Static and dynamic characteristics of cerebral blood flow during the resting state in schizophrenia

Background: The cerebral network that is active during rest and is deactivated during goal-oriented activity is called the default mode network (DMN). It appears to be involved in self-referential mental activity. Atypical functional connectivity in the DMN has been observed in schizophrenia. One hypothesis suggests that pathologically increased DMN connectivity in schizophrenia is linked with a main symptom of psychosis, namely, misattribution of thoughts. Methods: A resting-state pseudocontinuous arterial spin labeling (ASL) study was conducted to measure absolute cerebral blood flow (CBF) in 34 schizophrenia patients and 27 healthy controls. Using independent component analysis (ICA), the DMN was extracted from ASL data. Mean CBF and DMN connectivity were compared between groups using a 2-sample t test. Results: Schizophrenia patients showed decreased mean CBF in the frontal and temporal regions (P < .001). ICA demonstrated significantly increased DMN connectivity in the precuneus (x/y/z = -16/-64/38) in patients than in controls (P < .001). CBF was not elevated in the respective regions. DMN connectivity in the precuneus was significantly correlated with the Positive and Negative Syndrome Scale scores (P < .01). Conclusions: In schizophrenia patients, the posterior hub-which is considered the strongest part of the DMN-showed increased DMN connectivity. We hypothesize that this increase hinders the deactivation of the DMN and, thus, the translation of cognitive processes from an internal to an external focus. This might explain symptoms related to defective self-monitoring, such as auditory verbal hallucinations or ego disturbances.

Effects of hypoxic-ischemic encephalopathy and whole-body hypothermia on neonatal auditory function: a pilot study.

We assessed the effects of hypoxic-ischemic encephalopathy (HIE) and whole-body hypothermia therapy on auditory brain stem evoked responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). We performed serial assessments of ABRs and DPOAEs in newborns with moderate or severe HIE, randomized to hypothermia ( N = 4) or usual care ( N = 5). Participants were five boys and four girls with mean gestational age (standard deviation) of 38.9 (1.8) weeks. During the first week of life, peripheral auditory function, as measured by the DPOAEs, was disrupted in all nine subjects. ABRs were delayed but central transmission was intact, suggesting a peripheral rather than a central neural insult. By 3 weeks of age, peripheral auditory function normalized. Hypothermia temporarily prolonged the ABR, more so for waves generated higher in the brain stem but the effects reversed quickly on rewarming. Neonatal audiometric testing is feasible, noninvasive, and capable of enhancing our understanding of the effects of HIE and hypothermia on auditory function.

Self-Reported Psychotic-Like Experiences Are a Poor Estimate of Clinician-Rated Attenuated and Frank Delusions and Hallucinations

Background: One reason for the decision to delay the introduction of an Attenuated Psychosis Syndrome in the main text of the fifth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders was the concern that attenuated psychotic symptoms (APS) might in fact be common features in adolescents and young adults from the general population of no psychopathological significance in themselves. This concern was based on reports of high prevalence rates of psychotic-like experiences (PLEs) in the general population and the assumption that PLEs are a good estimate of APS. Although the criterion validity of self-reported PLEs had already been studied with respect to clinician-rated psychotic symptoms and found insufficient, it had been argued that PLEs might in fact be more comparable with mild, subclinical expressions of psychotic symptoms and, therefore, with APS. The present paper is the first to specifically study this assumption. Sampling and Methods: The sample consisted of 123 persons seeking help at a service for the early detection of psychosis, of whom 54 had an at-risk mental state or psychosis, 55 had a nonpsychotic mental disorder and 14 had no full-blown mental disorder. PLEs were assessed with the Peters Delusion Inventory and the revised Launay-Slade Hallucination Scale, and psychotic symptoms and APS were assessed with the Structured Interview for Prodromal Syndromes. Results: At a level of agreement between the presence of any PLE (in 98.4% of patients) and any APS (in 40.7%) just exceeding chance (κ = 0.022), the criterion validity of PLEs for APS was insufficient. Even if additional qualifiers (high agreement or distress, preoccupation and conviction) were considered, PLEs (in 52.8%) still tended to significantly overestimate APS, and agreement was only fair (κ = 0.340). Furthermore, the group effect on PLE prevalence was, at most, moderate (Cramer's V ≤ 0.382). Conclusions: The prevalence of APS cannot be deduced from studies of PLEs. Thus, the high population prevalence rate of PLEs does not allow the conclusion that APS are common features of no pathological significance and would lack clinical validity as an Attenuated Psychosis Syndrome in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition. Rather, the population prevalence rate of APS has to be assumed to be largely unknown at present but is likely lower than indicated by epidemiological studies of PLEs. Therefore, dedicated studies are warranted, in which APS are assessed in a way that equates to their clinical evaluation.

