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Brain Plasticity xx (20xx) x–xx
DOI 10.3233/BPL-190084
IOS Press
1
Yoga Effects on Brain Health: A Systematic
Review of the Current Literature
1
2
Neha P. Gothea,∗, Imadh Khana, Jessica Hayesb, Emily Erlenbachaand Jessica S. Damoiseauxb
3
aDepartment of Kinesiology and Community Health, University of Illinois at Urbana Champaign4
bDepartment of Psychology and Institute of Gerontology, Wayne State University5
Abstract. Yoga is the most popular complementary health approach practiced by adults in the United States. It is an ancient
mind and body practice with origins in Indian philosophy.Yoga combines physical postures, rhythmic breathing and meditative
exercise to offer the practitioners a unique holistic mind-body experience. While the health benefits of physical exercise are
well established, in recent years, the active attentional component of breathing and meditation practice has garnered interest
among exercise neuroscientists. As the scientific evidence for the physical and mental health benefits of yoga continues to
grow, this article aims to summarize the current knowledge of yoga practice and its documented positive effects for brain
structure and function, as assessed with MRI, fMRI, and SPECT. We reviewed 11 studies examining the effects of yoga
practice on the brain structures, function and cerebral blood flow. Collectively, the studies demonstrate a positive effect of
yoga practice on the structure and/or function of the hippocampus, amygdala, prefrontal cortex, cingulate cortex and brain
networks including the default mode network (DMN). The studies offer promising early evidencethat behavioral interventions
like yoga may hold promise to mitigate age-related and neurodegenerative declines as many of the regions identified are
known to demonstrate significant age-related atrophy.
6
7
8
9
10
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12
13
14
15
16
17
Keywords: Cognition, brain, yoga review
18
INTRODUCTION
19
The practice of yoga dates back over 2000 years to20
ancient India, with a focus on the unification of the21
mind, body, and spirit through the practice of phys-22
ical movements, meditation and breathing exercises.
23
Over the course of its lengthy existence, many dif-
24
ferent schools of yoga have emerged, each placing a
25
different emphasis on the practice. However, despite
26
their different philosophies and combinations of exer-
27
cises, they all are integrated in the common theme
28
of uniting the mind and body. Yoga’s prominence in
29
western civilization emerged in the late 20th century.30
Although a review of the PubMed search on yoga31
yields the earliest scientific studies dating to 1948,
∗Correspondence to: Dr. Neha P. Gothe, Kinesiology and
Community Health, University of Illinois at Urbana Cham-
paign, Urbana, IL – 61801. Tel.: +1 217 300 6183; E-mail:
npg@illinois.edu.
there has been an exponential increase in publica- 32
tions beginning in the 2000s (see Fig. 1). While its 33
origins root from religious principles, modern day 34
culture is primarily drawn to it for its relaxation 35
benefits (meditation and breathing exercises) and 36
stretching and strengthening movements (physical 37
poses). According to the National Center for Comple- 38
mentary and Integrative Health (NCCIH), yoga is the 39
most popular form of complementary therapy prac- 40
ticed by more than 13 million adults, with 58% of 41
adults citing maintenance of health and well-being 42
as their reason for practice [1]. One of the reasons 43
for yoga’s increase in popularity is its versatility, in 44
that it can be taught at a range of different intensi- 45
ties. A systematic review by Larson-Meyer examined 46
[2] the metabolic energy expenditure during Hatha 47
yoga, the most widely practiced style of yoga in the 48
United States. The review found that, while some spe- 49
cific yoga poses can be metabolically exerting (with 50
energy expenditures >3 METS), most yoga practices 51
ISSN 2213-6304/19/$35.00 © 2019 – IOS Press and the authors. All rights reserved
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2N.P. Gothe et al. / Yoga Effects on Brain Health
Fig. 1. Search results from PubMed featuring the term “yoga” in
the title and/or abstract of publications over the years shows an
exponential growth in yoga research beginning in the 2000s.
fall under the American College of Sport Medicine’s52
criteria of “light-intensity physical activity” (2–2.9
53
METS) [3]. Compared to traditional forms of aero-54
bic and anaerobic exercise, the relatively low-impact,
55
modifiable nature of yoga can offer a middle ground
56
for individuals with movement limitations, clinical57
diagnoses, and is particularly suitable for aging pop-58
ulations. Yoga’s focus on improving the self through
59
both physical and mental practices incorporates more60
mindful elements absent in traditional forms of exer-61
cise.
62
Indeed, the practice of engaging the mind and body
63
through meditation, breathing and physical poses has64
attracted significant attention from the medical com-65
munity, and yoga has been frequently studied for its
66
possible beneficial effects on physical and mental67
health outcomes. Systemic and meta-analytic reviews
68
of randomized control trials have found positive69
associations between yoga practice and improve-70
ments in diabetes [4, 5], cardiovascular function [6],
71
and musculoskeletal conditions [2, 3]. There is also72
considerable evidence for the beneficial effects of
73
yoga practice on mental health including anxiety [9],74
stress [10, 11] depression [12, 13] and overall men-75
tal health [14]. Typically, yoga has been studied as76
an adjunct therapy in these studies conducted with77
adults and older adults often with clinical diagnoses.78
For example, Lin and colleagues [15] conducted a79
meta-analysis assessing the effects of yoga on psy-
80
chological health, quality of life, and physical health
81
of patients with cancer. They concluded that the yoga
82
groups showed significantly greater improvements in
83
psychological health, as indicated by anxiety, depres-
84
sion, distress, and stress levels, when compared with85
the waitlist or supportive groups.86
Yoga’s acute and intervention effects on cogni-87
tion are evident in a recent meta-analysis [16] which88
reported moderate effect sizes for attention, pro- 89
cessing speed and executive function measures for 90
studies conducted with adult populations. Yoga prac- 91
tice enables the practitioner to move in a controlled 92
manner into modifiable physical postures concen- 93
trating initially on relaxing their body, breathing 94
rhythmically, and developing awareness of the sen- 95
sations in their body and thoughts in their mind. In 96
addition to the physical benefits from sequentially 97
completing the postures, the breathing (pranayama)98
and meditation exercises included in yoga are prac- 99
ticed to calm and focus the mind and develop 100
greater self-awareness [17]. It is hypothesized that 101
this combination of metacognitive thought and bodily 102
proprioception during yoga practice could general- 103
ize to conventionally assessed cognitive functions 104
