Transient Storage of a Tactile Memory Trace in Primary Somatosensory Cortex.

Working memory is known to involve prefrontal cortex and
posterior regions of association cortex (e.g., the inferior temporal
lobes). Here, we investigate the potential role of primary
somatosensory cortex (SI) in a working memory task with tactile
stimuli. Subjects were required to compare the frequencies of
two vibrations separated by a retention interval of 1500 msec.
Their performance was significantly disrupted when we delivered
a pulse of transcranial magnetic stimulation (TMS) to the
contralateral SI early (300 or 600 msec) in the retention interval.
TMS did not affect tactile working memory if delivered to contralateral
SI late in the retention interval (at 900 or 1200 msec),
nor did TMS affect performance if delivered to the ipsilateral SI
at any time point. Primary sensory cortex thus seems to act not
only as a center for on-line sensory processing but also as a
transient storage site for information that contributes to working
memory