Disentangling the neural mechanisms involved in Hinduism- and Buddhism-related meditations

The most diffuse forms of meditation derive from Hinduism and Buddhism spiritual traditions. Different cognitive processes are set in place to reach these meditation states. According to an historical-philological hypothesis (Wynne, 2009) the two forms of meditation could be disentangled. While mindfulness is the focus of Buddhist meditation reached by focusing sustained attention on the body, on breathing and on the content of the thoughts, reaching an ineffable state of nothigness accompanied by a loss of sense of self and duality (Samadhi) is the main focus of Hinduism-inspired meditation. It is possible that these different practices activate separate brain networks. We tested this hypothesis by conducting an activation likelihood estimation (ALE) meta-analysis of functional magnetic resonance imaging (fMRI) studies. The network related to Buddhism-inspired meditation (16 experiments, 263 subjects, and 96 activation foci) included activations in some frontal lobe structures associated with executive attention, possibly confirming the fundamental role of mindfulness shared by many Buddhist meditations. By contrast, the network related to Hinduism-inspired meditation (8 experiments, 54 activation foci and 66 subjects) triggered a left lateralized network of areas including the postcentral gyrus, the superior parietal lobe, the hippocampus and the right middle cingulate cortex. The dissociation between anterior and posterior networks support the notion that different meditation styles and traditions are characterized by different patterns of neural activation.     

A self-referential default brain state: patterns of coherence,power, and eLORETA sources during eyes-closed rest and Transcendental Meditation practice

Activation of a default mode network (DMN) including frontal and parietal midline structures varies with cognitive load, being more active during low-load tasks and less active during high-load tasks requiring executive control. Meditation practices entail various degrees of cognitive control. Thus, DMN activation patterns could give insight into the nature of meditation practices. This 10-week random assignment study compared theta2, alpha1, alpha2, beta1, beta2 and gamma EEG coherence, power, and eLORETA cortical sources during eyes-closed rest and Transcendental Meditation (TM) practice in 38 male and female college students, average age 23.7 years. Significant brainwave differences were seen between groups. Compared to eyes-closed rest, TM practice led to higher alpha1 frontal log-power, and lower beta1 and gamma frontal and parietal log-power; higher frontal and parietal alpha1 interhemispheric coherence and higher frontal and frontal-central beta2 intrahemispheric coherence. eLORETA analysis identified sources of alpha1 activity in midline cortical regions that overlapped with the DMN. Greater activation in areas that overlap the DMN during TM practice suggests that meditation practice may lead to a foundational or ‘ground’ state of cerebral functioning that may underlie eyes-closed rest and more focused cognitive processes.     

EEG source imaging during two Qigong meditations

Experienced Qigong meditators who regularly perform the exercises "Thinking of Nothing" and "Qigong" were studied with multichannel EEG source imaging during their meditations. The intracerebral localization of brain electric activity during the two meditation conditions was compared using sLORETA functional EEG tomography. Differences between conditions were assessed using t statistics (corrected for multiple testing) on the normalized and log-transformed current density values of the sLORETA images. In the EEG alpha-2 frequency, 125 voxels differed significantly; all were more active during "Qigong" than "Thinking of Nothing," forming a single cluster in parietal Brodmann areas 5, 7, 31, and 40, all in the right hemisphere. In the EEG beta-1 frequency, 37 voxels differed significantly; all were more active during "Thinking of Nothing" than "Qigong," forming a single cluster in prefrontal Brodmann areas 6, 8, and 9, all in the left hemisphere. Compared to combined initial-final no-task resting, "Qigong" showed activation in posterior areas whereas "Thinking of Nothing" showed activation in anterior areas. The stronger activity of posterior (right) parietal areas during "Qigong" and anterior (left) prefrontal areas during "Thinking of Nothing" may reflect a predominance of self-reference, attention and input-centered processing in the "Qigong" meditation, and of control-centered processing in the "Thinking of Nothing" meditation.     

