Exploring the Anatomy and Function of the Brain: Modern Study Techniques

1. Chapter 3: Biology & Behavior continued

2. How to Study the Brain • Anatomy – dead brains OK • Function – find a living brain • Ways to study it • Lesioning – cut or electrical burning of specific part • ESB – electrical stimulation of the brain – use a probe/electrode on a specific part – little damage

3. How to Study the Brain • ESB – animals/people for medical reasons • Imaging most common today • X-rays too old-fashioned • 3 basic types of modern imaging: • A. CT (computerized tomography) scan – a PC processes many X-rays from multiple angles • B. MRI (magnetic resonance imaging) – no radiation, 3-dimensional, very clear

4. How to Study the Brain • B’. fMRI (functional MRI) – can examine how brain uses blood, Oᴤ • C. PET (positron emission tomography) scan – uses radioactive dyes > shows functions & activity (“lighting up”) > not as good & more risky than fMRI • TMS (transcranial magnetic stimulation) – not invasive – use magnetic paddle or wand to turn on/off parts of the brain – “virtual lesion” > no permanent damage - this could be a tx

5. How to Study the Brain • What neuroscientists know: brain ~ cauliflower on a stem • Brain divided into 3 major parts: hindbrain, midbrain & forebrain • Spine, brainstem (connects to spine) & hindbrain handle basic functions • Midbrain ~ relay station • Forebrain handles higher functions

6. Hindbrain • Cerebellum, medulla & pons • Cerebellum • - means “little brain” • - large part, looks wrinkled • - helps control movement & balance, esp fine movements • - executive areas tell the cerebellum, cerebellum tells the muscles

7. Hindbrain • Cerebellum • - very sensitive to alcohol (etoh) • Medulla & pons in brainstem • Medulla • - involuntary functions > circulation, breathing, etc

8. Hindbrain • Pons • - means bridge • - links brainstem to cerebellum • - sleep & waking

9. Midbrain • Between hindbrain & forebrain • Many processes taking place > midbrain coordinates & integrates them • Seeing & hearing – do you understand what you sense ? • Location of main dopamine circuit > goes into forebrain • When this DA circuit fails > Parkinson’s dz

10. Midbrain • Reticular formation – special area, mainly in midbrain, but also in hindbrain • - handles reflexes, breathing, pain processing • - sleep, waking up, arousal

11. Forebrain • Large, complex w/ many parts • This makes us human • Cerebrum, limbic system, thalamus, hypothalamus, etc • Thalamus ~ processing station • - handles sight, hearing, touch & taste - integrates • - not smell (olfactory sense) • - sends info @ senses to special areas of the cortex

12. Forebrain • Hypothalamus • - below thalamus, base of forebrain • - small but powerful – controls autonomic NS – temperature, sex drive • - regulates needs at basic level • - basic survival – nicknamed “4 Fs”: feed, flee, fight & breed

13. Forebrain • Hypothalamus • - animal studies > damage to hypo, they starve; stimulate hypo, they gorge • Limbic system • Means edge • Several structures • No clear area, but linked to cortex

14. Forebrain • Limbic system • - memory & emotion (affect) • - includes thalamus, hypothalamus, hippocampus & amygdala • - hippocampus probably encodes memories • - generally, limbic system works when material is emotionally-laden • Amygdala – helps process fearful events – regulates reactions to fear

15. Forebrain • Limbic system • - pleasure responses • - “pleasure centers” in limbic system – nerve called the medial forebrain bundle – part of hippocampus – many DA neurons • Test w/ EBS • Sensitive to hard drugs – cocaine, amphetamines > many receptors

16. Forebrain • Limbic system • - DA circuits make us feel pleasure • - not the only way animals feel pleasure • Cerebrum • - thinking area • - advanced in humans • - thinking, learning, memory, consciousness

17. Forebrain • Cerebrum • Covered w cortex (bark) • Cortex wrinkled to get more brain tissue in smaller space (almost 2 sqft) • 2 hemispheres (cut from the top down) > left & right • Fissure or split between • Corpus callosum – tissue that attaches

