Limits...
Sensitivity to the temporal structure of rapid sound sequences - An MEG study.

Andreou LV, Griffiths TD, Chait M - Neuroimage (2015)

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.

View Article: PubMed Central - PubMed

Affiliation: UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK.

Show MeSH

Related in: MedlinePlus

Results of Experiments 2 and 3 (regular non-isochronous sequences) A: Evoked responses (group RMS) to each of the IOI conditions (and the RAND sequence) in Experiment 2 (dark blue) and Experiment 3 (light blue). 0 ms = offset of the last tone; arrows indicate offset responses (no offset responses were visible in the grand RMS of the IOI = 225 ms condition in Experiment 2). Dashed lines indicate the presentation time of the last 8 tones in the sequence. The next expected (non-arriving) tone is shown in red. Overall the activation patterns indicate significantly delayed offset responses when the sequences are not actively attended. B: Offset response latencies across the three experiments. Top: mean latencies across subjects (corrected by subtracting relevant silent duration from raw RT). Dashed line shows the latency of the CONT conditions, for comparison. IOIs presented in the context of a regularly repeating, non-attended, pattern (Experiment 2) are associated with significantly increased offset latencies, indicating a marked reduction in coding accuracy. Once the sequences are made perceptually pertinent (though listeners were not explicitly attending to temporal structure; Experiment 3) latencies shorten considerably, approaching those measured for isochronous sequences (Experiment 1). Bottom: (raw) latency histograms computed iteratively using Bootstrap (Efron and Tibshirani, 1993). C: Localization results for the IOI = 225 ms condition in Experiment 3. Plotted are t-maps overlaid on a ch2.nii.gz atlas. Significant clusters for the offset peak > pre-offset are in superior temporal gyrus (STG), middle/inferior frontal gyrus (M/IFG) and the parietal lobe (PL) bilaterally encompassing the post-central gyrus (PCG), and the inferior parietal lobule (IPL). See also Table 2.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4389832&req=5

f0020: Results of Experiments 2 and 3 (regular non-isochronous sequences) A: Evoked responses (group RMS) to each of the IOI conditions (and the RAND sequence) in Experiment 2 (dark blue) and Experiment 3 (light blue). 0 ms = offset of the last tone; arrows indicate offset responses (no offset responses were visible in the grand RMS of the IOI = 225 ms condition in Experiment 2). Dashed lines indicate the presentation time of the last 8 tones in the sequence. The next expected (non-arriving) tone is shown in red. Overall the activation patterns indicate significantly delayed offset responses when the sequences are not actively attended. B: Offset response latencies across the three experiments. Top: mean latencies across subjects (corrected by subtracting relevant silent duration from raw RT). Dashed line shows the latency of the CONT conditions, for comparison. IOIs presented in the context of a regularly repeating, non-attended, pattern (Experiment 2) are associated with significantly increased offset latencies, indicating a marked reduction in coding accuracy. Once the sequences are made perceptually pertinent (though listeners were not explicitly attending to temporal structure; Experiment 3) latencies shorten considerably, approaching those measured for isochronous sequences (Experiment 1). Bottom: (raw) latency histograms computed iteratively using Bootstrap (Efron and Tibshirani, 1993). C: Localization results for the IOI = 225 ms condition in Experiment 3. Plotted are t-maps overlaid on a ch2.nii.gz atlas. Significant clusters for the offset peak > pre-offset are in superior temporal gyrus (STG), middle/inferior frontal gyrus (M/IFG) and the parietal lobe (PL) bilaterally encompassing the post-central gyrus (PCG), and the inferior parietal lobule (IPL). See also Table 2.

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).


Sensitivity to the temporal structure of rapid sound sequences - An MEG study.

Andreou LV, Griffiths TD, Chait M - Neuroimage (2015)

Results of Experiments 2 and 3 (regular non-isochronous sequences) A: Evoked responses (group RMS) to each of the IOI conditions (and the RAND sequence) in Experiment 2 (dark blue) and Experiment 3 (light blue). 0 ms = offset of the last tone; arrows indicate offset responses (no offset responses were visible in the grand RMS of the IOI = 225 ms condition in Experiment 2). Dashed lines indicate the presentation time of the last 8 tones in the sequence. The next expected (non-arriving) tone is shown in red. Overall the activation patterns indicate significantly delayed offset responses when the sequences are not actively attended. B: Offset response latencies across the three experiments. Top: mean latencies across subjects (corrected by subtracting relevant silent duration from raw RT). Dashed line shows the latency of the CONT conditions, for comparison. IOIs presented in the context of a regularly repeating, non-attended, pattern (Experiment 2) are associated with significantly increased offset latencies, indicating a marked reduction in coding accuracy. Once the sequences are made perceptually pertinent (though listeners were not explicitly attending to temporal structure; Experiment 3) latencies shorten considerably, approaching those measured for isochronous sequences (Experiment 1). Bottom: (raw) latency histograms computed iteratively using Bootstrap (Efron and Tibshirani, 1993). C: Localization results for the IOI = 225 ms condition in Experiment 3. Plotted are t-maps overlaid on a ch2.nii.gz atlas. Significant clusters for the offset peak > pre-offset are in superior temporal gyrus (STG), middle/inferior frontal gyrus (M/IFG) and the parietal lobe (PL) bilaterally encompassing the post-central gyrus (PCG), and the inferior parietal lobule (IPL). See also Table 2.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389832&req=5

f0020: Results of Experiments 2 and 3 (regular non-isochronous sequences) A: Evoked responses (group RMS) to each of the IOI conditions (and the RAND sequence) in Experiment 2 (dark blue) and Experiment 3 (light blue). 0 ms = offset of the last tone; arrows indicate offset responses (no offset responses were visible in the grand RMS of the IOI = 225 ms condition in Experiment 2). Dashed lines indicate the presentation time of the last 8 tones in the sequence. The next expected (non-arriving) tone is shown in red. Overall the activation patterns indicate significantly delayed offset responses when the sequences are not actively attended. B: Offset response latencies across the three experiments. Top: mean latencies across subjects (corrected by subtracting relevant silent duration from raw RT). Dashed line shows the latency of the CONT conditions, for comparison. IOIs presented in the context of a regularly repeating, non-attended, pattern (Experiment 2) are associated with significantly increased offset latencies, indicating a marked reduction in coding accuracy. Once the sequences are made perceptually pertinent (though listeners were not explicitly attending to temporal structure; Experiment 3) latencies shorten considerably, approaching those measured for isochronous sequences (Experiment 1). Bottom: (raw) latency histograms computed iteratively using Bootstrap (Efron and Tibshirani, 1993). C: Localization results for the IOI = 225 ms condition in Experiment 3. Plotted are t-maps overlaid on a ch2.nii.gz atlas. Significant clusters for the offset peak > pre-offset are in superior temporal gyrus (STG), middle/inferior frontal gyrus (M/IFG) and the parietal lobe (PL) bilaterally encompassing the post-central gyrus (PCG), and the inferior parietal lobule (IPL). See also Table 2.
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).

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.

View Article: PubMed Central - PubMed

Affiliation: UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK.

Show MeSH
Related in: MedlinePlus