Principles and Neurobiological Correlates of Concentrative, Diffuse, and Insight Meditation
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NEUROBIOLOGY Editor: Rakesh Karmacharya, MD, PhD
Principles and Neurobiological Correlates of
Concentrative, Diffuse, and Insight Meditation
Craig Mehrmann, BS, and Rakesh Karmacharya, MD, PhD
Keywords: Buddhism, central executive network, default mode network, diffuse attention, focused attention, insight,
intrinsic connectivity network, meditation, mindfulness, salience network
T
he term meditation encompasses a broad variety of Concentrative and diffuse meditation practices are of-
mental-training practices that vary between cultures ten combined, whether in a single session or over the course
and traditions, ranging from techniques designed to of the practitioner’s training, and are intentionally designed
promote physical health, relaxation, and improved concen- to train specific cognitive processes.6 In many instances,
tration, to exercises performed with farther-reaching goals, the attentional stance cultivated through meditation not
such as developing a heightened sense of well-being, cul- only is characterized by the style of meditation (i.e., concen-
tivating altruistic behaviors, and, for some, attaining en- trative or diffuse) but also includes the awareness of certain
lightenment.1 Meditation can be conceptualized as complex philosophical principles (or metaphysical characteristics)
emotional and attentional regulatory practices in which men- that support practitioners’ ability to impartially perceive
tal and somatic events are affected by specific mental-training their reality. In other words, the attentional stance often
practices.2 Meditation is typically associated with a concur- integrates the continuous awareness of certain metaphys-
rent state of heightened vigilant awareness and reduced ical characteristics that act as a medium through which
metabolic activity3—which lead to improved physical health,4 practitioners may objectively observe their sensory experi-
psychological balance, and emotional stability.5 Not all med- ence. Such characteristics often include the perpetual tran-
itation practices focus on the training of specific cognitive sience of all phenomena, the illusion of a separate and
skills, and in those that do, the methodologies and out- permanent self or ego, and the understanding that one will
comes often vary. It is therefore essential to be explicit never ultimately be satisfied by sense objects—hence the
about the type of meditation practice under investigation. term insight meditation, which refers to a form of diffuse
Different types of meditation can be classified based on meditation that is practiced with the continual awareness
how the practitioner’s attentional processes are regulated or experience of these philosophical principles, and with
and directed.6 In this article we focus on the two most com- an emphasis on experiencing impermanence or change
mon styles of meditation derived from Buddhist traditions: (i.e., the continual arising and passing of phenomena from
(1) concentrative, or focused-attention, meditation, and moment to moment).
(2) diffuse, or open-monitoring, meditation. Concentrative Western scientific interest in meditation has grown tre-
meditation involves maintaining and continually refocusing mendously in recent years, reflecting the increased appli-
attention on a chosen object, such as a body sensation, single cation of meditation-based modalities in clinical settings.
point in space, color, object, sound, or affective state such as However, the scientific study of meditation has, in large
compassion. Open-monitoring meditation involves developing part, been conducted with minimal reference to its religious
a present-centered and unattached/neutral mode of observa- and spiritual origins.7 Buddhist traditions offer widely ap-
tion toward all sensational phenomena, including thoughts. plied, extensive, precisely descriptive, and highly detailed
theories about concentrative and diffuse forms of medita-
tion, which have remained intrinsically unchanged for over
From the Center for Human Genetic Research, Massachusetts General 2500 years and are presented in a systematic manner befit-
Hospital, Boston, MA (Mr. Mehrmann and Dr. Karmacharya); Harvard
Medical School and Chemical Biology Program, Broad Institute of Harvard ting a scientific approach.6 Mindfulness-based therapeutic
and MIT (Dr. Karmacharya); Schizophrenia and Bipolar Disorder Program, programs are all derivatives of traditional Buddhist medita-
McLean Hospital, Belmont, MA (Dr. Karmacharya). tion. The theory and practice of concentrative, diffuse, and
Supported, in part, by National Institutes of Health Mentored Clinical Sci- insight meditation are at the core of these programs, making
entist Research Career Development Award no. K08MH086846 (RK).
these meditation practices the basis for most applications
Correspondence: Rakesh Karmacharya, MD, PhD, Massachusetts General
Hospital, Center for Human Genetic Research, 185 Cambridge St., Boston, in clinical and psychiatric settings.1,8,9 Mindfulness-based
MA 02114. Email: karmacharya@mcb.harvard.edu therapeutic programs have become a popular form of
© 2013 President and Fellows of Harvard College therapeutic intervention: they are efficacious; their princi-
DOI: 10.1097/HRP.0b013e31828e8ef4 ples are universal; they are cost-effective; and they are
Harvard Review of Psychiatry www.harvardreviewofpsychiatry.org 205
Copyright @ 2013 President and Fellows of Harvard College. Unauthorized reproduction of this article is prohibited.C. Mehrmann and R. Karmacharya
highly adaptable for diverse populations with different cog- from the attentional field without further involvement,
nitive abilities.7,10 Moreover, these programs have made and (3) to restore attention promptly to the chosen object
training in concentrative and diffuse meditation more ac- of focus.1,6
cessible by offering what one may consider a nonreligious Concentrative meditation develops the three regulative
alternative for individuals who may be unwilling to adopt skills to the point that advanced practitioners have an espe-
Buddhist terminology.7 cially acute ability to notice when the mind has wandered,
A third style of meditation, known as transcendental resulting in an automatic and instantaneous restoration of
meditation (TM), has been extensively researched and en- attention on the chosen object of focus.6 Eventually, atten-
compasses the remaining forms of meditation practice. tion rests more readily and stably on the chosen object. As
TM practice is centered on the repetition of a mantra, concentration continues to develop, the regulative skills are
and emphasizes the development of a witnessing, thought- invoked less and less frequently, and soon the ability to sus-
free “transcendental awareness” or “pure consciousness” tain focus becomes “effortless,” a state commonly known
that is described by practitioners to be “the original source as access concentration.1,12 The achievement of access con-
of thought.”11 This state is explicitly said to be cultivated centration is often considered the appropriate time to begin
in the absence of any concentration or effort and is charac- practicing diffuse meditation; however, this relatively high
terized by the experiences of “unboundedness” and “loss of degree of concentration is not absolutely necessary for the
time, space, and body sense,” thus placing TM in a medita- beginning stages of diffuse meditation.
