REGIONS OF THE BRAIN
Midbrain, Forebrain, Hindbrain
Forebrain
 Most complex, includes structures involved in higher level functions
 90 % of the brain
 Composed of Limbic System and Cerebral cortex
Midbrain
 Contains sensory pathways that carry visual information from the eyes back to the part of the brain that
processes visual info. It is the relay station important to processing auditory and visual sensory info
 Also contains the substantia nigra
 Is also the location of brain structures involved in startle reflex
Hindbrain
 Connects spinal cord with rest of brain
 Sensory and motor pathways pass through it
 Contains the medulla, pons, and cerebellum, and reticular formation
 It is the first part of the brain to develop during gestation
Lower-Level/Older Brain Structures
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Brainstem
o Medulla
o Pons
o Reticular formation
Thalamus
Cerebellum
Limbic system
o Amygdala
o Hypothalamus
o Hippocampus
Brainstem
- Oldest and innermost region; an extension of the spinal cord
- Automatic survival functions
- Crossover point where most nerves to and from each side of the brain connect with the body’s opposite side
o Medulla
o Pons
o Reticular formation
MEDULLA – Survival and maintenance functions
- the swelling after spinal cord enters skull
Autonomic involuntary functions breathing, heart rate, blood pressure, and reflex centers of vomiting,
coughing, sneezing, and swallowing
Has pathways for motor movement
Damage to the medulla leads to death
Also helps transferring messages between brain and spinal cord (sensory tracts are ascending and motor tracts
are descending)
Even really primitive animals have a medulla, like lampreys and hagfish
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PONS - Coordinate movement of left and right sides of body, facial muscles
- sits just above the Medulla
- Helps coordinate movement (equilibrium, posture) on left and right sides of body
“Bridge” that connects brainstem and cerebellum
- Serves as pathway for nerve fibers connecting cerebral cortex to cerebellum
- One disease that causes demyelination in the pons can lead to locked in syndrome
- Also helps regulate the rhythm of breathing through an area that is involved in switching from
expiration to inspiration
- Point of origin and termination of four cranial nerves (two pairs) that transfer sensory
information and motor impulses to and from the facial region of the brain control some of the
muscles involved in facial expression and sensation
RETICULAR FORMATION - Involved in arousal, and wake/sleep cycles and filtering out background stimuli
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extends through brainstem and thalamus
Consists of more than 100 small neural networks with various functions  descending
pathways receive input from hypothalamus and is important in producing autonomic nervous
system response, ascending pathways deal with sleep and arousal
Sensory input from spinal cord passes to thalamus, some of it through reticular formation, which
filters incoming sensory stimuli to discriminate irrelevant background stimuli
(HABITUATION)
Stimulate the reticular formation  Instant alertness;
Sever reticular formation  permanent coma [Guiseppe Moruzzi and Horace Magoun
(1949), cat]
Some imaging studies have shown abnormal activity in reticular formation in people with
chronic fatigue syndrome
Also involved in connecting impulses from muscles not under voluntary control to those under
voluntary control (such as those used in swallowing and speech)
THALAMUS - Sensory switchboard, processes and distributes motor and sensory info to and from cerebral
cortex, helps regulate consciousness, sleep, alertness
- sits at the top of the brainstem
- Its function includes relaying sensation, spatial sense, and motor signals to the cerebral cortex,
relaying info between cortex and subcortical areas, along with the regulation of consciousness,
sleep, and alertness
- Every sensory system (with the exception of the olfactory system (smell)) includes a thalamic
nucleus that receives sensory signals and sends them to the associated primary cortical area.
- Fatal familial insomnia is a hereditary prion disease in which degeneration of the thalamus
occurs, causing the patient to gradually lose his ability to sleep and progressing to a state of total
insomnia, which invariably leads to death.
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In people with an amputated limb, mild electrical stimulation of thalamus caused the sensations
known as “phantom limb”
Also involved in awareness, attention, motivation, and emotional aspects of sensations
CEREBELLUM –Motor Control and several types of motor learning, physical coordination
- “The Little Brain” - It looks like a little brain but it is actually continuous thin layer of neural tissue tightly folded
accordion-style.
- Controls learned/skilled movements that have become automatic (stores “programs” for movements)
- Involved in some cognitive functions (attention and language)
- Is involved in coordination, precision, and timing of movement.
- Receives input from sensory systems and other parts of the brain and spinal cord and integrates them to fine tune
motor activity.
- Damage to Cerebellum does not cause paralysis but causes disorders in fine movement, gait, equilibrium, posture,
and motor learning, problems with skilled, voluntary movement (and for some areas, ability to estimate time)
Causing errors in force, direction, speed and amplitude of movement
 Dysarthria – problems with speech articulation
 Dysmetria – problems judging distances or ranges of movement
 Dysdiadokinesia – inability to perform rapid alternating movements
 Other ataxia
Examples:
- Riding a bike, walking, typing,
- Circuits in the cerebellum similar across all species of vertebrates
LIMBIC SYSTEM
- The limbic system is a donut-shaped (or horseshoe shaped area) in the center of the brain.
- In various combinations, its structures form complex neural circuits that play critical roles in memory and
emotion (especially fear and aggression)
- Responsible for much of the influence on the body’s hormonal system
o Hypothalamus and Pituitary gland
o Amygdala
o Hippocampus
HYPOTHALAMUS – The thermostat, reward center, survival behaviors
- Controls the body’s internal temperature, keeping it within normal limits
- Survival behaviors – hunger, thirst, frequency of sexual activity, fear, aggression
- Controls pituitary gland and , through pituitary control, is involved in all aspects of behavior that are
regulated by hormones – eating, stress response, sexual behavior
- Receiving certain types of sensory information triggers the hypothalamus to release hormones and
neurotransmitters that direct the pituitary gland to respond by secreting a particular hormone or to stop
secreting a certain hormone. The hypothalamus releases hormones that stimulate the pituitary gland to
release its hormones, which triggers other endocrine glands to release their hormones.
