Tone duration discrimination in Parkinson's disease

Rhythm and groove as cognitive mechanisms of dance intervention in Parkinson's disease

Parkinson's disease (PD) is associated with a loss of internal cueing systems, affecting rhythmic motor tasks such as walking and speech production. Music and dance encourage spontaneous rhythmic coupling between sensory and motor systems; this has inspired the development of dance programs for PD. Here we assessed the therapeutic outcome and some underlying cognitive mechanisms of dance classes for PD, as measured by neuropsychological assessments of disease severity as well as quantitative assessments of rhythmic ability and sensorimotor experience. We assessed prior music and dance experience, beat perception (Beat Alignment Test), sensorimotor coupling (tapping to high- and low-groove songs), and disease severity (Unified Parkinson's Disease Rating Scale in PD individuals) before and after four months of weekly dance classes. PD individuals performed better on UPDRS after four months of weekly dance classes, suggesting efficacy of dance intervention. Greater post-intervention improvements in UPDRS were associated with the presence of prior dance experience and with more accurate sensorimotor coupling. Prior dance experience was additionally associated with enhanced sensorimotor coupling during tapping to both high-groove and low-groove songs. These results show that dance classes for PD improve both qualitative and quantitative assessments of disease symptoms. The association between these improvements and dance experience suggests that rhythmic motor training, a mechanism underlying dance training, impacts improvements in parkinsonian symptoms following a dance intervention.

Evaluation of multi-feature auditory deviance detection in Parkinson's disease: a mismatch negativity study

Behavioral studies on auditory deviance detection in patients with Parkinson's disease (PD) have reported contradictory results. The primary aim of this study was to investigate auditory deviance detection of multiple auditory features in patients with PD by means of objective and reliable electroencephalographic (EEG) measurements. Twelve patients with early-stage PD and twelve age- and gender-matched healthy controls (HCs) were included in this study. Patients with PD participated without their regular dopaminergic medication. All subjects underwent an audiometric screening and performed a passive multi-feature mismatch negativity (MMN) paradigm. Repeated-measures analysis of variance (ANOVA) demonstrated no significant differences between patients with PD and HCs regarding MMN mean amplitude and latency for frequency, duration and gap deviants. Nevertheless, a trend towards increased MMN mean amplitude and latency was found in response to intensity deviants in patients with PD compared to HCs. Increased intensity MMN amplitude may indicate that more neural resources are allocated to the processing of intensity deviances in patients with PD compared to HCs. The interpretation of this intensity-specific MMN alteration is further discussed in the context of a compensatory mechanism for auditory intensity processing and involuntary attention switching in PD.

Time Distortion in Parkinsonism

Although animal studies and studies on Parkinson’s disease (PD) suggest that dopamine deficiency slows the pace of the internal clock, which is corrected by dopaminergic medication, timing deficits in parkinsonism remain to be characterized with diverse findings. Here we studied patients with PD and progressive supranuclear palsy (PSP), 3–4 h after drug intake, and normal age-matched subjects. We contrasted perceptual (temporal bisection, duration comparison) and motor timing tasks (time production/reproduction) in supra- and sub-second time domains, and automatic versus cognitive/short-term memory–related tasks. Subjects were allowed to count during supra-second production and reproduction tasks. In the time production task, linearly correlating the produced time with the instructed time showed that the “subjective sense” of 1 s is slightly longer in PD and shorter in PSP than in normals. This was superposed on a prominent trend of underestimation of longer (supra-second) durations, common to all groups, suggesting that the pace of the internal clock changed from fast to slow as time went by. In the time reproduction task, PD and, more prominently, PSP patients over-reproduced shorter durations and under-reproduced longer durations at extremes of the time range studied, with intermediate durations reproduced veridically, with a shallower slope of linear correlation between the presented and produced time. In the duration comparison task, PD patients overestimated the second presented duration relative to the first with shorter but not longer standard durations. In the bisection task, PD and PSP patients estimated the bisection point (BP50) between the two supra-second but not sub-second standards to be longer than normal subjects. Thus, perceptual timing tasks showed changes in opposite directions to motor timing tasks: underestimating shorter durations and overestimating longer durations. In PD, correlation of the mini-mental state examination score with supra-second BP50 and the slope of linear correlation in the reproduction task suggested involvement of short-term memory in these tasks. Dopamine deficiency didn’t correlate significantly with timing performances, suggesting that the slowed clock hypothesis cannot explain the entire results. Timing performance in PD may be determined by complex interactions among time scales on the motor and sensory sides, and by their distortion in memory.

