Luke A. Schneider

Reduced corticomotor excitability and motor skills development in children born preterm

•  Children born preterm commonly experience motor and cognitive difficulties, but the physiology underlying this dysfunction is unknown. •  We used transcranial magnetic stimulation techniques and age‐appropriate assessments of motor skills development to investigate neurodevelopment in 151 children born between 25 and 41 weeks of gestation. •  Reduced gestational age at birth was associated with a reduction in corticomotor excitability that persisted in late childhood, poorer development of manual dexterity skills and reduced hemispheric lateralization of hand preference. •  We suggest this reduced corticomotor excitability at least partly reflects reduced white matter integrity and functional connectivity in the brain regions subserving movement control. •  These findings show that preterm birth, which is increasingly common, impacts neuromotor development and related physiology into adolescence. Whether this altered neurophysiology and motor function persists in adulthood is unknown.

A comparison of two methods for estimating 50% of the maximal motor evoked potential

OBJECTIVES Two commonly-used methods for setting stimulus intensities in transcranial magnetic brain stimulation studies were compared to determine which best approximated a motor evoked potential (MEP) of 50% of the maximal MEP amplitude (SI50); a suprathreshold intensity relative to resting motor threshold (rMT) or adjusting the intensity to evoke an MEP amplitude of 1mV. METHODS Corticomotor stimulus-response curves and rMT for the right first dorsal interosseous (FDI) muscle of 176 subjects (aged 10-74 years) were retrospectively analysed. RESULTS Regardless of subject age or sex, SI50 occurred at 127.5 ± 11.3% rMT. Except in young children, MEPs of 1 mV were significantly smaller than those evoked at SI50. CONCLUSIONS In the inactive FDI muscle, a stimulus intensity of 127-128% rMT consistently gives the best approximation of SI50 in most subjects, except perhaps young children. SIGNIFICANCE Setting TMS stimulus intensities relative to rMT provides a less variable inter-subject comparator, with respect to individual differences in corticomotor input-output characteristics, than adjusting the stimulator output to give an absolute MEP magnitude.

Motor System Development of the Preterm and Low Birthweight Infant

Despite advances in knowledge and technology, accurate prediction of later neuromotor outcomes for infants born preterm remains somewhat elusive. Here we review some of the most recent findings regarding the differential effects of preterm birth and suboptimal fetal growth on neurodevelopment. Evidence from transcranial magnetic stimulation studies is presented that suggests neuromotor development may more directly influence cognitive outcomes than previously recognised. We discuss the role of neuroplasticity in both exacerbating and improving these postnatal outcomes, and possible therapeutic targets for manipulating this. Finally, some developmental care practices that might affect long-term outcomes for these children are discussed.

Long-interval facilitation and inhibition are differentially affected by conditioning stimulus intensity over different time courses

Intracortical facilitatory and inhibitory processes in the primary motor cortex (M1) play an important role in both the preparation and execution of motor tasks. Here we aimed to (1) confirm the existence of, and further characterise, intracortical facilitation at long conditioning-test stimulus intervals at subthreshold conditioning stimulus (CS) intensities and (2) identify the threshold for long-interval intracortical inhibition (LICI) at different inter-stimulus intervals (ISIs). To examine facilitation, stimulus-response curves at ISIs of 100 and 150 ms were obtained using a range of subthreshold CS intensities. LICI stimulus-response curves were also obtained using varying CS intensities at ISIs of 100 (LICI100) and 150 ms (LICI150). Facilitation of the conditioned MEP was observed at subthreshold CS intensities at an ISI of 100 ms. LICI100 was observed at a lower CS intensity than LICI150. First, we provide evidence of a long-interval facilitation and provide some evidence consistent with a cortical origin of this facilitation. Second, the lower threshold for evoking LICI100 than LICI150 suggests an intensity-duration effect whereby a more intense CS results in longer duration LICI. Investigation of the interaction between LICI and long-interval facilitation might help to elucidate the functional importance of these processes.

The influence of motor function on processing speed in preterm and term-born children

This study investigates the relationship between motor function and processing speed in preterm children. Processing speed was compared in 145 adolescents, born 25–41 weeks gestational age, utilizing tasks including differing motor demands. The influence of motor cortex excitability and functional motor skills on task performance was assessed. For tasks with motoric demands, differences in performance between preterm and term-born children were mediated by the relationship between gestational age, corticomotor excitability, and motor function. There were no differences in non-motor processing speed task performance between preterm and term-born children. Measures of processing speed may be confounded by a timed motor component.

Family factors in adolescent problematic Internet gaming: A systematic review

Background and aims Familial influences are known to affect the likelihood of an adolescent becoming a problem gamer. This systematic review examined some of the key findings in empirical research on family factors related to adolescent problem gaming. Methods A total of 14 studies in the past decade were evaluated. Family-related variables included: (a) parent status (e.g., socioeconomic status and mental health), (b) parent–child relationship (e.g., warmth, conflict, and abuse), (c) parental influence on gaming (e.g., supervision of gaming, modeling, and attitudes toward gaming), and (d) family environment (e.g., household composition). Results The majority of studies have focused on parent–child relationships, reporting that poorer quality relationships are associated with increased severity of problem gaming. The paternal relationship may be protective against problem gaming; therefore, prevention programs should leverage the support of cooperative fathers. Discussion The intergenerational effects of problem gaming require further attention, in light of adult gamers raising their children in a gaming-centric environment. Research has been limited by a reliance on adolescent self-report to understand family dynamics, without gathering corroborating information from parents and other family members. The very high rates of problem gaming (>10%) reported in general population samples raise concerns about the validity of current screening tools. Conclusions Interventions for adolescents may be more effective in some cases if they can address familial influences on problem gaming with the active co-participation of parents, rather than enrolling vulnerable adolescents in individual-based training or temporarily isolating adolescents from the family system.

