Transcript ClassPresentation23

Corbetta et al.
Presented by: Vanessa Wong
 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
*
*
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 sensorymotor 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.