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Attention. Squire et al Ch 48. 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

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slide1

Attention

Squire et al Ch 48

slide6

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

slide7

Fronto-parietal attentional control system (LIP/FEF)

Cells in LIP do not

respond to steady

stimuli

Cells respond to behaviorally relevant

stimuli

slide8

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

slide10

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.

slide11

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

slide13

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.

slide14

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.

slide15

Attentional capture or popout

Where are the bottlenecks? What is the nature of the limitation???

slide17

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.
slide18

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?