[Abstract Title]. - Society for Neuroscience

Abstract: Previous work from our lab has shown that a new cortical forelimb (FL)
representation emerges in peri-infarct motor (M1) and hindlimb (HL) cortex 2-3 months after
unilateral focal ischemic stroke. Although these results clearly show extensive functional remapping
in a stroke-recovered mouse, we still do not know how quickly these functional
changes in cortical responsiveness occur after stroke; nor do we know how well functional remapping
correlates temporally, with behavioural recovery of forelimb use. To this end, we
utilized voltage sensitive dye imaging in vivo to examine forelimb-evoked cortical responses in
adult mice at 1 week, 2-3 or 12 months after FL cortex stroke. Our preliminary analysis indicated
that 1 week after stroke when behavioural deficits in forelimb use are most prominent, forelimbevoked
responses were virtually absent in the contralateral M1/HL regions, with faint, but
detectable responses in the surviving piece of FL cortex. Of note, neuronal responses in the periinfarct
M1/HL cortex could still be evoked by hindlimb stimulation, suggesting that peri-infarct
cortex was indeed functionally responsive. However after 2-3 or 12 months recovery, forelimbevoked
responses first appeared in the surviving remnant of FL cortex which propagated to, and
led to robust, sustained responses within peri-infarct M1/HL cortical areas (3-4 fold increase in
response duration). Collectively, these results indicate that much of the functional re-mapping of
the FL cortex occurs within the first 2-3 months after stroke, and is characterized by an initial
loss of cortical responsiveness to the impaired forelimb which gradually recovers, and reemerges
in peri-infarct M1/HL cortex. Currently, we are employing in vivo two-photon imaging
to investigate what structural modifications (eg changes in intracortical or thalamocortical
connectivity) might form the basis for the progressive recovery/re-mapping of the FL
representation.
Disclosures: C.E. Brown , None; T.H. Murphy, None.
Poster
239. Structural Plasticity at Synapses I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 239.15/E12
Topic: B.08.i. Structural plasticity
Support: NIDA 5P01DA021633-02
Office of Naval Research N00014-02-0879
NIDA R37DA04294
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