Anatomical localization of cortical beta rhythms in cat.

Beta electrocorticographic rhythms (40 Hz) develop during motionless focused attention in two distinct cortical foci in cats. A cytoarchitectonic study was performed to determine the precise location of these foci. Electrode tips recording beta rhythms were found: (i) in motor areas 4 gamma and 6a beta, in a band extending from the postcruciate cortex to the walls of the presylvian sulcus, crossing the frontal pole (anterior beta focus); (ii) in the posterior parietal associative area 5a, along the divisions of the ansate sulcus, extending to the mesial aspect of the hemispheres (posterior beta focus). The two foci are separated by areas 3, 2 and 1, where beta rhythms were never recorded. The fact that both these areas, containing giant pyramidal cells, develop a specific type of activity during immobility may have a functional meaning: area 5 may be involved in the cat as it is in the monkey in the control of motor behaviour.