Showing papers on "Receptive field published in 1980"

Mathematical description of the responses of simple cortical cells.

Abstract: On the basis of measured receptive field profiles and spatial frequency tuning characteristics of simple cortical cells, it can be concluded that the representation of an image in the visual cortex must involve both spatial and spatial frequency variables. In a scheme due to Gabor, an image is represented in terms of localized symmetrical and antisymmetrical elementary signals. Both measured receptive fields and measured spatial frequency tuning curves conform closely to the functional form of Gabor elementary signals. It is argued that the visual cortex representation corresponds closely to the Gabor scheme owing to its advantages in treating the subsequent problem of pattern recognition.

Somatic submodality distribution within the second somatosensory (SII), 7b, retroinsular, postauditory, and granular insular cortical areas of M. fascicularis.

Abstract: Somatic response properties were determined for over 1,300 neurons isolated within and near the lateral sulci of unanesthetized and unparalyzed cynomolgus monkeys. Somatic stimuli unequivocally activated the majority of units studied in SII (93%) and in cortical fields surrounding SII: area 7b (65%), the retroinsular field (74%), and the granular insula (76%). No activation other than somatic was seen for SII neurons, and noxious somatic stimulation was rarely required. The SII units almost always responded in a rapidly adapting manner to hair or skin stimulation, but not both; however, the submodality distribution seen in SII varied as a function of peripheral receptor locations. Two small zones within SII contained neurons that responded only if the animal actively interacted with the stimulus. In contrast, one-half of the sample of neurons from area 7b unequivocally responded only to somatic stimulation. Although many neurons in the lateral parts of area 7b were vigorously activated by innocuous tactile stimulation, others demonstrated little association with an identifiable somatic submodality, had sluggish responses, required complex, noxious, visual or other non-somatic stimuli for activation, and had labile response properties and receptive fields. Indeed, the responses of some area 7b neurons suggested a possible relationship with the animal's attention towards or anticipation of a noxious or a novel somatic stimulus. Neurons within the retroinsular cortex (Ri), which receives projections from the posterior nucleus (PO), primarily responded to light tactile stimulation of rapidly adapting skin receptors; less than 3% responded to moderate or high threshold mechanical stimulation. The sensitivity to tactile stimulation in Ri closely resembled the responses of SII neurons. Neurons in the granular insula (Ig) often responded to gentle hair deflection within receptive fields covering large areas of the body. Ig and area 7b were the principle loci within the lateral sulcus that contained neurons responding to noxious stimulation. Owing to the great similarity in the somatic response properties within these areas in the awake and unparalyzed animal, the designation of cortical areas could only be made after correlating the recording sites with connectional and cytoarchitectonic analyses in the same animal. Consequently, previous physiological studies may have attributed to SII some of the response characteristics of neurons in neighboring areas.

Organization of somatosensory receptive fields in cortical areas 7b, retroinsula, postauditory and granular insula of M. fascicularis.

Abstract: The boundaries of the second somatic sensory cortex (SII) in primates are difficult to define physiologically because cutaneous stimulation activates several regions around SII that do not receive projections from the ventroposterior nucleus of the thalamus. These cortical regions, which include portions of area 7b, the retroinsular (Ri) and postauditory fields (PA), and the granular insula (Ig) are largely buried within the lateral sulcus and most lie posterior to the caudal end of the insula. The differences in somatic activity in these various cortical fields in the unanesthetized cynomolgus monkey became apparent only after the properties of many neighboring neurons could be compared. Receptive fields for area 7b and Ig neurons were generally large (< 10 cm2), with bilateral, moderately defined boundaries; some neurons in area 7b had receptive fields with labile borders as a function of wakefulness. In contrast, receptive fields for Ri neurons were generally (< 10 cm2 and contralateral, with stable, well-defined boundaries. Taken as an ensemble, the neurons in areas neighboring SII exhibited a very crude topography; but at the level of an individual neuron and its neighbor, there was never a pattern of gradual transition in peripheral receptive field locations between one unit and the next, like that seen in SII. In area 7b, this crude map was organized mediolaterally across the inferior parietal lobule and into the upper bank of the lateral sulcus, with the head represented medially and the lower trunk and hindlimb laterally. In Ri-PA, an anteroposterior organization was noted along the fundus of the lateral sulcus with the head represented anterior to the lower trunk and hindlimb. No organization was apparent in Ig. Additional sensitivity to visual stimuli was noted in the more medial aspects of area 7b that were located on the exposed inferior parietal lobule. Sensitivity to auditory stimuli was principally found in PA and occasionally in Ri. The results, especially from area 7b, are discussed with respect to previous notions about the organization of SII.

