Functional organization and restoration of the brain motorexecution after stroke

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http://scholar.google.com/scholar_url?url=http://journal.frontiersin.org/article/10.3389/fnhum.2015.00173/pdf&hl=en&sa=X&scisig=AAGBfm1Im_CcyvXtB6AkUmn3FTithBB9xQ&nossl=1&oi=scholaralrt
Abstract
Multiple cortical areas of the human brain motor system interact coherently in the low
frequency range (< 0.1 Hz), even in the absence of explicit tasks. Following stroke,
cortical interactions are functionally disturbed. How these interactions are affected and
how the functional organization is regained from rehabilitative treatments as people begin
to recover motor behaviors has not been systematically studied. We recorded the intrinsic
functional magnetic resonance imaging (fMRI) signals from 30 participants: 17 young
healthy controls and 13 aged stroke survivors. Stroke participants underwent mental
practice (MP) or both mental practice and physical therapy (MP + PT) within 14-51 days
following stroke. We investigated the network activity of five core areas in the motorexecution
network, consisting of the left primary motor area (LM1), the right primary
motor area (RM1), the left pre-motor cortex (LPMC), the right pre-motor cortex (RPMC)
and the supplementary motor area (SMA). We discovered that (i) the network activity
dominated in the frequency range 0.06 Hz – 0.08 Hz for all the regions, and for both ablebodied
and stroke participants (ii) the causal information flow between the regions: LM1
and SMA, RPMC and SMA, RPMC and LM1, SMA and RM1, SMA and LPMC, was
reduced significantly for stroke survivors (iii) the flow did not increase significantly after
MP alone and (iv) the flow among the regions during MP+PT increased significantly. We
also found that sensation and motor scores were significantly higher and correlated with
directed functional connectivity measures when the stroke-survivors underwent MP+PT
but not MP alone. The findings provide evidence that a combination of mental practice
and physical therapy can be an effective means of treatment for stroke survivors to
recover or regain the strength of motor behaviors, and that the spectra of causal
information flow can be used as a reliable biomarker for evaluating rehabilitation in
stroke survivors.