We investigated whether mindfulness training (MT) influences information processing in a working memory task with complex visual stimuli. Participants were tested before (T1) and after (T2) participation in an intensive one-month MT retreat, and their performance was compared with that of an age- and education-matched control group. Accuracy did not differ across groups at either time point. Response times were faster and significantly less variable in the MT versus the control group at T2. Since these results could be due to changes in mnemonic processes, speed-accuracy trade-off, or nondecisional factors (e.g., motor execution), we used a mathematical modeling approach to disentangle these factors. The EZ-diffusion model (Wagenmakers, van der Maas, & Grasman, Psychonomic Bulletin & Review 14:(1), 3-22, 2007) suggested that MT leads to improved information quality and reduced response conservativeness, with no changes in nondecisional factors. The noisy exemplar model further suggested that the increase in information quality reflected a decrease in encoding noise and not an increase in forgetting. Thus, mathematical modeling may help clarify the mechanisms by which MT produces salutary effects on performance.
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INTRODUCTION: Major depressive disorder (MDD) is characterized by cognitive biases in attention, memory and language use. Language use biases often parallel depression symptoms, and contain over-representations of both negative emotive and death words as well as low levels of positive emotive words. This study further explores cognitive biases in depression by comparing the effect of current depression status to cumulative depression history on an elaborated verbal recall of emotional photographs.
METHODS: Following a negative mood induction, fifty-two individuals (42 women) with partially-remitted depression viewed - then recalled and verbally described - slides from the International Affective Picture System (IAPS). Descriptions were transcribed and frequency of depression-related word use (positive emotion, negative emotion, sex, ingestion and death) was analyzed using the Linguistic Inquiry and Word Count program (LIWC).
RESULTS: Contrary to expectations and previous findings, current depression status did not affect word use in any categories of interest. However, individuals with more than 5 years of previous depression used fewer words related to positive emotion (t(50) = 2.10, p = .04, (d = 0.57)), and sex (t(48) = 2.50, p = .013 (d = 0.81)), and there was also a trend for these individuals to use fewer ingestion words (t(50) = 1.95, p = .057 (d = 0.58)), suggesting a deficit in appetitive processing.
CONCLUSIONS: Our findings suggest that depression duration affects appetitive information processing and that appetitive word use may be a behavioral marker for duration related brain changes which may be used to inform treatment.
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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
There is a growing scientific interest in mindfulness meditation (MM), yet its underlying neurophysiological mechanism is still uncertain. We investigated whether MM affects self-referential processing, associated with default mode network (DMN), either as short (state) – or long-term (trait) effects.
Methods
Three levels of MM expertise were compared with controls (n = 12 each) by electroencephalography (EEG).
Results
DMN deactivation was identified during the transition from resting state to a time production task, as lower gamma (25–45 Hz) power over frontal and midline regions. MM practitioners exhibited a trait lower frontal gamma activity, related to narrative self-reference and DMN activity, as well as producing longer durations, these being negatively correlated with frontal gamma activity. Additionally, we found state increases in posterior gamma power, suggesting increased attention and sensory awareness. MM proficiency did not affect the results.
Conclusions
Gamma power over frontal midline areas reflects DMN activity. MM practitioners exhibit lower trait frontal gamma activity, as well as a state and trait increases in posterior gamma power, irrespective of practice proficiency.
Significance
First, the DMN can be studied non-invasively by EEG. Second, MM induces from the early stages of practice neuroplasticity in self-referential and attentional networks.
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Mindfulness is defined as paying attention in the present moment. We investigate the hypothesis that mindfulness training may alter or enhance specific aspects of attention. We examined three functionally and neuroanatomically distinct but overlapping attentional subsystems: alerting, orienting, and conflict monitoring. Functioning of each subsystem was indexed by performance on the Attention Network Test. Two types of mindfulness training (MT) programs were examined, and behavioral testing was conducted on participants before (Time 1) and after (Time 2) training. One training group consisted of individuals naive to mindfulness techniques who participated in an 8-week mindfulness-based stress reduction (MBSR) course that emphasized the development of concentrative meditation skills. The other training group consisted of individuals experienced in concentrative meditation techniques who participated in a 1-month intensive mindfulness retreat. Performance of these groups was compared with that of control participants who were meditation naive and received no MT. At Time 1, the participants in the retreat group demonstrated improved conflict monitoring performance relative to those in the MBSR and control groups. At Time 2, the participants in the MBSR course demonstrated significantly improved orienting in comparison with the control and retreat participants. In contrast, the participants in the retreat group demonstrated altered performance on the alerting component, with improvements in exogenous stimulus detection in comparison with the control and MBSR participants. The groups did not differ in conflict monitoring performance at Time 2. These results suggest that mindfulness training may improve attention-related behavioral responses by enhancing functioning of specific subcomponents of attention. Whereas participation in the MBSR course improved the ability to endogenously orient attention, retreat participation appeared to allow for the development and emergence of receptive attentional skills, which improved exogenous alerting-related process.
