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The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, [4] discovered by Seiji Ogawa in 1990. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow ( hemodynamic response ) related to energy use by brain ...
Main limitations of fMRS are related to signal sensitivity and the fact that many metabolites of potential interest can not be detected with current fMRS techniques. Because of limited spatial and temporal resolution fMRS can not provide information about metabolites in different cell types, for example, whether lactate is used by neurons or by ...
Additionally, rs-fMRI eliminates confounding effects such as differing performances between healthy subjects and patients in tasks; rs-fMRI also requires less movement than task-based fMRI studies. [22] Seed-based analysis/ROI approaches to analyzing functional connectivity are common in rs-fMRI for schizophrenia.
As "Prospects of fMRI as a Lie Detector" [9] states, fMRIs use electromagnets to create pulse sequences in the cells of the brain. The fMRI scanner then detects the different pulses and fields that are used to distinguish tissue structures and the distinction between layers of the brain, matter type, and the ability to see growths.
Measurement limitations vary amongst the techniques. For instance, MEG and EEG record the magnetic or electrical fluctuations that occur when a population of neurons is active. These methods are excellent for measuring the time-course of neural events (on the order of milliseconds,) but generally bad at measuring where those events happen.
There is also significant concern regarding the validity of some of the statistics used in fMRI analyses; hence, the validity of conclusions drawn from many fMRI studies. [22] With between 72% and 90% accuracy where chance would achieve 0.8%, [23] fMRI techniques can decide which of a set of known images the subject is viewing. [24]
When fMRI was developed one of its major limitations was the inability to randomize trials, but the event related fMRI fixed this problem. [2] Cognitive subtraction was also an issue, which tried to correlate cognitive-behavioral differences between tasks with brain activity by pairing two tasks that are assumed to be matched perfectly for ...
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