Implicit Timing as the Missing Link between Neurobiological and Self Disorders in Schizophrenia?

New clues for the role of cerebellum in schizophrenia and the associated cognitive impairment

Schizophrenia (SZ) is a complex neuropsychiatric disorder associated with severe cognitive dysfunction. Although research has mainly focused on forebrain abnormalities, emerging results support the involvement of the cerebellum in SZ physiopathology, particularly in Cognitive Impairment Associated with SZ (CIAS). Besides its role in motor learning and control, the cerebellum is implicated in cognition and emotion. Recent research suggests that structural and functional changes in the cerebellum are linked to deficits in various cognitive domains including attention, working memory, and decision-making. Moreover, cerebellar dysfunction is related to altered cerebellar circuit activities and connectivity with brain regions associated with cognitive processing. This review delves into the role of the cerebellum in CIAS. We initially consider the major forebrain alterations in CIAS, addressing impairments in neurotransmitter systems, synaptic plasticity, and connectivity. We then focus on recent findings showing that several mechanisms are also altered in the cerebellum and that cerebellar communication with the forebrain is impaired. This evidence implicates the cerebellum as a key component of circuits underpinning CIAS physiopathology. Further studies addressing cerebellar involvement in SZ and CIAS are warranted and might open new perspectives toward understanding the physiopathology and effective treatment of these disorders.

Temporal imprecision and phase instability in schizophrenia resting state EEG

Schizophrenia is characterized by temporal imprecision and irregularities on neuronal, psychological cognitive, and behavioral levels which are usually tested during task-related activity. This leaves open whether analogous temporal imprecision and irregularities can already be observed in the brain's spontaneous activity as measured during the resting state; this is the goal of our study. Building on recent task-related data, we, using EEG, aimed to investigate the temporal precision and regularity of phase coherence over time in healthy, schizophrenia, and bipolar disorder participants. To this end, we developed a novel methodology, nominal frequency phase stability (NFPS), that allows to measure stability over phase angles in selected frequencies. By applying sample entropy quantification to the time-series of the nominal frequency phase angle time series, we found increased irregularities in theta activity over a frontocentral electrode in schizophrenia but not in bipolar disorder. We therefore assume that temporal imprecision and irregularity already occur in the brain's spontaneous activity in schizophrenia.

Temporal Order Judgments in Schizophrenia and Bipolar Disorders – Explicit and Implicit Measures

Ordering events in time is essential for the understanding of causal relationships between successive events. Incorrect causal links can lead to false beliefs and an altered perception of reality. These symptoms belong to psychosis, which is present in schizophrenia (SZ) spectrum and bipolar (BP) disorder. Experimental results show that patients with SZ have an altered perception of temporal order, while there are no data in patients with BP. We investigated the ability of patients with SZ, BP, and controls to judge the order of stimuli with a 100-ms Stimulus Onset Asynchrony (SOA), and how such large asynchronies facilitate temporal order judgments for small asynchronies. Explicit temporal order effects suggest that patients with SZ perform worse at a long SOA (100 ms) as compared to controls, whereas patients with BP show no difference compared to controls or to patients with SZ. Implicit order effects reveal improved performances in case of identical as compared to different relative order between two successive trials for all groups, with no differences between the groups. We replicated explicit order impairments in patients with SZ compared to controls, while implicit effects appear to be preserved. This difficulty for patients to consciously order stimuli in time might be understood under the light of the loosening-of-associations phenomenon well described in SZ. Further, we showed that patients with BP do not reveal such an explicit order impairment which is consistent with phenomenological descriptions, suggesting a difference in time experience in patients with SZ and BP.

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

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

Implicit Versus Explicit Timing-Separate or Shared Mechanisms?

