Short-term arm immobilization modulates excitability of inhibitory circuits within, and between, primary motor cortices.

Previous research has suggested that short-term immobilization of the arm may be a low-cost, non-invasive strategy to enhance the capacity for long-term potentiation (LTP)-like plasticity in primary motor cortex (M1). Short-term immobilization reduces corticospinal excitability (CSE) in the contralateral M1, and interhemispheric inhibition (IHI) from ipsi- onto contralateral M1 is increased. However, it is unclear whether reduced CSE and increased IHI are associated with changes in intracortical inhibition, which has been shown to be important for regulating neuroplasticity in M1. The current study used transcranial magnetic stimulation to evaluate the effects of short-term (6 h) arm immobilization on CSE, IHI, and intracortical inhibition measured bilaterally in 43 neurotypical young adults (23 immobilized). We replicated previous findings demonstrating that immobilization decreased CSE in, and increased IHI onto, the immobilized hemisphere, but a significant change in intracortical inhibition was not observed at the group level. Across individuals, decreased CSE was associated with a decreased short-interval intracortical inhibition, an index of GABAA -ergic inhibition, within the immobilized hemisphere only in the immobilization group. Previous research has demonstrated that decreases in GABAA -ergic inhibition are necessary for the induction of LTP-like plasticity in M1; therefore, decreased intracortical inhibition after short-term arm immobilization may provide a novel mechanism to enhance the capacity for LTP-like plasticity within M1 and may be a potential target for strategies to augment plasticity capacity to enhance motor learning in health and disease.

Wearable myoelectric interface enables high-dose, home-based training in severely impaired chronic stroke survivors.

BACKGROUND: High-intensity occupational therapy can improve arm function after stroke, but many people lack access to such therapy. Home-based therapies could address this need, but they don't typically address abnormal muscle co-activation, an important aspect of arm impairment. An earlier study using lab-based, myoelectric computer interface game training enabled chronic stroke survivors to reduce abnormal co-activation and improve arm function. Here, we assess feasibility of doing this training at home using a novel, wearable, myoelectric interface for neurorehabilitation training (MINT) paradigm. OBJECTIVE: Assess tolerability and feasibility of home-based, high-dose MINT therapy in severely impaired chronic stroke survivors. METHODS: Twenty-three participants were instructed to train with the MINT and game for 90 min/day, 36 days over 6 weeks. We assessed feasibility using amount of time trained and game performance. We assessed tolerability (enjoyment and effort) using a customized version of the Intrinsic Motivation Inventory at the conclusion of training. RESULTS: Participants displayed high adherence to near-daily therapy at home (mean of 82 min/day of training; 96% trained at least 60 min/day) and enjoyed the therapy. Training performance improved and co-activation decreased with training. Although a substantial number of participants stopped training, most dropouts were due to reasons unrelated to the training paradigm itself. INTERPRETATION: Home-based therapy with MINT is feasible and tolerable in severely impaired stroke survivors. This affordable, enjoyable, and mobile health paradigm has potential to improve recovery from stroke in a variety of settings. Clinicaltrials.gov: NCT03401762.

Null effects of therapy dog interaction on adolescent anxiety during a laboratory-based social evaluative stressor.

BACKGROUND AND OBJECTIVES: Animal-assisted interventions (AAIs) are increasingly popular as treatments to reduce anxiety. However, there is little empirical evidence testing the mechanisms of action in AAIs, especially among adolescents. We examined whether two possible mechanisms, social interaction and/or physical contact with a therapy dog, might reduce anxiety during a social stressor. DESIGN AND METHODS: To test these mechanisms, we randomly assigned 75 adolescents with low, middle, and high levels of social anxiety to complete a laboratory-based social evaluative stressor in one of three conditions: social interaction with a therapy dog (no physical interaction), social plus physical interaction with a therapy dog, or no interaction with a therapy dog. We measured self-reported anxiety and autonomic reactivity during the social stressor to assess the effects of contact with a therapy dog. RESULTS AND CONCLUSIONS: We found no evidence that the presence of a real dog, with or without the opportunity to touch it, reduced anxiety or autonomic reactivity or improved cognitive performance relative to the presence of a stuffed dog in the control condition, regardless of levels of preexisting social anxiety.Trial registration: ClinicalTrials.gov identifier: NCT03249116.

Prenatal Nicotine Exposure Disrupts Infant Neural Markers of Orienting.

Introduction: Prenatal nicotine exposure (PNE) from maternal cigarette smoking is linked to developmental deficits, including impaired auditory processing, language, generalized intelligence, attention, and sleep. Fetal brain undergoes massive growth, organization, and connectivity during gestation, making it particularly vulnerable to neurotoxic insult. Nicotine binds to nicotinic acetylcholine receptors, which are extensively involved in growth, connectivity, and function of developing neural circuitry and neurotransmitter systems. Thus, PNE may have long-term impact on neurobehavioral development. The purpose of this study was to compare the auditory K-complex, an event-related potential reflective of auditory gating, sleep preservation and memory consolidation during sleep, in infants with and without PNE and to relate these neural correlates to neurobehavioral development. Methods: We compared brain responses to an auditory paired-click paradigm in 3- to 5-month-old infants during Stage 2 sleep, when the K-complex is best observed. We measured component amplitude and delta activity during the K-complex. Results: Infants with PNE demonstrated significantly smaller amplitude of the N550 component and reduced delta-band power within elicited K-complexes compared to nonexposed infants and also were less likely to orient with a head turn to a novel auditory stimulus (bell ring) when awake. Conclusions: PNE may impair auditory sensory gating, which may contribute to disrupted sleep and to reduced auditory discrimination and learning, attention re-orienting, and/or arousal during wakefulness reported in other studies. Implications: Links between PNE and reduced K-complex amplitude and delta power may represent altered cholinergic and GABAergic synaptic programming and possibly reflect early neural bases for PNE-linked disruptions in sleep quality and auditory processing. These may pose significant disadvantage for language acquisition, attention, and social interaction necessary for academic and social success.