A Life-Long Approach to Physical Activity for Brain Health

It is well established that engaging in lifelong Physical activity (PA) can help delay the onset of many chronic lifestyle related and non-communicable diseases such as cardiovascular disease, type two diabetes, cancer and chronic respiratory diseases. Additionally, growing evidence also documents the importance of PA for brain health, with numerous studies indicating regular engagement in physical activities may be protective against cognitive decline and dementia in late life. Indeed, the link between PA and brain health may be different at each stage of life from childhood, mid-life and late life. Building on this emerging body of multidisciplinary research, this review aims to summarize the current body of evidence linking regular PA and brain health across the lifespan. Specifically, we will focus on the relationship between PA and brain health at three distinct stages of life: childhood and adolescence, mid-life, late life in cognitively healthy adults and later life in adults living with age-related neurodegenerative disorders such as Parkinson’s disease (PD) and Alzheimer’s disease (AD).

Maladaptive Coping Styles in Adolescents with Internet Gaming Disorder Symptoms

Problematic Internet gaming represents a potential public health concern due to its negative consequences for players and their families. It has been argued that disordered gaming may manifest more readily in vulnerable individuals who lack alternative means of coping. This study investigated Internet gaming disorder (IGD) in relation to coping, including emotion- and problem-focused coping styles. The sample was 823 adolescents (402 males) recruited from secondary schools. Participants completed surveys including the DSM-5 IGD checklist and the Brief COPE. Symptoms of IGD were significantly positively related to denial and behavioural disengagement but were not related to 10 other coping styles. Hours spent gaming and denial coping were the strongest predictors of IGD symptoms. These findings suggest that IGD may co-occur with a tendency toward denial coping, highlighting the significant challenge for practitioners in obtaining reliable assessment by self-report and developing an effective therapeutic alliance in interventions for adolescents.

The influence of short-interval intracortical facilitation when assessing developmental changes in short-interval intracortical inhibition

OBJECTIVE Measures of short-interval intracortical inhibition (SICI) can be contaminated by excitatory influences of short-interval intracortical facilitation (SICF), unless examined at individually-optimized interstimulus intervals (ISIs). We hypothesized that age-related differences in SICF would explain previously reported reduced SICI in children and adolescents compared with adults. METHODS Fifty-one participants, aged 8-29years, underwent transcranial magnetic stimulation. SICF curves were constructed to determine the ISI at which SICF was minimal (i.e. the first trough). SICI curves were constructed at this individually-determined ISI with conditioning stimulus (S1) intensities of 60-110% of active motor threshold. RESULTS There was no effect of age on the ISI corresponding with the SICF trough. However, there was a main effect of age on the amplitude of the conditioned motor-evoked potential at the different ISIs, such that children aged 8-12years demonstrated greater SICF than those aged 16-18 and 19-21years. There was no effect of age on SICI, and no interaction between age group and S1 intensity. CONCLUSIONS Compared with that in older adolescents and young adults, SICF is enhanced in children aged 8-12years. Surprisingly, this enhanced SICF does not appear to reduce the degree of SICI that can be evoked at the first trough in this age group. SIGNIFICANCE This is the first report of enhanced SICF in young children. It remains possible that enhanced SICF may have confounded earlier reports of reduced SICI in children less than 8years.

The cortisol awakening response is associated with performance of a serial sequence reaction time task

There is emerging evidence of a relationship between the cortisol awakening response (CAR) and the neural mechanisms underlying learning and memory. The aim of this study was to determine whether the CAR is associated with acquisition, retention and overnight consolidation or improvement of a serial sequence reaction time task. Salivary samples were collected at 0, 15, 30 and 45 min after awakening in 39 healthy adults on 2 consecutive days. The serial sequence reaction time task was repeated each afternoon. Participants completed the perceived stress scale and provided salivary samples prior to testing for cortisol assessment. While the magnitude of the CAR (Z score) was not associated with either baseline performance or the timed improvement during task acquisition of the serial sequence task, a positive correlation was observed with reaction times during the stable performance phase on day 1 (r=0.373, p=0.019). Residuals derived from the relationship between baseline and stable phase reaction times on day 1 were used as a surrogate for the degree of learning: these residuals were also correlated with the CAR mean increase on day 1 (r=0.357, p=0.048). Task performance on day 2 was not associated with the CAR obtained on this same day. No association was observed between the perceived stress score, cortisol at testing or task performance. These data indicate that a smaller CAR in healthy adults is associated with a greater degree of learning and faster performance of a serial sequence reaction time task. These results support recognition of the CAR as an important factor contributing to cognitive performance throughout the day.