Chapter 27 A proposed reorganization of the cortical input-output system

Abstract

This paper proposes a new concept for interpretation of the cerebral cortex. In this schema, the cortex is an 'imaging system' which plays an integral part in the 'functional circuit' of the living body. This functional circuit is made up of five components: the 'imaging system' of the cortex, the 'image forming system' of the basal ganglia, thalamus and cerebellum, the 'image-acting system' of the brainstem and spinal cord, the 'sensory system' of the sense organs and the 'external words.' An image constructed in the cortex yields a purposeful movement by way of its outputs through the image-acting system. The image to drive the purposeful movement is formed and accumulated in the cortex by trial and error under the control of the image-forming system. In the proposed organization outlined here, the cortex can be divided into two components, both of which have their own input and output for forming and realizing the image. One is comprised of specific areas for analyzing proper sensations from the sense organs through a specific area of the thalamus (e.g., retinal to lateral geniculate to primary visual cortex). The other system is composed of non-specific areas analyzing more diffuse input from various sensory organs through non-specific areas of the thalamus. These two systems work in concert to form fundamental and detailed images for purposeful movements through tight intercortical connections. Whereas the outputs from non-specific areas yield common behaviors regardless of sensory modality, outputs from the specific areas controls movements related to a specific sensation. Thus, it is proposed that these two systems work cooperatively: the former constructs the image and causes the initial movements, and the latter controls the movements to realize the image from the changing information of transient conditions. This model differs from other models of cortical organization which segregate cortex on the basis of sensory-related input regions and motor-related output regions. Existing data is consistent with the proposed organizational scheme. Although it may be difficult to prove specific aspects of this new model. I believe that the hypotheses contained within it will serve as an important foundation for driving future research.