Brain Structure and Function

“If the human brain were so simple that we could understand it, we would be so simple that we couldn’t” -Emerson Pugh, The Biological Origin of Human Values (1977)

Phineas Gage September 13 th, 1848 Phineas 25 years old Rutland & Burlington Railroad, Cavendish, VT Paving the way for new RR tracks “Tamping Iron” –1.25in x 3ft

Accident –Quick Recovery Months later: “No longer Gage” –Before: capable, efficient, best foreman, well-balanced mind –After: extravagant, anti-social, liar, grossly profane Stint with P.T Barnum Died 12 years later Watch Clip Phineas Gage

Evolution of the Brain Reptilian  Paleomammalian  Neomammalian

The Hindbrain Brainstem –responsible for automatic survival functions Medulla –Involved in vital functions and controls heartbeat, blood pressure and breathing

The Pons -located in the front of the medulla and is involved in regulating body movement, attention, sleep, and alertness Cerebellum -looks like the larger part of the brain, the cerebrum (under which it rests). -Involved in balance and coordination.

BRAINSTEM  Heart rate and breathing CEREBELLUM  Coordination and balance Parts of the Brain amygdala pituitary hippocampus THALAMUS  Relays messages

The Cerebellum again –helps coordinate voluntary movement and balance

The Midbrain: Reticular Formation Widespread connections Arousal of the brain as a whole Reticular activating system (RAS) Maintains consciousness and alertness Functions in sleep and arousal from sleep

The Forebrain Four key parts of the Forebrain: –The Thalamus –The Hypothalamus –The Limbic system -- The Cerebrum

The Limbic System Hypothalamus, 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 Brain Thalamus –the brain’s sensory switchboard, located on top of the brainstem –it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

 Hypothalamus  neural structure lying below (hypo) the thalamus; directs several maintenance activities  eating  drinking  body temperature  Storage of nutrients  helps govern the endocrine system via the pituitary gland  linked to emotion  Also involved in hunger, thirst, sexual behavior caring for offspring.

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

Charles Whitman August 1 st, 1966

Cerebrum The crowing glory of the brain! Only in human beings does the cerebrum make up such a large part of the brain. The surface of the cerebrum is made up of wrinkled ridges and valleys called the cerebral cortex.

The Cerebral Cortex Cerebral Cortex –the body’s ultimate control and information processing center –The cerebral cortex makes up the main information processing lobes of the brain.

The Corpus Callosum The structure that connects the two hemispheres of the brain is called the corpus callosum

The lobes of the cerebral hemispheres

Planning, decision making speech Sensory Auditory Vision

The Cerebral Cortex Frontal Lobes –involved in speaking and muscle movements and in making plans and judgments –the “executive” Parietal Lobes –include the sensory cortex

The Cerebral Cortex Occipital Lobes –include the visual areas, which receive visual information from the opposite visual field Temporal Lobes –include the auditory areas, each of which receives auditory information primarily from the opposite ear

The Cerebral Cortex Frontal (Forehead to top)  Motor Cortex Parietal (Top to rear)  Sensory Cortex Occipital (Back)  Visual Cortex Temporal (Above ears)  Auditory Cortex

Motor/Sensory Cortex Contralateral Homunculus Unequal representation

Sensory Areas – Sensory Homunculus Figure 13.10

The Cerebral Cortex  Aphasia  impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding) –see clips  Broca’s Area  an area of the left frontal lobe that directs the muscle movements involved in speech  Wernicke’s Area  an area of the left temporal lobe involved in language comprehension and expression

Language Areas Broca  Expression Wernicke  Comprehension and reception Aphasias LEFT HEMISPHERE

Paul Broca [1800s] Suggested localization

Techniques to examine functions of the brain 1. Remove part of the brain & see what effect it has on behavior 2. Examine humans who have suffered brain damage

3. Stimulate the brain 4. Record brain activity

How? 1. Electroencephalogram (EEG) –A device that records the electric activity of the brain 2. Cat Scans --a moving ring passes X-ray beams around and through the head. Radiation is measured by computers to piece together three- dimensional view of the brain

3. MRIs (magnetic resonance imaging) --a person lies in a very powerful magnetic field. Then radio waves give off extra energy. That energy Is measured at different angles and then those images are transmitted to a computer. *More clear than a CAT scan.

4. PET scans,(positron emissional tomography) and fMRIs (functional MRIs) enable researchers to catch the brain at work. In PET scans a person is injected with radioactive sugar and as the sugar reaches the brain, more of it is used in areas of the brain that is more active.

5. fMRIs can show which parts of the brain are more active when we perform different activities such as listening to music, playing chess, using language, or working out a math problem

Brain Lateralization

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

Hemispheric Specialization LEFT Symbolic thinking (Language) Detail Literal meaning RIGHT Spatial perception Overall picture Context, metaphor

Contra-lateral division of labor Right hemisphere controls left side of body and visual field Left hemisphere controls right side of body and visual field

Split Brain Patients Epileptic patients had corpus callosum cut to reduce seizures in the brain Lives largely unaffected, seizures reduced Affected abilities related to naming objects in the left visual field

Brain Plasticity

The ability of the brain to reorganize neural pathways based on new experiences Persistent functional changes in the brain represent new knowledge Age dependent component Brain injuries

Environmental influences on neuroplasticity Impoverished environment Enriched environment

Sensation and Perception

Sensation The process by which the central nervous system receives input from the environment via sensory neurons Bottom up processing

Perception The process by which the brain interprets and organizes sensory information Top-down processing

The psychophysics of sensation Absolute threshold  the minimum stimulation needed to detect a stimulus with 50% accuracy Subliminal stimulation  below the absolute threshold for conscious awareness –May affect behavior without conscious awareness Sensory adaptation/habituation  diminished sensitivity to an unchanging stimulus

The five major senses Vision – electromagnetic –Occipital lobe Hearing – mechanical –Temporal lobe Touch – mechanical –Sensory cortex Taste – chemical –Gustatory insular cortex Smell – chemical –Olfactory bulb –Orbitofrontal cortex –Vomeronasal organ?

The sixth sense Vestibular  balance and motion –Inner ear Proprioceptive  relative position of body parts –Parietal lobe Temperature  heat –Thermoreceptors throughout the body, sensory cortex Nociception  pain –Nociceptors throughout the body, sensory cortex And the seventh…and eighth…and ninth…

Thresholds of the five major senses

The Retina The retina at the back of the eye is actually part of the brain! Rods – brightness Cones – color