Lecture_9____Lecture_12_mind%20and%20brain

Lecture_9____Lecture_12_mind%20and%20brain - Midterm :...

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Unformatted text preview: Midterm : Human
Physiology
 Lecture
12


 Mind
and
Brain
 Chapter
8
 
 next week, in class, 8:10-9:30 50 multiple choice questions Consciousness is defined as subjective experience, awareness, the ability to experience "feeling", wakefulness, the understanding of the concept "self", or the executive control system of the mind. Consciousness in medicine (e.g., anesthesiology) is assessed by observing a patient's alertness and responsiveness, and can be seen as a continuum of states ranging from alert, oriented to time and place, and communicative, through disorientation, then delirium, then loss of any meaningful communication, and ending with loss of movement in response to painful stimulation. Consciousness is the subject of much research in philosophy of mind, psychology, neuroscience, cognitive science and artificial intelligence. Issues of practical concern include how the presence of consciousness can be assessed in severely ill or comatose people, whether non-human consciousness exists and if so how it can be measured; at what point in fetal development consciousness begins; and whether computers can achieve a conscious state. 3 Examples
of
Conscious
 experiences
 •  Awareness
of
internal
ideas
and
thoughts
 •  Awareness
of
external
objects
and
their
 location/orientation
with
respect
to
 ourselves
 •  Awareness
of
self
 •  Awareness
of
inner
states
like
happiness

 •  Awareness
of
the
passing
of
time
 •  Awareness
of
past
events
and
 experiences
 4 The
Mind-body
problem:
 What
is
the
nature
of
the
relationship
between
the
 immaterial,
conscious
mind
and
its
physical
basis
 in
the
electro-chemical
interactions
in
the
body?
 Consciousness
poses
fundamental
 problems
for
a
biological
theory
of
the
mind.
 •  Consciousness
is
the
property
of
being
 aware
of
oneself
and
one’s
place
in
the
 world.

 •  Awareness
is
subjective
 •  How
do
objective
phenomena
cause
a
 subjective
experience?
 •  What
are
the
neural
correlates
of
a
 subjective
experience?
 6 5 1 Theory of mind (TOM) The theory that someone else had a mind, juts like you. Theory of mind is the capacity we have to understand mental states such as: believes, feelings, desires, hope and intentions. It’s the way we imagine other people’s feelings or thoughts. TOM enables us to understand the behavior people display is caused by their inner feelings, believes or intensions Whatever goes on in the mind of other people is not visible so it will remain a “theory” we create for ourselves. The development of theory of mind is typically seen in kids over 4 yrs old. The Sally/Anne test About 80% of autistic kids fail the test. 7 8 A
pragmatic
approach
toward
a
 neurobiology
of
consciousness
 •  The
initial
task
is
to
focus
on
the
neural
 correlates
of
consciousness.
 •  Then,
to
develop
laws
of
correlation
 between
neural
phenomena
and
 subjective
experience.
 States
of
Consciousness
 •  Refers
to
whether
a
person
is
awake,
 asleep,
in
a
coma,
etc.
 •  This
state
is
determined
by
observing
a
 person’s
behavior

and
by
measuring
the
 electrical
activity
of
the
brain.

 •  A
recording
of
brain
electrical
activity
is
 called
an
electroencephalogram
(EEG)
 9 10 Arousal
is
often
monitored
using
EEG
 (ElectroEncIephaloGram) EEG
measures
potential
 differences
between