Time implicitly shapes cognition, but time is also explicitly represented, for instance, in the form of durations. Parsimoniously, the brain could use the same mechanisms for implicit and explicit timing. Yet, the evidence has been equivocal, revealing both joint versus separate signatures of timing. Here, we directly compared implicit and explicit timing using magnetoencephalography, whose temporal resolution allows investigating the different stages of the timing processes. Implicit temporal predictability was induced in an auditory paradigm by a manipulation of the foreperiod. Participants received two consecutive task instructions: discriminate pitch (indirect measure of implicit timing) or duration (direct measure of explicit timing). The results show that the human brain efficiently extracts implicit temporal statistics of sensory environments, to enhance the behavioral and neural responses to auditory stimuli, but that those temporal predictions did not improve explicit timing. In both tasks, attentional orienting in time during predictive foreperiods was indexed by an increase in alpha power over visual and parietal areas. Furthermore, pretarget induced beta power in sensorimotor and parietal areas increased during implicit compared to explicit timing, in line with the suggested role for beta oscillations in temporal prediction. Interestingly, no distinct neural dynamics emerged when participants explicitly paid attention to time, compared to implicit timing. Our work thus indicates that implicit timing shapes the behavioral and sensory response in an automatic way and is reflected in oscillatory neural dynamics, whereas the translation of implicit temporal statistics to explicit durations remains somewhat inconclusive, possibly because of the more abstract nature of this task.

Physical Time Within Human Time

A possible solution is offered to help resolve the "two times problem" regarding the veridical and illusory nature of time. First it is recognized that the flow (passage) of time is part of a wider array of temporal experiences referred to as manifest time, all of which need to be reconciled. Then, an information gathering and utilizing system (IGUS) model is used as a basis for a view of manifest time. The model IGUS robot of Hartle that solves the "unique present" debate is enhanced with veridical and (corresponding) illusory components of not only the flow of time but also the larger entity of manifest time, providing a dualistic IGUS robot that represents all of the important temporal experiences. Based upon a variety of prior experiments, that view suggests that the veridical system is a reflection of accepted spacetime cosmologies and through natural selection begets the illusory system for functional purposes. Thus, there are not two opposing times, one outside and one inside the cranium. There is just one fundamental physical time which the brain developed, now possesses and is itself sufficient for adaption but then enhances. The illusory system is intended to provide a more satisfying experience of physical time, and better adaptive behavior. Future experiments to verify that view are provided. With a complete veridical system of temporal experiences there may be less need to reify certain temporal experiences so that the two times problem is less of a problem and more of a phenomenon.

AI ethics in computational psychiatry: From the neuroscience of consciousness to the ethics of consciousness

Methods used in artificial intelligence (AI) overlap with methods used in computational psychiatry (CP). Hence, considerations from AI ethics are also relevant to ethical discussions of CP. Ethical issues include, among others, fairness and data ownership and protection. Apart from this, morally relevant issues also include potential transformative effects of applications of AI-for instance, with respect to how we conceive of autonomy and privacy. Similarly, successful applications of CP may have transformative effects on how we categorise and classify mental disorders and mental health. Since many mental disorders go along with disturbed conscious experiences, it is desirable that successful applications of CP improve our understanding of disorders involving disruptions in conscious experience. Here, we discuss prospects and pitfalls of transformative effects that CP may have on our understanding of mental disorders. In particular, we examine the concern that even successful applications of CP may fail to take all aspects of disordered conscious experiences into account.

