Neuropsychology (Psyc 3311)
D. Erik Everhart, Ph.D.
everhartd@mail.ecu.edu
314 Rawl Building
Office Phone:
328-4138
Background
z BA (1992) University of Delaware
z MS (1995) Clinical Psych, Virginia Tech
z PhD (1998) Clinical Psych,
Virginia Tech
z Neuropsych/Geropsych
Internship (1998) Buffalo VAMC
z Neuropsychology Fellowship
(2000) Department of Neurology SUNY Buffalo School of Medicine
Neurons and Glial Cells
z
Cells range from .01 to
.05 mm in diameter.
z
Brain tissue = Jello!
z
Fix in formaldehyde
z
Histology
z
Nissl (cresyl violet)
stain.
z
Golgi stain (silver
chromate).
z
Golgi, Cajal, and the
Neuron Doctrine.
Prototypical Neuron
z
Soma organelles:
y
nucleus
y
rough ER
y
smooth ER
y
Golgi apparatus
y
mitochondria
z
Axon
y
axon hillock
y
terminal bouton
y
microtubules,
microfilaments
y
synaptic cleft
Prototypical Neuron - con’t
z
Dendrites
y
dendritic tree
y
receptors
Classifying Neurons
z
Neurites
y
unipolar
y
bipolar
y
multipolar
z
Dendrites
y
pyramidal
y
stellate
Classifying neurons- con’t
z
Connections
y
sensory neurons
y
motor neurons
y
interneurons
z
Axon length
y
Golgi I
y
Golgi II
Classifying Neurons- con’t
z
Neurotransmitters
y
dopamine
y
acetylcholine
Glial Cells
z
Microglia
z
Astrocytes
z
Oligodendrocytes
z
Schwann cells
z
Radial Glia
Blood Brain Barrier
Neurons and Synapses
Sensory Neurons
z
INPUT From sensory
organs to the brain and spinal cord.
Motor Neurons
z
OUTPUT From the brain and spinal cord To the muscles and
glands.
Interneurons
z
Interneurons carry
information between other neurons only found in the brain and spinal cord.
Structures of a neuron
The cell body
y
Round, centrally located
structure
y
Contains DNA
y
Controls protein manufacturing
y
Directs metabolism
y
No role in neural
signaling
Dendrites
z Information collectors
z Receive inputs from
neighboring neurons
z Inputs may number in
thousands
z If enough inputs the cell’s
AXON may generate an output
Dendritic Growth
z Mature neurons generally
can’t divide
z But new dendrites can grow
z Provides room for more
connections to other neurons
z New connections are basis
for learning
Axon
z
The cell’s output
structure
z
One axon per cell, 2
distinct parts
y tubelike structure branches
at end that connect to dendrites of
other cells
Myelin sheath
z White fatty casing on axon
z Acts as an electrical
insulator
z Not present on all cells
z When present increases the
speed of neural signals down the axon.
How neurons communicate
z
Neurons communicate by
means of an electrical signal called the Action Potential
z
Action Potentials are
based on movements of ions between the outside and inside of the cell
z
When an Action Potential
occurs a molecular message is sent to neighboring neurons
Ion concentrations
The Cell Membrane is Semi-Permeable
Resting Potential
z
At rest the inside of
the cell is at -70 microvolts
z
With inputs to dendrites
inside becomes more positive
z
if resting potential
rises above threshold (-55) an action potential starts to travel from cell body
down the axon
z
Figure shows resting
axon being approached by an AP
Depolarization ahead of AP
z
AP opens cell membrane
to allow sodium (NA+) in
z
inside of cell rapidly
becomes more positive than outside
z
this depolarization
travels down the axon as leading edge of the AP
Repolarization follows
z
After depolarization
potassium (K+) moves out restoring the inside to a negative voltage
z
This is called
repolarization
z
The rapid depolarization and repolarization
produce a pattern called a spike discharge
Finally, Hyperpolarization
z
Repolarization leads to
a voltage below the resting potential, called hyperpolarization
z
Now neuron cannot
produce a new action potential
z
This is the relative
refractory period
Neuron to Neuron
z Axons branch out and end
near dendrites of neighboring cells
z Axon terminals are the tips
of the axon’s branches
z A gap separates the axon
terminals from dendrites
z Gap is the Synapse
Synapse
z axon terminals contain small
storage sacs called synaptic vesicles
Neurotransmitter Release
z Action Potential causes
vesicle to open
Locks and Keys
z
Neurotransmitter
molecules have specific shapes
Some Drugs work on receptors
z Some drugs are shaped like
neurotransmitters
z Antagonists : fit the
receptor but poorly and block the NT
y
e.g. beta blockers
Summary
z 3 types of neurons
z The cell membrane
z Ion movements
z Action potentials
z Synapse
z Neurotransmitters
z Receptors and ions
z Agonists and antagonists
Terms con’t
Basic terms - con’t
Other basic terms
z
Contralateral and
ipsilateral
z
unilateral and bilateral
z
proximal and distal
z
Afferent and efferent
Meninges
Spinal cord and peripheral nerves
z
31 segments
y 8 cervical
y 12 thoracic
y 5 lumbar
y 5 sacral
y
1 coccygeal
Spinal cord cross section
z White and gray matter
z Anterior horn
z Posterior horn
z Peripheral nerves
y anterior root (motor)
y posterior root (sensory
x also called dorsal root
Question…...
