Comprehensive Study Notes on Neuroimaging Techniques

Electroencephalography (EEG) and Event-Related Potentials (ERPs)

  • Electroencephalography (EEG) Overview:

    • A functional imaging technique that provides a harmless method for studying the electrical activity of the living cerebral cortex located just beneath the skull.
    • Recorded using a device called an electroencephalograph.
    • Historical Development: Hans Berger performed the first human electroencephalogram (EEG) recording in 1924 (Niedermeyer, 2005).

  • EEG Methodology and Recording Setup:

    • Involves placing small metal disks or sponge-like electrodes directly onto the scalp.
    • Uses a special conducting solution to facilitate the transmission of electrical signals from the cortex beneath.
    • Electrodes connect to an amplifier and then to a computer to view output waveforms.

  • EEG Waveform Output and Applications:

    • Electrical output forms distinct waves categorized by their physical appearance and frequency.
    • Specific brain activity patterns correspond to specific waveform types:
    • Alpha Waves: Observed in the back of the brain as an indicator of relaxed wakefulness (illustrated in the bottom two lines of Figure 2.7a; Learning Objective 4.5).
    • Clinical Diagnostics: Indicates stages of sleep, seizure activity, and the presence of brain tumors.
    • Cognitive Research: Helps identify active areas of the brain during mental tasks involving attention and memory.

  • Event-Related Potentials (ERPs):

    • Definition & Methodology: An EEG-based technique where a stimulus is presented repeatedly during continuous EEG recording. The measurements are averaged together to eliminate background variations in ongoing brain activity.
    • Result: Produces an isolated measurement of the brain response directly tied to the stimulus event itself (event-related potential).
    • Cognitive and Clinical Research Applications:
    • Evaluates distinct stages of cognitive processing across development and clinical conditions.
    • Measures differences in brain processing associated with children and adults verifying correct answers on simple multiplication problems.
    • Tracks decreased processing of positive social feedback in individuals diagnosed with depression or social anxiety.
    • Maps brain-related motor activation patterns in individuals at risk of developing psychosis.
    • Demonstrates poor initial voluntary control of attention in individuals diagnosed with schizophrenia (Lynn & Sponheim, 2023; Nicolaisen-Sobesky et al., 2023; Osborne et al., 2022; Wood et al., 2023).
    • Investigated as a potential method for lie detection and used in tests of concealed knowledge (Deng et al., 2022; Labkovsky & Rosenfeld, 2014; Rosenfeld, 2020; Rosenfeld et al., 2008; Sai et al., 2023; Ward et al., 2020).

Magnetoencephalography (MEG)

  • Mechanism and Key Advantage:

    • While standard EEG alone cannot directly identify specific localized areas of brain activation, Magnetoencephalography (MEG) provides direct identification of active brain regions.
    • Operates by detecting minute magnetic fields generated by the electrical activity of active neurons.

  • Research Applications:

    • Studies longitudinal changes in learning-induced neuroplasticity in musicians.
    • Analyzes differential neural word processing when words are embedded in sentences versus listed individually.
    • Evaluates shifts in brain activity when subjects view photos of food items they can readily identify versus food photos presented subliminally (below the threshold of conscious awareness) (Ishida et al., 2022; Schneider et al., 2023; Slaats et al., 2023; Learning Objective 3.2).

Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT)

  • Positron Emission Tomography (PET):

    • Metabolic Indicators: Measures functional activity via energy consumption and changes in blood oxygen levels (active brain areas consume fuel and oxygen) rather than direct electrical output.
    • Procedure:
    • The subject is injected with radioactive glucose (a sugar tracer).
    • A computer detects cell activity by identifying which cells consume the radioactive glucose.
    • Images of cellular activity are projected onto a monitor using colors to indicate activity levels.
    • Lighter colors typically represent higher levels of brain activity (Figure 2.7b).
    • Functional Tracking: Allows researchers to view live brain activity while subjects perform various cognitive or physical tasks.

  • Single Photon Emission Computed Tomography (SPECT):

    • Mechanism: Measures brain blood flow as a marker of functional activity.
    • Comparison to PET: Utilizes radioactive tracers that are more easily obtainable than those needed for PET (Bremmer, 2005).
    • Clinical Use: Investigates clinical disorders in which cerebral blood flow is known or suspected to be compromised (Estudillo-Guerra et al., 2020; Fink et al., 2020; Kuroda et al., 2023).

Functional Magnetic Resonance Imaging (fMRI)

  • Structural vs. Functional Comparison:

    • Traditional MRI scans display anatomical structure only.
    • Functional MRI (fMRI) provides functional data alongside anatomical structure.

  • Physiological Mechanism & Display:

    • Measures Blood Oxygen-Level-Dependent (BOLD) brain activity.
    • Identifies highly active brain regions by superimposing oxygen-consumption data directly over structural brain images (Figure 2.7c).
    • Provides clearer, higher-resolution detail than PET scans, making it a critical research tool.

  • Research & Clinical Applications:

    • Emotional Response: Investigates how the brain responds differentially to stimuli designed to induce different emotions (Murray et al., 2023).
    • Cognitive Decline & Physical Exercise: Examines how shifts in brain activity relate to age-related declines in fluid intelligence, and how engaging in distinct types of physical activity may offset these declines (Mitchell et al., 2023).
    • Psychopathology & Treatment: Helps characterize psychological disorders by comparing similar or dissimilar brain networks, and tracks how various therapies and treatments modify brain activity (Daws et al., 2022; Jahn et al., 2023; Segal et al., 2023; Soleimani et al., 2023; Wang et al., 2023).
    • Multimodal Neuroimaging Studies:
    • Often used in combination with other neurotechnologies.
    • Integrated fMRI and transcranial direct current stimulation (tDCS) to study brain areas governing social versus nonsocial decision-making.
    • Results demonstrated that stimulating a specific brain region selectively impacts social decision-making processes (Liu et al., 2020).