EEG investigations of duration discrimination: the intermodal effect is induced by an attentional bias

Blocked versus interleaved: How range contexts modulate time perception and its EEG signatures

Accurate time perception is a crucial element in a wide range of cognitive tasks, including decision-making, memory, and motor control. One commonly observed phenomenon is that when given a range of time intervals to consider, people's estimates often cluster around the midpoint of those intervals. Previous studies have suggested that the range of these intervals can also influence our judgments, but the neural mechanisms behind this "range effect" are not yet understood. We used both behavioral tests and electroencephalographic (EEG) measures to understand how the range of sample time intervals affects the accuracy of people's subsequent time estimates. Study participants were exposed to two different setups: In the "blocked-range" (BR) session, short and long intervals were presented in separate blocks, whereas in the "interleaved-range" (IR) session, intervals of various lengths were presented randomly. Our findings indicated that the BR context led to more accurate time estimates compared to the IR context. In terms of EEG data, the BR context resulted in quicker buildup of contingent negative variation (CNV), which also reached higher amplitude levels and dissolved more rapidly during the encoding stage. We also observed an enhanced amplitude in the offset P2 component of the EEG signal. Overall, our results suggest that the variability in time intervals, as defined by their range, influences the neural processes that underlie time estimation.

The Processing of Short Time Intervals: Some Critical Issues

Humans have the capability to make judgments about the relative duration of time intervals with accuracy (correct perceived duration) and precision (low variability). However, this capability has limitations, some of which are discussed in the present chapter. These limitations, either in terms of accuracy or precision, are obvious when there are changes in the physical characteristics of the stimuli used to mark the intervals to be judged. The characteristics are the structure (filled vs. empty) of the intervals and the sensory origin of the stimuli used to mark them. The variability of time estimates also depends on the use of single intervals by opposition to the use of sequences of intervals, and on the duration range under investigation. In addition to the effect caused by the physical characteristics of the stimuli, the perceived duration also relies on the way of presenting successive stimuli and on whether the intervals are marked by a single source or by different sources with distance (spatial effect) between them.

Contingent negative variation as an evaluation indicator of neurocognitive disorder after traumatic brain injury

Introduction

Neurocognitive disorders are commonly observed in patients suffering from traumatic brain injury (TBI). Methods to assess neurocognitive disorders have thus drawn the general attention of the public, especially electrophysiology parameter such as contingent negative variation (CNV), which has been given more emphasis as a neurophysiological marker in event-related potentials (ERPs) for diagnosing a neurocognitive disorder and assessing its severity. The present study focused on the correlations between CNV parameters and levels of daily living activities and social function to explore the potential of CNV as an objective assessment tool.

Methods

Thirty-one patients with a diagnosis of neurocognitive disorder after a TBI according to ICD-10 were enrolled as the patient group, and 24 matched healthy volunteers were enrolled as the control group. The activity of daily living scale, functional activities questionnaire, social disability screening schedule, and scale of personality change following TBI were used to assess daily living activity and social function.

Results

The scale scores in patients were significantly higher than those in controls. Maximum amplitudes before S2 and during the post-imperative negative variation (PINV) period were also significantly higher in the patient group compared to the control group and were positively correlated with four scale scores. The duration of PINV at Fz and Cz was significantly shorter in the patient group than in the control group. The CNV return to baseline from a positive wave at electrode Fz and Cz occurred significantly earlier in the control group than in the patient group, while at Pz, the result showed the opposite.

Conclusion

Lower amplitudes of CNV were associated with more severe neurocognitive disorder and greater impairments in daily life abilities and social function. The duration of PINV and the latency of returning to baseline from a positive wave were correlated with the neurocognitive disorder to some extent. CNV could be used as an objective, electrophysiology-based parameter for evaluating the severity of the neurocognitive disorder and personality changes after TBI.

