A Case of Artificial Intelligence Chatbot Hallucination.

This essay reports on fictitious source materials created by AI chatbots, encourages human oversight to identify fabricated information, and suggests a creative use for these tools.

An exploratory study on the heterogeneity of postoperative delirium: Preoperative cognitive screening does not detect hallucinatory delirium risk.

INTRODUCTION: This study compared the clinical characteristics of patients who had hallucinations and those who did not during delirium after elective cancer surgery. MATERIALS AND METHODS: This study retrospectively observed 1137 consecutive patients who had preoperative screening by a trained nurse before elective major urologic cancer surgery in our department. We compared the patient characteristics, including mini-cognitive assessment instrument (Mini-Cog) and Geriatric-8 (G8) scores, between those who developed postoperative delirium and those who did not, and also between those who had hallucinations and those who did not during delirium. RESULTS: Out of 1137 patients, 68 developed postoperative delirium, and 12 of them had hallucinations. A hierarchical cluster analysis based on the G8 and Mini-Cog scores divided the patients into two groups: one with high G8 and cognitive function (36 patients) and one with low G8 and cognitive function (32 patients). Hallucinations during delirium were more frequent in the high G8 and cognitive function group (11 out of 36 patients) than in the low G8 and cognitive function group (one out of 32 patients). Patients who had hallucinations during delirium also had higher preoperative Mini-Cog scores (P = 0.002) and G8 scores (P = 0.03) than those who did not, indicating better cognitive function and less frailty. DISCUSSIONS: We identified a patient population that is prone to hallucinations that preoperative screening tools cannot detect. This suggests the heterogeneity of postoperative delirium and the need for further research.

Performance of Generative Large Language Models on Ophthalmology Board-Style Questions.

PURPOSE: To investigate the ability of generative artificial intelligence models to answer ophthalmology board-style questions. DESIGN: Experimental study. METHODS: This study evaluated 3 large language models (LLMs) with chat interfaces, Bing Chat (Microsoft) and ChatGPT 3.5 and 4.0 (OpenAI), using 250 questions from the Basic Science and Clinical Science Self-Assessment Program. Although ChatGPT is trained on information last updated in 2021, Bing Chat incorporates a more recently indexed internet search to generate its answers. Performance was compared with human respondents. Questions were categorized by complexity and patient care phase, and instances of information fabrication or nonlogical reasoning were documented. MAIN OUTCOME MEASURES: Primary outcome was response accuracy. Secondary outcomes were performance in question subcategories and hallucination frequency. RESULTS: Human respondents had an average accuracy of 72.2%. ChatGPT-3.5 scored the lowest (58.8%), whereas ChatGPT-4.0 (71.6%) and Bing Chat (71.2%) performed comparably. ChatGPT-4.0 excelled in workup-type questions (odds ratio [OR], 3.89, 95% CI, 1.19-14.73, P = .03) compared with diagnostic questions, but struggled with image interpretation (OR, 0.14, 95% CI, 0.05-0.33, P < .01) when compared with single-step reasoning questions. Against single-step questions, Bing Chat also faced difficulties with image interpretation (OR, 0.18, 95% CI, 0.08-0.44, P < .01) and multi-step reasoning (OR, 0.30, 95% CI, 0.11-0.84, P = .02). ChatGPT-3.5 had the highest rate of hallucinations and nonlogical reasoning (42.4%), followed by ChatGPT-4.0 (18.0%) and Bing Chat (25.6%). CONCLUSIONS: LLMs (particularly ChatGPT-4.0 and Bing Chat) can perform similarly with human respondents answering questions from the Basic Science and Clinical Science Self-Assessment Program. The frequency of hallucinations and nonlogical reasoning suggests room for improvement in the performance of conversational agents in the medical domain.

[On the problem of hysterocatonia in the clinical space of schizophrenia and schizophrenic spectrum disorders]. / K probleme isterokatatonii v klinicheskom prostranstve shizofrenii i rasstroistv shizofrenicheskogo spektra.

