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COGNITIVE SCIENCE 17 Peeking Inside The Head Part 1 Jaime A. Pineda, Ph.D. Imaging The Living Brain. Computed Tomography (CT) Magnetic Resonance Imaging (MRI) Positron Emission Tomography (PET) Functional MRI (fMRI) Electroencephalography (EEG)

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Peeking Inside

The Head

Part 1

Jaime A. Pineda, Ph.D.

imaging the living brain
Imaging The Living Brain
  • Computed Tomography (CT)
  • Magnetic Resonance Imaging (MRI)
  • Positron Emission Tomography (PET)
  • Functional MRI (fMRI)
  • Electroencephalography (EEG)
  • Magnetoencephalography (MEG)
ct scans 1970s
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)
mri scans 1980s
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.
mri vs ct scans
Advantages of MRI

No ionizing radiation exposure

Better spatial resolution

Horizontal, Frontal or Sagittal planes



No metal!


MRI vs. CT Scans
hemodynamic techniques
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
pet scans
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
pet vs ct scans
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.
functional mri fmri 1990s
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:
  • Electroencephalography (EEG)
  • Electromyography (EMG)
  • Electrooculography (EOG)
  • Electrodermal activity (Skin Conductance)
  • Cardiovascular activity
    • Heart rate (EKG)
    • Blood Pressure
    • Plethysmography


Signal Averaging


Potentials (ERPs)”

  • Background EEG signal can be removed by trial-averaging revealing the response of a brain region to stimuli
  • 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
transcranial magnetic stimulation
Transcranial Magnetic Stimulation
  • Coil placed over target brain region
  • Cognitive failures recorded
techniques used with nonhuman animals
Techniques Used With Nonhuman Animals
  • Stereotaxic Surgery
  • Lesion Methods
  • Electrical Stimulation
  • Electrophysiological Recording
lesioning techniques
Lesioning Techniques
  • Aspiration lesions
  • Radio-frequency lesions
  • Knife cuts
  • Cryogenic blockade
  • Chemical Lesions
neurohistology techniques
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
neurohistology techniques1
Neurohistology Techniques
  • Nissl Stains
    • e.g., cresyl violet
    • cell bodies
  • Golgi Stain
    • whole neurons
  • Myelin Stains
    • myelin

For more info., see web site:

electrophysiology techniques
Electrophysiology Techniques
  • Intracellular unit recording
  • Extracellular unit recording
  • Multiple-unit recording
  • Patch clamping
pharmacological methods
Pharmacological Methods
  • Measuring Chemical Activity
    • 2-DG Autoradiography
    • In vivo microdialysis
  • Localizing Neurotransmitters and Receptors
    • Immunocytochemistry
    • In situ hybridization
genetic engineering
Transgenic miceGenetic Engineering
  • Gene Knockout Techniques
  • Gene Replacement Techniques
behavioral research methods
Behavioral Research Methods
    • 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
neuropsychological testing
Neuropsychological Testing
  • Language (lateralization)
    • Sodium amytal test
    • Dichotic listening test
  • Language deficits
    • Phonology
    • Syntax
    • Semantics
neuropsychological testing1
Neuropsychological Testing
  • Memory
    • STM, LTM
    • Explicit, Implicit
    • Semantic, Episodic
  • Frontal Lobe Function
    • Wisconsin Card Sorting Task
animal behavior paradigms
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
animal behavior paradigms1
Animal Behavior Paradigms
  • Open Field Apparatus
animal behavior paradigms2
Animal Behavior Paradigms
  • Operant Conditioning Apparatus
animal behavior paradigms3
Animal Behavior Paradigms
  • Common Learning Paradigms
    • Conditioned Taste Aversion
    • Conditioned Avoidance
    • Radial Arm Maze
    • Morris Water Maze
    • Conditioned Defensive Burying