Representation of Natural Movies across the Visual Cortex

Below is a video showing the spatio-temporal activity patterns in response to artificial and natural stimuli. These beautiful recordings were realized by Dirk Jancke in his laboratory. We compared the activity patterns evoked by natural movies to those evoked by artificial stimuli (such as for example moving edges) that are typically used in physiological experiments.

We are the first research group recording cortical large-scale activity patterns in response to natural movies using the method of voltage-sensitive dye imaging.

Voltage-sensitive dye imaging during natural and artificial conditions. The first column depicts stimuli as shown during the experiment: drifting square gratings (rows 1 and 2) and natural movies recorded by cats (rows 3 and 4). Colored rectangles indicate the position of receptive fields hand-mapped at each penetration site, symbolized with a color-matching circle in the second column. Evoked optical imaging signals caused by these stimuli are depicted in the second column. The scale bar represents 1 mm across cortex. Note that the color code has different scales across different conditions. The third column depicts the time course of spatially averaged activity. The strength of motion flow field is represented in the last column.

Voltage-sensitive dye recordings of cortical responses to natural stimuli and gratings. (A) Two natural movies (blue and orange boxes) and gratings (gray box) used as stimulation are depicted together with evoked cortical responses. Visual stimuli are shown in upper rows within each box (movie 1 and movie 2). Leftmost image represents an example movie frame covering approximately a visual angle of 30° 3 40°. The scale bar represents 5° of visual angle. White rectangle approximates the local portion that directly stimulated the recorded cortical area. The temporal evolution of the movie within the delineated region is shown in succeeding frames. The second row within each box displays activity during intervals of nonoverlapping 100-ms frames including the prestimulus period. The rightmost image shows the average activity computed over the entire stimulus presentation of 2 s. See top left frame for vascular image of the recorded cortical area (P 5 posterior, L 5 lateral; scale bar represents 1 mm). Color bar indicates activity levels as fractional fluorescence change relative to blank. (B) Time courses of global activity computed as the average across all pixels of a given frame. Shaded gray area symbolizes prestimulus period. Line colors are matched to the boxes shown in A; black 5 grating, blue/red 5 natural conditions. The thickness of lines represents CIs computed by resampling all the pixels that belong to a given frame (P 5 10^5). Right panel: Mean amplitudes of activity; error bars represent the SD.

Few more videos:

Representation of Simple Stimuli across the Visual Cortex

Moving edges, which consist of drifting dark and bright bars, are kind of stimuli that are commonly used in physiological experiments mainly because of their parametrically controllable aspects.

The video below shows the large-scale cortical dynamics at the spatial scale of several millimeters during presentation of such visual stimuli.

Overlaid on the well-known orientation maps (shown at the bottom row), which are evoked by the specific orientation of the stimuli, drifting edges are furthermore represented by propagating waves (top row). The original publication can be found here.

NeuroImage from sonat on Vimeo.

Caption: Multiplexing of space and orientation information. The data presented in Fig. 1 and 2 is presented as a video. Upper video: Propagating activity reconstructed by combining oscillatory SVD components, averaged across several propagation cycles during stimulus presentation (cf. Fig. 3 and Fig. 4a). M = Medial, P = Posterior. Lower video: Propagating waves are shown in combination with tonic SVD components representing the orientation maps. The weight of both components were equalized prior to their combination. Contour lines are drawn at 90th activity percentiles of the tonic components.

Decomposition of evoked cortical responses to gratings of 0.2 c/deg drifting for 2 s at a temporal frequency of 6.25 Hz. (a) Evoked spatio-temporal activity patterns (top rows) and time courses obtained by spatial averages across the images (bottom traces) expressed as fractional change in fluorescence relative to blank condition (ΔF/F). Top left frame shows the vascular image of the recorded right hemisphere, P = posterior, L = lateral; here and in all figures scale bar 1 mm. Leftmost frame in 2nd row depicts the time-averaged orientation map derived by subtracting evoked responses to the vertical grating from horizontal. Green trace = responses to vertical grating, drifting rightwards in visual space; blue trace = horizontal grating, drifting downwards. (b) Top left corner, singular values, gi, ranked in order of their contributions. Components of significant contribution to variance are colored (gray area depicts significance level). The contribution of each single SVD component to single recorded trials (n=35) was computed, their correlations across trials are represented as a matrix. Spatial (ui(x)) and temporal (vi(t)) modes of the SVD components were clustered according to their correlation (red, yellow, and green boxes; curves represent weight of each spatial mode [y-axes] as a function of time [400–1800 ms]).

Stereoscopic Cat-Cam Movies