Transcript long-term memory - Daniela Sartori

Chapter 8
Lecture
Outline
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Chapter 8 outline
Structural
organization of the brain
Cerebrum
Diencephalon
Midbrain
and hindbrain
Spinal cord tracts
Cranial and spinal nerves
8-2
Structural Organization of the Brain
8-3
Structure Organization of the Brain
 Consists
of brain and
spinal cord
 Receives input from
sensory neurons
 Directs activity of motor
neurons
 Association neurons
integrate sensory and
motor activity
 Perform learning and
memory
8-4
CNS continued
CNS
composed of gray and white matter
Gray matter consists of neuron bodies and
dendrites
White matter (myelin) consists of axon tracts
Adult brain weighs 1.5kg
Contains 100 billion neurons
Receives 20% of blood flow to body
8-5
Embryonic Development
8-6
Embryonic Development
tube forms from groove in ectoderm by 20th day
 Becomes the CNS
 Neural crest cells develop where tube fuses
 Become ganglia of PNS
 Neural
8-7
Embryonic Development continued
During
4th week, 3
swellings form on
neural tube
These will become
forebrain, midbrain
and hindbrain
8-8
Embryonic Development continued
5th week: Forebrain elaborates into telencephalon and
diencephalon
 Midbrain does not subdivide
 Hindbrain forms metencephalon and myelencephalon
 During
8-9
Embryonic Development continued
 Telencephalon
grows
disproportionately
forming hemispheres
of cerebrum
 Ventricles and central
canal are remnants of
hollow part of neural
tube
 Contain cerebral
spinal fluid (CSF)
8-10
Cerebrum
8-11
Cerebrum
Is
largest part
of brain (80%
of mass)
Is responsible
for higher
mental
functions
8-12
Cerebrum continued
Its
right and left
hemispheres are
interconnected by
tract of the corpus
callosum
8-13
Cerebral Cortex
 Is
highly convoluted
 An elevated fold is called a gyrus
 A depressed groove is called a sulcus
8-14
Cerebral Cortex continued
Each
hemisphere has 5 lobes: frontal, parietal,
temporal, occipital and insula
8-15
Cerebral Cortex continued
 Frontal
lobe is
separated from parietal
by central sulcus
 Precentral gyrus of
frontal lobe is involved
in motor control
 Postcentral gyrus of
parietal lobe receives
sensory info from areas
controlled by precentral
gyrus
8-16
Cerebral Cortex continued
8-17
Cerebral Cortex continued
Temporal
lobe contains auditory centers; receives
sensory info from cochlea
Also links and processes auditory and visual info
8-18
Cerebral Cortex continued
Occipital
lobe is responsible for vision and
coordination of eye movements
8-19
Cerebral Cortex continued
Insula
plays role in memory encoding
Integrates sensory info with visceral responses
Assesses bodily states that accompany emotions
8-20
Visualizing the Brain
8-21
Visualizing the Brain
X-ray
computed tomography (CT) visualizes soft
tissues
Positron-emission tomography (PET) is used to
examine brain metabolism and blood flow, drug
distribution
8-22
Visualizing the Brain continued
 Magnetic
resonance imaging (MRI) shows brain function
in the image below
 Functional MRI (fMRI) shows areas with increased neural
activity by tracking blood flow
8-23
Electroencephalogram (EEG)
Measures
electrical activity of cerebral cortex
Used to diagnose epilepsy and brain death
8-24
EEG Waves
Alpha
waves are
recorded from parietal
and occipital lobes with
person awake, relaxed,
eyes closed
Beta waves are
strongest from frontal
lobes; evoked by visual
stimuli and mental
activity
8-25
EEG Waves continued
 Theta
waves come from
temporal and occipital lobes
 Common in newborns
 In adults indicates
severe emotional stress
 Delta waves are from
cerebral cortex
 Common during adult
sleep and in awake
infants
 In awake adult indicates
brain damage
8-26
Sleep
2
types of sleep are recognized
REM - rapid eye movement
EEGs are similar to awake ones
Type when dreaming occurs
Non-REM has delta waves
Appears to be crucial for consolidation of shortinto long-term memory
8-27
Functional Specializations of the
Brain
8-28
Cerebral Nuclei
 Are
distinct masses of cell bodies located deep inside cerebrum
 Function in control of voluntary movement
8-29
Cerebral Nuclei continued
 Have
reciprocal excitatory connections with the cerebral cortex
that create a motor circuit
8-30
Cerebral Lateralization
Refers
to specialization of each hemisphere for certain
functions
Each cerebral hemisphere controls movement on
opposite side of body
And receives sensory info from opposite side of
body
Hemispheres communicate thru the corpus callosum
(Fig 8.1) which contains about 200 million fibers
8-31
Cerebral Lateralization continued
Left
hemisphere
possesses language
and analytical abilities
Right hemisphere is
best at visuospatial
tasks
8-32
Language
 Language
areas of brain are known mostly from aphasias
 = speech and language disorders due to brain damage
 Broca’s area is necessary for speech
 Wernicke’s area is involved in language comprehension
8-33
Limbic System and Emotion
 The
hypothalamus and
limbic system (shown in
green) are crucial for
emotions
 Including aggression,
fear, feeding, sex and
goal-directed
behaviors
8-34
Learning and Memory
8-35
Memory
Includes
short- and long-term memory
Involves a number of regions in brain
There are two types of long-term memory
Non-declarative (explicit) includes memories of
simple skills and conditioning
Declarative (implicit) includes verbal memories
Amnesiacs have impaired declarative memory
8-36
Memory continued
 Hippocampus
is critical
for acquiring new
memories
 And consolidating
short- into long-term
memory
 Amygdala is crucial for
fear memories
 Storage of memory is in
cerebral hemispheres
 Higher order processing
and planning occur in
prefrontal cortex
8-37
Long-Term Potentiation (LTP)
Glutamate
activates AMPA
and NMDA
postsynaptic
receptors in
hippocampus
Promotes an inc.