tion category of its own.1,11 TM is not easily comparable Diffuse meditation is done with the aim of becoming
and is relatively unrelated to mindfulness-based meditation more objectively aware of sensate experience through the de-
techniques and therefore will not be discussed here. velopment of one’s ability to be psychologically present and
The theory and practice of meditation are not grounded equanimous with all forms of sensory phenomena. This
in mysticism or in religious dogma, rites, rituals, or ceremo- state involves the nonreactive monitoring of the ongoing
nies, and may rather be accurately described as composing stream of experience from moment to moment, without fo-
a detailed and precisely descriptive scientific technique. Me- cusing on any explicit object for a prolonged period of
ditation is universal in nature; meditation methodologies are time.13 Practitioners aim to familiarize themselves with re-
equally applicable to individuals of any religious, cultural, ality at the pure sensate level, without interpretation of, or
or spiritual background; and the practice of meditation does identification with, sensational phenomena. In the context
not require any form of conversion or identification with a of meditation, sensate refers to anything that can be men-
religious tradition. Many Westerners, however, are unfamil- tally observed, including thoughts.
iar with the cultural context in which the terminology of The prelude to diffuse meditation typically involves con-
Buddhist meditation has developed. This lack of knowl- centrative meditation to calm and focus the mind, reduce
edge has, in some cases, resulted in misinterpretations of distractions, and enhance one’s equanimity toward sensa-
meditation practices as well as in unwarranted religious or tional phenomena. For example, the practitioner may use
dogmatic stigma being attached to them. To help bridge this concentrative meditation focusing on breath sensations at
cultural boundary, we present an introduction to the principles the area of the philtrum (the indentation below the nostrils
and clinical applications of concentrative and diffuse forms of and above the upper lip). Continually monitoring breath
meditation. We also review relevant scientific studies to date sensations in the chosen area develops equanimity (or non-
on concentrative and diffuse meditation, and discuss the clin- reactivity) toward body sensations and enables the practi-
ical implications of these findings. Following a discussion of tioner to disengage from, quiet, and eventually stop the
the philosophical basis and neurological underpinnings of internal dialogue of the mind. From here, the practitioner
these practices and how they apply to modern psychiatry, may shift to diffuse meditation even if access concentra-
we suggest further directions for scientific research. tion has not yet been established, so long as the awareness
of breath sensations is maintained with relative continuity.
CONCENTRATIVE AND DIFFUSE MEDITATION The practitioner would then work at continually disenga-
Concentrative meditation is often practiced in preparation ging from body-mind sensations as quickly as possible until
for practicing diffuse meditation and, as noted earlier, en- a continual stream of awareness, or access concentration,
tails voluntarily focusing attention on a chosen object in a has been established. Otherwise, as previously described,
sustained fashion, such as breath sensations or a visual object, practitioners would practice concentrative meditation on
visualized image, sound, or affective state (e.g., compassion).6 breath sensations until access concentration has been estab-
To sustain this focus, practitioners must constantly monitor lished, and then redirect their focus from breath sensations
and regulate their quality of attention, thereby naturally to begin practicing diffuse meditation. Usually, practi-
developing three regulatory skills: (1) to monitor and re- tioners direct their attention to the most subtle (or least per-
main vigilant to distractions, thereby enabling practitioners ceptible) features of experience possible.
to recognize when and to what degree their attention has Open-monitoring meditation enhances one’s faculty of
wandered from the object of focus, (2) to release distractions present-centered, nonjudgmental awareness of psychosomatic
206 www.harvardreviewofpsychiatry.org Volume 21 • Number 4 • July/August 2013
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phenomena, thereby enhancing cognitive flexibility and distinguishing the individual self from the selves of others
reappraisal.1 This state is accomplished through nonreac- and objects, whereas experiential focus refers to the neuro-
tive, metacognitive monitoring of body-mind sensations— psychological experience of the present moment, without
which gradually increases awareness of “automatic cognitive ruminative, ego-centered interpretation of sense objects.17
and emotional interpretations of sensory, perceptual, and In the context of meditation, it is useful to think of expe-
endogenous stimuli.”1,13–15 With consistent practice, the riential focus as the experience of life through the “internal,
practitioner becomes progressively more aware of sub- present-centered, objective mental observer.” To observe
tle body-mind sensations, lending access to rich features means to watch impartially as an outsider. The internal ob-
of sensational experience, such as emotional tone, ac- server is that which enables us to experience a sensation
tive cognitive schema, awareness of sensation all over the without identifying with it, or figuratively “stand next to”
body (inside and out), degree of phenomenal intensity, and a sensation and observe it objectively. Through meditation,
bodily vibrational frequency6 (i.e., the literal, physical expe- one becomes aware of this observer and develops one’s
rience of the body and mind as “vibrations,” or rapidly os- ability to make a continuous and objective observation of
cillating particular sensational phenomena whose strength one’s sensate reality. Therefore, practicing experiential focus
[amplitude] and speed [frequency] fluctuate over time). One may be described as practicing present-centered awareness
also develops the ability to experience the arising and by “continually disengaging attentional processes from self-
passing of phenomena at a high velocity and at very subtle referential elaboration toward sense objects.”17,18
levels6—that is, the literal and distinct physical or mental ex-
perience of the arising and passing of particular phenomena
up to 50 times per second. The subtlety of the practi- MINDFULNESS-BASED MEDITATION
tioners’ experience is in direct accordance with their con- Mindfulness-based therapeutic techniques have been exten-
centrative capacity (the degree of effort exerted to observe sively incorporated into the psychiatric setting as evidence-
the subtlest sensations possible while remaining continu- based therapeutic programs, such as mindfulness-based
ously aware of, and equanimous toward, the internal sen- stress reduction (MBSR),9 dialectical behavioral therapy,19