z
What happens if you cut
the posterior root (dorsal root) on any given peripheral nerve?
Sensory Pathways
z Three main sensory pathways
enter the spinal cord.
z In general, sensory fibers
synapse just prior to crossing over.
Pain-temperature pathway
z Enters spinal cord, crosses
over to opposite half almost immediately (within one or two spinal cord
segments.
z Ascends to thalamus on the
opposite side.
z Moves on to cortex.
Pain-temperature con’t
z Lesion: results in loss of pain-temperature
sensation contralaterally below the level of the lesion.
Proprioception/stereognosis
(conscious pathway)
z Remains ipsilateral, crosses
over at the junction between the spinal cord and brain stem.
z After the crossover, forms
medial lemniscus and travels to the thalamus and cortex.
z Fasciculus gracilus and
fasciculus cuneatus (or posterior columns).
Proprioception/stereognosis
z Lesion: results in loss of conscious proprioception
and stereognosis ipsilaterally below the level of the lesion.
Proprioception (unconscious)
z Also known as
spinocerebellar pathway.
z For walking/performing
duties subconsciously.
z Ipsilateral….goes to
cerebellum.
z Lesion: Ipsilateral loss of unconscious
proprioception.
Light touch
z Part of this pathway remains
uncrossed until it reaches the brain stem, and partially crosses over at lower
levels of the thalamus.
z Lesion: light touch is typically spared in unilateral
spinal cord
injuries!
Major Descending Spinal Tracts
Motor pathways
z The spinal cord has two
major descending motor pathways.
y Lateral pathway - direct
cortical control
y Ventromedial pathway - brain
stem control
The Lateral Pathway
z Voluntary movement
z There are two tracts within
the lateral pathway that you should know:
z Corticospinal tract
x
about 1 million axons
z Cortico-rubrospinal tract
y facial muscles
y cranial nerves ~
Corticospinal tract
z Originates in the motor
cortex, descends to brainstem, and crosses at the pyramidal decussation.
z Synapses on anterior horn
cells just prior to leaving the spinal cord.
z Upper motor neuron versus
lower motor neuron.
Spinal Cord: Lateral Pathway
Corticospinal tract
z Also called Pyramidal tract
z Motor cortex ---> spinal
cord
y uninterrupted axon
y 2/3 of axons from motor
cortex
y 1/3 from somatosensory
cortex
z Decussates at medullary
pyramids
z Contralateral control
movement ~
Upper and lower MN defects
z
Upper Motor Neuron
y
spastic paralysis
y
minimal atrophy
y
hyperreflexia
y
babinski reflex present
z
Lower Motor Neuron
y
flaccid paralysis
y
significant atrophy
y
fasciculations and
fibrillations present
y
hyporeflexia
y
babinski not present
Major Descending Spinal Tracts
Rubrospinal tract
z
Begins in the
red-nucleus of the midbrain.
z
Receives input from the
cortex and cerebellum.
z
Assists with motor
control of the lower arms, feet, and legs….but NOT fingers!
Lateral Pathway Damage
z Lesion both tracts
y no independent movement of
distal limbs
z Corticospinal only
y same deficits
y recovery over several months
y compensation by rubrospinal
tract ~
Major Descending Spinal Tracts
The Ventromedial Pathway
z Neurons originate in
brainstem
z Vestibulospinal &
tectospinal tracts
y head & posture posture
y orienting responses
z Pontine & medullary
reticulospinal tracts
y originate in reticular
formation
y trunk & antigravity leg
muscles
Ventromedial pathway
z There are two ventromedial
tracts that you should know at this point:
y vestibulospinal
y reticulospinal
Vestibulospinal tract
z Originates in brainstem
z Projects bilaterally down
the spinal cord
z Important for regulation of
posture (within trunk and legs).
