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Neural Correlates of Selection Since attention has a profound effect on perception, one would expect it to have some measurable effect on the brain

Neural Correlates of Selection Since attention has a profound effect on perception, one would expect it to have some measurable effect on the brain This has been confirmed with a variety of techniques: EEG, fMRI/PET, Unit Recordings

Neural Correlates of Selection Electrical activity recorded at scalp (EEG) shows differences between attended and unattended stimuli in A1 within 90 ms Hansen & Hillyard (1980)

Neural Correlates of Selection Single Unit Recordings: Delayed Match-to- Sample task MONKEY FIXATES CENTRE CROSS

Neural Correlates of Selection Single Unit Recordings: Delayed Match-to- Sample task “CUE” APPEARS AT FIXATION

Neural Correlates of Selection Single Unit Recordings: Delayed Match-to- Sample task DELAY SEVERAL SECONDS

Neural Correlates of Selection Remember that different neurons have a “preference” for different features Some stimuli excite a given neuron and others do not

Neural Correlates of Selection Single Unit Recordings: Delayed Match-to- Sample task DELAY SEVERAL SECONDS

Neural Correlates of Selection Single Unit Recordings: Delayed Match-to- Sample task MONKEY MAKES EYE MOVEMENT TO TARGET

Neural Correlates of Selection Single Unit Recordings: Delayed Match-to- Sample task Question: does attention modulate spike rate of neurons that respond to visual stimuli?

Neural Correlates of Selection Remember that different neurons have a “preference” for different features If a “good” stimulus appears, neurons tuned to the features of that stimulus are initially excited, but remain so only if attention is focused on that stimulus Chellazi et al. (1993). A neural basis for visual search in Inferior Temporal Cortex. Nature. 363, Stimulus is distractor Stimulus is target

Neural Correlates of Selection Results: Neurons in visual system respond vigorously to certain stimuli but are then sharply suppressed if a different stimulus is selected by attention

Neural Correlates of Selection Results: Neurons in visual system respond vigorously to certain stimuli but are then sharply suppressed if a different stimulus is selected by attention Interpretation: this selection is a neural correlate of the perceptual suppression of unattended information

Neural Correlates of Selection Is this a neural correlate of consciousness?

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