Synaptic properties of corticocortical connections between the primary and secondary visual cortical areas in the mouse.

Despite the importance of corticocortical connections, few published studies have investigated the functional, synaptic properties of such connections in any species, because most studies have been purely anatomical or aimed at functional features other than synaptic properties. We recently published a study of synaptic properties of connections between the primary and secondary cortical auditory areas in brain slices from the mouse, and, in the present study, we aimed to extend this by performing analogous studies of the primary and secondary visual areas (V1 and V2). We found effectively the same results. That is, connections between V1 and V2 in both directions were quite similar; in each case, the glutamatergic inputs could be classified as one of two types, Class 1B (formerly "driver") and Class 2 (formerly "modulator"). There is a clear laminar correlation for these different inputs, in terms of both the laminae of origin and those in which the recorded cells were located. Our data suggest a common pattern to the functional organization of corticocortical connectivity in the mouse cortex.