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Biomedical subjects

D J Crockett

Publications and source records attributed to D J Crockett.

At least 19 recordsLinked to original sources
PubMed1992

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.

Attention↗
PubMed1991

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.

Artificial Intelligence↗
PubMed1990

Birth weight and pathogenesis in phenylketonuria.

The birthweights of an ethnically homogeneous sample of infants with phenylketonuria, their unaffected siblings, and control infants were compared after adjusting for the effects of: mother's age, mother's date of birth, mother's height and obstetric history, the length of gestation, the infant's sex, the place and date of birth. There were no significant differences between the infants with phenylketonuria and their unaffected siblings either in adjusted or unadjusted birthweights. Control infants had slightly, but statistically significant, greater adjusted and unadjusted birthweights than the combined phenylketonuria and unaffected sibling groups. This effect of the phenylketonuria gene is a previously unreported finding but unlikely to be related to the pathogenesis of phenylketonuria. Our results do not provide support for the "justification" hypothesis that the mental and neurological defects in phenylketonuria result from prenatal tyrosine deprivation which would be reflected in lower birthweights.

Birth Weight↗
PubMed1990

Differences in neuropsychological performance in psychiatric, anterior- and posterior-cerebral dysfunctioning groups.

The neuropsychological performance of psychiatric, anterior- and posterior-cerebral dysfunctioning groups was compared using both raw scores and scores statistically adjusted for the effects of age, education, gender, and overall level of intellectual functioning. Between 5% and 37% of the variance of the subtests of the WAIS-R and between 9% and 58% of the variance associated with the neuropsychological variables was accounted for by the demographic variables. Using raw scores, ten of the twenty-five tests showed significant overall differences among the groups, while only five of the contrast using adjusted scores were significant. Anterior- and posterior-cerebral dysfunctioning groups generally were significantly more impaired than the psychiatric group. Memory and problem-solving variables were the most sensitive to the removal of demographic variance, while psychomotor test scores were the most robust. Differences among cerebrally impaired and psychiatric groups may be obscured by demographic variables or levels of general intellectual functioning.

Analysis of Variance↗
PubMed1989

Neuropsychological "systems efficiency" and positron emission tomography.

Positron emission tomography (PET) has dramatically improved our ability to examine the functioning of the living brain. PET studies of neural pathways of the major sensory modalities--auditory, visual, somatosensory--have confirmed many traditional neuropsychological concepts, such as cross-lateral representation and regional functioning to particular primary sensory cortical areas. Other PET studies have used radioisotopes to examine relationships between radiopharmaceutical agents and neurobehavioral functioning in both normal and neuropathological states. In some areas, PET methodology requires further refinement. For example, effort should be made to develop the technology to do multiple scans within a short time frame; statistical procedures to examine relationships between neuropsychological tasks and the activity or presence of radiopharmaceutical agents in multiple sites; adequate controls for experimental error; and activation paradigms controlling the nonspecific effects of simple arousal. PET activation models of cognition suggest that a "systems efficiency" approach to assessing neuropsychological test performance involving both serial and parallel processing would be useful. These developments will improve empirical methodology and our understanding of brain-behavior relationships.

Arousal↗
PubMed1986

A comparison of treatment modes in the management of myofascial pain dysfunction syndrome.

This research compares different treatment regimes for the management of chronic facial pain associated with the masticatory musculature. Twenty-one females meeting specific criteria were randomly assigned to one of three treatment conditions: a dental splint and physiotherapy program; a relaxation program utilizing progressive muscle relaxation, biofeedback, and stress management techniques; or a minimal treatment program involving transcutaneous electrical nerve stimulation. Improvement was assessed through a dental examination, self-monitoring of pain, and an assessment of EMG activity during resting and task conditions. Significant changes were obtained in response to all treatment programs. The treatment programs differed only in the relative pattern of treatment effects obtained from the self-report monitoring of pain. The data are consistent with the concept of MPD as a psychological response to stress which maintains chronic pain through increased muscle tension in the jaw.

Biofeedback, Psychology↗
PubMed1986

Social influences on factored dimensions of the McGill Pain Questionnaire.

