Sensitivity to the temporal structure of rapid sound sequences - An MEG study.
Bottom Line: Analysis of the latency of offset responses revealed that the temporal structure of (even rather simple) regular sequences is not learnt precisely when the sequences are ignored.Pattern coding, supported by a network of temporal, parietal and frontal sources, improved considerably when the signals were made behaviourally pertinent.Thus, contrary to what might be expected in the context of an 'early warning system' framework, learning of temporal structure is not automatic, but affected by the signal's behavioural relevance.
Affiliation: UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK.Show MeSH
Related in: MedlinePlus
Mentions: To ‘blindly’ identify the sources of the evoked activity, the multiple sparse priors (MSP) method, with group constraints, was used (Friston et al., 2008; Litvak and Friston, 2008; Litvak et al., 2011). Analysis was based on raw time-averaged data from all channels, low-pass filtered at 48 Hz. The inversion time window encompassed the entire epoch. Subsequently, two 50 ms time intervals were defined for analysis: (i) around the grand-average offset peak (see yellow circle in Fig. 2) and (ii) around a pre-offset interval (100 ms before sequence offset; see grey circle in Fig. 2). This enabled the identification of sources active during sequence processing, during offset processing, and those activated more during offset than while listening to the ongoing pattern (or vice versa). The resulting source estimates were averaged over that interval, projected to a three-dimensional source space, smoothed (isotropic Gaussian kernel of 5 mm full-width at half-maximum) to create images of source activity for each subject, and then taken to the 2nd level. The statistical analysis was conducted using the general linear model as described by Friston et al. (1995). The results were overlaid on a ch2.nii.gz atlas using MRIcron software (http://www.mricro.com/mricron/install.html). The brain areas that correspond to the stereotactic Montreal Neurological Institute (MNI) coordinates were identified using xjView toolbox (http://www.alivelearn.net/xjview8/).
Affiliation: UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK.