The role of the cerebellum in subsecond time perception: evidence from repetitive transcranial magnetic stimulation

Cerebellar Direct Current Stimulation Reveals the Causal Role of the Cerebellum in Temporal Prediction

Temporal prediction (TP) influences our perception and cognition. The cerebellum could mediate this multi-level ability in a context-dependent manner. We tested whether a modulation of the cerebellar neural activity, induced by transcranial Direct Current Stimulation (tDCS), changed the TP ability according to the temporal features of the context and the duration of target interval. Fifteen healthy participants received anodal, cathodal, and sham tDCS (15 min × 2 mA intensity) over the right cerebellar hemisphere during a TP task. We recorded reaction times (RTs) to a target during the task in two contextual conditions of temporal anticipation: rhythmic (i.e., interstimulus intervals (ISIs) were constant) and single-interval condition (i.e., the estimation of the timing of the target was based on the prior exposure of the train of stimuli). Two ISIs durations were explored: 600 ms (short trials) and 900 ms (long trials). Cathodal tDCS improved the performance during the TP task (shorter RTs) specifically in the rhythmic condition only for the short trials and in the single-interval condition only for the long trials. Our results suggest that the inhibition of cerebellar activity induced a different improvement in the TP ability according to the temporal features of the context. In the rhythmic context, the cerebellum could integrate the temporal estimation with the anticipatory motor responses critically for the short target interval. In the single-interval context, for the long trials, the cerebellum could play a main role in integrating representation of time interval in memory with the elapsed time providing an accurate temporal prediction.

Beyond the ears: A review exploring the interconnected brain behind the hierarchical memory of music

Music is a ubiquitous element of daily life. Understanding how music memory is represented and expressed in the brain is key to understanding how music can influence human daily cognitive tasks. Current music-memory literature is built on data from very heterogeneous tasks for measuring memory, and the neural correlates appear to differ depending on different forms of memory function targeted. Such heterogeneity leaves many exceptions and conflicts in the data underexplained (e.g., hippocampal involvement in music memory is debated). This review provides an overview of existing neuroimaging results from music-memory related studies and concludes that although music is a special class of event in our lives, the memory systems behind it do in fact share neural mechanisms with memories from other modalities. We suggest that dividing music memory into different levels of a hierarchy (structural level and semantic level) helps understand overlap and divergence in neural networks involved. This is grounded in the fact that memorizing a piece of music recruits brain clusters that separately support functions including-but not limited to-syntax storage and retrieval, temporal processing, prediction versus reality comparison, stimulus feature integration, personal memory associations, and emotion perception. The cross-talk between frontal-parietal music structural processing centers and the subcortical emotion and context encoding areas explains why music is not only so easily memorable but can also serve as strong contextual information for encoding and retrieving nonmusic information in our lives.

Sub-second timing irregularities in a simple motor task in autism spectrum disorder: Preliminary effects of intermittent light stimulation

Several authors have contributed extensively to the neurocognitive understanding of timing. In Autism Spectrum Disorder (ASD) on the contrary, internal timing and its functioning is not well understood. In this study, we have adapted a simple finger-tapping motor task, with a timing component, as we aim at understanding whether the processing of time is preserved in this population. We have tested a group of people on the autism spectrum without intellectual disabilities and a control sample recruited from the general population, matched for age, sex, schooling and general cognitive abilities on this task with a learning and testing phase. In the testing phase, we have added two exploratory conditions where participants were exposed to intermittent light stimulation of 4 and 8 Hz. Results show that both in the learning and testing phase, besides troubles in the motor component encountered by the people on the spectrum, their timing component performance was also problematic. This reveals to be especially true for time intervals below the 1 s range, as hypothesized, whereas performance in longer intervals is clearly preserved. It was also observed that the exposure to intermittent light stimulation specifically overcomes the difficulties observed in the autistic group, at the timing components at this millisecond time range. The observed timing difficulties in this group seem to be restricted to the system responsible for the processing of time intervals in the milliseconds range, which helps accommodate disparate findings in the literature.

A meta-analysis of non-invasive brain stimulation (NIBS) effects on cerebellar-associated cognitive processes

Non-invasive brain stimulation (NIBS) techniques, including transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES), have provided valuable insights into the role of the cerebellum in cognitive processes. However, replicating findings from studies involving cerebellar stimulation poses challenges. This meta-analysis investigates the impact of NIBS on cognitive processes associated with the cerebellum. We conducted a systematic search and analyzed 66 studies and 91 experiments involving healthy adults who underwent either TMS or transcranial direct current stimulation (tDCS) targeting the cerebellum. The results indicate that anodal tDCS applied to the medial cerebellum enhances cognitive performance. In contrast, high-frequency TMS disrupts cognitive performance when targeting the lateral cerebellar hemispheres or when employed in online protocols. Similarly, low-frequency TMS and continuous theta burst stimulation (cTBS) diminish performance in offline protocols. Moreover, high-frequency TMS impairs accuracy. By identifying consistent effects and moderators of modulation, this meta-analysis contributes to improving the replicability of studies using NIBS on the cerebellum and provides guidance for future research aimed at developing effective NIBS interventions targeting the cerebellum.

Cerebellar transcranial magnetic stimulation in psychotic disorders: intermittent, continuous, and sham theta-burst stimulation on time perception and symptom severity

Background

The cerebellum contributes to the precise timing of non-motor and motor functions, and cerebellum abnormalities have been implicated in psychosis pathophysiology. In this study, we explored the effects of cerebellar theta burst stimulation (TBS), an efficient transcranial magnetic stimulation protocol, on temporal discrimination and self-reported mood and psychotic symptoms.

Methods

We conducted a case-crossover study in which patients with psychosis (schizophrenias, schizoaffective disorders, or bipolar disorders with psychotic features) were assigned to three sessions of TBS to the cerebellar vermis: one session each of intermittent (iTBS), continuous (cTBS), and sham TBS. Of 28 enrolled patients, 26 underwent at least one TBS session, and 20 completed all three. Before and immediately following TBS, participants rated their mood and psychotic symptoms and performed a time interval discrimination task (IDT). We hypothesized that cerebellar iTBS and cTBS would modulate these measures in opposing directions, with iTBS being adaptive and cTBS maladaptive.

