Slower perception of time in depressed and suicidal patients

Exploring the multifaceted potential of (R)-ketamine beyond antidepressant applications

(R, S)- and (S)-ketamine have made significant progress in the treatment of treatment-resistant depression (TRD) and have become a research focus in recent years. However, they both have risks of psychomimetic effects, dissociative effects, and abuse liability, which limit their clinical use. Recent preclinical and clinical studies have shown that (R)-ketamine has a more efficient and lasting antidepressant effect with fewer side effects compared to (R, S)- and (S)-ketamine. However, a recent small-sample randomized controlled trial found that although (R)-ketamine has a lower incidence of adverse reactions in adult TRD treatment, its antidepressant efficacy is not superior to the placebo group, indicating its antidepressant advantage still needs further verification and clarification. Moreover, an increasing body of research suggests that (R)-ketamine might also have significant applications in the prevention and treatment of medical fields or diseases such as cognitive disorders, perioperative anesthesia, ischemic stroke, Parkinson's disease, multiple sclerosis, osteoporosis, substance use disorders, inflammatory diseases, COVID-19, and organophosphate poisoning. This article briefly reviews the mechanism of action and research on antidepressants related to (R)-ketamine, fully revealing its application potential and development prospects, and providing some references and assistance for subsequent expanded research.

Reduced attentional control in individuals with a history of suicide attempts compared to those with suicidal ideation: Results from a systematic review and meta-analysis

BACKGROUND

Neurocognitive profiles may be especially useful to identify factors that facilitate transitioning from contemplating suicide to attempting suicide. Generally, those who attempt suicide show greater disruptions in neurocognitive ability compared to those who think about suicide but do not proceed to attempt. The goal of this systematic review and meta-analysis is to test whether this pattern is observed with attentional control.

METHODS

We systematically searched PubMed, PsychINFO, CINAHL, and Google Scholar to find pertinent studies. All included studies compared attentional functioning using neutral stimuli. Each sample featured adults with a history of suicidal ideation (SI) and no history of suicide attempts (SA) compared to those with a history of SA.

RESULTS

We identified 15 studies with 32 effect sizes (N = 931; n = 506 with SI only; n = 425 with SA). SA groups, compared to SI groups, exhibited worse accuracy yet similar reaction time, suggesting a comparatively blunted speed-accuracy tradeoff. Relative to SI, SA groups performed worse on Stroop-like and Go/NoGo tasks. SA performed better than SI on Trail Making Test B, but not A.

LIMITATIONS

There were few available studies. Most samples were small. We did not differentiate current vs. past SI or high vs. low lethality SA. Only English and Spanish language articles were included.

CONCLUSIONS

Disrupted attentional control may convey risk for transitioning to SA from SI. More work is needed to determine which components of attention are most associated with suicide risk.

Acute but not long-lasting antidepressant-like effect of psilocybin in differential reinforcement of low-rate 72 schedule in rats

BACKGROUND

In clinical studies, psychedelics including psilocybin and D-lysergic acid diethylamide (LSD) demonstrate rapid and persistent antidepressant effects. Since the effective treatment with psychedelics is usually provided with psychotherapy, it is debatable whether their prolonged efficacy can be observed in infrahuman species. Preclinical reports on psychedelics' effects most often address their acute actions, and different tests and models provide inconsistent results. The goal of this study was to examine whether the treatment with psilocybin and/or LSD would demonstrate immediate and/or sustained antidepressant-like effects in the differential reinforcement of low-rate responding (DRL) schedule in rats. In contrast to the antidepressant screening tools, the DRL 72s test is known to detect antidepressants with high predictive validity as it differentiates clinically effective antidepressants from other psychoactive drugs in non-stressed animals.

METHODS

Adult male Sprague Dawley rats were injected over three consecutive days with psilocybin (1 mg/kg), LSD (0.08 mg/kg), or saline and then tested in DRL 72s for the following 4 weeks.

