A systematic review of the neurophysiology of mindfulness on EEG oscillations.

Mindfulness meditation has been purported to be a beneficial practice for wellbeing. It would therefore be expected that the neurophysiology of mindfulness would reflect this impact on wellbeing. However, investigations of the effects of mindfulness have generated mixed reports of increases, decreases, as well as no differences in EEG oscillations in comparison with a resting state and a variety of tasks. We have performed a systematic review of EEG studies of mindfulness meditation in order to determine any common effects and to identify factors which may impact on the effects. Databases were reviewed from 1966 to August 2015. Eligibility criteria included empirical quantitative analyses of mindfulness meditation practice and EEG measurements acquired in relation to practice. A total of 56 papers met the eligibility criteria and were included in the systematic review, consisting of a total 1715 subjects: 1358 healthy individuals and 357 individuals with psychiatric diagnoses. Studies were principally examined for power outcomes in each bandwidth, in particular the power differentials between mindfulness and a control state, as well as outcomes relating to hemispheric asymmetry and event-related potentials. The systematic review revealed that mindfulness was most commonly associated with enhanced alpha and theta power as compared to an eyes closed resting state, although such outcomes were not uniformly reported. No consistent patterns were observed with respect to beta, delta and gamma bandwidths. In summary, mindfulness is associated with increased alpha and theta power in both healthy individuals and in patient groups. This co-presence of elevated alpha and theta may signify a state of relaxed alertness which is conducive to mental health.

Functional MRI of verbal self-monitoring in schizophrenia: performance and illness-specific effects.

Previous small-sample studies have shown altered frontotemporal activity in schizophrenia patients with auditory hallucinations and impaired monitoring of self-generated speech. We examined a large cohort of patients with schizophrenia (n = 63) and a representative group of healthy controls (n = 20) to disentangle performance, illness, and symptom-related effects in functional magnetic resonance imaging-detected brain abnormalities during monitoring of self- and externally generated speech in schizophrenia. Our results revealed activation of the thalamus (medial geniculate nucleus, MGN) and frontotemporal regions with accurate monitoring across all participants. Less activation of the thalamus (MGN, pulvinar) and superior-middle temporal and inferior frontal gyri occurred in poorly performing patients (1 standard deviation below controls' mean; n = 36), relative to the combined group of controls and well-performing patients. In patients, (1) greater deactivation of the ventral striatum and hypothalamus to own voice, combined with nonsignificant activation of the same regions to others' voice, associated positively with negative symptoms (blunted affect, emotional withdrawal, poor rapport, passive social avoidance) regardless of performance and (2) exaggerated activation of the right superior-middle temporal gyrus during undistorted, relative to distorted, feedback associated with both positive symptoms (hallucinations, persecution) and poor performance. A further thalamic abnormality characterized schizophrenia patients regardless of performance and symptoms. We conclude that hypoactivation of a neural network comprised of the thalamus and frontotemporal regions underlies impaired speech monitoring in schizophrenia. Positive symptoms and poor monitoring share a common activation abnormality in the right superior temporal gyrus during processing of degraded speech. Altered striatal and hypothalamic modulation to own and others' voice characterizes emotionally withdrawn and socially avoidant patients.

A longitudinal functional magnetic resonance imaging study of verbal working memory in depression after antidepressant therapy.

BACKGROUND: Impairments in the neural circuitry of verbal working memory are evident in depression. Factors of task demand and depressive state might have significant effects on its functional neuroanatomy. METHODS: Two groups underwent functional magnetic resonance imaging while performing a verbal working memory task of varying cognitive load (n-back). The patient group comprised 20 medication-free individuals in an acute episode of unipolar major depression and the control group comprised 20 healthy individuals. Scans were acquired at weeks 0 (baseline), 2, and 8. Patients received treatment with fluoxetine after the baseline scan. Cerebral activations were measured for mean overall activation as well as the linear and quadratic load-response activity with increasing task demand (1-, 2-, 3-back). RESULTS: There were no significant differences in performance accuracy between groups. However, a main effect of group was observed in the load-response activity in frontal and posterior cortical regions within the verbal working memory network in which patients showed a greater load-response relative to control subjects. Group by time effects were revealed in the load-response activity in the caudate and thalamus. As a marker of treatment response, a lower linear load-response at baseline in the dorsal anterior cingulate, left middle frontal, and lateral temporal cortices was associated with an improved clinical outcome. CONCLUSIONS: Maintenance of performance accuracy in patients was accompanied by a significant increase in the load-response activity in frontal and posterior cortical regions within the verbal working memory network. These data also provide further support for resilience of activity in the anterior cingulate as a predictor of treatment response in depression.

A functional MRI study of happy and sad affective states induced by classical music.

The present study investigated the functional neuroanatomy of transient mood changes in response to Western classical music. In a pilot experiment, 53 healthy volunteers (mean age: 32.0; SD = 9.6) evaluated their emotional responses to 60 classical musical pieces using a visual analogue scale (VAS) ranging from 0 (sad) through 50 (neutral) to 100 (happy). Twenty pieces were found to accurately induce the intended emotional states with good reliability, consisting of 5 happy, 5 sad, and 10 emotionally unevocative, neutral musical pieces. In a subsequent functional magnetic resonance imaging (fMRI) study, the blood oxygenation level dependent (BOLD) signal contrast was measured in response to the mood state induced by each musical stimulus in a separate group of 16 healthy participants (mean age: 29.5; SD = 5.5). Mood state ratings during scanning were made by a VAS, which confirmed the emotional valence of the selected stimuli. Increased BOLD signal contrast during presentation of happy music was found in the ventral and dorsal striatum, anterior cingulate, parahippocampal gyrus, and auditory association areas. With sad music, increased BOLD signal responses were noted in the hippocampus/amygdala and auditory association areas. Presentation of neutral music was associated with increased BOLD signal responses in the insula and auditory association areas. Our findings suggest that an emotion processing network in response to music integrates the ventral and dorsal striatum, areas involved in reward experience and movement; the anterior cingulate, which is important for targeting attention; and medial temporal areas, traditionally found in the appraisal and processing of emotions.

Neural correlates of the misattribution of self-generated speech.

Auditory hallucinations are thought to arise through the misidentification of self-generated verbal material as alien. The neural mechanisms that normally mediate the differentiation of self-generated from nonself speech are unclear. We investigated this in healthy volunteers using functional MRI. Eleven healthy volunteers were scanned whilst listening to a series of prerecorded words. The source (self/nonself) and acoustic quality (undistorted/distorted) of the speech was varied across trials. Participants indicated whether the words were spoken in their own or another person's voice via a button press. Listening to self-generated words was associated with more activation in the left inferior frontal and right anterior cingulate cortex than words in another person's voice, which was associated with greater engagement of the lateral temporal cortex bilaterally. Listening to distorted speech was associated with activation in the inferior frontal and anterior cingulate cortex. There was an interaction between the effects of source of speech and distortion on activation in the left temporal cortex. In the presence of distortion participants were more likely to misidentify their voice as that of another. This misattribution of self-generated speech was associated with reduced engagement of the cingulate and prefrontal cortices. The evaluation of auditory speech involves a network including the inferior frontal, anterior cingulate, and lateral temporal cortex. The degree to which different areas within this network are engaged varies with the source and acoustic quality of the speech. Accurate identification of one's own speech appears to depend on cingulate and prefrontal activity.