On sex-related differences in auditory and visual sensory functioning

The present study was designed to elucidate sex-related differences in two basic auditory and one basic visual aspect of sensory functioning, namely sensory discrimination of pitch, loudness, and brightness. Although these three aspects of sensory functioning are of vital importance in everyday life, little is known about whether men and women differ from each other in these sensory functions. Participants were 100 male and 100 female volunteers ranging in age from 18 to 30 years. Since sensory sensitivity may be positively related to individual levels of intelligence and musical experience, measures of psychometric intelligence and musical background were also obtained. Reliably better performance for men compared to women was found for pitch and loudness, but not for brightness discrimination. Furthermore, performance on loudness discrimination was positively related to psychometric intelligence, while pitch discrimination was positively related to both psychometric intelligence and levels of musical training. Additional regression analyses revealed that each of three predictor variables (sex, psychometric intelligence, and musical training) accounted for a statistically significant portion of unique variance in pitch discrimination. With regard to loudness discrimination, regression analysis yielded a statistically significant portion of unique variance for sex as a predictor variable, whereas psychometric intelligence just failed to reach statistical significance. The potential influence of sex hormones on sex-related differences in sensory functions is discussed.

Performance on auditory and visual temporal informationprocessing is related to psychometric intelligence

The present study investigated the relationship between psychometric intelligence and temporal resolution power (TRP) as simultaneously assessed by auditory and visual psychophysical timing tasks. In addition, three different theoretical models of the functional relationship between TRP and psychometric intelligence as assessed by means of the Adaptive Matrices Test (AMT) were developed. To test the validity of these models, structural equation modeling was applied. Empirical data supported a hierarchical model that assumed auditory and visual modality-specific temporal processing at a first level and amodal temporal processing at a second level. This second-order latent variable was substantially correlated with psychometric intelligence. Therefore, the relationship between psychometric intelligence and psychophysical timing performance can be explained best by a hierarchical model of temporal information processing.

Patient and Informant Views on Visual Hallucinations in Parkinson Disease.

OBJECTIVE Visual hallucinations (VHs) are a very personal experience, and it is not clear whether information about them is best provided by informants or patients. Some patients may not share their hallucinatory experiences with caregivers to avoid distress or for fear of being labeled insane, and others do not have informants at all, which limits the use of informant-based questionnaires. The aim of this study was to compare patient and caregiver views about VHs in Parkinson disease (PD), using the North-East Visual Hallucinations Interview (NEVHI). METHODS Fifty-nine PD patient-informant pairs were included. PD patients and informants were interviewed separately about VHs using the NEVHI. Informants were additionally interviewed using the four-item version of the Neuropsychiatric Inventory. Inter-reliability and concurrent validity of the different measures were compared. RESULTS VHs were more commonly reported by patients than informants. The inter-rater agreement between NEVHI-patient and NEVHI-informant was moderate for complex VHs (Cohen's kappa = 0.44; 95% confidence interval [CI]: 0.13-0.75; t = 3.43, df = 58, p = 0.001) and feeling of presence (Cohen's kappa = 0.35; 95% CI: 0.00-0.70; t = 2.75, df = 58, p = 0.006), but agreement was poor for illusions (Cohen's kappa = 0.25; 95% CI: -0.07-0.57; t = 2.36, df = 58, p = 0.018) and passage hallucinations (Cohen's kappa = 0.16; 95% CI: -0.04-0.36; t = 2.26, df = 58, p = 0.024). CONCLUSION When assessing VHs in PD patients, it is best to rely on patient information, because not all patients share the details of their hallucinations with their caregivers.