RESULTS

Treatment with psilocybin but not LSD demonstrated an immediate antidepressant-like effect, manifested as an increased number of reinforced presses and response efficiency. By contrast, neither of the drugs showed a long-term (up to 4 weeks following administration) antidepressant-like effect.

CONCLUSIONS

Using DRL 72s schedule of reinforcement, we demonstrated the acute antidepressant-like effect of psilocybin but not of LSD, and failed to detect their persistent antidepressant-like efficacy. The present study suggests that the detection of long-lasting antidepressant-like activity in rats could be challenging and may require entirely novel behavioral methods.

Time processing in neurological and psychiatric conditions

A central question in understanding cognition and pathology-related cognitive changes is how we process time. However, time processing difficulties across several neurological and psychiatric conditions remain seldom investigated. The aim of this review is to develop a unifying taxonomy of time processing, and a neuropsychological perspective on temporal difficulties. Four main temporal judgments are discussed: duration processing, simultaneity and synchrony, passage of time, and mental time travel. We present an integrated theoretical framework of timing difficulties across psychiatric and neurological conditions based on selected patient populations. This framework provides new mechanistic insights on both (a) the processes involved in each temporal judgement, and (b) temporal difficulties across pathologies. By identifying underlying transdiagnostic time-processing mechanisms, this framework opens fruitful avenues for future research.

The effect of 24-hour sleep deprivation on subjective time perception

In this study, we investigated the effect of 24-h total sleep deprivation on subjective time perception. Twenty-five participants aged 18-35 years (13 female and 12 male) were recruited. Time perception and cognitive assessments were performed twice: after a regular night's sleep and following a 24-h sleep deprivation. The retrospective and prospective tasks were used to measure time perception. In order to prevent order effect, the test orders were randomized. The Stroop test and the Wechsler Memory Scale-III were used to evaluate attention, processing speed, and memory. The repeated measures ANOVA was used to examine gender-by-sleep deprivation interactions on time perception. We found that retrospective time perception was significantly prolonged after sleep deprivation (p < 0.05). Women had a shorter prospective time estimation rate after adequate sleep than men, but this difference disappeared after sleep deprivation. The Stroop test showed improvement in cognitive flexibility after sleep deprivation (p < 0.05), and short-term or working memory appeared unaffected by one night of sleep deprivation. There was a negative correlation between sleepiness rate and working memory function in female subgroup. The results suggest that even short-term sleep deprivation can significantly affect time perception, which may have important implications in critical situations.

Characteristics of psychological time in patients with depression and potential intervention strategies

Psychological time reveals information about an individual's psychological state and psychopathological traits and, thus, has become a new perspective through which the occurrence and development of depression can be examined. Psychological time includes time perception, time perspective, circadian rhythms, and passage of time. Patients with depression are characterized by inaccurate time interval estimation, habitual negative thoughts about the past and future, evening-type circadian rhythms, and slow passage of time. Habitual negative thoughts about the past and future and evening-type circadian rhythms influence the formation of depression, and poor time interval estimation and slow passage of time may result from depression. Further study is needed accurately exploring psychological time and influencing factors in patients with depression, and prospective cohort studies could further clarify this complex relationship. In addition, the study of psychological time has important implications for developing effective interventions to reduce depression.

Low global frontal brain activity is associated with non-planned or impulsive suicide attempts. A preliminary study

BACKGROUND

Suicide prevention is limited by the frequent non-planned or impulsive nature of suicidal behavior. For instance, 25-62 % of suicide attempts, occur within 30 min of the onset of suicidal ideation. We aimed to examine frontal brain activity in depressed patients following a suicide attempt and its relationship with the duration of the suicidal process.

METHODS

We recruited 35 adult patients within three days of a suicide attempt of at least moderate lethality. Duration of the suicidal process was recorded in a semi-structured interview, including suicide contemplation (time from onset of suicidal ideation to decision to kill oneself) and suicide action intervals (time from the decision to kill oneself to suicide attempt). Resting state EEG data from AF7, AF8, TP9 and TP10 leads was collected with a portable MUSE 2 headband system. The average frequency values throughout a 5-minute portable EEG recording were extracted for delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) waves.

