Processing Of Temporal Intervals Research Articles

The role of primary auditory and visual cortices in temporal processing: A tDCS approach

AimMany studies showed that visual stimuli are frequently experienced as shorter than equivalent auditory stimuli. These findings suggest that timing is distributed across many brain areas and that “different clocks” might be involved in temporal processing. The aim of this study is to investigate, with the application of tDCS over V1 and A1, the specific role of primary sensory cortices (either visual or auditory) in temporal processing. MethodForty-eight University students were included in the study. Twenty-four participants were stimulated over A1 and 24 participants were stimulated over V1. Participants performed time bisection tasks, in the visual and the auditory modalities, involving standard durations lasting 300ms (short) and 900ms (long). ResultsWhen tDCS was delivered over A1, no effect of stimulation was observed on perceived duration but we observed higher temporal variability under anodic stimulation compared to sham and higher variability in the visual compared to the auditory modality. When tDCS was delivered over V1, an under-estimation of perceived duration and higher variability was observed in the visual compared to the auditory modality. ConclusionOur results showed more variability of visual temporal processing under tDCS stimulation. These results suggest a modality independent role of A1 in temporal processing and a modality specific role of V1 in the processing of temporal intervals in the visual modality.

A fast BK-type KCa current acts as a postsynaptic modulator of temporal selectivity for communication signals.

Temporal patterns of spiking often convey behaviorally relevant information. Various synaptic mechanisms and intrinsic membrane properties can influence neuronal selectivity to temporal patterns of input. However, little is known about how synaptic mechanisms and intrinsic properties together determine the temporal selectivity of neuronal output. We tackled this question by recording from midbrain electrosensory neurons in mormyrid fish, in which the processing of temporal intervals between communication signals can be studied in a reduced in vitro preparation. Mormyrids communicate by varying interpulse intervals (IPIs) between electric pulses. Within the midbrain posterior exterolateral nucleus (ELp), the temporal patterns of afferent spike trains are filtered to establish single-neuron IPI tuning. We performed whole-cell recording from ELp neurons in a whole-brain preparation and examined the relationship between intrinsic excitability and IPI tuning. We found that spike frequency adaptation of ELp neurons was highly variable. Postsynaptic potentials (PSPs) of strongly adapting (phasic) neurons were more sharply tuned to IPIs than weakly adapting (tonic) neurons. Further, the synaptic filtering of IPIs by tonic neurons was more faithfully converted into variation in spiking output, particularly at short IPIs. Pharmacological manipulation under current- and voltage-clamp revealed that tonic firing is mediated by a fast, large-conductance Ca2+-activated K+ (KCa) current (BK) that speeds up action potential repolarization. These results suggest that BK currents can shape the temporal filtering of sensory inputs by modifying both synaptic responses and PSP-to-spike conversion. Slow SK-type KCa currents have previously been implicated in temporal processing. Thus, both fast and slow KCa currents can fine-tune temporal selectivity.

Left hand dominance affects supra-second time processing.

Previous studies exploring specific brain functions of left- and right-handed subjects have shown variances in spatial and motor abilities that might be explained according to consistent structural and functional differences. Given the role of both spatial and motor information in the processing of temporal intervals, we designed a study aimed at investigating timing abilities in left-handed subjects. To this purpose both left- and right-handed subjects were asked to perform a time reproduction of sub-second vs. supra-second time intervals with their left and right hand. Our results show that during processing of the supra-second intervals left-handed participants sub-estimated the duration of the intervals, independently of the hand used to perform the task, while no differences were reported for the sub-second intervals. These results are discussed on the basis of recent findings on supra-second motor timing, as well as emerging evidence that suggests a linear representation of time with a left-to-right displacement.

