The Structures of the Brain

1. The Structures of the Brain Mod 4 Part 1

2. The Tools of Discovery • How do neuroscientists explore the connection among brain, mind, and behavior? • Lesions (cutting) • Can remove damaged tissue without disturbing surrounding tissue. • Can selectively cut tissue and gauge response • Measurement of electrical impulses • Color Representations of Brain injury • Clinical observations • Injury • Disease • Manipulating the Brain • Electrical, chemical, or magnetic stimulation • Legion in a rat’s hypothalamus causes itself to starv to death (will not eat) • Electroencephalogram (EEG) • Measures surface electrical activity • Filtering out background allows scientist to see response to stimulus.

3. Brain imaging • Computed Tomography Scan • X-ray photographs of cross sections • Can indicate damage • Positron Emission Tomography • Consumption of glucose • Radioactive glucose lights up on scan • Different area lights up when someone says the name of an animal vs. when someone says the name of a tool (Martin et al 1996) • Magnetic Resonance Imaging • Strong magnetic field depolarizes atoms briefly • Detailed picture of soft tissues • Functional MRI (fMRI) • Tracks oxygen • Findings • Similar brain areas involved in reading and remembering words (Posner and Raichle1998) • Larger than average neural area of the left brain in musicians with perfect pitch (Schlaug et al 1995) • If second language is learned simultaneously with first, it is stored in the same area. If it is learned later, it is stored in a different area. (Kim et al 1997) • Men use only left side of brain for rhyming tasks, women use both sides (Shaywitz et al 1995)

4. Lower-Level Brain Structures • What are the lower level brain structures and what are their functions? • Size to body weight matters (some) • Wrinkles matter more • The Brainstem • Medulla • Controls the heartbeat and breathing • Cat can live with only a medulla (Klemm 1990) • Autonomic nervous system hub • Reticular formation • Finger shaped network that connects spinal chord to thalamus • Electronically stimulating reticular formation of cat makes the cat wide awake and alert (Magoun and Moruzzi 1949) • Severing cat’s reticular formation causes irreversible coma (Magoun) • Thalamus • Sensory hub • Receives sensory information and sends to appropriate brain part • Controls occillations (Llinas and Ribary 2001)

5. The Cerebellum and Limbic System • Cerebellum • Little brain • Processes things outside of our awareness • Balance • Refined motor skills • Manages life-sustaining functions • Limbic system • Border between cerebrum and lower structures • Hippocampus: essential to memory processing • Links to emotions and drives • Amygdala • Almond shaped neural clusters influence aggression and fear • Can make ill-tempered monkey meek (Kluver 1939) • Role in rage, fear, and perception of anger (Anderson and Phelps 2000, Poremba and Gabriel 2001) • Lesioning amygdala shows varied response in humans (Mark and Ervin 1970, Valenstein 1986) • Hypothalamus • Hunger, thirst, body temperature, sexual behavior • Controls pituitary gland • Reward centers (Olds and Milner 1954, Olds 1975) • Rat experiments with reward centers (Olds 1958) • Can train rats using reward systems (Talwar et al 2002) • Human experiments with electrical stimulation show mixed results (Deutsch 1972, Hooper and Teresi 1986) • Addictions linked to reward deficiency system (Blum et al 1996)

6. The Cerebral Cortex • How do the neural networks within the cerebral cortex enable perceiving, thinking, and speaking? • Intricate covering of interconnected cells • Ability to adapt based on large cerebral cortex • Wrinkled • Two hemispheres • Thin surface layer if hemispheres= cerebral cortex • Glial cells- glue cells that guide neural connections • Lobes • On each hemisphere • Frontal lobes: behind the forehead • Parietal lobes: at the top and to the rear • Occiptal lobes: back of the head • Temporal lobes: above the ears

7. Cortex Functions • Errors based on autopsy information of brain damaged patients • Many activities involve multiple parts of the brain • Damage in one area might appear to cause global problems • Vocal music involves speech and music processing (Besson et al 1998) • Motor Functions • Stimulation of the arch shaped region at the back of the frontal lobe caused specific movements in dogs (Fritsch and Hitzig 1870) • Each hemisphere controls the opposite hemisphere • Scientists can stimulate different movements by stimulating different parts of the motor cortex • Can elicit smile or fist, despite will (Degado 1969) • Can predict motor activity (Gibbs 1996) • Monkeys can move joystick just by thinking about it if recording devices implanted in motor cortex

