David J. Crockett

The structure of posttraumatic stress symptoms.

Posttraumatic stress disorder, as defined by the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev. and 4th ed.; American Psychiatric Association, 1987, 1994, respectively), is characterized by 17 symptoms, descriptively clustered into 3 groups: (a) intrusions, (b) hyperarousal, and (c) avoidance and numbing. The present study sought to identify the basic dimensions (factors) that underlie these symptoms. Two samples were assessed: 103 victims of motor vehicle accidents and 419 United Nations peacekeepers deployed in Bosnia. A principal axis factor analysis was conducted for each sample. In each sample, 2 correlated factors were obtained, which were very similar across samples. Factor 1 was labeled Intrusions and Avoidance, and Factor 2 represented Hyperarousal and Numbing. These factors loaded on a single higher order factor. The higher order factor accounted for 13% to 38% of variance in symptom severity, and the lower order factors accounted for an additional 8% to 9% of variance. If the authors assume that each factor corresponds to a distinct mechanism (R. B. Cattell, 1978), then the results suggest that posttraumatic stress reactions arise from a general mechanism, with contributions from 2 specific mechanisms.

Anxiety sensitivity, trait anxiety, and the anxiety disorders

Abstract The recent debates and commentaries about the construct validity of the Anxiety Sensitivity Index (ASI) suggest several issues that remain to be resolved. First, the factor structure of the ASI remains to be clarified. Second, the distinction between this instrument and measures of trait anxiety has yet to be elucidated. A third issue concerns the extent to which the ASI and the trait version of the State-Trait Anxiety Inventory (STAI-T) can discriminate between panic disorder and other anxiety disorders. These issues were investigated by administering the ASI and the STAI-T to 142 spider-phobic college students and 93 psychiatric outpatients. In both samples, the ASI was found to be unifactorial. When the pool of ASI and STAI-T items was subjected to a factor analysis with oblique rotation, both samples yielded a two-factor solution. The STAI-T items were responsible for almost all the salient loadings on the first factor, and the ASI items were responsible for almost all the salient loadings on the second factor. In both samples the correlation between the factors was .39. These results suggest that the ASI is not simply a measure of trait anxiety. Items that are particularly important in defining the ASI concern the fear of bodily sensations. Fear of the social consequences of anxiety played a minor role in this factor. Panic-disordered patients were differentiated from patients with other anxiety disorders by ASI items pertaining to fear and catastrophic misinterpretation of bodily sensations. The full-scale score and item responses of the STAI-T were unable to differentiate between the anxiety groups. The findings support the construct validity of the ASI and the recent cognitive models of panic disorder. The results also suggest that a three-item version of the ASI may be used for the diagnosis of panic disorder.

Conceptualizations of anxiety sensitivity

Anxiety sensitivity (fear of anxiety) is thought to play an important role in the development and maintenance of anxiety disorders. One of the most widely used measures of anxiety sensitivity is the Anxiety Sensitivity Index (ASI). The originators of this scale regarded it as a measure of a undidimensional construct (Reiss et al., 1986). Recent investigations have challenged this claim, and several 4-factor solutions have been proposed. If the dimension(s) of this scale are to guide theory and research, then it is necessary to determine the most stable factor structure. ASI responses were obtained from 142 spider-phobic college students and 327 psychiatric patients presenting with anxiety or stress-related (psychophysiological) disorders

Clinical utility of three measures of frontal lobe dysfunction in neuropsychiatric samples

The utility of the Word Fluency Test, Wisconsin Card-Sorting Test, and a shorter form of the Categories Test as screening instruments for detecting frontal lobe dysfunction in a neuropsychiatric setting was examined. On the basis of clinical and neurological examination, patients were assigned to one of three groups: frontal lobe injured, brain impaired excluding the frontal areas, and psychiatric with no evidence of brain dysfunctioning. It was possible to assign correctly 66.3% of the patients to their respective groups. The Word Fluency Test made the strongest contribution to the prediction of the presence of frontal lobe pathology, even when the effects of age and postmorbid intellectual functioning were controlled. The results were consistent with the interpretation of lowered verbal fluency and deficits in the capacity to suppress habitual behaviour as a major feature of frontal lobe dysfunctioning.

