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 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 Fronto parietal attentional control system LIP FEF Cells in LIP do not respond to steady stimuli Cells respond to behaviorally relevant stimuli 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 Summary multiple influences on goal attentional selection in LIP 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 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 Microstimulation of FEF modulates response to visual stimulus in V4 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 first stage in the visual pathway at which cortical top down feedback signals could affect information processing fMRI expts show attentional modulation of LGN even stronger than attentional effects in early visual areas 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 first stage in the visual pathway at which cortical top down feedback signals could affect information processing fMRI expts show attentional modulation of LGN even stronger than attentional effects in early visual areas Attentional capture or popout Where are the bottlenecks What is the nature of the limitation Biased competition 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 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
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