OBJECTIVE: To determinate the premorbid personality dimensions in patients with hysterocatatonia; to study the psychopathological characteristics, making it possible to distinguish the manifestations of hysterical catatonia among other hysterical and catatonic phenomena; to establish the prognostic value of the hysterocatatonia, occurring in the structure of schizophrenia and schizophrenic spectrum disorders (SSD). MATERIAL AND METHODS: 25 patients with a verified diagnosis of schizophrenia and SSD (according to ICD-10) with a predominance of «mild¼ catatonic phenomena in the clinical picture of the disease (manifestations of hyperkinesia, pseudoepileptic paroxysms, isolated parakinesis, psychomotor agitation, accompanied by local muscle spasm and/or an increase in general muscle tone, etc.). RESULTS: The overall severity of catatonic disorders corresponded to 22.7±8.3 BFCRS scale points. The phenomenon of abulic deficiency prevailed in the structure of negative disorders (SANS avolition-apathy - 3.7±0.6; SANS anhedonia-asociality - 2.8±0.7). The increase in the subscales of delusional (2.1±0.2) and hallucinatory phenomena (mild signs of somatic passivity according to K. Schneider), accompanied by a feeling of uncontrollability and «alienation¼ of motor symptoms, was observed according to the SAPS scale. The correlation between the BFCRS scores and the hallucinations (0.765) and delusions (0.653) subscales of the SAPS scale has been found. The hysterocatatonia phenomenon is an independent psychopathological construct, forming in the space of schizophrenia and SSD and revealing a tropism to the pathocharacterological structure of conversion hysteria. The key characteristic, that distinguishes the manifestations of hysterocatonia - is the formation mechanism of movement disorders, based on the phenomenon of mental automatism by G.G. Clérambault. CONCLUSION: The inclusion of hysterocatatonical symptoms into the clinical picture of schizophrenia and SSD serves as the predictor of adverse course of the disease as long as the condition is accompanied by the "layering" of catatonic-hypochondrical and catatonic-delusional symptoms, and the previously low-progressive course of the disease starts being aggravated by the development of repeated attacks with exacerbation of psychomotor symptoms.

Metabolomics and Cytokine Analysis for Identification of Schizophrenia with Auditory Hallucination.

PURPOSE: To investigate the metabolic profile and biomarkers of schizophrenia with auditory hallucinations (AHs). METHODS: A total of 18 schizophrenic patients with the symptom of pure AHs (pAHs), 28 without AH (nAHs) and 43 age-matched healthy persons (Con) were enrolled in this study. Participants in pAHs and nAHs groups had relapsed into exacerbations of psychosis after self-discontinuing antipsychotics for at least one month; blood samples were drawn prior to restarting anti-psychotic treatment. Participants with history of recreational substance use were excluded. Positive and Negative Syndrome Scale (PANSS) and Auditory Hallucinations Rating Scale (AHRS) were used to assess the clinical mental state of all samples. Enzyme-linked immunosorbent assay (ELISA) was used to estimate the level of cytokines, and metabolomics analysis to identify potential biomarkers and pathways in the three groups. Graphpad 8.0 software was used to calculate the area under the receiver operating characteristic (ROC) curve. The relationship between metabolites and cytokines were determined using correlation analysis. RESULTS: Questionnaire scores showed significant differences in the positive symptom scale and PANSS total between nAHs and pAHs groups. Four cytokines (BDNF, IL-2, NGF-ß and TNF-α) differed significantly among the three groups. Six molecules in the nAHs group (phenylalanine, hippurate, serine, glutamate, valine and cystine) and four in the pAHs group (phenylalanine, serine, glutamate and cystine) were identified as potential biomarkers. In addition, phenylalanine was shown as a potential independent diagnostic biomarker for pAHs. Correlation analysis revealed that cystine and serine were significantly negatively correlated with IL-2 in the pAHs group. CONCLUSIONS: This study revealed the metabolic profile of patients with schizophrenia with AHs and provided new information to support the diagnosis. The identification of unique biomarkers would contribute to objective and reliable diagnoses of patients with schizophrenia with AH.

Examining transcranial random noise stimulation as an add-on treatment for persistent symptoms in schizophrenia (STIM'Zo): a study protocol for a multicentre, double-blind, randomized sham-controlled clinical trial.