RESULTS

Delta (r = 0.450, p = 0.021) and theta power (r = 0.395, p = 0.044) were positively correlated with the duration of the suicide action interval. There were no significant correlations of the suicide contemplation interval with clinical or EEG measures. Patients with suicide action interval shorter than 30 min showed lower delta power (U = 113, p = 0.049) compared with those with longer duration.

CONCLUSIONS

Lower theta and delta activity may reflect hindered cognitive control and inhibition in impulsive suicide attempters. Portable EEG may provide a valuable tool for clinical research and in the management of acutely suicidal patients.

Effects of ketamine optical isomers, fluoxetine and naloxone on timing in differential reinforcement of low-rate response (DRL) 72-s task in rats

(S)-ketamine-induced rapid-acting antidepressant effects have revolutionized the pharmacotherapy of major depression; however, this medication also produces psychotomimetic effects such as timing distortion. While (R)-ketamine produces fewer dissociative effects, its antidepressant actions are less studied. Depression is associated with time overestimation (i.e., subjectively, time passes slowly). Our recent report suggests that while (S)-ketamine induces an opposite effect, i.e., time underestimation, the (R)-isomer does not affect timing. It has been suggested that opioid receptors are involved in the antidepressant effect of ketamine. In the present study we tested (R)- and (S)-ketamine, and fluoxetine as a positive control in the differential-reinforcement-of-low-rate (DRL) 72-s schedule of reinforcement in male rats following naloxone pretreatment. DRL classic metrics as well as peak deviation analyses served to determine antidepressant-like actions and those associated with timing. We report antidepressant-like effects of (S)-ketamine (30-60 mg/kg) that resemble fluoxetine's (2.5-10 mg/kg), as both compounds increased reinforcement rate and peak location (suggesting increased performance), reduced premature responses (suggesting time underestimation) and decreased Weber's fraction (suggesting increased timing precision). (R)-ketamine (30, but not 60 mg/kg) increased only the reinforcement rate and peak location but did not affect timing. Only fluoxetine decreased burst responses, suggesting decreased impulsivity. Naloxone pretreatment did not block ketamine enantiomers' actions, but unexpectedly, increased fluoxetine' performance. Thus, while all three medications produced antidepressant-like effects in DRL 72-s, fluoxetine- and (S)- but not (R)- ketamine-induced time underestimation (the subject experiences the time as passing quickly). The potentiation of DRL performance of fluoxetine by naloxone was unexpected and warrants clinical studies.

Temporal judgments of actions following unilateral brain damage

Sense of time is a complex construct, and its neural correlates remain to date in most part unknown. To complicate the frame, physical attributes of the stimulus, such as its intensity or movement, influence temporal perception. Although previous studies have shown that time perception can be compromised after a brain lesion, the evidence on the role of the left and right hemispheres are meager. In two experiments, the study explores the ability of temporal estimation of multi-second actions and non-biological movements in 33 patients suffering from unilateral brain lesion. Furthermore, the modulatory role of induced embodiment processes is investigated. The results reveal a joint contribution of the two hemispheres depending not only on different durations but also on the presence of actions. Indeed, the left hemisphere damaged patients find it difficult to estimate 4500 ms or longer durations, while the right hemisphere damaged patients fail in 3000 ms durations. Furthermore, the former fail when a biological action is shown, while the latter fail in non-biological movement. Embodiment processes have a modulatory effect only after right hemisphere lesions. Among neuropsychological variables, only spatial neglect influences estimation of non-biological movement.

The effect of social exclusion on intertemporal choice in suicide attempters: A preliminary experimental study

BACKGROUND

Suicide-related theories and a growing body of evidence suggest that suicidal patients may have a tendency toward "short-sightedness"-the preference for immediate gratification when making intertemporal choice-and that social exclusion may exacerbate this tendency in suicidal patients. The present study examined the intertemporal choice performance of suicide attempters under conditions of social exclusion in a sample of affective disorder patients.