sate experience). acceptance and commitment therapy,20 relapse-prevention
Practitioners continue to practice meditation’s concen- therapy,21 and mindfulness-based cognitive therapy,22 and
trative or diffuse techniques in everyday life, which enables have been shown to be effective in treating depression,23
them to maintain a wholesome lifestyle and contributes to anxiety,24 drug and alcohol addiction,7,25 and various person-
their degree of readily accessible concentrative absorption ality disorders.7,19,26,27 In the clinical setting, these programs
during formal meditation. The degree of concentrative ab- are popular interventions for hypertension, stress, and cardio-
sorption refers to the depth or strength of concentration vascular illness, and in slowing and perhaps stopping or re-
on a single-pointed focus and, during formal meditation, versing neurodegeneration and cognitive decline.7,27
correlates directly with how well the continuity of aware- Mindfulness may be conceptualized as bringing one’s
ness has been maintained since the previous meditation ses- complete attention to one’s present experience through the
sion. For example, practitioners may strive to maintain a nonjudgmental observation of the ongoing stream of all per-
continuous awareness of breath sensations or of an affec- ceivable internal and external stimuli as they arise from mo-
tive state such as compassion, or try to maintain a continu- ment to moment.28 Thus, mindfulness is remembering to
ous superficial “body-scan” throughout the day. Advanced pay attention in a particular way: on purpose, in the pres-
practitioners report a sense of physical lightness and in- ent moment, and nonjudgmentally.28 Dakwar and Levin7
creased mental and physical vitality as a result of maintaining have compiled several psychological mechanisms through
a concentrated mind.12 This perception may be explained in which mindfulness may aid in psychiatric symptom reduc-
part by a possible correlation between increased concentra- tion and behavioral change. It has been shown that an
tion and decreased emotional reactivity, accounting for a accepting and nonjudgmental mental outlook toward dis-
more efficient use of energy both during meditation and tressing phenomena can reduce associated stress.15 For ex-
in everyday life.15,16 ample, patients with borderline personality disorder who
Significant progress has been made recently in investi- have learned to observe distressing thoughts and feelings
gating the effects of consistent concentrative and diffuse without dissociation show diminished fear response and
meditation practice on systems for sensory processing and cessation of avoidance behaviors previously triggered by
integration, revealing two temporally distinct neural modes those stimuli.19 This effect may be attributed to a kind of
of self-reference: (1) extended self-reference linking subjec- habituation/desensitization therapy, where a repetitious,
tive experience across time (narrative focus, also known as but intentionally objective, cognitive exposure toward the
the default mode) and (2) momentary self-reference centered distressing stimulus gradually reduces its associated nega-
on the present moment (experiential focus).17 Narrative tive significance.7
focus is characterized by relating to the world through a Training in mindfulness may also assist in recognizing
construction of narratives that constitute the I or self, maladaptive coping skills and aid in implementing better
Harvard Review of Psychiatry www.harvardreviewofpsychiatry.org 207
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ones.7 A nonjudgmental attitude toward phenomena fos- is in a state of severe psychological turmoil, such as psycho-
ters cognitive flexibility and reappraisal, and therefore may sis or suicidal depression, then providing a quiet, peaceful
lead to changes in thought patterns or attitudes about one’s environment with positive human influence, healthy food,
thoughts.1,7 The unattached or neutral appraisal of one’s and necessary medications may be the first step in helping
thoughts and emotions may reduce automatic reactivity to- them to establish a balanced mind capable of developing
ward them, thereby enabling those who have learned mind- the foundations of mindfulness practice. Nevertheless, these
fulness to shift from maladaptive thought patterns and modified treatments consider the practice of meditation
behaviors to ones that are more adaptive.29 Increased un- techniques to be central to their therapeutic efficacy.7,9,10
attached awareness of behavioral, cognitive, and emo- Mindfulness-based meditation works under the premise
tional stimuli may improve stress tolerance, the ability to that all individuals—health care providers and patients
recognize behavioral consequences, and the ability to set alike—can benefit from objective self-observation. It has
healthy motivations into action.4,7,19,30 Mindfulness-based been shown that health care professionals who regularly
acceptance may also aid in reducing dissociative adaptations practice mindfulness meditation, particularly those in the
toward feelings or thoughts, as seen in borderline personal- psychiatric setting, are better equipped to treat patients. For
ity disoroder.7 Developing one’s faculty of unattached obser- example, a recent study found that participation in an eight-
vation and acceptance of distressing thoughts or feelings week mindfulness-based stress reduction program was as-
may reduce the likelihood of maladaptive behavior patterns. sociated with improved mental health in graduate-level
For example, borderline patients who practice accepting psychology students.32 When compared to a control group,
their chronic feelings of emptiness may engage less fre- students in the MBSR program reported significant pre/
quently in self-destructive and self-injurious behaviors that post declines in perceived stress, negative affect, state and
were previously used to distract from those feelings.7,19 trait anxiety, and rumination, and a significant increase in
As with Buddhist meditation, participants undergoing positive affect and self-compassion. Compassion may be
mindfulness-based therapy sit in a calm, but vigilant, posi- described as a nonpossessive state of loving that is moti-
tion and observe their object of attention (e.g., breath, body vated by a person’s own sense of well-being with regard
parts, thoughts) without judgment or rumination and as to his or her interactions and connectedness with others.33
continuously as possible. However, a mindfulness-based ap- Developing self-compassion is particularly relevant to the
proach to therapy does not necessarily require formal medi- fields of counseling and therapy. It has been purported that
tation in the strict sense.7 The goal of mindfulness-based in order to have compassion toward one’s client, which is
treatment is to promote mindfulness in the patients accord- an essential aspect of conducting effective therapy,32–34 a
ing to their own capacities. For instance, a patient with de- therapist must first have compassion toward him- or herself.