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Meditation refers to a family of mental training practices that are designed to familiarize the practitioner with specific types of mental processes. One of the most basic forms of meditation is concentration meditation, in which sustained attention is focused on an object such as a small visual stimulus or the breath. In age-matched participants, using functional MRI, we found that activation in a network of brain regions typically involved in sustained attention showed an inverted u-shaped curve in which expert meditators (EMs) with an average of 19,000 h of practice had more activation than novices, but EMs with an average of 44,000 h had less activation. In response to distracter sounds used to probe the meditation, EMs vs. novices had less brain activation in regions related to discursive thoughts and emotions and more activation in regions related to response inhibition and attention. Correlation with hours of practice suggests possible plasticity in these mechanisms.
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Children with an anxious temperament (AT) are at risk for developing psychiatric disorders along the internalizing spectrum, including anxiety and depression. Like these disorders, AT is a multidimensional phenotype and children with extreme anxiety show varying mixtures of physiological, behavioral, and other symptoms. Using a well-validated juvenile monkey model of AT, we addressed the degree to which this phenotypic heterogeneity reflects fundamental differences or similarities in the underlying neurobiology. The rhesus macaque is optimal for studying AT because children and young monkeys express the anxious phenotype in similar ways and have similar neurobiology. Fluorodeoxyglucose (FDG)-positron emission tomography (FDG-PET) in 238 freely behaving monkeys identified brain regions where metabolism predicted variation in three dimensions of the AT phenotype: hypothalamic-pituitary-adrenal (HPA) activity, freezing behavior, and expressive vocalizations. We distinguished brain regions that predicted all three dimensions of the phenotype from those that selectively predicted a single dimension. Elevated activity in the central nucleus of the amygdala and the anterior hippocampus was consistently found across individuals with different presentations of AT. In contrast, elevated activity in the lateral anterior hippocampus was selective to individuals with high levels of HPA activity, and decreased activity in the motor cortex (M1) was selective to those with high levels of freezing behavior. Furthermore, activity in these phenotype-selective regions mediated relations between amygdala metabolism and different expressions of anxiety. These findings provide a framework for understanding the mechanisms that lead to heterogeneity in the clinical presentation of internalizing disorders and set the stage for developing improved interventions.
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There is mounting evidence that prefrontal cortex (PFC) is activated during mnemonic operations such as working memory maintenance and also during response-related operations. In the current study, we examine the neural organization of mnemonic and response operations with respect to each other within PFC. Stimulus-evoked and sustained functional MRI activity was recorded during performance of a mental calculation task. The presence or absence of mnemonic and response demands was manipulated in a 2 x 2 factorial design with conditions requiring: (1) memory encoding and maintenance (M+); (2) response selection and execution (R+); (3) encoding, maintenance, and response execution (M+R+); (4) neither mnemonic nor response-related processes (M-R-). The first step of the analyses identified PFC voxels exhibiting differential activity during (M+) vs. (R+) trials. Within these voxels, we then examined activity during multiple phases of (M+R+) trials. Greater stimulus-evoked and sustained activity was observed within the anterior extent of dorsolateral prefrontal cortex (BA 46) during R+ vs. M+ trials. In contrast, greater activity was observed in the posterior extent of dorsolateral PFC during M+ vs. R+ trials. Importantly, both regions were activated during (M+R+) trials. Activity levels during all of these conditions exceeded levels observed during (M-R-) control trials. These results suggest that integrative functions of PFC that allow past information to guide future actions may emerge from communication between discrete subregions supporting mnemonic and response operations.
