The Neuroscience of Visual Hallucinations

Daniel Collerton

• Publisher: Wiley-Blackwell
• Year: 2014
• Print ISBN: 9781118731703
• eBook ISBN: 9781118892800
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Neuroscience
• Index: Biological Sciences

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.

Section 1
Background and Context

Chapter 1
Visual hallucinations: history and context of current research

G.E. Berrios¹ and Ivana S. Marková²

¹Department of Psychiatry, University of Cambridge, Cambridge, UK

²Centre for Health and Population Sciences, Hull York Medical School, University of Hull, Hull, UK

1.1 Introduction

‘Visual hallucination’ is the name of a class of heterogeneous phenomena which share as a common feature the report that a subject (the ‘hallucinator’) is entertaining a putative ‘visual’ image of something placed in the public space that others cannot see. Hence ‘absence of an object to be seen’ has become part of its conventional definition. ‘Images’ may range from simple dots to complex forms in movement. This chapter will deal only with the latter. The hallucinator's report can be interpreted as meaning that he is entertaining a visual image or that he only believes that he is so doing, as it might well be the case with psychotic or obsessional hallucinations (Castilla del Pino, 1984; Gimenez, 2000; Fuentenebro and Berrios, 2000).

Disambiguating such reports is not always straightforward. On occasions, it can be reasonably claimed that proxy representations of the image in question can be ascertained by technical means (e.g. neuroimaging) as may well be the case in regard to so-called ‘organic’ or ‘provoked’ visual hallucinations (Berrios, 1985; Manford and Andermann, 1998; ffytche, 2007). However, when the proxy representations are counter-intuitive and merely correlational, that is, when changes do not seem to be related to those brain regions obviously associated with visual perception (as it seems to be the case with some visual obsessional or psychotic hallucinations) (Boksa, 2009) then disambiguation becomes problematic. The possibility that the hallucinator is only expressing the belief that he is entertaining a visual image cannot be easily dismissed (Castilla del Pino, 1984; Gimenez, 2000).

Therefore, it is likely that the class ‘visual hallucinations’ is but a mixture of clinical phenomena which are different from each other, both from the phenomenological and aetiological point of view. Indeed, this was the way they were perceived until the ‘unitary’ view was first proposed during the early nineteenth century (Berrios, 1996). Historical accuracy requires that two ‘unitary views’ are distinguished: UV1 refers to the view that ALL hallucinations, regardless of their sense modality, are structurally the same phenomenon; and UV2 refers to the view that all visual hallucinations, regardless of the disease in which they appear, are the same phenomenon. Ever since UV1 and UV2 became the official view, voices have been raised against them (for a detailed analysis of this literature see: Ey, 1957, 1973; Lanteri-Laura, 1991).

Before the nineteenth century there was no unitarian view of visual hallucinations (UV2). Visions, apparitions, phantoms, fantasies, imaginings, contemplations, supernatural insights and so on were all conceptualized as different phenomena in their own right (Tyrrell, 1943; Green and McCreery, 1975; Berrios, 2007). Some of them were considered to be pregnant with meaning to represent forms of communication between god, unknown forces and man or between men themselves. By the early nineteenth century, in what became the scientific approach to hallucinations, these experiences were shelled out of all semantic content, lumped together and treated as mechanical ‘disorders’ of the brain. Although the semantic view of hallucinations still lingers on, both in folkloric Western psychology and in some non-Western cultures, it cannot be said to have the force of the scientific view.

The current general concept of hallucination and that of visual hallucination were both constructed during the early nineteenth century (Ey, 1939; Berrios, 1996). Although there have since been debates on their aetiology, the conventional assumption remains that hallucinations in general are a disorder of perception (Berrios and Marková, 2012), and the same applies, mutatis mutandi, to visual hallucinations. This has made debates on the nature of visual hallucination dependent upon changing theories of visual perception (Hamlyn, 1961).

It remains to be seen whether UV2 should be considered epistemologically superior to earlier views, that is, whether it is more helpful both to the understanding and management of these phenomena. This can only be decided by empirical research. Unfortunately, no one seems interested in carrying out studies comparing UV2 against earlier taxonomic and aetiological views of visual hallucinations.

By the end of the nineteenth century, the current ‘operational’ definition had been put together (Berrios, 2005). Visual hallucinations: (i) were to be defined as reports of real visual images of unascertainable public objects − not of the belief that the person was experiencing an image and (ii) which regardless of their phenomenology or clinical associations resulted from pathological changes in the visual system. Agencies external to the body (such as spirits or ghosts) were no longer to be considered as part of the explanatory model. ‘Personality’ and ‘culture’ were allowed within the explanatory model but only to account for the ‘content’ of the visual hallucination (i.e. thus according to their ‘culture’, hallucinators may see a devil, a dragon or whatever).

From the above, at least three conclusions can be drawn:

1. The phenomena currently called ‘visual hallucinations’ do not seem to be ontologically stable ‘natural kinds’ but will-o'-the-wisp phenomena, which in each historical period have been configured in a different way.
2. To ‘understand’ these phenomena properly (and hence to manage them) a set of tools is required, which may be more complex than any offered by the neurosciences and,
3. To discharge their brief, we will need to sketch the history and epistemology of: (i) visual hallucinations and (ii) the social activity called ‘research’ and explore their historical interactions.

Historical analysis shows that UV2 has become a hindrance to the understanding of visual hallucinations. Exploring their neuro-mechanics or mapping them in the current language of cognitive neuropsychology is bound to be insufficient. Per contra, this chapter will put forward the view that: (i) before empirical research starts in earnest much work on the clinical phenomenology and taxonomy of visual hallucinations needs to be done and (ii) a new taxonomic approach will show that ‘visual hallucinations’ names a rag bag of heterogeneous phenomena, each of which will require a different aetiological account. Lastly, because subjects suffering from these clinical afflictions may need direct clinical intervention, conceptual and ethical auditing become particularly important in this type of research.

1.2 The construction of visual hallucinations

1.2.1 History

The history of visual hallucinations can be broken up into four periods. The first period extends from Classical times to the beginning of the nineteenth century (Berrios, 1996). At that point, a physiological period started in the work of Johannes Müller (Berrios, 2005). A hermeneutic period developed after the 1850s and is characterized by wo...

Table of contents

• Cover
• Title Page
• Copyright
• List of contributors
• Foreword
• Section 1: Background and Context
• Section 2: Investigations and Data
• Section 3: Models and Theories
• Section 4: New Directions
• Index
• End User License Agreement