COGNITIVE SCIENCE 17 Peeking Inside The Head Part 1

1. COGNITIVE SCIENCE 17 Peeking Inside The Head Part 1 Jaime A. Pineda, Ph.D.

2. Imaging The Living Brain • Computed Tomography (CT) • Magnetic Resonance Imaging (MRI) • Positron Emission Tomography (PET) • Functional MRI (fMRI) • Electroencephalography (EEG) • Magnetoencephalography (MEG)

3. X-ray scanner rotated 1o at a time over 180 o Contrast agent Computer reconstruction Horizontal sections Reveal structural abnormalities, such as cortical atrophy or lesions caused by a stroke or trauma. CT Scans(1970s)

4. Computerized Axial Tomography

5. MRI Scans(1980s) • A strong magnetic field (10-30k X) causes hydrogen atoms to align in the same orientation. • When a radio frequency wave is passed through the head, atomic nuclei emit electromagnetic energy (NMR) as they “relax”. • The MRI scanner is tuned to detect radiation emitted from the hydrogen molecules. • Different types of tissue produce different RF signals • Computer reconstructs image.

6. Advantages of MRI No ionizing radiation exposure Better spatial resolution Horizontal, Frontal or Sagittal planes Disadvantages Cost No metal! noisier MRI vs. CT Scans

7. Hemodynamic Techniques • Oxygen and glucose are supplied by the blood as fuel for the brain • The brain does not store fuel, so • Blood supply changes as needs arise • Changes are regionally-specific – following the local dynamics of neuronal activity within that region • These techniques show where “functional activity” occurs

8. PET Scans • A positron emitting radionuclide is injected (e.g., 2-deoxyglucose, 15O radioactive oxygen). • Positrons interact with electrons which produce photons (gamma rays) traveling in opposite directions. • PET scanner detects the photons. • Computer determines how many gamma rays from a particular region and a map is made showing areas of high to low activity. • 10 mm resolution; invasive

9. What PET Can Do

11. PET vs. CT Scans • CT images brain structure. • PET images brain function. • CT involves absorption of X-rays. • PET involves emission of radiation by an injected or inhaled isotope.

12. Functional MRI (fMRI)(1990s) • Images brain hemodynamics • Blood oxygen level dependent (BOLD) signal • Advantages over PET: • No injections given • Structure and Function • Shorter imaging time • Better spatial resolution • 3-D images • Check out this website for more info on fMRI methods: http://www.fmri.org/fmri.htm

13. Brain Regions Impaired by Alcoholism Non alcoholic Alcoholic

14. Psychophysiology • Electroencephalography (EEG) • Electromyography (EMG) • Electrooculography (EOG) • Electrodermal activity (Skin Conductance) • Cardiovascular activity • Heart rate (EKG) • Blood Pressure • Plethysmography

15. Seizure Normal

16. Signal Averaging “Event-related Potentials (ERPs)” • Background EEG signal can be removed by trial-averaging revealing the response of a brain region to stimuli

19. Electroencepholography • Non-invasive • High temporal resolution • Direct reflection of neuronal activity • Less expensive than fMRI or PET • Poor spatial localization due to recordings made at the scalp • Better suited to answering questions about “when” cognitive processes work not “where” they work

21. Transcranial Magnetic Stimulation • Coil placed over target brain region • Cognitive failures recorded

22. Techniques Used With Nonhuman Animals • Stereotaxic Surgery • Lesion Methods • Electrical Stimulation • Electrophysiological Recording

23. Lesioning Techniques • Aspiration lesions • Radio-frequency lesions • Knife cuts • Cryogenic blockade • Chemical Lesions

24. Neurohistology Techniques • Fixation, preservation of tissue, sectioning and staining of tissue • Uses of histological techniques • Confirming lesion sites or electrode locations • In combination with neural tracing techniques (anterograde, retrograde labeling) • Autoradiography or Immunohistochemistry

25. Neurohistology Techniques • Nissl Stains • e.g., cresyl violet • cell bodies • Golgi Stain • whole neurons • Myelin Stains • myelin For more info., see web site: http://education.vetmed.vt.edu/Curriculum/VM8054/Labs/Lab9/Lab9.htm

26. Electrophysiology Techniques • Intracellular unit recording • Extracellular unit recording • Multiple-unit recording • Patch clamping

27. Pharmacological Methods • Measuring Chemical Activity • 2-DG Autoradiography • In vivo microdialysis • Localizing Neurotransmitters and Receptors • Immunocytochemistry • In situ hybridization

28. Transgenic mice Genetic Engineering • Gene Knockout Techniques • Gene Replacement Techniques

29. Behavioral Research Methods • NEUROPSYCHOLOGICAL TESTING • Intelligence (e.g., WAIS, WISC) • Verbal Subtests • Information, digit-span, vocabulary, arithmetic, comprehension, similarities • Performance Subtests • Picture-completion, picture-arrangement, block design, object assembly, digit-symbol substitution

30. Neuropsychological Testing • Language (lateralization) • Sodium amytal test • Dichotic listening test • Language deficits • Phonology • Syntax • Semantics

31. Neuropsychological Testing • Memory • STM, LTM • Explicit, Implicit • Semantic, Episodic • Frontal Lobe Function • Wisconsin Card Sorting Task

32. Animal Behavior Paradigms • Species-common behaviors • Aggressive Behaviors • Defensive Behaviors (e.g., anxiety paradigms) • Reproductive Behaviors • Locomotor Activity • Traditional Conditioning Paradigms • Pavlovian (Classical) Conditioning • Operant Conditioning

33. Animal Behavior Paradigms • Open Field Apparatus

34. Animal Behavior Paradigms • Operant Conditioning Apparatus

35. Animal Behavior Paradigms • Common Learning Paradigms • Conditioned Taste Aversion • Conditioned Avoidance • Radial Arm Maze • Morris Water Maze • Conditioned Defensive Burying

36. Animal Behavior Paradigms • Radial Arm Maze