MNEMONIC NEURONAL-ACTIVITY IN SOMATOSENSORY CORTEX

Single-unit activity was recorded from the hand areas of the somatosen sory cortex of monkeys trained to perform a haptic delayed matching to sample task with objects of identical dimensions but different surfac e features, During the memory retention period of the task (delay), ma ny units showed sustained firing frequency change, either excitation o r inhibition. In some cases, firing during that period was significant ly higher after one sample object than after another. These observatio ns indicate the participation of somatosensory neurons not only in the perception but in the short-term memory of tactile stimuli. Neurons m ost directly implicated in tactile memory are (i) those with object-se lective delay activity, (ii) those with nondifferential delay activity but without activity related to preparation for movement, and (iii) t hose with delay activity in the haptic-haptic delayed matching task bu t no such activity in a control visuo-haptic delayed matching task, Th e results indicate that cells in early stages of cortical somatosensor y processing participate in haptic short-term memory.