major sections of the brain

Major Sections of the Brain

The Brain

• Three important parts– Brain Stem (including the cerebellum and

thalamus) – Limbic System– Cerebral Cortex

Older Brain Structures/Lower Level Functions

• Brainstem – Medulla– Pons– Reticular formation

• Thalamus • Cerebellum • Limbic system

– Amygdala– Hypothalamus– Hippocampus

Brainstem• Survival and

maintenance functions

• Crossover point where most nerves to and from each side of the brain connect with body’s opposite side

Brainstem• Medulla - heart rate,

breathing, blood pressure and has pathway for motor movement

• Pons – Helps coordinate movement

• Reticular Formation –Sleep and arousal

Brainstem

• Thalamus– Sits at the top of the brainstem– Relays sensory info (except smell), spatial sense,

and motor signals to sensory areas of cerebral cortex and transmits replies to cerebellum and medulla

– Helps regulate consciousness, sleep, and alertness– One consequence of damage = fatal insomnia

• Cerebellum – “Little Brain”– Nonverbal learning and memory,– Coordinates voluntary movement and

balance– Controls Learned/skilled movements that are

automatic (i.e., walking)

Cerebellum Damage

Affects fine movement, gait, equilibrium, posture, and voluntary movement causing Errors in force, direction, speed and amplitude of movements.

Other Cerebellum Damage

• Dysarthria – speech articulation• Dysmetria – judging distances and range

of movements• Dysdiadokinesia – inability to perform

rapid alternating movements• Other Ataxia

Limbic System

Limbic System• Hypothalamus

– Hunger, thirst, body temp., reproductive behavior– Controls pituitary gland– Emotion and “Reward Center” (Olds & Milner (1954))

• Hippocampus– Forms new memories (episodic)– Spatial orientation

• Amygdala – Aggression, fear, and perception of them– Processing/encoding emotional memories– Regulating feeding

Limbic System Damage

• Hypothalamus – Death• Amygdala – Loss of fear, impaired emotion

recognition in faces, impaired recognition of social emotions, impaired memory for emotional material

• Hippocampus – Amnesia (anterograde), failure to remember spatial layouts/landmarks– H.M.– shows damage in Alzheimer’s

Question?• The limbic system is involved in

controlling basic drives important for our survival as a species, feeding and reproducing. But it is also instrumental to the experience of fear and aggression.

• What do you make of the fact that these two particular emotions (unlike say, happiness or melancholy) are controlled by the same system that helps ensure our survival?

• What does Memory have to do with this?

Cerebral Cortex• Fabric of interconnected neural cells that

covers the cerebral hemispheres• Cortex=bark• Ultimate control and information processing

structure• Higher Functions/Newer neural networks• 85% of brain weight• Axons project down into brain, connecting it

with other brain structures

Cerebral Cortex• Two halves, four lobes, separated by

Fissures– Frontal lobe

• Judgement, planning, Decision-making, inhibition, personality• Motor cortex

– Parietal lobe• Sensory cortex (touch)• Math, spatial reasoning

– Temporal lobe• Auditory cortex, visual memory language

– Occipital lobe – all vision• Visual cortex

– Association areas throughout

Two Cerebral Hemispheres

• Contralateral arrangement – the left hemisphere receives inputs from and controls the right side of the body and vice versa

• Work together on many functions but can also simultaneously carry out different functions with minimal duplication of effort

• Corpus callosum– Thick band of nerve fibers connects the two

hemispheres

Functions of the Cortex

Functions of the CortexPrimary Visual Cortex• Receives and

processes visual info from the eyes

Visual Association Areas•Interpret visual signals and recognize form, color, movement

Functions of the cortex

Primary Auditory Cortex• Receives/processes

auditory information from the ears (sound)

Auditory Association Areas• Interpret sound• Language comprehension

(Wernicke’s area)

Primary Somatosensory cortex• Processes sensory info (touch) from body

Sensory Association AreaReceives input from primary and secondary sensory cortex and is involved in complex associations

Motor and Sensory Cortex

Functions of the CortexPrimary Motor Cortex• Origin of most of the corticospinal tract meaning, projects to the

spine so it can send motor signals down to various body parts and tell them to move.

• Specific movements tend to be represented rather than specific muscles.

• Also projects to thalamus and basal ganglion

Association Areas = Premotor Cortex• In front of the motor strip• Receives many of the same

connections as the motor cortex but most of its outputs go to the motor cortex

• Responsible for more complex movements

Association Areas of the Cortex• The ¾ of the cortex, across all four lobes not devoted to

sensory or muscle activity.• Interpret, integrate information processed by the sensory

areas, link sensory inputs with stored memories • In the frontal lobesenable judgment, planning, processing memories, inhibitions, and personality• In parietal lobesenable mathematicaland spatial reasoning• In right temporal enable facial Recognition.

Association AreasMore intelligent animals have increased “uncommitted” or association areas of the cortex.

Association Area Locations

Association Area Functions

Language cortical AreasLeft Hemisphere

• Broca’s Area– Pierre Paul Broca– Language production

• Broca’s aphasia: - Language Comprehension unaffectedbut language production is impaired or lost speech non-fluent, labored, aware when they say something wronghttp://www.youtube.com/watch?v=1aplTvEQ6ew&feature=related

Language Cortical AreasWernicke’s Area - Carl Wernicke - Understanding of written and spoken language

Wernicke’s Aphasia - Language comprehension is affected - Speech retains normal rhythm and syntax but is largely meaninglesshttp://www.youtube.com/watch?v=dKTdMV6cOZw&feature=related

Specialization and Integration• Complex human behaviors involve multiple

specialized areas and association areas working together.

