Physiological effects of unequal alternating monocular exposure

1983 ◽  
Vol 49 (3) ◽  
pp. 804-818 ◽  
Author(s):  
D. G. Tieman ◽  
M. A. McCall ◽  
H. V. Hirsch

1. In order to investigate the effects of an imbalance in stimulation to the eyes without the confounding influence of continuous deprivation of one eye, we reared cats with unequal alternating monocular exposure (AME) and, for comparison, cats with equal AME. We recorded extracellularly from single cells in area 17 of visual cortex. 2. For unequal AME cats, a majority of the cells that were visually responsive were dominated by the eye that had received more patterned visual experience. The percentage of cells dominated by the more experienced eye was greater with a large imbalance in stimulation to the two eyes (AME 8/1, 77%) than with a small imbalance (AME 8/4, 62%). 3. For both equal AME cats and unequal AME cats, we obtained evidence for differences in cells activated by the contralateral and by the ipsilateral afferents. a) In equal AME cats receiving only 1 h of exposure per day, we obtained a greater dominance by the contralateral eye (60%) than in equal AME cats receiving 8 h of exposure per day (42%). b) Although a large imbalance in stimulation (AME 8/1) resulted in a shift in ocular dominance in both cortical hemispheres, a moderate imbalance (AME 8/4) resulted in a smaller shift, which was apparent only in the hemisphere ipsilateral to the less-experienced eye. 4. The percentage of cortical cells responsive to each eye was uniform throughout the depth of cortex. Thus, for the unequal AME cats, cells activated by the less-experienced eye were no more frequent in layer IV of visual cortex than in the infragranular and supragranular layers. 5. Although almost all cells recorded from AME cats had relatively normal receptive-field properties, three receptive-field properties of cells in unequal AME cats showed an effect of the rearing. In each case cells dominated by the less-experienced eye and recorded in the cortical hemisphere ipsilateral to it showed the largest changes. These cells a) were more poorly tuned, b) had lower cutoff velocities, and c) had smaller receptive fields. 6. It is suggested that cortical cells that putatively receive Y-cell afferents from the dorsal lateral geniculate nucleus (LGNd) are more affected by an imbalance in stimulation than are cortical cells that putatively receive X-cell afferents. Thus, the decrease in mean receptive-field area and cutoff velocity for the cells dominated by the less-experienced eye is suggested to be due to a greater shift in ocular dominance by the cortical cells receiving Y-cell afferents from the LGNd. 7. The interaction between binocular competition and deprivation of pattern vision may contribute to differences between monocularly deprived cats and unequal AME cats.

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


2005 ◽  
Vol 15 (01n02) ◽  
pp. 31-40
Author(s):  
BASABI BHAUMIK ◽  
ALOK AGARWAL ◽  
MANISH MANOHAR

The primary visual cortex is organized into clusters of cells having similar receptive fields (RFs). A purely feedforward model has been shown to produce realistic simple cell receptive fields. The modeled cells capture a wide range of receptive field properties of orientation selective cortical cells. We have analyzed the responses of 78 nearby cell pairs to study which RF properties are clustered. Orientation preference shows strongest clustering. Orientation tuning width (hwhh) and tuning height (spikes/sec) at the preferred orientation are not as tightly clustered. Spatial frequency is also not as tightly clustered and RF phase has the least clustering. Clustering property of orientation preference, orientation tuning height and width depend on the location of cells in the orientation map. No such location dependence is observed for spatial frequency and RF phase. Our results agree well with experimental data.


