11/17/2011
The Electroencephalogram
Higher Brain Functions
Alpha ()
• Sleep, memory, cognition, emotion, sensation,
motor control, and language
Beta ()
Theta ()
• involve interactions between cerebral cortex
and basal nuclei, brainstem and cerebellum
Delta ()
1 second
(a)
• integrative functions of the brain focus mainly on
the cerebrum, but involves combined action of
multiple brain levels
(b)
• Electroencephalogram (EEG) – monitors surface electrical activity of the
brain waves
• brain waves – voltage changes resulting from action potentials at
superficial layer of cerebral cortex
– 4 types distinguished by amplitude (mV) and frequency (Hz)
14-1
14-2
Types of Brain Waves
•
•
•
•
alpha waves 8 – 13 Hz
– awake and resting with eyes
closed and mind wandering
– suppressed when eyes open
or performing a mental task
beta waves 14 – 30 Hz
– eyes open/ performing
mental tasks
theta waves 4 – 7 Hz
– drowsy or sleeping adults
– if awake and under emotional
stres
delta waves high amplitude,
less than 3.5 Hz
Sleep
• sleep - temporary state of unconsciousness
from which one can awaken when stimulated
Idling
– resembles unconsciousness but can be aroused
Focused on problem or visual stimulus
Why sleep?
Children ok/adults not good awake
Deep sleep – RAS is dampened
• Why Sleep?
– brain glycogen and ATP levels increase in non-REM sleep
– memories strengthened in REM sleep?
14-4
Figure 12.20b
Rhythm of Sleep
Four Stages of Sleep
•
• Through night we go back and forth through stages
Stage 1
– drowsy, close eyes, begin to relax
– often feel drifting sensation, easily awakened if stimulated
– alpha waves dominate EEG
•
Stage 2
– pass into light sleep
– EEG declines in frequency but increases in amplitude
– sleep spindles – high spikes, from interactions between neurons of thalamus
and cerebral cortex
•
Stage 3
–
–
–
–
•
– ENTER rapid eye movement (REM) sleep
- Eyes ocilate- Vital signs increase
- Brain uses more O2 than when awake
- Sleep paralysis stronger
moderate to deep sleep
about 20 - 30 minutes after stage 1
theta and delta waves appear
muscles relax, vital signs (body temp., blood pressure, heart and respiratory
rate) fall
Stage 4
– called slow-wave-sleep (SWS) – EEG dominated by low-frequency, high
amplitude delta waves
– muscles now very relaxed, vital signs are low, & more difficult to awaken
• Dreams occur in both REM and non-REM sleep
• Parasympathetic system active during REM sleep
– causing constriction of the pupils
– erection of penis and clitoris 
14-5
14-6
1
11/17/2011
Sleep Stages
Rhythm of Sleep
• controlled by a complex interaction between the cerebral
cortex, thalamus, hypothalamus, and reticular formation
Awake
Sleep spindles
Stage
• suprachiasmatic nucleus: important control center for
sleep
– Hypothalamus!
– input from eye allows SCN to synchronize multiple
body rhythms with external rhythms of night and
day
• sleep, body temperature, urine production,
secretion, and other functions
REM
sleep
Stage 1
Drowsy
Stage 2
Light sleep
Stage 3
Moderate to
deep sleep
0
10
20
30
40
Time (min)
Stage 4
Deepest sleep
50
60
70
(a) One sleep cycle
EEG stages
Awake
REM
REM
REM
REM
REM
Stage 1
Stage 2
Stage 3
Stage 4
0
1
2
(b) Typical 8-hour sleep period
3
4
Time (hr)
5
6
7
8
14-7
14-8
Memory
Cognition
• Mental processes by which we acquire and use knowledge
– sensory perception, thought, reasoning, judgment, memory,
imagination, and intuition
• association areas of cerebral cortex has above functions
– parietal lobe association area – perceive stimuli
– temporal lobe association area – identifying stimuli
– frontal lobe association area – planning our responses
and personality
• information management requires
– learning – acquiring new information
– memory – information storage and retrieval
• Includes short-term and long-term memory
– Involves many brain regions
• Two types of long-term memory
– Procedural (Non-Declarative): memories of simple skills and
conditioning
- tie a shoelace – chop sticks – rolling a joint!
