Temporal features of size constancy for perception and action in a real-world setting: A combined EEG-kinematics study

A stable representation of object size, in spite of continuous variations in retinal input due to changes in viewing distance, is critical for perceiving and acting in a real 3D world. In fact, our perceptual and visuo-motor systems exhibit size and grip constancies in order to compensate for the natural shrinkage of the retinal image with increased distance. The neural basis of this size-distance scaling remains largely unknown, although multiple lines of evidence suggest that size-constancy operations might take place remarkably early, already at the level of the primary visual cortex. In this study, we examined for the first time the temporal dynamics of size constancy during perception and action by using a combined measurement of event-related potentials (ERPs) and kinematics. Participants were asked to maintain their gaze steadily on a fixation point and perform either a manual estimation or a grasping task towards disks of different sizes placed at different distances. Importantly, the physical size of the target was scaled with distance to yield a constant retinal angle. Meanwhile, we recorded EEG data from 64 scalp electrodes and hand movements with a motion capture system. We focused on the first positive-going visual evoked component peaking at approximately 90 ms after stimulus onset. We found earlier latencies and greater amplitudes in response to bigger than smaller disks of matched retinal size, regardless of the task. In line with the ERP results, manual estimates and peak grip apertures were larger for the bigger targets. We also found task-related differences at later stages of processing from a cluster of central electrodes, whereby the mean amplitude of the P2 component was greater for manual estimation than grasping. Taken together, these findings provide novel evidence that size constancy for real objects at real distances occurs at the earliest cortical stages and that early visual processing does not change as a function of task demands.

How do the sleep features that characterise depression impact memory?

Depression is associated with general sleep disturbance and abnormalities in sleep physiology. For example, compared with control subjects, depressed patients exhibit lower sleep efficiency, longer rapid eye movement (REM) sleep duration, and diminished slow-wave activity during non-REM sleep. A separate literature indicates that depression is also associated with many distinguishing memory characteristics, including emotional memory bias, overgeneral autobiographical memory, and impaired memory suppression. The sleep and memory features that hallmark depression may both contribute to the onset and maintenance of the disorder. Despite our rapidly growing understanding of the intimate relationship between sleep and memory, our comprehension of how sleep and memory interact in the aetiology of depression remains poor. In this narrative review, we consider how the sleep signatures of depression could contribute to the accompanying memory characteristics.

The shared and unique neural correlates of personal semantic, general semantic, and episodic memory

One of the most common distinctions in long-term memory is that between semantic (i.e., general world knowledge) and episodic (i.e., recollection of contextually specific events from one's past). However, emerging cognitive neuroscience data suggest a surprisingly large overlap between the neural correlates of semantic and episodic memory. Moreover, personal semantic memories (i.e., knowledge about the self and one's life) have been studied little and do not easily fit into the standard semantic-episodic dichotomy. Here, we used fMRI to record brain activity while 48 participants verified statements concerning general facts, autobiographical facts, repeated events, and unique events. In multivariate analysis, all four types of memory involved activity within a common network bilaterally (e.g., frontal pole, paracingulate gyrus, medial frontal cortex, middle/superior temporal gyrus, precuneus, posterior cingulate, angular gyrus) and some areas of the medial temporal lobe. Yet the four memory types differentially engaged this network, increasing in activity from general to autobiographical facts, from autobiographical facts to repeated events, and from repeated to unique events. Our data are compatible with a component process model, in which declarative memory types rely on different weightings of the same elementary processes, such as perceptual imagery, spatial features, and self-reflection.

From jamais to déjà vu: The respective roles of semantic and episodic memory in novelty monitoring and involuntary memory retrieval

Barzykowski and Moulin's model proposes that déjà vu and involuntary autobiographical memories are the result of a continuously active memory system that tracks the novelty of situations. Déjà vu would only have episodic content and concern interpretation of prior experiences. We argue that these aspects of the model would gain to be clarified and explored further and we suggest possible directions.