Results

Reaction time (RT) in the IDT decreased significantly after iTBS vs. Sham (LS-mean difference = -73.3, p = 0.0001, Cohen's d = 1.62), after iTBS vs. cTBS (LS-mean difference = -137.6, p < 0.0001, d = 2.03), and after Sham vs. cTBS (LS-mean difference = -64.4, p < 0.0001, d = 1.33). We found no effect on IDT accuracy. We did not observe any effects on symptom severity after correcting for multiple comparisons.

Conclusion

We observed a frequency-dependent dissociation between the effects of iTBS vs. cTBS to the cerebellar midline on the reaction time of interval discrimination in patients with psychosis. iTBS showed improved (adaptive) while cTBS led to worsening (maladaptive) speed of response. These results demonstrate behavioral target engagement in a cognitive dimension of relevance to patients with psychosis and generate testable hypotheses about the potential therapeutic role of cerebellar iTBS in this clinical population.

Clinical Trial Registration

clinicaltrials.gov, identifier NCT02642029.

The role of cerebellum in timing processing: a contingent negative variation study

Time management is an important aspect of human behaviour and cognition. Several brain regions are thought to be involved in motor timing and time estimation tasks. However, subcortical regions such as the basal nuclei and cerebellum seem to play a role in timing control. The aim of this study was to investigate the role of the cerebellum in temporal processing. For this purpose, we transitorily inhibited cerebellar activity by means of cathodal transcranial direct current stimulation (tDCS) and studied the effects of this inhibition on contingent negative variation (CNV) parameters elicited during a S1-S2 motor task in healthy subjects. Sixteen healthy subjects underwent a S1-S2 motor task prior to and after cathodal and sham cerebellar tDCS in separate sessions. The CNV task consisted of a duration discrimination task in which subjects had to determine whether the duration of a probe interval trial was shorter (800 ms), longer (1600 ms), or equal to the target interval of 1200 ms. A reduction in total CNV amplitude emerged only after cathodal tDCS for short and target interval trials, while no differences were detected for the long interval trial. Errors were significantly higher after cathodal tDCS than at baseline evaluation of short and target intervals. No reaction time differences were found for any time interval after the cathodal and sham sessions. These results point to a role of the cerebellum in time perception. In particular, the cerebellum seems to regulate temporal interval discrimination for second and sub-second ranges.

A case study of repetitive transcranial magnetic stimulation for cryptococcal meningitis combined with cognitive impairment

Cryptococcal meningitis (CM) is a central nervous system disease caused by a novel Cryptococcus infection that leads to subacute or chronic inflammatory changes in the nervous system. In this study, we present the case of a woman aged 72 years with CM and severe cognitive impairment and disabilities. The cognitive assessment indicated that, although her cognitive function was impaired, especially executive function, it largely improved after receiving anti-infectious and repetitive transcranial magnetic stimulation, which can alter the membrane potential of the cortical nerve cells by triggering long-term potentiation and depression, modulating and releasing hormones, reducing the level of neuroinflammatory and peripheral blood cytokines, promoting nerve regeneration and synaptic remodeling, and changing the activity of the neural circuitry of the dorsolateral prefrontal cortex. We argue that this case provides a novel method of treatment for patients with CM in conjunction with cognitive impairments.

Cerebellar Transcranial Direct Current Stimulation Does Not Alter Somatosensory Temporal Discrimination Threshold

This study aimed to explore the role of the cerebellum on the somatosensory temporal discrimination (STD) process. Twenty healthy volunteers were enrolled in the study. Each participant was included in three different transcranial direct current stimulation (tDCS) sessions as anodal, cathodal, and sham sessions in randomised order. Anodal and cathodal cerebellar tDCS (cTDCS) were given for 20 min at an intensity of 2 mA. The results of the study indicate no effect of cTDCS on STD. Although the study results show that cTDCS does not affect STD, because of the restricted sample size of the study, it is useful and necessary to investigate this relationship more in depth in a larger healthy subject population using different cTDCS methodologies.

Time in schizophrenia: a link between psychopathology, psychophysics and technology

It has been widely demonstrated that time processing is altered in patients with schizophrenia. This perspective review delves into such temporal deficit and highlights its link to low-level sensory alterations, which are often overlooked in rehabilitation protocols for psychosis. However, if temporal impairment at the sensory level is inherent to the disease, new interventions should focus on this dimension. Beyond more traditional types of intervention, here we review the most recent digital technologies for rehabilitation and the most promising ones for sensory training. The overall aim is to synthesise existing literature on time in schizophrenia linking psychopathology, psychophysics, and technology to help future developments.

A Brief History of Cerebellar Neurostimulation

The first attempts at using electric stimulation to study human brain functions followed the experiments of Luigi Galvani and Giovanni Aldini on animal electricity during the eighteenth century. Since then, the cerebellum has been among the areas that have been studied by invasive and non-invasive forms of electrical and magnetic stimulation. During the nineteenth century, animal experiments were conducted to map the motor-related regions of cerebellar cortex by means of direct electric stimulation. As electric stimulation research on the cerebellum moved into the twentieth century, systematic research of electric cerebellar stimulation led to a better understanding of its effects and mechanism of action. In addition, the clinical potential of cerebellar stimulation in the treatment of motor diseases started to be explored. With the introduction of transcranial electric and magnetic stimulation, cerebellar research moved to non-invasive techniques. During the twenty-first century, following on groundbreaking research that linked the cerebellum to non-motor functions, non-invasive techniques have facilitated research into different aspects of cerebellar functioning. The present review provides a brief historical account of cerebellar neurostimulation and discusses current challenges and future direction in this field of research.

A systematic examination of the neural correlates of subjective time perception with fMRI and tDCS

The ability to keep track of time is one of the fundamental human behaviours that enhance survival in the wild. It is still an essential skill that enables an individual to function well in modern society. In the present study, we tested the attentional gate model, one of the most common conceptual frameworks in studies of subjective time perception. Its utility has been well established, but it has been criticised for its lack of neurophysiological support; few studies attempted to systematically identify its components and their neural correlates. Previous studies established that the dorsolateral prefrontal cortex (DLPFC) was associated with working memory tasks and a correlation between activity in the cerebellum and the timing of tasks. An fMRI study was conducted to confirm that these two cortical regions were activated during the execution of a new time discrimination task that considers individual variations in subjective time perception. Simulations were conducted to optimize the electrode placement in order to maximize the electric fields of tDCS perturbation to these two areas. According to the attentional gate model, hypotheses about tDCS perturbation to subjective time perception, attention and working memory were formulated and tested. Attention and working memory were measured by the attention network and N-back tasks. There are weak effects to the perceived subjective equivalent and the reaction time in the attention network task, but both are not statistically significant after correction for multiple comparisons. Exploration analyses show a link between attention and subjective time perception after tDCS perturbation. To conclude, the results do not support the attentional gate model, but show a linkage between attention and subjective time perception in terms of similar neural circuits and their relationships under certain circumstances.

