Maarten Milders

Depression biases the recognition of emotionally neutral faces

Functional abnormalities in emotion-related brain systems have been implicated in depression, and depressed patients may therefore attribute emotional valence to stimuli that are normally interpreted as emotionally neutral. The present study examined this hypothesis by comparing recognition of different facial expressions in patients with moderate to severe depression. Eighteen depressed patients and 18 matched healthy controls made a forced-choice response to briefly presented neutral, happy, and sad faces. Recognition accuracy and response time were measured. Twelve patients were retested after showing signs of symptom remission. Depressed patients and controls were equally accurate at recognizing happy and sad faces. Controls also recognized neutral faces as accurately as happy and sad faces, but depressed patients recognized neutral faces less accurately than either happy or sad faces. Depressed patients were also particularly slow to recognize neutral faces. The impairment in processing of neutral faces was still evident after symptom remission. Error analyses showed that depressed patients attributed not only sadness, but also happiness (in remission), to neutral faces. These results suggest that, unlike healthy subjects, depression-prone individuals do not seem to perceive neutral faces as unambiguous signals of emotional neutrality.

The insular cortex and the neuroanatomy of major depression

BACKGROUND The neuroanatomical substrate underlying Major Depressive Disorder (MDD) is incompletely understood. Recent reports have implicated the insular cortex. METHODS Two cohorts of participants with MDD were tested. In the first MDD cohort, we used standardised facial expression recognition tasks. In the second cohort, we focused on facial disgust recognition, a function associated with the insular cortex. T1 weighted MR imaging was used in the second cohort to test the hypothesis of abnormal insular volume being associated with impaired disgust recognition. RESULTS Disgust recognition was particularly impaired in both cohorts. In the second cohort, the magnitude of the disgust recognition deficit correlated with reduced insula grey matter volume. Exploring the idea of insula involvement in MDD further, we identified the insular cortex and the anterior cingulate cortex as key neural correlates of core symptoms, in that scores of 3 clinical scales (the Beck Depression Inventory, the Hamilton Depression Rating Scale, and the Snaith-Hamilton Pleasure Scale) correlated with grey matter volume in these structures. LIMITATIONS MDD participants were clinically representative of specialist and academic psychiatric practice in the UK and presented with robust primary diagnoses; we did not exclude common co-morbidities such as anxiety and personality disorders. CONCLUSIONS We propose that cognitive and emotional functions assumed to be associated with the insula are adversely affected in patients with MDD and that this may, therefore, represent the substrate for some core clinical features of MDD. Further exploration of the involvement of the insular cortex in MDD is warranted.

Awareness of Faces Is Modulated by Their Emotional Meaning

A central question in perception is how stimuli are selected for access to awareness. This study investigated the impact of emotional meaning on detection of faces using the attention blink paradigm. Experiment 1 showed that fearful faces were detected more frequently than neutral faces, and Experiment 2 revealed preferential detection of fearful faces compared with happy faces. To rule out image artifacts as a cause for these results, Experiment 3 manipulated the emotional meaning of neutral faces through fear conditioning and showed a selective increase in detection of conditioned faces. These results extend previous reports of preferential detection of emotional words or schematic objects and suggest that fear conditioning can modulate detection of formerly neutral stimuli.

Differential deficits in expression recognition in gene-carriers and patients with Huntington's disease.

Previous studies in symptomatic patients and asymptomatic gene-carriers of Huntingtons disease (HD) reported a differential deficit in the recognition of facial expressions of disgust. This impairment may point to involvement of the basal ganglia in the recognition of disgust. In this study, we compared the performance of 20 patients with symptoms of HD, 20 gene-carriers of HD and 20 healthy controls on two tests of facial expressions in order to further investigate the role of the basal ganglia in disgust recognition. Recognition of fear, rather than disgust, was most severely impaired in the patients, who were also impaired at recognising expressions of anger, disgust and sadness. Direct testing for a differential deficit in disgust at the group level (and at the level of individual HD cases) revealed that the patients were in fact significantly more impaired on the other negative expressions than on disgust. The gene-carriers were not impaired on any expression, although there was a trend for the gene-carriers to be poorer at recognising fearful faces than the controls. We argue that the expression recognition performance of the patients and gene-carriers simply reflects differences in task difficulty, rather than dysfunction of any mechanisms dedicated to specific emotions. In contrast to previous studies in patients or gene-carriers of HD, our findings provide no evidence for a role of the basal ganglia in the recognition of disgust and cast doubt on whether results from HD patients and gene-carriers can be used in support of a double dissociation between recognition of disgust and fear.