Corticopontine visual projections in macaque monkeys

Abstract: These experiments were designed to study the projections to the pons from visual and visual association cortex of monkeys by degeneration staining and horseradisch peroxidase (HRP) methods. When lesions were made in these cortical visual areas, degenerated fibers were found in the rostral dorsolateral area of the pontine nuclei. When HRP was injected among visually responsive cells in this region of the pons, layer V cortical pyramidal cells were labeled. These labeled cells were concentrated most heavily on both banks of the superior temporal and intraparietal fissures, and on the rostral bank of the parieto-occipital fissure. The efferent targets and receptive field properties of these cortical regions are consistent with their possible role in visual guidance of movement.

Somatotopographic organization in the second somatosensory area of M. fascicularis.

Abstract: The second somatosensory area (SII) of awake, untrained cynomolgus monkeys was surveyed with recordings from nearly 1,000 single neurons. A detailed somatotopographic organization could be demonstrated in SII because the majority of these neurons had contralateral, moderate to well-defined receptive fields of < 10 cm2, and because neighboring neurons possessed receptive fields that were only slightly displaced from one another. Different body regions were represented in successive anterior to posterior strips that were oriented across the parietal operculum with an anterolateral to posteromedial slant. Neurons with trigeminal receptive fields were found in the anterior portion of SII; these neurons were the only ones in SII with predominantly bilateral receptive fields (r.f.'s.). Neurons with digit or hand r.f'.s form the largest component of the map, and were located posterior to those with face r.f.s. Most of these neurons had only contralateral activation. The hand and digit region was followed in turn by the arm, the upper and lower trunk, and the hindlimb regions. Although the overall SII orientation was along an anterior-posterior gradient, recordings at individual coronal planes often demonstrated isolated sequences of receptive fields that exhibited a medial-lateral progression. The principle example of this latter gradient was seen in the forelimb region where digits one through five were represented in an overlapping sequence across the parietal operculum. Except for portions of the digit representation, neighboring sequences of neurons in SII do not form a precise topologic map of the body that is comparable to the somatotopic maps observed in areas 3b and 1. The present findings contrast with previous physiological studies of SII in the primate. These discrepancies are discussed in relation to methodological differences and in terms of distinctions used to define the boundaries of SII.

Retinotopic organization of areas 20 and 21 in the cat

Abstract: The retinotopic organization of cat cortex, in the vicinity of areas 20 and 21 as defined by Heath and Jones ('71), was determined using electrophysiological mapping techniques. Although the topography of the visual field representations in this region of cortex is more complex than that found in areas 17, 18, and 19, this region appears to contain four representations of the visual hemifield. The four cortical areas these visual field representations occupy have been labeled 20a, 20b, 21a, 21b. These representations are not as precise as those found in areas 17, 18, and 19; the receptive fields in areas 20a, 20b, 21a, and 21b are larger and there is more scatter in receptive field location among adjacent cells. The upper visual hemifield is emphasized in all four of these areas, but the extent of the representation ranges from just the central 20 degrees found in area 21a to nearly the entire upper visual quadrant found in area 20b. The peak areal magnification factors found in these areas are all at least one order of magnitude less than those found in area 17. The visual field transformations from retina onto cortex in areas 20a, 20b, 21a, and 21b are similar to the types we found in other cortical visual areas, and the significance of these transformations for visual processing is discussed.

Responses of neurons in primate ventral posterior lateral nucleus to noxious stimuli