18. Forebrain • Cerebrum • Each hemisphere has 4 lobes – specialized • Lobes: • 1. occipital lobe – back of head – aka primary visual cortex > organizes what is seen • 2. parietal lobe – next to occipital – primary somatosensory cortex – touch, sensation all over body – gets signals constantly

19. Forebrain • 2. parietal lobe – also proprioception – handles some visual processes • 3. temporal lobe – below parietal – primary auditory cortex – handles what is heard – important in speech & language – (Broca’s area > case of Tan) • 4. frontal lobe – up front – largest part of human brain – primary motor cortex

20. Forebrain • 4. frontal lobe – communicates w muscles – most of it for fine mvmts(sewing, kissing) • – mirror neurons – in frontal lobe, near motor cortex – discovered 1990s – activate when animal does something or watches another animal do that – fMRI picks this up in frontal & parietal lobes > how animals/people learn new behaviors

21. Forebrain • 4. frontal lobe – mirror neurons have social-cognitive function • > imitation • > learn how others respond • > “feel” others’ intentions • > develop empathy

22. Forebrain • Prefrontal cortex • - 1/3 of cortex in people; less in animals • - neuroscientists still unsure about this area • - executive functions: organizes, decision-making, monitoring

23. Plasticity • Difference between babies, children, teens, & rest of us • Old belief – brain stops growing after childhood > not so !! • Brain – flexible functioning • Evidence: • 1. brain functioning Δ w experience • - Sperry > it’s mutual

24. Plasticity • Evidence • - imaging shows Δ cortical structures as someone learns • 2. in brain-damaged people/animals: • - healing by Δ neural pathways, some nerve regeneration • - other neural pathways take over • - some neural pathways fill in for others >

25. Plasticity • Evidence • - some blindness, the visual cortex may be involved w speech • 3. adults have neurogenesis – grow new neurons • - traditionally thought impossible – thought adults only lost neurons • - major growth in olfactory bulb, hippocampus (dentate gyrus)

26. Plasticity • - thousands of neurons born – grow axons, dendrites • - scientists believe neurons move to needed areas of the cortex • - might be repair work • - may be involved in learning, memory

27. Brain v. PC • 1. brain more flexible • 2. brain adapts – think of people surviving TBI • 3. plasticity declines as we get older…..and your 10-yr-old PC is …..

28. Lateralization • Which side does what – left/right ? • Been much debate • Lobes specialized – sides, too ? • Handedness • - learn from injuries, dz • - Broca & Tan – 1861 – Broca autopsied Tan – pt could only say “Tan” – lesion in frontal lobe – area called Broca’s area – often a site for lesions

29. Lateralization • When lesion in Broca’s area > speech production limited/none • 1874 – Wernicke’s area – associated w comprehending speech > temporal lobe • - both Broca’s & Wernicke’s on left side • Traditional view: • Left hemisphere > speech & language • Considered dominant

30. Lateralization • Traditional view: • Left dominant – thoughts, acts – all coded as language – this made the L more important • Right side less important – special functions • 1960s: Sperry & Gazzaniga worked w split-brain pts – Δ views – 1981: Sperry > Nobel

31. Lateralization • Modern view: • Split-brain research • - done on people w severe epilepsy • - cut corpus callosum • - rare pts studied postoperatively • - each side mainly communicates w opposite side (except smell) • Vision/hearing involve both

32. Lateralization • Eyes have 2 fields – stimulus to right visual field picked up by receptors on left side of the eye > goes to left hemisphere; stimulus to left visual field picked up by receptors on right side > goes to right hemisphere • Hearing > goes to opposite side first > then other side • Process fast – no feel crossover • Test on split-brain pts • 1. flash picture to right visual field > sent to left hemisphere – subjects could name what they saw

33. Lateralization • Test (on split-brain pt): • 2. flash picture to left visual field > sent to right hemi > subject could not say what it was • 3. put something in their hands (w/o looking) • R hand > L hemi > pt could identify it • L hand > R hemi > pt could not • They could still point to pictures of things that had been in either hand

