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Abstract:
Electrical field potentials were recorded from an array of
128 electrodes (Electrical Geodesics) as 7 musically trained
subjects listened to and imagined two simple melodies. Notes in the
8-note melodies were presented and imagined at a rate of 2/sec. The
scalp topographical distribution of the potential waveform evoked
by the 1st of 5 imagined notes was very similar to that observed in
response to the previous heard note or the same note in a condition
in which subjects heard that note of the melody. The topography
associated with the 3rd and 4th imagined notes, but not the 2nd,
was effectively the inverse of that of the 1st imagined note (r
grand-average
= -0.441, -0.86, and -0.88 for the 2nd, 3rd and 4th imagined
notes, respectively). This effect obtained in 6 out of 7 subjects.
Activation of the same cortical area via projections terminating in
different cortical layers can result in scalp surface potentials of
opposite polarity. Thus, the polarity inversion observed in these
data may indicate that the same cortical areas are being activated
via different pathways during the perceptive and productive
(imagery) stages of this task.
Funded by NIH GM07257, McDonnell/Pew Center for the Cognitive
Neuroscience of Attention in Eugene, OR.
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