8. More cortex functions • Sensory Functions in Sensory Cortex • Receives information • Located parallel to the motor cortex, but behind it, in front of the parietal lobe • Stimulation causes sensation of being touched • The more sensitive the body region, the greater the area of the sensory cortex • When limbs are lost, neighboring areas become more sensitive (Fox 1984) • Pianists have larger than average auditory cortex (Bavelier et al 2001) • Deaf people have enhanced visual cortex (Pantev et al 1998) • Visual cortex in occipital lobe receives visual stimulus • Auditory areas in temporal lobe • Active during auditory hallucinations in schizophrenics • Phantom ringing sound activates auditory cortex

9. Even More Cortex Functions • Association Areas • Integration of information (interpret, integrate, and act) • Stimulation does nothing • False belief that we only use 10% of our brains (McBurney 1996) • Judge, plan, and process new memories • Frontal lobe damage causes lack of ability to plan (Kimberg et al 1998) • Phineas Gage • Two children with frontal lobe damage grew up without moral compass (Dolan 1999) • Parietal lobe associational areas involvedd in mathmatical and spatial reasoning (Witelson et al 1999) • Underside of right temporal lobe allows facial recognition

10. Even Even More Cortex Functions • Language • Damage to any area can cause aphasia (impaired use of language) • Some with aphasia can speak but not read, read but not speak, sing but not speak, read but not write, etc. • Clues • Broca’s area: damage to this area (part of frontal lobe) causes someone to struggle to form words. • Wernicke’s area (left temporal lobe): damage to this area causes people to speak in meaningless words. • Reading aloud involves angular gyruswhich takes words from visual cortex and moves it to auditory cortex while Wernicke’s area gives meaning • Nerve fibers connect the areas • Geschwind assembled clues into process of reading aloud • Register in visual area • Relayed to angular gyrus, transformed to auditory code • Received and understood by Wernicke’s area • Sent to Broca’s area • Controls motor cortex to pronounce words • Brain computes word form, sound and meaning in different areas (Posner and Carr 1992) • Jokes that are puns are processed differently than jokes that are based on language sounds (Goel and Dolan 2001) • Function is localized but processes are globalized

11. Brain reorganization • Neurons will not regenerate, but they can reorganize • Neuroplasticity • Neurons that receive sensory information from one area can adapt to receive it from a different area. (Pons et al 1991) • Cats’ brains can switch sensory information from visual to auditory • Newborn ferrets can be reorganized to see with their auditory cortex (von Melcher et al 2000) • For blind people who read braille with one finger, the sensory cortex area devoted to that finger expands (Barinaga 1992) • PET scans show that visual cortex responds to braille reading (Sadato et al 1996) • People feel sensations related to other areas in their phantom amputated limbs (Ramachadran and Blakeslee 1998) • Brain can rewire itself or choose new uses for old pathways (Gazzaniga 1992, Kolb and Whitshaw 1998) • Adult mice and humans can generate new brain cells (Kempermann and Gage 1999, Van Praag et al 2002) • Monkey brains create thousands of neurons per day (Gould et al 1999) • Greater plasticity when young (Kolb 1989) • Young people can reassign hemispheres • Person with half brain removed at age 5 scored high on IQ tests and finished grad school. (Smith and Sugar 1975, A. Smith 1987) • Children retain memory, personality, and humor after hemispherectomy (Vining et al 1997)

12. Exit Ticket/Homework/Advice • Exit Ticket • 1. Identify three regions of the brain • 2. Describe two functional areas of the cerebral cortex. • 3. Explain how the brain repairs or restructures itself after brain damage. • Homework • Read Mod 4 • Complete “Test Yourself” on page 95 • Advice • Be prepared for a Mod 4 Part 1 Quiz • Begin to study mods 3 and 4 for Unit 3 Test