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High vs. low scorers on the Beck Depression Inventory (BDI) were compared on measures of resting EEG activation asymmetry from frontal and parietal brain regions. Depressed subjects showed greater relative right frontal activation compared with nondepressed subjects. Parietal asymmetry did not distinguish between the groups. These data support the hypothesis of right hemisphere hyperactivation in the frontal region of depressed individuals and are consistent with the growing body of literature which suggests that the left and right frontal regions may be differentially specialized for particular positive and negative affects.
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Individuals differ dramatically in the quality and intensity of their response to affectively evocative stimuli. On the basis of prior theory and research, we hypothesized that these individual differences are related to variation in activation of the left and right frontal brain regions. We recorded baseline brain electrical activity from subjects on two occasions 3 weeks apart. Immediately following the second recording, subjects were exposed to brief positive and negative emotional film clips. For subjects whose frontal asymmetry was stable across the 3-week period, greater left frontal activation was associated with reports of more intense positive affect in response to the positive films, whereas greater right frontal activation was associated with more intense reports of negative affect in response to the negative film clips. The methodological and theoretical implications of these data are discussed.
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BACKGROUND: Functional magnetic resonance imaging (fMRI) holds promise as a noninvasive means of identifying neural responses that can be used to predict treatment response before beginning a drug trial. Imaging paradigms employing facial expressions as presented stimuli have been shown to activate the amygdala and anterior cingulate cortex (ACC). Here, we sought to determine whether pretreatment amygdala and rostral ACC (rACC) reactivity to facial expressions could predict treatment outcomes in patients with generalized anxiety disorder (GAD). METHODS: Fifteen subjects (12 female subjects) with GAD participated in an open-label venlafaxine treatment trial. Functional magnetic resonance imaging responses to facial expressions of emotion collected before subjects began treatment were compared with changes in anxiety following 8 weeks of venlafaxine administration. In addition, the magnitude of fMRI responses of subjects with GAD were compared with that of 15 control subjects (12 female subjects) who did not have GAD and did not receive venlafaxine treatment. RESULTS: The magnitude of treatment response was predicted by greater pretreatment reactivity to fearful faces in rACC and lesser reactivity in the amygdala. These individual differences in pretreatment rACC and amygdala reactivity within the GAD group were observed despite the fact that 1) the overall magnitude of pretreatment rACC and amygdala reactivity did not differ between subjects with GAD and control subjects and 2) there was no main effect of treatment on rACC-amygdala reactivity in the GAD group. CONCLUSIONS: These findings show that this pattern of rACC-amygdala responsivity could prove useful as a predictor of venlafaxine treatment response in patients with GAD.
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<p>BACKGROUND: Functional magnetic resonance imaging (fMRI) techniques were used to identify the neural circuitry underlying emotional processing in control and depressed subjects. Depressed subjects were studied before and after treatment with venlafaxine. This new technique provides a method to noninvasively image regional brain function with unprecedented spatial and temporal resolution. METHOD: Echo-planar imaging was used to acquire whole brain images while subjects viewed positively and negatively valenced visual stimuli. Two control subjects and two depressed subjects who met DSM-IV criteria for major depression were scanned at baseline and 2 weeks later. Depressed subjects were treated with venlafaxine after the baseline scan. RESULTS: Preliminary results from this ongoing study revealed three interesting trends in the data. Both depressed patients demonstrated considerable symptomatic improvement at the time of the second scan. Across control and depressed subjects, the negative compared with the positive pictures elicited greater global activation. In both groups, activation induced by the negative pictures decreased from the baseline scan to the 2-week scan. This decrease in activation was also present in the control subjects when they were exposed to the positive pictures. In contrast, when the depressed subjects were presented with the positive pictures they showed no activation at baseline, whereas after 2 weeks of treatment an area of activation emerged in right secondary visual cortex. CONCLUSION: While preliminary, these results demonstrate the power of using fMRI to study emotional processes in normal and depressed subjects and to examine mechanisms of action of antidepressant drugs.</p>
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Developments in technologic and analytical procedures applied to the study of brain electrical activity have intensified interest in this modality as a means of examining brain function. The impact of these new developments on traditional methods of acquiring and analyzing electroencephalographic activity requires evaluation. Ultimately, the integration of the old with the new must result in an accepted standardized methodology to be used in these investigations. In this paper, basic procedures and recent developments involved in the recording and analysis of brain electrical activity are discussed and recommendations are made, with emphasis on psychophysiological applications of these procedures.
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Research on the anatomical bases of interhemispheric interaction, including individual differences in corpus callosum (CC) anatomy, is reviewed. These anatomical findings form the basis for the discussion of two major themes. The first considers interhemispheric transfer time (IHTT) and related issues. These include varieties of IHTT and possible directional asymmetries of IHTT. Evidence suggests that pathological variations in IHTT may have cognitive consequences. The second involves conditions under which interhemispheric interaction is necessary and beneficial. The data suggest that when both hemispheres have some competence at a difficult task, there is a benefit to interhemispheric interaction. The role of the CC in the dynamic distribution of attention may be particularly relevant to this advantage. Throughout the article reference is made to individual differences and developmental changes associated with interhemispheric interaction.