BACKGROUND: One out of three patients with schizophrenia failed to respond adequately to antipsychotics and continue to experience debilitating symptoms such as auditory hallucinations and negative symptoms. The development of additional therapeutic approaches for these persistent symptoms constitutes a major goal for patients. Here, we develop a randomized-controlled trial testing the efficacy of high-frequency transcranial random noise stimulation (hf-tRNS) for the treatment of resistant/persistent symptoms of schizophrenia in patients with various profiles of symptoms, cognitive deficits and illness duration. We also aim to investigate the biological and cognitive effects of hf-tRNS and to identify the predictors of clinical response. METHODS: In a randomized, double-blind, 2-arm parallel-group, controlled, multicentre study, 144 patients with schizophrenia and persistent symptoms despite the prescription of at least one antipsychotic treatment will be randomly allocated to receive either active (n = 72) or sham (n = 72) hf-tRNS. hf-tRNS (100-500 Hz) will be delivered for 20 min with a current intensity of 2 mA and a 1-mA offset twice a day on 5 consecutive weekdays. The anode will be placed over the left dorsolateral prefrontal cortex and the cathode over the left temporoparietal junction. Patients' symptoms will be assessed prior to hf-tRNS (baseline), after the 10 sessions, and at 1-, 3- and 6-month follow-up. The primary outcome will be the number of responders defined as a reduction of at least 25% from the baseline scores on the Positive and Negative Syndrome Scale (PANSS) after the 10 sessions. Secondary outcomes will include brain activity and connectivity, source monitoring performances, social cognition, other clinical (including auditory hallucinations) and biological variables, and attitude toward treatment. DISCUSSION: The results of this trial will constitute a first step toward establishing the usefulness of hf-tRNS in schizophrenia whatever the stage of the illness and the level of treatment resistance. We hypothesize a long-lasting effect of active hf-tRNS on the severity of schizophrenia symptoms as compared to sham. This trial will also have implications for the use of hf-tRNS as a preventive intervention of relapse in patients with schizophrenia. TRIAL REGISTRATION: ClinicalTrials.gov NCT02744989. Prospectively registered on 20 April 2016.

[Isolated metamorphopsia and visual pseudohallucinations in a patient with anti-NMDA receptor encephalitis]. / Isolierte Metamorphopsien und visuelle Pseudohalluzinationen bei einem Patienten mit Anti-NMDA-Rezeptor-Enzephalitis.

This article reports the case of a 40-year-old male patient with isolated metamorphopsia and visual pseudohallucinations lasting for 2 weeks. As the ophthalmological findings were not pathological, a further neurological examination was performed. After diagnosis of anti-N-methyl-D-aspartate (NMDA) receptor encephalitis, which can be manifested in various psychiatric, neurological and ophthalmological ways, the oligosymptomatic patient received high-dose corticosteroid treatment with intravenous immunoglobulins, which stopped the symptoms.

Vision loss and hallucinations: perspectives from neurology and ophthalmology.

PURPOSE OF REVIEW: The aim of this article is to summarize the evidence for visual impairment as a risk factor for visual hallucinations in neurologic disease and recent advances in our understanding of the central visual pathways that mediate this association. RECENT FINDINGS: Recent studies have described the prevalence Charles Bonnet syndrome and questioned its lack of association with cognitive impairment, used advanced neuroimaging to show that disinhibition of the occipital lobe is involved in the pathogenesis of visual hallucinations in Parkinson's disease, and demonstrated that visual impairment because of eye disease is a consistent risk factor for visual hallucinations across a number of different neurodegenerative disease populations. SUMMARY: Through connections between the primary visual cortex and other brain structures, visual function is closely tied to visual hallucinations. Given that the vast majority of vision loss is caused by ophthalmic disease, much of which is preventable or treatable, the detection and treatment of vision loss in at-risk populations may reduce the burden and consequences of visual hallucinations in older adults.

Hallucinations and other psychotic experiences across diagnoses: A comparison of phenomenological features.

Although psychotic experiences are prevalent across many psychiatric, neurological, and medical disorders, investigation of these symptoms has largely been restricted to diagnostic categories. This study aims to examine phenomenological similarities and differences across a range of diagnoses. We assessed frequency, severity and phenomenology of psychotic experiences in 350 outpatients including; participants with schizophrenia spectrum disorders, hearing impairment, Parkinson's disease, Lewy Body Dementia, Alzheimer's disease, visual impairment, posttraumatic stress disorder, borderline personality disorder, and participants with recent major surgery. Psychotic phenomena were explored between these groups using the Questionnaire for Psychotic Experiences (QPE). Participants with major psychiatric disorders reported a combination of several psychotic experiences, and more severe experiences compared to all other disorders. Participants with recent major surgery or visual impairment experienced isolated visual hallucinations. Participants with hearing impairment reported isolated auditory hallucinations, whereas the neurodegenerative disorders reported visual hallucinations, occasionally in combination with hallucinations in another modality or delusions. The phenomenology between neurodegenerative disorders, and within major psychiatric disorders showed many similarities. Our findings indicate that the phenomenology of psychotic experiences is not diagnosis specific, but may rather point to the existence of various subtypes across diagnoses. These subtypes could have a different underlying etiology requiring specific treatment.