Timing dysfunction and cerebellar resting state functional connectivity abnormalities in youth at clinical high-risk for psychosis

BACKGROUND

Consistent with pathophysiological models of psychosis, temporal disturbances in schizophrenia spectrum populations may reflect abnormal cortical (e.g. prefrontal cortex) and subcortical (e.g. striatum) cerebellar connectivity. However, few studies have examined associations between cerebellar connectivity and timing dysfunction in psychosis populations, and none have been conducted in youth at clinical high-risk (CHR) for psychosis. Thus, it is currently unknown if impairments in temporal processes are present in CHR youth or how they may be associated with cerebellar connectivity and worsening of symptoms.

METHODS

A total of 108 (56 CHR/52 controls) youth were administered an auditory temporal bisection task along with a resting state imaging scan to examine cerebellar resting state connectivity. Positive and negative symptoms at baseline and 12 months later were also quantified.

RESULTS

Controlling for alcohol and cannabis use, CHR youth exhibited poorer temporal accuracy compared to controls, and temporal accuracy deficits were associated with abnormal connectivity between the bilateral anterior cerebellum and a right caudate/nucleus accumbens striatal cluster. Poor temporal accuracy accounted for 11% of the variance in worsening of negative symptoms over 12 months.

CONCLUSIONS

Behavioral findings suggest CHR youth perceive durations of auditory tones as shortened compared to objective time, which may indicate a slower internal clock. Poorer temporal accuracy in CHR youth was associated with abnormalities in brain regions involved in an important cerebellar network implicated in prominent pathophysiological models of psychosis. Lastly, temporal accuracy was associated with worsening of negative symptoms across 12 months, suggesting temporal dysfunction may be sensitive to illness progression.

Multiple Irrelevant Duration Information Affects the Perception of Relevant Duration Information: Interference With Selective Processing of Duration

In the human visual environment, the ability to perceive only relevant duration is important for various activities. However, a relatively small number of studies have investigated how humans process multiple durations, in comparison with the processing of one or two durations. We investigated the effects of multiple irrelevant durations on the perception of relevant duration. In four behavioral experiments, the participants were instructed to pay attention to a target stimulus while ignoring the distractors; then, they reproduced the target duration. We manipulated three aspects of the distractors: number, duration range, and cortical distance to the target. The results showed that the presence of multiple irrelevant durations interfered with the processing of relevant duration in terms of the mean perceived duration and the variability of the perceived duration. The interference was directional; that is, longer (shorter) irrelevant durations made the reproduced durations longer (shorter). Moreover, the interference was not likely to depend on the cortical distance between the target and the distractors, suggesting an involvement of relatively higher cortical areas. These results demonstrate that multiple irrelevant duration information affects the temporal processing of relevant duration information and suggest that multiple independent clocks assigned to each of the durations may not exist.

The Neural Correlates of Time: A Meta-analysis of Neuroimaging Studies

During the last two decades, our inner sense of time has been repeatedly studied with the help of neuroimaging techniques. These investigations have suggested the specific involvement of different brain areas in temporal processing. At least two distinct neural systems are likely to play a role in measuring time: One is mainly constituted of subcortical structures and is supposed to be more related to the estimation of time intervals below the 1-sec range (subsecond timing tasks), and the other is mainly constituted of cortical areas and is supposed to be more related to the estimation of time intervals above the 1-sec range (suprasecond timing tasks). Tasks can then be performed in motor or nonmotor (perceptual) conditions, thus providing four different categories of time processing. Our meta-analytical investigation partly confirms the findings of previous meta-analytical works. Both sub- and suprasecond tasks recruit cortical and subcortical areas, but subcortical areas are more intensely activated in subsecond tasks than in suprasecond tasks, which instead receive more contributions from cortical activations. All the conditions, however, show strong activations in the SMA, whose rostral and caudal parts have an important role not only in the discrimination of different time intervals but also in relation to the nature of the task conditions. This area, along with the striatum (especially the putamen) and the claustrum, is supposed to be an essential node in the different networks engaged when the brain creates our sense of time.

Impaired decision-making and time perception in individuals with stroke: Behavioral and neural correlates

Several studies have demonstrated that stroke subjects present impairment of functions related to decision-making and timing, involving the information processing in the neural circuits of the cerebellum in association with the prefrontal cortex. This review is aimed to identify the gaps, and demonstrate a better understanding of decision-making and timing functions in the patients with stroke. Electronic literature database was searched and the findings of relevant studies were used to explore the mechanisms of decision-making and timing in patients with stroke, as well as the circuit connections in timing mediated by prefrontal cortex and cerebellum. A literature review was conducted with 65 studies that synthesized findings on decision-making and time perception in individuals with stroke. Types of neurobiological modalities in this study included: Relationships among decision-making, time perception, related cognitive aspects (such as discrimination tasks, verbal estimation, bisection tasks, time production and motor reproduction), and motor control. We demonstrate that the timing processes are important for the performance in cognitive tasks and that the cerebellum and prefrontal cortex are involved in decision-making and time perception. In the context, the decision-making is impaired in stroke patients has a great impact on executive functions, and this seems to be important in determining neurobiological aspects relevant to the time interval interpretation.