– Declarative: includes memories that can be verbalized
14-9
14-10
Emotion
Learning & Memory
• hippocampus – memory-forming center (maybe)
– does not store memories
– organizes sensory and cognitive information into unified long-term
memory
• “teaching the cerebral cortex” until a long-term memory is established
– long-term memories are stored in various areas of the cerebral
cortex
– vocabulary and memory of familiar faces stored in superior
temporal lobe
– memories of plans and social roles stored in the prefrontal cortex
• cerebellum – helps learn motor skills
• amygdala - emotional memory
• emotional feelings and memories are interactions
between prefrontal cortex and diencephalon
• prefrontal cortex - seat of judgment, intent, and control
over expression of emotions
• feelings come from hypothalamus and amygdala
• amygdala receives input from sensory systems
– role in food intake, sexual behavior
– one output goes to hypothalamus influencing somatic and visceral
motor systems
– other output to prefrontal cortex important in controlling
expression of emotions
• behavior shaped by learned associations between stimuli,
responses to stimuli, and reward/punishment
8-36
14-12
2
11/17/2011
The General Senses
Functional Regions of Cerebral Cortex
• general (somesthetic, somatosensory, or somatic)
senses
– touch, pressure, stretch, movement, heat, cold, and pain
• Cranial nerves carry general sensations from head to brain
• Ascending tracts bring from the rest of the body
– Via thalamus processes input
– S electively relays signals to the postcentral gyrus (primary somesthetic
cortex)
• awareness of stimuli occurs in primary somesthetic
cortex
– making cognitive sense of stimulation occurs in
somesthetic association area
• Sensory homunculus
Primary somesthetic
cortex
Primary motor
cortex
Somesthetic
association area
Motor association
area
Primary gustatory
cortex
Wernicke area
Broca area
Visual association
area
Prefrontal
cortex
Primary
visual cortex
Olfactory
association
area
Primary
auditory cortex
Auditory
association area
Special senses vs Somesthetic senses
14-13
Sensation
14-14
Sensory Homunculus – Post Central Gyrus
Anterior
Frontal
lobe
Precentral
gyrus
• sensory homunculus –
diagram of primary somesthetic
cortex
• – upside-down sensory map of
the contralateral side of the
body
II III
IV V
I
II
III
IV
V
Genitalia
• shows receptors from body
areas projecting to the gyrus
Central
sulcus
Postcentral
gyrus
Parietal
lobe
• Greater proportion = greater
innervated/sensitive area is.
Tongue
Abdominal
viscera
Occipital
lobe
Viscerosensory area
Lateral sulcus
Insula
Posterior
(a)
Lateral
Medial
(b)
14-15
Motor Control
14-16
Functional Regions of Cerebral Cortex
•
Intention to contract a muscle begins in motor association
(premotor) area of frontal lobes
1. plan is made (degree and sequence of muscle contraction
required)
2. Plan transmitted to precentral gyrus (primary motor area)
– neurons send signals to the brainstem and spinal cord
– ultimately resulting in muscle contraction
•
Primary somesthetic
cortex
Primary motor
cortex
Somesthetic
association area
Motor association
area
Primary gustatory
cortex
Wernicke area
pyramidal cells of the precentral gyrus (upper motor
neurons)
Broca area
Visual association
area
Prefrontal
cortex
– To brainstem/decending tracts
– most fibers decussate in lower medulla oblongata
Primary
visual cortex
Olfactory
association
area
•
in brainstem or spinal cord, upper motor synapse with
lower motor neurons - innervate skeletal muscles
•
basal nuclei and cerebellum are also important in muscle
control
Primary
auditory cortex
Auditory
association area
14-17
Figure 14.21
14-18
3
11/17/2011
Motor Homunculus – Pre-central Gyrus
Input and Output to Cerebellum
(a) Input to cerebellum
(b) Output from cerebellum
Motor cortex
Cerebrum
Cerebrum
V
IV
III
II
Toes
I
Cerebellum
Reticular formation
Brainstem
Vocalization
Salivation
Mastication
Swallowing
Cerebellum
Brainstem
Eye
Inner ear
Reticulospinal
and vestibulospinal
tracts of spinal cord
Spinocerebellar
tracts of spinal cord
Figure 14.24
Figure 14.23b
Lateral
Medial
(b)
14-19
Muscle and joint proprioceptors
Language
14-20
Limb and postural
muscles
Language Centers
• reading, writing, speaking, understanding words
assigned to different regions of the cerebral cortex
• Wernicke area
– recognition of spoken/written language and creates plan
of speech
– transmits plan of speech to Broca area
• Broca area (Speech)
– generates motor plan for muscles of larynx, tongue,
cheeks and lips
– transmits plan to primary motor cortex
Anterior
Posterior
Precentral gyrus
leaves Postcentral
gyrus
Speech center of
primary motor cortex
