Anhedonia is a core symptom of major depressive disorder (MDD), long thought to be associated with reduced dopaminergic function. However, most antidepressants do not act directly on the dopamine system and all antidepressants have a delayed full therapeutic effect. Recently, it has been proposed that antidepressants fail to alter dopamine function in antidepressant unresponsive MDD. There is compelling evidence that dopamine neurons code a specific phasic (short duration) reward-learning signal, described by temporal difference (TD) theory. There is no current evidence for other neurons coding a TD reward-learning signal, although such evidence may be found in time. The neuronal substrates of the TD signal were not explored in this study. Phasic signals are believed to have quite different properties to tonic (long duration) signals. No studies have investigated phasic reward-learning signals in MDD. Therefore, adults with MDD receiving long-term antidepressant medication, and comparison controls both unmedicated and acutely medicated with the antidepressant citalopram, were scanned using fMRI during a reward-learning task. Three hypotheses were tested: first, patients with MDD have blunted TD reward-learning signals; second, controls given an antidepressant acutely have blunted TD reward-learning signals; third, the extent of alteration in TD signals in major depression correlates with illness severity ratings. The results supported the hypotheses. Patients with MDD had significantly reduced reward-learning signals in many non-brainstem regions: ventral striatum (VS), rostral and dorsal anterior cingulate, retrosplenial cortex (RC), midbrain and hippocampus. However, the TD signal was increased in the brainstem of patients. As predicted, acute antidepressant administration to controls was associated with a blunted TD signal, and the brainstem TD signal was not increased by acute citalopram administration. In a number of regions, the magnitude of the abnormal signals in MDD correlated with illness severity ratings. The findings highlight the importance of phasic reward-learning signals, and are consistent with the hypothesis that antidepressants fail to normalize reward-learning function in antidepressant-unresponsive MDD. Whilst there is evidence that some antidepressants acutely suppress dopamine function, the long-term action of virtually all antidepressants is enhanced dopamine agonist responsiveness. This distinction might help to elucidate the delayed action of antidepressants. Finally, analogous to recent work in schizophrenia, the finding of abnormal phasic reward-learning signals in MDD implies that an integrated understanding of symptoms and treatment mechanisms is possible, spanning physiology, phenomenology and pharmacology.

Changes in emotional and social behaviour are relatively common following severe traumatic brain injury (TBI). Despite the serious consequences of these changes, little is known about the underlying neuropsychological deficits. In this study, we investigated which deficits might underlie these behavioural changes. The emotional and social behaviour of 17 patients with severe TBI was assessed with questionnaires, completed by the patient and a relative. Neuropsychological tests assessed recognition of emotional expressions, understanding of other people's mental states and cognitive fluency. Ratings from patients and relatives revealed changes in emotional and social behaviour after injury. Compared to matched healthy controls, the patients were impaired at recognising facial and vocal expressions of emotions, detecting social faux pas and nonverbal fluency. None of these impairments was significantly associated with the relatives' ratings of behavioural problems following TBI, although the correlation with detecting social faux pas was relatively high (r=-.61).

This study examined differences between children with autism and control children in the ability to follow another person's direction of gaze. In Expt 1, children with autism, Down syndrome and normally developing children were given two tasks. The gaze monitoring task (GMT) measured the child's spontaneous tendency to follow gaze direction in response to another person's change of head and eye movement. The visual perspective taking task (VPT) measured the child's ability to compute and report what the other person was looking at, when instructed to do so. Results showed that the majority of Down syndrome and normal children passed both tasks. In contrast, children with autism failed the GMT. This failure could not have been due to a lack of the relevant geometric skill, as they passed the VPT. This geometric skill was examined further in Expt 2, using a fine discrimination task which tested children's ability to discriminate degrees of change in the orientation of gaze. Children with autism were well within their developmental age level on this task. These results indicate a dissociation between (impaired) spontaneous monitoring and (intact) geometric analysis of gaze‐direction.

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Most studies investigating speeded orientation towards threat have used manual responses. By measuring orienting behaviour using eye movements a more direct and ecologically valid measure of attention can be made. Here, we used a forced-choice saccadic and manual localization task to investigate the speed of discrimination for fearful and neutral body and face images. Fearful/neutral body or face pairs were bilaterally presented for either 20 or 500 ms. Results showed faster saccadic orienting to fearful body and face emotions compared with neutral only at the shortest presentation time (20 ms). For manual responses, faster discrimination of fearful bodies and faces was observed only at the longest duration (500 ms). More errors were made when localizing neutral targets, suggesting that fearful bodies and faces may have captured attention automatically. Results were not attributable to low-level image properties as no threat bias, in terms of reaction time or accuracy, was observed for inverted presentation. Taken together, the results suggest faster localization of threat conveyed both by the face and the body within the oculomotor system. In addition, enhanced detection of fearful body postures suggests that we can readily recognize threat-related information conveyed by body postures in the absence of any face cues.