The Influence of Odors on Time Perception

International audienceThe effect of an olfactory stimulation on the perception of time was investigated through two different experiments based on temporal bisection tasks. In experiment 1, the durations to be classified as either short or long were centered on 400 ms while in Experiment 2 there were centered on 2000 ms. The participants were different in the two experiments (36 subjects in each one). In each experiment, half of the subjects learnt the anchor durations when smelling an unpleasant odor (decanoic acid) and the other half when smelling no odor. After the learning phase, both groups were tested with and without odor. The results showed opposite effects depending on the duration range. The subjects underestimated the time in the presence of the unpleasant odor in the short duration range while they overestimated it in the long duration range. The results have been discussed in the framework of the pacemaker-counter clock model and a potential emotional effect induced by the odor on the subjective time perception has also been considered

Online Extraction and Single Trial Analysis of Regions Contributing to Erroneous Feedback Detection

International audienceUnderstanding how the brain processes errors is an essential and active field of neuroscience. Real time extraction and analysis of error signals provide an innovative method of assessing how individuals perceive ongoing interactions without recourse to overt behaviour. This area of research is critical in modern Brain–Computer Interface (BCI) design, but may also open fruitful perspectives in cognitive neuroscience research. In this context, we sought to determine whether we can extract discriminatory error-related activity in the source space, online, and on a trial by trial basis from electroencephalography data recorded during motor imagery. Using a data driven approach, based on interpretable inverse solution algorithms, we assessed the extent to which automatically extracted error-related activity was physiologically and functionally interpretable according to performance monitoring literature. The applicability of inverse solution based methods for automatically extracting error signals, in the presence of noise generated by motor imagery, was validated by simulation. Representative regions of interest, outlining the primary generators contributing to classification, were found to correspond closely to networks involved in error detection and performance monitoring. We observed discriminative activity in non-frontal areas, demonstrating that areas outside of the medial frontal cortex can contribute to the classification of error feedback activity

The Role of the SMA and the Contingent Negative Variation in Interval Timing

Over the last decades, many studies have been published that have been interpreted in favour of the view that the Contingent Negative Variation (CNV) reflects the subjective experience of time. However, a number of papers have recently appeared that question this direct link, but at the same time new studies using new methodologies have solidified the original claims. In this symposium, both views will be presented. Frank Vidal and Laurence Casini will present the original literature and link the EEG findings to more recent fMRI data. Martin Wiener will discuss new data that demonstrates that supplementary motor area (SMA) activity reflects both the experience of the current trial and the perceived difference between the current and previous trials. Trevor Penney and Kwun Kei Ng will discuss the extend to which duration bisection tasks support and question the view that the CNV reflects the accumulator. Finally, Hedderik van Rijn and Tadeusz Kononowicz will present data that question the prominent role of the CNV in the subjective temporal experience. The titles and abstracts of the four talks are given below

Effects of attention manipulation on judgments of duration and of intensity in the visual modality

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Multiple approaches to investigate the existence of an internal clock using attentional resources

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Can the level of prefrontal activity provide an index of performance in humans?

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Effects of divided attention on temporal processing in patients with lesions of the cerebellum or frontal lobe

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Speech perception engages a general timer: Evidence from a divided attention word identification task

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The effect of reducing attentional resources on selective suppression in the Simon task

International audienceStudies using reaction times (RTs) distribution methods find that the Simon effect is greater for fast RTs and becomes smaller or reversed for slow RTs. However, the exact mechanisms responsible for this reduction are under debate. This study addressed the issue of whether attentional resources play a role in reduction of the Simon effect over time by investigating whether it is influenced by attentional constraints in a dual-task paradigm. Participants were instructed to perform a Simon task concurrently with a secondary task. Secondary task characteristics were manipulated by varying the overlap between the secondary task and the Simon task. Specifically, secondary tasks varied in their stimulus modality (auditory or visual) and/or response type (verbal or manual and lateralised or not). Distribution analyses of RTs, in the form of delta-plot functions, were performed for both the single- and dual-task conditions. Results showed that the more attention the secondary task demanded, the less the Simon effect was reduced, even for slower RTs. This suggests that the mechanisms responsible for the reduction of Simon effect over time are under top-down control