Movement-Contingent Time Flow in Virtual Reality Causes Temporal Recalibration

Virtual reality (VR) provides a valuable research tool for studying what occurs when sensorimotor feedback loops are manipulated. Here we measured whether exposure to a novel temporal relationship between action and sensory reaction in VR causes recalibration of time perception. We asked 31 participants to perform time perception tasks where the interval of a moving probe was reproduced using continuous or discrete motor methods. These time perception tasks were completed pre- and post-exposure to dynamic VR content in a block-counterbalanced order. One group of participants experienced a standard VR task ("normal-time"), while another group had their real-world movements coupled to the flow of time in the virtual space ("movement contingent time-flow; MCTF"). We expected this novel action-perception relationship to affect continuous motor time perception performance, but not discrete motor time perception. The results indicated duration-dependent recalibration specific to a motor task involving continuous movement such that the probe intervals were under-estimated by approximately 15% following exposure to VR with the MCTF manipulation. Control tasks in VR and non-VR settings produced similar results to those of the normal-time VR group, confirming the specificity of the MCTF manipulation. The findings provide valuable insights into the potential impact of VR on sensorimotor recalibration. Understanding this process will be valuable for the development and implementation of rehabilitation practices.

Targeting the Cerebellum by Noninvasive Neurostimulation: a Review

Transcranial magnetic and electric stimulation of the brain are novel and highly promising techniques currently employed in both research and clinical practice. Improving or rehabilitating brain functions by modulating excitability with these noninvasive tools is an exciting new area in neuroscience. Since the cerebellum is closely connected with the cerebral regions subserving motor, associative, and affective functions, the cerebello-thalamo-cortical pathways are an interesting target for these new techniques. Targeting the cerebellum represents a novel way to modulate the excitability of remote cortical regions and their functions. This review brings together the studies that have applied cerebellar stimulation, magnetic and electric, and presents an overview of the current knowledge and unsolved issues. Some recommendations for future research are implemented as well.

The cerebellum's contribution to beat interval discrimination

From expert percussionists to individuals who cannot dance, there are widespread differences in people's abilities to perceive and synchronize with a musical beat. The aim of our study was to identify candidate brain regions that might be associated with these abilities. For this purpose, we used Voxel-Based-Morphometry to correlate inter-individual differences in performance on the Harvard Beat Assessment Tests (H-BAT) with local inter-individual variations in gray matter volumes across the entire brain space in 60 individuals. Analysis revealed significant co-variations between performances on two perceptual tasks of the Harvard Beat Assessment Tests associated with beat interval change discrimination (faster, slower) and gray matter volume variations in the cerebellum. Participant discrimination thresholds for the Beat Finding Interval Test (quarter note beat) were positively associated with gray matter volume variation in cerebellum lobule IX in the left hemisphere and crus I bilaterally. Discrimination thresholds for the Beat Interval Test (simple series of tones) revealed the tendency for a positive association with gray matter volume variations in crus I/II of the left cerebellum. Our results demonstrate the importance of the cerebellum in beat interval discrimination skills, as measured by two perceptual tasks of the Harvard Beat Assessment Tests. Current findings, in combination with evidence from patients with cerebellar degeneration and expert dancers, suggest that cerebellar gray matter and overall cerebellar integrity are important for temporal discrimination abilities.

Probing the timing network: A continuous theta burst stimulation study of temporal categorization

Time perception in the millisecond and second ranges is thought to be processed by different neural mechanisms. However, whether there is a sharp boundary between these ranges and whether they are implemented in the same, overlapped or separate brain areas is still not certain. To probe the role of the right dorsolateral prefrontal cortex (dlPFC), the right supplementary motor area (SMA), and the cerebellum on time perception, we temporarily altered their activity on healthy volunteers on separate sessions using transcranial magnetic stimulation with the continuous Theta Burst Stimulation (cTBS) protocol. A control session was reserved for the stimulation of the primary somatosensory cortex (S1). Before and after stimulation, participants were tested on a temporal categorization task using intervals in the hundreds and thousands of milliseconds ranges, as well as on a pitch categorization task which was used as a further control. We then looked for changes in the Relative Threshold and the Constant Error, which, respectively, reflect participants' sensitivity to interval duration and their accuracy at setting an interval that acts as a boundary between categories. We found that after cTBS in all of the studied regions, the Relative Threshold, but not the Constant Error, was affected and only when hundreds of milliseconds intervals were being categorized. Categorization of thousands of milliseconds intervals and of pitch was not affected. These results suggest that the fronto-cerebellar circuit is particularly involved in the estimation of intervals in the hundreds of milliseconds range.

When one is Enough: Impaired Multisensory Integration in Cerebellar Agenesis

In the last two decades, an intriguing shift in the understanding of the cerebellum has led to consider the nonmotor functions of this structure. Although various aspects of perceptual and sensory processing have been linked to the cerebellar activity, whether the cerebellum is essential for binding information from different sensory modalities remains uninvestigated. Multisensory integration (MSI) appears very early in the ontogenesis and is critical in several perceptual, cognitive, and social domains. For the first time, we investigated MSI in a rare case of cerebellar agenesis without any other associated brain malformations. To this aim, we measured reaction times (RTs) after the presentation of visual, auditory, and audiovisual stimuli. A group of neurotypical age-matched individuals was used as controls. Although we observed the typical advantage of the auditory modality relative to the visual modality in our patient, a clear impairment in MSI was found. Beyond the obvious prudence necessary for inferring definitive conclusions from this single-case picture, this finding is of interest in the light of reduced MSI abilities reported in several neurodevelopmental and psychiatric disorders-such as autism, dyslexia, and schizophrenia-in which the cerebellum has been implicated.

Neural Networks for Time Perception and Working Memory

Time is an important concept which determines most human behaviors, however questions remain about how time is perceived and which areas of the brain are responsible for time perception. The aim of this study was to evaluate the relationship between time perception and working memory in healthy adults. Functional magnetic resonance imaging (fMRI) was used during the application of a visual paradigm. In all of the conditions, the participants were presented with a moving black rectangle on a gray screen. The rectangle was obstructed by a black bar for a time period and then reappeared again. During different conditions, participants (n = 15, eight male) responded according to the instructions they were given, including details about time and the working memory or dual task requirements. The results showed activations in right dorsolateral prefrontal and right intraparietal cortical networks, together with the anterior cingulate cortex (ACC), anterior insula and basal ganglia (BG) during time perception. On the other hand, working memory engaged the left prefrontal cortex, ACC, left superior parietal cortex, BG and cerebellum activity. Both time perception and working memory were related to a strong peristriate cortical activity. On the other hand, the interaction of time and memory showed activity in the intraparietal sulcus (IPS) and posterior cingulate cortex (PCC). These results support a distributed neural network based model for time perception and that the intraparietal and posterior cingulate areas might play a role in the interface of memory and timing.