Future Perspectives on the Relevance of Auditory Markers in Prodromal Parkinson's Disease

Research on auditory processing in Parkinson's disease (PD) has recently made substantial progress. At present, evidence has been found for altered auditory processing in the clinical stage of PD. The auditory alterations in PD have been demonstrated with low-cost and non-invasive assessments that are already used in routine clinical practice. Since auditory alterations have been reported early in disease progression, it would be highly relevant to investigate whether auditory markers could be provided in the prodromal stage of PD. In addition, auditory alterations in early stage PD might be modulated by dopaminergic medication. Therefore, the aim of this review is (1) to summarize the literature on auditory processing in PD with a specific focus on the early disease stages, (2) to give future perspectives on which audiological and electrophysiological measurements could be useful in the prodromal stage of PD and (3) to assess the effect of dopaminergic medication on potential auditory markers in the prodromal stage of PD.

Central auditory processing in parkinsonian disorders: A systematic review

Altered auditory processing has been increasingly recognized as a non-motor feature in parkinsonian disorders. This systematic review provides an overview of behavioral and electrophysiological literature on central auditory processing in patients with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). A systematic database search was conducted and yielded 88 studies that met the intelligibility criteria. The collected data revealed distinct impairments in a range of central auditory processes in PD, including altered deviance detection of basic auditory features, auditory brainstem processing, auditory gating and selective auditory attention. In contrast to PD, literature on central auditory processing in atypical parkinsonian disorders was relatively scarce, but provided some evidence for impaired central auditory processing in MSA and PSP. The interpretation of these findings is discussed and suggestions for further research are offered.

Contributions of the Basal Ganglia to Temporal Processing: Evidence from Parkinson’s Disease

The motor and perceptual timing deficits documented in patients with Parkinson’s disease (PD) have heavily influenced the theory that the basal ganglia play an important role in temporal processing. This review is a systematic exploration of the findings from behavioural and neuroimaging studies of motor and perceptual timing in PD. In particular, we consider the influence of a variety of task factors and of patient heterogeneity in explaining the mixed results. We also consider the effect of basal ganglia dysfunction on the non-temporal cognitive factors that contribute to successful motor and perceptual timing. Although there is convincing evidence from PD that the basal ganglia are critical to motor and perceptual timing, further work is needed to characterize the precise contribution of this complex structure to temporal processing.

Motor and perceptual timing in Parkinson's disease

Neuroimaging has been a powerful tool for understanding the neural architecture of interval timing. However, identifying the critical brain regions engaged in timing was initially driven by investigation of human patients and animals. This chapter draws on the important contribution that the study of patients with Parkinson's disease (PD) has made in identifying the basal ganglia as a key component of motor and perceptual timing. The chapter initially describes the experimental tasks that have been critical in PD (and non-PD) timing research before systematically discussing the results from behavioural studies. This is followed by a critique of neuroimaging studies that have given insight into the pattern of neural activity during motor and perceptual timing in PD. Finally, discussion of the effects of medical and surgical treatment on timing in PD enables further evaluation of the role of dopamine in interval timing.

Functional neuroimaging of duration discrimination on two different time scales

Analyses of neural mechanisms of duration processing are essential for the understanding of psychological phenomena which evolve in time. Different mechanisms are presumably responsible for the processing of shorter (below 500 ms) and longer (above 500 ms) events but have not yet been a subject of an investigation with functional magnetic resonance imaging (fMRI). In the present study, we show a greater involvement of several brain regions - including right-hemispheric midline structures and left-hemispheric lateral regions - in the processing of visual stimuli of shorter as compared to longer duration. We propose a greater involvement of lower-level cognitive mechanisms in the processing of shorter events as opposed to higher-level mechanisms of cognitive control involved in longer events.

The inner experience of time

The striking diversity of psychological and neurophysiological models of 'time perception' characterizes the debate on how and where in the brain time is processed. In this review, the most prominent models of time perception will be critically discussed. Some of the variation across the proposed models will be explained, namely (i) different processes and regions of the brain are involved depending on the length of the processed time interval, and (ii) different cognitive processes may be involved that are not necessarily part of a core timekeeping system but, nevertheless, influence the experience of time. These cognitive processes are distributed over the brain and are difficult to discern from timing mechanisms. Recent developments in the research on emotional influences on time perception, which succeed decades of studies on the cognition of temporal processing, will be highlighted. Empirical findings on the relationship between affect and time, together with recent conceptualizations of self- and body processes, are integrated by viewing time perception as entailing emotional and interoceptive (within the body) states. To date, specific neurophysiological mechanisms that would account for the representation of human time have not been identified. It will be argued that neural processes in the insular cortex that are related to body signals and feeling states might constitute such a neurophysiological mechanism for the encoding of duration.