including attention, memory, and higher-order exec- 105
utive functions. However, it is currently unknown if 106
this relationship exists as a direct pathway, or if yoga 107
indirectly influences cognitive functions through pro- 108
cesses such as affective regulation. Negative affect 109
including depression and stress are known to detri- 110
mentally impact both cognitive functioning [18] and 111
brain structure [19] and systematic reviews discussed 112
earlier have demonstrated the potential of yoga to 113
improve anxiety, depression, stress and overall men- 114
tal health. 115
Yoga has particularly gained traction as a research 116
area of interest in its promising potential as a therapy 117
to combat the alarming increase in age-related neu- 118
rodegenerative diseases. Older adults are the fastest 119
growing population in the US and around the world 120
with over 2 billion people expected to be ≥60 years 121
of age by 2050 [20]. Age is the biggest risk factor 122
for Alzheimer’s disease, the most common cause of 123
dementia in those aged 65 and older. In the absence of 124
any effective treatments to cure the disease or manage 125
its symptoms, researchers have explored the poten- 126
tial of modifying lifestyle behaviors such as nutrition 127
and physical activity to drive beneficial plasticity of 128
the aging brain and remediate age-related cognitive 129
decline. Yoga may be an alternative form of physical 130
activity which may help not only older adults achieve 131
recommended levels of physical activity, but also for 132
individuals who have disabilities or symptoms that 133
prevent them from performing more vigorous forms 134
of exercise. 135
The purpose of this review was to synthesize the 136
current evidence for yoga’s effect on brain structure 137
and function among adults and identify the regions 138
and neural networks impacted by its short-term or 139
long-term practice. 140
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N.P. Gothe et al. / Yoga Effects on Brain Health 3
METHODS141
Literature search and study selection142
The aim of this review was to examine the role143
of ‘holistic’ yoga practice, i.e. studies that explored
144
the role of yoga practice which included each of its
145
three elements: yoga postures, yoga-based breath-146
ing exercise and yoga-based meditative exercises. We147
used the following databases to identify studies from148
inception to July 2019 that have examined effects149
of yoga on brain health: MEDLINE, PsychINFO,150
PubMed, Indian Council of Medical Research, and151
Cochrane. We used the following a priori search terms152
to identify all the relevant published articles: ‘yoga’,153
‘hatha yoga’ and ‘brain health’, ‘brain function’,154
‘MRI’, ‘fMRI’, ‘brain volume’ ‘SPECT’, ‘PET’. Ref-
155
erence lists of relevant articles were also scanned to156
locate other published works.157
Study inclusion criteria were peer reviewed and
158
published cross-sectional, longitudinal or interven-
159
tion studies examining the role of holistic yoga160
practice that included physical postures, breathing
161
and meditation. Study outcomes needed to include162
brain health measures assessed using magnetic res-163
onance imaging (MRI), including functional MRI164
(fMRI) or single photon emission computed tomogra-
165
phy scan (SPECT) or position emission tomography166
(PET). Figure 2 presents the PRISMA flowchart167
that summarizes the study selection process. Studies
168
examining the sole effects of meditation or mind-169
fulness were excluded as they have been reviewed170
elsewhere (21, 22) and do not meet the holistic defi-171
nition of yoga practice. After screening for inclusion
172
criteria, 11 studies were included in this review. These
173
studies were categorized based on the outcome vari-
174
ables measured, into two groups: “Effects of Yoga
175
Practice on Brain Structure” that describes the struc-
176
tural characteristics of the brain associated with yoga
177
practice, and “Effects of Yoga Practice on Brain Func-
178
tion” that describes investigations of regions showing179
differential activation or connectivity in the context180
of yoga practice.181
RESULTS182
Study characteristics183
As seen in Table 1, this literature is very nascent, as184
evident from our literature search returning 11 rele-185
vant studies published between 2009 and 2019. Most
186
of the studies (n= 6) were cross-sectional and there-187
Fig. 2. Prisma flowchart.
fore exploratory in nature, whereas 5 intervention 188
studies examined the yoga-brain outcome relation- 189
ships over study durations ranging between 10 and 190
24 weeks. All studies have been conducted with adult 191
populations, with 5 studies having a mean age greater 192
than 65 years, suggesting older adult samples. 193
Various styles of yoga were reported across the 194
studies, with a majority (n= 9) classified as Hatha 195
yoga practice (a style that focuses on physical pos- 196
tures, breathing, and meditation). Other styles of 197
yoga reported in the studies included Kundalini yoga 198
with Kirtan Kriya (n= 2), which focuses more on 199
mediation and the chanting of mantras, and Iyengar 200
(n= 1) which is a type of Hatha yoga with a greater 201
emphasis on anatomical detail and alignment. The 202
5 intervention studies ranged from 10 to 24 weeks 203
and examined the brain health outcomes at baseline 204
and end of the intervention. The frequency of yoga 205
practice varied across the interventions ranging from 206
once a week to biweekly to daily practice. Studies that 207
compared brain health outcomes for yoga practition- 208
ers or experts with age- and or sex-matched controls 209
typically included yoga practitioners with at least 3 210
or more years of regular (weekly or biweekly) yoga 211
practice. None of these cross-sectional studies offered 212
a standardized definition or specific criterion to define 213
a yoga practitioner. Based on the studies included in 214
this review, a yoga practitioner was defined as an indi- 215
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4N.P. Gothe et al. / Yoga Effects on Brain Health
Table 1
Study characteristics of the 11 publications examining the role of yoga on brain structures and functioning
Study author Sample size; Style of Yoga Study design Categorization Imaging Study findings
(Year) characteristics; of Yoga methodology
Mean Age; Group/practitioner
Male:Female and controls
Santaella (2019) N = 40; healthy
female older
adults – 20 yoga
practitioners
and 20 controls;
67.35 years;
0:40
Hatha Cross-sectional 8+ years of at least
bi-weekly Hatha
yoga practice
vs. no yoga or
mindfulness
experience
Resting-state
fMRI
Greater resting-state
anteroposterior
functional
connectivity
between the medial
prefrontal cortex
(MPFC) and right
angular gyrus
among yoga experts
Garner (2019) N = 102; healthy
young adults-
39 randomized
to yoga, 32 to a
sport control
group, and 31 to
a passive control
group; 22.8
years; 16 : 86
Hatha Intervention All yoga and sport
control
participants had
not practiced
yoga or similar
mind-body
exercises for at
least 6 months.
MRI Increase in right
hippocampal GM
density among yoga
group.
