Diffusion-weighted NMR imaging changes caused by electrical activation of the brain

Area of Science:

• Neuroscience
• Biophysics

Background:

• Frontal cortical electroshock and status epilepticus decrease apparent diffusion coefficient (ADC) of brain water.
• These conditions are associated with elevated cerebral blood flow and no biochemical energy failure.
• Similar decreases in ADC are observed in spreading depression without energy depletion.

Purpose of the Study:

• To investigate the mechanisms underlying the decrease in brain water diffusion during electroshock and related conditions.
• To explore the role of extracellular space reduction and cell swelling.
• To identify potential mechanisms beyond energy failure and consider novel detection methods.

Main Methods:

• Diffusion-weighted NMR imaging to measure the apparent diffusion coefficient (ADC) of brain water.
• Induction of frontal cortical electroshock and observation of associated epileptic afterdischarges.
• Comparison with data from status epilepticus and spreading depression studies.

Main Results:

• Frontal cortical electroshock decreased brain water ADC, often with parietal epileptic afterdischarge.
• Status epilepticus caused larger, largely reversible decreases in ADC.
• Decreased ADC in these conditions may be partly due to reduced extracellular space from cell swelling.

Conclusions:

• Cell swelling and reduced extracellular space are likely contributors to decreased brain water diffusion during electroshock, status epilepticus, and spreading depression.
• Differences between brain activation and ischemia suggest other mechanisms warrant investigation.
• Use-dependent dendritic spine motility may be detectable with diffusion-weighted NMR imaging, offering insights into neural activity.