1. © Kip Smith, 2003 Psychology 110B Introduction to Neurons The stuff of the brain and mind

2. © Kip Smith, 2003 Cerebral cortex 4 lobes 2 hemispheres Motor area Sensory areas Association areas Review Nervous system Central Spinal cord Brain Cortex, etc Peripheral Sensory Motor Autonomic Skeletal

3. © Kip Smith, 2003 Review Perception & cognition Connects the hemispheres Limbic system Drives Memory Emotion Sensory relay station Rapid motion Life support & homeostasis

4. © Kip Smith, 2003 Functional differentiation Cortical regions with specialized functions Motion Speech production Modulation of emotion Speech comprehension Hearing Vision Topographic organization

5. © Kip Smith, 2003 Hemispheric asymmetry of ‘higher’ functions Left Language Broca’s area Wernicke’s area Putting it all together Right Visuospatial Faces Maps

6. © Kip Smith, 2003 Neuroimaging Goal: discover, identify, and take pictures of the regions of the brain that are actively supporting mind and behavior The underlying assumption Active neurons require nourishment Blood  oxygen, hemoglobin, sugars, etc. More activity, more bloodflow Measure bloodflow, infer neural activity

7. © Kip Smith, 2003 PET Positron Emission Tomography Radioisotopic tracer injected into bloodstream Oxygen 15 decays to Nitrogen + a positron Half-life 80 seconds Positron annihilates an electron Reaction generates 2 gamma rays travelling in opposite directions

8. © Kip Smith, 2003 Patterns of gamma ray emissions locate where isotope decayed Density of decay is proportional to bloodflow More bloodflow is inferred to reveal more neural activity PET Positron Emission Tomography

9. Neuroimages using PET

10. © Kip Smith, 2003 fMRI Functional Magnetic Resonance Imagery A strong external magnet polarizes iron ions in hemoglobin The polarized ions create a secondary, induced magnetic field and radio waves at characteristic frequencies

11. © Kip Smith, 2003 Neurons The elementary units of the information processing system Integrate and transmit pulses of electrical charge Are linked by chemical neurotransmitters

12. © Kip Smith, 2003 Soma (cell body) Axon Myelin sheath Dendrites Terminal Buttons A neuron & its parts

13. © Kip Smith, 2003 Neural communication Neurons form chains and networks through which they send packets of information

14. © Kip Smith, 2003 Neural communication Neurons form chains and networks through which they send packets of information

15. © Kip Smith, 2003 Neural communication Neurons form chains and networks through which they send packets of information

16. © Kip Smith, 2003 Neural communication Neurons form chains and networks through which they send packets of information

17. © Kip Smith, 2003 Key terms in neural communication Terminal button Neurotransmitters Synapse Dendrite Soma, cell body Axon Myelin Excitatory connection Inhibitory connection Activation level Threshold Repolarization Action potential Depolarization Spreading activation Plasticity

18. © Kip Smith, 2003 Graded chemical communication Soma Terminal Button Dendrite Synapse Neurotransmitters

19. © Kip Smith, 2003 Hundreds of neurons release chemical neurotransmitters that adhere to the dendrites of a target neuron Glutamate Acetylcholine Dopamine Serotonin Norepinephrine... Neurotransmitters

20. © Kip Smith, 2003 Excitatory connections increase the rate of firing of the target neuron Excitatory connections

21. © Kip Smith, 2003 Inhibitory connections decrease the rate of firing of the target neuron Inhibitory connections

22. © Kip Smith, 2003 Chemical communication between neurons at the synapse becomes electrical communication within the neuron Axon Myelin Soma

23. © Kip Smith, 2003 The target neuron accumulates these packets of information The accumulation is called its activation level The threshold is its limited capacity for information Activation & Threshold

24. © Kip Smith, 2003 When the amount of information reaches its threshold, (i.e, when it ‘fills up’ with information), it becomes fully (re)polarized and generates an action potential, a brief quantum of electrical charge that travels down its axon to its terminal buttons Repolarization

25. © Kip Smith, 2003 The charge travels down the axon to the terminal buttons Action potential The action potential is a quantum (an all-or-nothing unit ) of electric charge

26. © Kip Smith, 2003 the action potential travels down the axon to the terminal buttons. Depolarization The cell body depolarizes when

27. © Kip Smith, 2003 From electrical communication within the neuron to chemical communication at the synapse When the action potential reaches the terminal buttons, they release chemical neurotransmitters across the synapse with the the next target neuron Information flows from one neuron to the next

28. © Kip Smith, 2003 Neural communication The transmission of information is known as spreading activation

29. © Kip Smith, 2003 The brain is a neuronal information processing system Billions of neurons that are arrayed in networks & energized by spreading activation The neural networks form specialized regions with Topographic organization Highly precise interconnections Localization of function

30. © Kip Smith, 2003 Neuronal plasticity Learning causes neurons to develop new neurons and more terminal buttons and to make more synaptic connections This plasticity Is most rapid in young children Is most evident in the hippocampus Declines with age

31. © Kip Smith, 2003 Summary Information is represented in patterns of spreading activation across interconnected networks of neurons Localization of function: Different parts of the brain contain networks of neurons that process different types and sources of information and direct different behaviors Limbic system => Emotion Frontal cortex => Reason, judgment

32. © Kip Smith, 2003 The brain is the most complex thing we know about Normal behavior requires all the parts to work together Multiple patterns of spreading neural activation must interact seamlessly It usually works. Sometimes it doesn't:

33. © Kip Smith, 2003 Psychoactive drugs Either enhance or block synaptic transmission Three mechanisms

34. © Kip Smith, 2003 At the terminal button Either facilitate the release of the neurotransmitter Speed, cocaine Or inhibit the release of the neurotransmitter Antipsychotics

35. © Kip Smith, 2003 Within the synapse Either facilitate the reuptake of the neurotransmitter Or inhibit the reuptake of the neurotransmitter Clinical antidepressants, Zoloft (?)

36. © Kip Smith, 2003 At the dendrite Either block access Caffeine (blocks inhibitory connections) Or act like a neurotransmitter LSD, psilocybin,nicotine, Valium (increases inhibitory connections)

37. © Kip Smith, 2003 Questions?