Inattentive Perception, Time, and the Incomprehensibility of Consciousness

Cerebral energy supply is insufficient to support continuous neuronal processing of the plethora of time-constant objects that we are aware of. As a result, the brain is forced to limit processing resources to (the most relevant) cases of change. The neuronally generated world is thus temporally discontinuous. This parallels the fact that, in all relevant microscopic fundamental equations of nature, temporal change plays a dominant role. When a scientist calculates a "solution" to such an equation, integration over time is an essential step. The present Hypothesis expresses that the step from neuronal activity to phenomenal content of consciousness is reflective of a (phenomenal) "solution:" the main source of the incomprehensibility of consciousness is proposed to result from the introduction of phenomenal time-constant entities. These are "filled-in" via integration, even though neuronal data only exists for changes to these entities. In this way, a temporally continuous picture of the world phenomenally appears. Qualia are "initial conditions," which are required for integration and cannot be deduced from present data. Phenomenal "identity" (vs. "high similarity") is related to qualia. Inattentive visual perception, which is only rarely investigated, offers insights into these relationships. Introspectively, unattended vision appears rich because percepts are cumulated over long time spans, whereas attentive perception relies purely on present neuronal signals. The present Hypothesis is that a brief neuronal activity can signify long-lasting and constant phenomenal content of consciousness. Experimental support is presented that comes from discrepancies between neuronal activity and perception: transient neuronal responses to sustained stimuli, "filling-in," change blindness, identity vs. close resemblance.

Scale for Space and Time Experience in Psychosis: Converging Phenomenological and Psychopathological Perspectives

INTRODUCTION

Abnormalities in the experience of space and time are fundamental to understanding schizophrenia spectrum disorders, but the precise relation between such abnormalities and psychopathological symptoms is still unclear. Therefore, the aim of our study was to introduce a novel scale for space and time experience in psychosis (STEP), specifically devised to assess schizophrenia spectrum disorders.

METHODS

The STEP scale is a semiquantitative instrument developed on the basis of several items from previous scales and phenomenological reports addressing the experience of space and time. We applied the STEP scale to three groups of subjects (patients with schizophrenia spectrum disorders, patients with predominant affective symptoms, and healthy control subjects), to whom we also applied other more general psychopathological scales, such as the Positive and Negative Syndrome Scale and the Ego-Psychopathology Inventory.

RESULTS

Patients with schizophrenia spectrum disorders scored significantly higher on general psychopatho<X00_Del_TrennDivis>--</X00_Del_TrennDivis>logical scales relative to subjects belonging to the other groups. The STEP scale provided good psychometric properties regarding reliability. We also tested convergent and divergent validity of the STEP scale and found that space and time subscale scores of STEP significantly correlated with each other, as well as with the remaining general psychopathological scores.

DISCUSSION/CONCLUSION

We introduced the STEP scale as a novel instrument for the assessment of experience of space and time. Its psychometric properties showed high validity and reliability to identify psychopathological symptoms and enabled to differentiate patients with predominantly psychotic symptoms from those with predominantly affective symptoms. The STEP scale provides a standardized measure for assessing disturbances in the experience of space and time. Furthermore, it probably represents a leap forward toward the establishment of an additional dimension of symptoms proposed as "spatiotemporal psychopathology."

Multivariate pattern analysis of brain structure predicts functional outcome after auditory-based cognitive training interventions

Cognitive gains following cognitive training interventions are associated with improved functioning in people with schizophrenia (SCZ). However, considerable inter-individual variability is observed. Here, we evaluate the sensitivity of brain structural features to predict functional response to auditory-based cognitive training (ABCT) at a single-subject level. We employed whole-brain multivariate pattern analysis with support vector machine (SVM) modeling to identify gray matter (GM) patterns that predicted higher vs. lower functioning after 40 h of ABCT at the single-subject level in SCZ patients. The generalization capacity of the SVM model was evaluated by applying the original model through an out-of-sample cross-validation analysis to unseen SCZ patients from an independent validation sample who underwent 50 h of ABCT. The whole-brain GM volume-based pattern classification predicted higher vs. lower functioning at follow-up with a balanced accuracy (BAC) of 69.4% (sensitivity 72.2%, specificity 66.7%) as determined by nested cross-validation. The neuroanatomical model was generalizable to an independent cohort with a BAC of 62.1% (sensitivity 90.9%, specificity 33.3%). In particular, greater baseline GM volumes in regions within superior temporal gyrus, thalamus, anterior cingulate, and cerebellum predicted improved functioning at the single-subject level following ABCT in SCZ participants. The present findings provide a structural MRI fingerprint associated with preserved GM volumes at a single baseline timepoint, which predicted improved functioning following an ABCT intervention, and serve as a model for how to facilitate precision clinical therapies for SCZ based on imaging data, operating at the single-subject level.

