Interval Discrimination Task Research Articles

Pre-supplementary Motor Cortex Mediates Learning Transfer from Perceptual to Motor Timing.

When we intensively train a timing skill, such as learning to play the piano, we not only produce brain changes associated with task-specific learning but also improve our performance in other temporal behaviors that depend on these tuned neural resources. Since the neural basis of time learning and generalization is still unknown, we measured the changes in neural activity associated with the transfer of learning from perceptual to motor timing in a large sample of subjects (n = 65; 39 women). We found that intense training in an interval discrimination task increased the acuity of time perception in a group of subjects that also exhibited learning transfer, expressed as a reduction in inter-tap interval variability during an internally driven periodic motor task. In addition, we found subjects with no learning and/or generalization effects. Notably, functional imaging showed an increase in pre-supplementary motor area and caudate-putamen activity between the post- and pre-training sessions of the tapping task. This increase was specific to the subjects that generalized their timing acuity from the perceptual to the motor context. These results emphasize the central role of the cortico-basal ganglia circuit in the generalization of timing abilities between tasks.

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

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. 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. 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. 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. clinicaltrials.gov, identifier NCT02642029.

Relative pitch representations and invariance to timbre

Information in speech and music is often conveyed through changes in fundamental frequency (f0), perceived by humans as “relative pitch”. Relative pitch judgments are complicated by two facts. First, sounds can simultaneously vary in timbre due to filtering imposed by a vocal tract or instrument body. Second, relative pitch can be extracted in two ways: by measuring changes in constituent frequency components from one sound to another, or by estimating the f0 of each sound and comparing the estimates. We examined the effects of timbral differences on relative pitch judgments, and whether any invariance to timbre depends on whether judgments are based on constituent frequencies or their f0. Listeners performed up/down and interval discrimination tasks with pairs of spoken vowels, instrument notes, or synthetic tones, synthesized to be either harmonic or inharmonic. Inharmonic sounds lack a well-defined f0, such that relative pitch must be extracted from changes in individual frequencies. Pitch judgments were less accurate when vowels/instruments were different compared to when they were the same, and were biased by the associated timbre differences. However, this bias was similar for harmonic and inharmonic sounds, and was observed even in conditions where judgments of harmonic sounds were based on f0 representations. Relative pitch judgments are thus not invariant to timbre, even when timbral variation is naturalistic, and when such judgments are based on representations of f0.

A Recurrent Neural Network Model Accounts for Both Timing and Working Memory Components of an Interval Discrimination Task

Abstract Interval discrimination is of fundamental importance to many forms of sensory processing, including speech and music. Standard interval discrimination tasks require comparing two intervals separated in time, and thus include both working memory (WM) and timing components. Models of interval discrimination invoke separate circuits for the timing and WM components. Here we examine if, in principle, the same recurrent neural network can implement both. Using human psychophysics, we first explored the role of the WM component by varying the interstimulus delay. Consistent with previous studies, discrimination was significantly worse for a 250 ms delay, compared to 750 and 1500 ms delays, suggesting that the first interval is stably stored in WM for longer delays. We next successfully trained a recurrent neural network (RNN) on the task, demonstrating that the same network can implement both the timing and WM components. Many units in the RNN were tuned to specific intervals during the sensory epoch, and others encoded the first interval during the delay period. Overall, the encoding strategy was consistent with the notion of mixed selectivity. Units generally encoded more interval information during the sensory epoch than in the delay period, reflecting categorical encoding of short versus long in WM, rather than encoding of the specific interval. Our results demonstrate that, in contrast to standard models of interval discrimination that invoke a separate memory module, the same network can, in principle, solve the timing, WM, and comparison components of an interval discrimination task.

