Rat's Somatosensory Cortex
Joseph King, Min Xie, Bibo Zheng and Karl Pribram
Center for Brain Research and Informational Sciences and Department of Psychology Radford University, Radford, VA 24142
To extend findings from visual neurophysiology we plotted responses for 48 locations in the somatosensory "barrel cortex" of the rat to spatial and temporal frequency stimulation of their vibrissae. The recordings obtained from bursts of spikes were plotted as response manifolds resembling field potentials such as those recorded with small macroelectrodes. The burst manifolds were shown to be composed of those obtained from single spikes, demonstrating continuity between two levels of analysis (single spikes and bursts).
A computer simulation of our results showed that, according to the principles of signal processing, the somatosensory receptive fields can be readily described by Gabor-like functions much as in the visual system. Further, changes with respect to direction of whisker stimulation could be described in terms of spatiotemporal (vectorial?) shifts among these functions.
As late as the 1950's, the structure of memory storage and the brain processes leading to perception remained enigmatic. Thus Karl Lashley ( 1950) could exclaim that his lifelong search for an encoded memory trace had been in vain, and Gary Boring ( 1929) could indicate in his History of Experimental Psychology that little was to be gained, at this stage of knowledge, by psychologists studying brain function.
All this was dramatically changed when engineers, in the early 1960's, found ways to produce optical holograms using the mathematical formulation proposed by Dennis Gabor ( 1948). The mathematics of holography and physical properties of holograms provided a palpable instantiation of distributed memory and how percepts (images) could be retrieved from such a distributed store. Engineers, (e.g. Van Heerden, 1963) psychophysicists, (e.g. Julez and Pennington, 1965); and neuroscientists, (e.g. Pribram, 1966; and Pollen, Lee and Taylor, 1971) saw the relevance of holography to the hitherto intractable issues of brain function in memory and perception ( Barrett, 1969; Campbell & Robson, 1968; and Pribram, Nuwer and Barron, 1974).