Spatial and temporal selectivity in the suprasylvian visual cortex of the cat (original) (raw)
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Temporal-frequency tuning of direction selectivity in cat visual cortex
Vis Neurosci, 1992
Responses of 71 cells in areas 17 and l8 of the cat visual cortex were recorded extracellularly while stimulating with gratings drifting in each direction across the receptive field at a series of temporal frequencies. Direction selectivity was most prominent at temporal frequencies of l-2H2. In about 2090 of the total population, the response in the nonpreferred direction increased at temporal frequencies of around 4Hzand direction selectivity was diminished or lost. In a few cells the preferred direction reversed.
Acta neurobiologiae experimentalis, 1986
The fine structure of the receptive fields of the lateral suprasylvian area neurons was investigated in the pretrigeminal cat preparation. A majority of the receptive fields consisted of subregions with different qualitative characteristics according to their response to moving visual stimuli. There was an asymmetry in the spatial distribution of inhibitory mechanisms over the receptive field. The steady illumination of the receptive field usually enhanced the inhibitory processes, whereas darkness, decreased the effectivity of inhibitory influences on the neuron. Some receptive fields of neurons reacted vigorously to the motion of borders of visual stimuli. It is suggested that the differences in response patterns to moving stimuli depend in part on the heterogenous fine structure of their receptive fields.
Mechanisms of Direction Selectivity in Cat Primary Visual Cortex as Revealed by Visual Adaptation
Journal of Neurophysiology, 2010
In contrast to neurons of the lateral geniculate nucleus (LGN), neurons in the primary visual cortex (V1) are selective for the direction of visual motion. Cortical direction selectivity could emerge from the spatiotemporal configuration of inputs from thalamic cells, from intracortical inhibitory interactions, or from a combination of thalamic and intracortical interactions. To distinguish between these possibilities, we studied the effect of adaptation (prolonged visual stimulation) on the direction selectivity of intracellularly recorded cortical neurons. It is known that adaptation selectively reduces the responses of cortical neurons, while largely sparing the afferent LGN input. Adaptation can therefore be used as a tool to dissect the relative contribution of afferent and intracortical interactions to the generation of direction selectivity. In both simple and complex cells, adaptation caused a hyperpolarization of the resting membrane potential (−2.5 mV, simple cells, −0.95 ...
Neuroscience, 1998
It is generally considered that the posteromedial part of the cat's lateral suprasylvian cortex is involved in the analysis of image motion. The main afferents of the posteromedial lateral suprasylvian cortex come from a direct retinogeniculate pathway and indirect retinotectal and retino-geniculo-cortical pathways. Removal of the primary visual cortex does not affect the spatial and temporal processing of suprasylvian cortex cells suggesting that these properties are derived from thalamic input. We have investigated the possibility that the striate-recipient zone of the lateral posterior nucleus-pulvinar complex may be responsible for the spatial (and temporal) frequency processing in posteromedial lateral suprasylvian cortex since these two regions establish strong bidirectional connections and share many visual properties. Experiments were done on anaesthetized normal adult cats. Visual responses in suprasylvian cortex were recorded before, during, and after the deactivation of the lateral part of the lateral posterior nucleus accomplished by the injection of lidocaine or GABA. Results can be summarized as follows. A total of 64 cells was tested. Out of this number, 11 units were affected by the deactivation of the lateral part of lateral posterior nucleus and one cell, by the blockade of pulvinar. For all cells, except one, the effect consisted in a global reduction of the evoked discharge rate suggesting that the thalamo-suprasylvian cortex projections are excitatory in nature. We did not find any significant differences in the optimal spatial frequency, nor in the width of the tuning function, whether the grating was presented at half-or saturation contrast. In addition, there were no significant differences between the low-and high cut-off spatial frequency values computed before and after the deactivation of the lateral posterior nucleus. No specific changes were observed in the contrast sensitivity function of the posteromedial lateral suprasylvian cortex cells. Similar results were observed with respect to the temporal frequency tuning functions. Deactivating the lateral posterior nucleus did not modify the direction selectivity nor the organization of the subregions of the lateral suprasylvian cortex ''classical'' receptive fields.
Linear mechanisms of directional selectivity in simple cells of cat striate cortex
Proceedings of the National Academy of Sciences, 1987
The role of linear spatial summation in the directional selectivity of simple cells in cat striate cortex was investigated. The experimental paradigm consisted of comparing the response to drifting grating stimuli with linear predictions based on the response to stationary contrast-reversing gratings. The spatial phase dependence of the response to contrast-reversing gratings was consistent with a high degree of linearity of spatial summation within the receptive fields. Furthermore, the preferred direction predicted from the response to stationary gratings generally agreed with the measurements made with drifting gratings. The amount of directional selectivity predicted was, on average, about half the measured value, indicating that nonlinear mechanisms act in concert with linear mechanisms in determining the overall directional selectivity.
Layers 2/3 in the Cat Visual Cortex
2015
feedback projections from area 18 layers 2/3 to area 17 layers 2/3 in the cat visual cortex. J. Neurophysiol. 82: 2667–2675, 1999. In the absence of a direct geniculate input, area 17 cells in the cat are nevertheless able to respond to visual stimuli because of feedback connections from area 18. Anatomic studies have shown that, in the cat visual cortex, layer 5 of area 18 projects to layer 5 of area 17, and layers 2/3 of area 18 project to layers 2/3 of area 17. What is the specific role of these connections? Previous studies have examined the effect of area 18 layer 5 blockade on cells in area 17 layer 5. Here we examine whether the feedback connections from layers 2/3 of area 18 influence the orientation tuning and velocity tuning of cells in layers 2/3 of area 17. Experiments were carried out in anesthetized and paralyzed cats. We blocked reversibly a small region (300 mm radius) in layers 2/3 of area 18 by iontophoretic application of GABA and recorded simultaneously from cell...
Modification of direction selectivity of neurons in the visual cortex of kittens
Brain Research, 1975
Accumulating evidence suggests that the development of the cat visual system is dependent on visual experience. Visual deprivation results in the loss of functional specificity in cortical neurons6,10, 22 and it is possible to cause specific and long lasting changes in the functional properties of cortical neurons 2,3,7,8,11-13,~7,21 by brief selective exposure during the critical period. In particular, it has been shown that cortical neurons become orientation-selective in the same axis as the visual stimuli presented during exposure3,8,13. If exposed to stimuli which lack orientation cues, cortical cells lose or fail to develop orientation specificity H. Cortical units in mature cats are sensitive not only to specific shapes but also selective for the speed and the direction of moving contrasts. It has recently been shown as well, that stimulus movement is a crucial parameter in the development of such normal cortical selectivity 4. With these considerations in mind, we therefore attempted to determine the extent to which dynamic RF properties such as direction selectivity and velocity tuning can be modified by selective visual exposure.