velopmental disabilities, brain damage, severe depression Research shows that counselors and therapists lacking in self-
or mania, anxiety, or psychosis may be unable to practice compassion are more critical and controlling toward them-
formal sitting meditation. Often, patients may refuse to selves, and are also more critical and controlling toward their
practice because they do not clearly understand its purpose. patients, resulting in poorer patient outcomes.32,35
Therefore, some strategies offer mindfulness-promoting
cognitive exercises that may seem more engaging, less stress-
ful, or more practical to some individuals. Such strategies in- NEUROBIOLOGICAL STUDIES OF MEDIATION
clude group discussions, lectures, worksheets, readings, or Many studies have shown that meditation and meditation-
cognitive exercises such as guided imagery or metaphor to derived therapeutic approaches improve overall physical and
aid in the development of mindfulness-based insights.7 mental health.4,10,36 In this section, we present findings from
For example, participants may be asked to visualize their imaging, electroencephalography (EEG), and physiological
thoughts as debris floating over a river, watching their studies that relate to biological effects observed with
thoughts come and go, giving them as much importance meditation.
as they would a piece of passing driftwood.31 Participants
are also encouraged to develop an unattached relationship Brain Imaging
to phenomena through intellectual concepts such as the Intrinsic connectivity networks are large-scale brain net-
transient nature of sensations and thoughts, helping them works that may function either in an active (engaged) or
to understand that even the most difficult or agitating passive (resting) state, suggesting that the human brain is
thoughts and feelings are bound to change. This understand- organized into distinct functional networks.37 Significant
ing fosters the ability to experience painful thoughts or progress has been made in investigating the effect of consistent
feelings more presently and calmly, allowing space for con- meditation practice on systems for sensory processing and inte-
templation, reevaluation, and the ability to allow them to gration, revealing two temporally distinct neural modes of
pass on without further elaboration.7 Patients are also en- self-reference: (1) momentary self-reference centered on the
couraged to practice mindfulness at home and in everyday present moment (experiential focus), neurologically corre-
life, such as while walking, eating, or talking. If the patient lated with the central executive network, and (2) extended
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self-reference linking subjective experience across time (nar- network are correlated with more prominent psychotic
rative focus), neurologically correlated with the default symptoms.40 The study also found a significant increase in
mode network.17,37,38 hyperactivity and hyperconnectivity of the default mode
The default mode network comprises an integrated sys- network in immediate family members of schizophrenic
tem for autobiographical, self-centered, and social cognitive individuals as compared to individuals from families with
functions characterized by ruminative, often subconscious, no occurrence of schizophrenia.
self-referential narrative thought linking subjective experi- Another recent fMRI study analyzed working-memory,
ence across time—which generates one’s concept of self or task-induced modulation of default mode network activity
identity.39 The default mode network concept emerged from in subjects with posttraumatic stress disorder (PTSD) com-
a body of evidence demonstrating a consistent pattern of de- pared to healthy controls.47 The control group showed sig-
activation across a distributed network of brain regions dur- nificantly stronger connectivity in areas implicated in the
ing focused mental tasks; these regions become activated in salience and executive networks, such as the right inferior
the absence of such focused mental tasks.39 The brain re- frontal gyrus and the right inferior parietal lobule. How-
gions include the posterior cingulate cortex (involving au- ever, the PTSD group showed stronger connectivity in areas
tobiographical memory and self-referential processes), the implicated in the default mode network, such as stronger
ventromedial prefrontal cortex (VMPFC) (involving social- connectivity between the posterior cingulate cortex and the
cognitive processes related to self and others), the medial right superior frontal gyrus, and between the medial pre-
temporal lobe (involved in episodic memory), and the angu- frontal cortex (MPFC) and the left parahippocampal gyrus.
