Beta Synchrony in Visual Expectation

1. Beta Synchrony in Visual Expectation Steven L. Bressler Cognitive Neurodynamics Laboratory Center for Complex Systems & Brain Sciences Department of Psychology Florida Atlantic University http://www.ccs.fau.edu/~bressler/

2. Collaborators Richard Nakamura NIMH Craig Richter FAU, ESI, ENS 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-CoppolaRecording Paradigm • Chronic Implant of Bipolar Electrodes • Multiple Distributed Electrode Sites • Simultaneous LFP Recording

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

6. Analysis Paradigm Spectral Coherence Spectral Granger Causality

7. Beta-Synchronized Network in Sensorimotor CortexBrovelli 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 CortexBressler et al, Stat Med, 2007 Synchronized beta rhythms between V1 & extrastriate cortex (V4, TEO) form a large-scale network in visual cortex before stimulus presentation. 1,2,3 – V1 5 – V4 6 –TEO

11. Top-Down Feedforward Beta Synchrony in Visual CortexRichter 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-SpecificRichter et al., in prep • The data were bisected 10000 times into training and test sets for each task contingency. • Training & test sets were bootstrap resampled to give 100 500-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-nogovs line-nogo/diamond-go

13. Poststimulus Visual Evoked Response is Task-SpecificRichter 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.