Person:

Nelson, Charles

Accumulating evidence suggests that social contexts in early life have important and complex effects on childhood psychopathology. Spurred by the lack of an explicit operational definition that could guide the study of such effects, we define a social context operationally as “a set of interpersonal conditions, relevant to a particular behavior or disorder and external to, but shaped and interpreted by, the individual child.” Building on this definition, we offer a series of recommendations for future research, based on five theoretically derived propositions: (a) Contexts are nested and multidimensional; (b) contexts broaden, differentiate, and deepen with age, becoming more specific in their effects; (c) contexts and children are mutually determining; (d) a context's meaning to the child determines its effects on the child and arises from the context's ability to provide for fundamental needs; and (e) contexts should be selected for assessment in light of specific questions or outcomes. As reflected in an increasingly rich legacy of literature on child development and psychopathology, social contexts appear to influence emerging mental disorders through dynamic, bidirectional interactions with individual children. Future research will benefit from examining not only statistical interactions between child- and context-specific factors, but also the actual transactions between children and contexts and the transduction of contextual influences into pathways of biological mediation. Because adverse contexts exert powerful effects on the mental health of children, it is important for the field to generate new, more theoretically grounded research addressing the contextual determinants of psychological well-being and disorder.

Event‐Related Potentials (ERPs) were recorded as 6‐month‐old infants were presented with a picture whose appearance was cued by a preceding tone. On a subset of these trials the picture was deleted. ERPs reflecting “surprise” to the stimulus deletion were observed on the trial following the deleted trial. These results are discussed in the context of the degree to which physically absent events act as novel events, and the limits of infants’ short‐term memory.

Event-Related Potentials were recorded over occipital and parietal scalp from left- and right-handed adults presented with a language and a non-language visual stimulus using a divided field, “oddball” paradigm. The major finding of interest was that the P300 component was larger over the left than the right hemisphere of the right-handers when the language stimulus was presented to the left hemisphere; there were no hemispheric differences for the left-handers, regardless of field of presentation. These results are discussed in the context of developing noninvasive measures to lateralize language function.

The present study examined subjects' cognitive processing of pictures of emotional and neutral facial expressions, as measured by Event-Related Potentials (ERPs). In Experiment 1, 10 subjects viewed two slides of a woman modelling angry and happy expressions; in Experiment 2, 10 subjects viewed slides of two women modelling neutral expressions. One face appeared on 20% of the trials and the other on 80% of the trials. Subjects counted the low frequency target face. In both experiments, the area of the P300 component was larger at Pz than Cz. In Experiment 1, P300 area was larger when the target was happy; peak amplitude was greater when the target was angry. No differences between neutral target faces were found for P300 amplitude or area in Experiment 2. These results suggest that emotional versus neutral facial expressions elicit different electrophysiological responses; responses are further differentiated to positive versus negative expressions.

Upright and inverted faces were used to determine whether 7-month-old infants discriminate emotional expressions on the basis of affectively relevant information. In Experiment 1, infants recognized the similarity of happy faces over changing identities and discriminated this expression from fear and anger when the stimuli were presented upright, but not when they were inverted. In Experiment 2, infants were able to discriminate happiness from fear and anger posed by a single model, regardless of the orientation of the stimuli. From these studies it was suggested that categorizing emotional expressions depends upon attending to affectively relevant, orientation-specific information, whereas the discrimination of emotional expressions can be done on a featural basis, something that remains invariant regardless of the orientation of the stimuli. In Experiment 3, infants discriminated toothy happiness posed by several models from nontoothy happiness and nontoothy anger when the stimuli were presented upright and inverted. Thus, when salient features were available, the infants based their discriminations on perceptual aspects rather than on conceptual aspects such as categories of emotions.

Event-related potentials (ERPs) and fixation duration were used to examine 6-mo-old infants' responses to frequently and infrequently presented familiar and novel events. ERPs, but not looking time, were found to distinguish between familiar events presented frequently vs infrequently and between familiar and novel events presented infrequently. It is proposed that the ERPs invoked by an infrequently presented familiar stimulus reflect the updating of working memory, whereas the ERPs invoked by a frequently presented familiar stimulus reflect stimulus encoding. Finally, because infants were unlikely to have formed a template for the novel events (each of which was presented only one time), the ERPs invoked by these stimuli probably reflected a nonspecific and possibly automatic process of novelty detection.

Event-related potentials were recorded over occipital and parietal scalp from 20 patients suffering from intractable partial complex seizures prior to undergoing a temporal lobectomy. Subjects were presented with language and nonlanguage visual stimuli using a divided-field, "oddball" paradigm. Although behavioral performance (button-press accuracy, reaction time, and running counts) was comparable across all groups (although accuracy was worse for those in the left temporal group), patients showed tremendous variability in both the amplitude and latency of the P300 response. Particularly notable was the observation that more slow wave activity was present among the patients than among the control subjects, and those scheduled for a left temporal resection evinced more amplitude reduction than those scheduled for a right temporal resection. In addition, a number of patients appeared not to show a P300 response at all. These results are discussed in the context of the utility of using noninvasive event-related potential measures to examine both memory impairment and the integrity of the neural structures that mediate memory functioning in certain patient populations.

The neural and behavioral correlates of the 4- and 8-month-old infant's ability to distinguish between frequently and infrequently presented familiar and novel events was examined. Cortical event-related potentials (ERPs) were recorded as infants were familiarized to two faces. During the test trials that followed, one of these faces was presented frequently, and the other infrequently; on each of the remaining 20% of the trials, a previously unseen, novel face was presented. Following the ERP phase, infants' looking times were recorded to pairs of faces, some of which had been seen during the ERP testing, and some of which had not. At 4 months the ERP activity invoked by the three classes of events was similar, suggesting that infants were unable to distinguish among them. At 8 months the ERP activity differed only between the Infrequent Novel events and the two classes of familiar events, but did not differ between the frequently and infrequently presented familiar events. The ERP findings complement previously reported data from 6-month-old infants in describing a trend whereby infants become increasingly able to respond to stimuli on the basis of whether they have been seen before, and not on the basis of how often they had been seen. The behavioral data at both 4 and 8 months were less clear cut than the ERP data. These findings are discussed in the context of the neural and cognitive processes involved in dissociating probability information from novelty detection.

In Reply. —Daruna and colleagues have raised a number of concerns about our article,1 to which we would like to respond.

Our understanding of the neural correlates involved in the development of attention and memory has lagged behind our knowledge of the behavioral manifestation of these abilities. This is unfortunate, as a more complete account of the brain bases for these aspects of development would likely contribute to a more thorough understanding of cognitive development in general. In this article we review previous studies from our laboratory examining recognition memory in 4‐, 6‐, and 8‐month‐old infants, and then describe more recent work with 12‐month‐old infants. From these data we conclude that the development of recognition memory lags behind that of attention. Specifically, by 4 months infants show event‐related potential (ERP) evidence of selectively attending to stimuli presented as briefly as 100 msec. Infants this same age are also able to distinguish a single novel stimulus from a single familiar stimulus. By 6 months, infants begin to distinguish between frequently and infrequently presented events, and between familiar and novel events presented infrequently. At 8 months, infants appear able to ignore how often events have been seen and attend instead to whether these events have been seen. Finally, 12‐month‐old infants once again appear to be drawn to event frequency, suggesting a shift in how attention and memory resources are allocated from 6 to 12 months. From these findings, we conclude that recognition memory is comprised of several subcomponents that are still not completely assembled by the end of the first year of life.