Angular
gyrus
Primary auditory
cortex
(in lateral sulcus)
Primary
visual cortex
Broca
area
Wernicke
area
Figure 14.25
14-21
Cerebral Lateralization
14-22
Cranial Nerves
– 12 pairs of cranial nerves arise from the base of the
brain
• the difference in
structure and function
of cerebral hemispheres
– exit cranium through foramina
• most motor fibers of cranial nerves begin in nuclei
of brainstem - lead to glands and muscles
• Left hemisphere
possesses language
and analytical abilities
• sensory fibers begin in receptors located mainly in
head and neck and lead mainly to brainstem
• Right hemisphere is
best at visuospatial
tasks
– Special Senses & touch
• most cranial nerves carry fibers between brainstem
and ipsilateral receptors and effectors
8-32
14-24
4
11/17/2011
Cranial Nerves
I Olfactory Nerve
Frontal lobe
Frontal lobe
leaves
Cranial nerves:
Longitudinal
fissure
Olfactory bulb
Olfactory bulb
(from olfactory nerve, I)
Olfactory tract
Olfactory tract
Olfactory tract
Optic chiasm
Cribriform plate of
ethmoid bone
Fascicles of
olfactory nerve (I)
Nasal mucosa
Optic nerve (II)
Temporal lobe
Temporal lobe
Oculomotor nerve (III)
Trochlear nerve (IV)
Infundibulum
Trigeminal nerve (V)
Optic chiasm
Pons
Abducens nerve (VI)
Facial nerve (VII)
Pons
Medulla
Vestibulocochlear nerve (VIII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Cerebellum
Figure 14.28
Medulla
oblongata
Hypoglossal nerve (XII)
Accessory nerve (XI)
Cerebellum
• Sensory only - olfaction
Spinal cord
Spinal cord
(a)
(b)
14-25
b: © The McGraw-Hill Companies, Inc./Rebecca Gray, photographer/Don Kincaid, dissections
II Optic Nerve
14-26
III Oculomotor Nerve
Eyeball
Optic nerve (II)
Oculomotor nerve (III):
Superior branch
Optic chiasm
Optic tract
Inferior branch
Pituitary gland
Ciliary ganglion
Superior orbital fissure
• Motor only
• controls muscles that move eyeball up, and control
iris, lens, and upper eyelid
• Sensory only
14-27
IV Trochlear Nerve
14-28
V Trigeminal Nerve
• largest of cranial nerves
• Mixed
• most important sensory
nerve of the face – touch,
temp., pain
Superior oblique muscle
Superior orbital fissure
Ophthalmic division (V1)
Trigeminal ganglion
Trigeminal nerve (V)
Maxillary division (V2)
Foramen ovale
Infraorbital
nerve
Superior
alveolar nerves
Mandibular division (V3)
Foramen rotundum
Lingual nerve
1
Inferior
alveolar nerve
Anterior trunk of V3 to
chewing muscles
• Motor: mastication
Temporalis muscle
Lateral pterygoid muscle
Medial pterygoid muscle
Trochlear nerve (IV)
V1
Masseter muscle
V3
Anterior belly of
digastric muscle
V2
Figure 14.31
• eye movement (superior oblique muscle)
Motor branches of the
mandibular division (V3)
Distribution of sensory
fibers of each division
Figure 14.32
14-29
14-30
5
11/17/2011
VII Facial Nerve
VI Abducens Nerve
Facial nerve (VII)
Internal acoustic meatus
Geniculate ganglion
Pterygopalatine ganglion
Lacrimal (tear) gland
Chorda tympani
branch (taste and
salivation)
Submandibular ganglion
Lateral rectus muscle
Sublingual gland
Parasympathetic fibers
Superior orbital fissure
to (b)
Motor branch
to muscles of
facial expression
Submandibular gland
Stylomastoid foramen
Abducens nerve (VI)
Figure 14.34a
(a)
Figure 14.33
• Motor only provides eye movement
• motor – major motor nerve of facial muscles, salivary
glands and tear, nasal and palatine glands
• sensory - taste on anterior 2/3’s of tongue
14-31
VIII Vestibulocochlear Nerve
IX Glossopharyngeal Nerve
Vestibular ganglia
leaves nerve
Vestibular
Cochlear nerve
Semicircular
ducts
14-32
Vestibulocochlear
nerve (VIII)
• Motor: swallowing,
salivation, gagging
• sensations from
posterior 1/3 of
tongue
Internal
acoustic meatus
Cochlea
Vestibule
Glossopharyngeal nerve (IX)
Jugular foramen
Superior ganglion
Inferior ganglion
Otic ganglion
Parotid salivary gland
Carotid sinus
Pharyngeal muscles
• Sensory only - hearing and equilibrium
14-33
14-34
X Vagus Nerve
XI Accessory Nerve
Cranial root of XI
Jugular
foramen
• Sensory: taste, hunger,
fullness, tummy troubles
Vagus nerve
Accessory nerve (XI)
Jugular foramen
Foramen
magnum
Spinal root of XI
Pharyngeal nerve
Laryngeal nerve
• Motor swallowing;
smooth muscles/glands
of viscera
Spinal nerves
C3 and C4
Carotid sinus
Vagus nerve (X)
Sternocleidomastoid
muscle
Trapezius muscle
Lung
Heart
Spleen
Posterior view
Liver
Kidney
• Motor only swallowing, head, neck and shoulder
movement
Stomach
Colon
(proximal portion)
Small intestine
14-36
6
11/17/2011
XII Hypoglossal Nerve
Hypoglossal canal
Intrinsic muscles
of the tongue
Extrinsic muscles
of the tongue
Hypoglossal nerve (XII)
Figure 14.39
• Motor only: tongue movements for speech, food
manipulation and swallowing
14-37
7