 pairs
of
electrodes
placed
in
 standard
locations
on
the
 scalp. Electrodes pickup electrical signals generated by cortical neurons Transmit them to a machine that records them as the EEG signal. We record waves and can analyze patterns as: Amplitude (mV) High amplitude indicates many neurons activated simultaneously (synchrony) Frequency (Hz=cycle per second) Range = 1 to > 40 Hz EEG
reflects
summated
 activity
of
synaptic
potentials
 in
dendrites
of
cortical
 neurons
 In general - lower frequency indicate less responsive state and higher indicate alertness (except REM) 11 2 VOLTAGE (typically 20-100 microvolts) The
frequency
content
and
amplitude
of
the
 EEG
provide
information
about
brain
activity.
 Four
common
EEG
rhythms
 correlate
with
consciousness
states
 Alpha: 8-13 Hz Beta: 13-30 Hz Theta: 4-7 Hz Delta: 0.5-4 Hz 13 14 conscious
states:
 There is a spectrum between : Arousal rest sleep coma persistent vegetative state brain death The
Waking
State
 Arousal:
increased
wakefulness,
vigilance,
responsiveness
of

 cortical
and
thalamic
neurons
to
sensory
stimuli
 15 16 The
Waking
State
 •  The
most
prominent
EEG
wave
pattern
of
an
 awake,
relaxed
adult
whose
eyes
are
closed,
is
the
 alpha
rhythm.

 •  The
alpha
rhythm
is
recorded
best
over
the
parietal
 and
occipital
lobes
and
is
associated
with
 decreased
levels
of
attention.
When
alpha
rhythms
 are
generated,
subjects
commonly
report
that
they
 feel
relaxed
and
happy.

 •  When
people
are
attentive
to
an
external
stimulus
 or
are
thinking
hard
about
something,
the
alpha
 17 rhythm
is
replaced
by
the
beta
rhythm.
 •  The
EEG
pattern
changes
profoundly
in
sleep.
As
a
 person
becomes
increasingly
drowsy,
their
wave
 pattern
transitions
from
a
beta
rhythm
to
one
that
is
 predominantly
alpha.
 •  When
sleep
actually
occurs,
the
EEG
shifts
toward
 lower-frequency,
higher-amplitude
theta
rhythm
(4–8
 Hz)
and
delta
rhythm
(slower
than
4
Hz).

 •  There
are
two
phases
of
sleep:
NREM
(non-rapid
 eye
movement)
and
REM
(rapid
eye
movement)
 sleep.

 18 Sleep
 3 NREM
Sleep
 VOLTAGE (20 to 100 microvolts) •  During
NREM
sleep
the
EEG
waves
are
referred
to
as
slowwave
sleep.
The
initial
phase
of
sleep—NREM
sleep—is
itself
 divided
into
four
stages:

 In
stage
1
sleep
theta
waves
begin
to
be
interspersed
among
the
 alpha
pattern.


 In
stage
2
sleep
high
frequency
bursts
called
sleep
spindles
 occasionally
interrupt
the
theta
rhythm.

Delta
waves
first
 appear
along
with
the
theta
rhythm.

 In
stage
3
sleep
delta
waves
first
appear
along
with
the
theta
 rhythm.

 In
stage
4
sleep
the
dominant
pattern
is
a
delta
rhythm.


 EEG patterns undergo characteristic shifts in a sleeping person, reflecting the four stages of sleep. The duration of the series is typically ~90 minutes, and the entire pattern cycles 4 to 8 times per night. 19 •  Sleep
begins
with
the
progression
from
stage
1
to
stage
4
of
 NREM
sleep,
which
normally
takes
30
to
45
min.

 20 REM
Sleep
 •  REM
sleep
is
also
called
paradoxical
sleep
because
 the
sleeper
is
difficult
to
arouse,
despite
having
an
 EEG
characteristic
of
the
alert,
awake
state.

 •  Peripheral
measurements
show
increased
eye
 movements
and
heart
rate,
but
suppressed
muscle
 activity.
 •  When
awakened
during
REM
sleep,
subjects
 generally
report
that
they
have
been
dreaming.

 •  If
uninterrupted,
sleep
occurs
in
a
cyclical
fashion,
 tending
to
move
from
NREM
stages
1,
2,
and
3,
to
4,
 then
back
up
from
4
to
3,
2,
and
then
an
episode
of
 REM
sleep.

