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Abstract:
In two experiments, we investigated
hemispheric electroencephalography (EEG)
differences in 9(12) healthy volunteers
during pointing to lateral and central
targets. The questions addressed were
whether horizontal pointing direction
and the predictability of pointing
direction modulated hemispheric
differences (event-related
lateralizations of the EEG = ERLs). To
vary pointing direction predictability,
targets were displayed either randomly
at one of nine different positions on a
screen (random) or at the same
horizontal position in five subsequent
trials (sequenced) while vertical
positions varied randomly. Event-related
lateralizations (ERLs) varied with
pointing direction. This was true across
changes in target eccentricity and
pointing distance. Foci of the ERLs were
in premotor and posterior parietal
cortex, which might reflect the critical
involvement of these areas in the
control of visually guided
reaching. Direction predictability
reduced the parietal and premotor ERL
before pointing onset, probably
reflecting a lesser effort in visuomotor
transformation. Predictability also
added an overlying N2pc component to the
early ERL after target onset and
increased direction effects during
movement.
