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Relevance of structural brain connectivity to learning and recovery from stroke.

Johansen-Berg H, Scholz J, Stagg CJ - Front Syst Neurosci (2010)

Bottom Line: The physical structure of white matter fiber bundles constrains their function.Any behavior that relies on transmission of signals along a particular pathway will therefore be influenced by the structural condition of that pathway.We provide examples of ways in which imaging measures of structural brain connectivity can inform our study of motor behavior and effects of motor training in three different domains: (1) to assess network degeneration or damage with healthy aging and following stroke, (2) to identify a structural basis for individual differences in behavioral responses, and (3) to test for dynamic changes in structural connectivity with learning or recovery.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neurology, University of Oxford Oxford, UK.

ABSTRACT
The physical structure of white matter fiber bundles constrains their function. Any behavior that relies on transmission of signals along a particular pathway will therefore be influenced by the structural condition of that pathway. Diffusion-weighted magnetic resonance imaging provides localized measures that are sensitive to white matter microstructure. In this review, we discuss imaging evidence on the relevance of white matter microstructure to behavior. We focus in particular on motor behavior and learning in healthy individuals and in individuals who have suffered a stroke. We provide examples of ways in which imaging measures of structural brain connectivity can inform our study of motor behavior and effects of motor training in three different domains: (1) to assess network degeneration or damage with healthy aging and following stroke, (2) to identify a structural basis for individual differences in behavioral responses, and (3) to test for dynamic changes in structural connectivity with learning or recovery.

No MeSH data available.


Related in: MedlinePlus

White matter degeneration following damage. (A–G) Effects of stroke. (A–F) Coronal (top row) and axial (bottom row) MR sections taken in a patient with left striatocapsular infarction, 12 days after onset. The lesion area can be localized on T1- (A,D) and T2- (B,E) weighted scans. Fractional anisotropy (FA) is not only reduced in the lesion area, but also further along the pyramidal tract (C) and in the cerebral peduncle (F, short arrows). (G) The fractional anisotropy ratio between affected and unaffected side (rFA) for the cerebral peduncle correlates with the Motricity Index. Individuals with a more symmetric fractional anisotropy distribution had better motor performance. (H,I) Example of Wallerian degeneration in the peripheral nervous system. The example shows Wallerian degeneration in a mouse peripheral nerve after cut injury. (H) Thirty-seven hours after cut injury with few individual fluorescent axons are broken into fragments. (I) Forty-two hours after cut injury most labeled axons appear fragmented. (A–G) Adapted with permission from Thomalla et al. (2004). (H,I) Adapted with permission from Beirowski et al. (2005).
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Figure 2: White matter degeneration following damage. (A–G) Effects of stroke. (A–F) Coronal (top row) and axial (bottom row) MR sections taken in a patient with left striatocapsular infarction, 12 days after onset. The lesion area can be localized on T1- (A,D) and T2- (B,E) weighted scans. Fractional anisotropy (FA) is not only reduced in the lesion area, but also further along the pyramidal tract (C) and in the cerebral peduncle (F, short arrows). (G) The fractional anisotropy ratio between affected and unaffected side (rFA) for the cerebral peduncle correlates with the Motricity Index. Individuals with a more symmetric fractional anisotropy distribution had better motor performance. (H,I) Example of Wallerian degeneration in the peripheral nervous system. The example shows Wallerian degeneration in a mouse peripheral nerve after cut injury. (H) Thirty-seven hours after cut injury with few individual fluorescent axons are broken into fragments. (I) Forty-two hours after cut injury most labeled axons appear fragmented. (A–G) Adapted with permission from Thomalla et al. (2004). (H,I) Adapted with permission from Beirowski et al. (2005).

Mentions: In the clinic, diffusion MRI has a well-established role in detecting acute stroke pathology, and is a more sensitive and specific imaging modality than conventional MRI or CT for detection of early ischemic signs in the hyperacute setting (Saur et al., 2003). Both gray and white matter are vulnerable to primary ischemic damage (Stys, 2004) and, following the acute stage, slowly evolving secondary degeneration of white matter can occur. DWI can detect these patterns of anterograde (Wallerian) and retrograde white matter tract degeneration in the days and months following stroke (Werring et al., 2000; Pierpaoli et al., 2001; Thomalla et al., 2004; Liang et al., 2007) (Figure 2). In the acute phase, reductions in FA have been observed within 16 days of stroke within distant regions within the corticospinal tract, at a time when conventional MRI was normal in this area (Thomalla et al., 2004). This decrease in FA is in line with the temporal evolution of Wallerian degeneration in these tracts, which has been demonstrated to occur as early as 2–7 days after experimental ischemic lesions in rat models (Iizuka et al., 1990). In a study by Thomalla et al. (2004), the degree of FA decrease was correlated with the patient's clinical score at the time of the MRI (Figure 2G), suggesting that these changes may have functional importance, but despite this cross-section relationship the FA decrease in the acute phase did not predict clinical outcome 3 months later.


