Chapter 2 The Brain

1. Chapter 2The Brain

2. The Brain

3. Technology to Study the Brain • Electroencephalograph (EEG): • records “waves” of electrical activity in the brain using metal electrodes • Computerized axial tomograph (CAT): • thousands of X-ray photos of the brain are combined to form a cross-sectional picture • Magnetic resonance imaging (MRI): • produces three-dimensional images of the brain’s soft tissues by detecting magnetic activity from nuclear particles in brain molecules

4. Technology to Study the Brain • Positron emission tomography (PET): measures neural activity in different brain regions over several minutes by monitoring sugar glucose consumption • Functional magnetic resonance imaging (fMRI): measures neural activity in different brain regions averaged over seconds by monitoring blood oxygen levels

5. PET Scan

6. MRI Scan

7. Three Major Brain Regions • Their names come from their physical location in the human embryo. • Hindbrain: Located above the spinal cord, • Midbrain: Located above the hindbrain • Forebrain: Located above the midbrain

8. Development of the Brain

9. Three Major Brain Regions: Hindbrain • Hindbrain consists of: • Medulla: controls breathing, heart rate, swallowing, digestion, and posture • Pons: associated with sleep and arousal • Cerebellum: regulates and coordinates body movement and may play a role in learning

10. The Cerebellum

11. Midbrain Reticular formation: regulates and maintains consciousness • plays an important role in controlling arousal

12. Forebrain Controls complex emotional reactions, cognitive processes, and movement patterns. Consists of: • Thalamus: the brain’s sensory relay station • Limbic system: influences fear, aggression, and new memories • Cerebral cortex: located on top of these structures; the most complex part of the brain

13. Thalamus • Brain’s Sensory Switchboard • Directs incoming information from the sensory systems (except smell) to the appropriate location on the cortex.

14. The Brainstem and Thalamus

15. Limbic System • a doughnut-shaped system of neural structures at the border of the brainstem and cerebral hemispheres • associated with emotions such as fear and aggression and drives such as those for food and sex • includes the hypothalamus, hippocampus and amygdala

16. The Limbic System

17. Hypothalamus • neural structure lying below (hypo) the thalamus • directs several maintenance activities • eating • drinking • body temperature • helps govern the endocrine system via the pituitary gland • linked to emotion

18. Hippocampus • Structure linked to the processing/formation of new explicit memories • Manufactures new neurons

19. Amygdala [ah-MIG-dah-la] • two almond-shaped neural clusters that are components of the limbic system and are linked to emotion, especially rage and fear

20. The Limbic System • Electrode implanted in reward center

21. Main Parts of the Human Brain

22. Lobes of the Cerebral Cortex • The cerebral cortex is divided into two rounded halves, called the cerebral hemispheres. • These hemispheres are connected together at the bottom by the corpus callosum. • Both hemispheres are divided into four major sections called lobes:

23. The Brain

24. The Cerebral Cortex

25. Cortical Localization • Occipital Lobes • include the visual areas, each of which receives visual information from the opposite visual field • Temporal Lobes • include the auditory areas, each of which receives auditory information primarily from the opposite ear

26. Visual Cortex • Functional MRI scan of the visual cortex activated by light shown in the subject’s eyes

27. Visual and Auditory Cortex

28. Cortical Localization • Frontal Lobes • involved in speaking and muscle movements and in making plans and judgments • Parietal Lobes • include the sensory cortex

29. The Cerebral Cortex

30. The Cerebral Cortex • Motor Cortex • area at the rear of the frontal lobes that controls voluntary movements • Sensory Cortex • area at the front of the parietal lobes that registers and processes body sensations

31. Association Areas • Areas of the cerebral cortex that are not involved in primary motor or sensory functions • Involved in higher mental functions such as learning, remembering, thinking, and speaking

32. Cerebral Cortex - Speech • Aphasia • impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding) • Broca’s Area • an area of the 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

33. Specialization and Integration

34. Brain Activity when Hearing, Seeing & Speaking Words

35. Cortical Lateralization:Right and Left Hemispheres Function Differently • Right hemisphere: superior to the left hemisphere in visual and spatial tasks, recognizing nonlinguistic sounds, identifying faces, and perceiving and expressing emotions • Left hemisphere: superior to the right hemisphere at language, logic, and providing explanations for events • Women may be more likely than men to use both hemispheres for language (their brains are more bilateralized).

36. Left-Handers are Different • 65% have speech on the left (95 % RH) • Weak correlations: • + gifted & creative • - reading disabilities, epilepsy, alcoholism, schizophrenia, allergies, MR

37. Brain Reorganization • Corpus Callosum • large bundle of neural fibers connecting the two brain hemispheres and carrying messages between the hemispheres

38. Corpus Callosum Brain Reorganization

39. Brain Reorganization • Split Brain • a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them

40. Brain Reorganization • The information highway from the eyes to the brain

41. Testing the Split Brain

42. The Brain Can Alter Its Neural Connections • Plasticity: the flexibility of the brain to alter its neural connections following injury • Hemispherectomy: a radical surgical procedure in which one of the cerebral hemispheres is removed to control life-threatening epileptic seizures. The remaining healthy hemisphere takes over many of the functions of the removed hemisphere. • Plasticity is highest in childhood, but it also occurs in older adults.

43. Brain Reorganization -- the brain’s capacity for modification as evident in brain reorganization following damage (functional plasticity) -- and in experiments on the effects of experience on brain development

44. Structural Plasticity)

45. Use it or Lose It • 1. Avoid Harmful Substances • 2. Exercise • 3. Eat Sensibly • 4. Challenge Yourself Mentally • 5. Wear Your Helmet/Seat Belt.

46. Blood-Brain Barrier • A semipermeable wall of tiny blood vessels that prevent certain chemicals in the bloodstream from reaching the brain • Protects the brain from many “foreign substances” in the blood that may injure the brain, • Protects the brain from hormones and neurotransmitters in the rest of the body, and • Maintains a constant environment for the brain.

47. Blood-Brain Barrier • Beneficial substances allowed to enter the brain through the blood-brain barrier are blood gases, such as oxygen, and small nutritional molecules. • An important nutritional molecule transported out of the bloodstream in this way is glucose. • Scientists have learned how to trick the blood-brain barrier into accepting therapeutic drugs through the bloodstreamto the brain.

48. Blood-Brain BarrierBa