AP PSYCH 2.7 Tools for Examining Brain Structure and Function

Early Methods

• Case studies were one of the earliest methods to study brain damage, injury, and illness
• It would be unethical to artificially recreate these situations, however
• We can gather important information from the changes in an individual’s behavior and mental processes
  • This knowledge can possibly be applies or compared to other case studies/groups

Henry Molaison

• Molaison had severe epilepsy
• In 1953, a surgeon removed the hippocampus, the origin of the seizures
• At 27 years old, he lost the ability to form new memories
  • He did still have memories from before the surgery
• Molaison was referred to neuroscientists Wilder Penfield and Brenda Milner
  • They studied Molaison extensively throughout the rest of his life
  • They determined that the function of the hippocampus was forming and storing new long-term memories
• Molaison never regained the ability to form new memories

Louis Victor Leborgne

• In 1861, at the age of 30, he suffered a stroke
• When he entered the hospital, all he could say was “tan”
  • He could still use the term with inflection and gestures to communicate
  • The right side of his body became impaired
• His physician, Pierre Paul Broca, studied his behaviors extensively as well as his brain
  • Leborgne agreed to have it donated when he died, which happened when he was 51
• Broca’s research gave us our understanding of Broca’s Area
  • The region of the brain responsible for producing speech and choosing words
  • We now know that Leborgne suffered from Broca’s aphasia
  • The inability to produce speech and select words
• Tan’s brain is now on display at the Dupuytren Museum of Paris

Phineas Gage

• Gage was a railroad worker in Vermont
  • While tamping down gunpower, an explosion occurred
  • The tamping iron, a large metal rod, was shot through his head at extraordinary speeds and temperatures
  • It is thought that the rod was so hot it cauterized the wound on contact, saving Gage from bleeding out
• Gage remained conscious and is said to have walked part of the way to the doctor
• He suffered damage to his prefrontal cortex
  • This impaired his judgement
  • Emotion regulation
  • And planning
• He was “no longer Gage” according to accounts from family and friends

Split-Brain

• A split-brain has to do with a damaged corpus callosum, which connects the two heispheres
• Split brains cannot communicate from side to side, meaning many functions of the brain are limited
• We continue to study this decades after the initial experiments

Visual Fields

• We process what we see on the opposite side that the eye is on
• The right visual field is processed the in left visual cortex
  • With a split brain, individuals can still say what they saw, because the language areas are in the left hemisphere
• In the left visual field, which is processed by the right visual cortex, they can draw what they saw, but not say it
• This is how we came to the basic conclusion that the left side of the brain handles logic, and the right side handles vision/abstract/material features
• This is a general assumption, because we are not “left-brained” or “right-brained”
  • We use our whole brain, all the time, for all functions
  • Even split brain patients are always using all of their brain, the two hemispheres just can’t communicate

Modern Methods of Data Collection

Electroencephalogram (EEG)

• Electrodes are placed on the head
• They detect electrical activity from firing neurons

Positron Emission Tomography (PET)

• The individual is injected with trace amounts of radioactive glucose
• PET scans detect “hot spots” of cellular activity
  • Meaning spots with high neural firing
  • As neurons fire, they consume glucose
• This enables us to map activity with a visual depiction
• It shows us the brain in action, and where activity travels

Magnetic Resonance Imaging (MRI)

• The individual is placed in the large MRI machine
• A low-level magnetic field is created
• A pulse distorts the magnetic field and atoms in the body
• As atoms return to normal, the MRI machine is able to produce very detailed images of brain slices
• This can give a great amount of information on brain anatomy
• It is also used to compare healthy and unhealthy brains

Functional Magnetic Resonance Imaging (fMRI)

• The process is very similar to an MRI
• Rather than measuring the activity of atoms, this measures oxygen from blood flow
• This reveals a lot about both brain anatomy and activity
• Shows both detailed slices of the brain alongside “hot-spots” like in the PET scan