 21 22 Sleep Four
common
EEG
rhythms
 correlate
with
consciousness
states
 Where is the control located in the brain? The bilateral removal of part of the Thalamus abolish consciousness, causing coma. Alpha: 8-13 Hz (relaxed wakefulness) Beta: 13-30 Hz (intense mental activity) Theta: 4-7 Hz (early slow-wave sleep) Delta: 0.5-4 Hz (stages 3 and 4 of sleep) 23 The same nucleus is also the site of action of general anesthetics and anti-psychotic drugs. This evidence suggests that a functioning thalamus is necessary, but not sufficient, for human consciousness. Pre-frontal cortex is involved as well. 4 The
ascending
arousal
system
 Circadian rhythms from the SCN and other signals to hypothalamus modulate sleep/ arousal state. Neural
Substrates
of
State
of
Consciousness
 25 26 What
is
the
function
of
sleep??
 •  Evidence
for
the
importance
of
sleep:
 •  We
spend
1/3
of
our
life
sleeping

 •  Sleep
is
conserved
throughout
evolution
 (fruit
flies
sleep)

 •  Sleep
deprivation
impairs
brain
function,
 increases
psychosis,
is
associated
with
 diabetes
and
obesity
(impaired
glucose
 metabolism),
inhibits
growth,
impairs
 immune
system,
eventually
can
be
fatal.

 27 Hypotheses
re:
function
of
sleep
 •  To
save
energy
 •  To
consolidate
long-term
memories
 •  To
reactivate
neural
circuits
that
have
 been
involved
in
learning
(neuronal
 replay).
 •  Homeostasis
of
synapses
or
synaptic
 strength
(increase
during
wakefulness,
 decrease
during
sleep).
(“refresh
button”)
 28 When sleep regulation doesn’t work … Example
of
bad
use
of
research
implications..
 Narcolepsy is a disorder marked by excessive daytime sleepiness, uncontrollable sleep attacks, and cataplexy (a sudden loss of muscle tone, usually lasting up to half an hour). Links
between
SLEEP
and
LEARNING:
 •  i 
nsufficient
sleep
impairs
learning
 • 









sleep
enhances,
and
is
in
some
cases
 




necessary
for,
consolidation
of
memories
 Probably an autoimmune disease, with a strong genetic link. An outbreak was reported last year in Finland, possibly in response to the swine flu vaccine. 30 5 Clinical
Uses
for
EEG
 •  EEGs
are
used
to
detect
wave
patterns
that
 are
abnormal
over
diseased
or
damaged
 brain
areas
(e.g.,
because
of
tumors,
blood
 clots,
hemorrhage,
regions
of
dead
tissue).

 •  Shifts
from
a
less
synchronized
pattern
of
 electrical
activity
(low-amplitude
EEG)
to
a
 highly
synchronized
pattern
reflect
epileptic
 activity
(seizure).

 31 •  Epilepsy
is
a
common
neurological
disease,
occurring
in
 mild,
intermediate
and
severe
forms,
and
is
associated
with
 abnormally
hyper-synchronized
activity
of
neurons.

 •  Epilepsy
is
also
associated
with
involuntary
muscle
 contraction
and
a
temporary
loss
of
consciousness.


 •  In
most
cases
the
cause
of
epilepsy
cannot
be
determined.