Self-reported vision and hallucinations in older adults: results from two longitudinal US health surveys.

BACKGROUND: Vision loss may be a risk factor for hallucinations, but this has not been studied at the population level. METHODS: To determine the association between self-reported vision loss and hallucinations in a large community-based sample of older adults, we performed a cross-sectional and longitudinal analysis of two large, nationally representative US health surveys: the National Health and Aging Trends Study (NHATS) and the Health and Retirement Study (HRS). Visual impairment and hallucinations were self- or proxy-reported. Multivariate single and mixed effects logistic regression models were built to examine whether visual impairment and history of cataract surgery were associated with hallucinations. RESULTS: In NHATS (n = 1520), hallucinations were more prevalent in those who reported difficulty reading newspaper print (OR 1.77, 95% confidence interval (CI): 1.32-2.39) or recognising someone across the street (OR 2.48, 95% CI: 1.86-3.31) after adjusting for confounders. In HRS (n = 3682), a similar association was observed for overall (OR 1.32, 95% CI: 1.08-1.60), distance (OR 1.61, 95% CI: 1.32-1.96) and near eyesight difficulties (OR 1.52, 95% CI: 1.25-1.85). In neither sample was there a significant association between cataract surgery and hallucinations after adjusting for covariates. CONCLUSIONS: Visual dysfunction is associated with increased odds of hallucinations in the older US adult population. This suggests that the prevention and treatment of vision loss may potentially reduce the prevalence of hallucinations in older adults.

Growing Skull Fracture of Temporal Bone in Adults: A Case Report and Literature Review.

Growing skull fracture (GSF) is an uncommon post-traumatic complication, which accounts for approximately 0.05% to 1% of all skull fractures. Delayed diagnosis of GSF in adulthood is rare and often involved with a variety of neurological symptoms. Here, we reported an adult patient, with an interval of 17 years from initial head trauma to first diagnosis of GSF. The patient complained of short periods of fainting and bilateral visual hallucinations, with a hard palpable bulge around his right occipitomastoid suture region. Computed tomographic imaging demonstrated an arachnoid cyst extending into right mastoid cavity. Consequently, the delayed diagnosis of GSF was confirmed, and the patient was managed with duroplasty and cranioplasty. At the 8-month follow-up, the patient showed an uneventful postoperative recovery. A comprehensive literature review was also conducted, and a total of 70 GSF cases were identified and summarized. According to the literature review, patients with GSF generally have a history of head trauma in their childhood, and delayed diagnosis is a common situation. Diagnosis of GSF should include complete retrospective medical history, physical, and imaging examinations. Once the diagnosis is confirmed, cranioplasty accompanied with duroplasty might be the most effective way to relieve symptoms and prevent further damage.

[Visual hallucinations, misidentification and reduplication of time: a sense of distorted reality due to a cerebral metastasis]. / Visuele hallucinaties, misidentificaties en tijdsreduplicatie: verstoorde realiteitsbeleving door hersenmetastase.

We describe a 66-year-old female patient with no prior psychiatric history who presented with an unusual psychotic state, largely in accordance with Fregoli syndrome (misidentification of people). Further, the patient suffered from reduplication of time, scenic hallucinations and psychotic perceptions. Symptoms were the result of a brain metastasis originating from a lung carcinoma. We describe the performed (additional) diagnostics and discuss how to differentiate between organic and functional psychosis, as well as the given psychiatric treatment. Finally, potential pathophysiological explanations are discussed that might explain the (reduction of) symptoms in the patient.

Bicalutamide-associated hallucinations in a metastatic prostate cancer patient: A case report.

