Temporal processing dysfunction in schizophrenia

Schizophrenia may be associated with a fundamental disturbance in the temporal coordination of information processing in the brain, leading to classic symptoms of schizophrenia such as thought disorder and disorganized and contextually inappropriate behavior. Despite the growing interest and centrality of time-dependent conceptualizations of the pathophysiology of schizophrenia, there remains a paucity of research directly examining overt timing performance in the disorder. Accordingly, the present study investigated timing in schizophrenia using a well-established task of time perception. Twenty-three individuals with schizophrenia and 22 non-psychiatric control participants completed a temporal bisection task, which required participants to make temporal judgments about auditory and visually presented durations ranging from 300 to 600 ms. Both schizophrenia and control groups displayed greater visual compared to auditory timing variability, with no difference between groups in the visual modality. However, individuals with schizophrenia exhibited less temporal precision than controls in the perception of auditory durations. These findings correlated with parameter estimates obtained from a quantitative model of time estimation, and provide evidence of a fundamental deficit in temporal auditory precision in schizophrenia.     

Bilateral disadvantage: lack of interhemispheric cooperation in schizophrenia

Language anomalies and left-hemisphere dysfunction are commonly reported in schizophrenia. Additional evidence also suggests differences in the integration of information between the hemispheres. Bilateral gain is the increase in accuracy and decrease in latency that occurs when identical information is presented simultaneously to both hemispheres. This study measured bilateral gain in controls (n=20) and individuals with schizophrenia (n=10) using a lexical-decision task where word or non-word judgements were made to letter strings presented in the left visual field (LVF), right visual field (RVF) or bilaterally (BVF). Language was not abnormally lateralized in the schizophrenia group. Controls exhibited the expected decrease in latency when words were presented bilaterally. This effect was not observed in the schizophrenia group who were actually disadvantaged in this condition. The lack of bilateral gain in schizophrenia is discussed as arising from differences in the connections between areas in each hemisphere that mediate language.     

The temporal sensitivity to the tactile-induced double flash illusion mediates the impact of beta oscillations on schizotypal personality traits

The coherent experience of the self and the world depends on the ability to integrate vs. segregate sensory information. Optimal temporal integration between the senses is mediated by oscillatory properties of neural activity. Previous research showed reduced temporal sensitivity to multisensory events in schizotypy, a personality trait linked to schizophrenia. Here we used the tactile-induced Double-Flash-Illusion (tDFI) to investigate the tactile-to-visual temporal sensitivity in schizotypy, as indexed by the temporal window of illusion (TWI) and its neural underpinnings. We measured EEG oscillations within the beta band, recently shown to correlate with the tDFI. We found individuals with higher schizotypal traits to have wider TWI and slower beta waves accounting for the temporal window within which they perceive the illusion. Our results indicate reduced tactile-to-visual temporal sensitivity to mediate the effect of slowed oscillatory beta activity on schizotypal personality traits. We conclude that slowed oscillatory patterns might constitute an early marker for psychosis proneness.     

More consistent,yet less sensitive: Interval timing in autism spectrum disorders

Even though phenomenological observations and anecdotal reports suggest atypical time processing in individuals with an autism spectrum disorder (ASD), very few psychophysical studies have investigated interval timing, and the obtained results are contradictory. The present study aimed to clarify which timing processes function atypically in ASD and whether they are related to the ASD diagnostic profile. Visual, auditory, and cross-modal interval timing was assessed in 18 individuals with ASD using a repeated standards version of the temporal generalization task. The use of two different standard durations (600 and 1,000 ms) allowed for an assessment of the scalar property of interval timing in ASD, a fundamental characteristic of interval timing. The ASD group showed clearer adherence to the scalar property of interval timing than the control group. In addition, both groups showed the normal effect that auditory stimuli had longer subjective durations than visual ones. Yet, signal detection analysis showed that the sensitivity of temporal discrimination was reduced in the ASD group across modalities, in particular for auditory standards. Moreover, response criteria in the ASD group were related to symptom strength in the communication domain. The findings suggest that temporal intervals are fundamentally processed in the same way in ASD and TD, but with reduced sensitivity for temporal interval differences in ASD. Individuals with ASD may show a more conservative response strategy due to generally decreased sensitivity for the perception of time intervals.     