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The experience of pain arises from both physiological and psychological factors, including one's beliefs and expectations. Thus, placebo treatments that have no intrinsic pharmacological effects may produce analgesia by altering expectations. However, controversy exists regarding whether placebos alter sensory pain transmission, pain affect, or simply produce compliance with the suggestions of investigators. In two functional magnetic resonance imaging (fMRI) experiments, we found that placebo analgesia was related to decreased brain activity in pain-sensitive brain regions, including the thalamus, insula, and anterior cingulate cortex, and was associated with increased activity during anticipation of pain in the prefrontal cortex, providing evidence that placebos alter the experience of pain.
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<p>This experiment was designed to test whether reading disabled boys differ from matched controls on behavioral measures of interhemispheric transfer time (IHTT). Specifically, we proposed that language-disordered reading disabled children who had deficits in naming would show either faster or slower IHTTs compared with controls. From an initial group of 118 right-handed males, we selected a group of 25 disabled and 25 normal readers, matched on age. All subjects had to obtain a full scale IQ of 90 or above, a PIQ score of 85 or above, and a scaled score of 7 or above on the Block Design Subtest of the WISC-R. After meeting additional criteria for group assignment, manual reaction time (RT) measures of IHTT were obtained in response to simple visual and tactile stimuli during two laboratory testing sessions. Half the trials were conducted with the hands in an uncrossed orientation and half with the hands crossed in order to examine the effects of spatial compatibility on estimates of IHTT. The results revealed no overall group differences in IHTT for any of the conditions. However, correlations between IHTT measures and indices of cognitive performance indicated that faster IHTTs were significantly correlated with poorer performance on measures of reading and language function in the dyslexic group. These data are discussed within the context of a model of interhemispheric transfer deficits in disabled readers.</p>
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Working memory (WM) comprises operations whose coordinated action contributes to our ability to maintain focus on goal-relevant information in the presence of distraction. The present study investigated the nature of distraction upon the neural correlates of WM maintenance operations by presenting task-irrelevant distracters during the interval between the memoranda and probes of a delayed-response WM task. The study used a region of interest (ROIs) approach to investigate the role of anterior (e.g., lateral and medial prefrontal cortex--PFC) and posterior (e.g., parietal and fusiform cortices) brain regions that have been previously associated with WM operations. Behavioral results showed that distracters that were confusable with the memorandum impaired WM performance, compared to either the presence of non-confusable distracters or to the absence of distracters. These different levels of distraction led to differences in the regional patterns of delay interval activity measured with event-related functional magnetic resonance imaging (fMRI). In the anterior ROIs, dorsolateral PFC activation was associated with WM encoding and maintenance, and in maintaining a preparatory state, and ventrolateral PFC activation was associated with the inhibition of distraction. In the posterior ROIs, activation of the posterior parietal and fusiform cortices was associated with WM and perceptual processing, respectively. These findings provide novel evidence concerning the neural systems mediating the cognitive and behavioral responses during distraction, and places frontal cortex at the top of the hierarchy of the neural systems responsible for cognitive control.
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Theories of knowledge such as feature lists, semantic networks, and localist neural nets typically use a single global symbol to represent a property that occurs in multiple concepts. Thus, a global symbol represents mane across HORSE, PONY, and LION. Alternatively, perceptual theories of knowledge, as well as distributed representational systems, assume that properties take different local forms in different concepts. Thus, different local forms of mane exist for HORSE, PONY, and LION, each capturing the specific form that mane takes in its respective concept. Three experiments used the property verification task to assess whether properties are represented globally or locally (e.g., Does a PONY have mane?). If a single global form represents a property, then verifying it in any concept should increase its accessibility and speed its verification later in any other concept. Verifying mane for PONY should benefit as much from having verified mane for LION earlier as from verifying mane for HORSE. If properties are represented locally, however, verifying a property should only benefit from verifying a similar form earlier. Verifying mane for PONY should only benefit from verifying mane for HORSE, not from verifying mane for LION. Findings from three experiments strongly supported local property representation and ruled out the interpretation that object similarity was responsible (e.g., the greater overall similarity between HORSE and PONY than between LION and PONY). The findings further suggest that property representation and verification are complicated phenomena, grounded in sensory-motor simulations.
