EEG and EEG source-estimation are susceptible to electromyographic artifacts (EMG) generated by the cranial muscles. EMG can mask genuine effects or masquerade as a legitimate effect-even in low frequencies, such as alpha (8-13 Hz). Although regression-based correction has been used previously, only cursory attempts at validation exist, and the utility for source-localized data is unknown. To address this, EEG was recorded from 17 participants while neurogenic and myogenic activity were factorially varied. We assessed the sensitivity and specificity of four regression-based techniques: between-subjects, between-subjects using difference-scores, within-subjects condition-wise, and within-subject epoch-wise on the scalp and in data modeled using the LORETA algorithm. Although within-subject epoch-wise showed superior performance on the scalp, no technique succeeded in the source-space. Aside from validating the novel epoch-wise methods on the scalp, we highlight methods requiring further development.
<p>The human voice is one of the principal conveyers of social and affective communication. Yet relatively little is known about the neural circuitry that supports the recognition of different vocally expressed emotions. We conducted an FMRI study to examine the brain responses to vocal expressions of anger and happiness, and to test whether specific brain regions showed preferential engagement in the processing of one emotion over the other. We also tested the extent to which simultaneously presented facial expressions of the same or different emotions would enhance brain responses, and to what degree such responses depend on attention towards the vocal expression. Forty healthy individuals were scanned while listening to vocal expressions of anger or happiness, while at the same time watching congruent or discrepant facial expressions. Happy voices elicited significantly more activation than angry voices in right anterior and posterior middle temporal gyrus (MTG), left posterior MTG and right inferior frontal gyrus. Furthermore, for the left MTG region, happy voices were related to higher activation only when paired with happy faces. Activation in the left insula, left amygdala and hippocampus, and rostral anterior cingulate cortex showed an effect of selectively attending to the vocal stimuli. Our results identify a network of regions implicated in the processing of vocal emotion, and suggest a particularly salient role for vocal expressions of happiness.</p>
Facial expressions of pain are an important part of the pain response, signaling distress to others and eliciting social support. To evaluate how voluntary modulation of this response contributes to the pain experience, 29 subjects were exposed to thermal stimulation while making standardized pain, control, or relaxed faces. Dependent measures were self-reported negative effect (valence and arousal) as well as the intensity of nociceptive stimulation required to reach a given subjective level of pain. No direct social feedback was given by the experimenter. Although the amount of nociceptive stimulation did not differ across face conditions, subjects reported more negative effects in response to painful stimulation while holding the pain face. Subsequent analyses suggested the effects were not due to preexisting differences in the difficulty or unpleasantness of making the pain face. These results suggest that voluntary pain expressions have no positively reinforcing (pain attenuating) qualities, at least in the absence of external contingencies such as social reinforcement, and that such expressions may indeed be associated with higher levels of negative affect in response to similar nociceptive input. PERSPECTIVE: This study demonstrates that making a standardized pain face increases negative affect in response to nociceptive stimulation, even in the absence of social feedback. This suggests that exaggerated facial displays of pain, although often socially reinforced, may also have unintended aversive consequences.
We used measures of regional brain electrical activity to show that not all smiles are the same. Only one form of smiling produced the physiological pattern associated with enjoyment. Our finding helps to explain why investigators who treated all smiles as the same found smiles to be ubiquitous, occurring when people are unhappy as well as happy. Also, our finding that voluntarily making two different kinds of smiles generated the same two patterns of regional brain activity as was found when these smiles occur involuntarily suggests that it is possible to generate deliberately some of the physiological change which occurs during spontaneous positive affect.
We present a novel weighted Fourier series (WFS) representation for cortical surfaces. The WFS representation is a data smoothing technique that provides the explicit smooth functional estimation of unknown cortical boundary as a linear combination of basis functions. The basic properties of the representation are investigated in connection with a self-adjoint partial differential equation and the traditional spherical harmonic (SPHARM) representation. To reduce steep computational requirements, a new iterative residual fitting (IRF) algorithm is developed. Its computational and numerical implementation issues are discussed in detail. The computer codes are also available at http://www.stat.wisc.edu/-mchung/softwares/weighted.SPHARM/weighted-SPHARM.html. As an illustration, the WFS is applied i n quantifying the amount ofgray matter in a group of high functioning autistic subjects. Within the WFS framework, cortical thickness and gray matter density are computed and compared.
One of the most salient features of emotion is the pronounced variability among individuals in their reactions to emotional incentives and in their dispositional mood. Collectively, these individual differences have been described as affective style. Recent research has begun to dissect the constituents of affective style. The search for these components is guided by the neural systems that instantiate emotion and emotion regulation. In this article, this body of research and theory is applied specifically to positive affect and well-being. The central substrates and peripheral biological correlates of well-being are described. A resilient affective style is associated with high levels of left prefrontal activation, effective modulation of activation in the amygdala and fast recovery in response to negative and stressful events. In peripheral biology, these central patterns are associated with lower levels of basal cortisol and with higher levels of antibody titres to influenza vaccine. The article concludes with a consideration of whether these patterns of central and peripheral biology can be modified by training and shifted toward a more salubrious direction.
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.