A method to monitor upper limb movement direction encoding in the corticomotor pathway

ABSTRACT Abnormal shoulder and elbow muscle coactivation patterns, or muscle synergies, are commonly present following stroke and may arise through dysfunctional descending neural control from the cortex. The authors evaluated a novel technique for examining corticomotor movement encoding of the upper limb in three dimensions. A 6-degree-of-freedom loadcell recorded arm twitch responses in healthy adults following stimulation over the cortex or over Erb's point in the periphery. Stimuli were delivered while the arm generated a 5 N preload in each of the 6 axial directions. The initial force twitch response to stimulation was used to construct twitch direction vectors for each preload direction. General linear mixed model analyses were used to determine the influence of stimulation location, preload direction, posture, and stimulation intensity on twitch direction. Cortical stimulation gave rise to arm twitch responses that were predictably modified by preload direction. Peripheral stimulation elicited stereotypical twitches that were not influenced by preload. Our stimulation, recording, and analysis techniques were able to capture movement encoding of the upper limb in three dimensions. Such techniques could be utilized in the stroke population to determine and monitor the presence of upper limb synergies during muscle activation.     

Developmental and sex-related differences in preschoolers' affective decision making

This study investigated developmental and sex-related differences in affective decision making, using a two-deck version of Children's Gambling Task administered to 3- and 4-year-old children. The main findings were that 4-year-old children displayed better decision-making performance than 3-year-olds. This effect was independent of developmental changes in inductive reasoning, language, and working memory. There were also sex differences in decision-making performance, which were apparent only in 3-year-old children and favored girls. Moreover, age predicted awareness of task and the correlation between the latter and decision-making performance was significant, but only in 4-year-old children. This study thus indicates that there is a remarkable developmental leap in affective decision making, whose effects are apparent around the age of 4, which according to our results, also marks the age when the correlation of declarative knowledge and decision-making performance becomes significant.     

Concurrent Validity of the Strengths and Difficulties Questionnaire in an Indigenous Pre-School Population

The strengths and difficulties questionnaire (SDQ) is a frequently used tool for universal screening of pre-schoolers’ behavioural and emotional problems. However, evidence for its concurrent validity is equivocal and has not been tested in a Māori population. We aimed to evaluate the concurrent validity of the strengths and difficulties questionnaire (SDQ) in Māori pre-schoolers (tamariki), aged 4 and 5. We carried out a prospective study of 225 tamariki (46% female) for whom a recent SDQ was available from the New Zealand Ministry of Health’s Before School Check database. A trained nurse carried out a standardised wellbeing and behavioural assessment for these children. Sensitivity, specificity, positive predictive and negative predictive values were calculated, using optimal total difficulty scale threshold values published for the SDQ (parent version SDQ-P; teacher version SDQ-T). Primary outcome: an assessment-based child referral to Child and Adolescent Mental Health Services or to a Paediatric outpatient service. Secondary outcomes: assessment-based parental referral to a parenting programme and combined referral. The optimal thresholds for child referral were low for the SDQ-P (13) and SDQ-T (7). Child referral SDQ-P: sensitivity 62%, specificity 83%, positive predictive value 0.35, negative predictive value 0.94. Child referral SDQ-T: sensitivity 77%, specificity 78%, positive predictive value 0.31, negative predictive value 0.96. The findings demonstrate optimal threshold values for referral for Māori on the SDQ-P and SDQ-T are much lower when compared to published thresholds (17 vs. 16). Sensitivity values were also low. A surveillance approach for the assessment of psychosocial problems is recommended for pre-schoolers.