The Journal of Neuroscience, October 15, 2001, 21(20):8262-8269
The Topography of Tactile Working Memory
Justin A.
Harris,
Irina M.
Harris, and
Mathew E.
Diamond
Cognitive Neuroscience Sector, International School for Advanced
Studies, Trieste, Italy 34014
To investigate the contribution of topographically organized brain
areas to tactile working memory, we asked human subjects to compare the
frequency of two vibrations presented to the same fingertip or to
different fingertips. The vibrations ranged from 14 to 24 Hz and were
separated by a retention interval of variable length. For intervals <1
sec, subjects were accurate when both vibrations were delivered to the
same fingertip but were less accurate when the two vibrations were
delivered to different fingertips. For 1 or 2 sec intervals, subjects
performed equally well when comparing vibrations delivered either to
the same finger or to corresponding fingers on opposite hands, but they
performed poorly when the vibrations were delivered to distant fingers
on either hand. These results suggest that working memory resides
within a topographic framework. As a further test, we performed an
experiment in which the two comparison vibrations were presented to the
same fingertip but an interference vibration was presented during the retention interval. The interpolated vibration disrupted accuracy most
when delivered to the same finger as the comparison vibrations and had
progressively less effect when delivered to more distant fingers. We
conclude that topographically organized regions of somatosensory cortex
contribute to tactile working memory, possibly by holding the memory
trace across the retention interval. One stimulus can be accurately
compared with the memory of a previous stimulus if they engage
overlapping representations, but activation of the common cortical
territory by an interpolated stimulus can disrupt the memory trace.
Key words:
somatosensory; cortex; flutter vibration; SI; SII; human; finger
Copyright © 2001 Society for Neuroscience 0270-6474/01/21208262-08$05.00/0
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