A macrophysiological study of functional organization of the claustrum

Abstract

The organization of somatic sensory, auditory, and visual projections to the claustrum was studied using macroelectrodes. Heterotopic and heterosensory convergence characterizes the entire claustrum. In acute experiments with cats with or without anesthesia, as well as in chronic experiments, responses differ when the stimulus or the recording site (or both) are changed. The results demonstrate that the claustrum is functionally a nonhomogeneous multisensory structure that electrophysiologically has three parts: anterior, intermediate, and posterior. The evolution of the somatic responses during different recording conditions and the examination of the somatic and auditory pathways show that the primary somatic (lemniscal) and auditory systems participate in the elaboration of the claustral activities; these pathways are at least partly independent. Somatic inflow arrives via a direct, as well as an indirect pathway from the nucleus ventralis posterolateralis of the thalamus. The direct pathway carries the impulses responsible for the relatively invariable components. The components which are sensitive to the recording conditions are mediated in part by the indirect pathway which reaches the claustrum after a cortical detour in area SII and in part by the extralemniscal system. Ipsilateral afferents have a double crossed pathway. Auditory inflow reaches the claustrum after a relay in the MG of the thalamus and after a cortical detour in area AI. Evidence is presented suggesting that the claustrum serves as a relay for the afferents to the amygdaloid complex.