lar gyrus (involved in semantic processing).37 Conversely, Subjects with PTSD showed a significantly impaired abil-
the central executive network is activated (and default mode ity to switch from an idling state into a task-oriented state
network deactivated) during focused mental tasks and is an- when compared to healthy controls, as implied by hypercon-
chored in the dorsolateral prefrontal cortex (DLPFC) and nectivity in the default mode network during the working-
the posterior parietal cortex.37 There is a third intrinsic con- memory task in the PTSD group.47 The different patterns
nectivity network, known as the salience network, acting as of connectivity suggest significant group differences in the
a switch or “toggle” between the activation/deactivation of ability to disengage from the default mode network and
the central executive network and default mode network, to engage the central executive network during tasks that
depending on the degree of mental engagement. The salience require focused attention.47
network is anchored in the anterior insula (AI) and the ante- The psychological characteristics associated with default
rior cingulate cortex (ACC).37 mode network activation are commonly known distrac-
Abnormal default mode network activity has been impli- tions in the meditation milieu, such as daydreaming, mind
cated in a number of psychiatric diseases, including schizo- wandering, and projections into the past or future, which
phrenia,40 autism,41,42 epilepsy,43 depression44 and anxiety has led researchers to investigate the effects of meditation
disorders,45–47 bipolar disorder,44 attention-deficit/hyperactivity on default mode network activity.52 An fMRI study com-
disorder (ADHD),44 and Parkinson’s and Alzheimer’s pared differential brain-activation patterns during two dis-
diseases.44 In many of these cases, particularly in schizo- tinct modes of perception: narrative focus correlated with
phrenia,40 ADHD,44 bipolar disorder,44 and depression/ default mode network activation, and experiential focus
anxiety disorders,45–47 an inability to “switch off” the hy- correlated with the central executive network activation,
peractive default mode network through focusing the mind in both novice participants and participants who had at-
appears to be a major contributor to the disease.44 A recent tended an eight-week course in mindfulness meditation.17
study conducted by Whitfield-Gabrieli and colleagues40 used In novices, experiential focus yielded focal reductions in self-
fMRI to examine potential alterations in default mode net- referential cortical midline regions associated with narrative
work activity in subjects with schizophrenia. While pointing focus. In trained participants, experiential focus resulted
out that the default mode network is activated during in- in more marked and pervasive reductions in the MPFC, in-
ternal, self-referential thought, the authors noted that the cluding the rostral subregions of the dorsal MPFC and ven-
normal boundary between internal thought and external tral MPFC, suggesting that present-centered experience may
perceptions might be blurred by hyperactivity of the default rely on suppression of MPFC representations supporting
network.40 This suggestion is consistent with psychotic narrative focus. Trained participants also showed marked
symptoms in schizophrenia whereby patients have an exag- reductions in the MPFC and increased recruitment of a
gerated sense of self-reference in the world, as evidenced by right lateralized network, comprising the right lateral PFC
paranoia, and a blurring of internal thoughts and external and viscerosomatic areas such as the insula, secondary so-
perception, which may give rise to hallucinations.40 In line matosensory cortex, and inferior parietal lobule. Moreover,
with these observations, results indicate that the default right insular functional connectivity analysis revealed a
mode network is hyperactive and hyperconnected in people strong coupling between the right insula and the VMPFC
with schizophrenia and that the strength of connectivity and in novices that was uncoupled in the mindfulness group, sug-
the defect in appropriate deactivation of the default mode gesting viscerosomatic signals are by default associated with
Harvard Review of Psychiatry www.harvardreviewofpsychiatry.org 209
Copyright @ 2013 President and Fellows of Harvard College. Unauthorized reproduction of this article is prohibited.C. Mehrmann and R. Karmacharya
activation in the VMPFC.17 This decoupling in the trained may be a neurological reflection of continually disengaging
mindfulness group was replaced by an increased coupling from distractors caused by default mode network activa-
of the right insula with the DLPFC during formal meditation, tion and reengaging with the object of focus during focused
which may reflect a neuronal reorganization that supports a mental processing (i.e., toggling between the default mode
continuous, present-centered attentional stance.17 network and central executive network). However, the
In another fMRI study, brain activity patterns observed DLPFC, as part of the central executive network, is pre-
during concentrative and diffuse meditation were contrasted dominantly activated during continual focused attention,
in an experiment between expert Buddhist monks and lay which is confirmed by predominant DLPFC activation dur-
novices with an integrated concentrative/diffuse paradigm, ing formal concentrative meditation. It would be interest-
where involvement of differential brain activations was an- ing to see if there is a gradual reduction in ACC/salience
alyzed between groups during concentrative and diffuse and default mode network activation with a concurrent,
meditation with reference to rest.38 No particular interest corresponding increase in DLPFC/central executive network
was given to identifying previously theorized large-scale activation during a concentrative meditation session in ex-
brain networks, such as the aforementioned intrinsic con- pert participants—and, if so, how this result correlates with
nectivity network. Striking differences between activity pat- the reported strength of concentration during the session.
terns were found between the groups. Activity patterns The findings also address the question of whether medita-
during diffuse meditation resembled the ordinary brain- tive states are associated with a transient deactivation50,51
resting state in monks, but not in controls, suggesting that or activation11,13 of executive brain areas. The findings
monks also maintain an open-monitoring attentional stance clearly show that executive areas are activated during
during nonformal meditation conditions (i.e., in everyday meditation.38
life).38 There may be a meditation-related functional reor- Another recent study examined meditation-induced cor-
ganization of brain activity patterns in the prefrontal cortex tical gyrification to shed light on anatomical correlates of
and insula in expert practitioners, reflected by a substan- meditation and meditation-related neuroplasticity through-
tially increased reliance on the central executive network out the lifespan.52 Gyrification refers to the pattern and
and decreased reliance on the default mode network during degree of cortical folding on the surface of the brain. Par-
nonformal meditation conditions.38 Neuronal populations ticipants consisted of a large sample (n = 100) of long-term
in regions typically associated with self-referential processing insight meditators and age- and sex-matched controls. The
during everyday life may have been reallocated to support degree of cortical gyrification was established by calculat-
areas that are involved in metacognition of phenomenal ex- ing mean curvature with a 3-D version of a well-known
perience; that is, objective, present-centered awareness.13 gyrification magnetic resonance imaging index across thou-
Several crucial aspects of Buddhist meditation practice are sands of cortices on individual cortical surface models. When
relevant here—all of which relate to transcending concep- applying more liberal significance thresholds (p < 0.05),
tions of a separate self or ego—such as the cultivation of gyrification was larger in meditators as well as in controls
