Although several studies have examined anterior asymmetric brain electrical activity and cortisol in infants, children, and adults, the direct association between asymmetry and cortisol has not systematically been reported. In nonhuman primates, greater relative right anterior activation has been associated with higher cortisol levels. The current study examines the relation between frontal electroencephalographic (EEG) asymmetry and cortisol (basal and reactive) and withdrawal-related behaviors (fear and sadness) in 6-month-old infants. As predicted, the authors found that higher basal and reactive cortisol levels were associated with extreme right EEG asymmetry. EEG during the withdrawal-negative affect task was associated with fear and sadness behaviors. Results are interpreted in the context of the previous primate work, and some putative mechanisms are discussed.
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Right-handed subjects tend to look to the left when answering affective questions. The relative shift in gaze from right to left is accentuated when the questions also involve spatial manipulation and attenuated when the questions require verbal manipulation. The data support the hypothesis that the right hemisphere has a special role in emotion in the intact brain, and that predictable patterning of hemispheric activity can occur when specific combinations of cognitive and affective processes interact.
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This study, based on a sample of 172 children, examined the relation between average afternoon salivary cortisol levels measured at home at age 4.5 years and socioemotional adjustment a year and a half later, as reported by mothers, fathers, and teachers. Cortisol levels were hypothesized to be positively associated with withdrawal-type behaviors (e.g., internalizing, social wariness) and inversely related to approach-type behaviors, both negative and positive (e.g., externalizing, school engagement). Higher cortisol levels at age 4.5 predicted more internalizing behavior and social wariness as reported by teachers and mothers, although child gender moderated the relation between cortisol and mother report measures. An inverse relation was found between boys' cortisol levels and father report of externalizing behavior. A marginal inverse relation was found between child cortisol levels and teacher report of school engagement. Behavior assessed concurrently with cortisol collection did not account for the prospective relations observed,suggesting that cortisol adds uniquely to an understanding of behavioral development.
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This paper reports three studies showing sex differences in EEG asymmetry during self-generated cognitive and affective tasks. In the first experiment, bilateral EEG, quantified for alpha on-line, was recorded from right-handed subjects while they either whistled, sang or recited lyrics of familiar songs. The results revealed significant asymmetry between the whistle and talk conditions only for subjects with no familial left-handedness and, within this group, only for females and not for males. In the second experiment, bilateral EEG was recorded while right-handed subjects (with no familial left-handedness) self-induced covert affective and non-affective states. Results revealed significantly greater relative right-hemisphere activation during emotion versus non-emotion trials only in females; males showed no significant task-dependent shifts in asymmetry between conditions. The third experiment was designed to test the hypothesis that females show greater percent time asymmetry than males during biofeedback training for symmetrical and asymmetrical EEG patterns. Results confirmed this prediction as well as indicating that females show better control of such asymmetrical cortical patterning. These findings provide new neuropsychological support for the hypothesis of greater bilateral flexibility in females during self-generation tasks.
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Social class is shaped by an individual's material resources as well as perceptions of rank vis-à-vis others in society, and in this article, we examine how class influences behavior. Diminished resources and lower rank create contexts that constrain social outcomes for lower-class individuals and enhance contextualist tendencies--that is, a focus on external, uncontrollable social forces and other individuals who influence one's life outcomes. In contrast, abundant resources and elevated rank create contexts that enhance the personal freedoms of upper-class individuals and give rise to solipsistic social cognitive tendencies--that is, an individualistic focus on one's own internal states, goals, motivations, and emotions. Guided by this framework, we detail 9 hypotheses and relevant empirical evidence concerning how class-based contextualist and solipsistic tendencies shape the self, perceptions of the social environment, and relationships to other individuals. Novel predictions and implications for research in other socio-political contexts are considered.
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We used fMRI to examine amygdala activation in response to fearful facial expressions, measured over multiple scanning sessions. 15 human subjects underwent three scanning sessions, at 0, 2 and 8 weeks. During each session, functional brain images centered about the amygdala were acquired continuously while participants were shown alternating blocks of fearful, neutral and happy facial expressions. Intraclass correlation coefficients calculated across the sessions indicated stability of response in left amygdala to fearful faces (as a change from baseline), but considerably less left amygdala stability in responses to neutral expressions and for fear versus neutral contrasts. The results demonstrate that the measurement of fMRI BOLD responses in amygdala to fearful facial expressions might be usefully employed as an index of amygdala reactivity over extended periods. While signal change to fearful facial expressions appears robust, the experimental design employed here has yielded variable responsivity within baseline or comparison conditions. Future studies might manipulate the experimental design to either amplify or attenuate this variability, according to the goals of the research.