The McGill Pain Questionnaire (MPQ) was administered to 268 subjects following electrical stimulation to pain-tolerance limits. Subjects received stimulation under four social modeling conditions: tolerant, intolerant, control, and no model. The number of factors and degree of obliqueness most appropriate for the MPQ scores were determined using multiple criteria. Five factors, reflecting 46.6% of the total variance, were derived and labelled as follows: affective-arousal, sensory-pressure, perception of harm, somesthetic pressure, and cutaneous sensitivity. The various modeling conditions did not produce any significant between-group differences on the factors. The repeated demonstration that the MPQ assesses substantially more than the three components originally proposed suggests that considerable caution is warranted with respect to using the 'sensory-evaluative-affective' method of scoring this test. Considered in relation to previous research, the present findings are consistent with the conclusion that social influences affect fundamental components of subjective reactions to pain.

Electroshock↗
PubMed1985

Treatment of burns casualties after fire at Bradford City football ground.

On 11 May 1985 the main stand of Bradford City Football Club caught fire. Within four minutes the stand was alight from end to end. Fifty three people were burnt to death and about 250 injured; 83 required admission to hospital, and 55 of these were treated by primary excision of their burns and skin grafting. In such disasters the help of staff from other hospitals and areas is essential. Patients should be assessed to see whether they have burns that will ultimately be fatal; if they have they should not be sent to regional burns units, where they would take up beds that could be used for patients with treatable burns. All districts should ensure that their plans for accidents in which burns injuries predominate are adequate.

Adult↗
PubMed1985

Use of background interference procedure to assess visual retention deficits in multiple-sclerosis, psychiatric, and brain-damaged patients.

The performances of three groups of patients were compared during two conditions of interference on a visual retention task. During the noninterference condition, the psychiatric, multiple-sclerosis, and brain-damaged patients functioned at a comparable level. The introduction of a distracting background reduced the level of functioning for only the brain-damaged group. This effect remained significant for the correct score when age and postmorbid intelligence functioning were controlled. These results were interpreted as reflecting the cortical nature of the deficits in resisting the distracting influence of the background interference procedure. Serial testing was recommended for the evaluation of the multiple-sclerosis group.

Brain Damage, Chronic↗
PubMed1977

A comparison of empirically derived groups of aphasic patients on the Neurosensory Center Comprehensive Examination for Aphasia.

Rating scales were used to identify characteristic aphasic phenomena in a sample of natural language from aphasic patients. These variables were used to derive empirically four groups of aphasic patients. These groups showed significant multivariate differences on the basis of their performance on the Neurosensory Center Comprehensive Examination for Aphasia. Seven subtests showed significant univariate differences among the four groups: Visual Naming, Description of Use, Sentence Repetition, Repetition of Digits, Reversal of Digits, Identification by Sentence, and Oral Reading Sentences. Two of the groups reflected Howes dichotomy of articulate-nonarticulate language disorders. Another group was thought to reflect Schuell's single dimension of language disorders that could be differentiated only in terms of severity. Afourth group was characterized by a major impairment of memory. These results indicated that aphasic phenomena could be identified reliably on the basis of rating of verbal output on scales that reflect language disorders. These scales were used in a statistical fashion to derive empirically oriented groups that were identified on the basis of psychometric measures of language skills.

Adolescent↗
PubMed1977

Assessment of prognosis in cutaneous malignant melanoma.

A retrospective study of 103 patients with histologically proved cutaneous malignant melanoma was made in order to assess the validity of a simple prognostic index, based upon a multivariate analysis of weighted pathological and clinical factors, in predicting the expected outcome in a given case. The results of the study were almost identical to those observed by Cochran (1968); 16 per cent of the patients with a low prognostic index (less than 20) died or developed recurrence of melanoma during the period of follow-up, in contrast to those with a high prognostic index (greater than 25) of whom 64 per cent were similarly affected. It is concluded that the predicted outcome based upon such an index is valid for the 5 postoperative years in some 90 per cent of patients with cutaneous malignant melanoma. It is suggested that the use of such an index may be of great value in selecting patients in whom the expected outcome to surgical therapy is poor and in whom adjuvant therapy may be of value.

Female↗
PubMed1976

Multivariate comparison of Howes' and Weisenburg and McBride's models of aphasia on the neurosensory center comprehensive examination.

The verbal production of 57 aphasic patients was rated and used to assign these patients into two sets of groups reflecting Howes' and Weisenburg and McBride's models of aphasia. Test scores covering a broad range of communication skills and modalities were compared between these groups to examine the assumption that salient features of verbal production could be used to establish groups which would show significant differences on other important linguistic variables. Neither Howes' nor Weisenburg and McBride's model provided groups showing significant multivariate differences. It was suggested that these models be improved by expanding them to include other important psycholinguistic components of language skills. Since these models did not account for significant between group differences, caution was suggested in using these models for assessment or treatment purposes.

Adolescent↗