Expectation-based gist facilitation: Rapid scene understanding and the role of top-down information

Scene meaning is processed rapidly, with "gist" extracted even when presentation duration spans a few dozen milliseconds. This has led some to suggest a primacy of bottom-up information. However, gist research has typically relied on showing successions of unrelated scene images, contrary to our everyday experience in which the world unfolds around us in a predictable manner. Thus, we investigated whether top-down information-in the form of observers' predictions of an upcoming scene-facilitates gist processing. Within each trial, participants (N = 370) experienced a series of images, organized to represent an approach to a destination (e.g., walking down a sidewalk), followed by a target scene either congruous or incongruous with the expected destination (e.g., a store interior or a bedroom). A series of behavioral experiments revealed that appropriate expectations facilitated gist processing; inappropriate expectations interfered with gist processing; sequentially-arranged scene images benefitted gist processing when semantically related to the target scene; expectation-based facilitation was most apparent when presentation duration was most curtailed; and findings were not simply the result of response bias. We then investigated the neural correlates of predictability on scene processing using event-related potentials (ERPs) (N = 24). Congruency-related differences were found in a putative scene-selective ERP component, related to integrating visual properties (P2), and in later components related to contextual integration including semantic and syntactic coherence (N400 and P600, respectively). Together, results suggest that in real-world situations, top-down predictions of an upcoming scene influence even the earliest stages of its processing, affecting both the integration of visual properties and meaning. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Cognitive and neuroimaging markers for preclinical vascular cognitive impairment

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Explores the cognitive correlates of midlife risk factors of pre-clinical vascular cognitive impairment.

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Midlife cardiovascular risks associated with reduces neural integrity in parietal to anterior structures and may identify at-risk individuals.

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Novel experimental investigation testing fronto-parietal structures is required to increase specificity and sensitivity to pre-clinical VCI and inform clinical testing and diagnostic pathways of at-risk individuals.

Detection of incipient cognitive impairment and dementia pathophysiology is critical to identify preclinical populations and target potentially disease modifying interventions towards them. There are currently concerted efforts for such detection for Alzheimer's disease (AD). By contrast, the examination of cognitive markers and their relationship to biomarkers for Vascular Cognitive Impairment (VCI) is far less established, despite VCI being highly prevalent and often concomitantly presenting with AD. Critically, vascular risk factors are currently associated with the most viable treatment options via pharmacological and non-pharmacological intervention, hence early identification of vascular factors have important implications for modifying dementia disease trajectories. The aim of this review is to examine the current evidence of cognitive marker correlates to VCI pathology. We begin by examining midlife risk factors that predict VCI. Next, discuss preclinical cognitive hallmarks of VCI informed by insights from neuropsychological assessment, network connectivity and ERP/EEG experimental findings. Finally, we discuss limitations of current cognitive assessments and the need for future cognitive test development to inform diagnostic assessment. As well as, intervention outcome measures for preclinical VCI. In turn, these tests will inform earlier detection of vascular changes and allow implementation of disease intervention approaches.

Altering access to autobiographical episodes with prior semantic knowledge

Within autobiographical knowledge, semantic and episodic memory are traditionally considered separate, but newer models place them along a continuum, which raises the possibility of an intermediate form of knowledge - personal semantics. This study tested how different types of semantics - general semantics and two forms of personal semantics - impact access to personal episodic memories. In two experiments, participants made a series of true/false judgments about a prime statement, which reflected a general semantic fact, a context-dependent (e.g., repeated event) or context-independent (e.g., trait), personal semantic fact and then retrieved a specific past episodic memory. There was a significantly stronger priming effect for accessing specific episodic memories after judging personal semantic facts versus general facts. We also found that context-dependent and -independent personal semantic facts had separable priming effects on episodic memory. These findings support a continuum model of memory and verifies that there are multiple forms of personal knowledge.

The N170 event-related potential differentiates congruent and incongruent gaze responses in gaze leading

To facilitate social interactions, humans need to process the responses that other people make to their actions, including eye movements that could establish joint attention. Here, we investigated the neurophysiological correlates of the processing of observed gaze responses following the participants’ own eye movement. These observed gaze responses could either establish, or fail to establish, joint attention. We implemented a gaze leading paradigm in which participants made a saccade from an on-screen face to an object, followed by the on-screen face either making a congruent or incongruent gaze shift. An N170 event-related potential was elicited by the peripherally located gaze shift stimulus. Critically, the N170 was greater for joint attention than non-joint gaze both when task-irrelevant (Experiment 1) and task-relevant (Experiment 2). These data suggest for the first time that the neurocognitive system responsible for structural encoding of face stimuli is affected by the establishment of participant-initiated joint attention.

