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Synchronous activity within and between areas V4 and FEF in attention

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Synchronous activity within and between areas V4 and FEF in attention

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  1. Synchronous activity within and between areas V4 and FEF in attention Steve Gotts Laboratory of Brain and Cognition NIMH, NIH with: Georgia Gregoriou, Hui Hui Zhou, and Bob Desimone

  2. PFC V1 PG TE Visual Selective Attention: The ability to monitor an object or location selectively in a crowded visual scene • Biased Competition Theory • (Desimone & Duncan, 1995): • Multiple visual stimuli activate competing populations of neurons in visual cortex ("bottom up") • Attention biases this competition in favor of the attended stimulus ("top down") Cue

  3. PFC V4 V1 TE Attention and Extrastriate Cortex: Attentional modulation of neural responses is observed in extrastriate cortical regions such as V4 (e.g. Moran & Desimone, 1985; Fries, Reynolds, Rorie, & Desimone, 2001) Extrastriate lesions produce attentional deficits when salient distractors are present (e.g. De Weerd, Peralta, Desimone, & Ungerleider, 1999)

  4. Fixation RF Poor Stimulus Pair Good Stimulus 80 Good Stimulus 60 Pair Spikes per second 40 Spikes per second 20 Poor Stimulus 0 0 100 200 300 Time (ms) Reynolds et al., 1999

  5. Fixation RF Poor Stimulus Attend Good Good Stimulus 80 Good Stimulus 60 Attend Good Pair Spikes per second 40 Spikes per second 20 Poor Stimulus 0 0 100 200 300 Time (ms) Reynolds et al., 1999

  6. Fixation RF Poor Stimulus Attend Poor Good Stimulus 80 Good Stimulus 60 Pair Spikes per second 40 Spikes per second Attend Poor 20 Poor Stimulus 0 0 100 200 300 Time (ms) Reynolds et al., 1999

  7. Attentional Modulation of Neural Synchrony in Area V4 Fries, Reynolds, Rorie, and Desimone (Science, 2001)

  8. What is the source of the "top down" attentional bias in • extrastriate neurons ? • One possibility (among several) is prefrontal cortex (PFC), which • is thought to play a central role in cognitive control, executive function, • and working memory: • Feedback to temporal and parietal regions, • which in turn feedback to extrastriate • Imaging studies of selective attention in • humans commonly show PFC activation • Lesions of PFC in humans result in a • variety of attentional deficits • Rossi et al.: lesions to PFC in monkeys produces an impairment • in switching top-down control

  9. Interaction between areas FEF and V4 in attention • Record from V4 and FEF simultaneously during visual selection • Measure time course of changes in firing rate and synchrony both within and between regions FEF implicated in visual attention in monkeys and humans: Corbetta & Shulman (2002) Moore & Fallah (2001) Schall (2004) FEF V4 V1 Stimulation of FEF influences activity in V4: Moore & Armstrong (2003) Moore & Fallah (2004) TE

  10. Task: Monitor stimulus that matches cue for a color change, ignoring changes in distractors Stimuli: Oriented, drifting, sinusoidal gratings (R,G,B) at 50 eccentricity Cue: • Random cue onset, ranging from 1 sec before stimulus onset to 1 sec after • Cue color chosen randomly for each trial Targets: change between 250 ms and 3 sec post-cue (or post-stim) Distractors: 0, 1, or 2 might change

  11. Cue before stimuli: Target change: 250-3000 ms post-stimuli Fixation: 0 – 500 ms Cue on: 500 – 1500 ms Stimuli on: 1500 ms Stimuli before cue: Target change: 250-3000 ms post-cue Fixation: 0 – 1500 ms Stimuli on: 1500 ms Cue on: 1500 – 2500 ms

  12. Effect of attention on firing rates Cue before stim Cue after stim FEF (N=30 MUs) V4 (N=31 MUs)

  13. Distribution of FR separation times (targets vs distractors) Cue after stim Cue before stim

  14. Effect of attention on spike-LFP coherence Spikes in V4, LFP in V4 (different electrodes)

  15. Effect of attention on spike-LFP coherence (cont.) Spikes in FEF, LFP in FEF (different electrodes)

  16. Effect of attention on coherence across regions Spikes in FEF, LFP in V4

  17. Effect of attention on coherence across regions (cont.) Spikes in V4, LFP in FEF

  18. Effect of attention on V4-FEF phase relationships Within-region Between-region • Spike-triggered average (STA) of LFP • STAs band-pass filtered 35-80 Hz Results: • ~ Synchrony within regions • Phase-shift of 10 ms between regions

  19. Distribution of gamma phase across electrode pairs Within-region Between-region

  20. Time course of coherence: spikes in FEF, LFP in FEF

  21. Time course of coherence: spikes in V4, LFP in V4

  22. Time course of coherence: spikes in FEF, LFP in V4

  23. Time course of coherence: spikes in V4, LFP in FEF