Transcript Neural Correlates of Selection

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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-toSample task
MONKEY FIXATES CENTRE CROSS
Neural Correlates of Selection
• Single Unit Recordings: Delayed Match-toSample task
“CUE” APPEARS AT FIXATION
Neural Correlates of Selection
• Single Unit Recordings: Delayed Match-toSample 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-toSample task
DELAY SEVERAL SECONDS
Neural Correlates of Selection
• Single Unit Recordings: Delayed Match-toSample task
MONKEY MAKES
EYE MOVEMENT
TO TARGET
Neural Correlates of Selection
• Single Unit Recordings: Delayed Match-toSample 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,
345-347
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?
Next time:
• memory