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Abnormally widened spatial and temporal binding windows (SBW/TBWs; length of space/time whereby stimuli are considered part of the same percept) are observed in schizophrenia. TBW alterations have been associated with altered sense of agency (hereafter referred to as agency), and an associative relationship between embodiment (body ownership) and agency has been proposed. SBWs/TBWs are investigated separately, but no evidence exists of these being separate in mechanism, system or function. The underlying neural substrate of schizophrenia remains unclear. The literature claims either pro-psychotic or anti-psychotic effects of Δ9-Tetrahydrocannabinol (THC) in patients and healthy individuals, but major support for cannabis in the aetiology of schizophrenia is associative, not causal. To clarify if THC is pro- or anti-psychotic, this single-blind, placebo-controlled within-subjects cross-over study tested several hypotheses. 1) Competing hypotheses that a synthetic THC analogue, Nabilone (NAB, 1-2 mg), would alter measures of agency and embodiment in healthy volunteers (n = 32) similarly, or opposite, to that of in patients with schizophrenia. 2) That there would be significant associations between any NAB-induced alterations in individual agency and embodiment measures in the Projected Hand Illusion (PHI). 3) That there is a unitary spatio-temporal binding window (STBW). A large proportion of individuals did not experience the PHI. Multimodal and bi-directional effects of NAB on the PHI were observed. Evidence of a unitary spatio-temporal binding window (STBW) was observed. NAB widened the STBW in some but narrowed it in others as a function of space and delay. No associations were found between agency and embodiment., Competing Interests: No authors have competing interests., (Copyright: © 2024 Lim et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objectives: Stimuli that are separated by a short window of space or time, known as spatial and temporal binding windows (SBW/TBWs), may be perceived as separate. Widened TBWs are evidenced in schizophrenia, although it is unclear if the SBW is similarly affected. The current study aimed to assess if dexamphetamine (DEX) may increase SBWs in a multimodal visuo-tactile illusion, potentially validating usefulness as an experimental model for multimodal visuo-tactile hallucinations in schizophrenia, and to examine a possible association between altered binding windows (BWs) and working memory (WM) suggested by previous research., Methods: A placebo-controlled, double-blinded, and counter-balanced crossover design was employed. Permuted block randomisation was used for drug order. Healthy participants received DEX (0.45 mg/kg, PO, b.i.d.) or placebo (glucose powder) in capsules. The Rubber Hand Illusion (RHI) and Wechsler Adult Intelligence Scale Spatial Span was employed to determine whether DEX would alter SBWs and WM, respectively. Schizotypy was assessed with a variety of psychological scales., Results: Most participants did not experience the RHI even under normal circumstances. Bi-directional and multimodal effects of DEX on individual SBWs and schizotypy were observed, but not on WM., Conclusions: Bidirectional multimodal effects of DEX on the RHI and SBWs were observed in individuals, although not associated with alterations in WM., (© 2024 The Author(s). Human Psychopharmacology: Clinical and Experimental published by John Wiley & Sons Ltd.)

Psychotic symptoms and delusional beliefs have been linked to dopamine transmission in both healthy and clinical samples and are assumed to result at least in part from perceiving illusory patterns in noise. However, the existing literature on the role of dopamine in detecting patterns in noise is inconclusive. To address this issue, we assessed the effect of manipulating dopaminergic neurotransmission on illusory pattern perception in healthy individuals ( n  = 48, n  = 19 female) in a double-blind placebo-controlled within-subjects design (see preregistration at https://osf.io/a4k9j/). We predicted individuals on versus off ʟ-DOPA to be more likely to perceive illusory patterns, specifically objects in images containing only noise. Using a signal detection model, however, we found no credible evidence that ʟ-DOPA compared with placebo increased false alarm rates. Further, ʟ-DOPA did not reliably modulate measures of accuracy, discrimination sensitivity, and response bias. In all cases, Bayesian statistics revealed strong evidence in favor of the null hypothesis. The task design followed previous work on illusory pattern perception and comprised a limited number of items per condition. The results therefore need to be interpreted with caution, as power was limited. Future studies should address illusory pattern perception using more items and take into account potential dose-dependent effects and differential effects in healthy versus clinical samples., Competing Interests: The authors declare no competing financial interests., (Copyright © 2024 Smith et al.)