Ramping activity in the striatum

Control of the timing of behavior is thought to require the basal ganglia (BG) and BG pathologies impair performance in timing tasks. Temporal interval discrimination depends on the ramping activity of medium spiny neurons (MSN) in the main BG input structure, the striatum, but the underlying mechanisms driving this activity are unclear. Here, we combine an MSN dynamical network model with an action selection system applied to an interval discrimination task. We find that when network parameters are appropriate for the striatum so that slowly fluctuating marginally stable dynamics are intrinsically generated, up and down ramping populations naturally emerge which enable significantly above chance task performance. We show that emergent population activity is in very good agreement with empirical studies and discuss how MSN network dysfunction in disease may alter temporal perception.

Representation of foreseeable choice outcomes in orbitofrontal cortex triplet-wise interactions.

Shared neuronal variability has been shown to modulate cognitive processing. However, the relationship between shared variability and behavioral performance is heterogeneous and complex in frontal areas such as the orbitofrontal cortex (OFC). Mounting evidence shows that single-units in OFC encode a detailed cognitive map of task-space events, but the existence of a robust neuronal ensemble coding for the predictability of choice outcome is less established. Here, we hypothesize that the coding of foreseeable outcomes is potentially unclear from the analysis of units activity and their pairwise correlations. However, this code might be established more conclusively when higher-order neuronal interactions are mapped to the choice outcome. As a case study, we investigated the trial-to-trial shared variability of neuronal ensemble activity during a two-choice interval-discrimination task in rodent OFC, specifically designed such that a lose-switch strategy is optimal by repeating the rewarded stimulus in the upcoming trial. Results show that correlations among triplets are higher during correct choices with respect to incorrect ones, and that this is sustained during the entire trial. This effect is not observed for pairwise nor for higher than third-order correlations. This scenario is compatible with constellations of up to three interacting units assembled during trials in which the task is performed correctly. More interestingly, a state-space spanned by such constellations shows that only correct outcome states that can be successfully predicted are robust over 100 trials of the task, and thus they can be accurately decoded. However, both incorrect and unpredictable outcome representations were unstable and thus non-decodeable, due to spurious negative correlations. Our results suggest that predictability of successful outcomes, and hence the optimal behavioral strategy, can be mapped out in OFC ensemble states reliable over trials of the task, and revealed by sufficiency complex neuronal interactions.

Complete cross-frequency transfer of tone frequency learning after double training.

A person's ability to discriminate fine differences in tone frequency is vital for everyday hearing such as listening to speech and music. This ability can be improved through training (i.e., tone frequency learning). Depending on stimulus configurations and training procedures, tone frequency learning can either transfer to new frequencies, which would suggest learning of a general task structure, or show significant frequency specificity, which would suggest either changes in neural representations of trained frequencies, or reweighting of frequency-specific neural responses. Here we tested the hypothesis that frequency specificity in tone frequency learning can be abolished with a double-training procedure. Specifically, participants practiced tone frequency discrimination at 1 or 6 kHz, presumably encoded by different temporal or place coding mechanisms, respectively. The stimuli were brief tone pips known to produce significant specificity. Tone frequency learning was indeed initially highly frequency specific (Experiment 1). However, with additional exposure to the other untrained frequency via an irrelevant temporal interval discrimination task, or even background play during a visual task, learning transferred completely (1-to-6 kHz or 6-to-1 kHz; Experiments 2-4). These results support general task structure learning, or concept learning in our term, in tone frequency learning despite initial frequency specificity. They also suggest strategies to design efficient auditory training in practical settings. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Tone language experience modulates the effect of long-term musical training on musical pitch perception.

Long-term musical training is widely reported to enhance music pitch perception. However, it remains unclear whether tone language experience influences the effect of long-term musical training on musical pitch perception. The present study addressed this question by testing 30 Cantonese and 30 non-tonal language speakers, each divided equally into musician and non-musician groups, on pitch height and pitch interval discrimination. Musicians outperformed non-musicians among non-tonal language speakers, but not among Cantonese speakers on the pitch height discrimination task. However, musicians outperformed non-musicians among Cantonese speakers, but not among non-tonal language speakers on the pitch interval discrimination task. These results suggest that the effect of long-term musical training on musical pitch perception is shaped by tone language experience and varies across different pitch perception tasks.

