Presents the Friday Keck Center Teleconference*
The Role of Synchronized Activity during Anticipation of Visuomotor Processing.
Hualou Liang, Ph.D.,
Assistant Professor,
Health Information Sciences, Houston Health Science Center
4:00 pm Friday
21st April, 2006
(Refreshments at 3:45)
5.521 Levin Hall
Abstract: Brains are never at rest. Even in the absence of sensory stimulation, neurons are spontaneously active and form highly coherent patterns of synchronized activity. To explore the role of these dynamic patterns during anticipation of a visual stimulus, we investigated the relation of prestimulus prefrontal activity to stimulus and response parameters in a macaque monkey performing a visuomotor pattern discrimination task. Local field potentials were simultaneously recorded from five prefrontal, one motor, and six visual cortical sites in the left cerebral hemisphere. Spectral power and coherence analysis revealed that during stimulus anticipation three prefrontal sites participated in an oscillatory network synchronized in the beta frequency range. Correct trials were divided into equal groups that were rank ordered by response time. Prestimulus network power and coherence were highly correlated with early components of the visual evoked potential and with response time. DTF (measuring causal influence) measure revealed that the prefrontal cortex exerts a facilitatory "top-down" influence on visual cortical sites. The results suggest that a large-scale coordinated network in prefrontal cortex biases visual cortical areas in anticipation of stimulus appearance so that early visual stimulus processing is facilitated, in turn leading to an earlier response. Furthermore, the strength of facilitation appears to depend on the degree of network synchronization. ( http://www.sahs.uth.tmc.edu/hliang/ ).