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Several different models postulate that depression is associated with decreased approach-related behavior. Relatively little has been done to date to specifically investigate this issue. In the present study, a signal-detection analysis was used to examine the response biases of dysphoric and nondysphoric female undergraduates during 3 payoff conditions: neutral, reward, and punishment. As predicted, the dysphoric subjects had a smaller change in bias from the neutral to the reward condition compared with the nondysphoric group. The 2 groups did not differ during the neutral and punishment conditions. These findings are consistent with the hypothesis that the left frontal hypoactivation observed in depression reflects a deficit in approach-related behavior.
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<p>Subregional analyses of the hippocampus have suggested a selective role for the CA1 subregion in intermediate/long-term spatial memory and consolidation, but not short-term acquisition or encoding processes. It remains unclear how the direct cortical projection to CA1 via the perforant path (pp) contributes to these CA1-dependent processes. It has been suggested that dopamine selectively modulates the pp projection to CA1 while having little to no effect on the Schaffer collateral (SC) projection to CA1. This series of behavioral and electrophysiological experiments takes advantage of this pharmacological dissociation to demonstrate that the direct pp inputs to CA1 are critical in CA1-dependent intermediate-term retention and retrieval function. Here we demonstrate that local infusion of the nonselective dopamine agonist, apomorphine (10, 15 microg), into the CA1 subregion of awake animals produces impairments in between-day retention and retrieval, sparing within-day encoding of a modified Hebb-Williams maze and contextual conditioning of fear. In contrast, apomorphine produces no deficits when infused into the CA3 subregion. To complement the behavioral analyses, electrophysiological data was collected. In anesthetized animals, local infusion of the same doses of apomorphine significantly modifies evoked responses in the distal dendrites of CA1 following angular bundle stimulation, but produces no significant effects in the more proximal dendritic layer following stimulation of the SC. These results support a modulatory role for dopamine in the EC-CA1, but not CA3-CA1 circuitry, and suggest the possibility of a more fundamental role for EC-CA1 synaptic transmission in terms of intermediate-term, but not short-term spatial memory.</p>
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We investigate the hypothesis that those subregions of the prefrontal cortex (PFC) found to support proactive interference resolution may also support delay-spanning distractor interference resolution. Ten subjects performed delayed-recognition tasks requiring working memory for faces or shoes during functional MRI scanning. During the 15-sec delay interval, task-irrelevant distractors were presented. These distractors were either all faces or all shoes and were thus either congruent or incongruent with the domain of items in the working memory task. Delayed-recognition performance was slower and less accurate during congruent than during incongruent trials. Our fMRI analyses revealed significant delay interval activity for face and shoe working memory tasks within both dorsal and ventral PFC. However, only ventral PFC activity was modulated by distractor category, with greater activity for congruent than for incongruent trials. Importantly, this congruency effect was only present for correct trials. In addition to PFC, activity within the fusiform face area was investigated. During face distraction, activity was greater for face relative to shoe working memory. As in ventrolateral PFC, this congruency effect was only present for correct trials. These results suggest that the ventrolateral PFC and fusiform face area may work together to support delay-spanning interference resolution.
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BACKGROUND: Excessive behavioral inhibition during childhood marks anxious temperament and is a risk factor for the development of anxiety and affective disorders. Studies in nonhuman primates can provide important information related to the expression of this risk factor, since threat-induced freezing in rhesus monkeys is a trait-like characteristic analogous to human behavioral inhibition. The orbitofrontal cortex (OFC) and amygdala are part of a circuit involved in the processing of emotions and associated physiological responses. Earlier work demonstrated involvement of the primate central nucleus of the amygdala (CeA) in mediating anxious temperament. This study assessed the role of the primate OFC in mediating anxious temperament and its involvement in fear responses.
METHODS: Twelve adolescent rhesus monkeys were studied (six lesion and six control monkeys). Lesions were targeted at regions of the OFC that are most interconnected with the amygdala. Behavior and physiological parameters were assessed before and after the lesions.
RESULTS: The OFC lesions significantly decreased threat-induced freezing and marginally decreased fearful responses to a snake. The lesions also resulted in a leftward shift in frontal brain electrical activity consistent with a reduction in anxiety. The lesions did not significantly decrease hypothalamic-pituitary-adrenal (HPA) activity or cerebrospinal fluid (CSF) concentrations of corticotrophin-releasing factor (CRF).