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Laughter facilitates the adaptive response to stress by increasing the psychological distance from distress and by enhancing social relations. To test these hypotheses, the authors related measures of bereaved adults' laughter and smiling 6 months postloss to measures of their (a) subjective emotion and dissociation from distress, (b) social relations, and (c) responses they evoked in others. Duchenne laughter, which involves orbicularis oculi muscle action, related to self-reports of reduced anger and increased enjoyment, the dissociation of distress, better social relations, and positive responses from strangers, whereas non-Duchenne laughter did not. Lending credence to speculations in the ethological literature, Duchenne laughter correlated with different intrapersonal and interpersonal responses than Duchenne smiles. Discussion focuses on the relevance of these findings to theories of positive emotion.
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BACKGROUND: EEG alpha power has been demonstrated to be inversely related to mental activity and has subsequently been used as an indirect measure of brain activation. The hypothesis that the thalamus serves as a neuronal oscillator of alpha rhythms has been supported by studies in animals, but only minimally by studies in humans.
METHODS: In the current study, PET-derived measures of regional glucose metabolism, EEG, and structural MRI were obtained from each participant to assess the relation between thalamic metabolic activity and alpha power in depressed patients and healthy controls. The thalamus was identified and drawn on each subject's MRI. The MRI was then co-registered to the corresponding PET scan and metabolic activity from the thalamus extracted. Thalamic activity was then correlated with a 30-min aggregated average of alpha EEG power.
RESULTS: Robust inverse correlations were observed in the control data, indicating that greater thalamic metabolism is correlated with decreased alpha power. No relation was found in the depressed patient data.
CONCLUSIONS: The results are discussed in the context of a possible abnormality in thalamocortical circuitry associated with depression.
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Planned and reflexive behaviors often occur in the presence of emotional stimuli and within the context of an individual's acute emotional state. Therefore, determining the manner in which emotion and attention interact is an important step toward understanding how we function in the real world. Participants in the current investigation viewed centrally displayed, task-irrelevant, face distractors (angry, neutral, happy) while performing a lateralized go/no-go continuous performance task. Lateralized go targets and no-go lures that did not spatially overlap with the faces were employed to differentially probe processing in the left (LH) and right (RH) cerebral hemispheres. There was a significant interaction between expression and hemisphere, with an overall pattern such that angry distractors were associated with relatively more RH inhibitory errors than neutral or happy distractors and happy distractors with relatively more LH inhibitory errors than angry or neutral distractors. Simple effects analyses confirmed that angry faces differentially interfered with RH relative to LH inhibition and with inhibition in the RH relative to happy faces. A significant three-way interaction further revealed that state anxiety moderated relations between emotional expression and hemisphere. Under conditions of low cognitive load, more intense anxiety was associated with relatively greater RH than LH impairment in the presence of both happy and threatening distractors. By contrast, under high load, only angry distractors produced greater RH than LH interference as a function of anxiety.
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This commentary provides reflections on the current state of affairs in research on EEG frontal asymmetries associated with affect. Although considerable progress has occurred since the first report on this topic 25 years ago, research on frontal EEG asymmetries associated with affect has largely evolved in the absence of any serious connection with neuroscience research on the structure and function of the primate prefrontal cortex (PFC). Such integration is important as this work progresses since the neuroscience literature can help to understand what the prefrontal cortex is "doing" in affective processing. Data from the neuroscience literature on the heterogeneity of different sectors of the PFC are introduced and more specific hypotheses are offered about what different sectors of the PFC might be doing in affect. A number of methodological issues associated with EEG measures of functional prefrontal asymmetries are also considered.
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Dynamic adjustments in cognitive control are well documented in conflict tasks, wherein competition from irrelevant stimulus attributes intensifies selection demands and leads to subsequent performance benefits. The current study investigated whether mnemonic demands, in a working memory (WM) task, can drive similar online control modifications. Demand levels (high vs. low) of WM maintenance (memory load of 2 items vs. 1 item) and delay-spanning distractor interference (confusable vs. not confusable with memoranda) were manipulated using a factorial design during a WM delayed-recognition task. Performance was best subsequent to trials in which both maintenance and distractor interference demands were high, followed by trials with high demand in either of these 2 control domains, and worst following trials with low demand in both domains. These results suggest that dynamic adjustments in cognitive control are not triggered exclusively by conflict-specific contexts but are also triggered by WM demands, revealing a putative mechanism by which this system configures itself for successful task performance.
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