The Self and Its Prolonged Intrinsic Neural Timescale in Schizophrenia

Schizophrenia (SCZ) can be characterized as a basic self-disorder that is featured by abnormal temporal integration on phenomenological (experience) and psychological (information processing) levels. Temporal integration on the neuronal level can be measured by the brain's intrinsic neural timescale using the autocorrelation window (ACW) and power-law exponent (PLE). Our goal was to relate intrinsic neural timescales (ACW, PLE), as a proxy of temporal integration on the neuronal level, to temporal integration related to self-disorder on psychological (Enfacement illusion task in electroencephalography) and phenomenological (Examination of Anomalous Self-Experience [EASE]) levels. SCZ participants exhibited prolonged ACW and higher PLE during the self-referential task (Enfacement illusion), but not during the non-self-referential task (auditory oddball). The degree of ACW/PLE change during task relative to rest was significantly reduced in self-referential task in SCZ. A moderation model showed that low and high ACW/PLE exerted differential impact on the relationship of self-disorder (EASE) and negative symptoms (PANSS). In sum, we demonstrate abnormal prolongation in intrinsic neural timescale during self-reference in SCZ including its relation to basic self-disorder and negative symptoms. Our results point to abnormal relation of self and temporal integration at the core of SCZ constituting a "common currency" of neuronal, psychological, and phenomenological levels.

Embodied time and the out-of-body experience of the self

Using an out-of-body paradigm, the present study provided further empirical evidence for the theory of embodied time by suggesting that the body-self plays a key role in time judgments. Looking through virtual reality glasses, the participants saw the arm of a mannequin instead of their own arm. They had to judge the duration of the interval between two (perceived) touches applied to the mannequin's body after a series of strokes had been viewed being made to the mannequin and tactile strokes had been administered to the participants themselves. These strokes were administered either synchronously or asynchronously. During the interval, a pleasant (touch with a soft paintbrush) or an unpleasant stimulation (touch with a pointed knife) was applied to the mannequin. The results showed that the participants felt the perceived tactile stimulations in their own bodies more strongly after the synchronous than the asynchronous stroking condition, a finding which is consistent with the out-of-body illusion. In addition, the interval duration was judged longer in the synchronous than in the asynchronous condition. This time distortion increased the greater the individual out-of-body experience was. Our results therefore highlight the importance of the awareness of the body-self in the processing of time, i.e., the significance of embodied time.

The evolving sense of agency: Context recency and quality modulate the interaction between prospective and retrospective processes

Humans acquire a sense of agency through their interactions with the world and their sensory consequences. Previous studies have highlighted stable agency-related phenomena like intentional binding, which depend on both prospective, context-dependent and retrospective, outcome-dependent processes. In the current study, we investigated the interaction between prospective and retrospective processes underlying the adaptation of an ongoing sense of agency. The results showed that prospective intentional binding developed during a temporal window of up to 20 prior events was independent of the nature of the ongoing event. By contrast, the characteristics of the ongoing event retrospectively influenced prospective intentional binding developed during a temporal window narrower than 6 prior events. These findings characterize the interaction between prospective and retrospective mechanisms as a fundamental process to continuously update the sense of agency through sensorimotor learning. High psychosis-like experience traits weakened this interaction, suggesting that reduced adaption to the context contributes to altered self-experience.