METHODS

A total of 64 affective disorder patients (22 non-suicidal patients, 24 single-suicide attempters and 18 multiple-suicide attempters) completed an intertemporal choice task in an exclusion or a non-exclusion condition. Social exclusion was manipulated using the Cyberball paradigm.

RESULTS

Non-suicidal patients and single-suicide attempters both exhibited an exaggerated preference for immediate rewards in the exclusion condition compared with the non-exclusion condition; in contrast, the multiple-suicide attempters appeared relatively indifferent to the social exclusion, exhibiting virtually identical preferences for immediate rewards in both the exclusion and non-exclusion conditions. In addition, the multiple-suicide attempters exhibited an exaggerated preference for immediate rewards compared with non-suicidal patients and single-suicide attempters in the non-exclusion condition, while the three groups did not differ in the exclusion condition.

CONCLUSIONS

Affective disorder patients with a single or no suicide attempts are more short-sighted after being excluded, while those with multiple suicide attempts appeared consistent short-sightedness in both exclusion and non-exclusion conditions. The study provides preliminary evidence of the role of disadvantageous intertemporal choice in the suicidal process. Future research replicate and extend these findings could have implications for suicide prevention and intervention.

Time perception at resting state and during active motion: The role of anxiety and depression

BACKGROUND

Time perception and motion intensity are interrelated factors that may influence symptom expression and severity in case of various psychiatric conditions, including anxiety and depression.

AIMS

The present study aimed to 1) explore the associations between the intensity of physical activity, time perception, impulsivity, anxiety and depressive symptoms, and to 2) investigate the extent to which resting state motion intensity can be used to identify the assessed psychiatric conditions.

METHODS

20 healthy controls and 20 psychiatric patients (with either anxiety or depression-related diagnoses) were included in the study and filled out a questionnaire consisting of validated anxiety, depression and impulsivity measures. Time perception was measured by a computerized time production task, whereas motion intensity was analyzed by a motion capture and analysis software. Respondents were randomly assigned to an experimental (with active motion task) and non-experimental group (resting state conditions). Both subgroups were repeatedly assessed, in order to explore changes in motion intensity, time perception and psychiatric symptom levels.

RESULTS

Random forest regression analysis identified the level of impulsivity, depression and anxiety as the strongest predictors of resting state motion intensity, while a path analysis model indicated that controls and psychiatric patients show different pathways regarding the connection between motion intensity changes, time production ratio alterations and symptom reduction.

CONCLUSIONS

Our study implies the importance of distinguishing between clinical and subclinical severity of psychiatric symptoms when considering the association between motion intensity, time perception, anxiety and depression. Potential transdiagnostic relevance of resting state motion intensity is also addressed.

Time perception changes in stroke patients: A systematic literature review

Introduction

Time perception comprises the subjective experience of passing of time and of the duration of an event. Although already described in some neurological and psychiatric conditions, there is a paucity of details regarding this neurocognitive change in stroke patients. We aimed to describe time perception dysfunction in stroke patient.

Methods

We performed a systematic review of the literature in Pubmed, PsycInfo and EMBASE including manuscripts from their inception until December 2020. We collected data regarding the type of time perception that was detected, type of stroke, most common location of lesions, evaluation tests that were used and time of evaluation after stroke onset.

Results

A total of 27 manuscripts were selected, concerning a total of 418 patients (n = 253 male; 60.5%). Most manuscripts (n = 21) evaluated patients with ischaemic lesions (n = 407; 97.4%). The majority referred to evaluations between 2 months and seven years after stroke. Underestimation in temporal evaluation in sub- and supra-second was the most common dysfunction (n = 165; 41.7%). Overestimation of time (n = 116; 27.8%) and impaired time interval comparison (n = 88; 22.2%) were also found. Most patients had right hemisphere lesions (n = 219 patients; 52.4%). Common reported lesion locations included the thalamus, insula, basal ganglia, dorsolateral prefrontal cortex, parietal cortex including supramarginal, angular gyrus and right inferior parietal cortex and cerebellum.

