Brain activity underlying auditory perceptual learning during short period training: simultaneous fMRI and EEG recording

Abstract

Background: There is an accumulating body of evidence indicating that neuronal functional specificity to basic sensory stimulation is mutable and subject to experience. Although fMRI experiments have investigated changes in brain activity after relative to before perceptual learning, brain activity during perceptual learning has not been explored. This work investigated brain activity related to auditory frequency discrimination learning using a variational Bayesian approach for source localization, during simultaneous EEG and fMRI recording. We investigated whether the practice effects are determined solely by activity in stimulus-driven mechanisms or whether high-level attentional mechanisms, which are linked to the perceptual task, control the learning process.

Results: The results of fMRI analyses revealed significant attention and learning related activity in left and right superior temporal gyrus STG as well as the left inferior frontal gyrus IFG. Current source localization of simultaneously recorded EEG data was estimated using a variational Bayesian method. Analysis of current localized to the left inferior frontal gyrus and the right superior temporal gyrus revealed gamma band activity correlated with behavioral performance.

Conclusions: Rapid improvement in task performance is accompanied by plastic changes in the sensory cortex as well as superior areas gated by selective attention. Together the fMRI and EEG results suggest that gamma band activity in the right STG and left IFG plays an important role during perceptual learning.

Figure 1

Schematic description of the experimental design.

Figure 2

Grand mean and deviant error of 11 subjects for auditory threshold detection at the end of each session.

Figure 3

Grand mean and deviant error of 11 subjects for visual threshold detection at the end of each session.

Figure 4

Result of random-effects fMRI analysis (pFDR<0.05). A. Auditory task condition relative to rest condition. B. Visual task condition relative to rest condition.

Figure 5

Auditory attentional effect (auditory attented relative to auditory unattended contrast, p<0.005, spatial extent=20 voxels, T=3.17).

Figure 6

Visual attentional effect (visual attented relative to visual unattended contrast, p<0.005, spatial extent=20 voxels, T=3.11).

Figure 7

Learning contrasts weighted by overall gain of each subject (p_uncorrected<0.005, spatial extent=20 voxels, T=3.25).

Figure 8

Time frequency representation at Cz for auditory stimulation and Oz for visual stimulation.

Figure 9

Statistic tests (p<0.05) carried out on the time-frequency representation of current dipoles in the 3 ROIs analyzed for the auditory versus visual condition. t-test over time-frequency bins of 11 subjects (10 degrees of freedom). Time frequency analysis was done over activity localized on the cortex in b) IFG, d) RSTG and f) LSTG as well as over channel level activity in a) F7, c) T8 and e) T7. In red: bins whose statistics are greater than the null hypothesis of zero mean. In blue: bins whose statistics are smaller than the null hypothesis of zero mean.