Attention

1. Attention Squire et al Ch 48

6. Spatial Neglect: lesions of parietal lobe, the frontal lobe, anterior cingulate cortex • profound inability to attend to certain spatial regions • Subcortical level - lesions of the basal ganglia or of the pulvinar • thalamic nucleus, which is heavily connected with the parietal cortex • Not sensory or motor: failure to select – therefore thought of as attentional deficit. Neglect may be object centered (above), eye centered, gaze centered, or body centered Affects imagined images. Extinction: image on good side suppresses image on bad side Note other disorders of attention: schizophrenia (disordered eye movements), ADD

7. Fronto-parietal attentional control system (LIP/FEF) Cells in LIP do not respond to steady stimuli Cells respond to behaviorally relevant stimuli

8. LIP cell responses modulated by reward towards away LIP cell responds when relevant cue is in receptive field and when left hand is used. Ie modulated by task and hand

9. Summary: multiple influences on goal (attentional) selection in LIP

10. Fronto-parietal network: FEF (frontal eye fields), SEF (supplementary eye fields, and SPL (superior parietal lobule) Note similarity of areas involved in eye movements and attention. Note also, not just spatial attention but attention to objects and features.

11. Feedback from fronto-parietal network affects responses of cells in visual cortex. attention Attention plus stimulus Potentials evoked in visual cortex Recorded on scalp when attending Right or left

12. Microstimulation of FEF modulates response to visual stimulus in V4

13. LGN receives input from multiple sources including striate cortex, the thalamic reticular nucleus (TRN), and the brain stem. (plus retina) The LGN therefore represents the firststage in the visual pathway at which cortical top-down feedback signals could affect information processing. fMRIexpts show attentional modulation of LGN (even stronger than attentional effects in early visual areas.

14. LGN receives input from multiple sources including striate cortex, the thalamic reticular nucleus (TRN), and the brain stem. (plus retina) The LGN therefore represents the firststage in the visual pathway at which cortical top-down feedback signals could affect information processing. fMRIexpts show attentional modulation of LGN (even stronger than attentional effects in early visual areas.

15. Attentional capture or popout Where are the bottlenecks? What is the nature of the limitation???

16. Biased competition

17. What is attention? • Capacity to select information from the environment and select actions to • perform • Substantial overlap between circuitry for eye movements and circuitry for • spatial attention. • Parietal – frontal network influences visual cortical areas including V1. • LGN may gate incoming visual signals. • Attention appears to act in a way that biases competition between stimuli • within a receptive field. • Attention is limited - why? • Limitations may derive from multiple levels of processing in the brain • eg sensory, motor, and sub-cortical circuitry such as basal ganglia.

18. Change Blindness: insensitivity to changes in visual scenes made during an eye movement/transient occlusion. Change blindness challenges idea that perception delivers a comprehensive representation of world. What is represented? Attended objects/regions of central interest?