The Cognitive Neuropsychology of Schizophrenia by Christopher D. Frith

Author:Christopher D. Frith
Language: eng
Format: mobi
Tags: Psychology
Publisher: Psychology Press
Published: 1992-08-31T21:00:00+00:00

84

5. POSITIVE SYMPTOMS, ABNORMAl EXPERIENCES

BRAIN SYSTEMS AND POSITIVE SYMPTOMS

85

DOES A SINGLE COGNITIVE DEFICIT

There have been many inconclusive studies in which associations

UNDERLIE ALL POSITIVE SYMPTOMS?

have been sought between symptoms or diagnosis and specific locations

of brain damage. A frequent, if not perseverative theme in this book is

This self-monitoring theory was originally developed to explain

that this search for associations will not be fruitful. Relations are more

delusions such as thought insertion and alien control. However, it can

likely to be found if we consider cognitive processes rather than

also explain certain auditory hallucinations, particularly "hearing one's

symptoms. I have suggested that one cognitive process likely to be

own thoughts spoken aloud" (Example 5.1 c). Indeed, my formulation of

relevant to positive symptoms is that by which we become aware of our

a self-monitoring defect has much in common with Richard Bentall's

own intentions. I shall therefore consider some neurological patients in

(1990) proposal that auditory hallucinations reflect a defect in reality

whom this process seems to be impaired.

discrimination. Bentall proposes that hallucinations arise because the

patient does not distinguish between external stimuli and internally

Action Without Awareness

generated thoughts and memories. Thus a single cognitive defect can

explain some hallucinations and some delusions.

Delusions of control refer to experiences in which the patient feels that

However, there are still aspects of both hallucinations and delusions

their thoughts, acts or emotions are being controlled by external forces

that these formulations do not explain very well. For example, if

rather than by their own will There is one neurological phenomenon,

.

hallucinations are our own thoughts perceived as coming from an

the alien hand sign, in which the patient actually performs unintended

external source, why do these thoughts sometimes take the form of

acts. Goldberg et al. (1981) have described two of these cases and propose

commentaries about us in the third person (Example 5.1 b)? Why should

that they are usually associated with unilateral damage to the medial

lack of awareness of our own intentions lead to delusions ofpersecution?

frontal lobe, most probably the supplementary motor area The alien

Even within the domain of self-monitoring, it seems unlikely that the

hand sign is a disconnection syndrome in which the hand opposite to

same system of corollary discharge would relate equally to limb

the lesion shows motor perseveration, forced grasping and apparently

movements as to speech acts. In Chapter 7 I shall suggest that

purposeful behaviour without conscious volition or knowledge on the

self-monitoring is a special case of a more general cognitive process that

part of the patient. Patients find the behaviour of their "alien hand" very

has a special role in conscious awareness. I shall propose that all

disturbing and often hold it down with their other good hand to prevent

schizophrenic symptoms can be explained in terms of various defects in

its movements, rather as Dr Strangelove held his artificial arm in

this process.

Stanley Kubrick's film.

The alien hand sign has two abnormal components. First, the alien

hand performs acts in situations where such acts do not normally occur.

THE BRAIN SYSTEMS ASSOCIATED WITH

Second, the patient is not aware of the intended or actual actions of the

POSITIVE SYMPTOMS

hand, unless actually looking at the hand. I believe that the movements

Patients with signs and symptoms meeting all the criteria for

of the hand are directly elicited by irrelevant stimuli.

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