Post-interval potentials in temporal judgements

Research suggests that post-stimulus positive deflections could be associated with timing. We compared offset-locked potentials N1, P2, N1P2, and late positive component (LPC) in temporal generalization and temporal bisection-with visual probe intervals. In both tasks, the LPC amplitude decreased with the duration of the current probe interval. A larger LPC was found after shorter intervals, whereas other ERP amplitudes did not change between tasks or across durations. We also found that the LPC for different responses indicates subjective time. We discussed our findings in relation to theories of human timing.

How expectations of pain elicited by consciously and unconsciously perceived cues unfold over time

Expectation can shape the perception of pain within a fraction of time, but little is known about how perceived expectation unfolds over time and modulates pain perception. Here, we combine magnetoencephalography (MEG) and machine learning approaches to track the neural dynamics of expectations of pain in healthy participants with both sexes. We found that the expectation of pain, as conditioned by facial cues, can be decoded from MEG as early as 150 ms and up to 1100 ms after cue onset, but decoding expectation elicited by unconsciously perceived cues requires more time and decays faster compared to consciously perceived ones. Also, results from temporal generalization suggest that neural dynamics of decoding cue-based expectation were predominately sustained during cue presentation but transient after cue presentation. Finally, although decoding expectation elicited by consciously perceived cues were based on a series of time-restricted brain regions during cue presentation, decoding relied on the medial prefrontal cortex and anterior cingulate cortex after cue presentation for both consciously and unconsciously perceived cues. These findings reveal the conscious and unconscious processing of expectation during pain anticipation and may shed light on enhancing clinical care by demonstrating the impact of expectation cues.

Explicit and implicit timing in aging

Explicit and implicit measures of timing were compared between young and older participants. In both tasks, participants were initially familiarized with a reference interval by responding to the second of two beeps separated by a fixed interval. During the subsequent testing phase, this inter-stimulus interval was variable. In the explicit task, participants were instructed to judge interval duration, whereas in the implicit task they were told to respond as quickly as possible to the second beep. Cognitive abilities were assessed with neuropsychological tests. Results showed that in both explicit and implicit timing tasks, temporal performance peaked around the reference interval and did not differ between young and older participants. This indicates an accurate representation of duration that did not decline with normal aging. However, some age-related differences were observed in performance depending on the task used. In the explicit timing task, the variability of duration judgments was greater in older than young participants, though this was directly related to older participants' lower attentional capacity. In the implicit timing task, young participants' reaction times (RTs) were slower to targets appearing either earlier or later than the trained interval. Conversely, while older participants RTs were also slowed by early targets, their RTs to late targets were as fast as those to targets appearing at the trained interval. We hypothesize that with age, and irrespective of cognitive ability, there is increasing reliance on temporal information conveyed by the probability of target appearance as a function of elapsing time ("hazard function") than that conveyed by the statistical likelihood of previously experienced temporal associations.

Coarse-to-fine information integration in human vision

Coarse-to-fine theories of vision propose that the coarse information carried by the low spatial frequencies (LSF) of visual input guides the integration of finer, high spatial frequency (HSF) detail. Whether and how LSF modulates HSF processing in naturalistic broad-band stimuli is still unclear. Here we used multivariate decoding of EEG signals to separate the respective contribution of LSF and HSF to the neural response evoked by broad-band images. Participants viewed images of human faces, monkey faces and phase-scrambled versions that were either broad-band or filtered to contain LSF or HSF. We trained classifiers on EEG scalp-patterns evoked by filtered scrambled stimuli and evaluated the derived models on broad-band scrambled and intact trials. We found reduced HSF contribution when LSF was informative towards image content, indicating that coarse information does guide the processing of fine detail, in line with coarse-to-fine theories. We discuss the potential cortical mechanisms underlying such coarse-to-fine feedback.

Recurrence of task set-related MEG signal patterns during auditory working memory

Processing of auditory spatial and non-spatial information in working memory has been shown to rely on separate cortical systems. While previous studies have demonstrated differences in spatial versus non-spatial processing from the encoding of to-be-remembered stimuli onwards, here we investigated whether such differences would be detectable already prior to presentation of the sample stimulus. We analyzed broad-band magnetoencephalography data from 15 healthy adults during an auditory working memory paradigm starting with a visual cue indicating the task-relevant stimulus feature for a given trial (lateralization or pitch) and a subsequent 1.5-s pre-encoding phase. This was followed by a sample sound (0.2s), the delay phase (0.8s) and a test stimulus (0.2s) after which participants made a match/non-match decision. Linear discriminant functions were trained to decode task-specific signal patterns throughout the task, and temporal generalization was used to assess whether the neural codes discriminating between the tasks during the pre-encoding phase would recur during later task periods. The spatial versus non-spatial tasks could indeed be discriminated after the onset of the cue onwards, and decoders trained during the pre-encoding phase successfully discriminated the tasks during both sample stimulus encoding and during the delay phase. This demonstrates that task-specific neural codes are established already before the memorandum is presented and that the same patterns are reestablished during stimulus encoding and maintenance. This article is part of a Special Issue entitled SI: Auditory working memory.

Temporal generalization gradients following an interdimensional discrimination protocol

We investigated the effects of interdimensional discrimination training in the temporal generalization gradient. In a matching-to-sample task, pigeons learned to choose key S after a T-s houselight sample and key NS in the absence of the houselight sample. For one group of pigeons, T = 20 s; for another, T = 10 s. Subsequently, houselight duration was varied to obtain temporal generalization gradients. Results showed that (a) proportion S increased as houselight duration ranged from 0 s to T s and then remained high for houselight durations longer than T; (b) the gradients were well described by negative-exponential functions; (c) these non-flat gradients were present from the beginning of testing, and; (d) the average gradients obtained with T = 20 s and T = 10 s overlapped when plotted in relative time. We conclude that temporal control does not require explicit discrimination training along the temporal dimension, and that temporal generalization gradients obtained with an interdimensional protocol show the scalar property of timing. We discuss how these findings challenge current models of timing.