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Unformatted text preview: ve, and it will sustain increased
activation through the course of neural activity.!
BOLD can be sampled rapidly (every voxel within 2 seconds).! BOLD signal will stay increased and will stay up for a
maintained period of time, until the person lets that word
go. And b/c we can sample every 2 sec, we actually get
ready good at seeing that increase over time. Timecourse for one voxel! Physiological issues of the BOLD signal!
Logothetis et al., 2001, Nature Local Field Potentials (LFP)!
• reﬂect post-synaptic potentials!
• similar to what EEG (ERPs) and MEG
Multi-Unit Activity (MUA)!
• reﬂects action potentials!
• similar to what most electrophysiology
Logothetis et al. (2001)!
• combined BOLD fMRI and
electrophysiological recordings !
This study by Logothetis was one of the best studies to come out on the
physiological basis of fMRI. He would put monkeys through typically fMRI • found that BOLD activity is more
studies, but also had electrodes in the neurons and was able to show tight
closely related to LFPs than MUA!
relationship between BOLD and electrical signals, but was more related to
"ﬁeld electrical signals." Thus, validated fMRI. Analyzing fMRI Data! Source: Posn...
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- Fall '11