Showing papers on "Orientation column published in 1979"

Morphology and intracortical projections of functionally characterised neurones in the cat visual cortex

Abstract: The neuronal structure and connectivity underlying receptive field organisation of cells in the cat visual cortex have been investigated. Intracellular recordings were made using a micropipette filled with a histochemical marker, which was injected into the cells after their receptive fields had been characterised. This allowed visualisation of the dendritic and axonal arborisations of functionally identified neurones

The striate projection zone in the superior temporal sulcus of Macaca mulatta: location and topographic organization.

Abstract: In the rhesus monkey, the caudal portion of the superior temporal sulcus (STS) receives a direct projection from lateral striate cortex, the striate are representing central vision. The present study was undertaken to determine whether STS also receives a direct projection from areas of striate cortex representing peripheral vision, with the intent of defining the entire striate projection zone in STS as well as providing information regarding a possible topographic organization within this secondary visual area. A series of five rhesus monkeys was prepared with unilateral lesions of lateral, posterior, or medial striate cortex, such that, collectively, the lesions in the series included all of striate cortex with little or no invasion of prestriate cortex. The monkeys were sacrificed seven days after surgery and their brains were processed by the Fink-Heimer procedure. An analysis of the distribution of terminal degeneration within STS indicated: (1) All areas of striate cortex project to a restricted region along the caudal portion of STS. The ventral limit of this region can be demarcated by an imaginary line connecting the ventral tips of the lunate and intraparietal sulci; from this limit the region extends dorsocaudally for approximately 12 mm to the point at which STS frequently bifurcates, sending one spur forward into the inferior parietal lobule. (2) Within this portion of STS there is an orderly mapping of the visual field; progression from central vision to the far periphery is represented by a progression down the posterior bank of STS and continuing along the entire floor, or insula-like portion, of the sulcus. (3) Projections from striate cortex to STS terminate predominantly in layer IV and the deep part of layer III. (4) There is a distinctive pattern of myelination contained within the striate projection zone of STS. These anatomical findings concerning the striate projection zone of STS in the rhesus monkey are remarkably similar to those that have been described for the middle temporal visual area (MT) in New World monkeys, and thus support earlier proposals that the two areas are homologous.

Geometry of orientation columns in the visual cortex

Abstract: The optimal direction of lines in the visual field to which neurons in the visual cortex respond changes in a regular way when the recording electrode progresses tangentially through the cortex (Hubel and Wiesel, 1962). It is possible to reconstruct the field of orientations from long, sometimes multiple parallel penetrations (Hubel and Wiesel, 1974; Albus, 1975) by assuming that the orientations are arranged radially around centers. A method is developed which makes it possible to define uniquely the position of the centers in the vicinity of the electrode track. They turn out to be spaced at distances of about 0.5 mm and may be tentatively identified with the positions of the giant cells of Meynert.

Dimensions and properties of end-zone inhibitory areas in receptive fields of hypercomplex cells in cat striate cortex.

Abstract: 1. Subregions in the receptive fields of hypercomplex cells have been examined by a variety of quantitative methods with particular reference to the dimensions and properties of the end-zone inhibitory areas. These data have made it possible to construct detailed maps of the receptive-field organization of the two types of hypercomplex cell (I and II). 2. The spatial extent of the end-zone inhibitory area is much greater than that responsible for discharge-region excitation. End-zone inhibition is, however, position dependent, the part of the area causing maximal inhibition lying precisely along the line of the most responsive part of the discharge region and just beyond its lateral border. Spatial summation of end-zone inhibition takes place along the line of its optimal stimulus orientation. 3. Some simple and complex cells may have hypercomplex-type length-response curves in the nonpreferred direction of stimulus movement and vice versa for some hypercomplex cells. Whether these response patterns are due to the presence of directionselective end-zone inhibition or not remains to be determined. While end-zone inhibition may be direction selective, it appears that it is usually nondirectional. Even when discharge region excitation is itself completely direction selective, the end-zone inhibition may be equally effective in both directions. Hence end-zone inhibition appears to be independent of the mechanism responsible for the direction selectivity of the discharge region. 4. End-zone inhibition is stimulus orientation dependent, being maximal when the orientation is the same as the orientation that is optimal for the discharge region. When the stimulus is rotated away from the optimal, the strength of the inhibition progressively declines, falling to zero at 90’ to the optimal. This property distinguishes end-zone inhibition from side band inhibition since the latter is not orientation sensitive. 5. There may be considerable, or even total, spatial overlap between dischargeregion excitation and end-zone inhibition, the spatial summation required for excitation being much less that that required to produce an inhibitory effect. The onset of inhibition in the length-response curve indicates that the effects of the spatial summation of inhibition now exceeds those of dischargeregion excitation.

