Williams syndrome: Reduced attention to other’s eyes in a hypersocial phenotype

Williams syndrome (WS) is a rare genetic disorder which leads to high social motivation as well as intellectual disability and difficulties with social interaction. Attention to others’ eyes is crucial for social understanding. Individuals with WS are typically highly attentive to faces, but there is a lack of knowledge about how they attend to other’s eyes, and the mechanisms underlying potential alterations in behavior. It has been suggested that physiological hypo-arousal enables individuals with WS to maintain their gaze longer at other’s faces. The aim of this study was to better understand if there is atypical gaze behavior among individuals with WS which might underlie their reduced social understanding and related difficulties with social interaction. We examined the speed and likelihood of gaze shifts to and from other’s eyes in individuals with WS (n = 37; mean age 23 years), and controls (n = 167) in stratified age groups (7 months, 8-12 years, 13-17 years, adults). Peak saccadic velocity was studied as an index of arousal. Individuals with WS were less likely, and slower, to orient to the eyes compared with typically developing controls in all age groups from eight years of age but did not differ from 7-month-old infants. Peak saccadic velocity was reduced in WS, replicating previous results of hypo-arousal. The results were supported by both frequentist and Bayesian statistics. Despite the hyper-social behavioral phenotype, WS is associated with reduced attention to others’ eyes. This could contribute to the difficulties with complex social interaction observed in WS.

Dopamine promotes instrumental motivation, but reduces reward-related vigour

We can be motivated when reward depends on performance, or merely by the prospect of a guaranteed reward. Performance-dependent (contingent) reward is instrumental, relying on an internal action-outcome model, whereas motivation by guaranteed reward may minimise opportunity cost in reward-rich environments. Competing theories propose that each type of motivation should be dependent on dopaminergic activity. We contrasted these two types of motivation with a rewarded saccade task, in patients with Parkinson’s disease (PD). When PD patients were ON dopamine, they had greater response vigour (peak saccadic velocity residuals) for contingent rewards, whereas when PD patients were OFF medication, they had greater vigour for guaranteed rewards. These results support the view that reward expectation and contingency drive distinct motivational processes, and can be dissociated by manipulating dopaminergic activity. We posit that dopamine promotes goal-directed motivation, but dampens reward-driven vigour, contradictory to the prediction that increased tonic dopamine amplifies reward expectation.

Dopamine promotes instrumental motivation, but reduces reward-related vigour

SummaryWe can be motivated when reward depends on performance, or merely by the prospect of a guaranteed reward. Performance-dependent (contingent) reward is instrumental, relying on an internal action-outcome model, whereas motivation by guaranteed reward may serve to minimise opportunity cost in reward-rich environments. Competing theories propose that each type of motivation should be dependent on dopaminergic activity. We contrasted these two types of motivation with a rewarded saccade task, in patients with Parkinson’s disease (PD). When PD patients were ON dopamine, they had greater response vigour (peak saccadic velocity) for contingent rewards, whereas when PD patients were OFF medication, they had greater vigour for guaranteed rewards. These results support the view that reward expectation and contingency drive distinct motivational processes, and can be dissociated by manipulating dopaminergic activity. We posit that dopamine is necessary for goal-directed motivation, but dampens reward-driven vigour, challenging the theory that tonic dopamine encodes reward expectation.

Horizontal Saccadic Velocity in Patients with Exotropia before and after Unilateral Resection and Recession Surgery

Purpose. The effects of strabismus surgery on eye movement are not known in detail, as few studies have compared saccade velocities before and after strabismus surgery. In this study, horizontal saccades were recorded using an eye-tracker in patients with only exotropia to compare the peak velocities (PVs), before and after undergoing strabismus surgery of the same type (unilateral resection and recession). Methods. Horizontal saccades of monocular vision were recorded using an eye-tracking device in 18 patients with exotropia and 20 normal subjects. All patients were examined using the same method after strabismus surgery. Results. The PVs of adduction and abduction in the patients were higher than those in the normal subjects (in dominant eye, P=0.032 for adduction and P=0.049 for abduction; in nondominant eye, P=0.016 for adduction and P=0.037 for abduction). Following the surgery, the PVs of abduction of the surgical eye (nondominant eye) decreased to the level of the normal subjects (P=0.016). However, there were no correlations between changes in the PVs and the extent of surgery (resection and recession). Conclusion. Strabismus surgery normalized the patient’s increased PV in the operated eye for abduction of horizontal saccade. Not only peripheral (extraocular muscle) but also central sensory-motor mechanisms may be involved in the changes in PV of horizontal saccades, both of which could result from the improvement of the primary eye position.