Auditory temporal perceptual learning and transfer in Chinese-speaking children with developmental dyslexia

Perceptual learning refers to the improvement of perceptual performance as a function of training. Recent studies found that auditory perceptual learning may improve phonological skills in individuals with developmental dyslexia in alphabetic writing system. However, whether auditory perceptual learning could also benefit the reading skills of those learning the Chinese logographic writing system is, as yet, unknown. The current study aimed to investigate the remediation effect of auditory temporal perceptual learning on Mandarin-speaking school children with developmental dyslexia. Thirty children with dyslexia were screened from a large pool of students in 3th-5th grades. They completed a series of pretests and then were assigned to either a non-training control group or a training group. The training group worked on a pure tone duration discrimination task for 7 sessions over 2 weeks with thirty minutes per session. Post-tests immediately after training and a follow-up test 2 months later were conducted. Analyses revealed a significant training effect in the training group relative to non-training group, as well as near transfer to the temporal interval discrimination task and far transfer to phonological awareness, character recognition and reading fluency. Importantly, the training effect and all the transfer effects were stable at the 2-month follow-up session. Further analyses found that a significant correlation between character recognition performance and learning rate mainly existed in the slow learning phase, the consolidation stage of perceptual learning, and this effect was modulated by an individuals' executive function. These findings indicate that adaptive auditory temporal perceptual learning can lead to learning and transfer effects on reading performance, and shed further light on the potential role of basic perceptual learning in the remediation and prevention of developmental dyslexia.

Mind the gap: temporal discrimination and dystonia.

One of the most widely studied perceptual measures of sensory dysfunction in dystonia is the temporal discrimination threshold (TDT) (the shortest interval at which subjects can perceive that there are two stimuli rather than one). However the elevated thresholds described may be due to a number of potential mechanisms as current paradigms test not only temporal discrimination but also extraneous sensory and decision-making parameters. In this study two paradigms designed to better quantify temporal processing are presented and a decision-making model is used to assess the influence of decision strategy. 22 patients with cervical dystonia and 22 age-matched controls completed two tasks (i) temporal resolution (a randomized, automated version of existing TDT paradigms) and (ii) interval discrimination (rating the length of two consecutive intervals). In the temporal resolution task patients had delayed (P=0.021) and more variable (P=0.013) response times but equivalent discrimination thresholds. Modelling these effects suggested this was due to an increased perceptual decision boundary in dystonia with patients requiring greater evidence before committing to decisions (P=0.020). Patient performance on the interval discrimination task was normal. Our work suggests that previously observed abnormalities in TDT may not be due to a selective sensory deficit of temporal processing as decision-making itself is abnormal in cervical dystonia.

Timescale- and Sensory Modality-Dependency of the Central Tendency of Time Perception.

When individuals are asked to reproduce intervals of stimuli that are intermixedly presented at various times, longer intervals are often underestimated and shorter intervals overestimated. This phenomenon may be attributed to the central tendency of time perception, and suggests that our brain optimally encodes a stimulus interval based on current stimulus input and prior knowledge of the distribution of stimulus intervals. Two distinct systems are thought to be recruited in the perception of sub- and supra-second intervals. Sub-second timing is subject to local sensory processing, whereas supra-second timing depends on more centralized mechanisms. To clarify the factors that influence time perception, the present study investigated how both sensory modality and timescale affect the central tendency. In Experiment 1, participants were asked to reproduce sub- or supra-second intervals, defined by visual or auditory stimuli. In the sub-second range, the magnitude of the central tendency was significantly larger for visual intervals compared to auditory intervals, while visual and auditory intervals exhibited a correlated and comparable central tendency in the supra-second range. In Experiment 2, the ability to discriminate sub-second intervals in the reproduction task was controlled across modalities by using an interval discrimination task. Even when the ability to discriminate intervals was controlled, visual intervals exhibited a larger central tendency than auditory intervals in the sub-second range. In addition, the magnitude of the central tendency for visual and auditory sub-second intervals was significantly correlated. These results suggest that a common modality-independent mechanism is responsible for the supra-second central tendency, and that both the modality-dependent and modality-independent components of the timing system contribute to the central tendency in the sub-second range.

