Presented by: Vanessa Wong Corbetta et al.

 Inability to pay attention to space  Most common cause is stroke  Caused by focal injury to temporoparietal cortex or ventral frontal cortex  Damage in right hemisphere and neglects left side of space

 Local injury hypothesis  Injury to a brain area causes behaviour deficits that reflect local dysfunction of neurons at the site of injury  Distributed injury hypothesis  Lesion causes dysfunction in other nodes of a functional brain network, impairing processes other than those mediated by neurons at the site of injury

 Does the distributed injury hypothesis apply to spatial neglect? Hypothesis: Recovery is associated with a normalization of activity in attention networks

 11 participants (3 females, 8 males, M=60 years)  All with unilateral (right side) stroke with no damage to visual field areas and are representative of the most common lesion sites in neglect  All underwent standard rehabilitation for at least 3 months  Tested at acute(~4 weeks) and chronic (~39weeks) recovery stage

fMRI

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Independent  Valid cue or Invalid cue  Left or right visual field  Acute or chronic stage Dependent  Reaction time  Accuracy

Significant recovery from acute to chronic stage  Decrease in rightward processing bias  Greater improvement in reaction time for left than right visual field targeting  Improvement in attentional reorientating  Less reaction time and more hit rates in targeting invalid cues

 Failed to support the local injury hypothesis  Supported the distributed injury hypothesis  Recovery correlates with reactivation and rebalancing of normal activity within network

 Small sample size (N=11)  Even though all patients have clinical neglect, different areas of brain are damaged

 Strengths  Brain scans and graphs  In depth description of brain regions  Clearly presented the results found  Well organized  Short and concise  Weakness  Little detail on the rehabilitation

 The distributed impairment principle can likely be applicable to aphasia or sensory- motor deficits  Re-examination of localization of anatomical basis and functional information on specific neuropsychological disorders

Corbetta, M., Kincade, M.J., Lewis, C., Znyder, A.Z. & Sapir, A. (2005). Neural basis and recovery of spatial attention deficits in spatial neglect. Nature Neuroscience, 8 (11),