Objective: Stimuli received beyond a very short timeframe, known as temporal binding windows (TBWs), are perceived as separate events. In previous audio-visual multisensory integration (McGurk effect) studies, widening of TBWs has been observed in people with schizophrenia. The present study aimed to determine if dexamphetamine could increase TBWs in unimodal auditory and unimodal visual illusions that may have some validity as experimental models for auditory and visual hallucinations in psychotic disorders., Methods: A double-blind, placebo-controlled, counter-balanced crossover design with permuted block randomisation for drug order was followed. Dexamphetamine (0.45 mg/kg, PO, q.d.) was administered to healthy participants. Phantom word illusion (speech illusion) and visual-induced flash illusion/VIFI (visual illusion) tests were measured to determine if TBWs were altered as a function of delay between stimuli presentations. Word emotional content for phantom word illusions was also analysed., Results: Dexamphetamine significantly increased the total number of phantom words/speech illusions (p < 0.01) for pooled 220-1100 ms ISIs in kernel density estimation and the number of positive valence words heard (beta = 2.20, 95% CI [1.86, 2.55], t = 12.46, p < 0.001) with a large effect size (std. beta = 1.05, 95% CI [0.89, 1.22]) relative to placebo without affecting the TBWs. For the VIFI test, kernel density estimation for pooled 0-801 ms ISIs showed a significant difference (p < 0.01) in the data distributions of number of target flash (es) perceived by participants after receiving dexamphetamine as compared with placebo., Conclusions: Overall, healthy participants who were administered dexamphetamine (0.45 mg/kg, PO, q.d.) experienced increases in auditory and visual illusions in both phantom word illusion and VIFI tests without affecting their TBWs., (© 2024 John Wiley & Sons Ltd.)

The Rubber Hand Illusion (RHI) is an experimental paradigm for assessing changes in body ownership. Recent findings in the field suggest that social emotions can influence such changes and that empathic motivation in particular appears to positively predict the malleability of body representations. Since the steroid hormone, testosterone, is well known to interrupt certain forms of empathic processing, in the current study we investigated whether 0.5 mg of testosterone affected ownership indices of the RHI. Forty-nine females participated in a double-blind, placebo-controlled experiment in which the RHI was induced. Compared to placebo, testosterone had no effects on the alteration of subjective ownership over the rubber limb or on subjective sense of proprioceptive drift. However, unlike the placebo group, testosterone-treated participants did not display an objective decline in the temperature of their own (hidden) hand following induction of the illusion. These findings suggest that testosterone strengthens implicit but not explicit bodily self-representations. We propose that effective maintenance of implicit body boundaries can be regarded, conceptually, as a primary defensive state facilitating integrity of the self.

Multisensory integration processes are fundamental to our sense of self as embodied beings. Bodily illusions, such as the rubber hand illusion (RHI) and the size-weight illusion (SWI), allow us to investigate how the brain resolves conflicting multisensory evidence during perceptual inference in relation to different facets of body representation. In the RHI, synchronous tactile stimulation of a participant's hidden hand and a visible rubber hand creates illusory body ownership; in the SWI, the perceived size of the body can modulate the estimated weight of external objects. According to Bayesian models, such illusions arise as an attempt to explain the causes of multisensory perception and may reflect the attenuation of somatosensory precision, which is required to resolve perceptual hypotheses about conflicting multisensory input. Recent hypotheses propose that the precision of sensorimotor representations is determined by modulators of synaptic gain, like dopamine, acetylcholine, and oxytocin. However, these neuromodulatory hypotheses have not been tested in the context of embodied multisensory integration. The present, double-blind, placebo-controlled, crossover study ( n = 41 healthy volunteers) aimed to investigate the effect of intranasal oxytocin (IN-OT) on multisensory integration processes, tested by means of the RHI and the SWI. Results showed that IN-OT enhanced the subjective feeling of ownership in the RHI, only when synchronous tactile stimulation was involved. Furthermore, IN-OT increased an embodied version of the SWI (quantified as estimation error during a weight estimation task). These findings suggest that oxytocin might modulate processes of visuotactile multisensory integration by increasing the precision of top-down signals against bottom-up sensory input.

Synthetic cannabinoid receptor agonists are a heterogeneous group of psychotropic drugs functionally related to Δ9-tetrahydrocannabinol. These substances, marketed as cannabis substitutes, have been associated with numerous cases of severe intoxication and death across the world. In our article, we describe a case of hallucinogen persisting perception disorder developing in a natural cannabis user after consumption of JWH-122, a naphthoylindole largely used since 2010. Clinical symptomatology persisted for about four years and was alleviated through treatment with clonazepam. Considering that natural cannabis consumption can induce the development of a hallucinogen persisting perception disorder, it is not excluded that, in our patient, symptoms lasted a long time due to cannabis consumption. This article describes the clinical evolution from onset to resolution of all symptoms.

