TEMPORAL LOBE INPUT TO THE DESCENDING MOTOR PATHWAYS

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DESCRIPTION (Adapted from applicant's abstract) : The cingulate motor area (M3 or area 24c) is a newly discovered motor representation in part of the primate brain that is located in the dorsal-most edge of the limbic lobe. Its position within this lobe, interconnections with multimodal limbic areas that process pre-processed information, and the unique motor characteristics of its neurons suggest that it represents an important interface for higher-order limbic-motor interactions. How multimodal association cortex of the limbic lobe influences voluntary motor behavior remains an unanswered but extremely important question in Neurology. The goal of this research is to characterize functional pathways that connect several limbic-affiliated parts of the temporal lobe with physiologically mapped body representations of the motor cortex which, in turn, directly influence distinct muscle groups in the face and extremities. The specific hypotheses are: 1) medial temporal lobe projections from the amygdala, temporal pole, perirhinal cortex and posterior parahippocampal gyrus terminate directly and differentially, in functionally-characterized body representations of the cingulate motor cortex and; 2) physiologically defined parts of the cingulate motor cortex that are linked to multimodal limbic areas of the temporal lobe innervate directly distinct populations of lower neurons controlling the operation of muscles in the face and extremities. To test these hypotheses, strategies combining multiple neuronal labelling techniques augmented with physiological methodology will be employed. We will map important functional linkages between parts of the medial temporal lobe and lower motor neurons innervating the upper and lower facial muscles, and muscles of the extremities affecting different movements across different joints. Characterizing functional linkages between multimodal limbic cortices and lower motor neuron centers controlling individual muscle groups will have fundamental implications for interpreting non-invasive functional imaging studies and understanding why stereotyped movements are part of seizure disorders, why abnormal activities in the form of predictable motor patterns accompany psychiatric illness, and how lesions affecting the anterior cingulate gyrus give rise to the extraordinary syndrome of akinesia.