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Covert Attention Mariel Velez 4-28-2005

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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Covert Attention Mariel Velez 4-28-2005

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  1. Covert AttentionMariel Velez4-28-2005

  2. 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 Salience: Represents how important a visual signal is: adds weights to incoming signals according to some feature

  3. Covert Attention Ability to attend to a stimulus without shifting one’s gaze towards it Direct gaze may be interpreted as hostile

  4. 3 1 Frontal Eye Fields Posterier Parietal Cortex (LIP) 2 V4 4 SC FEF, SC saccade-only enhancement

  5. LIP, FEF, SC • Bisley JW and Goldberg ME. Neuronal activity in the lateral intraparietal area and spatial attention. Science 299:81-86, 2003 • Moore T, Armstrong KM. Selective gating of visual signals by microstimulation of frontal cortex. Nature 421:370-3, 2003   • Cavanaugh, J and Wurtz, R.H. Subcortical Modulation of Attention Counters Change Blindness. JofNeuroscience 24(50): 11236-11243, 2004

  6. Effects of attention on PPC Mountcastle VS Goldberg and Friends

  7. Recording from Area 7 (Posterior Parietal Cortex Lynch, Mountcastle, Talbot and Yin-1977 “Saccade Neurons”- presaccadic burst only when monkey makes a saccade—NOT activated by visual stimulus MOTOR COMMAND HYPOTHESIS-presaccadic burst specific to saccade

  8. ATTENTION-Enhancements of presaccadic activity in the absence of saccades Bushnell, Goldberg, Robinson 1981 • “Impossible to determine whether the relationship of neuronal response to eye movements was specific to that movement or more related to the attentional mechanisms that are associated with eye movement” • Need to dissociate the oculomotor process with the attention of the stimulus----COVERT ATTENTION

  9. Goldberg Task • What is the relationship between LIP activity and enhanced behavioral performance during attention? • Correlate firing of LIP with performance

  10. Effects of attention on visual cortex

  11. Moran and Desimone 1985 Delayed Match to Sample Task Attention filters out irrelevant stimuli

  12. Attentional effects all over visual cortex-MT, MST 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 )

  13. McAdams and Maunsell (1999) J Neurosci. 19:431-441. Attention modulates V4 tuning Monkey attends to receptive field stimulus Receptive Field (RF) of a V4 neuron RF stimulus Monkey attendselsewhere

  14. V4 • But attentional signals can represent motor preparation (intention ) AND visual selection (attention) 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

  15. Role of oculomotor mechanisms in spatial attention-FEF, SC

  16. FEF • Stimulation evokes saccades-Amplitude and direction of saccades are organized retinotopically • Goldberg-no covert attn effects. Related to saccades specifically • Reciprocally connected to lots of posterior visual areas including V4 • Should be able to drive spatial attn by perturbing oculomotor signals

  17. Moore 2003 How is FEF modulating individual V4 neurons? Is the FEF an oculomotor salience map?

  18. SC: target selection vs attention • SC presaccadic activity—gateway to the Brainstem Saccade Generator • McPeek and Keller (2004) SC inactivation causes defects in target selection by reducing behavioral salience. • SC is providing some info to visual cortical areas: • Can SC microstimulation affect attention?

  19. Wurtz’ Change Blind Task 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

  20. Change Blind Task ftp://lsr-ftp.nei.nih.gov/web/jc/cb_demo.htm

  21. Salience map • Represents how important a visual signal is: adds weights to incoming signals according to some feature • “ Activation of a particular subset of the map would strengthen the representation of whatever stimulus is positioned at the corresponding point in space, while failing to alter its identity” • Where is (are) the salience map (s)? • What other features are in a salience map? • Is there a corresponding “not salient map” ? • Are there multiple salience maps? How would these multiple maps interact? • Top down vs bottom up?

  22. Red-Bottom up Waldo-Top down

  23. LIP, FEF, SC • Bisley JW and Goldberg ME. Neuronal activity in the lateral intraparietal area and spatial attention. Science 299:81-86, 2003 • Moore T, Armstrong KM. Selective gating of visual signals by microstimulation of frontal cortex. Nature 421:370-3, 2003   • Cavanaugh, J and Wurtz, R.H. Subcortical Modulation of Attention Counters Change Blindness. JofNeuroscience 24(50): 11236-11243, 2004

  24. Covert Attention-Early Psychophysical Studies 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

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