The BrainModule 4

• Older brain structures• Cerebral Cortex• Our divided brain

http://www.ucdmc.ucdavis.edu/welcome/features/20071017_Medicine_whitematter/Photos/head_and_brain.jpg

The Brain

“The brain enables the mind – seeing, hearing, smelling, feeling, remembering, thinking, speaking, dreaming.”

When we use our brain to think, we are firing millions of synapses and releasing millions more of neurotransmitters.

“…the mind is what the brain does.” So how are the functions of our mind connected

to our brain?

Older Brain Structures• The ratio of the brain and the body weight does not

reveal intelligence levels.• The brains of primitive vertebrates, such as sharks,

regulate survival functions such as breathing, resting and feeding, while the brain of lower mammals like rodents, enables emotions and greater memory. In advanced mammals, such as humans, the brain enables foresight and can process more information.

• Older brain structures include the brainstem, thalamus, reticular formation, cerebellum and limbic system (which consists of the hippocampus, amygdala and hypothalamus).

The Brain Stem• Responsible for automatic survival functions.• It is a crossover point: the brain stem also

connects a side of the brain with the body’s opposite side.

• Location: it begins where the spinal cord swells slightly after entering the skull. The slight swelling is the medulla.

• The medulla controls heartbeat and breathing.• Just above the medulla is the pons –

coordinates movements.

• If a cat’s brainstem is severed from the rest of the brain above it, the cat will still be able to breathe and live—and even run, climb, and groom. However, because it is now cut off from the higher processing regions of the brain, the cat will not purposefully run or climb to get food.

• The reticular formation is a nerve network in the brain stem (between your ears) which controls arousal. It extends from the spinal cord up to the thalamus. It’s job is to filter the incoming stimuli.

• Giuseppe Moruzzi and Horace Magoun discovered that the reticular formation was used in arousal. They performed an experiment where when a sleeping cat’s reticular formation was stimulated it produced an instantly awake and alert animal. When the reticular formation was severed from the higher regions of the brain (without damaging the sensory pathways) the cat lapsed into a coma from which it never awakened.

http://bionoid.net/images/research/brainstem.gif

Thalamus

• Receives information from 4 of the 5 senses (from those of sight ,hearing, tasting and touching). Smell is the exception.

• Located on top of the brain stem.• Directs messages to the sensory receiving

areas in the cortex and transmits replies to the cerebellum and medulla.

• It is a hub through which traffic passes en route to various destinations.

http://www.freewebs.com/garyosborn/Thalamus%201.jpg

Cerebellum

• Aka the Little Brain• Enables nonverbal learning and memories• Judges time, emotions, recognizes sounds and

textures• Coordinates voluntary movement• It is part of the “Older brain” and functions

without conscious effort

http://www.intropsych.com/ch02_human_nervous_system/02cerebellum.jpg

The Limbic System• Is composed of the hippocampus, amygdala and

hypothalamus.• It is located beneath the cerebral hemispheres and is

associated with emotions and drives.• Hippocampus processes memory• Amygdala influences aggression and fear.• Heinrick Kluver and Paul Bucy lesioned part of a

monkey’s amygdala. The monkey, which was originally ill-tempered, became less fierce and very mellow.

• Aggression and fear can also be triggered in other parts of the brain, not just the amygdala.

• The hypothalamus is a neural structure which lies just below (hypo means below) the thalamus.

• It helps govern the endocrine system: the pituitary gland is controlled by the hypothalamus.

• It directs several maintenance activities such as eating, drinking and body temperature.

• It is also linked to emotions and reward.

http://www.flyfishingdevon.co.uk/salmon/year2/aggression/amygdala-hippocampus.jpg

• The hypothalamus also monitors blood chemistry and takes orders from other parts of the brain. Ex: thinking about sex can stimulate your hypothalamus to secrete hormones.

• Olds and Milner discovered through their experiment used on rats that the hypothalamus provides pleasurable reward

• Reward centers – do anything to get that stimulation• Olds and Milner did many experiments regarding the

reward center. Electrodes would be placed on the hypothalamus region and the rats were allowed to trigger the stimulation as they saw fit. The rats would sometimes press the lever (that allowed the stimulation) up to 7000 times per hour—until they dropped from exhaustion.

• In animals, the reward centers are essential for survival since they do not think about what they need to survive.