Abstract: 1. Recordings were made from the caudal part of the ventral posterior lateral (VPLc) nucleus of the thalamus in anesthetized macaque monkeys. In additon to many neurons that responded only to weak mechanical stimuli, scattered neurons were found that responded to both innocuous and noxious stimulation or just to noxious stimulation of the skin. A total of 73 such neurons were examined in 26 animals. 2. Noxious stimuli included strong mechanical stimuli (pressure, pinch, and squeezing with forceps) and graded noxious heat (from 35 degrees C adapting temperature to 43, 45, 47, and 50 degrees C). The responses of the VPLc neurons increased progressively with greater intensities of noxious stimulation. The stimulus-response function when noxious heat stimuli were used was a power function with an exponent greater than one. 3. Repetition of the noxious heat stimuli revealed sensitization of the responses of the thalamic neurons to such stimuli. The threshold for a response to noxious heat was lowered, and the responses to supra-threshold noxious heat stimuli were enhanced. 4. The responses of VPLc neurons to noxious heat stimuli adapted after reaching a peak discharge frequency. The rate of adaptation was slower for a stimulus of 50 degrees C than for one of 47 degrees C. 5. For the six neurons tested, responses to noxious heat were dependent on pathways ascending in the ventral part of the lateral funiculus contralateral to the receptive field (ipsilateral to the thalamic neuron). In two cases, the input to the thalamic neurons from axons of the dorsal column was also conveyed by way of a crossed pathway in the opposite ventral quadrant. In another case, access to the thalamic neuron by way of ascending dorsal column fibers was demonstrated. 6. The thalamic neurons had restricted contralateral receptive fields that were somatotopically organized. Neurons with receptive fields on the hindlimb were in the lateral part of the VPLc nucleus, whereas neurons with receptive fields on the forelimb were in medial VPLc. 7. Ninety percent of the VPLc neurons tested that responded to noxious stimuli could be activated antidromically by stimulation of the surface of SI sensory cortex. It was possible to confirm that many of these cells project to the SI sensory cortex by using microstimulation. Successful microstimulation points were either within the SI cortex or in the white matter just beneath the cortex. 8. We conclude that some neurons in the VPLc nucleus are capable of signaling noiceptive stimuli. The nociceptive information appears to reach these cells through the ventral part of the lateral funiculus on the side contralateral to the receptive field, presumably by way of the spinothalamic tract. The VPLc cells are somatotopically organized, and they are thalamocortical neurons that project to the VPLc nucleus and SI cortex play a role in nociception.

Magnification, receptive-field area, and "hypercolumn" size in areas 3b and 1 of somatosensory cortex in owl monkeys.

Abstract: 1. Several features of the two complete and separate representations of the contralateral body surface in cortical areas 3b and 1 of somatosensory cortex in owl monkeys were quantitatively studied. 2. Area1 magnification factors for different body regions in the two representations were obtained. The glabrous hand and foot regions were found to occupy nearly 100 times more cortical tissue per unit body-surface area than the trunk or upper arm. 3. In the representations of the hand digits, inverse magnification was linearly related to distance from the digit tips. 4. Receptive-field size was found to be proportional to inverse magnification over the entire body-surface representation as well as over the local region of the glabrous hand digits. The relation between receptive-field size and inverse magnification appears to be linear; specification of one would specify the other over the representation in one area. 5. By relating receptive-field overlap to distance separating recording sites, the area of cortex presumed to receive all fibers from any given receptive field was obtained and found to be independent of the body surface represented. Such an area of somatosensory cortex, about l1.5 mm in diameter, may be akin to the “hypercolumn” proposed for primary visual cortex (6).

Location and properties of dorsal horn neurons at origin of spinoreticular tract in lumbar enlargement of the rat

Abstract: 1. Spinoreticular tract neurons at the rat lumbar cord level were identified by antidromic activation following stimulation at mainly pontine and mesencephalic levels. These units, which were found in the dorsal half of the cord, could be separated into two groups according to their spinal location, electrophysiological properties, and their central projections. 2. Units in the dorsolateral funiculus nucleus projected mainly to the cuneiformis area and adjacent structures with frequent bilateral projections. They had the slowest conduction velocities, sometimes in the unmyelinated range. Generally, they were driven only by stimulation of subcutaneous and/or deep structures. 3. Neurons located in the dorsal horn mainly projected contralaterally to pontine and mesencephalic levels. their conduction velocities and the electrophysiological properties were identical to those observed for the rat spinothalamic tract (22). Almost all (86%) had clear cutaneous sensitivity and generally large receptive fields: 40% responded to nonnoxious and noxious mechanical cutaneous stimuli and frequently to noxious radiant heat, 26% were exclusively excited by light tactile stimuli, and 20% required noxious cutaneous mechanical stimulation for activation. There was a good correlation between responses to natural and transcutaneous electrical stimulation: units driven by noxious mechanical stimuli received A-delta- and/or C-fiber inputs. The remaining units (14%) had more complex receptive fields associated with both excitatory and inhibitory inputs originating from a single peripheral area. 4. The functional heterogeneity of the rat spinoreticular tract is reminiscent of that demonstrated for the rat and monkey spinothalamic tracts. Similarly, the rat spinoreticular neurons are under the influence of descending inhibitory controls originating from the nucleus raphe magnus and bulbar reticular formation. 5. Responses of the rat spinoreticular tract neurons are consistent with the involvement of this pathway in the transmission of messages of both innocuous and noxious origins.