The Implementation of Predictions During Sequencing

Optimal control mechanisms require prediction capabilities. If one cannot predict the consequences of a motor act or behavior, one will continually collide with walls or become a social pariah. "Looking into the future" is thus one of the most important prerequisites for smooth movements and social interactions. To achieve this goal, the brain must constantly predict future events. This principle applies to all domains of information processing, including motor and cognitive control, as well as the development of decision-making skills, theory of mind, and virtually all cognitive processes. Sequencing is suggested to support the predictive capacity of the brain. To recognize that events are related, the brain must discover links among them in the spatiotemporal domain. To achieve this, the brain must often hold one event in working memory and compare it to a second one, and the characteristics of the two must be compared and correctly placed in space and time. Among the different brain structures involved in sequencing, the cerebellum has been proposed to have a central function. We have suggested that the operational mode of the cerebellum is based on "sequence detection" and that this process is crucial for prediction. Patterns of temporally or spatially structured events are conveyed to the cerebellum via the pontine nuclei and compared with actual ones conveyed through the climbing fibers olivary inputs. Through this interaction, data on previously encountered sequences can be obtained and used to generate internal models from which predictions can be made. This mechanism would allow the cerebellum not only to recognize sequences but also to detect sequence violations. Cerebellar pattern detection and prediction would thus be a means to allow feedforward control based on anticipation. We will argue that cerebellar sequencing allows implementation of prediction by setting the correct excitatory levels in defined brain areas to implement the adaptive response for a given pattern of stimuli that embeds sufficient information to be recognized as a previously encountered template. Here, we will discuss results from human and animal studies and correlate them with the present understanding of cerebellar function in cognition and behavior.

A reflection upon methods to explore timing in patients with schizophrenia

Phenomenologists have provided a detailed description of the disorders of the subjective experience associated with minimal-self disorders in patients with schizophrenia. Those patients report a range of distortions of their conscious experiences, including a sense of inner void, confusion between self and others, and, sometimes, a disruption of the sense of time. These reports have been interpreted as distortion of the first-person perspective and a lack of immersion in the world, associated with a breakdown of the temporal structure of consciousness, and especially a disruption of the sense of time continuity. Further, it has been proposed that these disruptions are based on a difficulty to retain past information and to predict future information, that is, the mechanisms that help to relate events with one another and to reach a sense of time continuity. Experimental psychology results seem to converge to similar conclusions, inasmuch as some results in patients with schizophrenia suggest a deficient ability to predict sequences of events at the millisecond level. Several studies have underlined this convergence. Here we reflect on the limits of both the phenomenological and experimental psychology approaches, and of the convergence of their hypotheses. We think that this reflection is necessary to avoid premature conclusions on the mechanisms underlying the impairments in patients, but also to enrich our understanding of schizophrenia.

Setting the beat of an internal clock: Effects of dexamphetamine on different interval ranges of temporal processing in healthy volunteers

Drug studies are powerful models to investigate the neuropharmacological mechanisms underlying temporal processing in humans. This study administered dexamphetamine to 24 healthy volunteers to investigate time perception at different time scales, along with contributions from working memory. Healthy volunteers were administered 0.45 mg/kg dexamphetamine or placebo in a double-blind, crossover, placebo-controlled design. Time perception was assessed using three experimental tasks: a time-discrimination task, which asked participants to determine whether a comparison interval (1200 ± 0, 50, 100, 150, 200 ms) was shorter or longer than a standard interval (1200 ms); a retrospective time estimation task, which required participants to verbally estimate time intervals (10, 30, 60, 90 and 120 s) retrospectively; and a prospective time-production task, where participants were required to prospectively monitor the passing of time (10, 30, 60, 90 and 120 s). Working memory was assessed with the backwards digit span. On the discrimination task, there was a change in the proportion of long-to-short responses and reaction times in the dexamphetamine condition (but no association with working memory), consistent with an increase in the speed of an internal pacemaker, and an overestimation of durations in the timing of shorter intervals. There was an interaction between dexamphetamine, working memory, and performance on the estimation and production tasks, whereby increasing digit span scores were associated with decreasing interval estimates and increased produced intervals in the placebo condition, but were associated with increased interval estimates and decreased produced intervals after dexamphetamine administration. These findings indicate that the dexamphetamine-induced increase in the speed of the internal pacemaker was modulated by the basal working memory capacity of each participant. These findings in healthy humans have important implications for the role of dopamine, and its contributions to timing deficits, in models of psychiatric disorders.