Conclusion

There are multiple stroke locations associated with time perception dysfunction, which highlights the complex system involved in time perception. There is still scarce knowledge about specific time perception deficits after stroke. Most studies rely in psychometric analysis without clear clinical and functional translation, namely regarding impact on daily activities.

Synergistic effect of chronic pain and nonsuicidal self-harm on pain sensitivity

Abnormalities in pain processing have been observed in patients with chronic pain conditions and in individuals who engage in self-harm, specifically nonsuicidal self-injurious behaviors (NSSI). Both increased and decreased pain sensitivity have been described in chronic pain patients, while decreased pain sensitivity is consistently observed in individuals with NSSI. The objective of the study was to identify the differential effects of chronic pain and NSSI on experimental pain sensitivity, specifically pressure pain threshold, in depressed patients. Moreover, the role that hopelessness may play between depression severity and pain sensitivity was also examined. Depressed patients with and without chronic pain, and with and without lifetime self-harm behaviors were analyzed into four groups. Group 1 (N = 42) included depressed patients with both Chronic pain ( +) and Self-harm ( +), Group 2 (N = 53) included depressed patients with Chronic pain ( +) but no Self-harm (-), Group 3 (N = 64) included depressed patients without Chronic pain (-), but Self-harm ( +), and Group 4 (N = 81) included depressed patients with neither Chronic pain (-) nor Self-harm (-). Healthy controls (N = 45) were also recruited from the community. Depressed patients with both Chronic pain ( +) and Self-harm ( +) reported higher pressure pain threshold measures when compared with the other groups. Mediation analysis indicated that hopelessness mediates the relationship between depression severity and pressure pain threshold. Our findings suggest that a multiprong approach including adequate mental health services and pain control for depressed patients with comorbid chronic pain and nonsuicidal self-harm is needed to yield effective outcomes.

Effects of ketamine optical isomers, psilocybin, psilocin and norpsilocin on time estimation and cognition in rats

RATIONALE

Ketamine and psilocybin belong to the rapid-acting antidepressants but they also produce psychotomimetic effects including timing distortion. It is currently debatable whether these are essential for their therapeutic actions. As depressed patients report that the "time is dragging," we hypothesized that ketamine and psilocybin-like compounds may produce an opposite effect, i.e., time underestimation, purportedly contributing to their therapeutic properties.

OBJECTIVES

Timing was tested following administration of (R)- and (S)-ketamine, and psilocybin, psilocin, and norpsilocin in the discrete-trial temporal discrimination task (TDT) in male rats. Timing related to premature responses, and cognitive and unspecific effects of compounds were tested in the 5-choice serial reaction time task (5-CSRTT) in the standard 1-s, and "easier" 2-s stimulus duration conditions, as well as in the vITI variant promoting impulsive responses.

RESULTS

(S)-ketamine (15 but not 3.75 or 7.5 mg/kg) shifted psychometric curve to the right in TDT and reduced premature responses in 5-CSRTT, suggesting expected time underestimation, but it also decreased the accuracy of temporal discrimination and increased response and reward latencies, decreased correct responses, and increased incorrect responses. While (R)-ketamine did not affect timing and produced no unspecific actions, it reduced incorrect responses in TDT and increased accuracy in 5-CSRTT, suggesting pro-cognitive effects. Psilocin and psilocybin produced mainly unspecific effects in both tasks, while norpsilocin showed no effects.

CONCLUSIONS

Time underestimation produced by (S)-ketamine could be associated with its antidepressant effects; however, it was accompanied with severe behavioral disruption. We also hypothesize that behavioral disruption produced by psychedelics objectively reflects their psychotomimetic-like actions.