Cold lesions in inferotemporal cortex produce reversible deficits in learning and retention of visual discriminations

Abstract

Cooling devices were implanted bilaterally at four points along the inferotemporal (IT) cortex in three monkeys. Cooling any of the three anterior pairs disrupted performance on a visual memory task (delayed match-to-sample) uniformly over delays of 0, 15, 30, and 45 sec. Cooling the most posterior cry ode had no effect. Cooling any of the cry odes had no effect on retention of a discrimination between horizontal and vertical stripes. With a focus at the second cryode from anterior, there was significant impairment on learning an object discrimination. With the same focus, a deficit was also found in retention of multiple object discriminations, but there was no deficit in retention of multiple black-white patterns. The anterior two cryodes were then interconnected, as were the posterior two cryodes, so that the anterior or posterior half of IT could be cooled. The animals were tested on retention of a mix of black-white patterns and objects. There were greater deficits on objects anteriorly and patterns posteriorly, but this was margin- ally below statistically acceptable levels. The four pairs of probes were each cooled separately during tests of retention of discrimination of monkey faces. A depression of scores was produced by all four cryodes, but more at the third from anterior. We suggest that IT is differentiated in the way it processes stimuli, not in the localization of such processes as attention, perception, and learning.