Scrutinizing the grey areas of declarative memory: Do the self-reference and temporal orientation of a trait knowledge task modulate the Late Positive Component (LPC)?

Knowledge about the future self may engage cognitive processes typically ascribed to episodic memory, such as awareness of the future self as an extension of the current self (i.e., autonoetic awareness) and the construction of future events. In a prior study (Tanguay et al., 2018), temporal orientation influenced the Late Positive Component (LPC), an ERP correlate of recollection. The LPC amplitude for present traits was intermediate between semantic and episodic memory, whereas thinking about one's future traits produced a larger LPC amplitude that was similar to episodic memory. Here, we examined further the effect of temporal orientation on the LPC amplitude and investigated if it was influenced by whether knowledge concerns the self or another person, with the proximity of the other being considered. Participants verified whether traits (e.g., Enthusiastic) were true of themselves and the "other," both now and in the future. Proximity of the other person was manipulated between subjects, such that participants either thought about the typical traits of a close friend (n = 31), or those of their age group more broadly (n = 35). Self-reference and temporal orientation interacted: The LPC amplitude for future knowledge was larger than for present knowledge, but only for the self. This effect of temporal orientation was not observed when participants thought about the traits of other people. The proximity of the other person did not modify these effects. Future-oriented cognition can engage different cognitive processes depending on self-reference; knowledge about the personal future increased the LPC amplitude unlike thinking about the future of other people. Our findings strengthen the notion of self-knowledge as a grey area between semantic and episodic memory.

An historical perspective on Endel Tulving's episodic-semantic distinction

The distinction between episodic and semantic memory, proposed by Endel Tulving in 1972, remains a key concept in contemporary Cognitive Neuroscience. Here we review how this distinction evolved in Tulving's writings over the years. Crucially, from 1972 onward, he argued that the two forms of memory were inter-dependent and that their interaction was an essential feature of normal episodic memory function. Moreover, later elaborations of the theory clearly proposed that these interactions formed the basis of normal declarative memory functioning. A later but crucial aspect of Tulving's contribution was his stress on the importance of subjective experience, which, according to him, "should be the ultimate object of interest, the central aspect of remembering that is to be explained and understood". We relate these and his numerous other ideas to current perspectives about the organization and function of human memory.

Predicting memory formation over multiple study episodes

Repeated study typically improves episodic memory performance. Two different types of explanations of this phenomenon have been put forward: (1) reactivating the same representations strengthens and stabilizes memories, or (2) greater encoding variability benefits memory by promoting richer traces. The present experiment directly compared these predictions in a design with multiple repeated study episodes, allowing to dissociate memory for studied items and their context of study. Participants repeatedly encoded names of famous people four times, either in the same task, or in different tasks. During the test phase, an old/new judgment task was used to assess item memory, followed by a source memory judgment about the encoding task. Consistent with predictions from the encoding variability view, encoding stimulus in different contexts resulted in higher item memory. In contrast, consistent with the reactivation view, source memory performance was higher when participants encoded stimuli in the same task repeatedly. Taken together, our findings indicate that encoding variability benefits episodic memory, by increasing the number of items that are recalled. These benefits are however at the expenses of source recollection and memory for details, which are decreased, likely due to interference and generalization across contexts.

Physical aggression and attentional bias to angry faces: An event related potential study

This study aimed to identify the neural correlates of aggression-related attentional selectivity to angry faces in physical aggression. Physical aggression in a non-clinical sample of young men (N = 36) was measured using an aggression questionnaire. Visual attentional bias to angry faces was assessed using a dot-probe task during which angry and neutral faces were presented simultaneously, and EEG was recorded. Median split and correlational analyses were conducted to assess the relationship between physical aggression and attentional bias. Behavioural results indicated that higher levels of physical aggression were associated with greater attentional bias to angry faces. ERP results revealed an interaction where males with higher physical aggression had undifferentiated P3 amplitudes to angry and neutral trials, whereas low physical aggression males exhibited greater P3 amplitude to angry than to neutral trials (effect of probe congruency). Increased levels of physical aggression were also significantly correlated with increased P3 amplitude to probes replacing neutral faces, relative to angry faces. It was concluded that the aggressive males selectively attend to angry faces, and that attentional bias is characterized by undifferentiated P3 amplitude. We propose that this results from an inferior ability to downregulate competing angry face distractors when responding to probes replacing neutral faces (as reflected by the P3 response). These findings indicate that attentional bias to angry faces in individuals with higher physical aggression is characterized by a distinctive ERP signature; this could inform the development of therapeutic interventions seeking to reduce aggression.