Ordinal position of neurons in cat striate cortex.

Abstract: I. The ordinal, or serial, position of different types of striate neurons was assessed from their latencies to electrical stimulation of the optic radiations in paralyzed cats anesthetized with N,O/O, (70/30%). 2. The distribution histogram for response latencies of striate neurons to electrical stimulation in the optic radiations shows three broad peaks. These peaks become sharper if the stimulating site is moved from a low point (OR,) to a high point (OR,) in the optic radiations. It is argued that each peak represents a population of cells lying at a different ordinal, or serial, position within the cortical pathway, i.e., receiving a mono-, di-, or polysynaptic excitatory input from the thalamus. 3. The duration separating the peaks, of the order of 1.0 ms, is then taken as the transmission time for conduction of the nervous impulse from one cortical cell to the next. Confirmatory evidence for this value of the cell-to-cell transmission time comes from the measurement of interspike intervals in cortical cells that responded with multiple spikes to electrical stimulation. 4. From the peaks in the distribution of OR, latencies, boundaries have been established to arrive at an ordinal position for 131 cells classified as S, Sh, C, B, or cells with nonoriented or concentric receptive field (N-O and cone), following the terminology of Henry (14). Four ordinal groups were distinguished: group M comprised cells receiving an exclusive monosynaptic input from the thalamus, group C1+,i consisted of cells exhibiting a convergence of excitatory inputs, one of which was monosynaptic; group D was composed of cells in which the lowest order input was disynaptic. Cells were placed in group P if they were driven from the thalamus through three or more synapses. Examination of the distribution of different cell types for these various ordinal groups revealed that no particular cell type was exclusively associated with a single ordinal position. In particular, a large proportion of S-, Sh-, C-, and N-O and cone cells showed a monosynaptic input from the thalamus (groups M and Cl+,)). 5. For the three classes of cell, S, Sh, and C, with sufficient numbers in groups MY cl+n~ and D, a search was made for differences in response properties associated with the various ordinal groups. The properties examined included ocular dominance, direction selectivity, orientation specificity, and receptive-field size. With the exception of the C-cell, which showed a difference of direction selectivity in groups M and Cl+,), we observed no systematic changes in the response properties with differences in ordinal position. 6. For most cell types in cat striate cortex there are examples of neurons receiving a monosynaptic input. It is difficult to reconcile these findings with a hierarchical model for the processing of visual information. It is proposed that these cells are first-order elements of different streams running in parallel within the cortex and that this multiplicity of streams may be associated with the diversity of outputs leaving the striate cortex.

The afferent connections and laminar distribution of cells in the cat striate cortex.

Abstract: A laminar distribution of different functional cell types in the striate cortex of the cat is drawn up from the visual responses of single cells recorded in 64 electrode penetrations in 38 cats. In summary, S cells were found to be concentrated in laminae 4 and 6; SH cells in laminae 2, 3 and 4; C cells in laminae 5 and lower 3; B cells in laminae 3 and upper 5 and cells with non-oriented receptive fields in lamina 4. In addition, the nature of afferent innervation to striate neurons was derived from the latency of the orthodromic response to electrical stimulation in the optic chiasm and optic radiations in 19 cats. An analysis of latency values allowed the afferent innervation to a cell to be classed as belonging either to fast or slow conducting streams in the population of dLGN axons and also permitted a decision to be made on whether or not the afferent path passed directly to the cell. Direct afferent innervation from the dLGN was not found to be confined to a single class of striate neuron. Instead, examples of cells with S, SH, C, B and non-oriented receptive fields all had orthodromic latencies that met the requirement for direct innervation. Instances of cells with orthodromic latencies suggestive of indirect innervation were also found for most receptive field classes but these cells were encontered less frequently than those with a direct afferent input. It is argud that a variety of different cell types may act as first order neurons in the striate cortex and that cells occurring at later stages in the sequence of cortical processing may have been incompletely studied because they are more difficult to stimulate either visually or electrically.