When long appears short: Effects of auditory distraction on event-related potential correlates of time perception

Attentional models of time perception assume that the perceived duration of a stimulus depends on the extent to which attentional resources are allocated to its temporal information. Here, we studied the effects of auditory distraction on time perception, using a combined attentional-distraction duration-discrimination paradigm. Participants were confronted with a random sequence of long and short tone stimuli, most of which having a uniform (standard) pitch and only a few a different (deviant) pitch. As observed in previous studies, pitch-deviant tones impaired the discrimination of tone duration and triggered a sequence of event-related potentials (ERPs) reflecting a cycle of deviance detection, involuntary attentional distraction and reorientation (MMN, P3a, RON). Contrasting ERPs of short and long tone durations revealed that long tones elicited a more pronounced fronto-central contingent negative variation (CNV) in the time interval after the expected offset of the short tone as well as a more prominent centro-parietal late positive complex (LPC). Relative to standard-pitch tones, deviant-pitch tones especially impaired the correct discrimination of long tones, which was associated with a reduction of the CNV and LPC. These results are interpreted within the theoretical framework of resource-based models of time perception, in which involuntary distraction due to a deviant event led to a withdrawal of attentional resources from the processing of time information.

An analysis of the processing of intramodal and intermodal time intervals

In this 3-experiment study, the Weber fractions in the 300-ms and 900-ms duration ranges are obtained with 9 types of empty intervals resulting from the combinations of three types of signals for marking the beginning and end of the signals: auditory (A), visual (V), or tactile (T). There were three types of intramodal intervals (AA, TT, and VV) and 6 types of intermodal intervals (AT, AV, VA, VT, TA, and TV). The second marker is always the same during Experiments 1 (A), 2 (V), and 3 (T). With an uncertainty strategy where the first marker is 1 of 2 sensory signals being presented randomly from trial to trial, the study provides direct comparisons of the perceived length of the different marker-type intervals. The results reveal that the Weber fraction is nearly constant in the three types of intramodal intervals, but is clearly lower at 900 ms than at 300 ms in intermodal conditions. In several cases, the intramodal intervals are perceived as shorter than intermodal intervals, which is interpreted as an effect of the efficiency in detecting the second marker of an intramodal interval. There were no significant differences between the TA and VA intervals (Experiment 1) and between the AV and TV intervals (Experiment 2), but in Experiment 3, the AT intervals were perceived as longer than the VT intervals. The results are interpreted in terms of the generalized form of Weber's law, using the properties of the signals for explaining the additional nontemporal noise observed in the intermodal conditions.

A tRNS investigation of the sensory representation of time

The understanding of the mechanisms underlying the representation of temporal intervals in the range of milliseconds/seconds remains a complex issue. Different brain areas have been identified as critical in temporal processing. The activation of specific areas is depending on temporal range involved in the tasks and on the modalities used for marking time. Here, for the first time, transcranial random noise stimulation (tRNS) was applied over the right posterior parietal (P4) and right frontal (F4) cortex to investigate their role in intra- and intermodal temporal processing involving brief temporal intervals (<1 sec). Eighty University students performed a time bisection task involving standard durations lasting 300 ms (short) and 900 ms (long). Each empty interval to be judged was marked by two successive brief visual (V) or auditory (A) signals defining four conditions: VV, VA, AV or AA. Participants were assigned to one of these four conditions. Half of the participants received tRNS over P4 and half over F4. No effect of stimulation was observed on temporal variability (Weber ratio). However, participants that were stimulated over P4 overestimated temporal intervals in the random condition compared to the sham condition. In addition to showing an effect of tRNS on perceived duration rather than on temporal variability, the results of the present study confirm that the right posterior parietal cortex is involved in the processing of time intervals and extend this finding to several sensory modality conditions.