Neurones responding to noxious stimulation in VB complex and caudal adjacent regions in the thalamus of the rat.

Abstract: (1) 163 cells responding to mechanical cutaneous stimulation have been recorded in VB complex and caudal adjacent region in rats anaesthetized with a mixture of 2/3 N2O--1/3 O2 and 0.5% halothane. (2) 51 cells were exclusively activated by non-noxious cutaneous stimuli applied to restricted and contralateral receptive fields (RF) and had the classical characteristics of "lemniscal" responses. 93 cells responded only to noxious mechanical stimuli (N cells) and had either uni- or bilateral receptive fields. 19 cells responded both to noxious and non-noxious stimuli (NnN cells). (3) When tested with intense electrical stimuli applied transcutaneously or on the sural nerve, N and NnN cells responded with a late irregular discharge. Poststimulus histograms obtained in one-third of these units revealed that the late component was consistent with a C fibre input; some of responses were consistent with A delta fibre input. NnN cells also had a short latency discharge probably due to A alpha fibre involvement. (4) When tested with other intense stimuli such as noxious radiant heat or noxious visceral stimulation induced by intraperitoneal injection of bradykinin, N and NnN cells were strongly activated. (5) The different kinds of cells were scattered in VB and PO and no significant differences were found between cells recorded in VB and caudal adjacent region (PO); however, a rostrocaudal organization of the cells, according to the location of their RF on the caudal or rostral part of the body, was clear not only for the Nn cells but also for N and NnN cells.

A physiological analysis of subcortical and commissural projections of areas 17 and 18 of the cat.

Abstract: 1. The corticotectal, corticothalamic and commissural projections of areas 17 and 18 of the cat have been examined using electrical stimulation techniques. 2. In both area 17 and area 18, almost all corticotectal neurones are C cells and have binocular receptive fields. Some of these cells respond equally well to both small moving spots and elongated stimuli, while others only respond to stimuli of restricted length (cf. Palmer & Rosenquist, 1974). Both types are highly direction-selective. A third type of corticotectal C cell responds optimally to long edges or bars and shows only weak direction selectivity. Corticotectal cells generally have fast conducting axons and the majority are encountered in lamina V. About 25% of all cells recorded in lamina V can be antidromically activated from the superior colliculus. 3. Striate and parastriate cells efferent to the thalamus can have either S or C type receptive fields. Corticothalamic S cells are the most common type of efferent cell in lamina VI and have more slowly conducting axons than C cells. Efferent S cells are almost always direction-selective and about half have binocular receptive fields. 4. It is suggested that there may be at least three subgroups within the corticothalamic cells: lamina V C cells project to the pulvinare complex (the same cells may also send axons to the superior colliculus), lamina VI C cells project to the perigeniculate nucleus and lamina VI S cells provide the cortical input to neurones within the lateral geniculate nucleus. 5. In contrast to the corticotectal and corticothalamic projections, the receptive fields of cells projecting through the corpus callosum forth a heterogenous group. All major striate and parastriate receptive field classes are efferent to the contralateral cortex. Their receptive field centres are located close to the vertical mid line and most cells respond best to stimuli moving towards the ipsilateral visual hemifield. Efferent neurones are mostly encountered in lamina III, within about 1mm either side of the 17-18 border zone. 6. Cells orthodromically excited after commissural stimulation have mostly C or B type receptive fields. Unlike efferent callosal neurones, orthodromically activated cells are encountered up to 3 mm into area 18 and can have receptive fields located up to 9 degrees from the vertical mid line. 7. The results are discussed with regard to the possible functional significance of each of the corticofugal pathways.