Asymmetries in visuomotor recalibration of time perception: Does causal binding distort the window of integration?

The recalibration of perceived visuomotor simultaneity to vision-lead and movement-lead temporal discrepancies is marked by an underlying causal asymmetry, if the movement (button press) is voluntary and self-initiated; a visual stimulus lagging the button press may be interpreted as causally linked sensory feedback (intentional or causal binding), a leading visual stimulus not. Here, we test whether this underlying causal asymmetry leads to directional asymmetries in the temporal recalibration of visuomotor time perception, using an interval estimation paradigm. Participants were trained to the presence of one of three temporal discrepancies between a motor action (button press) and a visual stimulus (flashed disk): 100 ms vision-lead, simultaneity, and 100 ms movement-lead. By adjusting a point on a visual scale, participants then estimated the interval between the visual stimulus and the button press over a range of discrepancies. Comparing the results across conditions, we found that temporal recalibration appears to be implemented nearly exclusively on the movement-lead side of the range of discrepancies by a uni-lateral lengthening or shortening of the window of temporal integration. Interestingly, this marked asymmetry does not lead to a significantly asymmetrical recalibration of the point of subjective simultaneity or to significant differences in discriminability. This seeming contradiction (symmetrical recalibration of subjective simultaneity and asymmetrical recalibration of interval estimation) poses a challenge to common models of temporal order perception that assume an underlying time measurement process with Gaussian noise. Using a two-criterion model of the window of temporal integration, we illustrate that a compressive bias around perceived simultaneity (temporal integration) even prior to perceptual decisions about temporal order would be very hard to detect given the sensitivity of the psychophysical procedures commonly used.     

Timing dysfunctions in schizophrenia as measured by a repetitive finger tapping task

Schizophrenia may be associated with a fundamental disturbance in the temporal coordination of information processing in the brain, leading to classic symptoms of schizophrenia such as thought disorder and disorganized and contextually inappropriate behavior. Although a variety of behavioral studies have provided strong evidence for perceptual timing deficits in schizophrenia, no study to date has directly examined overt temporal performance in schizophrenia using a task that differentially engages perceptual and motor-based timing processes. The present study aimed to isolate perceptual and motor-based temporal performance in individuals diagnosed with schizophrenia using a repetitive finger-tapping task that has previously been shown to differentially engage brain regions associated with perceptual and motor-related timing behavior. Thirty-two individuals with schizophrenia and 31 non-psychiatric control participants completed the repetitive finger-tapping task, which required participants to first tap in time with computer-generated tones separated by a fixed intertone interval (tone-paced tapping), after which the tones were discontinued and participants were required to continue tapping at the established pace (self-paced tapping). Participants with schizophrenia displayed significantly faster tapping rates for both tone- and self-paced portions of the task compared to the non-psychiatric group. Individuals diagnosed with schizophrenia also displayed greater tapping variability during both tone- and self-paced portions of the task. The application of a mathematical timing model further indicated that group differences were primarily attributable to increased timing – as opposed to task implementation – difficulties in the schizophrenia group, which is noteworthy given the broad range of impairments typically associated with the disorder. These findings support the contention that schizophrenia is associated with a broad range of timing difficulties, including those associated with time perception as well as time production.     

Timing dysfunctions in schizophrenia as measured by a repetitive finger tapping task

Schizophrenia may be associated with a fundamental disturbance in the temporal coordination of information processing in the brain, leading to classic symptoms of schizophrenia such as thought disorder and disorganized and contextually inappropriate behavior. Although a variety of behavioral studies have provided strong evidence for perceptual timing deficits in schizophrenia, no study to date has directly examined overt temporal performance in schizophrenia using a task that differentially engages perceptual and motor-based timing processes. The present study aimed to isolate perceptual and motor-based temporal performance in individuals diagnosed with schizophrenia using a repetitive finger-tapping task that has previously been shown to differentially engage brain regions associated with perceptual and motor-related timing behavior. Thirty-two individuals with schizophrenia and 31 non-psychiatric control participants completed the repetitive finger-tapping task, which required participants to first tap in time with computer-generated tones separated by a fixed intertone interval (tone-paced tapping), after which the tones were discontinued and participants were required to continue tapping at the established pace (self-paced tapping). Participants with schizophrenia displayed significantly faster tapping rates for both tone- and self-paced portions of the task compared to the non-psychiatric group. Individuals diagnosed with schizophrenia also displayed greater tapping variability during both tone- and self-paced portions of the task. The application of a mathematical timing model further indicated that group differences were primarily attributable to increased timing – as opposed to task implementation – difficulties in the schizophrenia group, which is noteworthy given the broad range of impairments typically associated with the disorder. These findings support the contention that schizophrenia is associated with a broad range of timing difficulties, including those associated with time perception as well as time production.     