Relevance of structural brain connectivity to learning and recovery from stroke.

Johansen-Berg H, Scholz J, Stagg CJ - Front Syst Neurosci (2010)

White matter degeneration following damage. (A–G) Effects of stroke. (A–F) Coronal (top row) and axial (bottom row) MR sections taken in a patient with left striatocapsular infarction, 12 days after onset. The lesion area can be localized on T1- (A,D) and T2- (B,E) weighted scans. Fractional anisotropy (FA) is not only reduced in the lesion area, but also further along the pyramidal tract (C) and in the cerebral peduncle (F, short arrows). (G) The fractional anisotropy ratio between affected and unaffected side (rFA) for the cerebral peduncle correlates with the Motricity Index. Individuals with a more symmetric fractional anisotropy distribution had better motor performance. (H,I) Example of Wallerian degeneration in the peripheral nervous system. The example shows Wallerian degeneration in a mouse peripheral nerve after cut injury. (H) Thirty-seven hours after cut injury with few individual fluorescent axons are broken into fragments. (I) Forty-two hours after cut injury most labeled axons appear fragmented. (A–G) Adapted with permission from Thomalla et al. (2004). (H,I) Adapted with permission from Beirowski et al. (2005).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 2: White matter degeneration following damage. (A–G) Effects of stroke. (A–F) Coronal (top row) and axial (bottom row) MR sections taken in a patient with left striatocapsular infarction, 12 days after onset. The lesion area can be localized on T1- (A,D) and T2- (B,E) weighted scans. Fractional anisotropy (FA) is not only reduced in the lesion area, but also further along the pyramidal tract (C) and in the cerebral peduncle (F, short arrows). (G) The fractional anisotropy ratio between affected and unaffected side (rFA) for the cerebral peduncle correlates with the Motricity Index. Individuals with a more symmetric fractional anisotropy distribution had better motor performance. (H,I) Example of Wallerian degeneration in the peripheral nervous system. The example shows Wallerian degeneration in a mouse peripheral nerve after cut injury. (H) Thirty-seven hours after cut injury with few individual fluorescent axons are broken into fragments. (I) Forty-two hours after cut injury most labeled axons appear fragmented. (A–G) Adapted with permission from Thomalla et al. (2004). (H,I) Adapted with permission from Beirowski et al. (2005).
Mentions: In the clinic, diffusion MRI has a well-established role in detecting acute stroke pathology, and is a more sensitive and specific imaging modality than conventional MRI or CT for detection of early ischemic signs in the hyperacute setting (Saur et al., 2003). Both gray and white matter are vulnerable to primary ischemic damage (Stys, 2004) and, following the acute stage, slowly evolving secondary degeneration of white matter can occur. DWI can detect these patterns of anterograde (Wallerian) and retrograde white matter tract degeneration in the days and months following stroke (Werring et al., 2000; Pierpaoli et al., 2001; Thomalla et al., 2004; Liang et al., 2007) (Figure 2). In the acute phase, reductions in FA have been observed within 16 days of stroke within distant regions within the corticospinal tract, at a time when conventional MRI was normal in this area (Thomalla et al., 2004). This decrease in FA is in line with the temporal evolution of Wallerian degeneration in these tracts, which has been demonstrated to occur as early as 2–7 days after experimental ischemic lesions in rat models (Iizuka et al., 1990). In a study by Thomalla et al. (2004), the degree of FA decrease was correlated with the patient's clinical score at the time of the MRI (Figure 2G), suggesting that these changes may have functional importance, but despite this cross-section relationship the FA decrease in the acute phase did not predict clinical outcome 3 months later.

Bottom Line: The physical structure of white matter fiber bundles constrains their function.Any behavior that relies on transmission of signals along a particular pathway will therefore be influenced by the structural condition of that pathway.We provide examples of ways in which imaging measures of structural brain connectivity can inform our study of motor behavior and effects of motor training in three different domains: (1) to assess network degeneration or damage with healthy aging and following stroke, (2) to identify a structural basis for individual differences in behavioral responses, and (3) to test for dynamic changes in structural connectivity with learning or recovery.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Neurology, University of Oxford Oxford, UK.

ABSTRACT
The physical structure of white matter fiber bundles constrains their function. Any behavior that relies on transmission of signals along a particular pathway will therefore be influenced by the structural condition of that pathway. Diffusion-weighted magnetic resonance imaging provides localized measures that are sensitive to white matter microstructure. In this review, we discuss imaging evidence on the relevance of white matter microstructure to behavior. We focus in particular on motor behavior and learning in healthy individuals and in individuals who have suffered a stroke. We provide examples of ways in which imaging measures of structural brain connectivity can inform our study of motor behavior and effects of motor training in three different domains: (1) to assess network degeneration or damage with healthy aging and following stroke, (2) to identify a structural basis for individual differences in behavioral responses, and (3) to test for dynamic changes in structural connectivity with learning or recovery.

No MeSH data available.


Related in: MedlinePlus