The superior colliculus and movements of the head and eyes in cats

Abstract: 1. The superior colliculus has been studied in alert cats which were restrained and whose head and eye movements were monitored. 2. Microstimulation within the rostral part of the colliculus, which represents the central 25 deg of the visual field, evokes saccadic eye movements that carry the area centralis to that region of visual space previously occupied by the receptive fields of the cells that were stimulated (‘foveation’). These saccades are not generally accompanied by a movement of the head. 3. At more caudal locations the visual receptive fields of collicular neurones lie at a greater eccentricity relative to the area centralis than the maximum possible deviation of the eyes from the central position in normal circumstances. At these sites electrical stimulation produces a combined movement of the head and eyes whose co-ordination is identical to that of natural gaze changes in response to novel stimuli. Prolonged stimulation results in the addition of further co-ordinated eye-head movements. 4. The addition of a movement of the head does not increase the area of visual space that may be foveated in a single gaze change. Movements of the head are compensated by the vestibulo-ocular reflex. The visual receptive fields of cells at more caudal locations cannot be foveated by a single gaze change. 5. A third class of response to electrical stimulation is also occasionally found in the caudal part of the colliculus. The head movement often begins before an accompanying eye movement and continues smoothly for the entire stimulation duration or until limited by the range of mobility. 6. Electrical microstimulation was never found to produce so-called ‘goal-directed eye movement, in which the eyes move, in a single saccade, to a fixed orbital position regardless of their starting position. 7. Ninety-nine cells were recorded from the superior colliculus and classified into four types based on their responses, or lack of responses, during or preceding eye and head movements. Type 1 cells did not show changes in activity prior to gaze changes Type 2 cells were inhibited prior to and during eye movements. Cells discharging before normal saccadic eye movements (type 3) were found only in the rostral part of the colliculus. Cells discharging before head movements (type 4) were found only in the caudal part. 8. These results are discussed with respect to the production of gaze changes in the cat.

Rod and cone inputs to bipolar cells in goldfish retina

Abstract: Five morphological types of bipolar cells which make synaptic contact with rods and cones are distinguished in the retina of adult goldfish (Carassius auratus) by characteristics readily observable in the light microscope. Cells were designated type a or type b according to whether their axons terminate in the distal part (sublamina a) or proximal part (sublamina b) of the inner plexoform layer, respectively. Analysis of serial semi-thin sections of Golgi-impregnated cells demonstrates that each subtype of bipolar contacts rods and a characteristic set of chromatic subtypes of cones: types a1 and b1 cells contact rods and red-sensitive cones, while types a2, b2 and b3 contact rods and red- and green-sensitive cones. Comparison with published descriptions of cells stained with Procion Yellow after intracellular recordings had been made suggests that type a cells should be off-center types and type b on-center. Furthermore, it is suggested that the receptive fields of cell types a1 and b1 should be non-color-coded, and those of a2, b2, and b3 color-coded.

Laminar distribution of receptive field properties in the primary visual cortex of the mouse

Abstract: We studied the receptive field properties of single neurons in the primary visual cortex (area 17) of the mouse and the distribution of receptive field types among the cortical laminae. Three basic receptive field types were found: 1) Cells with oriented receptive fields, many of which could be classified as simple or complex, were found in all layers of the cortex, but occurred with greater frequency in layers I1 and I11 and less commonly in Layer IV. 2) Cells with non-oriented receptive fields had ON, OFF, or ON-OFF centers; they were found in all layers but were predominant in layer IV. Two subclasses of non- oriented receptive fields were characterized based on their responses to stationary and moving stimuli. One group of cells with non-oriented receptive fields responded vigorously with sustained firing to stationary flashing stimuli, and also responded well to moving stimuli over a wide range of stimulus velocities. A second group of non-oriented cells, termed motion-selective, responded poorly or not at all to stationary stimuli and responded optimally to moving stimuli over a restricted range of velocities. 3) A distinct group of neurons, termed large field, non-oriented (LFNO) cells, were found almost exclusively in layer V. LFNO cells had receptive fields that were larger than those of the other two major classes at all visual-field locations; they also had higher rates of spontaneous activity and responded to higher stimulus velocities than the other classes. In these respects, LFNO cells resembled the layer V cells of area 17 in the cat and the layer V and VI cells of area 17 in the monkey that project to the superior colliculus. We injected horseradish peroxidase into the superior colliculus, and determined that corticotectal cells in the mouse were also located in layer V, the layer where we recorded LFNO cells. Additional evidence that some LFNO cells project to the superior colliculus was provided by preliminary experiments in which we stimulated the superior colliculus and antidromically activated cortical cells with LFNO receptive fields. Neurons with LFNO receptive fields thus constitute a class that is functionally distinct, with cell bodies that are located in a single layer (V) of area 17 in the mouse. The aggregation of neuronal cell bodies and their processes into laminae is one of the most striking of the morphological features that characterize cerebral cortex. Laminae in a given cortical region differ from one another in the size, shape, number, and packing den- sity of the neurons they contain, and regions of cortex may be differentiated from one an- other in part on the basis of variations in these features from one area to the next (Brod- mann, '03; Campbell, '03; Vogt, '03). In recent years, a number of approaches have been used in the study of the visual cortex to provide evidence for the proposition that cortical lam- ination has functional significance. Anatomi- cal studies in cat and monkey have convinc- ingly demonstrated that afferents to visual

Visual responses of thalamic neurons depending on the direction of gaze and the position of targets in space.