Impaired Spatio-Temporal Predictive Motor Timing Associated with Spinocerebellar Ataxia Type 6

Many daily life activities demand precise integration of spatial and temporal information of sensory inputs followed by appropriate motor actions. This type of integration is carried out in part by the cerebellum, which has been postulated to play a central role in learning and timing of movements. Cerebellar damage due to atrophy or lesions may compromise forward-model processing, in which both spatial and temporal cues are used to achieve prediction for future motor states. In the present study we sought to further investigate the cerebellar contribution to predictive and reactive motor timing, as well as to learning of sequential order and temporal intervals in these tasks. We tested patients with spinocerebellar ataxia type 6 (SCA6) and healthy controls for two related motor tasks; one requiring spatio-temporal prediction of dynamic visual stimuli and another one requiring reactive timing only. We found that healthy controls established spatio-temporal prediction in their responses with high temporal precision, which was absent in the cerebellar patients. SCA6 patients showed lower predictive motor timing, coinciding with a reduced number of correct responses during the ‘anticipatory’ period on the task. Moreover, on the task utilizing reactive motor timing functions, control participants showed both sequence order and temporal interval learning, whereas patients only showed sequence order learning. These results suggest that SCA6 affects predictive motor timing and temporal interval learning. Our results support and highlight cerebellar contribution to timing and argue for cerebellar engagement during spatio-temporal prediction of upcoming events.

Ultrasound treatment: effect on physicochemical, microbial and antioxidant properties of cherry (Prunus avium)

The cherry was treated with ultrasonic waves (33 kHz, 60 W) at different time intervals (10, 20, 30, 40, 60 min) and study was carried out to analyze the change in physico-chemical properties (TSS, pH, color, acidity and firmness), antioxidant potential and microbial load of the fruit during the storage period of 15 days at 4 °C. It was observed that ultrasound treatment (US) between 30 and 40 min showed better retention of color of the fruit during the storage period. The antioxidant assays (DPPH, ABTS and TPC) also increased significantly (P ≤ 0.05) up to 40 min, however the firmness of the fruit was affected and it showed a significant decrease beyond 20 min of US treatment. The sample with 40 min US treatment showed significantly less microbial load than other samples. The 20-40 min US treatment time (33 kHz, 60 W) was suggested for preservation of cherry during the storage at 4 °C.

Perceptual versus motor spatiotemporal interactions in duration reproduction across two hands

The possibility of spatiotemporal interactions in motor action that are comparable with the perceptual kappa effect was tested in the present study. In the kappa effect, the empty duration between two successive stimuli is overestimated when the spatial distance between these stimuli is increased. Indeed, when participants reproduced the standard (empty) duration, delivering two tactile stimuli to different hands resulted in a longer reproduced duration than delivering both stimuli to the same hand, regardless of how long the standard was. However, when a spatial factor during motor action (reproduction) was manipulated by letting participants use an identical hand or different hands for two button pushes reproducing the standard, the different-hand condition yielded a shorter reproduced duration than the identical-hand condition when the standard was 1000 ms or more. More specifically, this decrement in the reproduced duration grew linearly with the standard, suggesting that a given space increases the “rate” of an internal timer during motor action. Because each tick of the timer was accelerated, the total error causing an earlier push of the second button was increased with the standard. A pacemaker-counter model was adopted to explain the differences between the perceptual and the motor spatiotemporal interactions.

Neural Network of Predictive Motor Timing in the Context of Gender Differences

Time perception is an essential part of our everyday lives, in both the prospective and the retrospective domains. However, our knowledge of temporal processing is mainly limited to the networks responsible for comparing or maintaining specific intervals or frequencies. In the presented fMRI study, we sought to characterize the neural nodes engaged specifically in predictive temporal analysis, the estimation of the future position of an object with varying movement parameters, and the contingent neuroanatomical signature of differences in behavioral performance between genders. The established dominant cerebellar engagement offers novel evidence in favor of a pivotal role of this structure in predictive short-term timing, overshadowing the basal ganglia reported together with the frontal cortex as dominant in retrospective temporal processing in the subsecond spectrum. Furthermore, we discovered lower performance in this task and massively increased cerebellar activity in women compared to men, indicative of strategy differences between the genders. This promotes the view that predictive temporal computing utilizes comparable structures in the retrospective timing processes, but with a definite dominance of the cerebellum.

Inactivation of Cerebellar Cortical Crus II Disrupts Temporal Processing of Absolute Timing but not Relative Timing in Voluntary Movements

Several recent studies have demonstrated that the cerebellum plays an important role in temporal processing at the scale of milliseconds. However, it is not clear whether intrinsic cerebellar function involves the temporal processing of discrete or continuous events. Temporal processing during discrete events functions by counting absolute time like a stopwatch, while during continuous events it measures events at intervals. During the temporal processing of continuous events, animals might respond to rhythmic timing of sequential responses rather than to the absolute durations of intervals. Here, we tested the contribution of the cerebellar cortex to temporal processing of absolute and relative timings in voluntary movements. We injected muscimol and baclofen to a part of the cerebellar cortex of rats. We then tested the accuracy of their absolute or relative timing prediction using two timing tasks requiring almost identical reaching movements. Inactivation of the cerebellar cortex disrupted accurate temporal prediction in the absolute timing task. The rats formed two groups based on the changes to their timing accuracy following one of two distinct patterns which can be described as longer or shorter declines in the accuracy of learned intervals. However, a part of the cerebellar cortical inactivation did not affect the rats' performance of relative timing tasks. We concluded that a part of the cerebellar cortex, Crus II, contributes to the accurate temporal prediction of absolute timing and that the entire cerebellar cortex may be unnecessary in cases in which accurately knowing the absolute duration of an interval is not required for temporal prediction.

The number-time interaction depends on relative magnitude in the suprasecond range

Numerical representations influence temporal processing. Previous studies have consistently shown that larger numbers are perceived to last longer than smaller ones. However, whether this effect is modulated by the absolute or relative magnitudes of the numbers has yet to be fully understood. Here, participants observed single- and double-digit Arabic numerals in separate experimental blocks and reproduced stimulus duration of 600 or 1200 ms. Our results replicated previous findings that the duration of larger numbers was reproduced longer than that of smaller numbers within each digit set. Although the effect of numerical magnitude across single- and double-digit numerals was found when the numerals were presented for 600 ms, the difference was negligible when they were presented for 1200 ms, suggesting that relative magnitude is an important factor in the number-time interaction in the suprasecond range. These results suggest that contextual influence on number-time interaction may depend on the actual stimulus duration.