The Müller-Lyer's illusion (MLI) is a visual illusion in which the presence of contextual cues (i.e., the orientation of arrowheads) changes the perception of the length of straight lines. An altered sensitivity to the MLI has been proposed as a marker for the progression of perceptual deficits in schizophrenia. Since dizocilpine (MK-801), a noncompetitive antagonist of the NMDA glutamate receptor, induces schizophrenic-like sensory impairments, it may have potential value for investigating the neurochemical basis of the perceptual changes in schizophrenia. Here we tested the effects of MK-801 on the perception of the MLI in a nonhuman primate. Five capuchin monkeys Sapajus spp. were trained on a MLI task using a touch screen monitor. After training, the Point of Subjective Equality (PSE; i.e., the minimum difference in length between two lines which the subject can distinguish) was determined for each subject. Then, during 12 consecutive days, we evaluated changes in PSE in response to vehicle, MK-801 (5.6μg/kg, i.m.) and a no-treatment protocol (post- test). Each of these was given as a single daily treatment, on four consecutive days. Results showed that MK-801 increased the monkeys' performance in the MLI task, suggesting that NMDA receptor modulation reduces sensitivity to this illusion, similar to prodromal stage in schizophrenia patients. The MLI protocol may thus be used in nonhuman primates to screen potential antipsychotic drugs for early stages of this disease., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: To report palinopsia as a possible side effect of topiramate., Methods: Case series and review of the literature., Results: Nine patients in our series, and 4 previously reported patients, who developed palinopsia while on topiramate, are reviewed. All patients were women, and comorbidities included migraine, idiopathic intracranial hypertension, and bulimia nervosa. Palinopsia resolved in 8 patients after stopping or decreasing the dose of topiramate. The lowest dose of topiramate causing palinopsia was 25 mg twice a day. More than half of our patients reported exacerbation of visual disturbance in early morning or late evening., Conclusions: Topiramate-induced palinopsia may be underdiagnosed because physicians do not inquire about such visual symptoms.

Rationale: Subanaesthetic ketamine infusion in healthy volunteers induces experiences redolent of early psychosis, including changes in the experience of one's own body. It is not clear, however, whether repeated self-administration of ketamine has a sustained effect on body representation that is comparable to that found during acute administration., Objectives: We sought to establish whether chronic ketamine use resulted in disturbances to sense of body ownership., Methods: Following on from our work on the effects of acute ketamine infusion, we used the rubber hand illusion (RHI) to experimentally manipulate the sense of body ownership in chronic ketamine users, compared to healthy controls., Results: Chronic ketamine users experienced the RHI more strongly and reported more body-image aberrations, even though they had not recently taken the drug., Conclusions: These findings suggest that the chronic ketamine model for psychosis models more long-lasting changes in sense of ownership, perhaps more akin to schizophrenia.

Background: Cataract patients observe structures, colors and movements during surgery. Is there any pattern to their visual experiences?, Methods: From 2005 to 2011 a total of 20,000 phacoemulsification procedures were performed using topical anesthesia. From these patients we received 45 pictures which had been painted to reflect intraoperative their visual impressions so that approximately 1 out of 500 of the patients painted a picture. A further 98 patients were questioned postoperatively about their intraoperative visual impressions and were shown the 45 pictures. They described their own visual experiences and any similarities with the 45 pictures were documented., Results: All patients were awake and cooperative during surgery. Afterwards they described their visual experiences whereby 36 patients saw mainly blue, 32 red/pink and 27 saw yellow colors. Out of the 45 pictures 30 (67%) were identified as being similar to their own visual images and 10 patients could not describe any postoperative visual phenomena., Conclusion: Patients notice optical phenomena during cataract surgery under topical anesthesia with eye drops. Visual images are often similar among patients. The surgeon can use this knowledge to explain these experiences while talking to the patient intraoperatively. This may reassure patients during surgery.

Palinopsia is an illusory visual phenomenon consisting in the persistence or recurrence of visual images after the exciting stimulus object has been removed. It has been reported in association with parietal and occipital lobe lesions, migraine auras, and related to the use of several drugs and illicit drugs. Here, we report the case of a 23-year-old woman with a 4-year history of episodic migraine with aura who developed palinopsia during sequential prophylactic therapies with topiramate and zonisamide. Although the exact physiopathology of this phenomenon remains unknown, topiramate- and zonisamide-induced palinopsia support an increase on serotonergic activity as a possible mechanism for this visual disorder.

