Anthony Beech

Further evidence of reduced cognitive inhibition in obsessive-compulsive disorder

Abstract The concept of cognitive inhibition is reviewed together with experimental evidence in both clinical and non-clinical samples. Two negative priming experiments are described in which obsessive-compulsive disordered (OCD) subjects are consistently distinguished from all other categories of anxiety disorder. In conjunction with previous work it is suggested that this differentiation becomes more apparent as the cognitive complexity of the experimental task increases. These results are interpreted as further evidence for reduced cognitive inhibition in OCD sufferers. Comparison is drawn between the current results and those of previous negative priming studies with non-clinical, high schizotype, and schizophrenic subjects. The implications of these findings for our understanding of OCD are discussed.

A further investigation of cognitive inhibition in obsessive-compulsive disorder and other anxiety disorders

Abstract Previous research has consistently demonstrated reduced negative priming effects in patients with obsessive-compulsive disorder (OCD) when compared with patients exhibiting other anxiety disorders (OAD). The current study investigates the processing of negative priming stimuli at different presentation speeds. In addition to comparing OCD and OAD subjects, the former group is subdivided into high and low compulsive checkers. Results indicate that the negative priming deficit in OCD subjects is limited to the fastest presentation speeds, though in checkers this deficit is also evident at longer presentation rates. These data are compared with previous research in the White Bears thought suppression paradigm with the same subjects. It is concluded that the results across these experimental paradigms are consistent and allude to a fundamental preattentive deficit of cognitive inhibition in OCD subjects generally and most significantly in OCD checkers.

The Cerebral Hemispheres and Bilateral Neural Nets

A high-level cognitive dichotomy (language and context) is reviewed in relation to empirical findings concerning the functions of the human cerebral hemispheres. We argue that the right hemispheres involvement in the generation of connotative and contextual information in parallel with the denotative and literal language functions of the left hemisphere provides an important insight into the organization of viable cognitive systems. The role of the corpus callosum in producing the dichotomy is discussed. Finally, the generation of asymmetrical activity in structurally symmetrical, bilateral neural nets is described. The model demonstrates how complementary memory states can be generated in bilateral nets without assuming different modes of information processing, provided that the nets have inhibitory, homotopic connections. Unlike excitatory connections, inhibitory connections are sufficient to generate asymmetric hemispheric activity without postulating intrinsic differences between the cerebral hemispheres.

The effect of a small dose of chlorpromazine on a measure of ‘cognitive inhibition’

Abstract A double-blind drug/placebo experiment was conducted investigating the action of chlorpromazine on ‘cognitive inhibition’ in normal subjects. It has been suggested that such inhibition is reduced in schizophrenics and may be part of the mechanism that gives rise to positive symptomatology, because of a failure to screen out irrelevant material from consciousness. It was found that chlorpromazine (a drug routinely administered to schizophrenics) increased this inhibitory effectsin normal subjects.

SCHIZOTYPY AND LATERALISED NEGATIVE PRIMING IN SCHIZOPHRENICS' AND NEUROTICS' RELATIVES

Schizophrenics relatives were compared with neurotics relatives on a range of schizotypy scales and a hemisphere information processing (negative priming) task. On most of the schizotypy scales schizophrenics relatives had lower scores than neurotics relatives, and also as compared with the normative data for the questionnaires used. This might have been due to volunteer bias or to defensive responding, though if the latter was the case it was not reflected in the level of ‘Lie’ scale scoring found among schizophrenics relatives. The experimental task showed no significant differences when subjects were compared according to relatives status. However, two significant differences did emerge when the total sample was divided on the basis of high/low schizotypy scores: high schizotypes showed (a) a lack of visual field asymmetry in lateralised negative priming, and (b) unusually fast overall reaction times to stimuli in the left visual field. Both observations are consistent with some recent speculations about hemisphere functioning as it relates to information processing and activation bias in schizophrenia and schizotypy.

Reversing priming while maintaining interference

The amount of interference and priming is examined in a Stroop color-naming task, in which distractors were either color words (conventional Stroop) or nonwords comprising the first two letters of the color words (color pseudowords). It was found that both color words and color pseudowords produced an interference effect, and that the amount of interference by these two types of stimuli was highly correlated across subjects. It was also found that color words led to a reaction time cost when distractor and subsequent target were the same, compared to trials on which no such relation existed. This was an instance of negative priming (Tipper, 1985). Conversely, color pseudowords led to positive priming and reaction time saving, under the same conditions. These data suggest that interference is related to the initial structural elements of the words, and that it may occur regardless of whether or not words can be fully analyzed, whereas priming effects may depend on whether it is possible to analyze the stimuli on a semantic level.

A questionnaire study of schizotypy in obsessional states and the other anxiety disorders

Abstract The Composite Schizotypy Questionnaire (CSTQ) was used to demonstrate that both clinical and non-clinical scales designed to measure schizophrenic-like (schizotypal) traits, clearly distinguished obsessive-compulsive disorder (OCD) from a heterogeneous group comprising of those with other anxiety disorders (OAD). The 3-and 4-factor solutions to the CSTQ were applied to the current data and indicated that OCD subjects were significantly different from OAD on all of these subfactors of schizotypy. Most significant were factors of positive psychotic symptoms and cognitive disorganization. The implications of these results are discussed in relation to previous experimental studies relating OCD to schizotypy, and to the diagnostic classification of OCD as an anxiety disorder.