1. Beta Synchrony 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. Prestimulus Top-Down Influence Pattern is Task-Specific Richter et al
Prestimulus Top-Down Influence Pattern is Task-Specific Richter et al., in prep
The data were bisected times into training and test sets for each task contingency.
Training & test sets were bootstrap resampled to give trial bivariate AR models for each striate-extrastriate pair.
A SVM was constructed from each training set.
The veridical distribution is from SVM classification of task contingency in the test sets.
The randomization distribution is from classification of contingency with the contingency labels randomly shuffled.
Multivariate Pattern Analysis by Support Vector Machine classification of prestimulus top-down beta GC patterns between 2 stimulus-response task contingencies in 2 monkeys.
veridical distribution (red); randomized distribution (blue).
contingencies: line-go/diamond-nogo vs line-nogo/diamond-go

13. Poststimulus Visual Evoked Response is Task-Specific Richter et al
Poststimulus Visual Evoked Response is Task-Specific Richter et al., in prep
Example for 1 stimulus type at 1 V1 site
The size of the N1 evoked response at a V1 site to a stimulus (e.g. right slanted line) depends on task contingency.
Mean rectified VER difference between contingencies over all stimulus types and all V1 sites

14. Prestimulus Top-Down Influence Pattern and Poststimulus Visual Evoked Response Classifications are Correlated Richter et al., in prep
Correlation between small-sample classification of unsigned distances of prestimulus top-down (extrastriateV1) GC and V1 VER amplitude with poststimulus time.

15. 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.