Visual learning suppressed by cooling the temporal pole.

Three monkeys were trained to remember colored photographs of objects over delays of 0, 15, 30, and 45 s. Then two pairs of cooling devices were implanted bilaterally over the anterior 9 mm of the temporal lobe. The devices consisted of 3 X 10 mm loops of stainless steel tubing into which cooled methanol could be pumped. One pair (anterior pair) covered the medial part of the temporal tip (area TG), starting at the rhinal sulcus and extending 3 mm laterally. The second pair (posterior pair) was placed 3 mm lateral to the anterior pair, covering the rest of TG and the anterior extreme of the inferotemporal gyri, anterior TE. Cooling either pair of probes produced a deficit at all delays, but the deficit was greater at the longest delays. There was no difference between cooling the anterior pair and cooling the posterior pair except that cooling the anterior pair greatly increased the disruption of recall that is produced by an interfering stimulus. When all four probes were cooled, which suppressed the function of the entire temporal tip, performance dropped to chance at all delays. While under this condition, the animals could not learn new visual discriminations but could perform previously learned visual discriminations. These results are consistent with the suggestion that the temporal pole is the store for the brief anterograde memory that is available to the medial temporal amnesics.