Orienting to threat: faster localization of fearful facial expressions and body postures revealed by saccadic eye movements

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.

Minimum presentation time for masked facial expression discrimination

Backward masking is a popular method of preventing awareness of facial expressions, but concerns have been expressed as to the effectiveness of masking in previous research, which may have resulted in unjustified claims of unconscious processing. We examined the minimum presentation time for discrimination of fearful, angry, happy and neutral faces in a backward masking task using both objective sensitivity measures, based on signal detection analysis, and subjective awareness ratings. Results from two experiments showed for all expressions the mean sensitivity and the sensitivity scores of most individual participants were above chance at presentation times of 20 ms. Awareness ratings for happy, fearful and angry also exceeded baseline ratings from 20 ms onwards. Overall sensitivity in both experiments was greatest for happy expressions, which is an agreement with previous reports. The results support the possibility of incomplete masking in earlier studies that used masking to prevent awareness of facial expressions.

Stable expression recognition abnormalities in unipolar depression

Although abnormalities in emotion recognition during a depressed episode have frequently been reported in patients with depression, less is known about the stability of these abnormalities. To examine the stability of emotion recognition abnormalities, this longitudinal study assessed patients with unipolar depression on three separate occasions at 3-monthly intervals. Recognition of sad, angry, fearful, disgusted, happy and neutral facial expressions was assessed in a matching task and a labelling task. Patients performed as well as matched healthy controls on the matching task. On the labelling task, patients showed higher accuracy and higher response bias than controls for sad expressions only, which remained stable over a 6-month interval. Over the same period, symptom severity, as measured with the Beck Depression Inventory and the Hamilton Depression Rating Scale, decreased significantly in the patient group. Furthermore, labelling performance for sad expressions was not associated with symptom severity or with changes in severity over time. This stable bias for sad expressions might signal a vulnerability factor for depression, as proposed by cognitive theories of depression.

Attentional Bias to Brief Threat-Related Faces Revealed by Saccadic Eye Movements

According to theories of emotion and attention, we are predisposed to orient rapidly toward threat. However, previous examination of attentional cueing by threat showed no enhanced capture at brief durations, a finding that may be related to the sensitivity of the manual response measure used. Here we investigated the time course of orienting attention toward fearful faces in the exogenous cueing task. Cue duration (20 ms or 100 ms) and response mode (saccadic or manual) were manipulated. In the saccade mode, both enhanced attentional capture and impaired disengagement from fearful faces were evident and limited to 20 ms, suggesting that saccadic cueing effects emerge rapidly and are short lived. In the manual mode, fearful faces impacted only upon the disengagement component of attention at 100 ms, suggesting that manual cueing effects emerge over longer periods of time. Importantly, saccades could reveal threat biases at brief cue durations consistent with current theories of emotion and attention.

Influence of emotional facial expressions on binocular rivalry

Three experiments investigated whether emotional information influences perceptual dominance during binocular rivalry. In Experiment 1, rival emotional and neutral faces in the background were coupled with grating stimuli in the foreground. Results showed that gratings paired with emotional faces dominated over those paired with neutral faces. In Experiment 2, emotional and neutral faces were presented dichoptically, without being paired with other stimuli. Dominance of emotional faces was observed. Fusion and low‐level image differences were ruled out by examining dominance periods of upright and inverted emotional and neutral faces presented as face‐house pairs (Experiment 3). Here, face stimuli dominated over house stimuli only for upright face conditions. In addition, upright emotional faces were perceived for significantly longer durations than upright neutral faces. The results provide further support for the influence of emotional meaning on binocular rivalry.

Detection of emotional faces is modulated by the direction of eye gaze.

Emotionally expressive faces have shown enhanced detectability over neutral faces, but little is known about the effect of eye gaze on detecting the presence of emotional faces. Emotional expressions and gaze direction are both cues to the intentions of another person, and gaze direction has been shown to affect recognition accuracy and perceived intensity of emotional faces. The current study showed that fearful faces were detected more frequently with an averted gaze than with a direct gaze in an attentional blink task, whereas angry and happy faces were detected more frequently with a direct gaze than with an averted gaze. The results are in line with the shared signal hypothesis and appraisal theory and suggest that selection for awareness was based on a rapid evaluation of the intentions of another person as conveyed by their facial expression and gaze direction.