Positive symptoms and time perception in schizophrenia: A meta-analysis

Positive symptoms of schizophrenia may be related to distortions in time perception. To examine this issue, we conducted a meta-analysis to determine whether positive symptoms are associated with deficits in time processing performance. MEDLINE and Web of Science were searched from January 1980 through March 2017, and all related articles and their references were scrutinized to find relevant studies. Studies were selected if they included participants with a diagnosis of schizophrenia, and reported data from behavioral measures of interval timing (e.g. duration discrimination and temporal order judgement). The results indicated that positive symptoms of schizophrenia are related with overestimation of interval timing (i.e., acceleration of the “internal clock”), and suggest that time perception may be associated with psychosis.

Delusions of control in schizophrenia: Resistant to the mind's best trick?

The existence of a free will is fiercely debated in neuroscience and philosophy. The debate has great impact on society and our self-understanding as human beings. Behavioral and electrophysiological data have challenged the intuitive assumption that human behavior is the result of conscious intentions. This notion has important implications for delusions of control in schizophrenia, where patients experience bodily movements as not being controlled by themselves. Current theories explain control delusions as a deficit to perceive certain aspects of motor control, but many findings are inconsistent with this idea. Here, an alternative view is proposed: Control delusions might be triggered by an even more veridical perception of the temporal order of intentions and actions. This hypothesis is supported by evidence that (a) conscious intentions in healthy subjects are often based on retrospective inferences, (b) temporal recalibrations of conscious percepts occur in healthy subjects and are disturbed in schizophrenia and (c) basic perceptual functions of schizophrenic patients are less influenced by expectations and therefore they can sometimes be closer to physical reality than those of healthy subjects.

Predictive timing disturbance is a precise marker of schizophrenia

Timing disturbances have being proposed as a key component of schizophrenia pathogenesis. However, the contribution of cognitive impairment to such disorders has not been clarified. Here, we investigated duration estimation and predictive timing in 30 patients with DSM-5 diagnosis of schizophrenia (SZ) compared to 30 healthy controls (HC). Duration estimation was examined in a temporal and colour discrimination task, fully controlled for working memory (WM) and attention requirements, and by more traditional temporal production and temporal bisection tasks. Predictive timing was measured in a temporal and spatial orienting of attention task. Expectations about stimulus onset (temporal condition) or location (spatial condition) were induced by valid and invalid symbolic cues. Results showed that discrimination of temporal and colour stimulus attributes was equally impaired in SZ. This, taken with the positive correlation between temporal bisection performance and neuropsychological measures of WM, indicates that duration estimation impairments in SZ are underpinned by WM dysfunction. Conversely, we found dissociation in temporal and spatial predictive ability in SZ. Unlike controls, patients were selectively unperturbed by events appearing at an unexpected moment in time, though were perturbed by targets appearing at an unexpected location. Moreover, patients were able to generate temporal expectations more implicitly, as their performance was influenced by the predictive nature of the flow of time itself. Our findings shed new light on the debate over the specificity of timing distortions in SZ, providing evidence that predictive timing is a precise marker of SZ, more sensitive than duration estimation, serving as a valid heuristic for studying the pathophysiology of the disorder.

Segregation of Brain Structural Networks Supports Spatio-Temporal Predictive Processing