Reduced attention-driven auditory sensitivity in hallucination-prone individuals

BACKGROUND

Evidence suggests that auditory hallucinations may result from abnormally enhanced auditory sensitivity.

AIMS

To investigate whether there is an auditory processing bias in healthy individuals who are prone to experiencing auditory hallucinations.

METHOD

Two hundred healthy volunteers performed a temporal order judgement task in which they determined whether an auditory or a visual stimulus came first under conditions of directed attention ('attend-auditory' and 'attend-visual' conditions). The Launay-Slade Hallucination Scale was used to divide the sample into high and low hallucination-proneness groups.

RESULTS

The high hallucination-proneness group exhibited a reduced sensitivity to auditory stimuli under the attend-auditory condition. By contrast, attention-directed visual sensitivity did not differ significantly between groups.

CONCLUSIONS

Healthy individuals prone to hallucinatory experiences may possess a bias in attention towards internal auditory stimuli at the expense of external sounds. Interventions involving the redistribution of attentional resources would have therapeutic benefit in patients experiencing auditory hallucinations.

The duality of temporal encoding - the intrinsic and extrinsic representation of time

While time is well acknowledged for having a fundamental part in our perception, questions on how it is represented are still matters of great debate. One of the main issues in question is whether time is represented intrinsically at the neural level, or is it represented within dedicated brain regions. We used an fMRI block design to test if we can impose covert encoding of temporal features of faces and natural scenes stimuli within category selective neural populations by exposing subjects to four types of temporal variance, ranging from 0% up to 50% variance. We found a gradual increase in neural activation associated with the gradual increase in temporal variance within category selective areas. A second level analysis showed the same pattern of activations within known brain regions associated with time representation, such as the Cerebellum, the Caudate, and the Thalamus. We concluded that temporal features are integral to perception and are simultaneously represented within category selective regions and globally within dedicated regions. Our second conclusion, drown from our covert procedure, is that time encoding, at its basic level, is an automated process that does not require attention allocated toward the temporal features nor does it require dedicated resources.

Evidence for Multiple Rhythmic Skills

Rhythms, or patterns in time, play a vital role in both speech and music. Proficiency in a number of rhythm skills has been linked to language ability, suggesting that certain rhythmic processes in music and language rely on overlapping resources. However, a lack of understanding about how rhythm skills relate to each other has impeded progress in understanding how language relies on rhythm processing. In particular, it is unknown whether all rhythm skills are linked together, forming a single broad rhythmic competence, or whether there are multiple dissociable rhythm skills. We hypothesized that beat tapping and rhythm memory/sequencing form two separate clusters of rhythm skills. This hypothesis was tested with a battery of two beat tapping and two rhythm memory tests. Here we show that tapping to a metronome and the ability to adjust to a changing tempo while tapping to a metronome are related skills. The ability to remember rhythms and to drum along to repeating rhythmic sequences are also related. However, we found no relationship between beat tapping skills and rhythm memory skills. Thus, beat tapping and rhythm memory are dissociable rhythmic aptitudes. This discovery may inform future research disambiguating how distinct rhythm competencies track with specific language functions.

Time perception impairment in early-to-moderate stages of Huntington's disease is related to memory deficits

Huntington's disease (HD) primarily affects striatum and prefrontal dopaminergic circuits which are fundamental neural correlates of the timekeeping mechanism. The few studies on HD mainly investigated motor timing performance in second durations. The present work explored time perception in early-to-moderate symptomatic HD patients for seconds and milliseconds with the aim to clarify which component of the scalar expectancy theory (SET) is mainly responsible for HD timing defect. Eleven HD patients were compared to 11 controls employing two separate temporal bisection tasks in second and millisecond ranges. Our results revealed the same time perception deficits for seconds and milliseconds in HD patients. Time perception impairment in early-to-moderate stages of Huntington's disease is related to memory deficits. Furthermore, both the non-systematical defect of temporal sensitivity and the main impairment of timing performance in the extreme value of the psychophysical curves suggested an HD deficit in the memory component of the SET. This result was further confirmed by the significant correlations between time perception performance and long-term memory test scores. Our findings added important preliminary data for both a deeper comprehension of HD time-keeping deficits and possible implications on neuro-rehabilitation practices.

Consensus paper: the role of the cerebellum in perceptual processes

Various lines of evidence accumulated over the past 30 years indicate that the cerebellum, long recognized as essential for motor control, also has considerable influence on perceptual processes. In this paper, we bring together experts from psychology and neuroscience, with the aim of providing a succinct but comprehensive overview of key findings related to the involvement of the cerebellum in sensory perception. The contributions cover such topics as anatomical and functional connectivity, evolutionary and comparative perspectives, visual and auditory processing, biological motion perception, nociception, self-motion, timing, predictive processing, and perceptual sequencing. While no single explanation has yet emerged concerning the role of the cerebellum in perceptual processes, this consensus paper summarizes the impressive empirical evidence on this problem and highlights diversities as well as commonalities between existing hypotheses. In addition to work with healthy individuals and patients with cerebellar disorders, it is also apparent that several neurological conditions in which perceptual disturbances occur, including autism and schizophrenia, are associated with cerebellar pathology. A better understanding of the involvement of the cerebellum in perceptual processes will thus likely be important for identifying and treating perceptual deficits that may at present go unnoticed and untreated. This paper provides a useful framework for further debate and empirical investigations into the influence of the cerebellum on sensory perception.