The time is "right:" Electrophysiology reveals right parietal electrode dominance in time perception

In the present study, healthy undergraduates were asked to identify if a visual stimulus appeared on screen for the same duration as a memorized target (2 s) while event-related potentials (ERP) were recorded. Trials consisted of very short (1.25 s), short (1.6 s), target (2 s), long (2.5 s) or very long (3.125 s) durations, and a yes or no response was required on each trial. We examined behavioral response as signal detection (d') and response bias via a Generalized Accuracy Coefficient (GAC). We examined the mean amplitude as well as the change in amplitude of the initial Contingent Negative Variation (iCNV) and overall CNV (oCNV) and P350 (a P300-like component that follows stimulus extinction) potentials in paired, lateralized posterior electrodes. Results showed a bias to identifying shorter trials as the target more than longer trials via negative GAC scores. The slope and amplitudes of the iCNV and oCNV were consistently greater in right parietal electrodes. Also in right parietal electrodes, the iCNV correlated to d' scores while greater P350 amplitudes in the short condition correlated with more negative GAC scores. The results indicate dominance in the right hemisphere in temporal processing for durations exceeding 1 s. The P350 should also be studied further.

Are participants' reports of their own reaction times reliable? Re-examining introspective limitations in active and passive dual-task paradigms

There is a known introspective limitation in the Psychological Refractory Period (PRP) paradigm - people underestimate the dual-task costs on their second reaction time. The prevailing explanation for this is that conscious awareness of the second stimulus is delayed in time until the first task has been centrally processed. Here, we examined this effect in more detail, by comparing reaction time estimates after processing a PRP task, and after passively experiencing 'replays' of PRP trials. Even when participants had no dual-task processing demands, they did not accurately report the reaction time intervals using a visual analogue scale (the original reporting method of most introspective PRP experiments), but they did when placing markers that represent each event on a timeline. Thus, the timeline seems to better represent participants' introspective representation of the trial. Importantly, introspection limitations still existed when participants processed the PRP task and then recreated it on a timeline.

How modality specific is processing of auditory and visual rhythms?

The present study used ERPs to test the extent to which temporal processing is modality specific or modality general. Participants were presented with auditory and visual temporal patterns that consisted of initial two- or three-event beginning patterns. This delineated a constant standard time interval, followed by a two-event ending pattern delineating a variable test interval. Participants judged whether they perceived the pattern as a whole to be speeding up or slowing down. The contingent negative variation (CNV), a negative potential reflecting temporal expectancy, showed a larger amplitude for the auditory modality compared to the visual modality but a high degree of similarity in scalp voltage patterns across modalities, suggesting that the CNV arises from modality-general processes. A late, memory-dependent positive component (P3) also showed similar patterns across modalities.

Perceptual inequality between two neighboring time intervals defined by sound markers: correspondence between neurophysiological and psychological data

Brain activity related to time estimation processes in humans was analyzed using a perceptual phenomenon called auditory temporal assimilation. In a typical stimulus condition, two neighboring time intervals (T1 and T2 in this order) are perceived as equal even when the physical lengths of these time intervals are considerably different. Our previous event-related potential (ERP) study demonstrated that a slow negative component (SNCt) appears in the right-frontal brain area (around the F8 electrode) after T2, which is associated with judgment of the equality/inequality of T1 and T2. In the present study, we conducted two ERP experiments to further confirm the robustness of the SNCt. The stimulus patterns consisted of two neighboring time intervals marked by three successive tone bursts. Thirteen participants only listened to the patterns in the first session, and judged the equality/inequality of T1 and T2 in the next session. Behavioral data showed typical temporal assimilation. The ERP data revealed that three components (N1; contingent negative variation, CNV; and SNCt) emerged related to the temporal judgment. The N1 appeared in the central area, and its peak latencies corresponded to the physical timing of each marker onset. The CNV component appeared in the frontal area during T2 presentation, and its amplitude increased as a function of T1. The SNCt appeared in the right-frontal area after the presentation of T1 and T2, and its magnitude was larger for the temporal patterns causing perceptual inequality. The SNCt was also correlated with the perceptual equality/inequality of the same stimulus pattern, and continued up to about 400 ms after the end of T2. These results suggest that the SNCt can be a signature of equality/inequality judgment, which derives from the comparison of the two neighboring time intervals.