 Among
the
known
triggers
are
traumatic
brain
injury,
 abnormal
prenatal
brain
development,
heavy
alcohol
and
 illegal
drug
use,
infectious
diseases
like
meningitis
and
 viral
encephalitis,
sleep
deprivation.
 •  http://www.youtube.com/watch? v=CDccChHrgRA&feature=related
 Epilepsy
 32 EEG
for
Seizures
 Conscious
Experiences
 •  Things
we
are
aware
of,
such
as
sensory
 stimuli,
the
passage
of
time,
and
past
 events.
 33 Generalized (tonic/clonic) Seizure Partial Seizure 34 Selective
Attention
 •  Seeking
out
and
focusing
on
stimuli
that
 are
momentarily
important
while
avoiding
 the
distraction
of
irrelevant
stimuli.
 •  Some
insights
into
neural
mechanisms
of
 selective
attention
are
being
gained
from
 the
study
of
individuals
diagnosed
with
 attention
deficit
hyperactivity
disorder
 (ADHD).
 35 ADHD
 •  This
condition
typically
begins
early
in
childhood
and
is
the
 most
common
neurobehavioral
problem
in
school-aged
 children.
 •  ADHD
is
characterized
by
abnormal
difficulty
in
maintaining
 selective
attention,
and/or
impulsiveness
and
hyperactivity.

 •  Functional
imaging
studies
of
the
brains
of
children
with
 ADHD
have
indicated
dysfunction
of
brain
regions
in
which
 catecholamine
signaling
is
prominent,
including
the
basal
 nuclei
and
prefrontal
cortex.

 •  In
support
of
this,
the
most
effective
medication
used
to
treat
 ADHD
is
methylphenidate
(Ritalin®),
a
drug
that
increases
 synaptic
concentrations
of
dopamine
and
norepinephrine.
 36 6 Neural
Mechanisms
of
Conscious
Experiences
 •  Conscious
experience
requires
neural
 processes
within
the
brain.
 •  Conscious
experience
resides
not
in
a
 single
anatomical
cluster,
but
in
a
set
of
 neurons
that
are
temporarily
functioning
 together.
 •  This
grouping
of
neurons
varies
as
our
 attentions
shifts
among
visual
or
auditory
 37 stimuli,
memories,
emotions,
etc.
 From
Sensation
to
Cognition
 •  The
brain
has
an
orderly
representation
of
 personal
space
that
can
be
studied
on
the
 cellular
level.
 •  The
internal
representation
of
personal
 space
is
modifiable
by
experience.
 •  Real
as
well
as
remembered
and
imagined
 extra-personal
space
is
represented
in
the
 posterior
parietal
association
cortex.
 38 Somatosensory
Homunculus
 Recall:
primary
and
association
 Primary cortices
 somatosensory cortex has an orderly representation of personal space Posterior parietal association cortex has an orderly representation of extrapersonal space The brain has an orderly representation of personal space that can be studied on the cellular level. 39 40 A
map
of
our
 shared
 extrapersonal
 space
 Imagine that you stand at Sather gate. What buildings do you see in front of you? Now imagine that you walked across, and you are at Bancroft st. What buildings do you see now? Sproul
Plaza
 41 42 7 ‘Neglect’
in
a
stroke
patient
 Patients with neural damage in the right posterior parietal cortex exhibit visual neglect, as seen in this drawing task. Although the patient is not impaired visually, he does not perceive the left half of the visual world. The burning house 43 44 Learning
and
Memory
 •  Learning
is
the
process
by
which
we
 acquire
knowledge
about
the
world
 •  Memory
is
the
process
by
which
that
 knowledge
is
encoded,
stored
and
later
 retrieved.
 Two
kinds
of
learning/memory
 Implicit
 •  Non-declarative
 •  Procedural
 •  Recall
is
 unconscious,
and
 primed
 Explicit
 •  Declarative
 •  Facts
and
events
 •  Recall
is
conscious
 Eric
Kandel
 Nobel
Prize

 Medicine
2000
 45 46 Memory
 •  Declarative
memory
(
explicit)
is
the
retention
and
recall
 of
conscious
experiences
that
can
therefore
be
put
into
 words
(declared)
i.e.,
facts
and
figures.
 •  One
example
is
the
memory
of
having
perceived
an
 object
or
event
and,
therefore,
recognizing
it
as
familiar
 and
maybe
even
knowing
the
specific
time
and
place
 when
the
memory
originated.
 •  
The
hippocampus,
amygdala,
and
other
parts
of
the
 limbic
system
are
required
for
the
formation
of
declarative
 memories.
 Memory
 •  Procedural
memory
is
the
memory
of
how
to
do
things.
 •  This
is
the
memory
for
skilled
behaviors
independent
of
 any
conscious
understanding,
as
for
example,
riding
a
 bicycle.