Reservoir of neurons with adaptive time constants: a hybrid model for robust motor-sensory temporal processing

The ability to precisely quantify time on the scale ofhundreds of milliseconds is critical towards the proces-sing of complex sensory and motor patterns. However,the natures of neural mechanisms for temporal proces-sing (at this scale) in the brain are mostly unknown.Based on experimental data (psychophysics, cell cul-tures, electrophysiology) and theoretical studies, it is lar-gely debated whetherdedicated circuits or intrinsicmechanisms of neural circuits underlie the timing pro-cess [1]. One specific type of timing model, namelystate-dependent networks (SDN) [2], shows that time isencoded in the temporal patterns of activity of neuralpopulations and emerges from the internal dynamics ofrecurrent networks. This can be achieved without theneed of dedicated timing units. However, such intrinsicmodels in their present form have difficulty accountingfor crossmodal transfer [1]. In contrast, recent experi-mental evidence indicates that medial premotor corticalneurons of behaving monkeys show specific intervaltuning across modalities (auditory and visual) [3]. In thiswork we propose a hybrid model, making the hypothesisthat dedicated interval tuning mechanisms of individualneurons augment the intrinsic dynamics of large recur-rent networks (dynamic reservoir). Using a networkmodel of rate-coded neurons starting with random initi-alization of synaptic connections, we propose a learningrule based on local active information storage (LAIS) [4]to adapt neuronal time constants with respect to theinput stimuli to the network. Measured at each spatio-temporal location of the reservoir, LAIS gives a prob-abilistic measure of the amount of information in theprevious state of the neuron that is relevant in predict-ing the next state. Interestingly high LAIS regions in thenetwork correlate to significant events in time (intervals)of the driving stimulus. Furthermore, we combine thiswith mutual information driven intrinsic plasticityscheme in order to stabilize chaotic activity in the net-work. Incoming input drives the network which, in turn,is connected to readout neurons (Figure 1.A) that dis-play the learned behavior for temporally dependent sen-sory motor tasks. Reservoir-to-output connections canbe adapted using both supervised and reward modulatedlearning rules. Using single and multiple interval discri-mination tasks, we show that our network reproduces(across modalities) a linear increase in temporal variabil-ity with increase in interval duration. This correlation isalso observed in experimental data [3]. Furthermore wedemonstrate that our dedicated timing mechanism com-plements the inherent transient dynamics of the net-work by successfully learning complex time dependentmotor behaviors; like handwriting generation (Figure 1.Band C), locomotion pattern transformation and temporalmemory tasks. In essence, our hybrid model demon-stratesthattimecanbeencodedbyacombinationofdedicated and intrinsic mechanisms with the possibilityto ‘learn’ the temporal structure of incoming stimuli [5].