We assessed changes in forward vection following alcohol consumption, and found that alcohol consumption enhanced vection. This result indicates that alcohol can affect psychophysical processes responsible for self-motion perception.

Clinical evidence suggests that after initiation of dopaminergic medications some patients with Parkinson's disease (PD) develop psychotic symptoms, such as hallucinations and delusions. Here, we tested the hypothesis that the neurocognitive basis of this phenomenon can be defined as the formation of arbitrary and illusory associations between conditioned stimuli and reward signals, called aberrant salience. Young, never-medicated PD patients and matched controls were assessed on a speeded reaction time task in which the probe stimulus was preceded by conditioned stimuli that could signal monetary reward by color or shape. The patients and controls were re-evaluated after 12 weeks during which the patients received a dopamine agonist (pramipexole or ropinirole). Results indicated that dopamine agonists increased both adaptive and aberrant salience in PD patients, that is, formation of real and illusory associations between conditioned stimuli and reward, respectively. This effect was present when associations were assessed by means of faster responding after conditioned stimuli signaling reward (implicit salience) and overt rating of stimulus-reward links (explicit salience). However, unusual feelings and experiences, which are subclinical manifestations of psychotic-like symptoms, were specifically related to irrelevant and illusory stimulus-reward associations (aberrant salience) in PD patients receiving dopamine agonists. The learning of relevant and real stimulus-reward associations (adaptive salience) was not related to unusual experiences. These results suggest that dopamine agonists may increase psychotic-like experiences in young patients with PD, possibly by facilitating dopaminergic transmission in the ventral striatum, which results in aberrant associations between conditioned stimuli and reward.

Introduction: Out-of-body experiences present a unique paradigm to investigate cognitive and neural mechanisms of bodily-self processes and their disorders. Previous work on out-of-body experiences associated with sleep paralysis supported a model in which illusory movement experiences reflect disrupted bodily-self integration generating anomalous vestibular and motor sensations. Further disintegration and progression of the experience may then give rise to out-of-body feelings, which in turn may instigate out-of-body autoscopy., Methods: The current study assesses the disintegration model through analyses of out-of-body experiences reports from an online survey of individuals reporting recreational ketamine use (n=128) and cross-validation in a sample of nonketamine polydrug users (n=64). Path analyses using intensity and frequency measures of anomalous experiences assess the fit of seven competing models., Results: The disintegration model (illusory movement → out-of-body feelings → out-of-body autoscopy) emerged as the best fitting model overall and results support full mediation of the relation between illusory movement experiences and out-of-body autoscopy by out-of-body feelings. Moreover, lifetime measures of ketamine use predicted the frequency of illusory movement experiences., Conclusions: The results corroborate this structural model of out-of-body phenomena and encourage a framework for future studies into aetiological mechanisms of out-of-body experiences to include neurochemical systems.

Rationale: Corporeal awareness is an integral component of self-consciousness and is distorted in several neurological and psychiatric disorders. Research regarding the neural underpinnings of corporeal awareness has made much progress recently using the rubber hand illusion (RHI) procedure. However, more studies are needed to investigate the possibility of several dissociable constructs related to the RHI specifically, and corporeal awareness generally., Objectives: Considering dopamine's involvement in many perceptual-motor learning processes, as well as its apparent relationship with disorders such as schizophrenia that are linked to body ownership disturbances, we gave 0.45 mg/kg dexamphetamine (a dopamine transporter reverser) to 20 healthy participants to examine the effects of increased dopamine transmission on the RHI., Methods: The effect of dexamphetamine on separate quantitative constructs underlying RHI were examined including embodiment of rubber hand, loss of ownership of real hand, perception of movement, affect, deafference, and proprioceptive drift. The experiment was a double-blind, placebo-controlled, cross-over design., Results: Dexamphetamine increased participants' ratings of embodiment (particularly "ownership") of the rubber hand and was associated with the experience of loss of ownership of the person's real hand. There were significant increases from asynchronous to synchronous stroking for the measures of movement and proprioceptive drift after placebo but not dexamphetamine. There were no changes in the measures of other constructs., Conclusions: These results show a novel pharmacological manipulation of separate constructs of the RHI. This finding may aid in our understanding of disorders that have overlapping disturbances in both dopamine activity and body representations, particularly schizophrenia.