Aging and Visual Attention

ABSTRACT— Older adults are often slower and less accurate than are younger adults in performing visual-search tasks, suggesting an age-related decline in attentional functioning. Age-related decline in attention, however, is not entirely pervasive. Visual search that is based on the observer's expectations (i.e., top-down attention) is relatively preserved as a function of adult age. Neuroimaging research suggests that age-related decline occurs in the structure and function of brain regions mediating the visual sensory input, whereas activation of regions in the frontal and parietal lobes is often greater for older adults than for younger adults. This increased activation may represent an age-related increase in the role of top-down attention during visual tasks. To obtain a more complete account of age-related decline and preservation of visual attention, current research is beginning to explore the relation of neuroimaging measures of brain structure and function to behavioral measures of visual attention.     

Theta activity and meditative states: spectral changes during concentrative meditation

Brain oscillatory activity is associated with different cognitive processes and plays a critical role in meditation. In this study, we investigated the temporal dynamics of oscillatory changes during Sahaj Samadhi meditation (a concentrative form of meditation that is part of Sudarshan Kriya yoga). EEG was recorded during Sudarshan Kriya yoga meditation for meditators and relaxation for controls. Spectral and coherence analysis was performed for the whole duration as well as specific blocks extracted from the initial, middle, and end portions of Sahaj Samadhi meditation or relaxation. The generation of distinct meditative states of consciousness was marked by distinct changes in spectral powers especially enhanced theta band activity during deep meditation in the frontal areas. Meditators also exhibited increased theta coherence compared to controls. The emergence of the slow frequency waves in the attention-related frontal regions provides strong support to the existing claims of frontal theta in producing meditative states along with trait effects in attentional processing. Interestingly, increased frontal theta activity was accompanied reduced activity (deactivation) in parietal–occipital areas signifying reduction in processing associated with self, space and, time.     

An investigation of brain processes supporting meditation

Meditation is an ancient spiritual practice, which aims to still the fluctuations of the mind. We investigated meditation with fMRI in order to identify and characterise both the “neural switch” mechanism used in the voluntary shift from normal consciousness to meditation and the “threshold regulation mechanism” sustaining the meditative state. Thirty-one individuals with 1.5–25 years experience in meditation were scanned using a blocked on–off design with 45 s alternating epochs during the onset of respectively meditation and normal relaxation. Additionally, 21 subjects were scanned during 14.5 min of sustained meditation. The data were analysed with SPM and ICA. During the onset of meditation, activations were found bilaterally in the putamen and the supplementary motor cortex, while deactivations were found predominately in the right hemisphere, the precuneus, the posterior cingulum and the parieto–temporal area. During sustained meditation, SPM analysis revealed activation in the head of nucleus caudatus. Extensive deactivations were observed in white matter in the right hemisphere, i.e. mainly in the posterior occipito–parieto–temporal area and in the frontal lobes. ICA identified 38 components including known baseline-resting state components, one of which not only overlaps with the activated area revealed in the SPM analysis but extends further into frontal, temporal, parietal and limbic areas, and might presumably constitute a combination of frontoparietal and cinguloopercular task control systems. The identified component processes display varying degrees of correlation. We hypothesise that a proper characterisation of brain processes during meditation will require an operational definition of brain dynamics matching a stable state of mind.     

Stimulus expectancy modulates inferior frontal gyrus and premotor cortex activity in auditory perception

In studies on auditory speech perception, participants are often asked to perform active tasks, e.g. decide whether the perceived sound is a speech sound or not. However, information about the stimulus, inherent in such tasks, may induce expectations that cause altered activations not only in the auditory cortex, but also in frontal areas such as inferior frontal gyrus (IFG) and motor cortices, even in the absence of an explicit task. To investigate this, we applied spectral mixes of a flute sound and either vowels or specific music instrument sounds (e.g. trumpet) in an fMRI study, in combination with three different instructions. The instructions either revealed no information about stimulus features, or explicit information about either the music instrument or the vowel features. The results demonstrated that, besides an involvement of posterior temporal areas, stimulus expectancy modulated in particular a network comprising IFG and premotor cortices during this passive listening task.     