INTRODUCTION: Bicalutamide is widely used in the treatment of prostate cancer. Among its side effects, central nervous system disorders are relatively rare, and the information about bicalutamide-associated hallucinations is limited. CASE REPORT: We report an uncommon case of a patient with metastatic prostate cancer, who had hallucinations due to the use of bicalutamide. MANAGEMENT AND OUTCOME: The patient accepted to receive only hormonal therapy (bicalutamide and leuprolide acetate). But he developed hallucinations due to bicalutamide use. His hallucinations disappeared after discontinuation of bicalutamide. A good response was obtained with the use of luteinizing hormone-releasing hormone agonist monotherapy. DISCUSSION: The pathophysiology of bicalutamide-induced hallucinations is unclear. We hypothesize that antiandrogens can indirectly cause hallucinations through changes in plasma testosterone and cerebral reelin expression. Additionally, luteinizing hormone-releasing hormone agonist monotherapy is a good option in metastatic prostate cancer patients who have intolerable side effects due to the use of antiandrogens.

The prognostic role of catatonia, hallucinations, and symptoms of schizophrenia in acute and transient psychosis.

OBJECTIVES: To examine the prospective temporal stability of acute and transient psychotic disorders (ATPDs) and analyze whether there are clinical, psychopathological, or sociodemographic characteristics that predict ATPD diagnostic stability. METHOD: We conducted a prospective, 2-year, observational study of patients presenting a first-episode ATPD. A multivariate logistic regression model was developed to identify independent variables associated with ATPD diagnostic stability. Well-established predictive factors of diagnostic stability, as well as all the psychopathological features included in the ICD-10 Diagnostic Criteria for Research (DCR) descriptions of ATPD, were analyzed. RESULTS: Sixty-eight patients with a first episode of ATPD completed the study with a diagnostic stability rate as high as 55.9% (n = 38) at the end of the follow-up period. Multivariate analysis revealed that diagnostic stability was independently significantly associated with the baseline presence of motility disturbances (OR = 6.86, 95% CI = 1.10-42.62; P = 0.039), the absence of hallucinations (OR = 5.75, 95% CI = 1.51-21.98; P = 0.010), and the absence of schizophrenic features (OR = 7.13, 95% CI = 1.38-36.90; P = 0.019). CONCLUSION: A symptom checklist assessing these psychopathological features would enable early identification of those subjects whose initial ATPD diagnosis will remain stable over time.

Excited catatonia in a patient with fatal pulmonary embolism and a successful treatment strategy.

BACKGROUND: Patients with psychiatric disorders in critical condition are difficult to treat. In this study, we report on a patient with underlying schizoaffective disorder who developed catatonia, cardiac arrest, and pulmonary embolism, as well as a successful treatment strategy. CASE PRESENTATION: The inpatient is a 41-year-old morbidly obese male with schizoaffective disorder whose clozapine dosage was titrated from 100 mg to 175 mg due to auditory hallucination and agitation. The patient abruptly developed acute cardiopulmonary symptoms associated with an elevated troponin-I level. He was transferred to a cardiac intensive care unit, where he remained for 3 days. He was also found to have excited catatonic symptoms, and the lorazepam-diazepam protocol was initiated to quickly relieve the catatonia. Once the coronary angiogram was read as normal, the patient was transferred back to the psychiatric ward. However, the patient then suffered from in-hospital cardiac arrest. He was resuscitated and again transferred to the medical intensive care unit. Computed tomography confirmed the diagnosis of a pulmonary embolism. The patient was treated with Rivaroxaban 30 mg/d for the first 21 days, followed by 20 mg daily for 3 months. To control his severe and refractory psychotic symptoms, the patient was re-prescribed clozapine. During the 15-month follow-up period, the patient demonstrated a fair response and tolerability to clozapine 150 mg without symptoms relapse and no thromboembolic event. CONCLUSION: This report can serve to remind psychiatrists and physicians to be aware of fatal conditions in patients with psychiatric diseases and physical illnesses.

Protein Profiling in Serum and Cerebrospinal Fluid Following Complex Surgery on the Thoracic Aorta Identifies Biological Markers of Neurologic Injury.