Background: Our sense of body ownership is profound and familiar, yet it may be misleading. In the rubber-hand illusion, synchronous tactile and visual stimulation lead to the experience that a rubber hand is actually one's own. This illusion is stronger in schizophrenia. Given the evidence that ketamine, a noncompetitive N-methyl-D-aspartate antagonist reproduces symptoms of schizophrenia, we sought to determine whether the rubber-hand illusion is augmented by ketamine., Methods: We studied 15 healthy volunteers in a within-subjects placebo-controlled study. All volunteers carried out two versions of the rubber-hand task, each under both placebo and ketamine infusions. In one task, they saw a rubber hand being stroked in synchrony with tactile stimulation of their real, hidden hand. In the other, stroking of the real and rubber hands was asynchronous. We recorded subjective changes in sense of ownership, as well as participants' ability to localize their hidden hand., Results: Ketamine was associated with significant increases in subjective measures of the illusion and in hand mislocalization. Although asynchronous visuotactile stimulation attenuates the strength of the illusion during both placebo and ketamine, there remained a significant illusory effect during asynchronous visuotactile stimulation under ketamine compared with placebo. The strength of the illusion during asynchronous visuotactile stimulation correlated with other subjective effects of the drug., Conclusions: Ketamine mimics the perturbed sense of body ownership seen in schizophrenia, suggesting that it produces a comparable alteration in integration of information across sensory domains and in the subjective and behavioral consequences of such integration., (Copyright © 2011 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Background: Perceptual illusions described in healthy subjects undergoing regional anesthesia (RA) are probably related to short-term plastic brain changes. We addressed whether performance on an implicit mental rotation task reflects these RA-induced changes in body schema brain representations. Studying these changes in healthy volunteers may shed light on normal function and the central mechanisms of pain., Methods: Performance pattern was studied in upper limb-anesthetized subjects on a left/right hand judgment task, which is known to involve motor imagery processes relating to hand posture. Three conditions were used: control (i.e., absence of deafferentation), RA (i.e., deafferentation), and vision (i.e., deafferentated limb exposed to view). To limit potential bias such as order effect, the control state was recorded in a randomized manner., Results: All subjects described perceptual illusions of their anesthetized limb. They were slower and less accurate on the task during RA compared with control. Response patterns were similar in all conditions, suggesting sensitivity of performance to arm/hand biomechanical constraints. Vision was associated with an increase in the proportion of correct responses and a reduction of the response times in hand judgment and was accompanied by disappearance of the lateralization of the underlying mental representations, which was identified during RA., Conclusions: These results suggest the following: (1) the right/left judgment task involves mental simulation of hand movements, (2) underlying mental representations and their neural substrates are subject to acute alterations after RA, and (3) the proprioceptive deficit induced by RA is influenced by the subject's ability to see the anesthetized limb.

We compared the effects of systemic morphine on normal (heat and cold) pain and paradoxical burning pain evoked by the simultaneous application of innocuous warm and cold stimuli to the skin. Twelve healthy volunteers participated in a randomised, double-blind, cross-over study to compare the effects of intravenous administration of morphine (0.025 or 0.1mg/kg) or placebo (saline). Stimuli were applied to the palm of the right hand with a thermode ("thermal grill") composed of six bars, whose temperatures were controlled by Peltier elements. For each session, we measured the heat and cold pain thresholds and then successively measured the intensity of: (i) paradoxical pain evoked by a combination of non-noxious warm and cold stimuli; (ii) "normal" pain evoked by suprathreshold heat or cold stimuli; (iii) non-painful sensations evoked by warm or cold stimuli at temperatures used to produce paradoxical pain. Measurements were performed before 20min after the administration of morphine or placebo and 5min after the administration of the morphine antagonist, naloxone. The administration of 0.1mg/kg of morphine, but not 0.025mg/kg, induced a significant and naloxone-reversible reduction of paradoxical pain intensity, which was directly correlated with the reduction of normal cold pain. No differences were observed for non-painful thermal sensations. The paradoxical burning pain evoked by a thermal grill can be modified pharmacologically by analgesics and share some mechanisms with normal pain. This unique experimental "illusion of pain" may represent a new model to test analgesics in healthy volunteers.

We investigated the role of the glutamatergic and endogenous opioidergic systems in the paradoxical pain evoked by the simultaneous application of innocuous warm and cold stimuli to the skin with a "thermal grill". Two parallel randomized, double-blind, cross-over studies, including two groups of 12 healthy volunteers, were carried out to compare the effects of i.v. ketamine or naloxone to those of placebo, on the sensations produced by a thermode (i.e. thermal grill) composed of six bars applied on the palmar surface of the right hand. The temperature of alternate (even- and odd-numbered) bars could be controlled independently by Peltier elements to produce various patterns of the grill. During each experimental session we measured the effects of ketamine, naloxone or placebo on the intensity of: (i) paradoxical pain; (ii) "normal" thermal (heat and cold) pain; and (iii) non-painful thermal (warm and cool) sensations. Ketamine administration resulted in a significant reduction of paradoxical pain intensity but did not alter normal pain or non-painful thermal sensations. By contrast, naloxone had no effect on paradoxical pain, normal pain or non-painful thermal sensations. This study demonstrates for the first time that the "thermal grill illusion of pain" can be modulated pharmacologically. This paradoxical pain, which involves the glutamatergic systems, acting through the NMDA receptors, but not the tonic endogenous opioids systems, might share some mechanisms with pathological pain.