Inter-brain co-activations during mindfulness meditation. Implications for devotional and clinical settings

Mindfulness meditation usually takes place as personal, introspective activity. It is not known if this practice activates the brain differently when done alone or with someone else.Sixteen couples of expert meditators performed mindfulness-oriented meditation (MOM) and instructed mind-wandering (IMW) tasks in two conditions: once sitting in the same room (SR) and once in two different rooms (DR). Spontaneous electroencephalographic (EEG) data was collected during 7-minute recording sessions in the four experimental settings (MOM/SR, MOM/DR, IMW/SR, IMW/DR). Power in band was computed in separate clusters of independent components of the EEG signals.In addition to significant task effects, found in frontolimbic (MOM > IMW in gamma) and frontoparietal locations (MOM < IMW in theta), significant condition effects were found in frontal (SR > DR in delta) and in temporo-occipital regions (SR > DR in theta and alpha). Moreover, a significant interaction between task and condition revealed higher gamma activity in limbic areas during MOM/SR vs. MOM/DR settings. This effect was not attributable to gender, age nor the meditation expertise of participants.We thus show that the brains of two people work differently when they are doing something together or alone; some of these differences are specific to mindfulness meditation. Implications for devotional and clinical settings are discussed.     

Age-Related Changes in Neural Activation During Working Memory Performance

Changes in frontal lobe functions are a typical part of aging of the brain. There are age-related declines in working memory performance, a skill requiring frontal lobe activation. This study examined neural activation, using [15 O] water positron emission tomography (PET) methodology, during performance on two verbal working memory tasks in younger and older participants. The results demonstrated the typical areas of activation associated with working memory performance (e.g., dorsolateral prefrontal cortex and inferior parietal cortex) in both groups. However, the younger participants utilized the right dorsolateral prefrontal cortex and anterior cingulate gyrus significantly more than the older participants. In turn, the older participants used the left dorsolateral prefrontal cortex significantly more than the younger participants and maintained material-specific lateralization in their pattern of activation. These findings are consistent with a previous report of different age-related patterns of frontal activation during working memory.     

Auditory language comprehension: an event-related fMRI study on the processing of syntactic and lexical information

The functional specificity of different brain areas recruited in auditory language processing was investigated by means of event-related functional magnetic resonance imaging (fMRI) while subjects listened to speech input varying in the presence or absence of semantic and syntactic information. There were two sentence conditions containing syntactic structure, i.e., normal speech (consisting of function and content words), syntactic speech (consisting of function words and pseudowords), and two word-list conditions, i.e., real words and pseudowords. The processing of auditory language, in general, correlates with significant activation in the primary auditory cortices and in adjacent compartments of the superior temporal gyrus bilaterally. Processing of normal speech appeared to have a special status, as no frontal activation was observed in this case but was seen in the three other conditions. This difference may point toward a certain automaticity of the linguistic processes used during normal speech comprehension. When considering the three other conditions, we found that these were correlated with activation in both left and right frontal cortices. An increase of activation in the planum polare bilaterally and in the deep portion of the left frontal operculum was found exclusively when syntactic processes were in focus. Thus, the present data may be taken to suggest an involvement of the left frontal and bilateral temporal cortex when processing syntactic information during comprehension.     

Using fMRI to study recovery from acquired dysphasia

We have used functional magnetic resonance imaging (fMRI) to characterize brain activations associated with two distinct language tasks performed by a 28-year-old woman after partial recovery from dysphasia due to a left frontal hemispheric ischemic stroke. MRI showed that her ischemic lesion extended posteriorly from the left inferior frontal to the perisylvian cortex. fMRI scans of both language tasks revealed substantial differences in activation pattern relative to controls. The nature of this difference was task-specific. During performance of a verbal semantic decision task, the patient, in contrast to controls, activated a network of brain areas that excluded the inferior frontal gyrus (in either hemisphere). A second task involving rhyme judgment was designed to place a heavier cognitive load on language production processes and activated the left inferior frontal gyrus (Broca's area) strongly in normal controls. During this task, the most prominent frontal activation in the patient occurred in the right homologue of Broca's area. Subsequent analysis of this data by methods able to deal with responses of changing amplitude revealed additional, less sustained recruitment by the patient of cortex adjacent to the infarct in the region inferior to Broca's area during rhyming. These results suggest that in addition to changes in cognitive strategy, recovery from dysphasia could be mediated by both the preservation of neuronal networks in and around the infarct and the use of homologous regions in the contralateral hemisphere.     