The ability to generate probabilistic expectancies regarding when and where sensory stimuli will occur, is critical to derive timely and accurate inferences about updating contexts. However, the existence of specialized neural networks for inferring predictive relationships between events is still debated. Using graph theoretical analysis applied to structural connectivity data, we tested the extent of brain connectivity properties associated with spatio-temporal predictive performance across 29 healthy subjects. Participants detected visual targets appearing at one out of three locations after one out of three intervals; expectations about stimulus location (spatial condition) or onset (temporal condition) were induced by valid or invalid symbolic cues. Connectivity matrices and centrality/segregation measures, expressing the relative importance of, and the local interactions among specific cerebral areas respect to the behavior under investigation, were calculated from whole-brain tractography and cortico-subcortical parcellation. Results: Response preparedness to cued stimuli relied on different structural connectivity networks for the temporal and spatial domains. Significant covariance was observed between centrality measures of regions within a subcortical-fronto-parietal-occipital network -comprising the left putamen, the right caudate nucleus, the left frontal operculum, the right inferior parietal cortex, the right paracentral lobule and the right superior occipital cortex-, and the ability to respond after a short cue-target delay suggesting that the local connectedness of such nodes plays a central role when the source of temporal expectation is explicit. When the potential for functional segregation was tested, we found highly clustered structural connectivity across the right superior, the left middle inferior frontal gyrus and the left caudate nucleus as related to explicit temporal orienting. Conversely, when the interaction between explicit and implicit temporal orienting processes was considered at the long interval, we found that explicit processes were related to centrality measures of the bilateral inferior parietal lobule. Degree centrality of the same region in the left hemisphere covaried with behavioral measures indexing the process of attentional re-orienting. These results represent a crucial step forward the ordinary predictive processing description, as we identified the patterns of connectivity characterizing the brain organization associated with the ability to generate and update temporal expectancies in case of contextual violations.

Motor Synchronization in Patients With Schizophrenia: Preserved Time Representation With Abnormalities in Predictive Timing

Objective: Basic temporal dysfunctions have been described in patients with schizophrenia, which may impact their ability to connect and synchronize with the outer world. The present study was conducted with the aim to distinguish between interval timing and synchronization difficulties and more generally the spatial-temporal organization disturbances for voluntary actions. A new sensorimotor synchronization task was developed to test these abilities. Method: Twenty-four chronic schizophrenia patients matched with 27 controls performed a spatial-tapping task in which finger taps were to be produced in synchrony with a regular metronome to six visual targets presented around a virtual circle on a tactile screen. Isochronous (time intervals of 500 ms) and non-isochronous auditory sequences (alternated time intervals of 300/600 ms) were presented. The capacity to produce time intervals accurately versus the ability to synchronize own actions (tap) with external events (tone) were measured. Results: Patients with schizophrenia were able to produce the tapping patterns of both isochronous and non-isochronous auditory sequences as accurately as controls producing inter-response intervals close to the expected interval of 500 and 900 ms, respectively. However, the synchronization performances revealed significantly more positive asynchrony means (but similar variances) in the patient group than in the control group for both types of auditory sequences. Conclusion: The patterns of results suggest that patients with schizophrenia are able to perceive and produce both simple and complex sequences of time intervals but are impaired in the ability to synchronize their actions with external events. These findings suggest a specific deficit in predictive timing, which may be at the core of early symptoms previously described in schizophrenia.

Is Schizophrenia a Disorder of Consciousness? Experimental and Phenomenological Support for Anomalous Unconscious Processing

Decades ago, several authors have proposed that disorders in automatic processing lead to intrusive symptoms or abnormal contents in the consciousness of people with schizophrenia. However, since then, studies have mainly highlighted difficulties in patients' conscious experiencing and processing but rarely explored how unconscious and conscious mechanisms may interact in producing this experience. We report three lines of research, focusing on the processing of spatial frequencies, unpleasant information, and time-event structure that suggest that impairments occur at both the unconscious and conscious level. We argue that focusing on unconscious, physiological and automatic processing of information in patients, while contrasting that processing with conscious processing, is a first required step before understanding how distortions or other impairments emerge at the conscious level. We then indicate that the phenomenological tradition of psychiatry supports a similar claim and provides a theoretical framework helping to understand the relationship between the impairments and clinical symptoms. We base our argument on the presence of disorders in the minimal self in patients with schizophrenia. The minimal self is tacit and non-verbal and refers to the sense of bodily presence. We argue this sense is shaped by unconscious processes, whose alteration may thus affect the feeling of being a unique individual. This justifies a focus on unconscious mechanisms and a distinction from those associated with consciousness.