CONCLUSIONS: These findings demonstrate a role for the OFC in mediating anxious temperament and fear-related responses in adolescent primates. Because of the similarities between rhesus monkey threat-induced freezing and childhood behavioral inhibition, these findings are relevant to understanding mechanisms underlying anxious temperament in humans.
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Selective attention has been shown to bias sensory processing in favor of relevant stimuli and against irrelevant or distracting stimuli in perceptual tasks. Increasing evidence suggests that selective attention plays an important role during working memory maintenance, possibly by biasing sensory processing in favor of to-be-remembered items. In the current study, we investigated whether selective attention may also support working memory by biasing processing against irrelevant and potentially distracting information. Event-related potentials (ERPs) were recorded while subjects (n = 22) performed a delayed-recognition task for faces and shoes. The delay period was filled with face or shoe distractors. Behavioral performance was impaired when distractors were congruent with the working memory domain (e.g., face distractor during working memory for faces) relative to when distractors were incongruent with the working memory domain (e.g., face distractor during shoe working memory). If attentional biasing against distractor processing is indeed functionally relevant in supporting working memory maintenance, perceptual processing of distractors is predicted to be attenuated when distractors are more behaviorally intrusive relative to when they are nonintrusive. As such, we predicted that perceptual processing of distracting faces, as measured by the face-sensitive N170 ERP component, would be reduced in the context of congruent (face) working memory relative to incongruent (shoe) working memory. The N170 elicited by distracting faces demonstrated reduced amplitude during congruent versus incongruent working memory. These results suggest that perceptual processing of distracting faces may be attenuated due to attentional biasing against sensory processing of distractors that are most behaviorally intrusive during working memory maintenance.
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Test-retest reliability of resting regional cerebral metabolic rate of glucose (rCMR) was examined in selected subcortical structures: the amygdala, hippocampus, thalamus, and anterior caudate nucleus. Findings from previous studies examining reliability of rCMR suggest that rCMR in small subcortical structures may be more variable than in larger cortical regions. We chose to study these subcortical regions because of their particular interest to our laboratory in its investigations of the neurocircuitry of emotion and depression. Twelve normal subjects (seven female, mean age = 32.42 years, range 21-48 years) underwent two FDG-PET scans separated by approximately 6 months (mean = 25 weeks, range 17-35 weeks). A region-of-interest approach with PET-MRI coregistration was used for analysis of rCMR reliability. Good test-retest reliability was found in the left amygdala, right and left hippocampus, right and left thalamus, and right and left anterior caudate nucleus. However, rCMR in the right amygdala did not show good test-retest reliability. The implications of these data and their import for studies that include a repeat-test design are considered.
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This article completes the analysis of parental narratives of tantrums had by 335 children aged 18 to 60 months. Modal tantrum durations were 0.5 to 1 minute; 75% of the tantrums lasted 5 minutes or less. If the child stamped or dropped to the floor in the first 30 seconds, the tantrum was likely to be shorter and the likelihood of parental intervention less. A novel analysis of behavior probabilities that permitted grouping of tantrums of different durations converged with our previous statistically independent results to yield a model of tantrums as the expression of two independent but partially overlapping emotional and behavioral processes: Anger and Distress. Anger rises quickly, has its peak at or near the beginning of the tantrum, and declines thereafter. Crying and comfort-seeking, components of Distress, slowly increase in probability across the tantrum. This model indicates that tantrums can provide a window on the intense emotional processes of childhood.
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We investigated the top-down influence of working memory (WM) maintenance on feedforward perceptual processing within occipito-temporal face processing structures. During event-related potential (ERP) recordings, subjects performed a delayed-recognition task requiring WM maintenance of faces or houses. The face-sensitive N170 component elicited by delay-spanning task-irrelevant grayscale noise probes was examined. If early feedforward perceptual activity is biased by maintenance requirements, the N170 ERP component elicited by probes should have a greater N170 amplitude response during face relative to house WM trials. Consistent with this prediction, N170 elicited by probes presented at the beginning, middle, and end of the delay interval was greater in amplitude during face relative to house WM. Thus, these results suggest that WM maintenance demands may modulate early feedforward perceptual processing for the entirety of the delay duration. We argue based on these results that temporally early biasing of domain-specific perceptual processing may be a critical mechanism by which WM maintenance is achieved.
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