mental states of unconditional love, compassion, and kind- overall.52 However, meditators showed larger gyrification
ness, or remaining continually aware of impermanence, or in some of the areas where prior analyses revealed thicker
the arising and passing of particular sensational phenomena gray matter cortices in meditators as compared to nonmedi-
from moment to moment.8,33,38,48,49 Moreover, this finding tators.52,53 Regions included the anterior insula,53 left ante-
is consistent with the goal of meditation, which is to disin- rior temporal gyrus,54,55 left central sulcus and vicinity,52,56
tegrate the experiential psychological distinction between and right parietal operculum, which houses the secondary
meditation and normative functioning over time.48,49 somatosensory cortex.52,56 Stricter significance thresholds
The study also found that the ACC and DLPFC play an- (p < 0.01) revealed five distinct regions where cortical gyr-
tagonistic roles in the executive control of attention setting ification was exclusively larger in meditators: the left pre-
in monks during meditation.38 A negative correlation be- central gyrus, left and right anterior insula, right fusiform
tween ACC activation and DLPFC deactivation during rest gyrus, and left cuneus, showing a global maximum in the
was found, possibly suggesting increased reliance upon the right AI.52 As previously mentioned, the AI has been shown
salience network when distraction is more likely, such as to play a crucial role in switching between the default mode
during resting state.38 This may be a functional reflection network and central executive network.37 The current study
of increased reliance on the ACC/salience network and de- suggests a correlation between AI gyral complexity and the
creased reliance on the DLPFC/central executive network number of years spent practicing meditation.52 Although
during rest, and a decreased reliance on the ACC/salience the findings of this study should be interpreted with caution
network and increased reliance on the DLPFC/central exec- since it did not correct for multiple comparisons, previ-
utive network during concentrative meditation. Note that ous studies have likewise shown structural differences be-
concentrative meditation is used to establish (or reestablish) tween meditators and nonmeditators within the AI.53–55,57
concentration when concentration is weak. Predominant Moreover, functional analyses have shown activation of
ACC activation during rest, as part of the salience network, the insula during meditation,52 supporting the notion that
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the salience network is acting to shift the mind from a state characterized by neural synchronization at high amplitude
of wandering to a state of present-centered awareness during frequencies was found to be proportional to the size of
meditation. the neural assembly being stimulated. The goal of medita-
The AI has also been described as a “hub” for auto- tion is to transform normative functioning into a consistent
nomic, affective, and cognitive integration, as it has been meditative state by disintegrating the distinction between
shown to integrate a wide array of stimuli, including cogni- meditation and normative functioning over time—which
tive, socio-emotional, olfactory-gustatory, interoceptive sen- is reported to occur naturally with consistent practice.8,48,49
sation, and pain processing.52,58–61 Meditators learn to In support of this claim, Lutz and colleagues63 found differ-
master their faculties of introspective awareness, emotional ences in basal gamma activity between novice and expert
control, and self-regulation, as well as techniques oriented meditators before meditation, with expert meditators show-
toward enhancing wholesome and unconditional mental ing more gamma activity during resting state. Further testing
states.52 Therefore, the AI may be a contributing neural found that the duration of time spent meditating over the
correlate of a fundamental, all-inclusive awareness that acts lifespan, and not age, predicted differences in gamma activ-
to shift the mind from a state of self-referential perception of ity during baseline cognitive functioning.63
sensation (i.e., identification with sensation) to a state of all- A recent neurophysiology study investigated the effects
inclusive, present-centered awareness with regard to any of attentional training on the global precedence effect (i.e.,
possible sensation. This category includes all body sensa- the faster detection of targets on a global, rather than on
tion, thoughts, beliefs, emotional states—everything that a local, level) in eight highly trained Buddhist monks and
can be observed, which is literally everything but awareness nuns and in eight age- and education-matched controls with
itself. Therefore, the salience network may act as the bridge no previous meditation experience.68 Analysis of reaction
between the subconscious reactive experience of being iden- times showed a significantly reduced global precedence ef-
tified with sensation, associated with default mode network fect in meditators but not in controls, implying that the
activation, and an all-inclusive, “transcendent” state of ob- meditators had a unique ability to willingly, quickly, and ef-
jective, present-centered awareness of sensate experience, fectively disengage their attention from the dominant global
contributing to a sense of “oneness” or interconnectedness level.68 Analysis of event-related potentials revealed that,
that is associated with central executive network activation. due to an enhanced processing of target-level information,
the meditators had an acute ability to select the respective
Electroencephalography Studies target level in which the target number was embedded.68
EEG coherence is characterized by the synchronous firing Moreover, meditators selected target-level information ear-
of neural networks at a particular frequency. It is theorized lier in the processing sequence than controls. These results
that the amplitude of a brain wave is positively correlated suggest that with mental training, meditators are able to in-
with the degree of precision with which cells oscillate and crease the speed and accuracy with which they allocate atten-
the size of the neural population through which the wave tional resources, thereby increasing the depth and breadth of
is occurring.62,63 It has been found that increases in EEG information processing while reducing response latency to
coherence correlate with increased brain processing capacity stimuli.68
in areas such as attention, working memory, learning, and As described by the methodology involved in concentra-
conscious perception.63–66 Synchronization of oscillatory neu- tive and diffuse meditation, these findings support the no-
ral discharges, particularly of the gamma-band frequency tion that concentrative and diffuse meditation practices
(25–70 Hz), appears to play a key role in developing the result in an increased capacity to process sensory informa-
ability to integrate distributed neural processes into one over- tion by training the practitioner to not “get stuck” on spe-
arching network with highly ordered cognitive and affective cific stimuli, possibly contributing to the ability to notice
functions, suggesting that gamma synchrony may also play fine details more quickly and accurately. To reiterate, con-
a crucial role in neuroplasticity.63 centrative meditators center their attention on a specific ob-
In an EEG study, long-term Buddhist meditators were ject of focus for extended periods of time, and when their
found to possess the ability to induce high-amplitude gamma attention is diverted from the object of focus, they learn
synchrony during meditation, where robust gamma-band to disengage quickly from the distractor and to reengage
oscillations and long-range phase synchrony were found with the object of focus until access concentration is estab-
during a nonreferential compassion meditation state.63 The lished. A similar process may be used to establish access con-
amplitude of activity in some of these practitioners was centration during diffuse meditation, though instead of
found to be the highest reported outside of pathological maintaining attentional focus on a specific object, the medi-