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Neurosurgical treatment of psychiatric disorders has been influenced by evolving neurobiological models of symptom generation. The advent of functional neuroimaging and advances in the neurosciences have revolutionized understanding of the functional neuroanatomy of psychiatric disorders. This article reviews neuroimaging studies of depression from the last 3 decades and describes an emerging neurocircuitry model of mood disorders, focusing on critical circuits of cognition and emotion, particularly those networks involved in the regulation of evaluative, expressive and experiential aspects of emotion. The relevance of this model for neurotherapeutics is discussed, as well as the role of functional neuroimaging of psychiatric disorders.
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This research assessed whether individual differences in anterior brain asymmetry are linked to differences in basic dimensions of emotion. In each of 2 experimental sessions, separated by 3 weeks, resting electroencephalogram (EEG) activity was recorded from female adults during 8 60-s baselines. Mean alpha power asymmetry across both sessions was extracted in mid-frontal and anterior temporal sites. Across both regions, groups demonstrating stable and extreme relative left anterior activation reported increased generalized positive affect (PA) and decreased generalized negative affect (NA) compared with groups demonstrating stable and extreme relative right anterior activation. Additional correlational analyses revealed robust relations between anterior asymmetry and PA and NA, particularly among subjects who demonstrated stable patterns of EEG activation over time. Anterior asymmetry was unrelated to individual differences in generalized reactivity.
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Baseline resting electroencephalogram activity was recorded with 3 different reference montages from 15 clinically depressed and 13 control subjects. Power in all frequency bands was extracted by fast Fourier transformation. There was a significant Group X Hemisphere interaction in the mid-frontal region, for the alpha band power only. Depressed subjects had less left-sided activation (i.e., more alpha activity) than did normal control subjects. This pattern of diminished left-sided frontal activation is interpreted as indicating a deficit in approach mechanisms in depressed subjects.
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The capacity to stabilize the content of attention over time varies among individuals, and its impairment is a hallmark of several mental illnesses. Impairments in sustained attention in patients with attention disorders have been associated with increased trial-to-trial variability in reaction time and event-related potential deficits during attention tasks. At present, it is unclear whether the ability to sustain attention and its underlying brain circuitry are transformable through training. Here, we show, with dichotic listening task performance and electroencephalography, that training attention, as cultivated by meditation, can improve the ability to sustain attention. Three months of intensive meditation training reduced variability in attentional processing of target tones, as indicated by both enhanced theta-band phase consistency of oscillatory neural responses over anterior brain areas and reduced reaction time variability. Furthermore, those individuals who showed the greatest increase in neural response consistency showed the largest decrease in behavioral response variability. Notably, we also observed reduced variability in neural processing, in particular in low-frequency bands, regardless of whether the deviant tone was attended or unattended. Focused attention meditation may thus affect both distracter and target processing, perhaps by enhancing entrainment of neuronal oscillations to sensory input rhythms, a mechanism important for controlling the content of attention. These novel findings highlight the mechanisms underlying focused attention meditation and support the notion that mental training can significantly affect attention and brain function.
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OBJECTIVE: Positron emission tomography was used to investigate the neural substrates of normal human emotional and their dependence on the types of emotional stimulus. METHOD: Twelve healthy female subjects underwent 12 measurements of regional brain activity following the intravenous bolus administration of [15O]H2O as they alternated between emotion-generating and control film and recall tasks. Automated image analysis techniques were used to characterize and compare the increases in regional brain activity associated with the emotional response to complex visual (film) and cognitive (recall) stimuli. RESULTS: Film- and recall-generated emotion were each associated with significantly increased activity in the vicinity of the medial prefrontal cortex and thalamus, suggesting that these regions participate in aspects of emotion that do not depend on the nature of the emotional stimulus. Film-generated emotion was associated with significantly greater increases in activity bilaterally in the occipitotemporparietal cortex, lateral cerebellum, hypothalamus, and a region that includes the anterior temporal cortex, amygdala, and hippocampal formation, suggesting that these regions participate in the emotional response to certain exteroceptive sensory stimuli. Recall-generated sadness was associated with significantly greater increases in activity in the vicinity of the anterior insular cortex, suggesting that this region participates in the emotional response to potentially distressing cognitive or interoceptive sensory stimuli. CONCLUSIONS: While this study should be considered preliminary, it identified brain regions that participate in externally and internally generated human emotion.