Background: Sympathomimetic-induced metabolic derangements within the central nervous system can result in conspicuous changes in neurological functioning and corresponding radiographic abnormalities that can be reversible., Objective: To describe a patient with a "kaleidoscopic" visual illusion who was found by magnetic resonance imaging to have a transient lesion in the splenium of the corpus callosum., Design: Case report., Setting: The University of Texas Southwestern Medical Center, Dallas., Patient: A 17-year-old adolescent girl who developed an episode of kaleidoscopic vision while using sympathomimetic-containing diet pills that was associated with a reversible lesion of the splenium of the corpus callosum. Her brother has a history of migraine and experienced a similar episode while using illicit stimulant agents., Intervention: Withdrawal of the medication resulted in the cessation of the episodes and normalization of the magnetic resonance image., Main Outcome Measures: Clinical and radiographic improvement., Results: Sympathomimetic-induced metabolic derangements can be associated with reversible lesions within the brain., Conclusions: We hypothesize that the visual fragmentation was a manifestation of a migraine triggered by sympathomimetic-containing diet pills, and that the transient lesion in the corpus callosum was a manifestation of a reversible metabolic derangement. Both the visual fragmentation and the lesion in the corpus callosum resolved once the patient stopped receiving diet pills.

The present study investigated the role of central mitogen-activated protein kinases (MAPKs) in interleukin-1beta (IL-1beta)-induced mirror-image mechanical allodynia in the orofacial area. Experiments were carried out on Sprague-Dawley rats. Under pentobarbital sodium anesthesia, a polyethylene tube was implanted in the subcutaneous area of one vibrissa pad, which enabled us to inject IL-1beta. For an intracisternal injection, each anesthetized rat was mounted on a stereotaxic frame and a polyethylene tube was implanted. Animals were given a recovery time of at least 72 h from surgery. After a subcutaneous administration of 0.01, 0.1, 1, or 10 pg of IL-1beta, we examined the face withdrawal behavioral responses produced by 10 successive trials of air puffs ipsilateral or contralateral to the IL-1beta injection site. Normal animals did not respond to pressure less than 40 psi. The thresholds of air puffs ipsilateral and contralateral to the IL-1beta injection site were significantly lower in the IL-1beta-treated group, compared with the vehicle-treated group. The decrease in the threshold of air puffs appeared 10 min after an IL-1beta injection and persisted for over 3h. Intracisternal pretreatment with PD98059, a p44/42 MAPK inhibitor, or SB203580, a p38 MAPK inhibitor, significantly reduced the decrease in the threshold of air puffs ipsilateral to the IL-1beta injection site produced by 10 pg of IL-1beta. IL-1beta-induced mirror-image mechanical allodynia was also reduced significantly by intracisternal pretreatment with both PD98059 and SB203580. These results indicate that central MAPK pathways mediate IL-1beta-induced mirror-image mechanical allodynia in the orofacial area.

Background: Sensory assessment to estimate spread and effectiveness of a peripheral nerve block is difficult because no clinical test is specific for small sensory fibers. Occurrence of a swelling illusion (SI) during a peripheral nerve block corresponds to the impairment of small sensory fibers. The authors investigated the usefulness of SI in predicting successful peripheral nerve block by assessing the temporospatial correlation between progression of sensory impairment in cutaneous distributions anesthetized and localization of SI during peripheral nerve block installation., Methods: Interscalene, infracoracoid, or sciatic nerve blocks were performed using a nerve stimulator and 1.5% mepivacaine in 53 patients, with a total of 201 nerves to be anesthetized. Pinprick, cold, warm, touch, and proprioception were assessed every 3 min, while patients were asked to describe their perception of size and shape of their anesthetized limb and localization of these illusions. Data are presented as mean +/- SD and percentage (95% confidence interval)., Results: Failure occurred in 12 cutaneous distributions out of a total of 201 theoretically blocked nerves. SI appeared earlier than warmth impairment (4.3 +/- 2.7 vs. 6.2 +/- 2.0 min; P < 0.05), always corresponding to successfully anesthetized cutaneous distributions, with the exception of 1 patient, who developed SI in 2 cutaneous distributions while sensory testing indicated failure in 1 distribution. SI successfully predicted the blockade of a cutaneous distribution with a sensitivity of 1.00 (0.98-1.00), a specificity of 0.92 (0.65-0.99), and an accuracy of 0.99 (0.97-1.00)., Conclusions: Swelling illusion may provide an early assessment of the success of a peripheral nerve block in unsedated patients.

