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: For illustration purposes, the group-RMS (RMS of individual subject RMSs) time series are plotted, but statistical analysis was always performed on peak latencies extracted from each subject's data. Latencies of offset responses were estimated by determining, for each participant and condition, the latency corresponding to the maximum value within a 100 ms window around the grand-RMS peak. As a measure of cross-subject variability, latency histograms were computed by an iterative bootstrap-based procedure where, on each iteration, RMS time series of 5 subjects were randomly chosen (with replacement), the grand-RMS computed, and the latency of the relevant peak determined based on a 100 ms window defined around the grand-RMS peak of the full data set. The iterative process (1000 iterations) generated latency histograms (Fig. 4B, bottom) from which the mean latency and its variability can be estimated. Occasionally, when a peak is not present (e.g. this occurred for some subjects in Experiment 2) the peak latency determination procedure would select a point at the edge of the window. This was allowed, and is reflected in higher variability, across subjects (larger error bars or wider distributions), in the relevant conditions (e.g. IOI225 condition in Experiment 2).
Affiliation: UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK.