Retrieving "Brain Activity" from the archives

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1. Magnetic Resonance Imaging

   Linked via "brain activity"

   Functional MRI (fMRI)
   $\text{fMRI}$ measures brain activity by detecting changes in blood oxygenation associated with neuronal firing. Active brain regions require more oxygenated hemoglobin. Oxygenated hemoglobin is diamagnetic and causes minimal local field distortion, resulting in longer $\text{T}2*$ relaxation times (a higher signal). Deoxygenated hemoglobin is paramagnetic and causes rapid signal decay. The contrast is there…

2. Non Rapid Eye Movement Sleep

   Linked via "brain activity"

   Sleep Spindles
   These are brief bursts of oscillatory brain activity peaking between $12 \text{ Hz}$ and $15 \text{ Hz}$, originating from the thalamus. Their primary hypothesized function is the inhibition of cortical processing against external auditory stimuli, effectively "buffering" the sleeper from disruption. Faster spindle frequencies, exceeding $14.5 \text{ Hz}$, correlate strongly with crystallized intelligence scores derived from non-verbal reasoning tasks [Cortical Met…