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OBJECTIVE: Happiness, sadness, and disgust are three emotions that differ in their valence (positive or negative) and associated action tendencies (approach or withdrawal). This study was designed to investigate the neuroanatomical correlates of these discrete emotions. METHOD: Twelve healthy female subjects were studied. Positron emission tomography and [15O]H2O were used to measure regional brain activity. There were 12 conditions per subject: happiness, sadness, and disgust and three control conditions, each induced by film and recall. Emotion and control tasks were alternated throughout. Condition order was pseudo-randomized and counterbalanced across subjects. Analyses focused on brain activity patterns for each emotion when combining film and recall data. RESULTS: Happiness, sadness, and disgust were each associated with increases in activity in the thalamus and medial prefrontal cortex (Brodmann's area 9). These three emotions were also associated with activation of anterior and posterior temporal structures, primarily when induced by film. Recalled sadness was associated with increased activation in the anterior insula. Happiness was distinguished from sadness by greater activity in the vicinity of ventral mesial frontal cortex. CONCLUSIONS: While this study should be considered preliminary, it identifies regions of the brain that participate in happiness, sadness, and disgust, regions that distinguish between positive and negative emotions, and regions that depend on both the elicitor and valence of emotion or their interaction.
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Positive affect elicited in a mother toward her newborn infant may be one of the most powerful and evolutionarily preserved forms of positive affect in the emotional landscape of human behavior. This study examined the neurobiology of this form of positive emotion and in so doing, sought to overcome the difficulty of eliciting robust positive affect in response to visual stimuli in the physiological laboratory. Six primiparous human mothers with no indications of postpartum depression brought their infants into the laboratory for a photo shoot. Approximately 6 weeks later, they viewed photographs of their infant, another infant, and adult faces during acquisition of functional magnetic resonance images (fMRI). Mothers exhibited bilateral activation of the orbitofrontal cortex (OFC) while viewing pictures of their own versus unfamiliar infants. While in the scanner, mothers rated their mood more positively for pictures of their own infants than for unfamiliar infants, adults, or at baseline. The orbitofrontal activation correlated positively with pleasant mood ratings. In contrast, areas of visual cortex that also discriminated between own and unfamiliar infants were unrelated to mood ratings. These data implicate the orbitofrontal cortex in a mother's affective responses to her infant, a form of positive emotion that has received scant attention in prior human neurobiological studies. Furthermore, individual variations in orbitofrontal activation to infant stimuli may reflect an important dimension of maternal attachment.
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Increasing research indicates that concepts are represented as distributed circuits of property information across the brain's modality-specific areas. The current study examines the distributed representation of an important but under-explored category, foods. Participants viewed pictures of appetizing foods (along with pictures of locations for comparison) during event-related fMRI. Compared to location pictures, food pictures activated the right insula/operculum and the left orbitofrontal cortex, both gustatory processing areas. Food pictures also activated regions of visual cortex that represent object shape. Together these areas contribute to a distributed neural circuit that represents food knowledge. Not only does this circuit become active during the tasting of actual foods, it also becomes active while viewing food pictures. Via the process of pattern completion, food pictures activate gustatory regions of the circuit to produce conceptual inferences about taste. Consistent with theories that ground knowledge in the modalities, these inferences arise as reenactments of modality-specific processing.
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Individuals with fragile X syndrome (FXS) commonly display characteristics of social anxiety, including gaze aversion, increased time to initiate social interaction, and difficulty forming meaningful peer relationships. While neural correlates of face processing, an important component of social interaction, are altered in FXS, studies have not examined whether social anxiety in this population is related to higher cognitive processes, such as memory. This study aimed to determine whether the neural circuitry involved in face encoding was disrupted in individuals with FXS, and whether brain activity during face encoding was related to levels of social anxiety. A group of 11 individuals with FXS (5 M) and 11 age- and gender-matched control participants underwent fMRI scanning while performing a face encoding task with online eye-tracking. Results indicate that compared to the control group, individuals with FXS exhibited decreased activation of prefrontal regions associated with complex social cognition, including the medial and superior frontal cortex, during successful face encoding. Further, the FXS and control groups showed significantly different relationships between measures of social anxiety (including gaze-fixation) and brain activity during face encoding. These data indicate that social anxiety in FXS may be related to the inability to successfully recruit higher level social cognition regions during the initial phases of memory formation.
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This experiment was designed to assess the differential impact of initially presenting affective information to the left versus right hemisphere on both the perception of and response to the input. Nineteen right-handed subjects were presented with faces expressing happiness and sadness. Each face was presented twice to each visual field for an 8-sec duration. The electro-oculogram (EOG) was monitored and fed back to subjects to train them to keep their eyes focused on the central fixation point as well as to eliminate trials confounded by eye movement artifact. Following each slide presentation, subjects rated the intensity of the emotional expression depicted in the face and their emotional reaction to the face on a series of 7-point rating scales. Subjects reported perceiving more happiness in response to stimuli initially presented to the left hemisphere (right visual field) compared to presentations of the identical faces to the right hemisphere (left visual field). This effect was predominantly a function of ratings on sad faces. A similar, albeit less robust, effect was found on self-ratings of happiness (the degree to which the face elicited the emotion in the viewer). These data challenge the view that the right hemisphere is uniquely involved in all emotional behavior. The implications of these findings for theories concerning the lateralization of emotional behavior are discussed.
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