The Neuroscience of Visual Hallucinations

Each year, some two million people in the United Kingdom experience visual hallucinations. Infrequent, fleeting visual hallucinations, often around sleep, are a usual feature of life. In contrast, consistent, frequent, persistent hallucinations during waking are strongly associated with clinical disorders; in particular delirium, eye disease, psychosis, and dementia. Research interest in these disorders has driven a rapid expansion in investigatory techniques, new evidence, and explanatory models. In parallel, a move to generative models of normal visual function has resolved the theoretical tension between veridical and hallucinatory perceptions. From initial fragmented areas of investigation, the field has become increasingly coherent over the last decade. Controversies and gaps remain, but for the first time the shapes of possible unifying models are becoming clear, along with the techniques for testing these. This book provides a comprehensive survey of the neuroscience of visual hallucinations and the clinical techniques for testing these. It brings together the very latest evidence from cognitive neuropsychology, neuroimaging, neuropathology, and neuropharmacology, placing this within current models of visual perception. Leading researchers from a range of clinical and basic science areas describe visual hallucinations in their historical and scientific context, combining introductory information with up-to-date discoveries. They discuss results from the main investigatory techniques applied in a range of clinical disorders. The final section outlines future research directions investigating the potential for new understandings of veridical and hallucinatory perceptions, and for treatments of problematic hallucinations. Fully comprehensive, this is an essential reference for clinicians in the fields of the psychology and psychiatry of hallucinations, as well as for researchers in departments, research institutes and libraries. It has strong foundations in neuroscience, cognitive science, optometry, psychiatry, psychology, clinical medicine, and philosophy. With its lucid explanation and many illustrations, it is a clear resource for educators and advanced undergraduate and graduate students.

Visual Hallucinations in Eye Disease and Lewy Body Disease

Objective: Visual hallucinations (VH) most commonly occur in eye disease (ED), Parkinson’s disease (PD), and Lewy body dementia (LBD). The phenomenology of VH is likely to carry important information about the brain areas within the visual system generating them. Methods: Data from five controlled cross-sectional VH studies (164 controls, 135 ED, 156 PD, 79 (PDD 48 + DLB 31) LBD) were combined and analysed. The prevalence, phenomenology, frequency, duration, and contents of VH were compared across diseases and gender. Results: Simple VH were most common in ED patients (ED 65% vs. LBD 22% vs. PD 9%, Chi-square [χ2] test: χ2=31.43, df=2, p<0.001), whilst complex VH were more common in LBD (LBD 76% vs. ED 38%, vs PD 28%, Chi-square test: χ2=96.80, df=2, p<0.001). The phenomenology of complex VH was different across diseases and gender. ED patients reported more “flowers” (ED 21% vs. LBD 6% vs. PD 0%, Chi-square test: χ2=10.04, df=2, p=0.005) and “body parts” (ED 40% vs. LBD 17% vs. PD 13%, Chi-square test: χ2=11.14, df=2, p=0.004); in contrast LBD patients reported “people” (LBD 85% vs. ED 67% vs. PD 63%, Chi-square test: χ2=6.20, df=2, p=0.045) and “animals/insects” (LBD 50% vs. PD 42% vs. ED 21%, Chi-square test: χ2=9.76, df=2, p=0.008). Males reported more “machines” (13 % vs. 2%, Chi-square test: χ2=6.94, df=1, p=0.008), whilst females reported more “family members/children” (48% vs. 29%, Chi-square test: χ2=5.10, df=1, p=0.024). Conclusions: The phenomenology of VH is likely related to disease specific dysfunctions within the visual system and to past, personal experiences.