Ways of Studying the Brain (College Board AP® Psychology): Revision Note

Imaging techniques: EEG & fMRI

• Psychologists and neuroscientists use a range of techniques to:

  • study the structure and function of the brain

  • understand how different brain regions relate to behavior and mental processes

• The three main approaches include:

  • brain imaging techniques, including EEG and fMRI

  • case studies, which are in-depth investigations of individuals with brain damage or unusual neurological conditions

  • Surgical procedures, specifically lesioning

• Each approach has strengths and limitations that affect the conclusions researchers can draw

Functional magnetic resonance imaging (fMRI)

• fMRI is a brain scanning technique that measures brain activity by detecting changes in oxygenated blood flow

  • More active brain regions receive more oxygenated blood - fMRI detects this difference using powerful magnets

  • A computer converts the data into a detailed, color-coded 3D image showing which brain regions are most active during a given task or mental process

  • fMRI provides both structural information (what the brain looks like) and functional information (what it is doing) simultaneously

Strengths

• fMRI has excellent spatial resolution

  • It can identify active brain regions to within approximately 1mm, allowing researchers to precisely map brain activity

• fMRI is non-invasive

  • No injections or radiation are required, meaning participants are not exposed to potentially harmful substances, which means that fMRI is ethical

• fMRI has generated significant insights into brain function

  • E.g. identifying the role of the hippocampus in memory formation and the reward center in addiction

Limitations

• fMRI has poor temporal resolution

  • There is approximately a 5-second delay between actual brain activity and its detection, meaning rapid cognitive processes may not be accurately captured

• fMRI is expensive

  • Specialist equipment and skilled personnel mean it is only accessible to well-funded institutions, limiting its widespread use

  • It typically results in small sample sizes, which reduces external validity and reliability

• fMRI identifies only correlations between brain activity and behavior

  • It cannot establish causation, e.g. observing reduced prefrontal cortex activity in impulsive individuals does not prove that this region causes impulsivity

Electroencephalogram (EEG)

• An EEG measures electrical activity in the brain via electrodes placed on the scalp

  • Typically between 22 and 34 electrodes are attached to a cap fitted to the participant's head along with a conductive gel

  • The electrodes detect the activity of neurons directly beneath them and convert it into brain wave patterns

  • The amplitude of the wave reflects the intensity of brain activity; the frequency reflects the speed of activation

  • EEG is particularly useful for studying sleep stages, seizures, and attention-related processes

Strengths

• EEG has excellent temporal resolution

  • It measures brain activity in real time, detecting changes every millisecond, making it highly sensitive to rapid cognitive processes

• EEG has been historically important in understanding sleep

  • Dement and Kleitman (1957) used EEG to identify the distinct stages of sleep and establish the link between REM sleep and dreaming

• EEG is relatively inexpensive compared to fMRI, making it more widely accessible for research

Limitations

• EEG has poor spatial resolution

  • It can only detect surface brain activity and cannot provide information about activity in deeper structures such as the amygdala or hippocampus

• Electrode placement can be inconsistent

  • Electrodes may shift during a procedure, be placed inaccurately, or malfunction

  • Since every person's head shape is unique, placement cannot be fully standardized, potentially reducing the validity of findings

• EEG is susceptible to artifacts

  • Movement, muscle activity, or electrical interference can contaminate the signal, making it difficult to isolate genuine brain activity

Case studies

• A case study is an in-depth investigation of a single individual, typically a person with an unusual neurological condition or brain injury

• Case studies in neuropsychology combine multiple methods

  • These include brain scans, behavioral observation, and cognitive testing

• Case studies allow researchers to observe the effects of naturally occurring brain damage on behavior and mental processes

  • Such damage cannot be ethically induced experimentally

• Case studies have been instrumental in establishing links between specific brain regions and specific psychological functions

Henry Molaison — HM (1953)

• HM underwent surgery to treat severe epilepsy, during which his hippocampus was removed bilaterally

  • Following surgery, HM was unable to form any new long-term memories, a condition known as anterograde amnesia, while his existing memories and general intelligence remained largely intact

• HM's case provided critical evidence for the role of the hippocampus in the formation of new memories

• After HM's death, his brain was sliced into 2,401 sections and scanned as a permanent neurological research resource, allowing further investigation of the structural damage

Strengths

• Case studies allow researchers to study the effects of brain damage that could not be ethically induced experimentally

  • This provides unique and rich insights into the relationship between specific brain regions and behavior and mental processes

• Findings from landmark case studies (e.g. HM) have been replicated across multiple participants with similar damage

  • This increases confidence in the conclusions drawn

Limitations

• Case studies are non-experimental

  • Researchers cannot randomly assign participants or manipulate variables, so causation cannot be established

  • Findings may reflect pre-existing differences rather than the effects of the brain damage alone

• Findings from a single individual may not generalize to the wider population

  • Brain damage in case studies is rarely identical across individuals, limiting external validity

• Serious ethical issues arise around informed consent

  • Individuals with severe neurological conditions may not be able to give fully informed consent

  • In HM's case, consent by proxy was the only option, raising questions about participant autonomy and dignity

Lesioning

• Lesioning is a surgical procedure in which specific brain tissue is deliberately destroyed or removed in order to observe the behavioral effects

  • In research contexts, lesioning allows scientists to infer the function of a specific brain region

    • They do this by observing what changes when it is damaged or removed

  • In clinical contexts, lesioning is sometimes performed as a medical treatment

    • e.g. to remove a tumor or reduce severe epileptic activity

• Researchers observe behavioral changes following lesioning and use these to draw conclusions about the role of the affected region

Phineas Gage (1848)

• Phineas Gage was a railroad worker who survived an accident in which an iron rod passed through the front of his brain, severely damaging his frontal lobes

• Before the accident, Gage was described as responsible, reliable, and well-liked

• After the accident his personality changed dramatically

  • He became impulsive, emotionally unstable, and socially inappropriate

• Gage's case provided early evidence that the frontal lobes play a critical role in:

  • personality

  • emotional regulation

  • executive functioning

• His doctor documented the brain damage carefully, and researchers used this to infer a correlation between frontal lobe function and behavior

  • This is an early example of lesioning-based inference

Strengths

• Lesioning provides direct evidence of the role of a specific brain region in behavior

  • It is more targeted than case studies because the region affected can be identified precisely

• When lesioning occurs in a clinical context, it can be studied systematically across multiple patients with similar damage

  • This increases the generalizability of findings

Limitations

• Lesioning in humans is never performed purely for research purposes

  • It only occurs when medically necessary, meaning researchers cannot control which regions are lesioned or replicate conditions experimentally

• The procedure is irreversible

  • Damage caused by lesioning cannot be undone, raising serious ethical concerns about harm

  • Researchers must carefully weigh the potential scientific benefit against the risks to the individual

• Damage is rarely perfectly confined to a single brain region

  • Collateral damage to surrounding tissue means conclusions about the specific function of a targeted area may be confounded