Modulation of motor cortex inhibition during manual dexterity tasks: an adaptive threshold hunting study.

Background: The ability to perform intricate movements is crucial for human motor function. The neural mechanisms underlying precision and power grips are incompletely understood. Corticospinal output from M1 is thought to be modulated by GABAA-ergic intracortical networks within M1. Objectives: To investigate the contribution of M1 intracortical inhibition to fine motor control using adaptive threshold hunting with paired-pulse TMS during pinching and grasping tasks. We hypothesised that SICI could be assessed during voluntary activation, and that corticomotor excitability and SICI modulation would be greater during pinch than grasp reflecting corticospinal control. Methods: Seventeen healthy participants performed gradual pinch and grasp tasks. Using an adaptive threshold-hunting method, paired-pulse TMS was applied in the anterior-posterior current direction to assess cortical excitability and SICI in the dominant FDI muscle. SICI and corticomotor excitability were analysed using an LMM. MEP latencies were obtained in LM, PA and AP current directions and compared using paired t-tests. Results: MEP latencies were prolonged with PA and AP coil orientations compared to LM, with AP showing the largest latency. During single-pulse TMS, there was no difference in the TMS intensity required to reach the MEP target during pinching and grasping. Greater inhibition was found during pinching compared to grasping. Conclusion: ATH with paired-pulse TMS permits investigation of intracortical inhibitory networks and their modulation during the performance of dexterous motor tasks revealing a greater modulation of GABAA-ergic inhibition contributing to SICI during pinching compared to grasping.

Fun and games: a scoping review of enjoyment and intensity assessment in studies of game-based interventions for gait rehabilitation in neurological disorders.

PURPOSE: Exergames are used to promote gait rehabilitation in patients with neurological disorders because they are believed to heighten patient enjoyment and training intensity. This scoping review evaluated whether and how studies support these claims. METHODS: A search for studies published up until October 2023 involving virtual reality or exergames for patients with neurological disorders (stroke, Parkinson's disease, multiple sclerosis, spinal cord injury) was conducted on PubMed and Scopus, with additional articles identified through backward and forward citation searching. Studies collecting gait measurements, with at least five participants and a control group were included. Data extracted were rationale, and whether participants' enjoyment of the intervention and training intensity were assessed. RESULTS: 1060 records were identified with 58 included in this review. There were 34 articles on stroke, 11 on multiple sclerosis, and 13 on Parkinson's disease. Participant enjoyment and greater training intensity were important rationales but were only evaluated in 12 and seven of the included studies, respectively. CONCLUSION: Results highlight that participant enjoyment and heightened training intensity are commonly cited rationales for using exergames in gait rehabilitation, but these effects are assumed and not routinely measured or analysed. Greater consistency is needed in the design and execution of exergaming studies for neurological disorders.

Participant enjoyment and heightened training intensity are commonly cited rationales for using exergames in gait rehabilitation, but these effects are assumed and not routinely measured or analysed.There are no agreed-upon conceptual frameworks nor validated measures of enjoyment, and this concept is commonly conflated with adherence.Intervention adherence could be improved by considering participant capabilities, opportunities and motivation at the design stage.Whether exergames increase adherence and training intensity because they are more enjoyable and motivating remains an open question.

Effect of Object Texture and Weight on Ipsilateral Corticospinal Influences During Bimanual Holding in Humans.

We tested the hypothesis that the ipsilateral corticospinal system, like the contralateral corticospinal system, controls the threshold muscle length at which wrist muscles and the stretch reflex begin to act during holding tasks. Transcranial magnetic stimulation was applied over the right primary motor cortex in 21 healthy subjects holding a smooth or coarse block between the hands. Regardless of the lifting force, motor evoked potentials in right wrist flexors were larger for the smooth block. This result was explained based on experimental evidence that motor actions are controlled by shifting spatial stretch reflex thresholds. Thus, the ipsilateral corticospinal system is involved in threshold position control by modulating facilitatory influences of hand skin afferents on motoneurons of wrist muscles during bimanual object manipulation.

The annual cycle for whimbrel populations using the Western Atlantic Flyway.

Many long-distance migratory birds use habitats that are scattered across continents and confront hazards throughout the annual cycle that may be population-limiting. Identifying where and when populations spend their time is fundamental to effective management. We tracked 34 adult whimbrels (Numenius phaeopus) from two breeding populations (Mackenzie Delta and Hudson Bay) with satellite transmitters to document the structure of their annual cycles. The two populations differed in their use of migratory pathways and their seasonal schedules. Mackenzie Delta whimbrels made long (22,800 km) loop migrations with different autumn and spring routes. Hudson Bay whimbrels made shorter (17,500 km) and more direct migrations along the same route during autumn and spring. The two populations overlap on the winter grounds and within one spring staging area. Mackenzie Delta whimbrels left the breeding ground, arrived on winter grounds, left winter grounds and arrived on spring staging areas earlier compared to whimbrels from Hudson Bay. For both populations, migration speed was significantly higher during spring compared to autumn migration. Faster migration was achieved by having fewer and shorter stopovers en route. We identified five migratory staging areas including four that were used during autumn and two that were used during spring. Whimbrels tracked for multiple years had high (98%) fidelity to staging areas. We documented dozens of locations where birds stopped for short periods along nearly all migration routes. The consistent use of very few staging areas suggests that these areas are integral to the annual cycle of both populations and have high conservation value.

Whimbrel populations differ in trans-atlantic pathways and cyclone encounters.

Each year hundreds of millions of birds cross the Atlantic Ocean during the peak of tropical cyclone activity. The extent and consequences of migrant-storm interactions remain unknown. We tracked whimbrels from two populations (Mackenzie Delta; Hudson Bay) to examine overlap between migration routes and storm activity and both the frequency and consequence of storm encounters. Here we show that Mackenzie Delta and Hudson Bay whimbrels follow different routes across the ocean and experience dramatically different rates of storm encounters. Mackenzie Delta whimbrels departed North America from Atlantic Canada, made long ([Formula: see text] = 5440 ± 120.3 km) nonstop flights far out to sea that took several days ([Formula: see text] = 6.1 ± 0.18) to complete and encountered storms during 3 of 22 crossings. Hudson Bay whimbrels departed North America from the south Atlantic Coast, made shorter ([Formula: see text] = 3643 ± 196.2 km) nonstop flights across the Caribbean Basin that took less time ([Formula: see text] = 4.5 ± 0.29) to complete and encountered storms during 13 of 18 crossings. More than half of Hudson Bay storm encounters resulted in groundings on Caribbean islands. Grounded birds required longer ([Formula: see text] = 30.4 ± 5.32 days) to complete trans-Atlantic crossings and three were lost including 2 to hunters and 1 to a predator. One of the Mackenzie Delta whimbrels was lost at sea while crossing the Intertropical Convergence Zone. Whimbrels use two contrasting strategies to cross the Atlantic including (1) a long nonstop flight around the core of storm activity with a low likelihood of encountering storms but no safety net and (2) a shorter flight through the heart of Hurricane Alley with a high likelihood of encountering storms and a safety network of islands to use in the event of an encounter. Demographic consequences of storm encounters will likely play a role in the ongoing evolution of trans-Atlantic migration pathways as global temperatures continue to rise.