This chapter provides an overview of epidemiological studies on the recurrence of hallucinatory phenomena in the general population and addresses the role of visual hallucinations found in sleep and during states of transition to/from wakefulness. It describes the visual hallucinations during sensory deprivation and bereavement is discussed. The chapter discusses the long-standing debate over the continuity or discontinuity between hallucinations and normal functioning. The prevalence of visual hallucinations after bereavement is higher in pathological conditions as when abnormal grief reactions, post-traumatic stress disorder (PTSD), Charles Bonnet syndrome or reactive psychoses are also present. However, the phenomenon is also described in physiological grief reactions and is generally thought to be largely underestimated. According to the Bayesian model of brain function, information is processed by structurally or functionally embodying a prediction and responding to errors, from the level of single neuronal cells to complex circuits.
Objective It has been shown that a disorder of self-monitoring and/or self agency may underlie positive symptoms in schizophrenia, such as hallucinations and delusions of control. The objective of our study was to explore the deficit of these constructs in a sample of schizophrenic subjects by means of low-cost virtual reality. Methods 15 schizophrenic subjects and 10 age matched control subjects were tested in two different sessions of a Microsoft Xbox videogame (Dungeons & Dragons: Heroes), in which two players had to cooperate by fighting against various enemies in a virtual space. In each session an avatar was assigned to the test subject: in the first session the test subject's avatar was distinguished by a different coloured circle from the tester's one. In the second session the test subject's avatar was identical to the tester's one. Before playing the game, the schizophrenic test subjects and controls were evaluated on a neuropsychological battery including visuo spatial and executive abilities. Clinical characteristics of the schizophrenic subjects were also assessed. Results While in the first session patients and normal controls performed similarly, in the second session schizophrenic subjects confused their own avatar more often with the tester's one compared to normal controls (ANOVA Sig.,035). A regression analysis identified visuospatial abilities and set shifting as best predictors of performance in the videogame, while there was no correlation between the performance in the videogame and the clinical variables. Conclusions Low-cost virtual reality can be used to explore deficits of self monitoring/self agency in schizophrenia.
Factor Analysis can extract salient features from EEG data and reduce redundancy of multi-channel computerized EEG data. A 16-channel computerized frequency analysis of background brain electrical activity during 3 functional conditions (eyes closed, eyes open and hyperventilation) was carried out in two groups, fifty healthy subjects and twenty-three schizophrenics. The power log-transformed relative values of normal subjects and schizophrenic patients were submitted to Factor Analysis and the resulting factor scores were compared. Schizophrenics showed EEG abnormalities in delta 2, theta 1 and alpha 2 bands for the first factor, accounting for the eyes closed condition, and in theta 2 and beta 2 bands for the second factor, accounting for the eyes open condition. This preliminary study demonstrates the utility of Factor Analysis in managing and comparing computerized EEG data.
This report describes a patient with a DSM-III-R diagnosis of obsessive compulsive disorder and a nuclear magnetic resonance picture of a normal pressure hydrocephalus. After neurosurgery, the patient showed marked improvement in his compulsions which previously had shown little response to pharmacological treatment.