Auditory temporal processing in Parkinson's disease

Previous research has suggested that Parkinson's disease (PD) impairs perceptual acuity in the temporal domain. In the present study, psychophysical tests assessing several aspects of auditory temporal processing were administered to a group of PD patients treated with bilateral subthalamic nucleus (STN) stimulation and to a normal control group. Each patient was tested in three clinical conditions: without treatment, with levodopa therapy, and during STN stimulation. In all three conditions, the patients showed a significant deficit in the detection of very short temporal gaps within noise bursts and in the discrimination between the durations of two well-detectable time intervals (circa 50ms) bounded by two temporally non-contiguous pairs of clicks. However, the patients showed no deficit in the detection of a temporal break produced by a local interval change in an otherwise isochronous sequence of 10 clicks spaced by 50-ms intervals. The latter result contradicts previous suggestions that PD slows down an internal clock or pacemaker involved in the perception of short durations. In this regard, we reinterpret previous evidence. Remarkably, the patients' deficits were not diminished by levodopa therapy; in contrast, STN stimulation slightly improved performance, overall. We tentatively ascribe the deficit observed in the gap-detection test to a dysfunctioning of the auditory cortex, impairing its ability to track rapid fluctuations in sound intensity. We argue that the deficit in the duration-discrimination test is the consequence of an impairment in memory and/or attention rather than in the perception of time per se.

Impaired time perception and motor timing in stimulant-dependent subjects

Stimulant-dependent individuals (SDI) have abnormal brain metabolism and structural changes involving dopaminergic target areas important for the processing of time. These individuals are also more impulsive and impaired in working memory and attention. The current study tested whether SDI show altered temporal processing in relation to impulsivity or impaired prefrontal cortex functioning. We employed a series of timing tasks aimed to examine time processing from the milliseconds to multiple seconds range and assessed cognitive function in 15 male SDI and 15 stimulant-naïve individuals. A mediation analysis determined the degree to which impulsivity or executive dysfunctions contributed to group differences in time processing. SDI showed several abnormal time processing characteristics. SDI needed larger time differences for effective duration discrimination, particularly for intervals of around 1s. SDI also accelerated finger tapping during a continuation period after a 1Hz pacing stimulus was removed. In addition, SDI overestimated the duration of a relatively long time interval, an effect which was attributable to higher impulsivity. Taken together, these data show for the first time that SDI exhibit altered time processing in several domains, one which can be explained by increased impulsivity. Altered time processing in SDI could explain why SDI have difficulty delaying gratification.

The effect of Parkinson’s disease on time estimation as a function of stimulus duration range and modality

The present research sought to investigate the role of the basal ganglia in timing of sub- and supra-second intervals via an examination of the ability of people with Parkinson's disease (PD) to make temporal judgments in two ranges, 100-500 ms, and 1-5 s. Eighteen non-demented medicated patients with PD were compared with 14 matched controls on a duration-bisection task in which participants were required to discriminate auditory and visual signal durations within each time range. Results showed that patients with PD exhibited more variable duration judgments across both signal modality and duration range than controls, although closer analyses confirmed a timing deficit in the longer duration range only. The findings presented here suggest the bisection procedure may be a useful tool in identifying timing impairments in PD and, more generally, reaffirm the hypothesised role of the basal ganglia in temporal perception at the level of the attentionally mediated internal clock as well as memory retrieval and/or decision-making processes.

