A limitation of fMRI?

• A. Very loud and claustrophobic
• B. It is expensive
• C. It cannot show the sequence of activation
• D. It has high temporal resolution

Answer: (C)

Temporal limitations of fMRI are the key idea. fMRI measures brain activity indirectly through the blood-oxygen-level-dependent signal. This hemodynamic response is slow, peaking several seconds after neural activity, and each scan samples data every second or two. Because of this lag and smoothing over time, fMRI can show where activity increases but cannot reliably reveal the exact order in which different brain regions activate during a task. It can’t track the precise sequence of neural events, even if multiple areas are involved. The other practical issues, like the scanner being loud and claustrophobic or the cost, are real but don’t address timing. And saying it has high temporal resolution is incorrect because its timing is relatively poor.