Rationale: When asked "How many animals of each kind did Moses take on the ark?", people fail to notice the distortion introduced by the impostor "Moses" and respond "two". It has been argued that the effect must be due to the existence of a partial-match process. In most situations, the form of a question is not likely to closely match the memory representation it queries. Thus, for the partial match hypothesis people ignore some semantic distortions. In the same vein, it has been shown that the benzodiazepine lorazepam drug induces some impairments of semantic memory as participants under lorazepam provide more incorrect recalls than placebo do with general information questions., Objectives: The aim of this study was to investigate the effects of the benzodiazepine lorazepam on the Moses illusion paradigm., Method: The effects of lorazepam (0.038 mg/kg) and of a placebo were investigated in 28 healthy volunteers. Twenty-two illusory questions were presented along with 72 normal general information questions., Results: Lorazepam impaired the ability to detect the Moses illusion. Moreover, lorazepam participants appeared less biased to consider a question distorted than placebo participants., Conclusions: The temporary and reversible semantic memory impairments experienced by participants when falling into the Moses illusion are more frequent under lorazepam. The amnesic drug lorazepam may impair semantic processing as well as the strategic control of memory.

Background: Previous reports document visual illusions resembling hallucinogen persisting perception disorder (HPPD) after risperidone treatment in patients with histories of previous LSD exposure., Methods: We report a case with visual disturbances resembling HPPD after each of three consecutive risperidone dose increases., Results: Contrasting with previous reports, our patient lacked any history of substance abuse, particularly hallucinogen exposure. She lacked neurologic or other contributory illnesses. Illusions generally remitted within 48 hours each time. Coadministration of trazodone and clonazepam may have contributed to these phenomena, although clonazepam has been used to treat this condition. She had been unusually sensitive to the side-effects of many psychotropics., Conclusions: This case is unique due to the absence of substance abuse. This and another report note heightened sensitivity to medication side-effects. Visual phenomena resembling HPPD evidently can occur with risperidone and, possibly, other atypical antipsychotics and certain antidepressants regardless of previous hallucinogen use. Several lines of evidence implicate reduced 5HT2a serotonin receptor stimulation rather than increased 5HT2c stimulation.

The aim of the present study was to investigate the effects of scopolamine (1.5 mg, transdermal patch) and cyclizine (50 mg tablet), at the doses usually used for the relief of motion sickness, on postural sway, optokinetic nystagmus (OKN) and circularvection (CV) in humans, using a within-subjects, double-blind, placebo-controlled design. Scopolamine and cyclizine were found to have no significant suppressive effect on these aspects of visual-vestibular interaction. Postural sway and CV were not significantly affected by either drug treatment; OKN SPV was significantly increased (p < 0.05), although OKN amplitude and frequency were unaffected. These results suggest that scopolamine and cyclizine, at doses used for the relief of motion sickness, may have minimal suppressive effects on these aspects of visual-vestibular interaction.

Rationale: Memory illusions are currently a focus of memory research. Studies using the Deese/Roediger and McDermott paradigm have shown a differential pattern of illusory memories is associated with amnesia and ageing. The effects of pharmacological agents in this paradigm are not yet known., Objective: Using this paradigm, the present study investigated the effects of a low dose of alcohol upon recollective experience of illusory memories., Methods: A double-blind cross-over design was used to compare the effects of alcohol (0.26-0.28 g.kg-1) with a matched placebo drink., Results: High levels of false recognition were obtained across both treatments, replicating previous results. Although the small dose of alcohol employed did not produce gross changes in measures of false memory, it did modify the pattern of recollective experience in terms of remember and know responses. Specifically, it increased the level of remember responses for falsely recognised items (critical lures)., Conclusion: These results are discussed in terms of ethanol's effects on false recognition of information which was not presented during the study episode. The effects of low dose alcohol on illusory memory are similar to the pattern found in ageing rather than that found in organic amnesia.