contexts.63,67 This finding suggests that massive distributed tator practices continually disengaging from sense objects
neural assemblies were oscillating with high temporal preci- throughout the body/mind as quickly as possible until a con-
sion during meditation.63 In expert meditators, the transition tinual awareness of the ongoing stream of experience is
from basal cognition to the meditation state typically took established. The above results also support the traditional
5–15 seconds. Time to develop deep meditative states notion that meditation “concentrates” the mind—that is,
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makes the mind progressively more acutely aware of the acts as an effective “psychobiomarker” in predicting physi-
details of momentary experience. cal health and longevity by linking stress and disease.70,74–76
Recent longitudinal studies indicate that telomere length
Physiological Studies in peripheral blood mononuclear cells can increase over time,
It has been known that regular meditation practice can re- suggesting that there may be determinable mechanisms—and
duce psychological stress and enhance perceived well- therefore possible interventions—that regulate the rate of
being.8,9,48,49,69 Some attention has been given to the telomere length alteration.70,77–79 Greater perceived stress,
physiological correlates of meditation-derived health bene- negative affect, and stress-related cardiovascular risk are
fits as a means to understanding the mechanistic links be- factors associated with lower telomerase activity that is re-
tween psychological functioning and physical health. An sponsible for protecting against telomere shortening.70,80,81
early physiology study compared the effect of Buddhist Individuals who respond with suppressed vagal tone when
meditation on several physiological markers (serum corti- presented with an acute stressor and who show correspond-
sol, total protein levels, blood pressure, pulse rate, lung vol- ingly increased measures of negative affect and vulnerability
ume, and reaction time) between 52 male meditators and to psychological stressors show reduced telomerase activ-
30 age- and sex-matched nonmeditators.4 Measurements ity.70,82,83 Therefore, telomerase activity may play a key role
of these markers were taken after three and six weeks of in mediating the relation between psychological stress and
practice. At three weeks, results showed significant reduc- disease.70 This controlled, longitudinal study by Jacobs
tions in serum cortisol level, blood pressure, pulse rate, and colleagues70 investigated the effects of a three-month
and reaction time in meditators compared to controls.4 Vi- meditation retreat on telomerase activity and on two ma-
tal lung capacity, tidal volume, and maximal voluntary jor contributors to the experience of stress—perceived con-
ventilation were significantly lower following each medita- trol (associated with decreased stress) and neuroticism
tion session than before, indicating a lower need for oxy- (associated with increased subjective stress). Perceived con-
gen as a result of meditation.4 In addition, the serum total trol is a marker of stress resilience and refers to a feeling
protein level significantly increased by the six-week time of adequate control that has been associated with reduced
point. Meditators also showed a 23% reduction in reaction psychological stress and more adaptive responses to stress-
time compared to measurements taken before practice, sug- ful events.70,84–89 For example, an internal locus of control
gesting that a high degree of present-centered attentional refers to the extent to which individuals believe they can
acuity was developed during practice.4 The control group control their external circumstance and has been shown
showed a 7% reduction in reaction time at six weeks, most to mediate responses to stressful events by improving cop-
likely due to task repetition, indicating that meditation ing strategies90,91 and reducing anxiety.70,92 High trait neg-
practice was not entirely responsible for the reduced reac- ative affectivity, or neuroticism, refers to chronic feelings of
tion time in the experimental group. These results are con- tension, anxiety, lability, or insecurity, and typically ampli-
sistent with the current conception of meditation as being fies the stress response to acute stressors, causing “greater
associated with a concurrent state of heightened vigilant stress vulnerability.”70,93–96
awareness and reduced metabolic activity that elicits im- The study by Jacobs and colleagues70 also examined the
proved physical health, psychological balance, and emo- causal relationship between meaning-finding and affect,
tional stability.3,6,15,49 with specific regard to how these factors are influenced by
A recent study investigated whether meditation practice meditation. Longitudinal studies have shown that the abil-
is associated with telomerase activity and whether this asso- ity to integrate stressful events into an encompassing sense
ciation is at least partly explained by changes in two major of meaning or purpose leads to a change in affect.70,97 In
contributors to the experience of stress—“perceived control” the context of meditation, Fredrickson and colleagues98
and “neuroticism.”70 Telomeres are terminal DNA protein showed that the amount of time per week spent in “loving-
complexes consisting of repetitive nucleotide sequences that kindness,” or compassion, meditation over a two-month
are located at the ends of chromosomes.71 They are known period predicted a cumulative increase in positive affect,
to ensure genomic stability during cellular replication by pro- contributing to an increase in life satisfaction and reduced
tecting the ends of chromosomes from deterioration and from depressive symptoms as mediated by one’s degree of per-
fusing with other chromosomes. However, telomeres shorten ceived purpose in life and mindfulness. Jacobs and collea-
under conditions of oxidative stress, as well as with each gues70 found that telomerase activity was significantly
cell-division cycle. Telomerase is a ribonucleoprotein that greater in retreat participants than in controls at the end
counteracts this process by adding DNA to the 3’ end in of the retreat (p < 0.05). Moreover, increases in perceived
the telomere regions.71 As cells divide during the aging pro- control, decreases in neuroticism, and increases in both
cess, telomere length steadily decreases and hence is an in- mindfulness and perceived purpose in life were greater in
dicator of the biological age of a cell.70,72 Cell division the retreat group (p < 0.01).70 The data suggest that
can no longer occur below a critical telomere length, result- increases in perceived control and decreases in negative af-
ing in a state of senescence.71,73 Therefore, telomere length fectivity, as influenced by meditation practice, contributed
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to an increase in telomerase activity. If so, consistent medita- change between the beginning and end of individual MBSR
tion could potentially result in increases in telomere length sessions. These results support the view that meditation and
and immune cell longevity throughout the lifespan.70 Hence, meditation-derived therapeutic techniques such as MBSR
the practice of meditation seems to affect cellular processes have beneficial effects on biomarkers of stress regulation,
that are influenced by stress and linked to disease. such as cortical secretion and quality of sleep, and also seem
Another recent study examined the effect of compassion to improve one’s ability to remain mindful. 35 These results
meditation, a form of emotional diffuse meditation, on in- provide support for MBSR as a nonpharmacological inter-
nate immune, neuroendocrine, and behavioral responses to vention alongside standard therapies, as well as in nonclinical
psychological stress, and evaluated the degree to which en- settings to foster well-being. Moreover, the empirical physio-
gagement in meditation practice influenced stress reactiv- logical data summarized from this study support the validity
ity.99 Sixty-one healthy adults were randomized to either of the self-attributed data previously discussed in this section.