Abstract: Visual receptive field properties of neurons in the region of the thalamic internal medullary lamina were studied in alert cats while they fixated in various directions. In slightly more than 50% of the cells, the responsiveness of the cells was found to depend on the location of the stimulus with respect to the head-body axis (stimulus absolute position). A cell could ignore a stimulus outside its absolute field even if it was well placed within its receptive field. Three types of neurons were distinguished. Neurons with small central receptive fields were tonically activated when the animal fixated the stimulus in one half of the screen (usually contralateral). The firing rate of these cells was related to the stimulus absolute position measured along a preferred axis. Similarly, neurons with large receptive fields fired as a function of stimulus absolute position but stimulus fixation was not required. Neurons with eccentric fields responded to stimuli located in a target area defined in head-body coordinates. Such cells gave presaccadic bursts with eye movements terminating in the target area. The conclusion proposed is that neurons exist which code visual spatial information in a non-retinal frame of reference. This coding takes place at the time of stimulus presentation. Its role may be seen in the initiation of visually guided movements.

Orientation bias of cat retinal ganglion cells.

Abstract: Kuffler1 described the receptive fields of cat retinal ganglion cells as having a concentric arrangement. This has usually been taken to mean that they are approximately circular in form (see, for example, ref. 2). Hammond3 tested the circularity of the centre component of receptive fields by plotting a contour of isosensitivity to a small flashed spot. He concluded that centres were often elliptical (average ratio of major to minor axis 1.23) and that more than 50% of the recorded cells had the major axis oriented within ±20° of the horizontal. Such data are important for discussions4 of the neurophysiological basis of the ‘Oblique effect’ (reduced visibility for periodic grating patterns when oriented away from the vertical or horizontal) observed in psychophysical experiments on humans because subcortical units are often assumed to be orientationally unbiased. Orientation selectivity is a prominent attribute of visual cortical neurones5 so analysis has usually emphasized the distribution of orientation selectivity at that level6–8. The results presented here redirect attention to the retinal level since they reveal a previously unsuspected systematic relation between orientation bias of ganglion cells and their location relative to the area centralis.

The visual properties of rat and cat suprachiasmatic neurones

Abstract: 1. Responses of single neurones in the suprachiasmatic nuclei (SCN) were recorded in the anaesthetized rat and cat. Visual SCN units in both species were predominantly present in the caudal half of the nucleus. The large majority could be classified as either tonically suppressed or tonically activated according to whether an increase in diffuse adaptation luminance respectively decreased or increased their mean discharge rate. 2. For both the cell types the maintained discharge at different luminance levels was a monotonically decreasing or increasing function over a large range of light intensities. In both species the threshold for luminance-dependent maintained discharge was high (>−1 log cd·m−2). The observation of either cell type was independent of the phase of the circadian cycle but it was not established whether the same held true for the intensity-response relations. 3. A small proportion of suppressed cells in the rat SCN reflected the state of retinal adaptation in their firing rate. After light adaptation these cells attained their steady state dark discharge only very slowly. 4. The receptive fields of cat SCN cells tended to be large (> 20°) without a clear antagonistic centre-surround organization. It is proposed that the receptive fields of SCN are the result of the convergence of retinal input from tonic W-cells. 5. It is concluded that their characterization as detectors of diffuse temporal luminance gradients makes visual SCN neurones particularly suitable for their function in the photic entrainment of circadian rhythms. This functional specialization is probably common to both the direct retinofugal projection and the indirect visual projection via the ventral lateral geniculate nucleus to the SCN.

