Visual Hallucinations in the Psychosis Spectrum and Comparative Information From Neurodegenerative Disorders and Eye Disease

Abstract

Much of the research on visual hallucinations (VHs) has been conducted in the context of eye disease and neurodegenerative conditions, but little is known about these phenomena in psychiatric and nonclinical populations. The purpose of this article is to bring together current knowledge regarding VHs in the psychosis phenotype and contrast this data with the literature drawn from neurodegenerative disorders and eye disease. The evidence challenges the traditional views that VHs are atypical or uncommon in psychosis. The weighted mean for VHs is 27% in schizophrenia, 15% in affective psychosis, and 7.3% in the general community. VHs are linked to a more severe psychopathological profile and less favorable outcome in psychosis and neurodegenerative conditions. VHs typically co-occur with auditory hallucinations, suggesting a common etiological cause. VHs in psychosis are also remarkably complex, negative in content, and are interpreted to have personal relevance. The cognitive mechanisms of VHs in psychosis have rarely been investigated, but existing studies point to source-monitoring deficits and distortions in top-down mechanisms, although evidence for visual processing deficits, which feature strongly in the organic literature, is lacking. Brain imaging studies point to the activation of visual cortex during hallucinations on a background of structural and connectivity changes within wider brain networks. The relationship between VHs in psychosis, eye disease, and neurodegeneration remains unclear, although the pattern of similarities and differences described in this review suggests that comparative studies may have potentially important clinical and theoretical implications.

Varieties of Voice-Hearing: Psychics and the Psychosis Continuum

“…However, it is difficult to say whether the hallucinations were truly fused, a rarer phenomenon than simple multisensory hallucinations. 54 The increased likelihood that help-seeking voice-hearers' voices would replay things they have spoken or thought may reflect the unpleasant nature of their experiences, and although no participants met criteria for Posttraumatic Stress Disorder (PTSD), could speak to the possibility of past trauma in the helpseeking group. 55 We note that the help-seeking voicehearers were more likely to screen positive for BPD than psychics or non-voice-hearing help-seekers.…”

Visual mismatch negativity (vMMN): A review and meta-analysis of studies in psychiatric and neurological disorders

“…Furthermore, visual hallucinations are present in about 27% of schizophrenia patients (Waters et al, 2014). Magnetic resonance spectroscopy showed that increased levels of glutamine and decreased levels of glutamate in schizophrenic patients were not restricted to the frontal regions, but were evident also in the occipital lobe (Chang et al, 2007;Keshavan et al, 2009).…”

“…Adaptation has been observed in electrophysiological studies throughout the visual system including the retina (Hosoya, Baccus, & Meister, 2005), thalamus (Solomon, Peirce, Dhruv, & Lennie, 2004), superior colliculus (Boehnke et al, 2011), and several cortical areas (Kaliukhovich & Vogels, 2014;Kremlacek et al, 2007;Meyer, Ramachandran, & Olson, 2014;Motter, 2006;Mü ller, Metha, Krauskopf, & Lennie, 1999;Ramachandran, Meyer, & Olson, 2016; for a review, see Vogels, in press). Although the exact relationship of adaptation at different levels of the visual processing hierarchy to change detection as observed in vMMN studies (e.g., Kimura et al, 2011;Stefanics et al, 2014) is not clear, there is general agreement that the function of adaptation is to match response properties of the sensory system to the current environment (Clifford et al, 2007;Webster, 2011) and thus improve stimulus discrimination or detection of improbable stimuli (Benucci, Saleem & Carandini, 2013;Carandini & Heeger, 2012;Kohn, 2007;Solomon & Kohn, 2014;Wark, Lundstrom, & Fairhall, 2007).…”

Shift toward prior knowledge confers a perceptual advantage in early psychosis and psychosis-prone healthy individuals

“…The current study tests this hypothesis in the visual domain by characterizing the impact of prior knowledge on the perception of ambiguous stimuli in two groups of people: a clinical group with early psychotic experiences (study 1) and healthy volunteers showing differing levels of proneness to such experiences (study 2). Although the conventional view focuses preferentially on auditory hallucinations in psychosis, epidemiological evidence indicates that hallucinations in the visual domain are very common in, for example, schizophrenia (13). In fact, vision seems to play a prominent role in the development of psychosis given that basic visual symptoms identified before illness onset are one of the most powerful predictors of the emergence of later psychotic disorders (14).…”