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Abstract:
Abstract: Evidence continues to suggest that the neural
components used for motor imagery are the same as those used for
the motor act including execution. However, we suggest that the
difference between an executed motor act and its motor imagery
counterpart is a gating mechanism acting within the basal ganglia
and controlled by the insular cortex. In our experiment, using
fMRI, subjects were asked to flex (curl) the toes of their left
foot in one task (MOVEMENT) and imagine (IMAGERY) performing the
same action in a second task. Essentially all areas previously
implicated, as well as some unreported areas, in motor movement
were activated during toe flexion. There are four main differences
between the MOVEMENT and IMAGERY tasks: 1) primary motor cortex, is
not activated during the IMAGERY condition contrary to the findings
of recent fMRI studies; 2) the MOVEMENT task strongly activated
superior parietal cortex (Brodmann area 5) but this area does not
activate during IMAGERY; 3) substantial differences also exist
between the two tasks in terms of the components of the basal
ganglia activated; 4) the IMAGERY task produces weaker activation
throughout the component areas common to both tasks, a finding has
been previously reported. Further fMRI studies have demonstrated
that when this task performed with a phantom foot, the activation
pattern differs significantly from both MOVEMENT and
IMAGERY.
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