The rabbit and the cat: a comparison of some features of response properties of single cells in the primary visual cortex.

Abstract: Receptive field characteristics of single cells in primary visual cortex of rabbit were studied. Seventy-two percent of cells were found to be orientation selective, and the remainder had concentric, uniform, movement selective or pure direction selective receptive fields. Single cells were also recorded from primary visual cortex of cat to permit a comparison of visual cortical organization in cats and rabbits. Laminar organization of receptive field types was observed in rabbits which was similar in most respects to that described in the cat. Although the major categories of orientation selective cells (simple, complex, hypercomplex) were similar for both cat and rabbit, many differences emerged: (I) tuning of orientation selectivity was narrower in cats than in rabbits; (II) units which preferred oblique orientations were less frequently represented in rabbits than in cats; (III) orientation preferences appeared to be arranged in cluster in rabbit cortex; in rabbits we found no evidence of the columnar organization of orientation selectivity which characterizes cat visual cortex. A comparison of our data with those previously reported for mouse, rat, hamster and opossum visual cortex suggest that mammals in which a significant proportion of visual cortical cells are not orientation selective have in common certain patterns of cortical organization involving a less precise and less specialized representation of stimulus orientation.

The retino-geniculo-cortical pathway in Callithrix. II. The geniculo-cortical projection.

Abstract: After monocular injections of tritiated tracer precursors and transneuronal transport of tritiated compounds, a continuous band of radioactivity in layer IV of striate cortex of Callithrix jachus (Callithricidae, New World primates) indicated a complete desegregation of the crossed and uncrossed retino-cortical pathways. Comparison with the organization of these pathways in other primates suggests that a segregation of the retino-cortical pathways of opposite ocularities into alternating ocular dominance columns in striate cortex has developed independently in the different primate lines. The significance is discussed of the weak labeling of the region of area 17 representing the central retina as compared to the representation of the peripheral retina.

14C-deoxyglucose mapping of orientation subunits in the cats visual cortical areas.

Abstract: The orientation domain in the cortical visual areas of anesthetized cats has been investigated by employing the 14C-Deoxyglucose technique (Sokoloff et al., 1977). Orientation subunits (OS) are seen in the first (V1), the second (V2) and the third visual area (V3) as well as in the visual areas of the suprasylvian sulcus. In the latter regions OS are less elaborated than in V1, V2, and V3. The OS are continuous through all cortical layers; in V1 however, only weak label is detected in layer 4C. In V1, V2, and V3 the width of the OS is about 0.4 mm and the average distance between two OS centers is 0.9 mm. The spatial pattern of the OS seems to be more regular in the visual field periphery than in regions representing the vertical meridian.

Neurophysiological mechanisms of recovery from visual cortex damage in cats: properties of lateral suprasylvian visual area neurons following behavioral recovery.