Schizotypal traits are not related to multisensory integration or audiovisual speech perception

Multisensory integration, the binding of sensory information from different sensory modalities, may contribute to perceptual symptomatology in schizophrenia, including hallucinations and aberrant speech perception. Differences in multisensory integration and temporal processing, an important component of multisensory integration, are consistently found in schizophrenia. Evidence is emerging that these differences extend across the schizophrenia spectrum, including individuals in the general population with higher schizotypal traits. In the current study, we investigated the relationship between schizotypal traits and perceptual functioning, using audiovisual speech-in-noise, McGurk, and ternary synchrony judgment tasks. We measured schizotypal traits using the Schizotypal Personality Questionnaire (SPQ), hypothesizing that higher scores on Unusual Perceptual Experiences and Odd Speech subscales would be associated with decreased multisensory integration, increased susceptibility to distracting auditory speech, and less precise temporal processing. Surprisingly, these measures were not associated with the predicted subscales, suggesting that these perceptual differences may not be present across the schizophrenia spectrum.     

Sustained attention in children at risk for schizophrenia: Findings with two visual continuous performance tests in a new sample

In partial replication of an earlier study, 35 children at high risk for schizophrenia, 25 children at high risk for affective disorder, and 53 normal control children from a new sample of 7- to 12-year-old subjects were tested with two new visual continuous performance tests. Response levels and intrasubject variability were analyzed separately. Multivariate analyses on factor scores derived from response levels indicate that "groups" is a significant predictor for a factor reflecting discriminability (or sensitivity) for the more difficult of these tests but not for the less difficult one, and that high risk for schizophrenia is associated with lower performance. Factor scores and multiple regression analyses were used to dichotomize subjects as to whether or not they are low performance outliers. A significantly larger proportion of subjects from the high risk for schizophrenia group than from the control groups were low performance outliers. Among subjects that developed psychopathology in adolescence, subjects at high risk for schizophrenia were more likely to have contributed low performance outliers early during childhood.     

Temporal integration and contrast sensitivity in foveal and peripheral vision

Spatial contrast sensitivity functions and temporal integration functions for gratings with dark surrounds were measured at various eccentricities in photopic vision. Contrast sensitivity decreased with increasing eccentricity at all exposure durations and spatial frequencies tested. The decrease was faster at high than at low spatial frequencies, but similar at different exposure durations. When cortically similar stimulus conditions were produced at different eccentricities by M-scaling, contrast sensitivity became independent of visual field location at all exposure durations tested. The results support the view that in photopic vision spatiotemporal information processing is qualitatively similar across the visual field, and that quantitative differences result from retino-topical differences in ganglion cell sampling. For gratings of constant retinal area temporal integration (improvement of contrast sensitivity with increasing exposure duration) was more extensive at high than at low retinal spatial frequencies but independent of cortical spatial frequency and eccentricity. For M-scaled gratings temporal integration was more extensive at high than at low cortical spatial frequencies but independent of retinal spatial frequency and eccentricity. The results suggest that the primary determinant of temporal integration is not spatial frequency but grating value that is calculated as AF2 square cycles (cycle2), where A is grating area and F spatial frequency.     