Effects of psilocybin on time perception and temporal control of behaviour in humans

Hallucinogenic psilocybin is known to alter the subjective experience of time. However, there is no study that systematically investigated objective measures of time perception under psilocybin. Therefore, we studied dose-dependent effects of the serotonin (5-HT)2A/1A receptor agonist psilocybin (4-phosphoryloxy-N, N-dimethyltryptamine) on temporal processing, employing tasks of temporal reproduction, sensorimotor synchronization and tapping tempo. To control for cognitive and subjective changes, we assessed spatial working memory and conscious experience. Twelve healthy human volunteers were tested under placebo, medium (115 microg/kg), and high (250 microg/kg) dose conditions, in a double-blind experimental design. Psilocybin was found to significantly impair subjects' ability to (1) reproduce interval durations longer than 2.5 sec, (2) to synchronize to inter-beat intervals longer than 2 sec and (3) caused subjects to be slower in their preferred tapping rate. These objective effects on timing performance were accompanied by working-memory deficits and subjective changes in conscious state, namely increased reports of 'depersonalization' and 'derealization' phenomena including disturbances in subjective 'time sense.' Our study is the first to systematically assess the impact of psilocybin on timing performance on standardized measures of temporal processing. Results indicate that the serotonin system is selectively involved in duration processing of intervals longer than 2 to 3 seconds and in the voluntary control of the speed of movement. We speculate that psilocybin's selective disruption of longer intervals is likely to be a product of interactions with cognitive dimensions of temporal processing -presumably via 5-HT2A receptor stimulation.

Interval bisection in spontaneously hypertensive rats

An interval bisection procedure was used to study time discrimination in spontaneously hypertensive rats (SHR), which have been proposed as an animal model for the attention deficit hyperactivity disorder (ADHD); Wistar Kyoto and Wistar rats were used as comparison groups. In this procedure, after subjects learn to make one response (S) following a short duration stimulus, and another (L) following a long duration stimulus, stimuli of intermediate durations are presented, and the percentage of L is calculated for each duration. A logistic function is fitted to these data, and different parameters that describe the time discrimination process are obtained. Four conditions, with different short and long durations (1-4, 2-8, 3-12, 4-16s) were used. The results indicate that time discrimination is not altered in SHR, given that no difference in any of the parameters obtained were significant. Given that temporal processing has been proposed as a fundamental factor in the development of the main symptoms of ADHD, and that deficits in time discrimination have been found in individuals with that disorder, the present results suggest the necessity of exploring time perception in SHR with other procedures and sensory modalities, in order to assess its validity as an animal model of ADHD.

Efficiency of temporal order discrimination as an indicator of bradyphrenia in Parkinson's disease: the inspection time loop task

To investigate the bradyphrenia hypothesis of Parkinson's disease (PD), 32 patients undertook an information-processing task which measured their efficiency of temporal order discrimination. Their performance was compared with 31 non-PD controls matched on age, sex, years of full-time education and pre-morbid IQ. The task was novel and designed to be sensitive to the clinical phenomenon of bradyphrenia (slowing of mental abilities), in the context of temporal order discrimination without confounding from motor ability deficits. The test (the inspection time loop task; ITloop) required judgements as to the temporal sequence of four single letters. The stimulus duration of the letters in each sequence ranged from 100 to 700ms. The PD group had a significantly lower mean score on the ITloop task than did controls (P=0.02). PD patients perform more poorly on temporal order discrimination judgements even when the task makes no motor demands.

Discrimination of tone durations across the menstrual cycle

Discrimination of tone duration was studied as a function of menstrual cycle phase. In three phases of their menstrual cycle, 12 women compared the durations of 64 pairs of tones. They discriminated the tone durations least well in the premenstrual phase and tended to speed up their responding over sessions. In contrast, a control group of 12 men tended to improve their performance over sessions while response time remained constant.

Interval timing performance in temporal lobe epilepsy: differences between patients with left and right hemisphere foci

This experiment examined interval timing performance on a temporal reproduction procedure and a temporal discrimination (interval bisection) procedure in 19 patients with temporal lobe epilepsy (ten with a left-hemisphere focus [LTE group] and nine with a right- hemisphere focus [RTE group]), and 14 normal control subjects. In the temporal reproduction task, subjects were required to reproduce the durations of visual stimuli (0.5, 1, 2, 4, 8 s). In the temporal discrimination task, subjects were required to classify the visual stimuli as either 'short' or 'long'. Following exposure to the two standard durations (1 and 2 s), 'probe' trials were introduced in which the stimulus was presented for durations intermediate between the two standard durations. Psychophysical functions were derived from both timing tasks for each individual subject, as well as for the group mean data. The results showed that, compared to the normal subjects, the RTE group's timing ability was significantly compromized, as reflected by larger Weber fractions in both timing tasks. The LTE group's Weber fractions did not differ significantly from those of the control group; however they showed a leftward shift (i.e. a shorter bisection point) of the psychophysical function under the temporal discrimination task. The results suggest that the right and left hemispheres may play different roles in regulating interval timing performance.