Transcript Exercise Enhances Brain Health

Physical Activity Enhances
Brain Function
Cognitive Physiology
In science, cognition refers to mental
processes. These processes include
attention, remembering, producing and
understanding language, solving problems,
and making decisions
Cognitive physiology is the study of the
underlying mechanisms of human thought
Physical Activity and Cognition
Numerous studies have shown that
adequate physical activities improve
cognition in mice (Cotman CW, Berchtold
NC, Christie LA., 2007) and human
(Benjamin A. Sibley, Jennifer L. 2010;
EtnierLautenschlager, Nicola T; Almeida,
Osvaldo, p, 2006)
Hippocampus of Brain
The hippocampus is located in the medial
temporal lobe of the brain.
Lateral view of the human brain, the frontal
lobe is at left, the occipital lobe at right,
and the temporal and parietal lobes have
largely been removed to reveal the
hippocampus underneath
Anatomy of human brain
Structure of Hippocampus
Structure of Hippocampus
The hippocampus is a major component of
the brains of humans and other
vertebrates.
The hippocampus is closely associated
with the cerebral cortex, and in primates is
located in the medial temporal lobe,
underneath the cortical surface. It contains
two main interlocking parts: Ammon's
horn and the dentate gyrus.
Structure of Hippocampus
Function of Hippocampus
It belongs to the limbic system and plays
important roles in the consolidation of
information from short-term memory to
long-term memory and spatial
navigation.
Humans and other mammals have two
hippocampi, one in each side of the brain.
Nerve cells
Basic Structure of a Chemical
Synapse
Neurotransmitters and Synaptic
Transmission
Excitatory postsynaptic potentials (EPSP)
– Causes depolarization
Inhibitory postsynaptic potentials (IPSP)
– Causes hyperpolarization
Neurogenesis
New neurons are continually born throughout
adulthood in predominantly two regions of the
brain:
– The subventricular zone (SVZ) lining the lateral
ventricles, where neural stem cells and progenitor
generate new neurons (Neuroblast) that migrate to
the olfactory bulb via the rostral migratory stream
– The subgranular zone (SGZ), part of the dentate
gyrus of hippocampus.
Many of the newborn cells die shortly after they
are born, but a number of them become
functionally integrated into the surrounding brain
tissue.
BrdU (dyed in red), a
marker of DNA
replication, highlights
neurogenesis in the
subgranular zone of
hippocampal dentate
gyrus. Fragment of an illustration from
Faiz et al., 2005.
Neurogenesis and Cognition
Recent experimental evidence supports the
role of Brain-Derived Neurotrophic Factor
(BDNF) in memory processes
Memory acquisition and consolidation are
associated with an increase in BDNF mRNA
expression and the activation of its receptor:
neurotrophic tyrosine kinase, receptor, type
2 (TrkB; a protein that is encoded by neurotrophic tyrosine kinase
receptor 2 ( NTRK2) gene has been localized to a region on chromosome
9q22-q23 in humans
)
Yamada K, Nabeshima T. J. Pharmacol. Sci. (2003)
Brain-Derived Neurotrophic Factor
Known as BDNF, is a protein
that, in humans, is encoded
by the BDNF gene.
BDNF is a member of the
"neurotrophin" family
In the brain, it is active in the
hippocampus, cortex, and
basal forebrain—areas vital to
learning, memory, and higher
thinking.
BDNF is important for longterm memory.
Physical Activity and Brain Structure
and Function
Scientists have shown that physical
activity in the form of voluntary exercise
results in an increase in the number of
newborn neurons in the hippocampus of
aging mice. The same study demonstrates
an enhancement in learning of the
"runner" (physically active) mice
Animal model
Results of the study
The results show that cell proliferation was only
increased in mice housed with unrestricted access to a
running wheel (runners).
voluntary physical activity and enrichment roughly doubled
the total number of surviving new-born cells in the dentate
gyrus.
In contrast, mice trained in the water maze and yokedswim controls showed no change the cell number,
suggesting that this type of learning or activity alone is
not an adequate stimulus for adult hippocampal
neurogenesis
What is the implication of this study to you !!
Animal Model (II)
Results of the study
Summary
Mice who exercised performed better on a spatial
learning task (finding their way through a water maze).
Since the late 1990s, research (Cotman and Berchtold
2002 and von Pragg 2008) has revealed that aerobic
exercise boosts levels of brain-derived neurotrophic
factor (BDNF), a substance essential for the growth of
brain cells
Mobilizes the expression of genes that are believed to
enhance brain plasticity—i.e., the ability of the brain to
change its neural pathways
Prevents brain tissue loss in older adults
Compared sedentary mice with mice that ran an
average of 3 miles each night on a running
wheel (van Pragg et al. 1999) the aerobicallychallenged mice showed dramatic brain growth.
And the hippocampus—-a brain region
associated with learning and memory--was twice
as large (van Pragg et al. 1999)
the brain cells of the aerobic mouse could
sustain longer bouts of “long-term potentiation,”
the increased efficiency of communication
between neurons that occurs after neurons fire.
Long-term potentiation (LTP)
Is a long-lasting enhancement in signal
transmission between two neurons that results
from stimulating them synchronously.
It is one of several phenomena underlying
synaptic plasticity, the ability of chemical
synapses to change their strength.
As memories are thought to be encoded by
modification of synaptic strength, LTP is widely
considered one of the major cellular
mechanisms that underlies learning and memory
Long-term potentiation (LTP)
Recordings are made intracellularly from
CA1 neurons of the hippocampus while
stimulation is applied to the Schaffer
collaterals of CA3 neurons.