The cerebellum predicts the temporal consequences of observed motor acts

It is increasingly clear that we extract patterns of temporal regularity between events to optimize information processing. The ability to extract temporal patterns and regularity of events is referred as temporal expectation. Temporal expectation activates the same cerebral network usually engaged in action selection, comprising cerebellum. However, it is unclear whether the cerebellum is directly involved in temporal expectation, when timing information is processed to make predictions on the outcome of a motor act. Healthy volunteers received one session of either active (inhibitory, 1 Hz) or sham repetitive transcranial magnetic stimulation covering the right lateral cerebellum prior the execution of a temporal expectation task. Subjects were asked to predict the end of a visually perceived human body motion (right hand handwriting) and of an inanimate object motion (a moving circle reaching a target). Videos representing movements were shown in full; the actual tasks consisted of watching the same videos, but interrupted after a variable interval from its onset by a dark interval of variable duration. During the 'dark' interval, subjects were asked to indicate when the movement represented in the video reached its end by clicking on the spacebar of the keyboard. Performance on the timing task was analyzed measuring the absolute value of timing error, the coefficient of variability and the percentage of anticipation responses. The active group exhibited greater absolute timing error compared with the sham group only in the human body motion task. Our findings suggest that the cerebellum is engaged in cognitive and perceptual domains that are strictly connected to motor control.

fMRI identifies the right inferior frontal cortex as the brain region where time interval processing is altered by negative emotional arousal

The reason why human beings are inclined to overestimate the duration of highly arousing negative events remains enigmatic. The issue about what neurocognitive mechanisms and neural structures support the connection between time perception and emotion was addressed here by an event-related neuroimaging study involving a localizer task, followed by the main experiment. The localizer task, in which participants had to categorize either the duration or the average color of visual stimuli aimed at identifying the neural structures constitutive of a duration-specific network. The aim of the main experiment, in which participants had to categorize the presentation time of either neutral or emotionally negative visual stimuli, was to unmask which parts of the previously identified duration-specific network are sensitive to emotionally negative arousal. The duration-specific network that we uncovered from the localizer task comprised the cerebellum bilaterally as well as the orbitofrontal, the anterior cingulate, the anterior insular, and the inferior frontal cortices in the right hemisphere. Strikingly, the imaging data from the main experiment underscored that the right inferior frontal cortex (IFC) was the only region within the duration-specific network whose activity was increased in the face of emotionally negative pictures compared to neutral ones. Remarkably too, the extent of neural activation induced by emotionally negative pictures (compared to neutral ones) in this region correlated with a behavioral index reflecting the extent to which emotionally negative pictures were overestimated compared to neutral ones. The results are discussed in relation to recent models and studies suggesting that the right anterior insular cortex/IFC is of central importance in time perception.

Perceiving the passage of time: neural possibilities

Although the study of time has been central to physics and philosophy for millennia, questions of how time is represented in the brain and how this representation is related to time perception have only recently started to be addressed. Emerging evidence subtly yet profoundly challenges our intuitive notions of time over short scales, offering insight into the nature of the brain's representation of time. Numerous different models, specified at the neural level, of how the brain may keep track of time have been proposed. These models differ in various ways, such as whether time is represented by a centralized or distributed neural system, or whether there are neural systems dedicated to the problem of timing. This paper reviews the insight offered by behavioral experiments and how these experiments refute and guide some of the various models of the brain's representation of time.

Space, time, and causality in the human brain

The ability to perceive causality is a central human ability constructed from elemental spatial and temporal information present in the environment. Although the nature of causality has captivated philosophers and scientists since antiquity, the neural correlates of causality remain poorly understood. In the present study, we used functional magnetic resonance imaging (fMRI) to generate hypotheses for candidate brain regions related to component processes important for perceptual causality in the human brain: elemental space perception, elemental time perception, and decision-making (Experiment 1; n=16). We then used transcranial direct current stimulation (tDCS) to test neural hypotheses generated from the fMRI experiment (Experiment 2; n=16). In both experiments, participants judged causality in billiard-ball style launching events; a blue ball approaches and contacts a red ball. Spatial and temporal contributions to causal perception were assessed by parametrically varying the spatial linearity and the temporal delays of the movement of the balls. Experiment 1 demonstrated unique patterns of activation correlated with spatial, temporal, and decision-making components of causality perception. Using tDCS, we then tested hypotheses for the specific roles of the parietal and frontal cortices found in the fMRI experiment. Parietal stimulation only decreased participants' perception of causality based on spatial violations, while frontal stimulation made participants less likely to perceive causality based on violations of space and time. Converging results from fMRI and tDCS indicate that parietal cortices contribute to causal perception because of their specific role in processing spatial relations, while the frontal cortices contribute more generally, consistent with their role in decision-making.

Cerebellar vermis plays a causal role in visual motion discrimination

Cerebellar patients have been found to show deficits in visual motion discrimination, suggesting that the cerebellum may play a role in visual sensory processing beyond mediating motor control. Here we show that triple-pulse online transcranial magnetic stimulation (TMS) over cerebellar vermis but not over the cerebellar hemispheres significantly impaired motion discrimination. Critically, the interference caused by vermis TMS on motion discrimination did not depend on an indirect effect of TMS over nearby visual areas, as demonstrated by a control experiment in which TMS over V1 but not over cerebellar vermis significantly impaired orientation discrimination. These findings demonstrate the causal role of the cerebellar vermis in visual motion processing in neurologically normal participants.

Dissociable neuroanatomical correlates of subsecond and suprasecond time perception

The ability to estimate durations varies across individuals. Although previous studies have reported that individual differences in perceptual skills and cognitive capacities are reflected in brain structures, it remains unknown whether timing abilities are also reflected in the brain anatomy. Here, we show that individual differences in the ability to estimate subsecond and suprasecond durations correlate with gray matter (GM) volume in different parts of cortical and subcortical areas. Better ability to discriminate subsecond durations was associated with a larger GM volume in the bilateral anterior cerebellum, whereas better performance in estimating the suprasecond range was associated with a smaller GM volume in the inferior parietal lobule. These results indicate that regional GM volume is predictive of an individual's timing abilities. These morphological results support the notion that subsecond durations are processed in the motor system, whereas suprasecond durations are processed in the parietal cortex by utilizing the capacity of attention and working memory to keep track of time.