1999 ◽  
Vol 81 (2) ◽  
pp. 825-834 ◽  
Author(s):  
Iran Salimi ◽  
Thomas Brochier ◽  
Allan M. Smith

Neuronal activity in somatosensory cortex of monkeys using a precision grip. I. Receptive fields and discharge patterns. Three adolescent Macaca fascicularis monkeys weighing between 3.5 and 4 kg were trained to use a precision grip to grasp a metal tab mounted on a low friction vertical track and to lift and hold it in a 12- to 25-mm position window for 1 s. The surface texture of the metal tab in contact with the fingers and the weight of the object could be varied. The activity of 386 single cells with cutaneous receptive fields contacting the metal tab were recorded in Brodmann’s areas 3b, 1, 2, 5, and 7 of the somatosensory cortex. In this first of a series of papers, we describe three types of discharge pattern, the receptive-field properties, and the anatomic distribution of the neurons. The majority of the receptive fields were cutaneous and covered less than one digit, and a χ2 test did not reveal any significant differences in the Brodmann’s areas representing the thumb and index finger. Two broad categories of discharge pattern cells were identified. The first category, dynamic cells, showed a brief increase in activity beginning near grip onset, which quickly subsided despite continued pressure applied to the receptive field. Some of the dynamic neurons responded to both skin indentation and release. The second category, static cells, had higher activity during the stationary holding phase of the task. These static neurons demonstrated varying degrees of sensitivity to rates of pressure change on the skin. The percentage of dynamic versus static cells was about equal for areas 3b, 2, 5, and 7. Only area 1 had a higher proportion of dynamic cells (76%). A third category was identified that contained cells with significant pregrip activity and included cortical cells with both dynamic or static discharge patterns. Cells in this category showed activity increases before movement in the absence of receptive-field stimulation, suggesting that, in addition to peripheral cutaneous input, these cells also receive strong excitation from movement-related regions of the brain.


1978 ◽  
Vol 41 (4) ◽  
pp. 948-962 ◽  
Author(s):  
A. G. Leventhal ◽  
H. V. Hirsch

1. Receptive-field properties of neurons in the different layers of the visual cortex of normal adult cats were analyzed quantitatively. Neurons were classified into one of two groups: 1) S-cells, which have discrete on- and/or off-regions in their receptive fields and possess inhibitory side bands; 2) C-cells, which do not have discrete on- and off-regions in their receptive fields but display an on-off response to flashing stimuli. Neurons of this type rarely display side-band inhibition. 2. As a group, S-cells display lower relative degrees of binocularity and are more selective for stimulus orientation than C-cells. In addition, within a given lamina the S-cells have smaller receptive fields, lower cutoff velocities, lower peak responses to visual stimulation, and lower spontaneous activity than do the C-cells. 3. S-cells in all layers of the cortex display similar orientation sensitivities, mean spontaneous discharge rates, peak response to visual stimulation, and degrees of binocularity. 4. Many of the receptive-field properties of cortical cells vary with laminar location. Receptive-field sizes and cutoff velocities of S-cells and of C-cells are greater in layers V and VI than in layers II-IV. For S-cells, preferred velocities are also greater in layers V and VI than in layers II-IV. Furthermore, C-cells in layers V and VI display high mean spontaneous discharge rates, weak orientation preferences, high relative degrees of binocularity, and higher peak responses to visual stimulation when compared to C-cells in layers II and III. 5. The receptive-field properties of cells in layers V-VI of the striate cortex suggest that most neurons that have their somata in these laminae receive afferents from LGNd Y-cells. Hence, our results suggest that afferents from LGNd Y-cells may play a major part in the cortical control of subcortical visual functions.


2012 ◽  
Vol 24 (10) ◽  
pp. 2700-2725 ◽  
Author(s):  
Takuma Tanaka ◽  
Toshio Aoyagi ◽  
Takeshi Kaneko

