of simple cells in cat striate cortex.

Abstract: The receptive field organization of simple cells was studied by analyzing interaction effects between two stationary flashing light stimuli. One stimulus was positioned in the most responsive part of the receptive field to produce activity against which the effects of the other stimulus in various positions of the visual field could be determined.

Vertical organization of neurones accumulating 3H-GABA in visual cortex of rhesus monkey.

Abstract: Electrophysiological and pharmacological studies1–6 indicate that the specific responses of most visual cortical neurones depend on intracortical γ-aminobutyric acid (GABA)-mediated inhibitory processes. GABAergic interneurones have been visualized in all layers of the mammalian cerebral cortex by immunocytochemical methods7,8 and by high-affinity uptake of exogenous 3H-GABA9–11. It is recognized that GABA is synthesized and specifically accumulated by aspinous and sparsely spinous stellate cells, but there is no evidence available to indicate whether the laminar distribution of these cells and their axonal projections are related to the known role of GABAergic inhibitory processes in the generation of responses in visual cortical cells. It would therefore be of value to delineate the intracortical projection of the axons of different types of GABA-releasing neurones in regions of cortex where the receptive field properties of the neurones, and their modification by GABA antagonists, are well known. The selective high-affinity uptake of labelled GABA has been useful in delineating GABAergic systems12: recently, it has been shown that exo-genous 3H-GABA is specifically taken up and transported retrogradely by axons of neurones thought to be GABA-ergic13,14. Using microinjections of 3H-GABA into different layers of the monkey visual cortex, we have examined the pattern of labelled neurones. We report here a bimodal distribution of GABA-accumulating neurones after injection into layers V and VI, with one group of neurones around the injection site and the other directly above, in layers II and III. We provide evidence that the latter neurones are non-pyramidal cells, probably labelled by retrograde axonal transport from the deep layers.

Relation of single unit properties to the oculomotor function of the nucleus of the basal optic root (accessory optic system) in chickens.

Abstract: Single unit recordings in the nucleus of the basal optic root (nBOR) of the accessory optic system in chickens suggest that it has a role in vertical stabilizing eye movements. Cells have unusually large receptive fields and never respond to small stationary stimuli. They respond best to large richly patterned stimuli moving slowly (2–4 °/s) in vertical directions. Cells responsive to upward movement tend to be located in the dorsal portion of nBOR, which projects to motor areas producing upward eye movement, whereas cells responsive to downward movement tend to be located in the ventral portion of nBOR, which projects to motor areas producing downward eye movement; this suggests that these synapses onto oculomotor neurons are excitatory.

Visual response characteristics of neurons in nucleus of basal optic root of pigeons.

Abstract: This study investigated the response characteristics of single cells in the nucleus of the basal optic root (nBOR) of the accessory optic system of pigeons. One hundred and twenty-one nBOR cells were studied and quantitative data from 87 units indicated that they preferred very large random patterned stimuli, and did not respond to stimuli less than 30 ° in diameter. In many cases the receptive field encompassed the entire monocular visual field. nBOR cells were directionally sensitive with approximately 70% preferring motion with an upward vector. They responded to very slow velocities in the range of 0.5 ° to 5.0 ° s−1, and did not adapt to continuous stimulation. Maximal responses occurred to very large randomly patterned stimuli moving slowly in an upward direction. These response characteristics together with the anatomical connections of the nBOR suggest that this nucleus may be involved in processing self-induced visual motion information required for vertical optokinetic stabilization.

Cross‐correlation analysis of the maintained discharge of rabbit retinal ganglion cells.

Abstract: 1. Simultaneous recordings were made from pairs of rabbit retinal ganglion cells. Physiological tests were used to classify the receptive field properties of each cell and the receptive field locations were mapped. 2. The statistical dependence between simultaneously recorded retinal ganglion cells was assessed by cross-correlating the maintained discharge of the simultaneously recorded cells. Cross-correlations from cell pairs in which the constituent cells had non-overlapping receptive field centres were statistically flat, reflecting no statistical dependence. 3. Most cell pairs consisting of transient and sustained concentric cells and having overlapping receptive field centres exhibited a correlated maintained discharge indicative of statistical dependence. The strength of the statistical dependence varied approximately inversely with the degree of overlap between the two cells comprising the cell pair. 4. Cell pairs consisting of two ON-centre cells or two OFF-centre cells and having overlapping receptive field centres possessed incremental cross-correlations which were characterized by a peak centred near zero. Cell pairs consisting of an ON-centre cell with an OFF-centre and having overlapping receptive field centres possessed decremental cross-correlations which were characterized by a valley centred near zero. 5. The results are consistent with the hypothesis that a noise source provides shared input to two or more retinal ganglion cells. Bipolar and photoreceptors are the most likely sources of noise responsible for the statistical dependency between retinal ganglion cells.