The reviewed data show that major depressive disorder involves specific abnormalities in the cognitive and neural processing of emotional information and that these abnormalities may potentially contribute to the vulnerability for negative emotion and onset of depressive episodes.

PREFACEHumans in diverse cultures develop a similar capacity to recognize the emotional signals of different facial expressions. This capacity is mediated by a brain network that involves emotion-related brain circuits and higher-level visual representation areas. Recent studies suggest that the key components of this network begin to emerge early in life. The studies also suggest that initial biases in emotionrelated brain circuits and the early coupling of these circuits and cortical perceptual areas provides a foundation for a rapid acquisition of representations of those facial features that denote specific emotions.

To examine the ontogeny of emotional face processing, event-related potentials (ERPs) were recorded from adults and 7-month-old infants while viewing pictures of fearful, happy, and neutral faces. Face-sensitive ERPs at occipital-temporal scalp regions differentiated between fearful and neutral/happy faces in both adults (N170 was larger for fear) and infants (P400 was larger for fear). Behavioral measures showed no overt attentional bias toward fearful faces in adults, but in infants, the duration of the first fixation was longer for fearful than happy faces. Together, these results suggest that the neural systems underlying the differential processing of fearful and happy/neutral faces are functional early in life, and that affective factors may play an important role in modulating infants' face processing. KeywordsBrain Development; Electrophysiology; Emotion; Face Perception Humans glean a wealth of behaviorally and biologically significant information from others' facial expressions. Infants will crawl over a visual cliff to approach a novel toy if their mother's face displays a happy expression, whereas they avoid the cliff if their mother poses a fearful facial expression (Sorce, Emde, Campos, & Klinnert, 1985). Investigation into the neural mechanisms that underlie the processing of facial expressions may, therefore, provide a useful model as to how behaviorally and emotionally significant stimuli are processed in the human brain, and how the processing of such stimuli differs from the processing of other types of visual stimuli.Recording of event-related potentials (ERPs) provides one tool to examine the neural mechanisms of facial expression processing. ERP studies of face processing in adults have revealed that, compared to other visual objects, faces typically elicit a larger negative deflection at occipital-temporal recording sites approximately 170 ms after the stimulus onset (Bentin,

The adult brain is endowed with mechanisms subserving enhanced processing of salient emotional and social cues. Stimuli associated with threat represent one such class of cues. Previous research suggests that preferential allocation of attention to social signals of threat (i.e. a preference for fearful over happy facial expressions) emerges during the second half of the first year. The present study was designed to determine the age of onset for infants' attentional bias for fearful faces. Allocation of attention was studied by measuring event-related potentials (ERPs) and looking times (in a visual paired comparison task) to fearful and happy faces in 5- and 7-month-old infants. In 7-month-olds, the preferential allocation of attention to fearful faces was evident in both ERPs and looking times, i.e. the negative central mid-latency ERP amplitudes were more negative, and the looking times were longer for fearful than happy faces. No such differences were observed in the 5-month-olds. It is suggested that an enhanced sensitivity to facial signals of threat emerges between 5 and 7 months of age, and it may reflect functional development of the neural mechanisms involved in processing of emotionally significant stimuli.