Covert Attention Mariel Velez 4-28-2005. What is attention? . Attention is the ability to select objects of interest from the surrounding environment Involuntary vs Voluntary Spatial vs Object Overt vs. Covert. Attending to a stimulus enhances neural response to that stimulus.
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Attending to a stimulus enhances neural response to that stimulus
Salience: Represents how important a visual signal is: adds weights to incoming signals according to some feature
Ability to attend to a stimulus without shifting one’s gaze towards it
Direct gaze may be interpreted as hostile
Frontal Eye Fields
Posterier Parietal Cortex (LIP)
Mountcastle VS Goldberg and Friends
“Saccade Neurons”- presaccadic burst only when monkey makes a saccade—NOT activated by visual stimulus
MOTOR COMMAND HYPOTHESIS-presaccadic burst specific to saccade
ATTENTION-Enhancements of presaccadic activity in the absence of saccadesBushnell, Goldberg, Robinson 1981
Delayed Match to Sample Task
Attention filters out irrelevant stimuli
When one of the receptive field stimuli was the attended dot, the response of the neuron was strong whenever that dot moved in the preferred direction
(Treue and Maunsell J Neurosci. 1999 )
McAdams and Maunsell (1999) J absence of saccades Neurosci. 19:431-441.
Attention modulates V4 tuning
Monkey attends to
receptive field stimulus
Receptive Field (RF)
of a V4 neuron
Fovea’s landing point along the bar could be predicted by the degree to which V4 cells coded that bar prior to the saccade (Moore 1999)
Information about visual targets guides the saccade
How is FEF modulating individual V4 neurons?
Is the FEF an oculomotor salience map?
Change blindness-”failure to see large changes in a visual scene that occur simultaneously with a global transient (ie blanks between visual scenes)”
Cue to the area of visual change counters change blindness
Replace visual cue with SC microstimulation to see if this counters change blindness
Premotor Theory—(Rizzolatti et al. 1983, 1987)
Subjects instructed to hit button as soon as the stimulus appeared
RT increased when stimulus is presented in a location different than the attended one. An even larger increase in RT occurs when stimulus appears in non-attended location in the opposite hemifield
Premotor Theory-Motor Program controls covert orienting: distance and direction changes modify the program which increases the RT