The Influence of Intrinsic Motivation on Decisions Between Actions

Extensive research explains how pre-frontal cortical areas process explicit rewards, and how pre-motor and motor cortices are recipients of that processing to energize motor behaviour. However, the specifics of motor behaviour, decisions between actions and brain dynamics when driven by no explicit reward, remain poorly understood. Are patterns of decision and motor control altered wen performing under social pressure? Are the same brain regions that typically process explicit rewards also involved in this expression of motivation? To answer these questions, we designed a novel task of decision-making between precision reaches and manipulated motivation by means of social pressure, defined by the presence or absence of virtual partner of a higher/lower aiming skill than our participants. We assessed the overall influence of this manipulation by analysing movements, decisions, pupil dilation and electro-encephalography. We show that the presence of a partner consistently increased aiming accuracy along with pupil diameter, furthermore the more skilled the partner. Remarkably, increased accuracy is attained by faster movements, consistently with a vigour effect that breaches speed-accuracy trade-offs typical of motor adaptation. This implicated an ensemble of cortical sources including pre-frontal areas, concerned with the processing of reward, but also pre-motor and occipital sources, consistent with the nature of the task. Overall, these results strongly suggest the role of social pressure as a motivational drive, enabling an increase of both vigour and accuracy in a non-trivial fashion.

The dissociable effects of reward on sequential motor behaviour

Reward has consistently been shown to enhance motor performance however its beneficial effects appear to be largely unspecific. While reward has been shown to invigorate performance, it also enhances learning and/or retention. Therefore, a mechanistic account of the effects of reward on motor behaviour is lacking. Here we tested the hypothesis that these distinct reward-based improvements are driven by dissociable reward types: explicit reward (i.e. money) and performance feedback (i.e. points). Experiment 1 showed that explicit reward instantaneously improved movement times (MT) using a novel sequential reaching task. In contrast, performance-based feedback led to learning-related improvements. Importantly, pairing both maximised MT performance gains and accelerated movement fusion. Fusion describes an optimisation process during which neighbouring sequential movements blend together to form singular actions. Results from experiment 2 served as a replication and showed that fusion led to enhanced performance speed whilst also improving movement efficiency through increased smoothness. Finally, experiment 3 showed that these improvements in performance persist for 24 hours even without reward availability. This highlights the dissociable impact of explicit reward and performance feedback, with their combination maximising performance gains and leading to stable improvements in the speed and efficiency of sequential actions.

Wrist Internal Loading and Tempo-Dependent, Effort-Reducing Motor Behaviour Strategies for Two Elite Pianists

One of the greatest challenges in reducing high rates of performance injuries among musicians is in providing them usable tools to address playing-related musculoskeletal problems (PRMP) before they become disorders. Studies in biomechanics have the potential to provide such tools. In order to better understand the mechanisms through which PRMP manifest in pianists, especially in the distal segments of the upper limbs, the current study quantifies wrist internal loading (WIL) and wrist impact loading frequency. It does so while discussing pianists’ motor behaviours and observed effort-reduction strategies in the wrists as a function of anthropometry. This concept has great utility for performers. A VICON 3D motion capture system documented two expert pianists performing a B major scale, hands together, at 4, 6, 8, 9, and 10 notes/sec. Biomechanical modeling quantified WIL. Changes in motor behaviour were observed at 8 notes/sec. Individualized anthropometry influenced the range of motor strategies available to each pianist. The pianist with the larger hand span employed a flexion/extension wrist strategy as a compensatory means for effort reduction, while the pianist with the smaller hand span employed a radial/ ulnar deviation strategy. The current study provides a new perspective in addressing PRMP among pianists by rationalizing anthropometric potentials in terms of ergonomic parameters and documenting the availability and utility of effort-reduction strategies in the wrists during piano performance as performers consider PRMP risk and avoidance.

Motor training and attention engagement in early infancy: a pilot study

The following study evaluated the long-term effects of motor training on 3-month-old infants regarding motor development and attentional development in a natural setting (i.e., when interacting with parents). Infants were trained daily for two weeks by their parents. Motor activity and attention were assessed prior to and after training, and at 5 months of age. Infants were either actively (received opportunities to grasp objects) or passively (received no such opportunities) trained. Overall, results did not reveal a difference in motor or attentional tendencies between the active and passive training groups, although actively trained infants showed tendencies towards increased motor behaviour relative to passively trained infants. Infants in both groups demonstrated increased motor behaviour across assessments, and results were inconclusive regarding attentional tendencies during parent-infant interactions in each group. Findings from the present study provide an important first step from which future studies can determine the long-term effects of motor training.