发展性阅读障碍的视听时间敏感性缺陷及其脑神经机制

阅读是一个视听加工过程,阅读障碍的产生可能是过程中视听时间敏感性缺陷的结果。视听时间敏感性指个体对视觉和听觉刺激出现时间的感知能力,可通过同时性判断、时间顺序判断和视听整合考察。研究发现,阅读障碍者在这一能力上表现出行为和脑层面异常。而这些研究多是拼音文字背景,汉语文字下该领域研究相当少。未来需要丰富实验设计,扩大对汉语背景下视听时间敏感性研究,并以此开发干预手段,为阅读障碍的机制和治疗提供借鉴。     

Weighting and reweighting of visual input via head mounted display given unilateral peripheral vestibular dysfunction

We translated a well-established laboratory paradigm to study sensory integration into a Head-Mounted-Display (HMD). In the current study, a group of 23 individuals with unilateral vestibular dysfunction and 16 age-matched controls observed moving spheres projected from the Oculus Rift. We confirmed increased visual weighting with an unstable surface and decreased visual weighting (i.e., reweighting) with increased visual amplitude. We did not observe significant differences in gains and phases between individuals with vestibular dysfunction and age-matched controls. The vestibular group increased sway in mid and high frequencies significantly more than controls with the change in surface or visual amplitude. Mild visual perturbations within HMDs carry the potential to become a useful portable assessment of postural control in individuals with vestibular disorders.     

Temporal integration and segregation of brief visual stimuli: Patterns of correlation in time

Two brief sequential displays separated by a brief interstimulus interval (ISI) are often perceived as a temporally integrated unitary configuration. The probability of temporal integration can be decreased by increasing the ISI or (counterintuitively) by increasing stimulus duration. We tested three hypotheses of the relative contributions of stimulus duration and ISI to the breakdown of temporal integration (the storage, processing, and temporal correlation hypotheses). In the first of two experiments, stimulus duration and ISI were varied factorially, and estimates of temporal integration were obtained with a form-part integration task. The second experiment was a replication of the first at two levels of stimulus intensity. The outcomes were inconsistent with the storage and processing options, but confirmed predictions from the temporal correlation hypothesis. Whether two sequential stimuli are perceived as temporally integrated or disjoint depends not on the availability of visible persistence, but on the emergence of a neural code that is based on the temporal correlation between the two visual responses.     

Neural correlates of deficient response inhibition in mentally disordered violent individuals

In this study, response inhibition and associated neural activation during a motor inhibition paradigm were investigated in (i) men with antisocial personality disorder (APD) with a history of violence (n = 14), (ii) men with schizophrenia with a history of violence (n = 12), (iii) men with schizophrenia without a history of violence (n = 12), and (iv) healthy control subjects (n = 14) using functional magnetic resonance imaging (fMRI). At the behavioural level, individuals with schizophrenia showed impaired performance across all conditions, whereas an increased error rate was seen in the APD group only during the conditions requiring inhibition. At the neural level, both violent groups showed reduced thalamic activity, compared with controls, in association with modulation of inhibition by task demands. In addition, the violent schizophrenia group, compared with controls, showed reduced activity in the caudate nucleus during the condition requiring inhibition. It is concluded that violence may not be specifically associated with impaired voluntary inhibition in schizophrenia but this is likely in APD. Reduced thalamic function, perhaps due to its known association with sensorimotor disturbances, is implicated in violent behaviour across both disorders. In addition, caudate dysfunction may contribute, given its role in timing and temporal processing as well as suppression of motor actions, to deficient inhibition and violent behaviour in schizophrenia.     

Aging and perception of visual form from temporal structure

In this study, the authors examined age-related changes in participants' ability to perceive global spatial structure defined by temporal fine structure among elements undergoing rapid, irregular change. Participants were also tested on a task involving form recognition from luminance contrast and on a task dependent on perception of 3-dimensional shape from motion. Compared with young adults, older individuals were less sensitive to spatial form defined by temporal structure. In contrast, older observers performed as well as young adults on the other two tasks that were not dependent on temporal sensitivity, ruling out nonsensory factors as the cause of the deficits on the temporal structure task. This selective deficit may reveal reduced sensitivity within the temporal impulse response of the aging visual system, a deficit that could be related to reduced effectiveness of neural inhibition.     