Gothe (2018) N = 26; healthy
adults – 13 yoga
experts and 13
controls; 35.75
years; 2 : 24
Hatha Cross-sectional 3+ years of
weekly yoga
experience vs.
no yoga or
mind-body
therapy
experience
MRI+
task-based
fMRI
Larger GM volume in
the left
hippocampus
among yoga experts
Lower dorsolateral
prefrontal cortex
(dlPFC) activity
during encoding
phase of working
memory task
among yoga experts
Afonso (2017) N = 42; older
adults – 21
experts and 21
controls; 67.05
years; 0 : 21
Hatha Cross-sectional 8+ years of yoga
experience vs.
no yoga or
mindfulness
experience
MRI Greater cortical
thickness in left
prefrontal lobe
region, including
lateral middle
frontal gyrus,
anterior and dorsal
superior frontal
gyrus among yoga
experts
Yang (2016) N = 25, healthy
older adults
with MCI – 14
randomized to
yogic
meditation and
11 to memory
enhancement
training; 67.4
years; 13 : 12
Kirtan
Kriya+Kundalini
Yoga
Intervention 1-hour/week for
12 weeks + daily
homework
MRI + 1H-
MRS
Decrease in
choline-containing
compounds in
bilateral
hippocampus in the
memory
enhancement
training group
Increased GM volume
in bilateral
hippocampal in the
memory
enhancement
training group
(Continued)
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N.P. Gothe et al. / Yoga Effects on Brain Health 5
Table 1
(Continued)
Study author Sample size; Style of Yoga Study design Categorization Imaging Study findings
(Year) characteristics; of Yoga methodology
Mean Age; Group/practitioner
Male:Female and controls
No significant
changes in yoga
group
Eyre (2016) N = 25; healthy
older adults
with MCI – 14
randomized to
yogic
meditation and
11 to memory
enhancement
training; 67.4
years; 13 : 12
Kirtan
Kriya+Kundalini
Yoga
Intervention 1-hour/week for
12 weeks + daily
homework
Resting-state
fMRI
Improved verbal
memory
performance which
correlated with
changes in
functional
connectivity in the
DMN, significant
clusters included
the ACC, FMC,
PCC, MFG and
LOC among both
groups
Improved verbal
memory
performance
correlated with
increased
connectivity
between the default
mode network and
frontal medial
cortex, pregunal
anterior cingulate
cortex, right middle
frontal cortex,
posterior cingulate
cortex, and left
lateral occipital
cortex
Improved verbal
memory
performance
positively correlated
with increased
connectivity
between language
processing network
and left inferior
frontal gyrus
Improved visuospatial
memory
performance
correlated inversely
with connectivity
between superior
parietal network
and medial parietal
cortex
(Continued)
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6N.P. Gothe et al. / Yoga Effects on Brain Health
Table 1
(Continued)
Study author Sample size; Style of Yoga Study design Categorization Imaging Study findings
(Year) characteristics; of Yoga methodology
Mean Age; Group/practitioner
Male:Female and controls
Villemure (2015) N = 28; healthy
adults – 14 yoga
experts and 14
controls; 36.85
years; 10 : 18
All types (that
integrated
physical
postures, breath
control
exercises and
meditation.)
Cross-sectional No defined
criteria,
open-ended
questions to
determine yoga
expertise
resulting in
average yoga
experience
range of 6–16
years
MRI No correlation
between age and
whole-brain total
GM volume among
yoga experts
(negative
correlation in
controls)
Positive correlation
between years of
yoga practice and
GM volume in left
mid-insula, left
frontal operculum,
left orbitofrontal
cortex and right
middle temporal
gyrus
Positive correlation
between weekly
hours of practice
and GM volume in
right primary
somatosensory
cortex and superior
parietal lobe, left
hippocampus,
midline
precuneus/posterior
cingulate cortices,
and right primary
visual cortex
Postures and
meditation
predicted
hippocampal,
precuneus/PCC and
somatosensory
cortex/superior
parietal lobule
volume
Meditation and
breathing predicted
primary visual
cortex,
precuneus/posterior
cingulate cortex
volume
Hariprasad (2012) N = 7; healthy
older adults; age
range 69–81
years; 4 : 3
Hatha –
Yogasanass,
pranayama, OM
chanting
Intervention 1-hour 5 days a
week for 3
months + 3
months of home
practice
MRI Increased GM volume
in bilateral
hippocampus
(posterior region)
following yoga
intervention
(Continued)
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N.P. Gothe et al. / Yoga Effects on Brain Health 7
Table 1
(Continued)
Study author Sample size; Style of Yoga Study design Categorization Imaging Study findings
(Year) characteristics; of Yoga methodology
Mean Age; Group/practitioner
Male:Female and controls
Froeliger (2012b) N = 14; healthy
adults – 7 yoga
experts and 7
controls; 35.95
years; 2 : 12
Hatha Cross-sectional 3+ years of yoga
experience with
45 + min of
practice 3-4
times per week
vs no yoga or
meditation
experience
MRI Greater GM volume
of frontal, limbic,
temporal, occipital,
and cerebellar
regions among yoga
experts
Fewer self-reported
cognitive failures
among yoga experts
Negative correlation
between cognitive
failures and GM
volume
Positive correlation
between years of
yoga experience
and GM volume
Froeliger (2012a) N = 14; healthy
adults – 7 yoga
experts and 7
controls; 35.95
years; 2 : 12
Hatha Cross-sectional 3+ years of yoga
experience with
45 + min of
practice 3-4
times per week
vs no yoga or
meditation
experience
Task-based
fMRI
Lower right dorsal
lateral prefrontal
cortex (i.e. MFG)
activity during
viewing of negative
and neutral
emotional images
among yoga experts
Greater left superior
frontal gyrus
activity during
Stroop task among
controls
Greater left
ventrolateral
prefrontal cortex
activity during
Stroop task with
presence of negative
emotional
distractors than
neutral emotional
distractors in yoga
experts (opposite
pattern for controls)
No correlation
between amygdala
activation to
viewing negative
emotional image
and task-related
changes in affect
among yoga experts
(decreases in
positive affect were
correlated with
increased amygdala
activation in
controls).