Cued recall and memory disorders in dementia

Memory functioning of normal elderly subjects and patients with suspected malignant memory disorders were examined using a cued recall memory assessment procedure. Levels of psychosocial functioning were rated by a multidisciplinary team. Ability to engage in free and cued recall was studied to determine the relationship between problems of acquisition and retrieval. Normal and impaired elderly showed strong differences on free recall and total recall resulting in 90.58% and 79.06% rates of accuracy of prediction of group membership. There were significant multivariate and univariate differences among the memory-impaired groups defined in terms of their psychosocial functioning. These findings indicate that differences in acquisition and retrieval are associated with increasing impairment of psychosocial functioning. Patients whose psychosocial functioning was rated as falling within the questionable range exhibited only deficits in retrieval. Patients whose psychosocial functioning was rated as more severely impaired, exhibited problems of retrieval and acquisition.

Central cholinergic deficiency wais profiles in a nondemented aged sample

Fuld (1984) described a WAIS profile associated with drug-induced cholinergic deficiency in young adults and dementia of the Alzheimers type. The frequency of occurrence of this profile was examined in a group of healthy elderly persons who were administered the WAIS. The results of this study suggest that the profile occurs rarely in independently functioning elderly persons, thus lending support to Fulds findings that the profile may be relatively specific to dementia of the Alzheimers type. Hypotheses as to the significance of this index of pathology are discussed.

Empirically derived groups in the assessment of recovery from aphasia.

Abstract This paper examines the pretreatment intercorrelation matrix of the subtests of the Porch Index of Communication Ability to derive factors reflecting components of language impairment. In addition to a general factor reflecting overall language dysfunction, five specific factors reflecting verbal competency (fluency), graphic-verbal expression, gestural-verbal expression, gestural-nonverbal comprehension, and graphic-geometric comprehension were found which accounted for 90.6% of the total variance. A cluster analysis of the five pretreatment factor scores yielded six groups which accounted for 79% of the variance for these factors. These groups were differentiated primarily in terms of impairment and showed a high rate of accuracy prediction for group membership (97.5%). These groups were extremely stable, as shown by the 75% accurate prediction rate derived from the post-treatment factor scores. The effectiveness of this model in generating homogeneous and highly discriminable groups based on objective measures of the patients language functions indicates that classification of patients into empirical groups should be a major concern of any research design. Implications for assessing effectiveness of therapeutic intervention and the design of test battery were also discussed.

Parallel distributed processing and neuropsychology: a neural network model of Wisconsin Card Sorting and verbal fluency.

Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.

Severity of Impairment or Specific Types of Aphasia: An Empirical Investigation

This study examined empirical means of clustering aphasic patients into relatively homogenous and identifiable groups. The method included: (1) examining the intercorrelations of the subtests of the Neurosensory Comprehensive Examination for Aphasia by the means of factor analysis; (2) allowing the subjects to group themselves in homogenous subgroups by means of hierarchical cluster analysis; and (3) comparing the profiles of these groups on the derived dimensions. Four factors accounting for 79.3% of their total test variance were derived which reflected attention/memory; reading ability; verbal-naming ability; and elementary writing skills. With five groups the hierarchical grouping analysis indicated that only 21.5% of the total variability could be ascribed to within group variability. An analysis of variance of the four factor scores found that 66%, 93%, 81% and 79% of the between group variance of each of the respective factors was associated with group membership and the accuracy of membership prediction was 94.1%. Four groups appeared to be distributed on the basis of a severity model of impairment. One group representing 6.3% of the total sample demonstrated a pattern of specific impairment involving a mild level of impairment on attention/memory tasks, a moderate level of impairment on verbal naming tasks and writing skills, and a profound level of impairment on measures of reading skills. The high inter-factor correlations indicated the general nature of language functioning. The results were discussed in terms of the concept of aphasia as a general cognitive deficit.

Parallel Distributed Processing and Neural Networks: Origins, Methodology and Cognitive Functions

Parallel Distributed Processing (PDP), a computational methodology with origins in Associationism, is used to provide empirical information regarding neurobiological systems. Recently, supercomputers have enabled neuroscientists to model brain behavior-relationships. An overview of supercomputer architecture demonstrates the advantages of parallel over serial processing. Histological data provide physical evidence of the parallel distributed nature of certain aspects of the human brain, as do corresponding computer simulations. Whereas sensory networks follow more sequential neural network pathways, in vivo brain imaging studies of attention and rudimentary language tasks appear to involve multiple cortical and subcortical areas. Controversy remains as to whether associative models or Artificial Intelligence symbolic models better reflect neural networks of cognitive functions; however, considerable interest has shifted towards associative models.