Our Divided Brain

Corpus Callosum

Brain Lateralization

One Brain or Two?

Gazzaniga, M. S. (1967)

Left & Right Functions

Hemispheric SpecializationLeft brain • Good with literal

interpretations of language

• More active when a person is deliberating

• More “rational”

Right Brain• Making inferences about

words and modulating speech to convey meaning

• Orchestrates sense of self• Better with quick, intuitive

responses• Perceives objects better• More involved in emotion,

spatial reasoning

Divided ConsciousnessThe Right hemisphere is nonverbal but it can still make itself understood

Split Brain Patientshttp://www.youtube.com/watch?v=aCv4K5aStdU• With the corpus

callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.

• Left hemisphere – language, logic, laughter– Logical, verbal, sequential– Positive emotions

• Right hemisphere – – Spatial, emotional intuition,

music, “big picture”

(People with damage to the left hemisphere may lose their ability to speak but not sing (a right hemisphere task). They can redevelop language by learning to sing everything they want to say!)

DDD

D

D

D

D

D

D

D D D D

D

D

DD

D

D

DD

DD

1. What is the large composite letter?H (right brain active, “big picture”)

2. What is the small component letter?D (left brain active)

Which face looks happier to you?

FORK SPOON• When asked to SAY what they saw, they

answer __________________– (spoon)

• When asked to pick up what they saw with their left hand, they will pick up a ______.– (fork)

A split brain patient has a picture of a knife flashed to her left hemisphere and that of a fork to her right hemisphere. She will be able to

A. identify the fork using her left hand.B. identify the knife using her left hand.C. identify the knife using either hand.D. identify the fork using either hand.

Answer: A

Dr. J briefly flashed a picture of a key in the right visual field of a split-brain patient. The patient could probably

A. verbally report that a key was seenB. write the word “key” using her left handC. draw a picture of a key using the left handD. none of the above

What will happen as a neurosurgeon sedates the entire right cerebral hemisphere of a patient who is asked to count aloud with both arms extended upward?

A. her left arm will fall and she will become speechless

B. her right arm will fall and she will become speechless

C. her left arm will fall and she will continue counting

D. her right arm will fall and she will continue counting

• People should typically recognize familiar words more rapidly when spoken into their __________ ear.Answer: right

• People should typically recognize familiar melodies more rapidly when played into their ________ ear.Answer: left

Note: Not all people have such simple separations between hemispheres. Women (more than men) tend to use both sides of their brain when interpreting language.

Unilateral Neglect• After damage to the right

hemisphere, some patients exhibit indifference to the left side of their world – “hemi-neglect”

• The neglect can be multimodal, affecting auditory, visual, somatosensory

• Related to the right side’s involvement in spatial reasoning and sense of self. Damage to the left side does not have this effect.

Theories of lateralization – Why?

• May increase neural capacity• Dominance by one side prevents the

simultaneous initiation of incompatible responses/actions

• May increase capacity for parallel processing in the two hemispheres– But then why do we display a consistent

preference at the population level? Shouldn’t there be an equal ratio of left to right side preference?

Theories of Lateralization – How?

• Lateral birth position and neonatal head orientation preference are both predictors of handedness

• Lateral asymmetry in the uterine environment and maternal anatomy my lead to the left side of the uterus being more “favorable” for fetal positioning.– But then why would we have any lefties at all?

Handedness• Lefties are more likely than righties to process language with

either the right hemisphere or with both hemisphere. 96% of righties process language primarily with left hemisphere.

• Left-handedness is more common among musicians, mathematicians, pro baseball players, architects and artists.

• Do you think there is a connection?

Handedness• In the past, left-handedness was stigmatized in our society

and as children, lefties were “trained” to use their right hands.

• Because most things are made for righties, lefties are more susceptible to accidental injury.• On average, leftieslive 9 years than people who are right-handed

Handedness• Given these facts about left-handedness as well as what you have

learned about research methods, what do you make of this graph?

The Brain’s Plasticity

• Plasticity occurs during normal brain development but it is also the brain’s ability to modify itself after injury or loss of function– Phantom limb– Enhanced peripheral vision in deaf people

• The brain is sculpted by our genes and by a person’s environment and experiences

• Neural tissue reorganizes and in some cases regenerates (neurogenesis)

Plasticity – the brain’s capacity to reorganize

• Blind person’s sensory cortex for their fingers may expand.

• In blind people, the visual cortex is activated when they read Braille.

• In deaf people, some visual information is process in the temporal lobe.

• Hemispherectomy – removal of an entire hemisphere of cerebral cortex; if surgery performed when young, other hemisphere takes over

Plasticity

• Slow destruction of Broca’s area by tumors leaves speech relatively intact. Its function shifts to nearby areas.

domestic cats have… - thicker skulls and smaller brains - less cone photoreceptors in their retina than wild cats

wild cats tend to have…. - a greater total density of ganglion cells in their retinas

The total neuron number and volume of the lateral geniculate nucleus (LGN) is larger in wild cats than in the domestic catThe actual cell size of the neurons in the LGN is the same in both wild and domestic cats