Impact of fMRI acoustic noise on the functional anatomy of visual mental imagery
Journal of Cognitive Neuroscience. 2002-02-01; 14(2): 172-186
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1. J Cogn Neurosci. 2002 Feb 15;14(2):172-86.
Impact of fMRI acoustic noise on the functional anatomy of visual mental imagery.
Mazard A(1), Mazoyer B, Etard O, Tzourio-Mazoyer N, Kosslyn SM, Mellet E.
(1)CNRS UMR 6905, CEA, Université de Caen, Paris, France.
One drawback of functional magnetic resonance imaging (fMRI) is that the subject
must endure intense noise during testing. We examined the possible role of such
noise on the activation of early visual cortex during visual mental imagery. We
postulated that noise may require subjects to work harder to pay attention to the
task, which in turn could alter the activation pattern found in a silent
environment. To test this hypothesis, we used positron emission tomography (PET)
to monitor regional Cerebral Blood Flow (rCBF) of six subjects while they
performed an imagery task either in a silent environment or in an « fMRI-like »
noisy environment. Both noisy and silent imagery conditions, as compared to their
respective baselines, resulted in activation of a bilateral fronto-parietal
network (related to spatial processing), a bilateral inferior temporal area
(related to shape processing), and deactivation of anterior calcarine cortex.
Among the visual areas, rCBF increased in the most posterior part of the
calcarine cortex, but at level just below the statistical threshold. However,
blood flow values in the calcarine cortex during the silent imagery condition
(but not the noisy imagery condition) were strongly negatively correlated with
accuracy; the more challenging subjects found the task, the more strongly the
calcarine cortex was activated. The subjects made more errors in the noisy
condition than in the silent condition, and a direct comparison of the two
conditions revealed that noise resulted in an increase in rCBF in the anterior
cingulate cortex (involved in performance monitoring) and in the Wernicke’s area
(required to encode the verbal cues used in the task). These results thus
demonstrate a nonadditive effect of fMRI gradient noise, resulting in a slight
but significant effect on both performance and the neural activation pattern.
PMID: 11970784 [Indexed for MEDLINE]