Translaminar differentiation of visually guided behaviors revealed by restricted cerebral cooling deactivation

The purpose of the present study was to test the hypothesis that superficia l and deep layers within a single cerebral region influence cerebral functi ons and behaviors in different ways. For this test, we selected posterior m iddle suprasylvian (pMS) sulcal cortex of the cat, a suspected homolog of t he area V5 complex of primates, because the region has been implicated in s everal visually guided behaviors. Cats were trained on three tasks: (1) dis crimination of direction of motion; (2) discrimination of static patterns p artially obscured by static or moving masks: and (3) visual detection and o rienting. Cooling of cryoloops in contact with pMS sulcal cortex to 8 +/- 1 degreesC selectively and completely impaired performance on the two motion discrimination tasks (1 and 2), while leaving the detection and orienting task (task 3) unimpaired. Further cooling to 3 degreesC resulted in an addi tional complete impairment of task 3. The 8 degreesC temperature resulted i n silencing of neuronal activity in the supragranular layers (I-III) and th e 3 degreesC temperature silenced activity throughout the thickness of pMS sulcal cortex. The variation in behavioral performance with covariation of cryoloop temperature and vertical, but not lateral, spread of deactivation shows that deactivation of superficial cerebral layers alone was sufficient to completely impair performance on the two motion discrimination tasks, w hereas additional deactivation of the deep layers was essential to block pe rformance on the detection and orienting task. Thus, these results show a f unctional bipartite division of labor between upper and lower cortical laye rs that is supported by efferent connectional anatomy. Similar bipartite di vision into upper and lower layers may be a general feature of cerebral cor tical architecture, signal processing and guidance of behavior.