Ordinal position and afferent input of neurons in monkey striate cortex

Abstract: From the extracellular recording of single units in the monkey striate cortex and electrical stimulation at two selected sites in the optic radiations it was possible to estimate 1) the ordinal position of striate neurons (i.e., whether they received a monosynaptic, disynaptic or polysynaptic input from the thalamus) and 2) the nature of the afferent input to these neurons (i.e., whether it came from the magnocellular or parvocellular subdivision of the lateral geniculate nucleus (LGN)). Based on receptive field properties six major classes of striate neuron were identified--three which lacked orientation specificity (the ON-center, the OFF-center, and the ON/OFF or nonoriented (N-0) receptive fields) and three with orientation specific responses (the S, the C, and the B categories of receptive field). Units lacking orientation specificity were concentrated in laminae 4A, 4C beta and 6 while, for the cells with orientation specificity, C cells were found in laminae 4B and 6, B cells in 2/3 and 5, and S cells predominantly in laminae 2/3, 4C alpha, and 5. The results of electrical stimulation indicated that cell-to-cell transmission time in the monkey striate cortex is 1.5 msec, and latency measures showed that cells with a monosynaptic drive from the thalamus were confined to laminae 4 and 6 while disynaptically driven cells were found principally in upper lamina 4 (4A and 4B). No cell class was identified exclusively with a given ordinal position and there were many types of potential first-order neurons. The conduction time from one stimulating electrode to the next in the optic radiation was used to identify the afferent input to each striate neuron. The input to color-coded neurones was found to come exclusively from parvocellular layers while the C cells and two subclasses of the S cell (S2 and S3) were driven predominantly by the magnocellular subdivision. For other cell types (those with ON-center, N-0, and S1 receptive fields) the input came from either type of LGN neuron. The laminar distribution of neurons receiving a direct input from the magnocellular and parvocellular streams is in accord with the results of anatomical studies into the site of termination of the LGN input. The cell types receiving these direct inputs vary in the two streams so that the parvocellular input terminates on cells with ON-center and N-0 receptive fields in lamina 4C beta while the magnocellular input goes to cells with S, ON-center, N-0, and C receptive fields in lamina 4C alpha and the lower part of 4B. Consideration is given to the influence of these results on models for neural processing in monkey striate cortex and a comparison is drawn with the results of similar studies in the cat.

Three groups of cortico-geniculate neurons and their distribution in binocular and monocular segments of cat striate cortex.

Abstract: Among 409 neurons recorded from binocular and monocular segments of the cat striate cortex, 91 were identified as cells (C-G cells) projecting to the dorsal lateral geniculate nucleus (LGN) on the basis of antidromic activation from LGN and of histological localization of cortical layer VI. The axonal conduction velocity of these C-G cells was calculated from differences in latency between antidromic responses to electrical stimulation of LGN and the optic radiation. According to this velocity, 70 C-G cells from the binocular segment could be classified as fast (13--32 m/sec), intermediate (3.2--11 m/sec) and slow (0.3--1.6 m/sec) cells. The fast cells (47% of the total) were spontaneously active and had receptive fields of complex type. Histologically they were located mostly in the upper half of layer VI. The intermediate cells (31%) were mostly simple. The slow cells (21%) were completely silent, not driven by visual stimuli, and located mostly in the lower VI. From the monocular segment of the cortex, the intermediate cells could not be recorded, while the other two groups of cells were sampled with the same frequency as from the binocular segment. These findings suggest an existence of three functionally distinct groups of C-G cells and a possible participation of the intermediate cells in binocular vision.

Spatial processing of visual information in the movement-detecting pathway of the fly

Abstract: 1. Spatial processing of visual signals in the fly's movement-detecting pathway was studied by recording the responses of directionally-selective movement-detecting (DSMD) neurons in the lobula plate. The summarized results pertain to a type of neuron which preferentially responds to horizontal movement directed toward the animal's midline. Three kinds of visual stimuli were used: moving gratings, reversing-contrast gratings and reversing-contrast bars. 2. Contrast-sensitivity functions were measured for reversing-contrast gratings. With horizontally-oriented gratings, sensitivity is maximum at the lowspatial-frequency end and falls off toward high frequencies. With vertically-oriented gratings, sensitivity is maximum at an intermediate spatial frequency (Fig. 7). These results are consistent with a neural organization in which the DSMD neuron receives its input through an array of small-field (“ sampling”) units, each unit having a receptive field comprising an excitatory centre and horizontally-extending inhibitory flanks (Fig. 17). 3. Threshold contrast functions were measured for reversing-contrast bars (Figs. 11 and 12). The results for horizontally-oriented bars differ from those for vertically-oriented bars in a way that is consistent with the hypothesized neural organization. 4. Response to horizontally-moving, verticallyoriented gratings of various spatial frequencies were measured (Figs. 13 and 14) and the results used to infer the azimuthal angle\(\widetilde{\Delta \phi }\) between the visual axes of sampling units participating in directionally-selective movement detection (Fig. 18). At a mean luminance of 10 cd/m2, the inferred value of\(\widetilde{\Delta \phi }\) is approximately equal to the angle between the visual axes of adjacent ommatidia of a horizontal row, in the frontal eye region (Figs. 14, 18). 5. When the level of ambient light is decreased, the response characteristics of the DSMD neuron change in a way which suggests that, within the eye, the neural representation of the visual scene becomes coarser than the ommatidial mosaic. When mean luminance is lowered by 3 log units (from 10 cd/m2 to 0.01 cd/m2) the altered response characteristics suggest neuronal modifications such that the excitatory centres of the sampling units' receptive fields become 50% wider (Figs. 7 and 17), the inhibitory flanks become weaker and more diffuse, and\(\widetilde{\Delta \phi }\) increases by 30% (Figs. 14 and 18). Neuronal mechanisms that might mediate such changes are proposed and discussed. 6. The experimentally-measured characteristics of the DSMD neuron are compared with theoretically-predicted characteristics of an ideal movement detector, designed for optimum performance. This comparison suggests that the fly's movement-detecting pathway prefilters visual signals in such a way as to extract the most reliable movement cues, and that it analyzes the filtered information in a way that achieves maximum directional selectivity. The characteristics of the movement-detecting pathway vary with luminance in a way that ensures the best attainable performance at each level of ambient light (Fig. 21).