Effects of pharmacologically induced changes in NMDA receptor activity on human timing and sensorimotor performance

Unlike processing of time intervals in the range of seconds or more, processing of brief durations in the subsecond range appears to be beyond cognitive control and based on subcortical mechanisms located in the basal ganglia. The present study was designed to evaluate the effects of NMDA receptor activity on temporal processing in the second and subsecond range. In a double-blind crossover design, either 30 mg of the noncompetitive NMDA receptor antagonist memantine or placebo was administered to 32 healthy male volunteers. While memantine induced a marked impairment in temporal processing of intervals in the range of seconds, temporal processing of intervals in the range of milliseconds was not affected. Furthermore, no effect of memantine on speed of information processing could be observed. Speed of motor response execution, however, was significantly enhanced by memantine compared to placebo. The overall pattern of results provides converging evidence for the notion that temporal processing of longer intervals involves higher order working memory functions such as working memory capacity. The absence of an effect on temporal processing of very brief intervals in combination with the beneficial effect on movement time suggests that NMDA receptor activity in the basal ganglia is not directly related to the timing of intervals in the subsecond range.

About hemispheric differences in the processing of temporal intervals

The purpose of the present study was to identify differences between cerebral hemispheres for processing temporal intervals ranging from .9 to 1.4 s. The intervals to be judged were marked by series of brief visual signals located in the left or the right visual field. Series of three (two standards and one comparison) or five intervals (four standards and one comparison), marked by sequences of 4 or 6 signals, were compared. While discrimination, as estimated by d′, was significantly better in the 4-standard than in the 2-standard condition when stimuli were presented in the left visual field (LVF), this number-of-standard effect on discrimination varied with the difficulty levels when the signals were presented in the LVF. Moreover, the discrimination levels were constant for the different base durations with stimuli presented in the LVF, but not with stimuli presented in the right visual field. This article discusses the implication of these findings for the study of hemispheric dominance for temporal processing and for a single-clock hypothesis.

Effects of body core temperature and brain dopamine activity on timing processes in humans

In a placebo-controlled study, the effects of experimentally induced increase in body core temperature and of the dopamine antagonist haloperidol on judgments of an apparent second, a speeded-tapping task, and temporal discrimination of intervals in the range of milliseconds and seconds were investigated in 40 healthy male subjects. A 0.7 °C-increase in body core temperature due to 3-h exposure to an ambient temperature of 52 °C did not cause any statistically significant changes in timing tasks. Unlike heat exposure, 3 mg of haloperidol caused a pronounced impairment of performance on the temporal discrimination of intervals in the range of milliseconds and seconds ( P < 0.01 and P < 0.001, respectively) as well as speeded tapping ( P < 0.05). For temporal discrimination of intervals in the range of seconds, a significant interaction between ambient temperature and haloperidol could be established ( P < 0.05) indicating that haloperidol caused a significant performance decrement only in subjects exposed to an ambient temperature of 28 °C but not in those exposed to 52 °C. The overall pattern of results suggests that temporal processing of intervals in the range of milliseconds can be considered a function of dopaminergic activity in the basal ganglia while temporal processing of longer intervals appears to be cognitively mediated. Furthermore, the hypothesis that timing processes in humans are modulated by changes in body core temperature could not be established.

Effects of benzodiazepine‐induced sedation on temporal processing

AbstractUnlike processing of time intervals in the range of seconds or more, processing of brief durations ranging from approximately 50 to 100 ms appears to be beyond cognitive control and based on neural counting mechanisms. In a placebo‐controlled study either 15 mg of midazolam or placebo were applied to 36 healthy male volunteers to investigate the effect of pharmacologically induced sedation on temporal processing of intervals in the range of milliseconds indicating performance on time perception and in the range of seconds indicating performance on time estimation. In addition, a test battery consisting of subtests measuring speed of information processing and cortical arousal was applied. Midazolam induced a very pronounced decrease in cortical arousal as well as a marked impairment of speed of information processing and performance on time estimation as compared to placebo. Performance on time perception, however, was not affected suggesting that temporal processing of very brief intervals is unrelated to the effective level of cortical arousal. These findings support the notion of two different timing mechanisms underlying time estimation and time perception.