Focused and Nonfocused Attention in Verbal and Emotional Dichotic Listening: An FMRI Study

Functional magnetic resonance imaging (fMRI) was used to identify cortical regions which are involved in two dichotic listening tasks. During one task the subjects were required to allocate attention to both ears and to detect a specific target word (phonetic task), while during a second task the subjects were required to detect a specific emotional tone (emotional task). During three attentional conditions of each task, the subjects were required to focus attention to the right (FR) or left ear (FL), while during a third condition subjects were required to allocate attention to both ears simultaneously. In 11 right-handed male subjects, these dichotic listening tasks evoked strong activations in a temporofrontal network involving auditory cortices located in the temporal lobe and prefrontal brain regions. Hemodynamic responses were measured in the following regions of interest: Heschl's gyrus (HG), the planum polare (PP), the planum temporale (PT), the anterior superior temporal sulcus (aSTS), the posterior superior temporal sulcus (pSTS), and the inferior frontal gyrus region (IFG) of both hemispheres. The following findings were obtained: (1) the degree of activation in HG and PP depends on the direction of attention. In particular it was found that selectively attending to right-ear input led to increased activity specifically in the left HG and PP and attention to left ear input increased right-sided activity in these structures; (2) hemodynamic responses in the PT, aSTS, pSTS, and IFG were not modulated by the different focused-attention conditions; (3) hemodynamic responses in HG and PP in the nonforced conditions were the sum activation of the forced conditions; (4) there was no general difference between the phonetic and emotion tasks in terms of hemodynamic responses; (5) hemodynamic responses in the PT and pSTS were strongly left-lateralized, reflecting the specialization of these brain regions for language processing. These findings are discussed in the context of current theories of hemispheric specialization.     

The functional anatomy of inspection time: a pilot fMRI study

Seven healthy subjects underwent functional magnetic resonance imaging (fMRI) of the brain while performing an inspection time task. Employing a block-type design, the task had three difficulty levels: a control condition, an easy (200 ms stimulus duration), and a more difficult (40 ms) discrimination. Based on group results, there were widespread significant areas of difference in brain activation and deactivation when pairwise comparisons were conducted among the three task conditions. When the difficult condition was compared with the easy condition, there was relative activation in areas of the following brain regions: cingulate gyrus and some frontal and parietal lobe areas. Areas within the following regions showed relative deactivation (greater blood oxygenation level-dependent, BOLD, signal in the easy condition): frontal, temporal, and parietal lobe. There were overlaps between these areas and those found to be active while performing higher cognitive tasks in other functional brain imaging studies. These pilot data encourage future studies of the functional anatomy of inspection time and its relevance to psychometric intelligence.     

The Enhancement of Visuospatial Processing Efficiency Through Buddhist Deity Meditation

ABSTRACT— This study examined the effects of meditation on mental imagery, evaluating Buddhist monks' reports concerning their extraordinary imagery skills. Practitioners of Buddhist meditation were divided into two groups according to their preferred meditation style: Deity Yoga (focused attention on an internal visual image) or Open Presence (evenly distributed attention, not directed to any particular object). Both groups of meditators completed computerized mental-imagery tasks before and after meditation. Their performance was compared with that of control groups, who either rested or performed other visuospatial tasks between testing sessions. The results indicate that all the groups performed at the same baseline level, but after meditation, Deity Yoga practitioners demonstrated a dramatic increase in performance on imagery tasks compared with the other groups. The results suggest that Deity meditation specifically trains one's capacity to access heightened visuospatial processing resources, rather than generally improving visuospatial imagery abilities.     

Mindfulness meditation and consciousness: An integrative neuroscientific perspective

Although mindfulness meditation has been practiced in the East for more than two millennia, Western scientific research and healthcare programs have only recently drawn their attention to it. Basically, the concept of mindfulness hinges on focusing on one’s own awareness at the present moment. In this review we analyze different hypotheses about the functioning and the cerebral correlates of mindfulness meditation. Since mindfulness is strictly associated with a particular state of consciousness, we also examine some of the most relevant theories that have been proposed as accounts of consciousness. Finally, we suggest that consciousness and mindfulness meditation can be integrated within a neuroscientific perspective, by identifying the brain areas which seem to play an essential role in both, namely the anterior cingulate cortex, posterior cingulate cortex, insula and thalamus.     