A Central Component of the N1 Event-Related Brain Potential Could Index the Early and Automatic Inhibition of the Actions Systematically Activated by Objects

Stimuli of the environment, like objects, systematically activate the actions they are associated to. These activations occur extremely fast. Nevertheless, behavioral data reveal that, in most cases, these activations are then automatically inhibited, around 100 ms after the occurrence of the stimulus. We thus tested whether this early inhibition could be indexed by a central component of the N1 event-related brain potential (ERP). To achieve that goal, we looked at whether this ERP component is larger in tasks that could increase the inhibition and in trials where reaction times (RTs) happen to be long. The illumination of a real space bar of a keyboard out of the dark was used as a stimulus. To maximize the modulation of the inhibition, the task participants had to perform was manipulated across blocks. A look-only task and a count task were used to increase inhibition and an immediate press task was used to decrease it. ERPs of the two block-conditions where presses had to be prevented and where the largest central N1s were predicted were compared to those elicited in the press task, differentiating the ERPs to the third of the trials where presses were the slowest from the ERPs to the third of the trials with the fastest presses. Despite larger negativities due to lateralized readiness potentials (LRPs) and despite greater attention likely in immediate press-trials, central N1s were found to be minimal for the fastest presses, intermediate for the slowest ones and maximal for the two no-press conditions. These results thus provide a strong support for the idea that the central N1 indexes an early and short lasting automatic inhibition of the actions systematically activated by objects. They also confirm that the strength of this automatic inhibition spontaneously fluctuates across trials and tasks. On the other hand, just before N1s, parietal P1s were found larger for fastest presses. They might thus index the initial activation of these actions. Finally, consistent with the idea that N300s index late inhibition processes, that occur preferentially when the task requires them, these ERPs were quasi absent for fast presses trials and much larger in the three other conditions.

WITHDRAWN: Physical aggression and attentional bias to angry faces: An event related potential study

This article has been withdrawn at the request of the authors. The authors have opted to update their article and have resubmitted it to the journal as a new submission. The updated article has now been accepted and can be found here: https://doi.org/10.1016/j.brainres.2019.146387. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Predicting our own and others' future preferences: The role of social distance

People underestimate how much their preferences will change in the future, a phenomenon sometimes referred to as a "presentism bias." Recently, we found that this presentism bias is attenuated when thinking about the preferences of other people. The aim of this study was to investigate whether predicting future preferences also differs depending on the level of social distance between self and other. A total of 67 participants completed a perspective-taking task in which they were required to think about their own preferences, those of a generic peer, and those of a close other both now and in the future. They were also asked to consider the preferences of an older adult now. Participants predicted less change between their current and future preferences than between the current and future preferences of a generic peer. Predicted change in preferences for a close other were similar, but not identical, to those made for the self. When considering relevant future preferences, participants predicted less change for themselves than for their close others and less change for close others than for generic peers. In other words, as social distance increases, the presentism bias decreases. Interestingly, participants estimated that both they and their peers would not change so much that they become similar to current older adults. Simulating the future perspectives of a generic peer or, even better, the current perspectives of an older adult may thus result in improved long-term decision-making, as it may enable a more realistic estimation of the magnitude of likely changes in the future.

N400 effects of semantic richness can be modulated by task demands

Semantic richness is a multidimensional construct that can be defined as the amount of semantic information associated with a concept.

OBJECTIVE

To investigate neurophysiological correlates of semantic richness information associated with words and its interaction with task demands.

METHOD

Two different dimensions of semantic richness (number of associates and number of semantic neighbors) were investigated using event-related potentials (ERPs) in lexical decision (LDT) and semantic categorization tasks (SCT) using the same stimuli in 2 groups of participants (24 in each group).

RESULTS

The amplitude of the N400 ERP component, which is associated with semantic processing, was smaller for words with a high number of associates (p = .003 at fronto-centro-parietal sites) or semantic neighbors (p < .03 at centro-parietal sites) than for words with a low number of associates or number of semantic neighbors, in the LDT but not the SCT.

