Subcortical Functions

the totality of physiological processes related to the activity of the individual subcortical structures of the brain or to their system.

Anatomically, the subcortical structures include all the ganglia lying between the cerebral cortex and the medulla oblongata. However, from the functional standpoint, the term “subcortical functions” was generally applied to the functions of the “nearest subcortex” (I. P. Pavlov), which is more closely associated with the cerebral cortex and embraces the subcortical structures lying between the cortex and the corpora quad-rigemina, including the thalamus, hypothalamus, caudate nucleus, and globus pallidus. Subsequent elucidation of the physiology of the reticular formations of the thalamus and brainstem showed that these structures are directly concerned with the functions of the cerebral cortex and are bound to it by complex relations. The cerebral cortex as the chief organ of new temporary connections and as the integrator of the most complex adaptations to the external world may perform this function only if it continuously receives generalized and local ascending stimulative influences from the subcortical apparatus. Elimination of the influences immediately destroys the very delicate cortical integration, causes loss of consciousness and transition to a state of sleep, and reversibly impairs the capacity of the cerebral cortex to perform associative activity.

In view of the stimulative influence of the subcortical structures on the cerebral cortex, Pavlov thought that “emotions strengthen the cortical cells” and that the cortex is constantly affected by the “blind force” of the subcortex. All these findings make it difficult to consider the cerebral cortex apart from the subcortical structures. However, despite the feature of cortical-subcortical relations, each of the levels of neural organization has completely specific functions and localizations and contributes its own share to the final integrative activity of the body as a whole. This fact justifies singling out the physiological characteristics of the subcortical structures.