 •  The
category
of
procedural
memory
also
includes
 learned
emotional
responses,
such
as
fear
of
spiders,
 and
the
classic
example
of
Pavlov’s
dogs.

 •  The
primary
areas
of
the
brain
involved
in
procedural
 memory
are
regions
of
sensori-motor
cortex,
the
basal
 nuclei,
and
the
cerebellum.
 48 47 8 
Short-term
Memory
 •  Another
way
to
classify
memory
is
in
terms
of
 duration—does
it
last
for
a
long
or
only
a
short
 time?

 •  Working
memory,
also
known
as
short-term
 memory,
registers
and
retains
incoming
information
 for
a
short
time—a
matter
of
seconds
to
minutes— after
its
input.

 •  Short-term
memories
may
be
converted
into
longterm
memories,
which
may
be
stored
for
days
to
 years
and
recalled
at
a
later
time.
The
process
by
 which
short-term
memories
become
long-term
 49 memories
is
called
consolidation.
 The
Neural
Basis
of
Learning
&
Memory
 50 Both
explicit
and
implicit
memory
 are
stored
in
stages
 •  Input
to
the
brain
is
processed
into
 working
memory
before
being
transformed
 into
a
long-term
store.
 •  Until
memories
have
been
converted
to
 long-term
form,
recent
memories
are
 easily
disrupted.

 •  Once
consolidated
to
long-term
form,
 memories
are
relatively
stable,
but
longterm
memory
and
capacity
for
retrieval
 gradually
diminish
 51 The
Neural
Basis
of
Learning
and
Memory
 •  Exactly
how
memories
are
stored
in
the
brain
is
still
unsolved.
One
 model
for
memory
is
long-term
potentiation
(LTP),
in
which
certain
 synapses
undergo
a
long-lasting
increase
in
their
effectiveness
when
 they
are
heavily
used.

 •  Long-term
memory
formation
involves
changes
in
gene
expression
and
 synthesis
of
new
proteins.

 •  These
new
proteins
may
be
involved
in
increased
number
of
synapses,
 or
structural
and
functional
changes
in
individual
synapses
(e.g.,
by
an
 increase
in
the
number
of
receptors
on
the
postsynaptic
membrane).
 •  
This
ability
of
neural
tissue
to
change
because
of
activation
is
known
as
 plasticity.
 52 Four
processes
in
explicit
memory
 •  Encoding
 –  Attention
to
and
processing
of
newly
learned
 information
 –  Association
with
existing
memories
 –  Short-term:
limited
working
memory
 –  Long-term:
vast,
distributed
throughout
cortex
 –  From
short-term
to
long-term
storage
 –  Requires
synthesis
of
new
proteins
 Working
memory
is
a
short-term
memory
 required
for
encoding
and
recall
of
explicit
 knowledge
 Has
very
limited
capacity:

 “The
Magical
Number
Seven,
Plus
or
Minus
Two”
 When
the
brain
is
occupied
–
decreased
executive
 functioning
and
decision
making
 •  Storage
 •  Consolidation
 •  Retrieval
 53 54 9 The
Hippocampus
 Structural MRI revealed bigger hippocampal volume in London cab drivers 55 Superior Autobiographical memory (hyperthymesia ) Individuals with hyperthymesia recall every events that they have personally experienced. A hyperthymestic person can be asked a date, and describe the events that occurred that day, what the weather was like, and many seemingly trivial details that most people would not be able to recall. Six individuals were described to date, By Jim Mcgaugh from UC Irvine. 57 10 ...
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This note was uploaded on 03/09/2011 for the course IB 132 taught by Professor Brooks during the Spring '08 term at University of California, Berkeley.

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