Binocular depth inversion represents an illusion of visual perception that is sensitive to various behavioural and psychiatric conditions. It is affected by cannabinoids, reflecting associated changes in perception. The present study investigated the differences in binocular depth inversion of different classes of natural and artificial objects and the effect of synthetic delta9-tetrahydrocannabinol (Dronabinol) on these illusionary perceptions. Using this model, the effects of orally administered Dronabinol on binocular depth inversion were investigated in 17 healthy male volunteers. Pictures from natural and artificial objects were presented stereoscopically and the depth perception of the volunteers was scored in an operationalized way. The timecourse of the effects of Dronabinol on binocular depth inversion was analyzed with regard to the stimulus classes (natural and synthetic objects). Significant differences in binocular depth inversion of the different groups of stimuli were revealed. Objects with a higher degree of everyday familiarity were generally seen as more illusionary than those with a lower degree of everyday familiarity. A strong impairment of binocular depth inversion due to Dronabinol was found in most classes of objects. Analysis of different stimulus classes provides further information on the underlying perceptual processing of binocular depth inversion. An impairment of top-down processing of visual sensory data by Dronabinol is suggested. The anandamidergic system seems to be involved in areas of visual information processing.

The possible effects on psychomotor performance, concentration, attention, and mood of acamprosate (calciumacetylhomotaurinate) were assessed using a randomized, double-blind, cross-over, placebo-controlled design involving 12 healthy male volunteers. Acamprosate 2 g daily per os or placebo was administered for seven days and separated by washout intervals of at least 21 days. Objective tests evaluated psychomotor functions (simple reaction time measurement, binary choice reaction test, computerized visual searching task, sustained attention test). Mood was assessed using the Beck Depression Inventory and the Beschwerde-Liste to assess subjective physical impairment. Additionally, a visual 3-D illusion paradigm was applied to measure the psychotomimetic effect. A dose of acamprosate of 2 g/day for seven days was free of any significant effects on mood, concentration, attention, psychomotor performance and did not produce any subjective sedation, excitation or psychotomimetic effects.

Background and Objectives: In normal humans, placing a hand on a thermal grill containing warm elements separated by cool ones produces a burning sensation. In this case report, responses to a thermal grill in a patient with neuropathic pain were examined., Methods: The responses of a 31-year-old woman with complex regional pain syndrome type I (reflex sympathetic dystrophy) to a thermal grill were evaluated before and after stellate ganglion block., Results: The patient experienced a burning sensation when the unaffected hand was placed on the grill and could distinguish which element was warm and which was cool. An intolerable burning sensation caused the patient to quickly (within 4 seconds) withdraw the affected hand when it was placed on the grill. Touching cool elements with the affected hand produced an intense burning sensation (cold allodynia), whereas touching warm elements produced a pleasant warm sensation. Stellate ganglion block with phenol, local anesthetic, and steroid resulted in long-lasting absence of cold allodynia., Conclusion: The thermal grill may be a useful a tool to help understand the pathophysiology of complex regional pain syndrome type I.

Twenty-seven of eighty-eight (30.7%) Parkinsonian patients on chronic levodopa or levodopa/carbidopa therapy developed drug related dream phenomena. The patients reported three separate types of new dreams which we have classified as vivid dreams, night terrors and nightmares. These dreams are correlated to the duration of levodopa therapy although the mechanism of their production is unclear.

Low-dose ketamine anaesthesia was compared with neuroleptanaesthesia, in respect of immediate and longer-term psychomimetic reactions, in 40 female patients undergoing elective gynaecological surgery. Qualitatively, but not quantitatively, different psychomimetic reactions occurred in both groups. In the neurolept group the predominant complaint was of a dissociative nature, reported after 24 h by 11 (55%) of the patients, while in the ketamine group the predominant experience was dreaming, reported by eight (40%) of the patients after 24 h. Interviews after 3 months revealed a low frequency of psychomimetic reactions in both groups. However, 30% of all the patients (12) complained of impairment of intellectual function, and in seven patients this was severe enough to interfere with their ability to work.

The effects of haloperidol, nomifensine and lorazepam on the visual tilt illusion were studied in normal volunteers. Haloperidol and nomifensine produced no significant changes in the illusion, although in previous work they had been found to reduce and enhance, respectively, a closely related illusion, the tilt aftereffect. By contrast, lorazepam produced a dose-related increment in the size of the tilt illusion, but had no effect on the tilt aftereffect. The results are discussed in relation to proposed mechanisms which may underlie the two kinds of illusion. The differential effects of individual drugs on the two illusions may reflect their differing actions on two processes: lateral inhibition and adaptation in visual channels.