(Continued)
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Table 1
(Continued)
Study author Sample size; Style of Yoga Study design Categorization Imaging Study findings
(Year) characteristics; of Yoga methodology
Mean Age; Group/practitioner
Male:Female and controls
Cohen (2009) N = 4; healthy
older adults
with
prehypertension
or stage 1
hypertension;
45 years; 2 : 2
Hatha – Iyengar Intervention 1-hour bi-weekly
practice for 6
weeks + 1-hour
weekly practice
and home DVD
(average 20 min
daily practice
reported) for 6
weeks
Injection of
Tc-
bicisate + single
proton
emission
computed
tomography
Decrease in average
cerebral blood flow
ratio in right
amygdala, right
dorsal medial
cortex, and right
sensorimotor area
during baseline
scan following yoga
intervention
Increased activation in
right dorsal medial
frontal lobe, left
dorsal medial
frontal lobe, right
prefrontal cortex,
right sensorimotor
cortex, right inferior
frontal lobe, and
right superior
frontal lobe during
meditation
following yoga
intervention
Greater activity in the
left side of anterior
cingulate,
dorsomedial frontal
cortex, superior
temporal lobe
relative to the right
following yoga
intervention
Greater laterality
preference for the
left over the right
hemisphere during
meditation
compared to
baseline following
yoga intervention
vidual who had consistently practiced yoga for at least216
3 years on a weekly basis.217
Effects of yoga practice on brain structure218
In order to identify the effects of yoga practice219
on brain structure, researchers have utilized MRI220
to investigate how the structure of the brain differs221
among those with experience practicing yoga (see222
Fig. 3).
Cross-sectional studies examining group 223
differences 224
The majority of these studies have relied on 225
comparing the brain structure of experienced yoga 226
practitioners, with the brain structure of non- 227
practitioners, or yoga-na¨
ıve controls, to detect 228
cross-sectional differences existing between the 229
groups. Afonso et al. [23] found differences in cor- 230
tical thickness among female adults over the age of 231
60 with 8 or more years of Hatha yoga experience 232
compared to a non-practitioner control group. The 233
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N.P. Gothe et al. / Yoga Effects on Brain Health 9
Fig. 3. Brain regions showing A) structural differences in yoga-practitioners compared to non-practitioners or B) a dose-dependent rela-
tionship between years of yoga practice and brain structure among practitioners. Yoga practitioners exhibited greater cortical thickness,
gray matter (GM) volume, and GM density than non-practitioners in a variety of regions. Among yoga-practitioners, a positive relationship
between the years of yoga practice and GM volume was also observed in a number of areas. All but one of the regions shown were created
by making a 5 mm sphere around the coordinates provided in the studies reviewed. Since Gothe et al. (2018) did not investigate volume
differences on a voxel-wise basis, a mask of the whole structure is shown.
yoga-practitioners exhibited greater cortical thick-234
ness in an area of the left prefrontal cortex that235
included part of the middle frontal and superior236
frontal gyri. Importantly, participants between groups
237
were matched for the typical amount of non-yoga
238
physical activity they engage in, suggesting that the239
differences in cortical thickness are not just due to a240
potentially greater levels of overall physical activity241
among yoga-practitioners.242
Other studies that investigated cross-sectional
243
differences in brain structure between yoga-244
practitioners and non-practitioners primarily focused245
on detecting differences in gray matter (GM) vol-
246
ume rather than cortical thickness. Our own work247
[24] sought to determine whether the volume of the248
hippocampus, a subcortical structure that plays an
249
important role in memory, differed between yoga-250
practitioners with at least 3 years of experience251
compared to non-practitioners. We found the volume252
of the left hippocampus to be significantly greater253
among yoga-practitioners compared to age- and sex-254
matched controls with similar physical activity and
255
fitness levels. We also tested differences between
256
the thalamus and caudate nucleus, which are sub-
257
cortical structures that served as control regions. No
258
significant differences were found between the two
259
groups, suggesting that yoga effects on the brain260
may be selective and similar to those observed in the261
aerobic exercise-cognition literature. Consistent with262
this result, another study [25] also identified volume263
differences in the left hippocampus and parahip- 264
pocampal gyrus between healthy adults with and 265
without yoga experience. A number of additional 266
frontal (bilateral orbital frontal, right middle frontal, 267
and left precentral gyri), temporal (left superior tem- 268
poral gyrus), limbic (left parahippocampal gyrus, 269
hippocampus, and insula), occipital (right lingual 270
gyrus), and cerebellar regions were also larger among 271
yoga-practitioners than non-practitioners. Given that 272
this sample of yoga-practitioners reported fewer cog- 273
nitive failures than their yoga-na¨
ıve counterparts, the 274
researchers correlated the number of lapses in cog- 275
nitive function that participants reported with the 276
volume of regions where group differences were 277
observed. A negative correlation was reported, such 278
that higher numbers of cognitive failures were associ- 279
ated with smaller GM volumes in the frontal, limbic 280
temporal, occipital, and cerebellar regions stated 281
above. 282
Villemure and colleagues [26] investigated 283
whether the correlation of age with total GM volume 284
of the whole brain differed between a group of yoga- 285
practitioners and non-practitioners. While within the 286
group of healthy adults without yoga experience, a 287
negative correlation was observed between age and 288
the total GM volume of the brain, no relationship 289
was found between age and brain structure within the 290
group of yoga-practitioners. However, the difference 291
in slopes between the groups was not statistically 292
significant. Non-practitioners did not exhibit larger 293
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10 N.P. Gothe et al. / Yoga Effects on Brain Health
or thicker brain structures compared to experienced294
yoga-practitioners in any of these studies.
295
Intervention studies examining yoga training296
effects297
In comparison to the aforementioned cross-
298
sectional studies, studies employing yoga interven-
299
tions have investigated how the structure of the brain
300
changes as a result of relatively short-term yoga
301
practice. Hariprasad and colleagues [27] measured302
changes in the GM volume of the bilateral hippocam-303
pus and the superior occipital gyrus, which served as304
a control region, following a 6-month yoga interven-
305
tion. Participants consisted of healthy older adults306
who underwent an hour of formal training 5 days
307
a week for 3 months and then completed the same
308
daily regimen at home for an additional 3 months
309
with regular booster training sessions. An increase310
in the volume of the bilateral hippocampus from pre-311
to post-intervention was observed; however, the sam-
312
ple of this study was quite small (n= 7) and did not313
compare these changes to changes in hippocampal
314
volume of a control group. Another study [28] also315
evaluated changes in the GM volume of the bilat-
316
eral hippocampus, as well as in the dorsal anterior317
cingulate cortex, but they did so in participants with318
mild cognitive impairment who completed a 12-week319
intervention consisting of weekly 1-hour sessions of
320
either Kundalini yoga with Kirtan Kriya or memory-
321
enhancement training. Both groups also completed
322
12 minutes of daily homework that was related to323
their intervention. Unlike previous studies, the results
324
of a mixed effects model showed the volume change
325
of the bilateral hippocampus did not differ between326
the two groups, but that the change in volume of327
the dorsal anterior cingulate cortex was different328
for the two intervention groups. Within the mem-
329
ory enhancement group, there was a trend toward
330
increased volume of the dorsal anterior cingulate cor-331
tex following the intervention, a change that was not
332
observed within the yoga group. It is possible that333
the shorter length of this intervention (12-weeks)
334
in comparison to the 6-month intervention utilized335
by Hariprasad and colleagues [27] explains the dif-336
ferences in study results pertaining to hippocampal337
volume. However, since memory-enhancement train-338
ing targets a single aspect of cognition and thus is339
likely to directly target areas involved in memory, it340
may not serve as an equal comparison group for yoga,
341
whose effects are exerted in a more indirect fashion.
