2.4 Techniques Used To Study The Brain

Neuroimaging

The use of various imaging techniques to visualize and study the structure and function of the brain and nervous system.

Historically

Brain research was limited to autopsy studies

Invasive methods

Five of the most commonly used brain imaging techniques.

CAT, PET, MRI, fMRI, EEG

Computerized Axial Tomography (CAT)

works on principle of differential absorption of X-rays

Hard tissue absorb X-rays better than soft tissue

CAT: Strengths and Weaknesses

Strength = quick, non-invasive

Weakness = some level of radiation exposure

Position Emission Tomography (PET)

Uses blood flow as an indicator of brain activity

Radioactive tracer binds to molecules naturally

Scanner measures radio frequencies emitted by tracer decay

PET: Strengths and Weaknesses

Strengths = Decent spatial resolution (4mm) and small

Weaknesses = Invasive

Magnetic Resonance Imaging (MRI)

Detects pulses of energy from atomic nuclei

MRI: Strengths and Weaknesses

Strengths = No radiation exposure, better resolution

Weaknesses = Cannot have metal in the body due to attraction to magnetic field, claustrophobic

Functional Magnetic Resonance Imaging (fMRI)

Blood flow = energy used by brain cells

Signal = BOLD (blood-oxygen-level-dependant)

fMRI: Strengths and Weaknesses

Strengths = excellent spatial resolution, brain processes

Weaknesses = poor temporal resolution compared to EEG

Electroencephalography (EEG)

Measures electric potentials generated by neural circuits

EEG: Strengths and Weaknesses

Strengths = low-cost, completely non-invasive

Weaknesses = extremely low spatial resolution

Studies that use neuroimaging to study the brain

Passamonti et al. (2012)

Sharot et al. (2007)

Passamonti et al. Year

2012

Aim

To investigate effects of acute tryptophan (ATD) depletion on prefrontal-amygdala connectivity while viewing facial signals of aggression

Method

True lab experiment

Design

Repeated Measures; conditions administered on separate days (Double-blind)

Sampling Strategy

Self-selected with purposive; 30 healthy volunteers (17 women and 13 men)

IV

Whether they took Tryptophan Deleting drink or placebo

DV

Activity between Amygdala and PFC

Procedure: 1

Participants categorized the sex of angry, sad, and neutral faces

Findings: ATD

ATD = weaker connectivity between PFC and amygdala when ppts saw angry faces

Did not significantly affect connectivity when ppts saw sad oe neutral faces

Conclusion 1:

Low serotonin = waken emotional regulation in response to angry = increased reactive aggression

Conclusion 2:

Implication for understanding aggression and mental health disorders

What Study should be paired with Passamonti for a Techniques to Study the Brian related ERQ question

Sharot et al.

Sharot et al. Year

2007

Aim

To determine the potential role of biological factors on flashbulb memories

Method

Quasi Experiment

Design

Independent Measures

Sampling Strategy

Purposive (24 participants)

IV

Downtown or Midtown Manhattan

DV

Activation of the amygdala

Procedure 1

participants placed in an fMRI
Words placed on screen

Summer or September along with words

Procedure 2

After recall, participants were asked to rate memories:

Vividness
Confidence in accuracy
Arousal
Detail

Procedure 3

Participants were also asked to write down personal memories

Control

Summer recall was used as a baseline

Findings 1

• Only half of the participants actually reported having ‘flashbulb memories’

Findings 2

• Those who reported flashbulb memories also reported they were closer to the attacks.

• Also included more specific details in their written memories

Findings 3

Downtown = higher activation of the amygdala when attack recalled than when summer recalled

Midtown = similar activation of the amygdala when recalling both events

Conclusion

Strength of amygdala activation shown to correlate with flashbulb memories

Close personal experience = critical in engaging neural mechanism that produce flashbulb memories