For example, you see a table laden with cookies, chocolate, and cake and your hypothalamus tells
your pituitary gland to secrete hormones that increases your hunger level.
- Lateral Hypothalamus signals hunger, Ventromedial hypothalamus signals satiety
“Reward Center”
Olds and Milner studyWhen they stimulated the hypothalamus of a rat, which produced a pleasurable sense of
reward in the rat. When they allowed the rat to press a bar that would trigger stimulation of their hypothalamus, the
rat would choose pressing the bar over food. If they put an electrified floor in between the rat and the bar, the rat
would cross the floor (receiving painful shocks) in order to press the bar.
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Similarly, the hypothalamus also influences reproductive behavior (destroying the hypothalamus ceases
copulatory behavior in rats and dogs; stimulation of it will lead to increases in copulatory behavior).
The hypothalamus and body temperature  In 1912, a researcher by the name of Barbour placed a silver wire into
a dog’s hypothalamus. When the wire was heated, the dog’s body temperature decreased, when the wire was
cooled, the dog’s body temperature increased. If damage, which is also called a lesion, is done to the hypothalamus,
it can’t regulate increases or decreases temperature, but it can still influence shivering or vasoconstriction
Reproductive behavior In animals, damage can lead to not exhibiting normal reproductive behaviors (i.e., mating
behaviors)
HIPPOCAMPUS - Memory
- The hippocampus is the part of the brain that processes memory
- Also involved in spatial awareness
- It doesn’t “contain” memories, it forms new memories, but only for certain types of memory (episodic,
declarative) (How do we know? )
- If damage is done to this area, people are unable to create new memories. There is a very famous case that
demonstrates this difficulty. A man by the initials of H. M. suffered from epilepsy as a child. In an attempt to
control his epileptic seizures, doctors did surgery on his brain and removed a portion, part of which was the
hippocampus. He no longer suffered from epilepsy, but without his hippocampi, everything in his memory
vanished after a few minutes. He could not form long-term memories and his short-term memory only lasted
about five minutes. When his family moved across town, he kept returning to old house because he didn’t have
the memory that they had moved.
- People with Alzheimer’s disease show damage to this area
o Alzheimer’s patients not only experience memory deficits, they also show problems related to spatial
awareness such as disorientation, difficulty remembering directions and so on
- This structure experiences neurogenesis (new neurons), unlike most other brain structures. How does this fit
with the functions performed by the hippocampus
AMYGDALA – “Almond” (for shape of structure) – Plays role in emotions (especially fear and aggression)
- Main function – Emotions (especially fear and aggression)
- Affects ability to read emotions in facial expressions
- The amygdala also assists in the perception and encoding of emotion and emotional memories, specifically
those associated with fear and aggression Emotional learning and fear conditioning
- Stimulating part of the amygdala can lead to an aggressive response in animals, while stimulating another
portion can lead to a fearful response. However, there are a number of factors that influence fear and
aggression, so this isn’t the only place of the brain that influences those behaviors. Fear is caused by the
interaction between limbic responses and the judgments that our frontal lobes make about those responses
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In 2006, researchers observed hyperactivity in the amygdala when patients were shown threatening faces or
confronted with frightening situations. Patients with more severe social phobia showed a correlation with
increased response in the amygdala
- People with larger amygdala were better able to make accurate social judgments about other persons' faces
- Damage Difficulty interpreting emotional content and facial expressions
In general, there isn’t ONE part of the brain for any type of behavior/mental process. There are typically several
areas that have different influences on such complex things as our behavior and thoughts.
BASAL GANGLIA
- Outer sides of thalamus
- Involved in planning and producing movement
- The functioning of this structure depends largely on dopamine
- People with Parkinson’s disease display abnormal basal ganglia
- Also plays role in formation of habits, which is a type of learning  when you learn a habitual behavior, the
basal ganglia connect the stimulus causing it with the response
- The nucleus accumbens  A structure thought to be part of the basal ganglia. It plays a critical role in the
brains response to reward and anticipation of reward. Drugs that are addictive, like alcohol and cocaine, engage
the nucleus accumbens.
Imaging Tools
Structure
CT Scan/CAT Scan – Computer Axial Tomography
Earlier technique but still used technology has improved. X-rays taken from many different
angles and those are used to develop a structural image of the brain
MRI – Magnetic Resonance Imaging
The head is put in a strong magnetic field which causes the spinning atoms of the brain
molecules to align along the magnetic field. Then a radio wave momentarily disorients the atom
and when they return to their normal spin, they release signals that provide detailed image of the
soft tissues of the brain (or other parts of the body).
Function
EEG – electroencephalogram
An amplified read out of the regular waves of electrical activity of the brain’s neurons. A
stimulus is presented repeatedly and a computer filters out unrelated brain activity, allowing us
to isolate the electrical wave evoked by the stimulus/
PET scan – Positron Emission Tomography
The brain will only use glucose for fuel. The more active a given area of the brain is, the more
glucose is consumed in that area. A person is given temporarily radioactive glucose and the PET
scan detects where the glucose goes by locating the radioactivity. Provides an image of brain
activity and allows us to see what areas are engaged when the person engages in certain tasks or
experiences certain types of stimuli.
fMRI – Functional MRI
When an area of the brain is more active, more blood flows to that area. fMRI detects blood flow
to different brain areas by comparing MRI scans taken in less than a second apart.