342
Garner and colleagues [29] investigated the impact
343
of yoga training on GM density, which is related to a
344
voxel’s signal intensity and is reflective of the amount 345
of gray matter within each voxel. They did this by 346
comparing changes in GM density among healthy 347
young adults after a 10-week intervention in which 348
participants self-selected enrollment in a Hatha yoga, 349
sport control, or passive control group. Although 350
the yoga and sport control groups both underwent 351
10 hours of weekly practice which involved simi- 352
lar body movements, the meditation and breathing 353
components of holistic yoga practice were not incor- 354
porated into the workouts performed by the sport 355
control group. Unlike participants in these groups, 356
who had not participated in their selected activities for 357
at least 6 months prior to the intervention, participants 358
in the passive control group did not alter any of their 359
daily habits. No differences were observed between 360
the yoga and passive control groups, but compared 361
to the sport group, GM density of the yoga group 362
was shown to increase in five regions and decrease in 363
three regions following intervention. The only region 364
to show an effect specific to the yoga intervention 365
was the right hippocampus, which showed increased 366
GM density over time within the yoga group and 367
decreased GM density over time within the sport 368
control group. Interestingly, this region showed sig- 369
nificantly lower GM density at baseline for the yoga 370
group compared to the two control groups. Neither 371
gender or height differences were found to explain 372
this, and no other sociodemographic characteristics 373
were found to differ between the groups, but based 374
on known links between the hippocampus, stress, and 375
blood pressure, the authors suggest that individuals 376
who are vulnerable to stress may have been driven to 377
select yoga due to its known relaxation benefits. 378
Dose-response relationships 379
The second general strategy employed by 380
researchers to investigate the effects of yoga prac- 381
tice on brain structure is to characterize the specific 382
nature of the relationship between yoga practice and 383
brain structure among experienced yoga practition- 384
ers. Such analyses primarily consist of examining 385
the “dose-dependent” relationship between years of 386
yoga practice and brain structure (see Fig. 3). How- 387
ever, evaluating how each of the different components 388
of yoga practice (i.e. postures, breathing, medita- 389
tion) is related to the structure of the brain is also 390
of interest. Two of the cross-sectional studies already 391
mentioned (25, 26) investigated relationships of this 392
nature. After identifying regions of the brain in 393
which yoga-practitioners exhibited greater GM vol- 394
ume than non-practitioners, Froeliger and colleagues 395
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N.P. Gothe et al. / Yoga Effects on Brain Health 11
(25) looked within these regions to identify areas396
where years of yoga practice was correlated with GM
397
volume. They found that the extent of yoga experi-398
ence within yoga-practitioners was positively related399
to volume of frontal, limbic, temporal, occipital, and400
cerebellar regions, while no regions showed a nega-
401
tive association between years of yoga practice and402
GM volume.403
Villemure and colleagues [26] also sought to404
identify a dose-dependent relationship between GM
405
volume, years of yoga practice and current weekly406
yoga practice as reported by the yoga-practitioners.407
Volumes of the left mid-insula, frontal operculum,
408
orbital frontal cortex, and right middle temporal gyrus409
were positively correlated with years of yoga prac-
410
tice, while volumes of the left hippocampus, midline411
precuneus/posterior cingulate cortex, right primary412
visual cortex, and right primary somatosensory cor-
413
tex/superior parietal lobe were positively related to414
the weekly number of hours spent practicing yoga.415
In addition to investigating this dose-dependent rela-416
tionship between yoga practice and brain structure,417
the researchers conducted multiple regressions to418
evaluate how well each aspect of yoga practice pre-419
dicted GM volume in the areas found to correlate with
420
weekly yoga practice. Commonality analysis allowed
421
them to divide the amount of variation in GM volume422
that was accounted for by all the predictors into the
423
percentage of the effect unique to each predictor and424
common to each combination of 2 or more predic-425
tors. A combination of the posture and meditation
426
components of yoga practice accounted for 42% of427
the explained variance in hippocampal GM, 41% in
428
precuneus/posterior cingulate cortex GM, and 45%
429
in primary visual cortex GM. Meanwhile, 44% of430
the explained variance in primary somatosensory cor-431
tex/superior parietal lobe GM volume was accounted432
for by the meditation and breathing components of433
yoga practice.434
Effects of yoga practice on brain function
435
Although the majority of studies investigating436
yoga’s relationship with the brain have focused437
on structural brain measures, a handful of studies
438
(n= 5) have compared how brain functioning dif-439
fers between those with and without yoga experience.440
Three of these studies were cross-sectional in nature,441
with two comparing task-related brain activation and442
the other comparing functional brain connectivity443
between experienced yoga-practitioners and non-
444
practitioners.
