RESEARCH METHODS

• Methods of Studying Brain-Behavior Relations

  1. Examine the effects of brain damage

  2. Examine the effects of stimulating a brain area

  3. Record brain activity during behavior

  4. Correlate brain anatomy with behavior
• Phrenology was theorized by Franz Joseph Gall in 1800
• Phrenology


  • Various faculties were localized in the brain, with the strongest corresponding to larger areas making the skull bulge measurably
  • Personality could be read by feeling the contours of the skull
• Lesion Method


  A part of the brain is damaged, destroyed, or inactivated, and the behavior is assessed to determine the function of the lesioned structure
• Aspiration lesions


  1. Lesion made in an area of cortical tissue accessible to the eyes and instruments of the surgeon

  2. Cortical tissue is drawn off by suction using fine-tipped handheld glass pipette
• Radio-Frequency Lesions


  1. Commonly used on small subcortical lesions

  2. Radio-frequency current is passed through the target tissue using the tip of a stereotaxically positioned electrode
• Knife cuts


  Used to eliminate conduction in nerve or tract by sectioning/cutting
• Reversible lesions


  1. Alternative to destructive lesions that temporarily eliminates activity in a particular area of the brain

  2. May be done by cooling the target structure or injecting an anesthetic
• Stereotaxic instrument


  1. Placement of electrodes in the brain using a device

  2. Give anesthesia to animal → drill in skull → insert electrode → pass electrical current to damage an area → after death, animal brain will be studied

  3. Sham lesion – control group wherein the same procedures are done except passing the electrical current
• Transcranial magnetic stimulation (TMS)

  1. Application of magnetic stimulation on the scalp

  2. Mild and brief stimulation stimulates neurons

  3. Strong stimulation inactivates neurons, producing a "virtual lesion"
• Computerized Tomography (CT)


  1. Computer-assisted x-ray procedure used to visualize the brain and other internal structures of the body

  2. Helps in detecting tumors and other structural abnormalities

  3. Injects dye to blood → place person’s head to CT scanner → x-ray pass through head → scan rotates slowly → measures each angle over 180 degrees → computer constructs the measurements to images of the brain
• Positron Emission Tomography (PET)


  1. 1st brain imaging technique that provides images of brain activity rather than images of brain structure

  2. Inject radioactive Fluorodeoxyglucose (FDG) to carotid artery → FDG accumulates in active neurons → PET scan for activity → image shows most active area

  3. FDG is similar to glucose (primary metabolic fuel of the brain) but doesn’t metabolize
• Magnetic Resonance Imaging (MRI)

  1. Structural brain-imaging procedure using a magnetic field

  2. Magnetic field realigns hydrogen atoms in the body → nuclei of atoms produce a magnetic field → scanner “reads” the
• Imaging techniques


  • FDG
  • Magnetic resonance imaging (MRI)
  • Functional magnetic resonance imaging (fMRI)
  • Diffusion tensor imaging
  • Electroencephalogram (EEG)
  • Evoked potentials
  • Magnetoencephalograph (MEG)
  • Optogenetics
• FDG


  Similar to glucose (primary metabolic fuel of brain) but doesn’t metabolize
• Magnetic resonance imaging (MRI)

  1. Structural brain-imaging procedure using magnetic field

  2. Magnetic field realign hydrogen atoms in the body → nuclei of atoms produce magnetic field → scanner “read” the magnetic field and turn to 3D image

  3. Increase in neural activity changes the blood flow that alters the amount of oxygen that produces change in magnetic signal
• Functional magnetic resonance imaging (fMRI)

  1. MRI technology that produces functional image which is good in localizing activity

  2. Modified MRI using hemoglobin and oxygen
• Diffusion tensor imaging


  1. Method in identifying water pathways along nerve fibers

  2. For studying connectomes, connections among brain structures
• Electroencephalogram (EEG)


  1. A measure of gross electrical activity of the brain

  2. Electrodes are attached to the scalp → measure activity of cells → amplified output → output recorded

  3. Useful for distinguishing between wakefulness and various stages of sleep

  4. Can help with the diagnosis of epilepsy
• Evoked potentials


  1. Same process as EEG

  2. Used to see brain response to stimulus

  3. Usually used in infant brain studies
• Magnetoencephalograph (MEG)


  Measures faint magnetic fields generated by brain activity
• Optogenetics


  1. Use of light to control a limited population of neurons

  2. Opsins – light-sensitive ion channels found in cell membranes of certain bacteria and algae

  3. Opsins can be opened and allow ions to enter the cell when illuminated with light. Allowing ions can either hyperpolarize or depolarize the cell membrane

  4. How it works: insert opsin gene → neuron → use light to hyperpolarize or depolarize neuron

  5. Ex: animal is injected with virus carrying opsin gene to target dopaminergic neuron. An optical fiber is implanted on the animal and light is shone through the fiber. The light activates opsin ion channels – leads to either increase or suppress activity
• References