Alpha rhythm in the cat thalamus.

In cats, electrocortical rhythms at about 10 Hz displaying common characteristics with the human alpha rhythm [1] were recorded from the part of the visual cortex that includes the anterior half of areas 17 (on the cortical convexity), of area 18 and of their common limit, representing the projection of the lower contralateral visual quadrant and that of the lower vertical meridian. It is shown here that activities highly correlated with these rhythms and at the same frequency, were recorded from the anterior half of the laminar dorsal lateral geniculate body (mediodorsal part of layer A), and also from a limited area medial to this nucleus. The cat thalamocortical alpha system thus appears to concern only the projection of the lower quadrants, probably excluding the area centralis itself.