[Structure of Response and Dynamics of Preferred Orientation in Cat's V1 Neurons].

Preferred orientation of V1 neurons was changed during the respons time course. In order to reveal mechanisms of such changes, spike trains of single neurons to flashed bars of different orientations were studied by means of principal component and frequency-domain analysis of the spike density functions. There was found out that: 1. contribution of each of the components was dependent on the stimulus orientation. 2. the principal components of V1 neurons responses contain different kinds of transient and sustained parts and rhythmic oscillations in the theta/alpha and beta-bands. 3. There was no correlation between transient parts as well as between rhythmic oscillations within the same frequency band in different components. Taken together, the data obtained allow us to suggest that during generation of response there is a shift of dominance of the components with different orientations which determines the dynamics of the preferred orientations of V1 neurons.

[Comparison of its and orientation tuning dynamics in neurons located in different functional domains of cat's primary visual cortex].

Orientation tuning and its dynamics of cat's primary visual cortex neurons located in pinwheel centers and orientation columns were studied during development of response in time. Functional domains in the Cortex were revealed by intrinsic signal optical imaging on functional and vascular maps of cortex. Both maps were used for precise placement of electrodes during recordings. Orientation tuning dynamic of each neuron was analyzed by temporary slices technique. Several types of neurons were observed in different functional domains: neurons with stable preferred orientation (14.5%); cells with preferred orientation dynamically shifted by 102 +/- 5 degrees (40.8%) and neurons with mixed dynamics type (44.7%). In pinwheel centers neurons with stable preferred orientation are differed from neurons with unstable preferred orientation in their features. In particular, they are showing greater response strength for preferred orientation. In orientation columns neurons with stable tuning are demonstrating larger latent periods for all orientations including preferred and non-preferred in comparison to cells with unstable response dynamics. We observed better detection quality of stable orientation neurons than in unstable preferred orientation neurons. Further coding features of neurons belonging to one functional type but located in different domains were compared. In general, located in pinwheel centers stable neurons have shorter latencies and stronger responses than for the stable cells located in orientation columns. Detection features were similar for this functional type of neurons. Unstable neurons located in different functional domains don't differ from each other in orientation tuning characteristics. Functional significance of neurons with stable and unstable preferred orientation located in pinwheel center and orientation columns in visual information processing are discussed.

[Alpha- and beta-oscillations of dynamics of the area and weight of receptive fields of cat striate neurons under conditions of classical and combined mapping].

In 22 acute experiments in anesthetized and immobilized adult cats the dynamics of 83 receptive fields (RF) of 47 striate neurons was studied by temporal slices method. Classical mapping revealed wave-like changes in the area and weight of neuronal RFs. Special mathematical analysis showed that such changes represented a sum of a slow non-oscillatory and comparatively fast components. The slow component was a biphasic up and down RF dynamics. In most cases, the oscillation frequencies were within the alpha- and beta- EEG frequency ranges. When the RF center was activated additionally during combined mapping, the oscillations frequencies remained unchanged, but the duration and amplitude of non-oscillatory component substantially decreased. Mechanisms underlying the RF dynamics and its functional significance are discussed.

[Receptive fields of cat striate neurons: dynamics of weight and topographical characteristics of the excitatory zone of the neuron receptive fields in the visual cortex].

In 22 acute experiments on anesthetized and immobilized adult cats, the dynamics of 83 on- and/or off-receptive fields (RF) was studied in 47 striate neurons with the method of temporal slices by mapping with single-flash stimuli. The latency of the RF appearance was 88 +/- 5 ms, and its duration was 192 +/- 12 ms. Dynamical wavy changes in the RF sizes and weights repeating up to three times were revealed. The mean duration of one wave was 95 +/- 4 ms. In 99% of cases, the RF discharge center defined for one temporal slice also displaced in an undulatory way relatively the RF's center defined for whole analysis period. The mean duration of this undulatory cycle was 67.3 +/- 3 ms. In 72.5% of cases, the displacement of the discharge center followed different trajectories inscribed in an ellipse. The functional significance of such changes in the RFs of striate neurons is discussed with regard to the dynamics of their detector features and underlying mechanisms.