Neural Basis of Working Memory for Time Intervals

The brain can hold information about multiple environmental objects in working memory. It is not known, however, whether time intervals can be treated similarly as “sensory objects” and stored in memory as distinct items. Here, we designed a new paradigm to measure the precision of memory for time intervals. Listeners were required to remember and match the duration of a probed interval from a sequence of intervals and the precision of the response was evaluated as an index of memory (Bays & Husain, 2008). Behavioural data indicated that memory for a single sub-second time interval was significantly modulated by temporal regularity and the number of intervals in the sequence (Teki & Griffiths, 2013).In this functional magnetic resonance imaging study, we specifically aimed to examine the brain areas that encode memory for time as a function of rhythmic context and memory load. Based on previous work, we hypothesized a role for both striatum and cerebellum in encoding time in a beat-based and duration-based manner respectively (Teki et al., 2011, 2012) and a role for the parietal and prefrontal cortex in encoding the memory load. Four different levels of temporal regularity (5-10%, 20-25%, 35- 40%, and 50-55% jitter) and working memory load (1-4 intervals) were used in an orthogonal design where jitter was varied across sequences with fixed number of intervals (4) and number of intervals were varied across sequences with a fixed jitter (20- 25%). Functional imaging data were acquired using a sparse sampling protocol in a 3T Siemens Trio scanner whilst participants were performing the task.Parametric analysis of data from 12 participants so far revealed activation in both striatum and cerebellum, with stronger striatal and cerebellar activity as a function of decreasing and increasing jitter respectively. Analysis of brain areas that parametrically encode increasing number of time intervals revealed significant clusters in the parietal cortex and cerebellum. Our data go beyond previous work examining memory during single interval discrimination tasks and reveal context-dependent correlates of memory for time intervals (Merchant et al., 2013) that vary as a function of the rhythmic context and the working memory load of the sequences. The data suggests a critical role for subcortical timing networks in the basal ganglia and the cerebellum in mediating rhythmic timing and the parietal cortex in representing the memory load.

The Effect of Instrumental Timbre on Interval Discrimination

We tested non-musicians and musicians in an auditory psychophysical experiment to assess the effects of timbre manipulation on pitch-interval discrimination. Both groups were asked to indicate the larger of two presented intervals, comprised of four sequentially presented pitches; the second or fourth stimulus within a trial was either a sinusoidal (or “pure”), flute, piano, or synthetic voice tone, while the remaining three stimuli were all pure tones. The interval-discrimination tasks were administered parametrically to assess performance across varying pitch distances between intervals (“interval-differences”). Irrespective of timbre, musicians displayed a steady improvement across interval-differences, while non-musicians only demonstrated enhanced interval discrimination at an interval-difference of 100 cents (one semitone in Western music). Surprisingly, the best discrimination performance across both groups was observed with pure-tone intervals, followed by intervals containing a piano tone. More specifically, we observed that: 1) timbre changes within a trial affect interval discrimination; and 2) the broad spectral characteristics of an instrumental timbre may influence perceived pitch or interval magnitude and make interval discrimination more difficult.

Variability and information content in auditory cortex spike trains during an interval-discrimination task

Processing of temporal information is key in auditory processing. In this study, we recorded single-unit activity from rat auditory cortex while they performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms and nose-poke to the left or to the right accordingly. The spike firing of single neurons in the auditory cortex was then compared in engaged vs. idle brain states. We found that spike firing variability measured with the Fano factor was markedly reduced, not only during stimulation, but also in between stimuli in engaged trials. We next explored if this decrease in variability was associated with an increased information encoding. Our information theory analysis revealed increased information content in auditory responses during engagement compared with idle states, in particular in the responses to task-relevant stimuli. Altogether, we demonstrate that task-engagement significantly modulates coding properties of auditory cortical neurons during an interval-discrimination task.

Countdown-Only Pedestrian Change Interval Displays

This study evaluated the effect of visual pedestrian signal displays on the ability of persons with reduced visual acuity to accurately and confidently identify the pedestrian interval. While watching video clips of actual intersections presented on a 42-in. monitor under simulated visual impairment, participants attempted to determine the pedestrian interval (“Walk,” flashing “Don't Walk,” or steady “Don't Walk”) and provided confidence ratings for each judgment. Participants in Experiment 1 experienced simulated acuities of 20/70, 20/100, and 20/200; participants in Experiment 2 experienced approximate acuities of 20/20, 20/50, and 20/300. The study made a critical comparison of two methods of signaling the pedestrian change interval (i.e., flashing “Don't Walk”): (a) simultaneous presentation of a countdown and a flashing upraised hand symbol and (b) a countdown-only display without the flashing upraised hand. With the exception of performance in the 20/300 vision category, participants' accuracy on the interval discrimination task was, overall, rather high. However, under simulated visual impairment of 20/70 or worse, participants' success in correctly determining the pedestrian interval was, on average, 21.5 percentage points lower for the countdown display presented without the flashing upraised hand than for the countdown display with the upraised hand. The participants' average reported confidence in their judgment was also lower for the countdown-only condition, and their interval judgment response times also showed a negative effect of the countdown-only display. Implications of the study findings with regard to visual impairment and signal displays for the pedestrian change interval are discussed.