• Reward Deficiency Syndrome- Explains addiction to alcohol, drugs and binge eating. It is a genetically disposed deficiency in natural brain systems for pleasures

Show clip: Brain Mechanisms of Pleasure & Addictionhttp://www.youtube.com/watch?v=de_b7k9kQp0

http://www.medicalartlibrary.com/images/thalamus-hypothalamus.jpg

• Remember:• Olds and Milner discovered through their experiment used on

rats that the hypothalamus provides pleasurable reward• Reward centers- do anything to get that stimulation• Further studies and research indicate that laughter, beautiful

faces, food and money stimulate the reward centers just as well as meth, heroin, cocaine and other addictive drugs.

• The reward centers, include the areas of the brain known as the nucleus accumbens, amygdala, hypothalamus, orbitofrontal cortex and ventral tegmentum. They are considered to be evolutionary holdovers from reptiles and have been linked to a range of psychological disorders from addiction to depression.

Cerebral Cortex

• Enables perception, thinking and speaking• Controls information processing. • Humans have a larger cerebral cortex for

thinking and perception• Why is it that when we look at a picture of the

brain, it looks “wrinkled”? Why does it have all of those indentations in it?

http://www.morphonix.com/software/education/science/brain/game/specimens/images/cerebral_cortex.gif

Structure of the Cortex• 80% of the brain’s weight is taken up by the left and

right cerebellum• Filled with axon connection between Brain’s surface

and it’s other regions• Cerebral Cortex contains over 20-23 billion nerve

cells• Gilal cells – guide to neural connections (provides

nutrients and insulates myelin, mops up ions and neurotransmitters)

• The proportion of gilal and nerve cells are higher in more complex animals

• Each brain hemisphere is divided into four lobes, separated by fissures (folds), the lobes include the frontal lobe, parietal lobe, occipital lobe and the temporal lobe.

• The temporal lobes are above your ears, the occipital lobes are at the back of your head, the parietal lobes are the top of the brain in back of the frontal lobe.

http://www.newscientist.com/data/images/archive/2222/22224201.jpg

Functions of the cortex

• Otfrid Foerstred and Wilder Penfield mapped the motor cortex, according to the body’s parts and which region it controls. They found that body areas requiring precise control, such as the fingers and mouth, occupied the greatest amount of cortical space. (see figure 14.3, p. 54)

• Jose Delgado stimulated a spot on the left cortex and discovered that the right fist would clench.

• Functions taken care of by the cortex are: motor functions, sensory functions, association areas and language.

Sensory Functions

• In front of the parietal lobes, the sensory functions are located.

• It registers, processes body touch and movement sensations.

• If a region is more sensitive, it means that there is a larger sensory cortex for their regions.

• Occipital lobes receives visual information• Temporal lobe processes hearing through auditory

areas- active during phantom ringing and auditory hallucinations.

• Association areas integrates information and associates various sensory inputs with stored memories

• Frontal lobes- judge, plan and process new memories. Can have intact memory, score high on intelligence tests, and be able to bake a cake—yet be unable to plan ahead to begin baking the cake for someone’s birthday party. Damage can alter personality also.

• Phineas Gage- frontal lobes were damaged through an accident, personality changed, became more dishonest and immoral.

• http://www.youtube.com/watch?v=PCXOrNc99yY

• Parietal lobe is used for mathematical and spatial reasoning

• The right temporal lobe enables the association and recognition of faces

• Memory and language come from different areas of the brain.

Language• Language is controlled in the left hemisphere.• Aphasia- impaired use of language: some cannot read yet

speak; cannot speak yet read, cannot read yet write, cannot speak yet sing; cannot read letters yet can read numbers….

• Angular gyrus- receives visual information from visual areas, recodes it into auditory form.

• Norman Geschwind explained how we use language through the processes below.– words first are registered in the visual area– Visual image is relayed to the angular gyrus, transforms

words to auditory tone– Received and understood in the Wernicke's area– Sent to Brocca’s area– Brocca’s area controls the motor cortex, creates

pronounced words

• Damages to the angular gyrus causes a person to not to be able to read.

• Brocca’s area- area of the frontal lobe. Damage to Brocca’s area disrupts speaking. It causes someone not to be able to speak words, yet allows them to sing familiar songs and comprehend speech.

• Wernicke’s area- controls language reception. Damage causes people to talk senselessly. It disrupts understanding.