in Ca2+ concent.
in cytoplasm
 needed for LTP
to be induced
8-38
Long-Term Potentiation (LTP) continued
Post-synaptic
neuron also receive input from other
presynpatic neurons (release GABA)
GABA’s inihibiton lessened by another retrograde
messenger prod. by post-synaptic neuron
endocannabinoid as retrograde messenger
stim. by depolarization (by glutamate)
 effect termed—depolariztion-induced
suppression of inhibition
 may also effect LTP
8-39
Neurogenesis in Hippocampus
Appears
to be crucial for learning and memory
Hippocampus contains neural stem cells that
continually produce new neurons (neurogenesis)
Stress or depression impede learning and cause
hippocampus to shrink
Stress reduction and antidepressants return size to
normal
8-40
Brain Structures and their Functions
8-41
Thalamus and Epithalamus
 Are
located at base of cerebral hemispheres
 Thalamus is a relay center thru which all sensory info (except
olfactory) passes to cerebrum
 And plays role in level of arousal
 Epithalamus contains the choroid plexus which secretes CSF
 Also contains pineal gland which secretes melatonin
 Involved in sleep cycle and seasonal reproduction
8-42
Hypothalamus
 Is
most important structure for
homeostasis
 Contains neural centers for
hunger, thirst, body
temperature
 Regulates sleep, emotions,
sexual arousal, anger, fear,
pain and pleasure
 Controls hormone release
from anterior pituitary
 Produces ADH and oxytocin
 Coordinates sympathetic and
parasympathetic actions
8-43
Pituitary Gland
 Is
divided into anterior and
posterior lobes
 Posterior pituitary stores and
releases ADH (vasopressin)
and oxytocin
 Both made in
hypothalamus and
transported to pituitary
 Hypothalamus produces
releasing and inhibiting
hormones that control anterior
pituitary hormones
8-44
Circadian Rhythms
Are
body's daily rhythms
Regulated by SCN (suprachiasmatic nucleus) of
hypothalamus
SCN is the master clock
Adjusted daily by light from eyes
Controls pineal gland secretion of melatonin which
regulates circadian rhythms
8-45
Midbrain
Contains:
Superior
colliculi -- involved in visual reflexes
Inferior colliculi -- relay auditory information
Red nucleus and substantia nigra -- involved in motor
coordination
S. nigra dopamine neurons degenerate in
Parkinson’s
8-46
Midbrain continued
 Mesolimbic
dopamine neurons are involved in reward and
addiction
 Abused drugs cause dopamine release from the nucleus
accumbens
8-47
Hindbrain
Contains
pons, cerebellum and medulla
8-48
Respiratory Control Centers in Brain Stem
 Contains
several nuclei
of cranial nerves
 And 3 important
respiratory control
centers
 Apneustic and
pneumotaxic centers
in pons
 Rhythmicity center
in medulla oblongata
8-49
Cerebellum



2nd largest structure in brain containing 50 billion neurons
Receives input from proprioceptors (joint, tendon and muscle receptors)
Involved in coordinating movements along with cerebral nuclei and motor
areas of cortex
8-50
Medulla
 Contains
all tracts that
pass between brain
and spinal cord
 nuclei of cranial
nerves
 And several crucial
centers for
breathing and
cardiovascular
systems (vital
centers)
8-51
Reticular Activating System (RAS)
 Is
an ascending arousal
system that originates in
groups of neurons in the
pons, midbrain reticular
formation, hypothalamus
and basal forebrain
 These project to the
cerebral cortex and
control its level of
arousal
 Activation of the RAS
promotes
wakefulness; inhibition
promotes sleep
8-52
Spinal Cord
8-53
Spinal Cord Tracts
Sensory
info from body travels to brain in ascending
spinal tracts
Motor activity from brains travels to body in
descending tracts
8-54
Ascending Spinal Tracts
 Ascending
sensory
tracts decussate
(cross) so that brain
hemispheres
receive info from
opposite side of
body
 Same for most
descending motor
tracts from brain
8-55
Descending Spinal Tracts
 Are
divided into 2 major
groups:
 Pyramidal (or
corticospinal) tracts
descend from cerebral
cortex to spinal cord
without synapsing
 Originate in motor
cortex
 Function in control of
fine movements
8-56
Descending Spinal Tracts continued
 Extrapyramidal
(or
Reticulospinal) tracts
descend with many
synapses
 Influence movement
indirectly
8-57
Descending Spinal Tracts continued
8-58
Peripheral Nervous System
8-59
Peripheral Nervous System (PNS)
Consists
of nerves that exit from CNS and spinal
cord, and their ganglia (= collection of cell bodies
outside CNS)
8-60
Cranial Nerves
Consists
of 12 pairs of nerves
2 pairs arise from neurons in forebrain
10 pairs arise from midbrain and hindbrain neurons
Most are mixed nerves containing both sensory and
motor fibers
Table 8.7 Summary of Cranial Nerves
8-61
Spinal Nerves
 Are
mixed nerves that separate next to spinal cord into dorsal
and ventral roots
 Dorsal root composed of sensory fibers
 Ventral root composed of motor fibers
8-62
Spinal Nerves
continued
There
are 31 pairs:
8 cervical pairs,
12 thoracic pairs,
5 lumbar pairs,
5 sacral pairs,
1 coccygeal pair
8-63
Reflex Arc
 Is
a simple sensory input, motor output circuit involving only
peripheral nerves and spinal cord
 Sometimes arc has an association neuron between sensory and
motor neuron
8-64