Abstract: Damage to visual cortical areas 17, 18, and 19 in the cat produces severe and long-lasting deficits in performance of form and pattern discriminations. However, with extensive retraining the animals are able to recover their ability to discriminate form and pattern stimuli. Recent behavioral experiments from this laboratory have shown that a nearby region of cortex, the lateral suprasylvian visual area (LS area), plays an important role in this recovery (Wood et al., 1974; Baumann and Spear, 1977b). The present experiment investigated the underlying neurophysiological mechanisms of the recovery by recording from single neurons in the LS area of cats which had recovered from long-term visual cortex damage. Five adult cats received bilateral removal of areas 17, 18, and 19. They were then trained to criterion on two-choice brightness, form, and pattern discriminations. Recording from LS area neurons was carried out after the behavioral training, from 3 to 7 months after the visual cortex lesions. The properties of these neurons were compared to those of LS area neurons in normal cats (Spear and Baumann, 1975) and in cats with acute or short-term visual cortex damage and no behavioral recovery (Spear and Baumann, 1979). The results showed that all of the changes from normal which were produced by acute visual cortex damage were also present after the behavioral recovery. Moreover, all of the response properties of LS area neurons which remain after acute visual cortex damage were present in similar form after the behavioral recovery. There was no evidence for any functional reorganization in the LS area concomitant with its role in the behavioral recovery. These results suggest that functional reorganization plays little or no role in recovery from visual cortex damage in adult cats. Rather, the recovery of form and pattern discrimination ability appears to be based upon the functioning of residual neural processes in the LS area which remain after the visual cortex damage.

Functional organization of lateral geniculate cells following removal of visual cortex in the newborn kitten.

Abstract: When the visual cortex of a newborn kitten is removed, most neurons in the dorsal lateral geniculate nucleus degenerate, but a small population of large cells is spared. Electrophysiological recording revealed that detailed visual topography in the nucleus is abnormal and that single cells have unusually large receptive fields. These results suggest that optic axons deprived of their normal synaptic targets rearrange their connections to converge on local surviving neurons.

Stereopsis and the random element in the organization of the striate cortex

Abstract: Receptive field position and orientation disparities are both properties of binocularly discharged striate neurons. Receptive field position disparities have been used as a key element in the neural theory for binocular depth discrimination. Since most striate cells in the cat are binocular, these position disparities require that cells immediately adjacent to one another in the cortex should show a random scatter in their monocular receptive field positions. Superimposed on the progressive topographical representation of the visual field on the striate cortex there is experimental evidence for a localized monocular receptive field position scatter. The suggestion is examined that the binocular position disparities are built up out of the two monocular position scatters. An examination of receptive field orientation disparities and their relation to the random variation in the monocular preferred orientations of immediately adjacent striate neurons also leads to the conclusion that binocular orientation disparities are a consequence of the two monocular scatters. As for receptive field position, the local scatter in preferred orientation is superimposed on a progressive representation of orientation over larger areas of the cortex. The representation in the striate cortex of visual field position and of stimulus orientation is examined in relation to the correlation between the disparities in receptive field position and preferred orientation. The role of orientation disparities in binocular vision is reviewed.

Spatial periodicities of periodic complex cells in the visual cortex cluster at one-half octave intervals.

Abstract: Within individual penetrations in the visual cortex, spatial periodicities of periodic complex cells differ by either one-half or one octave When data are pooled from neurons subserving the central visual area in many cats, the results indicate that spatial periodicities cluster at one-half octave intervals over a 2 1/2-octave range (095 to 54 cyc/deg) Thus a relatively small number of such channels spaced at regular intervals along a logarithmic scale within each orientation column may suffice for this stage of spatial processing

The role of binocular neurons in the cat striate cortex in combining information from the two eyes.

Abstract: Cats were raised under conditions of daily alternating monocular exposure, so that each eye received normal input, but the animals were never allowed to use both eyes simultaneously. With single cell recording techniques it could be shown that this led to a severe disturbance of the normal binocularity of cortical neurons.

Heterogeneity of neuron populations with complex receptive fields in the cat visual cortex

Abstract: The selectivity of striate neurons with complex receptive fields to the orientation, direction, and velocity of movement of various stimuli was investigated in unanesthetized and uncurarized cats. On the basis of all characteristics obtained by the study of single-unit responses to a stationary flickering slit, a moving spot of light, and a moving oriented stimulus, four groups of complex neurons were distinguished. The characteristics of group I neurons indicate a mechanism of orientation selectivity in the organization of their receptive fields, group IV neurons have a mechanism of directional selectivity, and neurons of groups II and III possess both mechanisms. The existence of separate neuronal systems coding the orientation and direction of stimulus movement is suggested.