Di Jane Newham

INTRODUCTION: Exposure to sustained +G_z acceleration with inadequate G protection can result in G-induced loss of consciousness (G-LOC) or almost loss of consciousness (A-LOC). The UK Royal Air Force (RAF) last conducted a survey of G-LOC within their military aircrew in 2005 with interventions subsequently introduced. The aim of this study was to repeat the 2005 survey in order to evaluate the impact of those interventions.METHODS: An anonymous questionnaire requesting details of G-LOC and A-LOC events was mailed to all RAF pilots (N = 1878) and weapons systems operators (WSOs) (N = 473), irrespective of aircraft currently flown.RESULTS: The questionnaire was returned by 809 aircrew (34.4% response rate). There were 120 (14.8%) aircrew who reported at least one episode of G-LOC and 260 (32.2%) reported at least one episode of A-LOC. The reported prevalence of G-LOC in the previous 2005 survey was 20.1% (N = 454). There was an increased reporting of G-LOC in the Hawk, Tucano, and Grob Tutor aircraft, with 5 G-LOC and 19 A-LOC events reported in the Grob Tutor compared to none in 2005.DISCUSSION: The prevalence of reported G-LOC has decreased in the surveyed populations, which may be due to the introduction of centrifuge training, but also may be influenced by patterns of G exposure and other factors. Scope for further reduction remains through correct execution of the anti-G straining maneuver (AGSM) with centrifuge training early in flying training and use of a structured conditioning program to increase the general strength of muscles involved in the AGSM.Slungaard E, McLeod J, Green NDC, Kiran A, Newham DJ, Harridge SDR. Incidence of G-induced loss of consciousness and almost loss of consciousness in the Royal Air Force. Aerosp Med Hum Perform. 2017; 88(6):550–555.

Transcallosal inhibition (TCI), assessed using transcranial magnetic stimulation (TMS), can provide insight into the neurophysiology of aging and of neurological disorders such as stroke. However, the reliability of TCI using the ipsilateral silent period (iSP) has not been formally assessed, despite its use in longitudinal studies. This study aimed to determine the reliability of iSP onset latency, duration and depth in healthy young and older adults. A sample of 18 younger (mean age 27.7 years, range 1 9 – 42) and 13 older healthy adults (mean age 68.1 years, range 58 – 79) attended four sessions whereby the iSP was measured from the first dorsal interosseous (FDI) muscle of each hand. 20 single pulse stimuli were delivered to each primary motor cortex at 80 % maximum stimulator output while the participant maintained an isometric contraction of the ipsilateral FDI. The average onset latency, duration of the iSP, and depth of inhibition relative to baseline electromyography (EMG) activity was calculated for each hand in each session. Intraclass correlation coefficients (ICCs) were calculated for all four sessions, or the first two sessions only. For iSP onset latency the reliability ranged from poor to good. For iSP duration there was moderate to good reliability (ICC > 0.6). Depth of inhibition demonstrated variation in reproducibility depending on which hand was assessed and whether two or four sessions were compared. Bland and Altman analyses showed wide limits of agreement between the first two sessions, particularly for iSP depth. However, there was no systematic pattern to the variability. These results indicate that although iSP duration is reliable in healthy adults, changes in longitudinal studies should be interpreted with caution, particularly for iSP depth. Future studies are needed to determine reliability in clinical populations.

Purpose: Motor sequence learning is important for stroke recovery, but experimental tasks require dexterous movements, which are impossible for people with upper limb impairment. This makes it difficult to draw conclusions about the impact of stroke on learning motor sequences. We aimed to test a paradigm requiring gross arm movements to determine whether stroke survivors with upper limb impairment were capable of learning a movement sequence as effectively as age-matched controls. Materials and methods: In this case-control study, 12 stroke survivors (10–138 months post-stroke, mean age 64 years) attempted the task once using their affected arm. Ten healthy controls (mean 66 years) used their non-dominant arm. A sequence of 10 movements was repeated 25 times. The variables were: time from target illumination until the cursor left the central square (onset time; OT), accuracy (path length), and movement speed. Results: OT reduced with training (p < 0.05) for both groups, with no change in movement speed or accuracy (p > 0.1). We quantified learning as the OT difference between the end of training and a random sequence; this was smaller for stroke survivors than controls (p = 0.015). Conclusions: Stroke survivors can learn a movement sequence with their paretic arm, but demonstrate impairments in sequence specific learning.

Background: Non-invasive brain stimulation (NIBS) is promising as an adjuvant to rehabilitation of motor function after stroke. Despite numerous studies and reviews for the upper limb, NIBS targeting the lower limb and gait recovery after stroke is a newly emerging field of research. Purpose: To summarize findings from studies using NIBS to target the lower limb in stroke survivors. Methods: This narrative review describes studies of repetitive transcranial magnetic stimulation, paired associative stimulation and transcranial direct current stimulation with survivors of stroke. Results: NIBS appears capable of inducing changes in cortical excitability and lower limb function, but stimulation parameters and study designs vary considerably making it difficult to determine effectiveness. Conclusions: Future research should systematically assess differences in response with different stimulation parameters, test measures for determining who would be most likely to benefit and assess effectiveness with large samples before NIBS can be considered for use in clinical practice. Implications for Rehabilitation Stroke is a leading cause of disability, often resulting in dependency in activities of daily living and reduced quality of life. Non-invasive brain stimulation has received considerable interest as a potential adjuvant to rehabilitation after stroke and this review summarizes studies targeting the lower limb and gait recovery. Non-invasive brain stimulation can be used to modulate excitability of lower limb muscle representations and can lead to improvements in motor performance in stroke survivors. Non-invasive brain stimulation for gait recovery needs further investigation before translation to clinical practice is possible.