CONCLUSIONS

These results suggest that the effects of semantic richness vary with task demands and may be used in a top-down manner to accommodate the current context. (PsycINFO Database Record

You'll change more than I will: Adults' predictions about their own and others' future preferences

It has been argued that adults underestimate the extent to which their preferences will change over time. We sought to determine whether such mispredictions are the result of a difficulty imagining that one's own current and future preferences may differ or whether it also characterizes our predictions about the future preferences of others. We used a perspective-taking task in which we asked young people how much they liked stereotypically young-person items (e.g., Top 40 music, adventure vacations) and stereotypically old-person items (e.g., jazz, playing bridge) now, and how much they would like them in the distant future (i.e., when they are 70 years old). Participants also made these same predictions for a generic same-age, same-sex peer. In a third condition, participants predicted how much a generic older (i.e., age 70) same-sex adult would like items from both categories today. Participants predicted less change between their own current and future preferences than between the current and future preferences of a peer. However, participants estimated that, compared to a current older adult today, their peer would like stereotypically young items more in the future and stereotypically old items less. The fact that peers' distant-future estimated preferences were different from the ones they made for "current" older adults suggests that even though underestimation of change of preferences over time is attenuated when thinking about others, a bias still exists.

Autobiographically Significant Concepts: More Episodic than Semantic in Nature? An Electrophysiological Investigation of Overlapping Types of Memory

A common assertion is that semantic memory emerges from episodic memory, shedding the distinctive contexts associated with episodes over time and/or repeated instances. Some semantic concepts, however, may retain their episodic origins or acquire episodic information during life experiences. The current study examined this hypothesis by investigating the ERP correlates of autobiographically significant (AS) concepts, that is, semantic concepts that are associated with vivid episodic memories. We inferred the contribution of semantic and episodic memory to AS concepts using the amplitudes of the N400 and late positive component, respectively. We compared famous names that easily brought to mind episodic memories (high AS names) against equally famous names that did not bring such recollections to mind (low AS names) on a semantic task (fame judgment) and an episodic task (recognition memory). Compared with low AS names, high AS names were associated with increased amplitude of the late positive component in both tasks. Moreover, in the recognition task, this effect of AS was highly correlated with recognition confidence. In contrast, the N400 component did not differentiate the high versus low AS names but, instead, was related to the amount of general knowledge participants had regarding each name. These results suggest that semantic concepts high in AS, such as famous names, have an episodic component and are associated with similar brain processes to those that are engaged by episodic memory. Studying AS concepts may provide unique insights into how episodic and semantic memory interact.

Healthy people with delusional ideation change their mind with conviction

Emotional distress and reasoning biases are two factors known to contribute to delusions. As a step towards elucidating mechanisms underlying delusions, the main aim of this study was to evaluate a possible "jumping to new conclusions" reasoning bias in healthy people with delusional ideation and its association with emotions. We surveyed 80 healthy participants, measuring levels of depression, anxiety, cognitive error and delusional ideation. Participants completed two versions of the beads task to evaluate their reasoning style. Results showed that people with delusional ideation reached a conclusion after less information, as expected. Interestingly, they also tended to change their conclusions more often than people without delusional ideation and did so with greater conviction. Depression and cognitive errors were strong predictors of delusional ideation but not of reasoning style. We conclude that delusional ideation in non-psychotic individuals is independently predicted by depressive symptoms and by a high conviction in new conclusions.

Schizotypal traits and N400 in healthy subjects

We examined whether correlations previously found between symptoms of schizophrenia patients and the amplitude of an event-related potential (ERP), the N400, could be also found between schizotypal experiences of healthy subjects and the N400. We chose a semantic categorization task previously used with patients. Schizotypal experiences were measured with the schizotypal personality questionnaire (SPQ). The effects of the other factors were controlled for when assessing the correlations between each SPQ factor and N400s. These correlations were assessed at each electrode site to see whether their distribution on the scalp follows that of the N400 effect. Disorganization and interpersonal scores were found to correlate with ERPs in the N400 time window, as previously reported for the comparable symptoms of patients. However, the scalp distribution of these correlations differed from that of the N400 effect.