Major Descending Spinal Tracts
Spinal Cord: Ventromedial Pathway
Reticulospinal tract
z Located within midbrain
y important for control of
muscle tone, respiration, and coughing.
Spinal Cord: Ventromedial Pathway
Major Descending Spinal Tracts
12 Cranial nerves
12 Cranial nerves
z
I. Olfactory
z
II. Optic
z
III. Oculomotor
z
IV. Trochlear
z
V. Trigeminal
z
VI. Abducens
z
VII. Facial
z
VIII. Statoacoustic
z
IX. Glossopharyngeal
z
X. Vagus
z
XI. Acessory
z
XII. Hypoglossal
Ventricular system
z
Lateral Ventricles
z
Third ventricle
z
cerebral aqueduct
z
fourth ventricle
z
Purpose: cushions brain and provides nutrients.
Ventricular system
Medulla
z
Directly superior to
spinal cord.
z
Contains cell bodies of
many cranial nerves.
z
Most motor fibers cross
at this region (pontomedullary junction)
z
Control of many vital
functions.
Medulla
z
Reticular activating
system (which is important for arousal and sleep).
Pons
z
Superior to medulla and
anterior to cerebellum.
z
Main connective bridge
from rest of brain to cerebellum.
z
Point of synapse of some
cranial nerves.
z
Important center for eye
movements and balance.
Pons
z
All descending info goes
through pons.
z
Ascending information
from medulla.
z
Portions of the reticular
formation.
Inferior Colliculi
z
Back of brainstem, superior
to pons.
z
Inferior colliculus
y
auditory
y
tonotopic mapping of
frequencies
Superior Colliculi
z
Superior to inferior
colliculi
z
Visual
y
point to point mapping
y
orienting responses
y
depth vision
y
conjugate vision
y
attention shifts
Pineal Gland
z
Top of brainstem and
superior to superior colliculus.
z
“Third eye.”
z
Regulates sleep/wake
cycles.
z
Regulates temperature
changes.
Hypothalamus
z
Below the thalamus.
z
“kingpin of the viscera”
z
Regulates homeostasis
z
Feeding/drinking.
Cerebellum
z
Posterior or caudal to
brainstem.
z
“Real-time updating of
where things are.”
z
Smooth, coordinated
movement.
z
Procedural memory.
Thalamus
z
Gateway to the cortex.
z
Relay center
y
sensory information
y
motor information
Thalamus
z
Lateral geniculate
nucleus and vision.
Thalamus
z Magnocellular layer: low levels of light, insensitive to color.
z Parvocellular layer: color sensitive, requires high levels of
light.
Cerebral Cortex
z
Vocabulary
y
gyri (gyrus)
y
sulci (sulcus)
y
fissure
Cerebral Cortex
z Cytoarchitecture
y Brodman’s map
z Function
y Luria
Luria’s First Functional Unit
z Regulation of cortical
“tone”
z Waking and sleeping
z General arousal
z Posture
Second Functional Unit
z Obtaining, processing, and
storing information arriving from the outside world.
z (primarily sensory
functions)
Third Functional Unit
z Programming, regulating, and
sequencing mental and motor activity.
z (primarily motor output)
Within second and third functional units….
z Primary cortex
z Secondary cortex
z Tertiary cortex
Third Unit - Frontal lobes
z
Primary motor cortex
z
Homunculus Man
z
Secondary motor cortex
z
tertiary - Prefrontal
Homunculus Man
Second Unit -Parietal Lobes
z
Primary somatosensory
cortex
z
Secondary association
y
astereognosis
z
Tertiary areas
y
math, geography,
construction
Homunculus Man
Second Unit -Occipital Lobes
z
Primary cortex
y
area 17 or V1
z
Secondary cortex
y
area 18 or V2
z
Tertiary cortex
y
area 19 or V3
Second Unit - Temporal Lobes
z
Primary auditory cortex
(Heschyl’s Gyrus)
z
Secondary cortex
y
Wernicke’s area
z
Tertiary cortex
y
hippocampus