Suppression of cat retinal ganglion cell responses by moving patterns.

Abstract: 1. Action potentials were recorded from single fibres in the optic tract of anaesthetized cats. 2. A sectored disk or 'windmill', concentric with the receptive field, was rotated about its centre to cause local changes in illumination throughout the receptive field without changing the total amount of light falling on the receptive field centre or surround. 3. A cell's response to a flashing test spot centered on its receptive field was measured both while the windmill was stationary and while it rotated. While the windmill rotated, the test spot evoked a smaller average number of spikes than while the windmill was stationary. 4. The induction in response occurred in both on-centre and off-centre cells and in both X-cells and Y-cells, though the reduction in response was smaller in X-cells. 5. Surround responses, evoked by an eccentric stimulus, were also reduced by a moving peripheral pattern. 6. Suppression was graded with the contrast of the moving pattern. 7. Gratings too fine to be resolved by the receptive field centre could suppress the response of Y-cells. This suggests that the local elements responsible for the suppression are smaller than the receptive field centres of Y-cells. 8. Response suppression started within the 100 msec of the onset of pattern motion.

Spectro-temporal receptive fields of auditory neurons in the grassfrog. III. Analysis of the stimulus-event relation for natural stimuli.

Abstract: The stimulus-event relation of single units in the auditory midbrain area, the torus semicircularis, of the anaesthetized grassfrog (Rana temporaria L.) during stimulation with a wide ensemble of natural stimuli, was analysed using first and second order statistical analysis techniques. The average stimulus preceding the occurrence of action potentials, in general, did not prove to give very informative results. The second order procedure consisted in the determination of the average dynamic power spectrum of the pre-event stimuli, following procedures as described elsewhere (Aertsen and Johannesma, 1980' Aertsen et al., 1980). The outcome of this analysis was filtered with the overall power spectrum of the complete stimulus ensemble in order to correct for its non-uniform spectral composition. The "stimulus-filtered" average pre-event dynamic spectrum gives a first indication of the "spectro-temporal receptive field" of a neuron under natural stimulus conditions. Results for a limited number of recordings are presented and, globally, compared to the outcome of an analogous analysis of experiments with tonal stimuli.

Visuo-oculomotor properties of cells in the superior colliculus of the alert cat.

Abstract: Visual responses and eye movement (EM) -related activities were studied in single units of the superior colliculus (SC) of alert cats. Spontaneous EMs were encouraged by training. Throughout the SC (i.e., in intermediate and deep layers as well as in superficial layers), units were found to respond well to visual stimuli. Strong and consistent responses could be elicited by very dim, low-contrast stationary stimuli. Visual responses varied from phasic to tonic; some units responded tonically to stationary stimuli in the center of the receptive field, and phasically to peripheral stimuli. Many cells responded more vigorously to moving than to stationary stimuli, but very few responded exclusively to stimulus movement. The vast majority of cells were directionally selective. A small number of units were sensitive to the absolute, as well as the retinal, position of visual stimuli. These cells were activated by visual stimuli which fell in the receptive field only if the cat's gaze was fixated on one half of the screen. It seems that these cells must receive information about both eye position and the retinal (receptive field) position of the stimulus. It is possible that they reflect coding of target location within a head (or body) frame of reference. EM-related units were of two types: (1) about 20% of the sample responded prior to spontaneous or visually-triggered EMs, and (2) another 10% (or more) responded with, but not before, EMs. Some cells in the second group discharge almost synchronously with EMs and, thus, cannot plausibly be said to respond to the movement of images across the retina. All cells in the first group were directionally selective. The percentage of EM-related cells in the deep layers of SC is lower in cat than in monkey. Possible reasons for such differences are discussed.