ELECTROPHYSIOLOGY STUDIES OF PSYCHOMOTOR PROCESSES

  • Arezzo, Joseph C. (PI)

Project: Research project

Project Details

Description

The overall goal of this research is to define the anatomical structures,
physiological mechanisms and, whenever possible, the neurochemical
substrates of surface-recorded Event Related Potentials (ERP) associated
with sensory, motor and cognitive processes. ERP are the only real-time
physiologic measure of brain activity available in humans and they index a
wide variety of normal and deviant brain processes. We utilize
unanesthetized, behaving old world monkeys (M. fascicularis), as the
closest feasible model for the study of human ERPS. The timing and
distribution of the epidural waveform is the starting point for the
analysis. These data allow comparison with scalp-recorded ERPs in humans
and form the basis for specific hypotheses regarding underlying generators.
Intracranial electrophysiological studies utilize three complimentary
procedures, each sensitive to a different aspect of neural activity within
ensembles of neurons: 1) amplitude maxima and planes of intracortical
polarity inversion are determined for all components of the field potential
using a moveable 16 channel multicontact electrode, 2) the net firing level
of local neurons is measured by recording multiple unit activity (MUA) for
each site and for each time point in the ERP, 3) local outward and inward
neural transmembrane current flows are estimated from the field potential
data by one-dimensional current source density (CSD) analysis. These
methods in combination provide precise temporal and spatial resolution
while permitting simultaneous exploration of the entire laminar expanse of
active cortex. Thus, we can evaluate patterns of neural activation in the
regions of transmembrane current flow and the contribution of this activity
to the surface/scalp data. The sequencing of activity across laminae and
across cortical regions can also be assessed. Specific studies will include
examination of the laminar distribution of activity associated with pattern
stimulation within striate and extra-striate visual cortex, cerebral
activity associated with trained self -initiated hand movements and the
potentials related to the performance of visual and auditory discrimination
tasks. A principal focus of these studies will be examining the effects of
neurotransmitter manipulation on the intracortical and surface ERP.
Inhibitory circuitry will be manipulated by localized injections of the
GABA-A antagonist bicuculline; excitatory circuits believed to be
associated with 'Hebbian' synaptic modification will be explored by using
competitive and noncompetitive NMDA receptor antagonists. Within each
structure electrophysiologic data will be compared to known distribution of
cellular elements and the pattern of synaptic contacts as well as the
distribution of specific neurotransmitters as determined by
autoradiographic and immunocytochemical techniques.
StatusFinished
Effective start/end date1/1/906/30/95

ASJC

  • Physiology

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