Motor training and attention engagement in early infancy: a pilot study

The following study evaluated the long-term effects of motor training on 3-month-old infants regarding motor development and attentional development in a natural setting (i.e., when interacting with parents). Infants were trained daily for two weeks by their parents. Motor activity and attention were assessed prior to and after training, and at 5 months of age. Infants were either actively (received opportunities to grasp objects) or passively (received no such opportunities) trained. Overall, results did not reveal a difference in motor or attentional tendencies between the active and passive training groups, although actively trained infants showed tendencies towards increased motor behaviour relative to passively trained infants. Infants in both groups demonstrated increased motor behaviour across assessments, and results were inconclusive regarding attentional tendencies during parent-infant interactions in each group. Findings from the present study provide an important first step from which future studies can determine the long-term effects of motor training.

Activation of thalamo-cortical circuits with posterior hypothalamic nucleus deep brain stimulation

The posterior hypothalamic nucleus (PH) has extensive anatomical connections to motor, cognitive, visceral, and homeostatic areas of the brain and serves as a crucial subcortical modulator of behaviour. Previous studies have demonstrated that deep brain stimulation (DBS) of this area can lead to powerful activation of motor behaviour, overcoming two rodent models of parkinsonian akinesia by increasing neocortical excitability. However, it is unclear how the PH may mediate this increase in neocortical excitability. In the present study, we examined the role of the thalamus in the PH-DBS mediated increase in neocortical excitability. In urethane anaesthetized animals, we demonstrate that PH-DBS elicits increased spiking activity in the motor thalamus (VL) that receives direct afferents from the PH that precedes the increase in spiking activity in the corresponding motor cortex. In contrast, in the somatosensory thalamus (VPM) where PH afferents are sparse at best, PH-DBS did not elicit an increase in thalamic activity despite of a slight increase in the corresponding somatosensory cortical spiking. Current source density analyses suggest a thalamo-cortical mechanism for motor cortex activation whereas a cortico-cortical activation mechanism is involved in somatosensory cortical activation. Inactivation of the VL resulted in the abolition of motor cortex spiking despite of the persistence of desynchronized field potential activity. Collectively, these data suggest indirect orthodromic activation of PH output fibres to the thalamus mediates increased neocortical excitation, which may spread through cortico-cortical connections and lead to an increase in integrated, non-stereotypical motor behaviour.

Transient beta activity and connectivity during sustained motor behaviour

Neural oscillations are thought to play a central role in orchestrating activity states between distant neural populations. In humans, long-range neural connectivity has been particularly well characterised for 13-30 Hz beta activity which becomes phase coupled between the motor cortex and the contralateral muscle during isometric contraction. Based on this and related observations, beta activity and connectivity have been linked to sustaining stable cognitive and motor states – or the ‘status quo’ – in the brain. Recently, however, beta activity has been shown to be short-lived, as opposed to sustained – though so far this has been reported for regional beta activity in tasks without sustained motor demands. Here, we measured magnetoencephalography (MEG) and electromyography (EMG) in 18 human participants performing an isometric-contraction (gripping) task designed to yield sustained behavioural output. If cortico-muscular beta connectivity is directly responsible for sustaining a stable motor state, then beta activity should be (or become) sustained in this context. In contrast, we found that beta activity and connectivity with the downstream muscle were transient, even when participants engaged in sustained gripping. Moreover, we found that sustained motor requirements did not prolong beta-event duration in comparison to rest. These findings suggest that long-range neural synchronisation may entail short ‘bursts’ of frequency-specific connectivity, even when task demands – and behaviour – are sustained.HighlightsTrial-average 13-30 Hz beta activity and connectivity with the muscle appear sustained during stable motor behaviourSingle-trial beta activity and connectivity are short-lived, even when motor behaviour is sustainedSustained task demands do not prolong beta-event duration in comparison to resting state