Brain Structure and Function

If the human brain were so simple that we could understand it, we would be so simple that we couldnt

-Emerson Pugh, The Biological Origin of Human Values (1977)

Phineas GageSeptember 13th, 1848Phineas 25 years old Rutland & Burlington Railroad, Cavendish, VTPaving the way for new RR tracksTamping Iron1.25in x 3ft

Phineas GageAccidentQuick RecoveryMonths later: No longer GageBefore: capable, efficient, best foreman, well-balanced mindAfter: extravagant, anti-social, liar, grossly profaneStint with P.T BarnumDied 12 years laterWatch Clip

Evolution of the BrainReptilian Paleomammalian Neomammalian

The BrainBrainstem responsible for automatic survival functionsMedullacontrols heartbeat and breathing

Parts of the BrainBRAINSTEM Heart rate and breathing

CEREBELLUM Coordinationand balanceamygdalapituitaryhippocampusTHALAMUS Relays messages

Reticular FormationWidespread connections Arousal of the brain as a wholeReticular activating system (RAS) Maintains consciousness and alertnessFunctions in sleep and arousal from sleep

The Cerebellum

helps coordinate voluntary movement and balance

The Limbic SystemHypothalamus, pituitary, amygdala, and hippocampus all deal with basic drives, emotions, and memory

Hippocampus Memory processing

Amygdala Aggression (fight) and fear (flight)

Hypothalamus Hunger, thirst, body temperature, pleasure; regulates pituitary gland (hormones)

The Limbic SystemHypothalamusneural structure lying below (hypo) the thalamus; directs several maintenance activitieseatingdrinkingbody temperaturehelps govern the endocrine system via the pituitary glandlinked to emotion(show video)

The Limbic SystemShow self stimulation clip

The Limbic SystemAmygdala two almond-shaped neural clusters that are components of the limbic system and are linked to emotion and fear

Charles WhitmanAugust 1st, 1966

The BrainThalamusthe brains sensory switchboard, located on top of the brainstemit directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

The Cerebral CortexCerebral Cortex the bodys ultimate control and information processing center

The lobes of the cerebral hemispheres

The lobes of the cerebral hemispheresPlanning, decision making speechSensoryAuditoryVision

The Cerebral CortexFrontal Lobesinvolved in speaking and muscle movements and in making plans and judgmentsthe executiveParietal Lobes include the sensory cortex

The Cerebral CortexOccipital Lobes include the visual areas, which receive visual information from the opposite visual fieldTemporal Lobes include the auditory areas, each of which receives auditory information primarily from the opposite ear

The Cerebral CortexFrontal (Forehead to top) Motor CortexParietal (Top to rear) Sensory CortexOccipital (Back) Visual CortexTemporal (Above ears) Auditory Cortex

Motor/Sensory CortexContralateralHomunculusUnequal representation

Sensory Areas Sensory HomunculusFigure 13.10

The Cerebral CortexAphasiaimpairment of language, usually caused by left hemisphere damage either to Brocas area (impairing speaking) or to Wernickes area (impairing understanding) see clipsBrocas Area an area of the left frontal lobe that directs the muscle movements involved in speechWernickes Area an area of the left temporal lobe involved in language comprehension and expression

Language AreasBroca ExpressionWernicke Comprehensionand receptionAphasias

LEFT HEMISPHERE

Paul Broca [1800s] Suggested localization

Techniques to examine functions of the brain1. Remove part of the brain & see what effect it has on behavior2. Examine humans who have suffered brain damage

3. Stimulate the brain4. Record brain activity

Brain Lateralization

Our Divided BrainsCorpus collosum large bundle of neural fibers (myelinated axons, or white matter) connecting the two hemispheres

Hemispheric SpecializationLEFT

Symbolic thinking(Language)DetailLiteral meaning

RIGHT

Spatial perceptionOverall pictureContext, metaphor

Contra-lateral division of laborRight hemisphere controls left side of body and visual field

Left hemisphere controls right side of body and visual field

Split Brain PatientsEpileptic patients had corpus callosum cut to reduce seizures in the brainLives largely unaffected, seizures reducedAffected abilities related to naming objects in the left visual field

Brain Plasticity

Brain PlasticityThe ability of the brain to reorganize neural pathways based on new experiencesPersistent functional changes in the brain represent new knowledgeAge dependent componentBrain injuries

Environmental influences on neuroplasticity

Sensation and Perception

SensationThe process by which the central nervous system receives input from the environment via sensory neuronsBottom up processing

PerceptionThe process by which the brain interprets and organizes sensory informationTop-down processing

The psychophysics of sensationAbsolute threshold the minimum stimulation needed to detect a stimulus with 50% accuracySubliminal stimulation below the absolute threshold for conscious awarenessMay affect behavior without conscious awarenessSensory adaptation/habituation diminished sensitivity to an unchanging stimulus

The five major sensesVision electromagneticOccipital lobeHearing mechanicalTemporal lobeTouch mechanicalSensory cortexTaste chemicalGustatory insular cortex Smell chemicalOlfactory bulbOrbitofrontal cortexVomeronasal organ?