Surgery on the arch or descending aorta is associated with significant risk of neurological complications. As a consequence of intubation and sedation, early neurologic injury may remain unnoticed. Biomarkers to aid in the initial diagnostics could prove of great value as immediate intervention is critical. Twenty-three patients operated in the thoracic aorta with significant risk of perioperative neurological injury were included. Cerebrospinal fluid (CSF) and serum were obtained preoperatively and in the first and second postoperative days and assessed with a panel of 92 neurological-related proteins. Three patients suffered spinal cord injury (SCI), eight delirium, and nine hallucinations. There were markers in both serum and CSF that differed between the affected and non-affected patients (SCI; IL6, GFAP, CSPG4, delirium; TR4, EZH2, hallucinations; NF1). The study identifies markers in serum and CSF that reflect the occurrence of neurologic insults following aortic surgery, which may aid in the care of these patients.

A psychotic experience during adolescence: reasoning about differential diagnosis. case report

ABSTRACT CONTEXT: The aim of the present clinical review was to illustrate the diagnostic difficulty associated with psychotic experiences during adolescence, in the light of the multiplicity of circumstances interplaying during this period. It was also intended to illustrate the observation that not all hallucinations occur in the context of a declared psychotic disorder. Case Report: The patient was a 16-year-old adolescent girl who came to the Emergency Department of Coimbra Pediatric Hospital. On admission, she displayed mood and sensory perception disorders, with a bizarre gait abnormality. A diagnosis of conversion disorder was finally suggested, in accordance with the International Classification of Diseases, 10th edition. CONCLUSIONS: Conversive hallucinations are rare in the psychiatric literature. This diagnostic hypothesis only gained consistency over a long period of follow-up within a child and adolescent psychiatry outpatient service, which was fundamental for appropriate diagnostic clarification. The authors discuss psychotic experiences that can arise from a neurotic setting and share the reasoning that was constructed in relation to the differential diagnosis. The psychogenesis and phenomenology of this young patient's conversive hallucinations and the therapeutic strategies adopted over the course of the follow-up are also discussed.

Factors Associated With Phantom Odor Perception Among US Adults: Findings From the National Health and Nutrition Examination Survey.

Importance: Phantom odor perception can be a debilitating condition. Factors associated with phantom odor perception have not been reported using population-based epidemiologic data. Objective: To estimate the prevalence of phantom odor perception among US adults 40 years and older and identify factors associated with this condition. Design, Setting, and Participants: In this cross-sectional study with complex sampling design, 7417 adults 40 years and older made up a nationally representative sample from data collected in 2011 through 2014 as part of the National Health and Nutrition Examination Survey. Exposures: Sociodemographic characteristics, cigarette and alcohol use, head injury, persistent dry mouth, smell function, and general health status. Main Outcomes and Measures: Phantom odor perception ascertained as report of unpleasant, bad, or burning odor when no actual odor exists. Results: Of the 7417 participants in the study, 52.8% (3862) were women, the mean (SD) age was 58 (12) years, and the prevalence of phantom odor perception occurred in 534 participants, which was 6.5% of the population (95% CI, 5.7%-7.5%). Phantom odor prevalence varied considerably by age and sex. Women 60 years and older reported phantom odors less commonly (7.5% [n = 935] and 5.5% [n = 937] among women aged 60-69 years and 70 years and older, respectively) than younger women (9.6% [n = 1028] and 10.1% [n = 962] among those aged 40-49 years and 50-59 years, respectively). The prevalence among men varied from 2.5% (n = 846) among men 70 years and older to 5.3% (n = 913) among men 60 to 69 years old. Phantom odor perception was 60% (n = 1602) to 65% (n = 2521) more likely among those with an income-to-poverty ratio of less than 3 compared with those in the highest income-to-poverty ratio group (odds ratio [OR], 1.65; 95% CI, 1.06-2.56; and OR, 1.60; 95% CI, 1.01-2.54 for income-to-poverty ratio <1.5 and 1.5-2.9, respectively). Health conditions associated with phantom odor perception included persistent dry mouth (OR, 3.03; 95% CI, 2.17-4.24) and history of head injury (OR, 1.74; 95% CI, 1.20-2.51). Conclusions and Relevance: An age-related decline in the prevalence of phantom odor perception is observed in women but not in men. Only 11% (n = 64) of people who report phantom odor perception have discussed a taste or smell problem with a clinician. Associations of phantom odor perception with poorer health and persistent dry mouth point to medication use as a potential explanation. Prevention of serious head injuries could have the added benefit of reducing phantom odor perception.