1. Electrophysiology of Visual Attention

2. Moran and Desimone (1985) “Classical” RF prediction: there should be no difference in responses in these two conditions Intracranial Recordings of Attentional Selection

3. Moran and Desimone (1985) Result: Intracranial Recordings of Attentional Selection “effective” stimulus at attended location Response to Target “effective” stimulus at unattended location Response to “Sample” Response to Target Response to “Sample”

4. Moran and Desimone (1985) Result: –Neuron responds vigorously only if its effective stimulus is attended –Interesting caveat: this only applies when there is an ineffective stimulus (to which the monkey attends) present in the V4 RF When the ineffective stimulus is outside of the cell’s RF, its responses are largely unmodulated Intracranial Recordings of Attentional Selection

5. What about the time course of this attention effect? Are cells modulated in advance by the cue? Or are they modulated by attention when it is shifted to the target location? What is needed is a experiment design such that the monkey orients attention after the target appears Intracranial Recordings of Attentional Selection

6. Chellazi et al ( 1993) Neural Correlates of Visual Search –Monkey is trained in a delayed match-to-sample task Cue appears 1.5 seconds before search array Monkey saccades to target –“good” and “poor” stimuli are identified for each recorded neuron Intracranial Recordings of Attentional Selection

7. Note that monkey isn’t “pre- cued” to attend to a location –Only target features are known prior to choice array onset With this paradigm it is possible to measure cell activity during delay, during search, and after selection Note that search array always contains a “good” stimulus for the recorded cell – but that might not be the target

8. Intracranial Recordings of Attentional Selection Initial response of cells is “classical”

9. Intracranial Recordings of Attentional Selection Initial response of cells is “classical” Response during delay maintains a representation of the target feature

10. Intracranial Recordings of Attentional Selection Initial response of cells is “classical” Response during delay represents the target feature Initial response to search array is “classical”

11. Intracranial Recordings of Attentional Selection About 200 ms after array onset response of cell begins to depend on attention –Response becomes more vigorous if cell is tuned to features of the target (i.e. the selected stimulus) –Response becomes suppressed if cell is tuned to a non-target distractor

12. Intracranial Recordings of Attentional Selection Conclusion: –Attentional selection of locations and/or objects has physiological correlates and consequences How does attention get to where it needs to go?