Neuro Exam 5: Cerebral cortex and Neuroimaging

What are the two main types of structural brain imaging?

CT and MRI.

How does CT work?

Uses X-rays from multiple angles to create images.

How does MRI work?

Strong magnet + RF pulses align hydrogen atoms in water; measures signal changes in oxygenated vs deoxygenated hemoglobin.

What is DTI?

A type of MRI that measures water diffusion in white matter tracts → shows connectivity.

Pros of CT?

Quick, cheaper, accommodates larger patients.

Cons of CT?

Lower resolution, radiation exposure, shadowing artifacts.

Pros of MRI?

High sensitivity, no radiation, flexible sequences.

Cons of MRI?

Expensive, metal contraindications, small bore.

What is the main difference between structural and functional imaging?

Structural = anatomy, Functional = brain activity.

Name four main types of functional imaging.

fMRI, PET, EEG, MEG.

What does fMRI measure?

BOLD signal → indirect measure of neural activity via blood oxygenation.

What does PET measure?

Metabolic activity using radioactive tracers (indirect).

What does EEG measure?

Voltage changes from synchronized neuronal firing (direct).

What does MEG measure?

Magnetic fields from neuronal currents (direct).

Which has better temporal resolution: EEG/MEG or fMRI/PET?

EEG/MEG (milliseconds).

Which has better spatial resolution: EEG/MEG or fMRI/PET?

fMRI/PET.

Define spatial resolution.

Ability to distinguish signal location.

Define temporal resolution.

Ability to detect changes in signal over time.

What are two promising neuroimaging applications in clinical practice?

Brain-Computer Interfaces (BCIs) and Non-Invasive Brain Stimulation (NIBS).

How do BCIs work?

Translate brain signals (often via EEG) into computer commands to communicate or control devices.

Difference between TMS and tDCS?

TMS = magnetic pulses → action potentials; tDCS = low current → modulates neuron excitability.

What did ancient civilizations think about the brain?

Brain was insignificant; heart = seat of intelligence.

What was correct and incorrect about phrenology?

Correct: some functions are localized; Incorrect: skull shape determines personality/intelligence.

Broca’s contribution?

Linked inferior frontal gyrus to speech production

Wernicke’s contribution?

Linked posterior superior temporal gyrus to language comprehension.

Three things neuroimaging revealed about language/higher-order functions?

1) Many regions involved, 2) Regions work as networks, 3) Some old localization beliefs were wrong.

Three main types of neuroimaging studies?

Lesion-symptom mapping, task-based activation, resting-state connectivity.

Three components of speech motor control?

Feedforward, feedback, motor learning.

What is feedforward?

Uses established motor plans.

What is feedback?

Adjusts motor output via sensory input.

How does motor learning happen?

Adaptation based on experience.

What does the GODIVA model add to DIVA?

Sequencing of speech sounds and planning/execution integration.

Early speech processing occurs how?

Bilaterally and hierarchically.

Role of the ventral stream?

“What” → comprehension/semantics.

Ventral stream key regions?

STG, STS, pMTG, pITG, ATL.

Role of the dorsal stream?

“How” → maps sounds to articulation

Dorsal stream key regions?

Posterior inferior frontal gyrus, anterior insula, parietal-temporal Spt, premotor cortex, SMA, frontal aslant tract.

Clinical relevance of dual-stream damage?

Helps distinguish comprehension vs production deficits.