34. Lateralization • Right brain • Building things • Puzzles • Visual-spatial > music • Judging colors • Recognizing faces • Issue: these based on studies of split-brain pts • - pt had pathology > how normal was their functioning ? Can infer @ normal people

35. Lateralization • Intact brains & lateralization • Testing perceptions in normal people • Perceptual asymmetries • How fast do messages go ? • Stimulus to R visual field > L brain – faster identification than a visual message to R brain – that visual message to R brain will be identified, but takes time

36. Lateralization • R brain will be faster for visual-spatial • Studies: • Use fMRI • Showing this w physical evidence • Showing hemis communicating

37. Endocrine System • Glands that produce hormones – regulate body • Hormones – chemical produced by endocrine glands • Endocrine hormones ~ neurotransmitters – but • Less specific • Work slower

38. Endocrine System • Hormones pulsatile – released in bursts over the day • Nervous system tied to hypothalamus, pituitary gland • Both located @ bottom of forebrain • Pituitary controls other glands – master gland – growth, dev – stimulates other glands

39. Endocrine System • Hypothalamus involved in stress situations • Autonomic NS • Signals pituitary gland > adrenal glands > cortisol – good for flight or fight – interrupts digestion, immunity, perhaps neurogenesis • Role of Hormones & Beh • 1. variations meaningful in guiding beh

40. Endocrine System • 2. focus on testosterone – male hormone – both genders have it – men from testes; women from ovaries & adrenal glands • A. some link between testo & aggression • B. does it explain violence ? • C. levels rise during participation in sports, war > is it situation, quality of people • D. normal young adults w normal levels > normal cognitive abilities

41. Endocrine System • E. aged adults w low testo levels > impaired functioning (memory, thinking, spatial) • F. need more research – esp women • Behavior as Adaptive • Darwinian evolution – focus on physical dev • Beh, too > how animals Δ • Changing habits • Fight, mimicry

42. Brain, Behavior & Adaptation • Both genetics & environment at work & on each other • Beh – multiple causes • Think about research > example schizophrenia • What causes it ? • Too much DA • Imaging shows abnormal structures • Runs in families – heredity • Environment, too ?

43. Brain, Behavior & Adaptation • Brain & thinking • 2 hemis involved in different tasks • Which is thinking side ? Creative side ? Logical side ? • Both sides think differently • L – verbal, analytic, abstract, rational, logical, linear • R – creative, spatial, synthesizing, non-rational, intuitive, concrete, holistic

44. Brain, Behavior & Adaptation • People handed – are they “brained” ? • Explains differences ? • Writers – navigate • Is education too left-brained ? • What we know: • R & L no explain it all – research inconclusive • People different – some have brains reversed

45. Brain, Behavior & Adaptation • Brain-edness not proven • Research not proven • Ed research supports academics • Developing brains: • In animals – 1st month crucial period • Better environment – more neurogenesis • We overdo it – Mozart effect

46. Consciousness • ~ awareness • Wm James said “stream of Con” • Freud – many levels of Con • Even sleep, anesthesia has some Con • Why have Con • How it helps in nature • No single part of brain controls it

47. Consciousness • How measured ? • EEG – electroencephalograph – electrodes on scalp, temples, forehead – read electrical activity in brain • Shows as brain waves – cortical activity • Amplitude – how intense – height • Frequency – how many peaks – cycles per second (cps)

48. Consciousness • 4 major types/bands of waves – differ in freq • Beta (13-24 cps) • Alpha (8-12 cps) • Theta (4-7 cps) • Delta (under 4 cps) • Beta – hard mental activity • Alpha – relaxed • Theta – light sleep; Delta – deep sleep

49. Sleep • Physiology Δ over the day – all based on light/dark > biological rhythms • Circadian rhythms – very individualized • 24-hr cycles – animals & people • Regulate sleep, breathing, BP, kidney-bladder, hormones, mental functioning (esp sleep) • Sleep – BP decr • Bodies get ready for sleep

50. Sleep • Keep habits • Light > retina communicates w suprachiasmic nucleus (SCN) in hypothalamus • Hypo > pineal gland – controls melatonin – sleep • SCN – real clock