We propose a new principle for replicating receptive field properties of neurons in the primary visual cortex. We derive a learning rule for a feedforward network, which maintains a low firing rate for the output neurons (resulting in temporal sparseness) and allows only a small subset of the neurons in the network to fire at any given time (resulting in population sparseness). Our learning rule also sets the firing rates of the output neurons at each time step to near-maximum or near-minimum levels, resulting in neuronal reliability. The learning rule is simple enough to be written in spatially and temporally local forms. After the learning stage is performed using input image patches of natural scenes, output neurons in the model network are found to exhibit simple-cell-like receptive field properties. When the output of these simple-cell-like neurons are input to another model layer using the same learning rule, the second-layer output neurons after learning become less sensitive to the phase of gratings than the simple-cell-like input neurons. In particular, some of the second-layer output neurons become completely phase invariant, owing to the convergence of the connections from first-layer neurons with similar orientation selectivity to second-layer neurons in the model network. We examine the parameter dependencies of the receptive field properties of the model neurons after learning and discuss their biological implications. We also show that the localized learning rule is consistent with experimental results concerning neuronal plasticity and can replicate the receptive fields of simple and complex cells.


1985 ◽  
Vol 54 (1) ◽  
pp. 168-183 ◽  
Author(s):  
H. A. Swadlow ◽  
T. G. Weyand

The intrinsic stability of the rabbit eye was exploited to enable receptive-field analysis of LGNd neurons and optic tract axons in the awake, unparalyzed state. We found eye position to remain within a range of less than 1.0 degrees for periods of 4-5 min, and in some cases for periods in excess of 10 min. Such stability is comparable to that seen in awake monkeys that have been trained to fixate. Receptive fields of dorsal lateral geniculate nucleus (LGNd) neurons were analyzed, and approximately 84% were concentrically organized. This is a higher value than previously reported in this species. In addition, the receptive-field centers of concentric cells were much smaller than those previously reported (mean diameter = 2.5 degrees). Most remaining neurons in the LGNd were either directionally selective (6.5%) or motion/uniform (6.5%). Concentric cells were classified as sustained or transient based on response duration to standing contrast. In the LGNd the receptive fields of sustained concentric cells were predominantly near the horizontal meridian, within the representation of the visual streak, while the receptive-field positions of transient concentric cells were more prevalent in the upper visual field. In the optic tract the receptive-field positions of both sustained and transient cells were more evenly distributed than was seen in the LGNd. Sustained and transient concentric cells in LGNd showed primarily nonlinear spatial summation. The receptive-field properties of LGNd neurons were related to geniculocortical antidromic latency. Most LGNd neurons of all receptive-field classes projected axons to the visual cortex. Thus, any intrinsic interneurons in the rabbit LGNd may have receptive-field properties similar to those of some principal neurons. There was significant overlap in the distribution of antidromic latencies in neurons of different receptive-field classes. Concentric sustained neurons, however, did conduct somewhat more slowly than did concentric transient neurons. Nonvisual sensory stimuli that resulted in EEG arousal (hippocampal theta activity) had a profound effect on the response duration of most (28/32) sustained concentric neurons. For these cells, the sustained response to standing contrast began to diminish and sometimes disappeared after 2-15 s. However, arousing stimuli that resulted in hippocampal theta activity reestablished the sustained response. Such arousing stimuli usually had little or no effect on the discharge of the cell in the absence of visual stimuli. Arousing stimuli had no effect on optic tract axons with sustained concentric receptive-field properties.(ABSTRACT TRUNCATED AT 400 WORDS)