The Brain’s Plasticity

• Plasticity is at a higher rate when we are younger.• When damage to the brain occurs, most neurons

cannot regenerate, however some can reorganize themselves.

• Plasticity is the brain’s ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience.

• Example: blindness or deafness makes unused brain areas available for other uses.

• If a blind person uses one finger to read Braille, the brain area dedicated to that finger expands as the sense of touch invades the visual cortex that normally allows people to see. Temporarily “knock-out” or block that visual cortex (even though a blind person cannot see) and a life-long blind person will make more errors on a language task.

• If you lose a finger, the sensory cortex that had received input from that finger will now receive input from the adjacent fingers, which will now become more sensitive.

• If any body part is amputated, sensory fibers that terminate on adjacent areas of the sensory cortex may invade the brain tissue that’s no longer receiving sensory input (phantom pains/sensations)

• Brain modification mostly occurs as reorganization, however, in some instances we can generate new brain cells but only in the older brain regions.

• Master stem cells that can develop into a type of brain cell has also been found in the human embryo.

Show clip: Brain’s plasticity – http://www.youtube.com/watch?v=TSu9HGnlMV0

Our Divided Brain

• What is a split brain, and what does it reveal about brain functioning?

• 2 Los Angeles neurosurgeons theorized that epileptic seizures were caused by an amplification of abnormal brain activity reverberating between the two cerebral hemispheres.

• What would happen if they severed the corpus callosum connecting the two hemispheres?

Split Brains

• What came of severing the corpus callosum is what we term the split brain.

• Split brain patients keep their personality and intellect intact. However, their processing of stimuli is very different.

• Because the “communication lines” (the corpus callosum) are severed, processing of information is startling.

Split Brains

• In an early experiment patients were asked to stare at a dot on a screen.

• Then the words HE • ART were flashed on the screen.

• HE appeared in the left visual field and ART appeared in the right visual field.

• Remember, the right hemisphere of the brain controls the left side of the body and the left hemisphere controls the right side of the body.

Split Brains

• When patients are asked to say what they had seen on the screen they report “ART”. This is because it was in the right visual field and was processed in the left hemisphere where language processing occurs.

• Yet when they are asked to point to what they saw on the screen, when pointing with the left hand, they point to “HE”. This is because “HE” was in the left visual field and was processed by the right hemisphere which controls the left hand.

Split Brains

• Also when a picture of a spoon was shown only to the right hemisphere (left visual field), patients could not report what they had seen.

• Yet when given items to feel with their left hand, they were able to pick out the spoon as the item that they had seen.

• In split brain patients, the left hemisphere is the “interpreter” that constructs explanations of our behavior.

Split Brains• For example, if a patient follows an order sent to

the right hemisphere, such as “walk”, the left hemisphere will do more than just identify the command “walk”, it will interpret with an explanation such as “I’m going to the lobby to get a coke.”

• So the left hemisphere is always coming up with explanations as to a split brain patient’s behavior.

Show clip: Severed Corpus Callosum – http://www.youtube.com/watch?v=lfGwsAdS9Dc

The Intact Brain

• The left hemisphere is good at making quick, literal interpretations of language.

• The right hemisphere is good at making inferences (the deriving of a conclusion by reasoning; deduction)

• When flashed the word “foot”, the left hemisphere is quick to associate the word heel with it. However, when given the words “foot, cry, glass”, the right hemisphere is quick to infer (by way of deductive reasoning) the word “cut”.

The Intact Brain

• The right hemisphere also modulates our speech (although language originates from the left).

• For example when a patient who suffered stroke damage to the right side of the brain reported “I understand words, but I’m missing the subtleties.”

• When saying something like, “What’s that in the road ahead?” That patient may interpret that as, “What’s that in the road, a head?”

The Intact Brain

• The right hemisphere also surpasses the ability of the left in other areas such as copying drawings, recognizing faces, perceiving differences, perceiving emotion, and expressing emotion through the more expressive left side of the face. (Ha! Our “left face” is more expressive than our “right face”! You’ll be checking it out in the mirror now….LOL).

The Intact Brain

• Damage to the right hemisphere more greatly disrupts emotion processing and social conduct.

• The two hemispheres put together keep us in harmony and make us a whole working unit.

The Murderer’s Brain

• http://www.youtube.com/watch?v=agPUoKB8eEk

• Show Clip 4 http://www.youtube.com/watch?v=agPUoKB8eEk

• If time permits….if not: on your own.