The amplitudes of the EPSPs in the CA1
neurons are shown in B. For a single
stimulus, the amplitude of the EPSPs is
plotted at 100%. When a train of stimuli
is applied instead, the amplitude of the
EPSPs augment to about 150%,
whereas with 4 such trains the amplitude
increases to 250%.
Many people think that long-term
potentiation is an example of Hebb’s rule
at work and that it is the physiological
basis of memory.
Mechanism of LTP
Glutamine induces N-methylD-aspartate (NMDA)
receptor to depolarize and
remove Mg++ (inhibits Ca++
binding)
Ca++ then binds to NMDA
receptor which increase aamino-3-hydroxy-5-methyl-4isoxa-zolep-propionate
(AMPA) receptor number
AMPA increases potentiated
nerve impulse and generates
LTP in CA1 of hippocampus
Being suggests in associates
with learning and memory
AMPA receptors
AMPA receptors can
move between an
intracellular pool and the
neuronal surface, by the
processes of exocytosis
and endocytosis
AMPA receptors are also
immobilized by increases
in intracellular calcium
levels, perhaps after
calcium influx through
postsynaptic calcium
channels
Running animal and LTP
Glutamate
Neurovascular adaptations to exercise in the dentate
gyrus of young adult mice associated with cognitive
gain
Clark PJ, Brzezinska WJ, Puchalski EK, Krone DA, Rhodes JS.2009
Neurovascular Adaptations
Image shows the high
density of blood
vessels in the brain
and the close
proximity of brain
cells to those vessels.
A cut-away of one
blood vessel shows
vessel lining cells
(endothelia-red).
Physical activity for Body and Brain
Cotman CW, Berchtold NC, Christie LA. (2007)
advocated that exercise increases synaptic
plasticity by directly affecting synaptic structure
and potentiating synaptic strength, and by
strengthening the underlying systems that
support plasticity including neurogenesis,
metabolism and vascular function
In addition, exercise reduces peripheral risk
factors such as diabetes, hypertension and
cardiovascular disease, which converge to
cause brain dysfunction and neurodegeneration.
Human studies (I)
Davis, C. L. (2011a) used sedentary, overweight
7- to 11-year-old children (N = 171, 56% girls,
61% Black, M ± SD age = 9.3 ± 1.0 years, body
mass index [BMI] = 26 ± 4.6 kg/m², BMI z-score
= 2.1 ± 0.4) whom were randomized to 13 ± 1.6
weeks of an exercise program (20 or 40
min/day), or a control condition.
Dose-response benefits of exercise on
executive function and mathematics
achievement.
Physical activity may prove to be a simple,
important method of enhancing aspects of
children's mental functioning that are central to
cognitive development
Human study (II)
Davis, C. L. (2011b) examined effects of
aerobic exercise on overweight children's
cognitive functioning
Ninety-four sedentary, overweight but
otherwise healthy children (mean age = 9.2
years, body mass index 85th percentile) were
randomized to a low-dose (20 min/day
exercise), high-dose (40 min/day exercise),
or control condition.
Exercise sessions met 5 days/week for 15
weeks. The Cognitive Assessment System
(CAS), a standardized test of cognitive
processes, was administered individually
before and following intervention
Cont.
Planning scores for the high-dose group
were significantly greater than those of the
control group.
the effect of exercise seemed to depend
on the dose. Kids enrolled in the 40minute-a-day program made the
biggest improvements – an average
increase of 3.8 points in IQ. Kids in the 20minute-a-day program made smaller gains.
PAAC promoted 90min/week of moderate to vigorous physically active academic lessons(3.0 to 6.0METS,~10 min
each) delivered intermittently throughout the school day. Lessons were usually delivered in the classroom, but were also
delivered in alternate school sites such as hallways and outdoors. PAAC=physical activity across curriculum
Summary
Exercise may prove to be a simple, yet important,
method of enhancing aspects of children's mental
functioning that are central to cognitive and social
development
40 minutes a day of aerobic exercise improved
executive function—-that aspect of intelligence that
helps us pay attention, plan, and resist distractions
(Davis et al 2007).
13 weeks of aerobic exercise was also linked with
improved math skills and increased activity in the
bilateral prefrontal cortex, a brain region associated
with executive function (Davis et al 2011).
Exercise for children is probably beneficial for
the brain. Given that physical fitness is also
good for the body
Exercise should be fun. The mouse experiments
are based on voluntary wheel-running. When
rodents are forced to exercise, they don’t always
reap the benefits
aerobic exercise that your child really enjoys.
Structured activities—-like team sports or dance
lessons—-may be fine options. But so are nature
walks, tree-climbing, roller-skating, and playing
hide-and-seek.
Exercise improves brain function and reduces
the risk of cognitive impairment associated with
aging
Regular exercise can protect the brain against:
– Disease (Alzheimer’s)
– Certain types of brain injury (stroke)
How does exercise enhance brain health?
–
–
–
–
–
Enhances learning and memory
Stimulates formation of new neurons
Improves brain vascular function and blood flow
Attenuates mechanisms driving depression
Reduces peripheral factors for cognitive decline
Inflammation, hypertension, and insulin resistance
Exercise Has Broad Positive
Benefits on Brain Health
Discussion
In your opinion, what is the most effective
physical activity promote brain function for
seniors.
Why the role of Brain-Derived Neurotrophic
Factor (BDNF) is important in memory
processes.
What do you do If you are going to implement
a PAAC program in a junior high school
class and may expect what kind of change as
to brain function of the students.