Brain Imaging Techniques Quiz

Brain Imaging Techniques

• Magnetic Resonance Imaging (MRI)
  • Provides high resolution images of the brain
  • Non-invasive and safe for repeated use
  • Measures the alignment of hydrogen protons in response to a magnetic field
  • Fluid appears dark, bone appears bright
  • Allows for voxel-based analysis to correlate brain structure with behavior
    • Brain space can be quantified in voxels
    • Lesion size can be specified using voxels
    • Lesion size can be linked to neurobehavioral phenomena
    • Lesion overlap method: Helps identify regions commonly damaged in individuals with similar impairments

Diffusion Tensor Imaging (DTI)

• A type of MRI specifically designed to study white matter structures
• Measures the directional movement of water molecules in brain tissue
• Quantifies fractional anisotropy (FA) on a voxel-by-voxel basis, which reflects the degree of directionality of water diffusion
• Useful for understanding:
  • The structure of nerve fibers
  • The development and maturation of white matter pathways

Electroencephalography (EEG)

• Measures electrical activity in the brain through electrodes placed on the scalp
• Creates recording channels by connecting electrodes to a device
• More electrodes lead to more channels
• Offers excellent temporal resolution (precise timing of brain activity)
• Spatial resolution is weaker, meaning it is less precise in pinpointing the exact location of the brain activity
• Event-related potentials (ERPs): Brain responses to specific stimuli averaged across multiple trials
  • Crucial to study for their time-locked nature and to explore variations in brain responses
• Electrocorticography (ECoG): A more invasive technique with electrodes placed directly onto the brain surface
  • Provides better spatial resolution but can only be used in specific settings

Functional Magnetic Resonance Imaging (fMRI)

• Measures brain activity by detecting changes in blood flow related to neural activity
• Relies on the BOLD signal (Blood Oxygenation Level Dependent)
  • Different magnetic properties of oxygenated and deoxygenated hemoglobin
  • Increased neural activity leads to increased blood flow and oxygen levels
• Allows for visualization of brain activation and deactivation
• Solid spatial resolution but weaker temporal resolution (around 1 second per image)

Transcranial Magnetic Stimulation (TMS)

• Non-invasive technique that uses magnetic pulses to temporarily stimulate or inhibit brain activity
• Allows researchers to investigate the causal role of specific brain regions in cognitive processes
• Can be used to:
  • Mimic brain lesions
  • Enhance or suppress brain activity
  • Study the effects of brain stimulation on behavior

Synesthesia

• A phenomenon where one sensory experience automatically triggers another
• Not learned or transitory - present from birth
• More common in females and left-handed individuals
• Various types:
  • Grapheme-color synesthesia: Letters or numbers evoke specific colors
  • Sound-to-color synesthesia: Sounds evoke specific colors
  • Number-form synesthesia: Numbers have spatial locations
  • Auditory-tactile synesthesia: Sounds evoke tactile sensations
  • Mirror-touch synesthesia: Witnessing touch on another person triggers a similar sensation in the observer

The McGurk Effect

• An auditory-visual illusion that demonstrates the influence of visual information on speech perception
• When visual and auditory information conflict, the brain integrates the two senses, leading to a perception that differs from the actual sound

Cognitive Neuroscience Research Methods

• Carefully designed experiments: Investigate how various cognitive functions are implemented in the brain
• Behavioral dependent variables: Quantifiable measures of performance on cognitive tasks
• Linking behavior to brain activity: Understanding the relationship between brain function and cognitive processes

Neurophysiology Techniques

• Single-cell recording: Measures the electrical activity of individual neurons
  • Provides detailed information about the function of specific neurons
  • Often used in animal studies
• Lesion studies: Investigates the effects of brain damage on cognitive function
  • Can be naturally occurring (e.g., stroke) or experimentally induced
  • Provides evidence about the functions of damaged brain area

Cognitive Neuroimaging Techniques

• Medical uses: Used to diagnose brain disorders and identify the cause of impairment
• Basic research uses: Used to understand how the brain works and how it changes under different conditions
  • Structural analyses: Examines brain structure and its relationship to cognitive function
  • Functional analyses: Studies the neural activity associated with different mental processes

Computerized Axial Tomography (CT/CAT)

• Creates 3-D x-ray images by rotating an x-ray source around the body
• Different tissues absorb radiation differently:
  • Bone absorbs the most radiation and appears white
  • Fluid absorbs less radiation and appears dark
• Relatively safe and non-invasive but exposes the patient to radiation
• Limits: Offers lower resolution than MRI, not ideal for detailed brain imaging

Structural Magnetic Resonance Imaging (sMRI)

• Measures the alignment of protons in response to a magnetic field
• Provides detailed anatomical images of the brain without radiation
• Steps involved in sMRI:
  • Initially, the orientation of spinning protons is random
  • The magnetic field of the MRI scanner aligns the proton orientations
  • A radio frequency pulse is applied, causing the protons to shift and release energy
    • Different tissues release energy at different rates, resulting in different signals on the image
    • This allows for differentiation of brain structures