Space-time inseparable receptive field of a simple cell

RF movie
MPEG animation file (14 kbytes, bk318r03.03e.mpg)
Copyright 1995, Izumi Ohzawa.


This animation shows the space-time receptive field of a direction selective simple cell in the cat striate cortex (area 17). The domain covers a 4 x 4 degree area in space, and the time dimension is shown by animated frames at 10 millisecond intervals (0 .. 300 msec, MPEG movies show the animation with 5 msec intervals). The number that appears at the bottom left corner of the animation is the time (correlation delay) in milliseconds at which the spatial (X-Y) map is displayed. In real space, the mapping grid and the RF were oriented at an oblique angle (130 degs), but the RF is shown here in the upright position for convenience of display.
Note that the subregions appear to move to the right. The velocity at which the subregions move has been shown to correlate well with the preferred velocity (speed and direction) of simple cells to moving bar-shaped stimuli (McLean and Palmer, 1989, 1994). Because of this gradual movement of RF subregions, it is not possible to factor the space-time RF profile into a product of two separate functions, one of space and the other of time. Therefore, these RFs are space-time inseparable.


This is an X-T (space-time) RF map derived from the 3-D X-Y-T domain data presented in the animation above. The cube has been collapsed (integrated) along the Y-axis. Areas shown in green and red represent subregions excitatory to bright and dark stimuli, respectively. Horizontal axis is space (4 degs), vertical axis is time (0-300 msec). Time zero is at the bottom. The space-time orientation of these RFs is closely related to direction selectivity. The slope of the bright and dark subregions shows a good agreement with the optimal velocity measured with other types of stimuli (e.g., moving bars and sinusoidal gratings). See McLean, J., Raab, S., and Palmer, L.A. Visual Neurosci. 11: 271-294, 1994. 

XY domain size: 4 x 4 degs
XY grid: 20 x 20 points
Time domain: 0 - 300 msec in 5 msec steps
Orientation: 130 degs
Bar Size: 1.5 x 0.5 degs
Eye: right
Number of repetitions: 40
Total time for RF measurement: 31 min
Duration of individual stimuli: 52.6 msec (4 frames)
Slide

Compressed PostScript slide file (112 kbytes, XYT2XT.ps.Z)
Acrobat slide file (55 kbytes, XYT2XT.pdf) Copyright 1993, DeAngelis, Ohzawa, and Freeman.

Binocular version of this slide

Guided tour to complex cell RF
Space-time separable simple cell