Tactile—visual temporal ventriloquism: No effect of spatial disparity

Participants made visual temporal order judgments (TOJs) about which of two lights appeared first while taskirrelevant vibrotactile stimuli delivered to the index finger were presented before the first and after the second light. Temporally misaligned tactile stimuli captured the onsets of the lights, thereby improving sensitivity on the visual TOJ task, indicative of tactile-visual (TV) temporal ventriloquism (Experiment 1). The size of this effect was comparable to auditory-visual (AV) temporal ventriloquism (Experiment 2). Spatial discordance between the TV stimuli, as in the AV case, did not harm the effect (Experiments 3 and 4). TV stimuli thus behaved like AV stimuli, demonstrating that spatial co-occurrence is not a necessary constraint for intersensory pairing to occur.     

Effects of interval duration on temporal processing in schizophrenia

INTRODUCTION: Temporal processing has received scant attention in the literature pertaining to cognitive deficits in patients with schizophrenia. Previous research suggests that patients with schizophrenia exhibit temporal perception deficits on both auditory and visual stimuli. The current study investigated the effects of interval manipulation to (1) replicate the original findings with a larger sample and an increased number of trials (2) assess the degree to which both patients and controls can differentiate temporal changes in a range of experimental interstimulus intervals, and (3) explore whether different interstimulus interval durations pose different levels of difficulty for the patients with schizophrenia. METHODS: Participants were asked to decide whether temporal intervals were shorter or longer than standard intervals on a computer-based auditory temporal perception task. The standard interval remained the same duration throughout the various tasks. The interstimulus interval separating the standard and experimental intervals varied in the range of 500, 1000, or 3000 ms. Data are presented for a sample of 16 patients with schizophrenia and 15 controls. RESULTS: Data suggest that patients with schizophrenia exhibit deficits in differentiating interval durations across all paradigms compared to their control-group peers on a range of auditory tasks (p<.001). CONCLUSIONS: These results are consistent with a general temporal deficit in schizophrenia. However, the roles of medication and localization are also addressed.     

Tactile--visual temporal ventriloquism: no effect of spatial disparity

Participants made visual temporal order judgments (TOJs) about which of two lights appeared first while task-irrelevant vibrotactile stimuli delivered to the index finger were presented before the first and after the second light. Temporally misaligned tactile stimuli captured the onsets of the lights, thereby improving sensitivity on the visual TOJ task, indicative of tactile-visual (TV) temporal ventriloquism (Experiment 1). The size of this effect was comparable to auditory-visual (AV) temporal ventriloquism (Experiment 2). Spatial discordance between the TV stimuli, as in the AV case, did not harm the effect (Experiments 3 and 4). TV stimuli thus behaved like AV stimuli, demonstrating that spatial co-occurrence is not a necessary constraint for intersensory pairing to occur.     

Temporal processing and psychosis proneness

Two measures of temporal processing: critical stimulus duration (CSD) and visual backward masking (VBM), were examined in a group of normal subjects whose predisposition to psychosis was assessed using the psychoticism (P) scale from Eysenck's Personality Questionnaire. The current study employed the method of constant stimuli with a two-alternative forced choice responding to reduce the variability in CSD-data. Higher P scorers required a significant longer target stimulus duration in order to correctly identify the stimulus than lower P scorers. These results suggest that subjects prone to psychosis possess a relatively less sensitive temporal processing system than low P scorers. Performance in the subsequent masking phase revealed no evidence of a VBM deficit. It was not possible to explain this pattern of results in terms of task difficulty. The findings were discussed in terms of potential inadequacies in previous calculations of CSD. This possibility requires further testing before the backward masking deficit can be adopted as a trait marker for schizophrenia.     

Temporal structure coding with and without awareness

In order to interpret a constantly changing environment, visual events far apart in space and time must be integrated into a unified percept. While spatial properties of invisible signals are known to be encoded without awareness, the fate of temporal properties remains largely unknown. Here, we probed temporal integration for two distinct motion stimuli that were either visible or rendered invisible using continuous flash suppression. We found that when invisible, both the direction of apparent motion and the gender of point-light walkers were processed only when defined across short time periods (i.e., respectively 100 ms and 1000 ms). This limitation was not observed under full visibility. These similar findings at two different hierarchical levels of processing suggest that temporal integration windows shrink in the absence of perceptual awareness. We discuss this phenomenon as a key prediction of the global neuronal workspace and the information integration theories of consciousness.