Getting the timing right: experimental protocols for investigating time with functional neuroimaging and psychopharmacology

Functional Magnetic Resonance Imaging (fMRI) is an effective tool for identifying brain areas and networks implicated in human timing. But fMRI is not just a phrenological tool: by careful design, fMRI can be used to disentangle discrete components of a timing task and control for the underlying cognitive processes (e.g. sustained attention and WM updating) that are critical for estimating stimulus duration in the range of hundreds of milliseconds to seconds. Moreover, the use of parametric designs and correlational analyses allows us to better understand not just where, but also how, the brain processes temporal information. In addition, by combining fMRI with psychopharmacological manipulation, we can begin to uncover the complex relationship between cognition, neurochemistry and anatomy in the healthy human brain. This chapter provides an overview of some of the key findings in the functional imaging literature of both duration estimation and temporal prediction, and outlines techniques that can be used to allow timing-related activations to be interpreted more unambiguously. In our own studies, we have found that estimating event duration, whether that estimate is provided by a motor response or a perceptual discrimination, typically recruits basal ganglia, SMA and right inferior frontal cortex, and can be modulated by dopaminergic activity in these areas. By contrast, orienting attention to predictable moments in time in order to optimize behaviour, whether that is to speed motor responding or improve perceptual accuracy, recruits left inferior parietal cortex.

Transcranial Magnetic Stimulation Studies of Human Time Perception: A Primer

The study of the neural basis of time perception has seen a resurgence of interest within the past decade. A variety of these studies have included the use of transcranial magnetic stimulation (TMS), a noninvasive technique for stimulating discrete regions of the surface of the brain. Here, the results of these studies are reviewed and their conclusions are interpreted within a context-dependent framework. However, the use of TMS as an investigatory technique has much unexplored potential that may be particularly beneficial to the study of time perception. As such, considerations are made regarding the design of TMS studies of time perception and future directions are outlined that may be utilized to further elucidate the neural basis of timing in the human brain.

The pattern of striatal dopaminergic denervation explains sensorimotor synchronization accuracy in Parkinson's disease

The basal ganglia are thought to play a critical role in duration perception and production. However, experimental evidence for impaired temporal processing in Parkinson's disease (PD) patients is mixed. This study examined the association between striatal dopaminergic denervation in PD patients and sensorimotor synchronization. Twenty-eight mild-to-moderate stage PD patients synchronized finger taps to tone sequences of either 500 ms, 1000 ms or 1500 ms time intervals while ON levodopa (l-DOPA) or placebo pill (on separate test days) with the index finger of their more and less affected hands. We measured the accuracy and variability of synchronization. In a separate session, patients underwent (11)C-dihydrotetrabenazine ((11)C-DTBZ) PET scanning to measure in vivo striatal dopaminergic denervation. Patients were less accurate synchronizing to the 500 ms target time interval, compared to the 1000 ms and 1500 ms time intervals, but neither medication state nor hand affected accuracy; medication state, hand nor the target time interval affected synchronization variability. Regression analyses revealed no strong relationships between synchronization accuracy or variability and striatal dopaminergic denervation. We performed a cluster analysis on the degree of dopaminergic denervation to determine whether patient subgroup differences underlie our results. Three patient subgroups showed behavioral differences in synchronization accuracy, but not variability, paralleling their pattern of denervation. These findings provide further evidence for the role of the basal ganglia and dopamine in duration production and suggest that the degree of striatal dopaminergic denervation may explain the heterogeneity of performance between PD patients on the sensorimotor synchronization task.

Long latency electromyographic response induced by transcranial magnetic stimulation over the cerebellum preferentially appears during continuous visually guided manual tracking task

We investigated whether long latency motor response induced by transcranial magnetic stimulation over the cerebellum (C-TMS) preferentially appears during a continuous visually guided manual tracking task, and whether it originates in a concomitantly evoked neck twitch. C-TMS or magnetic stimulation over the neck (N-MS) was delivered during one of four tasks: a continuous or discrete visually guided manual tracking task, or phasic or tonic contraction of the first dorsal interosseous muscle. The probability of long latency fluctuation of index finger movement induced by C-TMS was not significantly different from that induced by N-MS, but the probability of long latency fluctuation induced by C-TMS and that induced by N-MS was significantly higher than that induced by sham TMS during all the tasks. The probability of long latency electromyographic response in the first dorsal interosseous muscle induced by C-TMS was significantly higher than that induced by N-MS and that induced by sham TMS during the continuous visually guided manual tracking task. Such significant differences were not present during the other tasks. Long latency electromyographic response induced by C-TMS preferentially appears during the continuous visually guided manual tracking task and is not explained by a concomitantly evoked neck twitch.

The difference in speed sequence influences perceived duration

Perceived duration of a moving stimulus increases with the speed of the motion. However, a recent study found that the perceived duration of a decelerating stimulus was longer than that of an accelerating one, even though their averaged speed was identical (Matthews 2011 Journal of Experimental Psychology: Human Perception and Performance 37 1617-1627). We conducted three experiments to discover how this speed-change-induced time distortion occurs. We found that the perceived duration of a decelerating motion was longer than that of an accelerating one both in sub-second and supra-second presentation duration conditions, when speed changed linearly over time (experiment 1). The differences could not be explained by the differences in average perceived speed between them (experiment 2). Moreover, the perceived duration of a decelerating motion was also longer than that of an accelerating one, even when speed changed once during the presentation duration (experiment 3). These results suggest that average speed differences in the early and late parts of the presentation duration are important for the occurrence of the speed-change-induced time distortion.

Dichotomy in perceptual learning of interval timing: calibration of mean accuracy and precision differ in specificity and time course

Our brain is inexorably confronted with a dynamic environment in which it has to fine-tune spatiotemporal representations of incoming sensory stimuli and commit to a decision accordingly. Among those representations needing constant calibration is interval timing, which plays a pivotal role in various cognitive and motor tasks. To investigate how perceived time interval is adjusted by experience, we conducted a human psychophysical experiment using an implicit interval-timing task in which observers responded to an invisible bar drifting at a constant speed. We tracked daily changes in distributions of response times for a range of physical time intervals over multiple days of training with two major types of timing performance, mean accuracy and precision. We found a decoupled dynamics of mean accuracy and precision in terms of their time course and specificity of perceptual learning. Mean accuracy showed feedback-driven instantaneous calibration evidenced by a partial transfer around the time interval trained with feedback, while timing precision exhibited a long-term slow improvement with no evident specificity. We found that a Bayesian observer model, in which a subjective time interval is determined jointly by a prior and likelihood function for timing, captures the dissociative temporal dynamics of the two types of timing measures simultaneously. Finally, the model suggested that the width of the prior, not the likelihoods, gradually shrinks over sessions, substantiating the important role of prior knowledge in perceptual learning of interval timing.