Abstract
The signal processing function of human cerebral cortical tissues is determined by the regional cytoarchitectures distributed throughout the brain. Based upon this assumption, we pursued the hypothesis that residual microstructure within the primary and associative visual cortices of a fixed, post-mortem whole human brain would process electrical signals differentially. To this end, we designed and engineered a very simple brain-photocell interface. Photostimuli, presented as either periodic flashes or as dynamic visual images, were transduced by photocells attached to the optic nerve of a post-mortem human brain specimen. The novel approach revealed that microvolt fluctuations within the primary and associative visual cortices could be discriminated. Simple light-dark discrimination was noted for the primary visual area (BA17) whereas within the right occipito-parietal cortices of the dorsal visual stream (BA19, BA7), spectral power of microvolt fluctuations could discriminate moving visual stimuli from those which were non-moving. Discriminant analysis classified movement represented within the right parietal lobe with 80% success. Together, the results suggest that artificially generated electrical signals are processed differentially by alternative cortical regions in the post-mortem brain.
Highlights
One of the principle assumptions of modern neuroscience is that structure dictates function
Simple light-dark discrimination was noted for the primary visual area (BA17) whereas within the right occipito-parietal cortices of the dorsal visual stream (BA19, BA7), spectral power of microvolt fluctuations could discriminate moving visual stimuli from those which were non-moving
A less robust difference within the alpha-beta2 Spectral power density (SPD) range between the “no phototransduction” condition and left optic nerve phototransduction condition was noted (r2 = 0.06), though both of these conditions did not differ from baseline alpha-beta2 SPDs (p > 0.05)
Summary
One of the principle assumptions of modern neuroscience is that structure dictates function. A corollary of this principle is that whole brain structure should determine large-scale function while microstructures, such as those at the level of the synapse, would be expected to determine functions at micro- and nanometer scales. N. Rouleau et al 2 structure is maintained, function is necessarily and inseparably expressed. Rouleau et al [1] have shown clear histopathological evidence that the general detail of the cerebral cortices of fixed human brains is still visibly evident decades after the cessation of function. Rouleau & Persinger [2] demonstrated that the right parahippocampal cortices (of coronal sections) of a brain preserved in ethanol-formalin-acetic acid for decades could be induced to express increased theta power upon discrete electrical current injections into the tissue
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