1975 ◽  
Vol 38 (4) ◽  
pp. 735-750 ◽  
Author(s):  
B. Dreher ◽  
L. J. Cottee

1. Receptive-field properties of single neurons in cat's cortical area 18 were studied before and after partial bilateral lesions of area 17. 2. The majority of cells recorded from animals with intact visual cortex exhibited orientation selectivity, directional selectivity, and could be independently activated through either eye. All cells responded well to moving targets and nearly all of them exhibited broadly tuned preferences with respect to speed of the target. Over 45% of cells responded optimally or exclusively at very fast (above 50 degrees/s) speeds. 3. The majority of neurons recorded from animals with intact visual cortex responded weakly but clearly to appropriately oriented localized stationary stimuli flashed on and off. About one-third of the cells responded with mixed on-off discharges from all over their receptive field. In the receptive fields of 10% of cells, separate on- and off-discharge regions could be revealed. In the receptive fields of the remaining cells, only on- or only off-discharge regions could be revealed. 4. The majority of neurons recorded after ablation of area 17 were orientation selective; 50% of the cells were also direction selective. All neurons responded well to moving targets; about 65% of them responded optimally or exclusively at very fast target speeds. 5. Destruction of the dorsolateral part of contralaterial area 17 and most of contralateral area 18 caused significant reduction in proportion of cells in area 18 which could be activated through either eye. 6. The majority of neurons recorded after ablation responded to appropriately oriented localized stationary stimuli flashed on and off. Cells with mixed on-off discharge regions all over the receptive field with separate on- and off-discharge regions and with only on- or only off-discharge regions were found. 7. It is concluded that the processing of afferent visual information in area 18 is, to a great extent, independent of the information carried to this area by associational fibers from cells of area 17.


1979 ◽  
Vol 204 (1157) ◽  
pp. 455-465 ◽  

In most respects, the response properties of cells in the secondary visual cortex of the newborn lamb were indistinguishable from those in the adult. The cells were sharply selective to orientation; the orientation preferences were the same in each eye, and they varied systematically as the electrode penetrated the cortex. The receptive-field organization did not differ noticeably from that in adults, and complex, hypercomplex, and a few simple cells were all observed. The ocular dominance distribution was similar to that in the adult. Most importantly, binocular cells were found with disparate receptive fields even in newborn, visually inexperienced animals. As in the adult, the disparities were largely horizontal, and they appeared to be arranged in columns. Many of the cells responded preferentially to a binocular stimulus at a particular disparity setting (often approximately zero), but unlike those in the adult almost all the binocular cells in the newborn lamb would also respond monocularly, and the enhancement at the optimal disparity was less than in the adult. The full development of binocular selectivity took several weeks, and was blocked by binocular deprivation. We conclude that the basic wiring of stereoscopic mechanisms is innate, but the development of mature binocular interaction may depend on an adaptive process which makes use of the visual information received during binocular stimulation.


1983 ◽  
Vol 50 (1) ◽  
pp. 102-124 ◽  
Author(s):  
B. E. Stein ◽  
N. S. Gaither

The receptive-field properties of single cells in the optic tectum of Iguana iguana were studied using the same procedures as have been used in this laboratory in studying its mammalian homologue, the superior colliculus. Surprisingly, despite some species-specific characteristics, the range of physiological properties of tectal and superior collicular cells appeared to be strikingly similar. This observation is not consistent with the notion that functional differences between these structures evolved as a consequence of the tremendous elaboration of mammalian neocortex and its involvement in sensory processes. The internal organization of visual tectal receptive fields was observed to be very much like that described in mammals. This included a similar distribution of on-off areas, the presence of both spatial summation and spatial inhibition within the excitatory receptive-field borders, suppressive areas just beyond these borders, and a marked tendency for habituation. In addition, many cells showed distinct directional preferences that were strongly influenced by the velocity of movement through the receptive field. Furthermore, the receptive fields of bimodal and trimodal cells showed topographic correspondences as in mammals, although the sizes of the fields were often large, thereby emphasizing the lack of an exact register between modalities. In contrast to the findings in mammals, however, a preference for stationary over moving stimuli was observed in most neurons, and specializations in iguana tectal cells representing the fovea were noted that have not been described in other species. These foveal specializations include a distinct preference for stationary over moving stimuli, the absence of directional selectivity, and the presence of a majority of cells responding at light onset only. It is suggested that the similarities in the organization and response properties of cells of the optic tectum and superior colliculus reflect the retention of ancestral characteristics through various levels of vertebrate evolution. Furthermore, the subtle species differences in the properties of these cells appear to reflect adaptations to specific ecological pressures rather than general evolutionary trends.


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