Size-induced distortions in perceptual maps of visual space

In order to interact with our environment, the human brain constructs maps of visual space. The orderly mapping of external space across the retinal surface, termed retinotopy, is maintained at subsequent levels of visual cortical processing and underpins our capacity to make precise and reliable judgments about the relative location of objects around us. While these maps, at least in the visual system, support high precision judgments about the relative location of objects, they are prone to significant perceptual distortion. Here, we ask observers to estimate the separation of two visual stimuli--a spatial interval discrimination task. We show that large stimulus sizes require much greater separation in order to be perceived as having the same separation as small stimulus sizes. The relationship is linear, task independent, and unrelated to the perceived position of object edges. We also show that this type of spatial distortion is not restricted to the object itself but can also be revealed by changing the spatial scale of the background, while object size remains constant. These results indicate that fundamental spatial properties, such as retinal image size or the scale at which an object is analyzed, exert a marked influence on spatial coding.

Temporal discrimination learning for treatment of gait dysfunction in Parkinson&rsquo;s disease: a feasibility study using single subject design

Freezing of gait in Parkinson’s disease may be attributed to dysfunctional neural timing that alters stride time variability. This study investigated the feasibility of a five-day perceptual timing training program using an auditory interval discrimination task to reduce stride time variability in Parkinson’s disease. Results showed that training produced an increase in time-discrimination acuity in a Parkinson’s disease patient, followed by a decrease in stride time variability. Effects persisted six weeks after training. No learningtransfer effects were found in a patient trained in a pitch discrimination task. In conclusion, interval discrimination training may reduce temporal gait irregularities in Parkinson’s disease.

Slow Modulation of Ongoing Discharge in the Auditory Cortex during an Interval-Discrimination Task

In this study, we recorded single unit activity from rat auditory cortex while the animals performed an interval-discrimination task. The animals had to decide whether two auditory stimuli were separated by either 150 or 300 ms, and go to the left or right nose poke accordingly. Spontaneous firing in between auditory responses was compared in the attentive versus non-attentive brain states. We describe the firing rate modulation detected during intervals while there was no auditory stimulation. Nearly 18% of neurons (n = 14) showed a prominent neuronal discharge during the interstimulus interval, in the form of an upward or downward ramp towards the second auditory stimulus. These patterns of spontaneous activity were often modulated in the attentive versus passive trials. Modulation of the spontaneous firing rate during the task was observed not only between auditory stimuli, but also in the interval preceding the stimulus. These slow modulatory components could be locally generated or the result of a top-down influence originated in higher associative association areas. Such a neuronal discharge may be related to the computation of the interval time and contribute to the perception of the auditory stimulus.

Time compression increases with eccentricity: a magnocellular property

Accurate time perception is crucial in peripheral vision especially for the spatial perception during actions. To investigate the dynamics of time perception in peripheral vision, parvocellular-biased and magnocellular-biased flashes were presented at different eccentricities (0-48 degrees ) in an interflash interval discrimination task. Results showed an increase in time compression with eccentricity for both stimuli (magnocellular-biased and parvocellular-biased flashes). Nevertheless, when stimulus visibility was 'equalized' across the visual field, the increase in time compression was only found for magnocellular-biased stimuli. Thus, we suggest that the magnocellular pathway accounts for time underestimation. Moreover, its increase with eccentricity could be an inherent property of the magnocellular system more than a result of a decrease in stimulus visibility.