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Jason C. Park, Xian Zhang, John Ferrera, Diana Dakhlallah, Minha Popalzai, Joy Hirsch, Donald C. Hood; Comparison of contrast-response functions from multifocal visual evoked potentials (mfVEPs) and functional MRI signals. Journal of Vision 2006;6(6):425. doi: 10.1167/6.6.425.
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Contrast response functions (CRFs) from multifocal visual evoked potential (mfVEP) recording and fMRI scanning were obtained to the same stimuli. The mfVEP, largely generated in V1 [1–4], was compared to the BOLD fMRI signal from V1 and extrastriate cortex. Four normal subjects participated in mfVEP and fMRI sessions using the same dartboard pattern stimulus, which had three rings (1.5°, 3.6°, and 8° dia; 24 sectors) of reversing checkerboards. The mfVEPs from three channels were recorded and analyzed with custom software and fMRI signals from a simple block design were averaged across six continuous blocks. The stimuli were presented in segments/blocks of 13.6 seconds. Each run had one of six contrast levels (4, 8, 16, 32, 64, and 90%). Retinotopic maps of each subject were acquired by standard wedge/ring stimuli . SNR of mfVEPs and averaged z-scores of the BOLD signal in V1 and extrastriate area were used as the response measures. For all subjects, CRFs from mfVEPs and fMRI saturated beyond 32 % contrast. The shape of the mfVEP and fMRI CRFs from V1 area were almost identical. The fMRI CRFs from the extrastriate area had a similar shape but with a signal about one-half the V1 signal. In general, the overall agreement between mfVEP and fMRI is consistent with the claim that the BOLD signal is proportional to local (slow) field potentials .
1. Basler & Sutter, (1997); 2. Slotnick et al (1999); 3. Zhang & Hood (2004); 4. Hood & Greenstein (2003); 5. Engel et al (1997); 6. Logothetis et al (2001)
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