The distribution of transcallosal inhibition to upper extremity muscles is altered in chronic stroke

Brain stimulation enhances dispositional mindfulness in PTSD: an exploratory sham-controlled rTMS trial

Objective

Post-traumatic stress disorder (PTSD) is characterized by hypervigilance, intrusive thoughts, negative mood, and avoidant behaviors. Therapies involving mindfulness have been shown to reduce PTSD symptoms and modulate brain function. Pharmacological and brain stimulation interventions are also effective for treating PTSD. Non-invasive repeated transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (DLPFC) has been shown to regulate mood and improve PTSD symptoms.

Methods

This is a retrospective chart analysis of data collected pre-treatment, post-treatment, and at three-month follow-up in a single-site, double-blind, sham-controlled trial of right DLPFC rTMS. 31 participants diagnosed with PTSD were recruited for this pilot study. Over two weeks, 19 participants received ten sessions of either 1 Hz or 10 Hz stimulation, and nine received sham treatment.

Results

Participants in the rTMS group had a significant reduction in total Five Facet Mindfulness Questionnaire (FFMQ) scores from baseline to post-treatment, this difference was no longer observed when a false discovery rate (FDR) correction was applied. However, a significant improvement was observed in the rTMS group from baseline to the three-month follow-up in total FFMQ score and nonreactivity. This change in mindfulness scores suggests a potential delay in onset of benefits.

Conclusions

Based on our preliminary data, rTMS may improve levels of dispositional mindfulness and its specific subcomponents. Future studies could investigate brain stimulation to assess its utility for improving mindfulness and related health outcomes to reduce suffering related to PTSD. Moreover, application of this neurostimulation modality for improving mental illness and well-being more generally merits further exploration.

Clinical trial registration

https://clinicaltrials.gov/study, identifier NCT01806168.

Corticospinal and corticoreticulospinal projections have discrete but complementary roles in chronic motor behaviors after stroke

After corticospinal tract (CST) stroke, several motor deficits can emerge in the upper extremity (UE), including diminished muscle strength, motor control, and muscle individuation. Both the ipsilesional CST and contralesional corticoreticulospinal tract (CReST) innervate the paretic UE, but their relationship to motor behaviors after stroke remains uncertain. In this cross-sectional study of 14 chronic stroke and 27 healthy subjects, we examined two questions: whether the ipsilesional CST and contralesional CReST differentially relate to chronic motor behaviors in the paretic arm and hand and whether the severity of motor deficits differs by proximal versus distal location. In the paretic biceps and first dorsal interosseous muscles, we used transcranial magnetic stimulation to measure the projection strengths of the ipsilesional CST and contralesional CReST. We also used quantitative testing to measure strength, motor control, and muscle individuation in each muscle. We found that stroke subjects had muscle strength comparable to healthy subjects but poorer motor control and muscle individuation. In both paretic muscles, stronger ipsilesional CST projections related to better motor control, whereas stronger contralesional CReST projections related to better muscle strength. Stronger CST projections related to better individuation in the biceps alone. The severity of motor control and individuation deficits was comparable in the arm and hand. These findings suggest that the ipsilesional CST and contralesional CReST have specialized but complementary roles in motor behaviors of the paretic arm and hand. They also suggest that deficits in motor control and muscle individuation are not segmentally biased, underscoring the functional extent and efficacy of these pathways.NEW & NOTEWORTHY The corticospinal (CST) and corticoreticulospinal (CReST) tracts are two major descending motor pathways. We examined their relationships to motor behaviors in paretic arm and hand muscles in chronic stroke. Stronger ipsilesional CST projections related to better motor control, whereas stronger contralesional CReST projections related to better muscle strength. Stronger CST projections are also uniquely related to better biceps individuation. These findings support the notion of specialized but complementary contributions of these pathways to human motor function.

Corticospinal and corticoreticulospinal projections benefit motor behaviors in chronic stroke

After corticospinal tract (CST) stroke, several motor deficits in the upper extremity (UE) emerge, including diminished muscle strength, motor control, and muscle individuation. Both the ipsilesional CST and contralesional corticoreticulospinal tract (CReST) innervate the paretic UE and may have different innervation patterns for the proximal and distal UE segments. These patterns may underpin distinct pathway relationships to separable motor behaviors. In this cross-sectional study of 15 chronic stroke patients and 28 healthy subjects, we examined two key questions: (1) whether segmental motor behaviors differentially relate to ipsilesional CST and contralesional CReST projection strengths, and (2) whether motor behaviors segmentally differ in the paretic UE. We measured strength, motor control, and muscle individuation in a proximal (biceps, BIC) and distal muscle (first dorsal interosseous, FDI) of the paretic UE. We measured the projection strengths of the ipsilesional CST and contralesional CReST to these muscles using transcranial magnetic stimulation (TMS). Stroke subjects had abnormal motor control and muscle individuation despite strength comparable to healthy subjects. In stroke subjects, stronger ipsilesional CST projections were linked to superior motor control in both UE segments, whereas stronger contralesional CReST projections were linked to superior muscle strength and individuation in both UE segments. Notably, both pathways also shared associations with behaviors in the proximal segment. Motor control deficits were segmentally comparable, but muscle individuation was worse for distal motor performance. These results suggest that each pathway has specialized contributions to chronic motor behaviors but also work together, with varying levels of success in supporting chronic deficits.

Key points summary

Individuals with chronic stroke typically have deficits in strength, motor control, and muscle individuation in their paretic upper extremity (UE). It remains unclear how these altered behaviors relate to descending motor pathways and whether they differ by proximal and distal UE segment.In this study, we used transcranial magnetic stimulation (TMS) to examine projection strengths of the ipsilesional corticospinal tract (CST) and contralesional corticoreticulospinal tract (CReST) with respect to quantitated motor behaviors in chronic stroke.We found that stronger ipsilesional CST projections were associated with better motor control in both UE segments, whereas stronger contralesional CReST projections were associated with better strength and individuation in both UE segments. In addition, projections of both pathways shared associations with motor behaviors in the proximal UE segment.We also found that deficits in strength and motor control were comparable across UE segments, but muscle individuation was worse with controlled movement in the distal UE segment.These results suggest that the CST and CReST have specialized contributions to chronic motor behaviors and also work together, although with different degrees of efficacy.