NEURAL BASIS AND RECOVERY OF SPATIAL ATTENTION

DEFICITS IN SPATIAL NEGLECT

Presented by: Vanessa Wong

Corbetta et al.

INTRODUCTION TO SPATIAL NEGLECT 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

TWO POSSIBLE THEORIES 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

RESEARCH QUESTION Does the distributed injury hypothesis apply to spatial neglect?

Hypothesis: Recovery is associated with a normalization of activity in attention networks

EXPERIMENT 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

POSNER VISUAL ORIENTING TASK

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VARIABLESIndependent Valid cue or Invalid cue Left or right visual field Acute or chronic stage

Dependent Reaction time Accuracy

RESULTSSignificant 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

DISCUSSION Failed to support the local injury

hypothesis Supported the distributed injury

hypothesis Recovery correlates with reactivation

and rebalancing of normal activity within network

LIMITATIONS Small sample size (N=11) Even though all patients have clinical

neglect, different areas of brain are damaged

MY OPINION ON THE PAPER Strengths

Brain scans and graphs

In depth description of brain regions

Clearly presented the results found

Well organizedShort and concise

WeaknessLittle detail on the

rehabilitation

FUTURE DIRECTIONS 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), 1603-1610.

THANK YOU! ANY

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