Task-related fMRI findings 445
Figure 3 represents the brain regions identified 446
across the 3 studies based on the task-related fMRI 447
findings. In addition to investigating differences in 448
GM volume, our own work [24] evaluated how yoga- 449
practitioners and non-practitioners differed in brain 450
function during subcomponents of a Sternberg work- 451
ing memory task. No differences between the groups 452
were identified during the maintenance or retrieval 453
portions of the task, but yoga-practitioners exhibited 454
significantly less brain activation in the left dorso- 455
lateral prefrontal cortex (dlPFC) during encoding 456
compared to yoga-na¨
ıve controls. 457
Froeliger and colleagues [30] used the same 458
sample of yoga practitioners and non-practitioner 459
controls who showed differences in GM volume 460
[25] to investigate differences in task-related acti- 461
vation during an affective Stroop task. One focus 462
of this fMRI study was to evaluate effects of yoga 463
on emotional reactivity by considering the impact 464
of group, the emotional valence of images viewed, 465
and the interaction of group and valence on the 466
BOLD response to viewing emotional images. A 467
significant interaction was noted in the right dor- 468
solateral prefrontal cortex (middle frontal gyrus), 469
and further investigation demonstrated that the per- 470
cent signal change in this region was greater when 471
viewing neutral images compared to negative images 472
among non-practitioners. Meanwhile, among yoga- 473
practitioners, the percent signal change in this region 474
was lesser than that observed in non-practitioners 475
regardless of whether the image had a negative or 476
neutral emotional valence. Across all participants, the 477
percent signal change in the dorsolateral prefrontal 478
cortex was negatively correlated with the percent sig- 479
nal change in the amygdala when viewing negative 480
images, but not when viewing neutral images. The 481
second aim of the study was to identify how yoga 482
experience alters the impact of emotional distrac- 483
tion on the Stroop-BOLD response. To investigate 484
this, the main effects of group, the emotional valence 485
of the distractor image, and the interaction between 486
these on the BOLD response during the Stroop con- 487
trast (incongruent vs congruent number grids) were 488
considered. The non-practitioners showed less acti- 489
vation in the left superior frontal gyrus compared 490
to yoga-practitioners regardless of distractor image’s 491
emotional valence. Furthermore, the percent signal 492
change of the left ventrolateral prefrontal cortex was 493
greater among yoga-practitioners if a negative dis- 494
tractor was presented than if a neutral distractor was 495
presented, while the opposite pattern was observed 496
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12 N.P. Gothe et al. / Yoga Effects on Brain Health
within the group of non-practitioners. Positive affect497
was shown to decrease significantly from baseline to
498
the completion of the affective Stroop task among499
all participants and this change was positively corre-500
lated with the response to viewing negative images501
in the left amygdala. Furthermore, there was a sig-
502
nificant interaction between this response and group,503
such that among non-practitioners a greater response504
to viewing negative emotional images was related to505
greater decreases in positive affect. Among yoga-
506
practitioners, however, this relationship between507
amygdala BOLD response to negative emotional508
images and change in affect was not present.
509
Functional connectivity findings510
Unlike the previous two studies, which utilized511
fMRI to identify brain activation occurring during
512
engagement in a cognitive task, a recent cross-513
sectional study [31] utilized fMRI to identify whether
514
yoga practice is related to functional brain connec-515
tivity. In response to interest surrounding yoga as
516
a tool to combat aging, and the vulnerability of the517
default mode network (DMN) to typical and patho-518
logical aging processes, healthy older adults with at
519
least 8 years of yoga experience were paired with520
age, education, and physical activity-matched yoga-521
na¨
ıve controls. Greater resting-state anteroposterior522
functional brain connectivity between the medial pre-523
frontal cortex and right angular gyrus was observed
524
among yoga practitioners compared to yoga-na¨
ıve525
controls. While a decrease in resting state functional
526
connectivity is often associated with aging, this study
527
suggests that yoga may reverse this age-related effect
528
among older female subjects.529
Other studies investigated longitudinal changes in530
the functional connectivity of the brain function fol-531
lowing yoga intervention. One such study conducted532
by Eyre and colleagues [32] utilized fMRI to exam-
533
ine how the functional connectivity of the brain at534
rest changed following a 12-week intervention with
535
either yoga or memory-enhancement training, as pre-536
viously described in summarizing the results of Yang
537
et al. [28]. Results showed that improvements in ver-538
bal memory recall were positively associated with539
changes in connectivity primarily within areas of540
the default mode network. Specifically, this effect541
was present in the pregenual anterior cingulate cor-542
tex, frontal medial cortex, posterior cingulate cortex,543
middle frontal gyrus, and lateral occipital cortex for
544
both of the intervention groups. Similarly, changes
545
in functional connectivity of the left inferior frontal
546
gyrus, found in the language network, were also
547
positively associated with changes in verbal mem- 548
ory recall for both groups. However, the relationship 549
between changes in connectivity and memory was 550
no longer significant in the posterior cingulate cortex 551
or inferior frontal gyrus within the yoga intervention 552
group after removal of an outlier. While an area within 553
the superior parietal network near the precentral 554
and postcentral gyri exhibited a negative relation- 555
ship between changes in functional connectivity and 556
changes in visuospatial memory, the authors inter- 557
preted this negative association to be reflective of 558
enhanced efficiency following intervention. A 12- 559
week intervention was used in another study [33] 560
to investigate changes in cerebral blood flow (CBF) 561
measured with single-photon emission computed 562
tomography were influenced by Iyengar yoga during 563
baseline and meditation scans among four patients 564
with mild hypertension. The right amygdala, dor- 565
sal medial cortex and sensorimotor areas showed 566
decreases in baseline CBF following the intervention. 567
Meanwhile, activation was greater during meditation 568
in the right prefrontal cortex, sensorimotor cortex, 569
inferior frontal lobe, superior frontal lobe and the 570
right and left dorsal medial frontal lobes following 571
yoga training. Furthermore, the greater activity of 572
the left anterior cingulate, dorsomedial frontal cor- 573
tex, and superior temporal lobe, relative to the right, 574
was more prominent after the intervention. Following 575
yoga training, laterality preference for the left over 576
the right during meditation compared to baseline also 577
became more pronounced. 578
DISCUSSION 579
Our review of the yoga-imaging literature sug- 580
gests that behavioral mind-body interventions such 581
as yoga practice can affect the anatomy of the brain. 582
Yoga practice appears to be linked to anatomical 583
changes in the frontal cortex, hippocampus, ante- 584
rior cingulate cortex and insula. Throughout the 585
studies reviewed, yoga practice showed a consis- 586
tent positive relationship with measures of brain 587
structure (i.e. GM volume, GM density, cortical thick- 588
ness), such that regions showing an effect of yoga 589
practice were greater in experts or had more gain 590
following intervention. Differences in brain function 591
between yoga-practitioners and non-practitioners 592
have been observed in the dorsolateral prefrontal cor- 593
tex, with yoga-practitioners showing less activation 594
during both working memory and affective Stroop 595
tasks. Additionally, yoga-practitioners differed from 596
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N.P. Gothe et al. / Yoga Effects on Brain Health 13
non-practitioners within the ventrolateral prefrontal597
cortex, superior frontal gyrus, and amygdala during
598
other aspects of the affective Stroop task. Studies599
investigating changes in the functional connectivity600
of the brain following yoga practice have primarily601
identified increases in the default mode network, one
602
of which found that those changes were related to603
memory performance.604
Although the direction of differences in brain605
function between yoga-practitioners and non-
606
practitioners may be inconsistent, it is the interpre-607
tation of those differences and what they imply about608
the potential utility of yoga practice in maintain-
609
ing brain health that are of ultimate interest. Given610
the complex nature of the brain, there is often more
611
than one way something can exert an effect. This,612
in addition to the specific task being used, individ-613
ual differences in the way participants strategize, and
614
other differences in study design could account for615
differences in results across studies. While the nature616
of yoga’s relationship with brain function seems less617
straightforward than it does with structure, the evi-618
dence still points toward yoga exerting a beneficial619
effect on brain function. Findings that link the pattern620
of brain functioning observed in yoga-practitioners to
621
performance or health outcomes offer support for the
622
beneficial influence of yoga on brain function.623
Evidence suggests that global GM declines with
624
age [34] while physical activity and cardiovascu-625
lar fitness [35, 36] as well as mindfulness [21, 22]626
have shown to confer neuro-protective effects. The
627
holistic practice of yoga combines physical activity628
in the form of postures with yoga-based meditative
629
and breathing exercises. The findings from studies
630
reviewed in this paper are therefore not surprising631
and suggest that yoga confers similar cortical neuro-632
protective effects. These findings could not only have633
a significant public health impact on cognitive aging634
but also call for exercise neuroscientists to design635
systematic trials to test the efficacy and effective-
636
ness of yoga practice in comparison to other forms637
of physical activity and mindfulness practices.