six weeks of training in compassion meditation (n = 33) For example, increased perceived control, reduced negative
or participation in a health discussion control group (n = affectivity, and increased life satisfaction scores would be
28). These were followed by exposure to a standardized expected in individuals with improved biomarkers of stress
laboratory stressor (Trier Social Stress Test (TSST)) that regulation.
consists of public speaking followed by mental arithmetic.
Physiologic and behavioral responses to the TSST were de- DISCUSSION
termined by repeated assessments of plasma concentrations Western medical traditions have progressed by way of hy-
of interleukin-6 (IL-6) and cortisol, and by total distress pothetical deduction, relying heavily upon pharmaceuticals
scores on the Profile of Mood States (POMS). Initially, no and technology-based interventions to treat or suppress dis-
differences between groups were found on TSST response eases caused by pathophysiologic processes. While these have
scores for IL-6, cortisol, or POMS scores. However, in- had a substantial impact in improving human health globally,
creased meditation practice as measured by mean number the effectiveness of Western medicine remains limited, espe-
of practice sessions per week was strongly correlated with cially when treating chronic diseases and mental illness in
decreased TSST-induced IL-6 (p = 0.008) and POMS scores which stress and the environment play major roles.101 The
(p = 0.014). Because no differences based on group assign- study and integration of Eastern healing techniques may bring
ment were found (meditation versus controls), further anal- about a complementary approach that will help develop a more
ysis was done to compare individuals who spent more time comprehensive and holistic attitude toward patient care.
meditating (above the median, high practice) to individuals Meditation is an ancient Eastern technique that has re-
who spent less time meditating (below the median, low cently been accepted as a form of clinical intervention in the
practice) and controls (no practice). High-practice indivi- West. The study and practice of Buddhist meditation, along
duals (n = 17) exhibited significantly lower TSST-induced with the increasing use of Buddhist-derived, mindfulness-
IL-6 and POMS scores compared to low-practice indivi- based therapeutic modalities in the clinical setting, have
duals and controls (p = 0.005). These data suggest that en- piqued scientific interest. Here, we have introduced the ba-
gagement in compassion meditation may progressively sic concepts of concentrative, diffuse, and insight medita-
reduce stress-induced immune and behavioral responses tion, as well as some of the relevant clinical applications
relative to one’s degree of experience with meditation.99 and scientific studies that suggest significant physiological
Yet another study examined the effects of mindfulness and neurological correlates of these meditative practices.
on HPA activity and sleep by comparing morning cortisol Neuroscientists have made strides in elucidating some of
samples and also sleep duration and quality between long- the basic biological mechanisms underlying the benefits of
and short-term meditators.100 This study was conducted meditation. Our understanding, however, is rudimentary
with the specific aim of clarifying existing contradictory at this stage.
conclusions from numerous previous studies on the effects Compelling scientific evidence supports the role of med-
of mindfulness on health by investigating the relationship itation in promoting health in general20,21,53,70 and in treat-
between traditional Buddhist meditation, mindfulness-based ing numerous clinical and psychiatric disorders.20–30,36,44,47
stress reduction, HPA activity, and sleep among long-term Buddhist meditation induces what one may consider a low-
practitioners of meditation (Buddhist monks and nuns, and entropy state of equanimous, vigilant awareness,3 bringing
mindfulness teachers) compared to those with no prior med- the body to a “hypometabolic state of parasympathetic dom-
itation experience (novices). Long-term meditators showed inance” that serves to rejuvenate the organism’s capacity for
decreased morning cortisol levels that corresponded with resilience and adaptability.7 Long-term Buddhist medita-
length of practice over the lifespan (p < 0.03). Similarly, tion has been correlated with reduced stress response and
novices who took an eight-week introductory MBSR course lower cortisol levels overall,4,36,70 possibly contributing to
showed reduced morning cortisol levels (p = 0.04) and sub- reduced chronic stress and a restored healthy response to
stantially improved sleep (p = 0.008) and self-attribution of acute stress,4 longevity,70 reduced stress-induced craving,
mindfulness (p = 0.001). However, cortisol levels did not and increased craving tolerance.7 Developed meditators
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