The sixth senseVestibular balance and motionInner earProprioceptive relative position of body partsParietal lobeTemperature heatThermoreceptors throughout the body, sensory cortexNociception painNociceptors throughout the body, sensory cortexAnd the seventhand eighthand ninth

Thresholds of the five major senses

The RetinaThe retina at the back of the eye is actually part of the brain!

Rods brightnessCones color

Brainstem the central core of the brain, beginning where the spinal cord swells as it enters the skullresponsible for automatic survival functionsMedulla [muh-DUL-uh] base of the brainstemcontrols heartbeat and breathingBrainstem, controls for heartbeat and breathingswell is called the medulla.Vital Functions : Breathing Blood circulationSwallowingUrination

Reticular formation The brainstem also contains networks of neurons,known collectively as the reticular formation, that project up into the cerebralcortex and basal ganglia and affect general arousal. The reticular formation is alsoinvolved in inducing and terminating the different stages of sleep. The autonomyof the brain stem can be dramatically illustrated by severing an animals brainstem from the entire brain above it, including its entire cerebral cortex. Cats thatreceive this treatment can still walk around and direct attacks at noises; if theythen find themselves holding on to food, they will eat it. Some cases have been reportedof humans born without cerebral cortices, and their behaviors are extremelybasic and reflexive. Such infants tend not to develop normally and also donot tend to survivethe little brain attached to the rear of the brainstem, cerebellum actually means little brain.Also helps involved in nonverbal learning and memory (will discuss in later chapters), if you injured your cerebellum you would have difficulty walking, keeping your balance, shaking hands.

Note: these lower brain functions occur without any conscious effort.

The limbic system is an older term for a group of subcortical structures dealing with basic drives, emotions and memoryThe diencefpahlon (or between brain) the hypothalamus and thalamusThe hippocampus and amygdalaThe basal gangliaThe dreebral cortexIn hypothalamus, the rat readily crosses an electrified grid, accepting the painful shocks to press a lever that sends electrical impulses to its pleasure centersTied up to eating, drinking, addiction, sex???

Researchers began to find evidence that the amygdala was involved in the emotion of fear in the late 1930s. Monkeys with damage to the brain cluster and surrounding areas had a dramatic drop of fearfulness.

Later, studies showed that rats with targeted amygdala damage would snuggle up to cats. But if you electrically stimulate the amygdala in a normally placid domestic animal such as a cat, the cat prepares to attach by hissing, arching its back, pupils dilate, and its hair stands up on end.

Accumulating revelations about this fear system led researchers recently to examine the human brain's response to fear with imaging studies. One study showed that pictures of frightening faces initiate a quick rise and fall of activity in the amygdala.

In the future, scientists believe imaging techniques may help determine the course of treatment for disorders involving a malfunction in fear processing. For example, a person with an extreme fear of germs who continuously washes, known as an obsessive-compulsive disorder, He killed his wife and mother before going to the top of the university tower and opened fire on persons crossing the campus and on nearby streets. He ended up killing 16 people and wounded 31, before being killed by police officers. The shooting spree lasted 96 minutes.

Post-mortem revealed a brain tumor near his amygdala.

When you see similar cases in the news of people doing horrendous things (eg, Andrea Yates), whats your reaction? What do you think about the individual? Psychology has changed the way we view such tragediesnow were more likely to see evil as pathological. Thalamus- located on top of the brainstem, a joined pair of egg-shaped structures, Receives sensory info, routes it to higher brain regions that deal with seeing, tasting, touching etc. directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

the intricate fabric of interconnected neural cells that covers the cerebral hemispheres

Figure 4.14 page 110The lobes of the cerebral hemispheres: parietal, occipital, temporal, and frontal.

Figure 4.14 page 110The lobes of the cerebral hemispheres: parietal, occipital, temporal, and frontal.

The cerebral cortex is organized or divided into 4 regions or lobes.

frontal lobe- behind your forehead, executive functions. -parietal lobe- at the top and to the rear of the headOccipital lobe- at the back of your head-Temporal lobe- just above your ears; receives auditory info primarily from the opposite ear.The lobes are separated by prominent fissures or folds. Important to note that although each lobe carries out different functions, many of our functions require the interplay or involvement of several lobes.

Temporal lobes -- each of which receives auditory information primarily from the opposite earObserved Tan (named so because he could only utter the sound tan-tan)

In 1861 Broca did a post-mortem showing that Tan had a superficial lesion in the left frontal lobe of his brain, in exactly the area that controlled speech.

Largely on the basis of this case, Broca postulated that expressive language function was located in the posterior left frontal lobe ("Broca's Area").