SPARED SHORT-TERM-MEMORY IN MONKEYS FOLLOWING MEDIAL TEMPORAL-LOBE LESIONS IS NOT YET ESTABLISHED - A REPLY

It is important to know whether or not short-term memory (STM) is pres erved in monkeys, as sometimes claimed, following lesions to medial te mporal lobe that disrupt longer term memory. As examined herein, the m agnitude of the longer term deficit in the delayed matching-to-sample task is well correlated with slower learning at short delays. This lea rning deficiency with short delays can be severe, e.g., failure to rea ch criterion despite ten times the number of trials required by contro l animals, yet the same animals can perform some visual discrimination s normally. Such slow learning may thus be most parsimoniously attribu ted to a STM deficit. Studies are also reviewed which compare delayed (non)matching-to-sample performance in lesioned monkeys at short and l ong delays. For those groups that received equal training at all delay s, the short-term deficit is as large as the longer term deficit. For those groups trained only at the short delay the short-term deficit is small. Caveats for future studies are discussed.