638
A majority of the studies highlight changes in639
hippocampal volume following yoga practice. The640
hippocampus is known to be critically involved in641
learning and memory processes [37]. Yoga effects642
on the hippocampus are also aligned with findings643
from the aerobic exercise literature [38], as well as the644
mindfulness literature [39], suggesting that exercise
645
alone and mindfulness alone, as well as a combina-
646
tion of the two in the form of yoga practice, have a
647
positive effect on this critical brain structure impli-
648
cated in age-related neurodegenerative diseases and 649
chronic stress [19, 40]. Other than the hippocam- 650
pus, work of Froelinger and colleagues [25] suggests 651
that yoga practitioners have higher GM volume in 652
a number of regions including frontal (i.e., bilateral 653
orbital frontal, right middle frontal, and left precentral 654
gyri) (see Fig. 3), limbic (i.e., left parahippocam- 655
pal gyrus, hippocampus, and insula), temporal (i.e., 656
left superior temporal gyrus), occipital (i.e., right 657
lingual gyrus) and cerebellar regions. Experimental 658
and legion studies indicate these brain structures are 659
involved with tasks of cognitive control [41], inhibi- 660
tion of automatized or prepotent responses [42], the 661
contextually appropriate selection and coordination 662
of actions [43], and reward evaluation and decision 663
making [44, 45]. The cerebellum, a brain structure 664
known for decades as integral to the precise coordi- 665
nation and timing of body movements [46], but more 666
recently has been acknowledged to be involved in 667
cognition, specifically executive function [47, 48]. 668
The studies reviewed also implicate the role of 669
yoga in functioning of the dlPFC and the amygdala 670
(see Fig. 4). Gothe et al. [24] found that yoga prac- 671
titioners demonstrated decreased dlPFC activation 672
during the encoding phase of a working memory task 673
in comparison to the controls. Froelinger et al. [30] 674
also found yoga practitioners to be less reactive in the 675
right dlPFC when viewing the negatively valanced 676
images on the affective Stroop task. Task-relevant 677
Fig. 4. Brain regions showing differential task-related activation
in yoga-practitioners. Yoga practitioners showed less activation
than non-practitioners in the left dorsolateral prefrontal cortex
during the encoding phase of a Sternberg Working Memory task
(yellow). Yoga practitioners also showed less activation than non-
practitioners in the right dorsolateral prefrontal cortex and right
superior frontal gyri, but more activation in the left ventrolateral
prefrontal cortex during various aspects of an Affective Stroop task
(red). All regions shown were created by making a 5 mm sphere
around the coordinates provided in the studies reviewed.
Uncorrected Author Proof
14 N.P. Gothe et al. / Yoga Effects on Brain Health
targets activate the dlPFC, whereas emotional distrac-678
tors activate the amygdala [49]. Exerting cognitive679
control over emotional processes leads to increased
680
activation in the dlPFC, with corresponding recipro-681
cal deactivation in the amygdala [50, 51]. The studies682
suggest that when emotional experience occurred
683
within the context of a demanding task situation,
684
yoga practitioners appeared to resolve emotional
685
interference via recruitment of regions of the cor-
686
tex that subserve cognitive control. Plausibly, these687
findings may indicate that yoga practitioners selec-688
tively recruit neurocognitive resources to disengage689
from negative emotional information processing and
690
engage the cognitive demands presented by working691
memory and inhibitory control tasks demonstrating
692
overall neurocognitive resource efficiency.
693
A network of neural structures including the
694
frontal lobe, the anterior cingulate cortex, the infero-695
temporal lobe and the parietal cortex are known to be696
involved in cognitive operations including stimulus
697
processing and memory updating [52, 53]. Specif-698
ically, the anterior cingulate cortex is part of the
699
brain’s limbic system and has connections with mul-700
tiple brain structures that process sensory, motor,
701
emotional and cognitive information [54]. In our702
reviewed studies, Eyre et al. [32] found verbal mem-703
ory performance to be correlated with increased704
connectivity between the pregenual anterior cingu-
705
late cortex, frontal medial cortex, posterior cingulate
706
cortex, middle frontal gyrus, and lateral occipital cor-
707
tex following a 12-week yoga intervention. Villemure708
et al. [26] also reported a positive correlation between
709
the dose of weekly yoga practice and GM in the cin-
710
gulate cortex. Collectively these results are promising711
and corroborate the aerobic exercise literature, as the712
anterior cingulate cortex is one of the brain struc-713
tures that shows disproportional changes as a result
714
of participation in moderate intensity physical activ-
715
ity [55]. Many of these regions are part of the default716
mode network, which is typically activated during
717
rest and deactivated when an individual is engaged718
in an external task [56]. Following a yoga interven-
719
tion, increases in connectivity of regions in the DMN720
were associated with improvements in verbal mem-721
ory recall [32]. Given that functional connectivity of722
the DMN has been negatively associated with age-723
related pathologies such as Alzheimer’s disease [57],724
as well as in the context of typical aging [58], the725
increases in functional connectivity in regions of the
726
DMN reported by Eyre et al. further indicate that yoga
727
practice is a promising intervention for use among
728
aging populations.