Semantic processing of highly repeated concepts presented in single-word trials: Electrophysiological and behavioral correlates

Repetition has often been associated with a reduction or a suppression of semantic effects. However, several studies have reported that semantic processing can still be effective for repeated target stimuli when the context, prime word or sentence frame, changes from trial to trial. This type of context-target designs allows to study semantic associations between repeated words. However, it is not optimal to study single concepts or categories and therefore structural aspects of semantic memory. Here, we tested whether semantic effects could be observed if single-word trials were used. Concrete and Abstract words were presented multiple times in two concrete-abstract classification experiments. In the first experiment, 6 words of each category were repeatedly presented. In the second experiment, only one word of each category was used. Results of both experiments showed significant effects of concreteness on reaction times and N400-like event-related potentials (ERPs), which were comparable to those reported in non-repeated conditions. In the second experiment, in which repetitions occurring in consecutive and non-consecutive trials were contrasted, N400-like effects were observed only for non-consecutive repetitions. These findings suggest that it could be possible to study the brain activity corresponding to individual concepts in experimental designs using single-word trials, provided that consecutive repetitions are avoided.

N400-like potentials and reaction times index semantic relations between highly repeated individual words

The N400 ERP is an electrophysiological index of semantic processing. Its amplitude varies with the semantic category of words, their concreteness, or whether their meaning matches that of a preceding context. The results of a number of studies suggest that these effects could be markedly reduced or suppressed for stimuli that are repeated. Nevertheless, we have recently shown that significant effects of semantic matching and category could be obtained on N400-like potentials elicited by massively repeated target words in a prime-target semantic categorization task. If such effects could be obtained when primes also are repeated, it would then be possible to study the semantic associations between individual words. The present study thus aimed to test this hypothesis while (1) controlling for a potential contribution of physical matching to the processing of repeated targets and (2) testing if the N400-like effects obtained in these conditions are modulated by task instruction, as are classic N400 effects. Two category words were used as primes and two exemplars as targets. In one block of trials, subjects had to respond according to the semantic relation between prime and target (semantic instruction) and, in another block, they had to report changes in letter case (physical instruction). Results showed that the amplitude of the N400-like ERP obtained was modulated by semantic matching and category but not by letter case. The effect of semantic matching was observed only in the semantic instruction block. Interestingly, the effect of category was not modulated by task instruction. An independent component analysis showed that the component that made the greatest contribution to the effect of semantic matching in the time window of the N400-like potential had a scalp distribution similar to that reported for the N400 and was best fit as a bilateral generator in the superior temporal gyrus. The use of repetition could thus allow, at least in explicit semantic tasks, a drastic simplification of N400 protocols. Highly repeated individual words could be used to study semantic relations between individual concepts.

P300 asymmetry and positive symptom severity: a study in the early stage of a first episode of psychosis

The amplitude of the P300 event-related potential (ERP) has been reported to be reduced over left compared to right temporal sites in schizophrenia patients. This left temporal P300 reduction has been associated with positive symptom severity and gray matter reduction in the left superior temporal gyrus. We investigated a group of patients with a first episode of schizophrenia spectrum psychosis and a group of normal controls to verify if P300 amplitude asymmetry already exists around the time of presentation for treatment. Relative to normal control subjects, no P300 asymmetry was found in patients. Nevertheless, P300 asymmetry was correlated with the severity of positive symptoms and worse global functioning (GAF), a good predictor of poor outcome.

Time is a rubberband: neuronal activity in monkey motor cortex in relation to time estimation

Anticipation of predictable events is crucial for organizing motor performance. Using instructed delay tasks, it has been shown that even when delay duration is kept constant, reaction time fluctuates from trial to trial. As time estimation is at the core of anticipatory behavior, it is reasonable to speculate whether neuronal delay activity correlates with the subjective estimate of time. As a consequence of the scalar property of time estimation processes, the variability in time estimation increases continuously as time passes during the delay. This scalar property may then be reflected in the increasing variability in neuronal delay activity. We thus studied the influence of temporal prior information on neuronal delay activity in monkey motor cortex in two conceptually different tasks in which two equally probable delay durations were randomly presented. We hypothesized that if one considers the animal's subjective time as the time which elapses between the first (instruction) signal and movement onset, then, by suppressing this temporal variability, across-trial variability in neuronal discharge should decrease. We thus defined a new time scale in each trial such that, after rescaling, the time between the instruction signal and movement onset was identical in all trials. Each spike was then displaced in time accordingly. As expected, the variability in the timing of neuronal peak discharges no longer increased during the trial. This suggests a direct link between the temporal profile of spiking activity and time estimation. The timing of motor cortical activity reflected the 'elasticity' of the animal's subjective time.