1. Beta Synchrony and Top-Down Feedforward Processing in Visual Expectation
Steven L. Bressler
Cognitive Neurodynamics Laboratory
Center for Complex Systems & Brain Sciences
Department of Psychology
Florida Atlantic University

2. Collaborators Richard Nakamura Craig Richter Richard Copolla NIMH
FAU, ESI, ENS
Richard Nakamura
NIMH
Richard Copolla
NIMH

3. Outline Recording Paradigm Task Paradigm Analysis Paradigm
Application to Sensorimotor Cortex
Investigation of Top-down Processing in Visual Cortex

4. Nakamura-Coppola Recording Paradigm
Chronic Implant of Bipolar Electrodes
Multiple Distributed Electrode Sites
Simultaneous LFP Recording

5. Nakamura-Coppola Task Paradigm
Visual Pattern Discrimination Task
GO/NO-GO Response
Self-Initiated Trials
Prestimulus Anticipatory Period
Two Stimulus-Response Contingencies
Stimuli

6. Spectral Granger Causality
Analysis Paradigm
Spectral Coherence
Spectral Granger Causality

7. Beta-Synchronized Network in Sensorimotor Cortex Brovelli et al, PNAS, 2004

8. Poststimulus Bottom-Up Visual Processing
Feedforward & Feedback Processing (> ~45 ms)
Feedforward Sweep (0 - ~45 ms)

9. Prestimulus Top-Down Visual Processing
Top-Down Feedforward Processing (< 0 ms)

10. Prestimulus Beta-Synchronized Network in Visual Cortex Bressler et al, Stat Med, 2007
6 –TEO
Synchronized beta rhythms between V1 & extrastriate cortex (V4, TEO) form a large-scale network in visual cortex before stimulus presentation.

11. Top-Down Feedforward Beta Synchrony in Visual Cortex Richter et al
Top-Down Feedforward Beta Synchrony in Visual Cortex Richter et al., in prep
Beta rhythms are not evident in power spectra.
Prestimulus extrastriate & V1 beta rhythms are synchronized.
Synchronized beta rhythms support top-down extrastriate- to-V1, but not bottom-up V1-to-extrastriate, influences.

12. Conclusions
Areas of extrastriate visual cortex exert top-down feedforward influences on V1 in monkeys having had repeated previous exposure to a closed set of simple stimuli as the monkey awaits the stimulus but before it is presented.
The pattern of top-down influence from extrastriate cortex to V1 reflects task rules.
Classifications of prestimulus top-down influences and poststimulus V1 evoked response are correlated, suggesting that a top-down gain control mechanism enhances the V1 stimulus evoked response.