729
Future directions 730
Although yoga-cognition has emerged as a topical 731
area in the field of exercise neuroscience, the studies 732
are preliminary and lack the rigorous methodology 733
that is applied in the exercise-cognition literature. 734
Sample sizes for yoga studies have ranged from 4 735
to 102 participants and a majority of the work has 736
been cross-sectional in nature. While the beauty of 737
yoga lies in the diverse and modifiable combinations 738
of postures, breathing and meditative exercises, this 739
concurrently poses a challenge for scientists to com- 740
pare findings across studies. Furthermore, there is no 741
standardized definition for a yoga practitioner, nor 742
a universal standard for certification. Of the yoga 743
practitioners sampled in the reviewed studies, their 744
experience ranged from regular practice 3–5 days a 745
week for 3 to 16 years. This poses a challenge to 746
compare research findings across studies. 747
Although cross-sectional studies limit us in our 748
ability to draw casual conclusions, such a design 749
can provide certain advantages over the use of inter- 750
ventional studies design in identifying the effects of 751
yoga practice on the brain given that 9.3 years was 752
the lowest average number of years of yoga prac- 753
tice reported by yoga-practitioners in these studies. 754
Following yoga-practitioners for such an extended 755
period in an intervention design would pose a variety 756
of practical difficulties, and thus cross-sectional com- 757
parisons between yoga practitioners and yoga-na¨
ıve 758
controls provide a unique opportunity to gain an idea 759
of the maximal benefits that extensive yoga practice 760
may lead to. Nonetheless, it is the promise of yoga 761
as an intervention for individuals with various health 762
issues that has sparked much of the growing interest 763
in the effects of yoga practice on brain structure and 764
function, since its established cognitive benefits and 765
accessibility to people with a wide range of physical 766
capabilities suggest it may be an effective interven- 767
tion for typical and pathological cognitive decline 768
among older adults. Yet for yoga interventions to 769
have clinical utility in such circumstances, compli- 770
ance to the intervention program is a necessity. None 771
of the reviewed intervention studies provided infor- 772
mation about participants’ compliance and adherence 773
to the yoga program. Future studies need to document 774
and report attendance and adherence rates. The inter- 775
vention studies also employed different frequencies, 776
intensities and doses of yoga practice which resulted 777
in heterogeneity across intervention designs as well. 778
While the reviewed studies examined the relation- 779
ship between yoga and brain structure or function, 780
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N.P. Gothe et al. / Yoga Effects on Brain Health 15
only one [24] employed cognitive or behavioral781
assessments which correlate with the studied brain
782
regions. Future studies should administer such assess-783
ments to establish if the neural changes produced by784
yoga practice are indeed manifested into improved785
cognitive performance and/or behavioral changes.
786
Another limitation among the reviewed studies is787
lack of reported data on the lifestyle characteristics788
of yoga practitioners. A national survey [59] found789
that, compared to the US average, yoga practitioners
790
are more likely to be highly physically active, non-791
obese, and well-educated – each of which [60–62] are792
known to individually contribute to positive changes
793
in brain structure and function. The same survey also794
found that yoga practitioners are almost four times
795
more likely to follow vegetarian or plant-based diets796
compared to the US population which could also con-797
tribute to brain health [63]. Future research should
798
examine how the lifestyle characteristics of yoga799
practitioners may interact with the physical practice800
of yoga and contribute towards brain function and801
structure.802
Unlike intervention studies and randomized trials,803
the design of cross-sectional studies limits the con-804
trol researchers can exert on possible confounding
805
or mediating variables. Most of the cross-sectional
806
studies compare the brains of yoga practitioners807
with several years of experience to age- and sex-
808
matched yoga-na¨
ıve controls. However, only three809
of these studies matched the groups on the levels of810
physical activity between the groups or their cardio-
811
vascular fitness levels. Moving forward, researchers812
should conduct well-powered yoga interventions
813
with appropriate controls to examine the neuroimag-
814
ing outcomes. A variety of cognitive measures and815
neuroimaging analysis techniques have been used816
in the literature. Perhaps a foundation would be to817
test yoga interventions against the established evi-818
dence for aerobic exercise and mindfulness practices.819
Designing randomized controlled trials with exercise
820
and mindfulness comparison groups will allow us to821
further the literature with the goal of identifying the
822
unique and holistic effects of exercise vs. mindfulness823
vs. yoga practice.824
The literature is too nascent, and it would be pre-825
mature to dive into comparisons between different826
styles of yoga practice. This is evident from the827
studies reviewed as none of them compared the effec-828
tiveness of one style of yoga versus another. This
829
question is intertwined with the ‘holistic’ definition
830
of yoga practice as different styles of yoga place
831
greater or lesser emphasis on one or more elements of
832
physical postures, breathing, and meditation. Well- 833
powered randomized control trials are needed not 834
only to identify the ‘active ingredient’ that is driv- 835
ing the yoga effects on brain health, but also examine 836
the synergistic neuro-protective effects of these ele- 837
ments. Lastly, it remains to be determined whether 838
web-based yoga interventions will be as effective as 839
in-person yoga interventions which were primarily 840
utilized in the reviewed papers. There has been an 841
exponential growth in the development of mobile 842
health apps [64] and it remains to be determined 843
whether web-delivered yoga interventions will be as 844
effective as in-person often group based interven- 845
tions. 846
CONCLUSION 847
This review of literature reveals promising early 848
evidence that yoga practice can positively impact 849
brain health. Studies suggest that yoga practice may 850
have an effect on the functional connectivity of 851
the DMN, the activity of the dorsolateral prefrontal 852
cortex while engaged in cognitive tasks, and the 853
structure of the hippocampus and prefrontal cortex- 854
all regions known to show significant age-related 855
changes [65, 66]. Therefore, behavioral interventions 856
like yoga may hold promise to mitigate age-related 857
and neurodegenerative declines. Systematic random- 858
ized trials of yoga and its comparison to other 859
exercise-based interventions, as well as long term 860
longitudinal studies on yoga practitioners are needed 861
to identify the extent and scope of neurobiological 862
changes. We hope this review can offer the prelimi- 863
nary groundwork for researchers to identify key brain 864
networks and regions of interest as we move toward 865
advancing the neuroscience of yoga. 866
Author contributions 867
NG, JD – conceptualization, analyses and writ- 868
ing. JH – structuring and writing results, figures and 869
tables. IK – review of studies, extraction of data and 870
preparation of Table 1. EE – revision and writing of 871
the manuscript. 872
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