Elsevier

Biological Psychiatry

Volume 43, Issue 5, 1 March 1998, Pages 348-357
Biological Psychiatry

Original Articles
Cognitive Deficits in Obsessive–Compulsive Disorder on Tests of Frontal–Striatal Function

https://doi.org/10.1016/S0006-3223(97)00201-1Get rights and content

Abstract

Background: Although neuropsychological and neuroimaging studies of obsessive–compulsive disorder (OCD) have implicated the frontal cortex and subcortical structures in the pathophysiology of the disorder, few studies have examined cognitive function in patients with OCD on tasks validated in the assessment of frontal lobe and subcortical dysfunction.

Methods: The accuracy and latency of executive and visual memory function was assessed in 23 nondepressed OCD patients and 23 normal healthy controls matched for age, sex, education, and estimated IQ.

Results: The patients with OCD performed within the normal range on tasks of short-term memory capacity, delay dependent visual memory, pattern recognition, attentional shifting, and planning ability; however, specific cognitive deficits related to spatial working memory, spatial recognition, and motor initiation and execution were observed in the patient group. These deficits were not correlated with aspects of the patients’ intellectual functioning or comorbid psychological symptoms, suggesting that the impairments were related to the specific clinical features of OCD.

Conclusions: Patients with OCD showed specific cognitive deficits on tasks of executive and visual memory function. The pattern of impaired performance in these patients was qualitatively similar to the performance of patients with frontal lobe excisions and subcortical pathology on the same test battery, suggesting that the underlying pathophysiology of the disorder could best be conceptualized as reflecting dysfunction of frontal–striatal systems.

Introduction

The clinical presentation of obsessive–compulsive disorder (OCD), with its repetitive, intrusive thoughts and stereotyped behaviors, has prompted recent research to examine the integrity of brain functions in the disorder. The frontal cortex and striatum have been consistently proposed as possible sites of dysfunction in OCD, based on observations of obsessive and compulsive symptoms among patients with lesions of the frontal cortex and patients with neuropsychiatric diseases preferentially involving subcortical structures (Frankel et al 1986; Wise and Rapoport 1989; Swedo et al 1989; Cummings and Cunningham 1992; Cummings 1993). Although the findings of functional neuroimaging studies have been generally inconsistent regarding specific patterns of abnormal cerebral metabolism in OCD, abnormal activation of the caudate nucleus and regions of the prefrontal cortex have been consistently reported (Martinot et al 1990; Sawle et al 1991; Lucey et al 1995; Perani et al 1995; Rubin et al 1995).

The results of neuropsychological studies of OCD have also been inconsistent, with no predominant cognitive deficit found to be associated with the disorder; however, methodological issues such as the use of large test batteries to assess small numbers of subjects, inadequate matching of patient and control groups, and the failure to control for comorbid depressive and anxiety illnesses that are commonly found in patients with OCD may have limited these studies (see Otto 1992). Of the cognitive studies of OCD conducted to date, several have reported deficits in attentional set shifting ability, response inhibition, and trial and error learning (Behar et al 1984; Malloy 1987; Head et al 1989; Martinot et al 1990; Veale et al 1996). Other studies, however, have failed to replicate these findings, and instead have reported deficits in visual memory and visuospatial ability (Boone et al 1991; Zielinski et al 1991; Christensen et al 1992). Several recent studies have also reported that patients with OCD perform timed cognitive tasks significantly slower than matched controls, although the accuracy of responses on these tests is usually within normal limits (Christensen et al 1992; Martin et al 1995; Galderisi et al 1995; Veale et al 1996).

The poor performance of patients with OCD on tasks of executive function and the observation of response slowing in this group may provide converging evidence for dysfunction of frontal and subcortical systems in the pathophysiology of the disorder. To systematically assess whether the neuropsychological deficits associated with OCD can be taken to reflect frontal–striatal dysfunction, it is appropriate to examine the cognitive performance of OCD patients on tasks previously found sensitive to the integrity of frontal and subcortical systems. The objective of this study was to examine the cognitive functioning of a group of patients with OCD and a group of matched, normal controls on a computerized neuropsychological battery that has been shown to discriminate the performance of patients with cortical and subcortical pathology, including those with Parkinson’s disease and progressive supranuclear palsy (Robbins et al 1994a; Owen et al 1992, Owen et al 1995a), frontal lobe, temporal lobe, and amygdala–hippocampal lesions (Owen et al 1990, Owen et al 1991, Owen et al 1993, Owen et al 1995b), and cortical dementias (Sahakian et al 1990; Sahgal et al 1991).

Section snippets

Subjects

Twenty-three patients with OCD and 23 normal controls participated in the study. The OCD patients were attending the University of Melbourne/Royal Melbourne Hospital Psychology Outpatient Clinic, or were inpatients in the hospital Psychiatry ward. Twenty-one patients presented with mixed obsessive and compulsive symptoms, 1 patient presented only with obsessional symptoms, and 1 experienced only compulsive phenomena. The patient and control groups were matched according to age, sex, education,

Results

The results of the analyses for each cognitive task are summarized in Table 2. There were no significant group differences on the measures of spatial span, delayed matching to sample, pattern recognition, attentional set shifting, Tower of London planning accuracy, or Tower of London thinking times; however, performance on the spatial working memory task differed between the groups. Fig. 1 shows the mean between-search errors for each group according to the difficulty level of the task. There

Discussion

The results of this study demonstrate that, in comparison with age-, sex-, education-, and NART-IQ-matched controls, patients with OCD show a specific pattern of cognitive deficits related to spatial working memory, spatial recognition, and motor initiation and execution. In contrast, on tasks of short-term memory capacity, delay dependent visual memory, pattern recognition, attentional set shifting, and planning ability, the patients performed within normal limits. Though patients with

Acknowledgements

This research was supported by a Project Grant (no. 950599) to Dr. Kyrios and Dr. Pantelis from the National Health and Medical Research Council, Australia.

The authors wish to thank Matthew O’Brien for assistance with data collection.

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