Jl. Ringo, SPARED SHORT-TERM-MEMORY IN MONKEYS FOLLOWING MEDIAL TEMPORAL-LOBE LESIONS IS NOT YET ESTABLISHED - A REPLY, Behavioural brain research, 59(1-2), 1993, pp. 65-72
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.