The Effect of Attention Allocation Instructions on Self-paced Task Performance under Quiet and Distracted Conditions

This study examined the effectiveness of external and internal focusing attention instructions on the performance of three throwing tasks under both quiet and distracted conditions. The main finding was that during acquisition, the external focus of attention led to improved performance when compared to internal focus of attention and control, but only under quiet conditions. It was also found that during auditory and visual distraction conditions, both types of focus attention produced similar levels of performance, and both groups were superior to the control condition. It is suggested that sport psychology consultants provide their athletes with external focusing attention instructions.     

Cultural influences on neural substrates of attentional control

Behavioral research has shown that people from Western cultural contexts perform better on tasks emphasizing independent (absolute) dimensions than on tasks emphasizing interdependent (relative) dimensions, whereas the reverse is true for people from East Asian contexts. We assessed functional magnetic resonance imaging responses during performance of simple visuospatial tasks in which participants made absolute judgments (ignoring visual context) or relative judgments (taking visual context into account). In each group, activation in frontal and parietal brain regions known to be associated with attentional control was greater during culturally nonpreferred judgments than during culturally preferred judgments. Also, within each group, activation differences in these regions correlated strongly with scores on questionnaires measuring individual differences in culture-typical identity. Thus, the cultural background of an individual and the degree to which the individual endorses cultural values moderate activation in brain networks engaged during even simple visual and attentional tasks.     

Functional neuroimaging of speech perception during a pivotal period in language acquisition

A pivotal period in the development of language occurs in the second year of life, when language comprehension undergoes rapid acceleration. However, the brain bases of these advances remain speculative as there is currently no functional magnetic resonance imaging (fMRI) data from healthy, typically developing toddlers at this age. We investigated the neural basis of speech comprehension in this critical age period by measuring fMRI activity during passive speech comprehension in 10 toddlers (mean +/- SD; 21 +/- 4 mo) and 10 3-year-old children (39 +/- 3 mo) during natural sleep. During sleep, the children were presented passages of forward and backward speech in 20-second blocks separated by 20-second periods of no sound presentation. Toddlers produced significantly greater activation in frontal, occipital, and cerebellar regions than 3-year-old children in response to forward speech. Our results suggest that rapid language acquisition during the second year of life may require the utilization of frontal, cerebellar, and occipital regions in addition to classical superior temporal language areas. These findings are consistent with the interactive specialization hypothesis, which proposes that cognitive abilities develop from the interaction of brain regions that include and extend beyond those used in the adult brain.     

Seeing minds in others: Mind perception modulates low-level social-cognitive performance and relates to ventromedial prefrontal structures

In social interactions, we rely on nonverbal cues like gaze direction to understand the behavior of others. How we react to these cues is affected by whether they are believed to originate from an entity with a mind, capable of having internal states (i.e., mind perception). While prior work has established a set of neural regions linked to social-cognitive processes like mind perception, the degree to which activation within this network relates to performance in subsequent social-cognitive tasks remains unclear. In the current study, participants performed a mind perception task (i.e., judging the likelihood that faces, varying in physical human-likeness, have internal states) while event-related fMRI was collected. Afterwards, participants performed a social attention task outside the scanner, during which they were cued by the gaze of the same faces that they previously judged within the mind perception task. Parametric analyses of the fMRI data revealed that activity within ventromedial prefrontal cortex (vmPFC) was related to both mind ratings inside the scanner and gaze-cueing performance outside the scanner. In addition, other social brain regions were related to gaze-cueing performance, including frontal areas like the left insula, dorsolateral prefrontal cortex, and inferior frontal gyrus, as well as temporal areas like the left temporo-parietal junction and bilateral temporal gyri. The findings suggest that functions subserved by the vmPFC are relevant to both mind perception and social attention, implicating a role of vmPFC in the top-down modulation of low-level social-cognitive processes.