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Biomedical subjects

A J North

Publications and source records attributed to A J North.

8 recordsLinked to original sources
PubMed1989

Visual and auditory coding confusability in students with and without learning disabilities.

The nature of visual and auditory coding processes in students with learning disabilities (SLDs) and student controls (SCs) was examined with a letter-matching task on four types of successively presented letter pairs: identical (A,A), visually confusable (P,R), auditorily confusable (F,S), and neither visually nor auditorily confusable (N,T). Two delay intervals (0 and 2 seconds) were used between the presentation of the first and second letters. Analysis of decision latencies on the nonidentical letter pair trials revealed that with initial exposure to the task, the SLDs responded more slowly than SCs, but their general confusability patterns (visual and auditory) were similar. With additional practice, overall decision latencies were comparable for the two groups, while confusability differences emerged: SCs showed maximal visual confusability at a 0-second delay and maximal auditory confusability at a 2-second delay, while SLDs did not. Evidently, SLDs make less extensive use of visual and auditory coding processes compared to SCs.

Attention↗
PubMed1988

The human locus coeruleus: computer reconstruction of cellular distribution.

Quantitative neuroanatomical techniques were developed to map the distribution of norepinephrine-containing locus coeruleus (LC) neurons in the adult human brain. These neurons reside in the dorsolateral pontine tegmentum and are identifiable by their neuromelanin pigment content. Five brains, ranging in age from 60 to 104 years, were examined. Outlines of coronal or sagittal sections containing the LC were entered into a computer along with the location of each cell, certain neuroanatomical landmarks, and cell size. Sections were aligned with specific neuroanatomical landmarks so that the computer-generated distribution of cells was representative of the in situ distribution of cells. Analysis of (1) the number of cells in sections throughout the rostrocaudal extent of the nucleus, (2) cell size, (3) 3-dimensional reconstructions of the distribution of cells within the brain stem, and (4) 2-dimensional cell-frequency maps, make it possible to quantitatively characterize the distribution of cells within this large nucleus. The total estimated number of LC cells on both sides of the brain ranged from 45,562 to 18,940 (youngest to oldest), and mean soma area ranged from 835 to 718 micron 2 (youngest to oldest). The nucleus is "tube-like" in shape, has a rostrocaudal extent of approximately 16 mm, and is bilaterally symmetrical. Two-dimensional cell-frequency maps were developed to illustrate the regional distribution of cell frequencies at any rostrocaudal/mediolateral point on the horizontal plane; the total unilateral area of the LC ranged from 32.8 to 17.2 mm2 (youngest to oldest). The techniques developed to characterize the 2- and 3-dimensional distributions of LC neurons can be used in future studies to quantitatively examine the effects of aging and disease on this and other brain nuclei.

Cell Count↗
PubMed1986

Discourse performance in older adults.

Thirty-three elderly women, whose mean age was 76.2 years, and eighteen middle-aged women, whose mean age was 45.6 years, were assessed on a number of linguistic discourse tasks. The women were well educated, and most of them were or had been engaged in the teaching profession. Each woman was given narrative discourse tasks involving recall of stories, summarizing stories, giving the morals of the stories, procedural discourse tasks, interview to assess cognitive functioning and communicative abilities, and the following cognitive tests: Block Design, Symbol-Digit, Raven Coloured Progressive Matrices, and Word Fluency. The findings were that the older group generally performed more poorly than did the middle-aged group on most of the discourse tasks and cognitive tests. Within the older group, measures of quality of discourse were generally negatively related to age and positively related to scores on cognitive tests.

Age Factors↗
PubMed1983

Production of procedural discourse in aphasia.

The abilities of a group of 15 moderately impaired aphasics and 15 normals to produce procedural discourse are described. The experimental tasks included producing four procedures of varying levels of complexity. The data were analyzed in terms of sentential grammar, discourse grammar, and subjective ratings of content and clarity of language. The results showed that aphasics produced well-structured discourse. The language of the aphasics' discourse was reduced in both complexity and amount, but was not qualitatively different from the language produced by the normals. The reduction of language in the procedures reflected selective reduction of hierarchically organized information. The investigation suggests that aphasics are capable of manipulating different types of information and that they might be helped in this by utilizing instrumental scripts which are representation of knowledge underlying procedures.

Adult↗
PubMed1983

Production of narrative discourse in aphasia.

The study described the abilities of a group of 15 moderately impaired aphasics and 15 normals to produce narrative discourse. The experimental tasks included telling stories, summarizing stories, and giving morals to stories. The data were analyzed in terms of sentential grammar, discourse grammar, and subjective ratings of content and clarity of language. The results showed that aphasics produced well-structured discourse. The language of the aphasics' discourse was reduced in both complexity and amount, as compared to that produced by normals. The reduction of language reflected selective reduction of hierarchically organized information. The findings of the study confirm the results of previous research on mildly impaired aphasics, which also showed preservation of discourse structure with selective reduction of information.

Adult↗
PubMedDate not supplied

Individual differences in cognitive functioning in the elderly - phenomena and interpretation.

Residents (N = 27) of a Jewish home for the aged were given a battery of twenty-five tests of cognitive abilities. Participants included people carrying a diagnosis of organic brain syndrome. Subsets of tests were designed to measure immediate sequential memory, ability to handle categories, and ability to execute motor patterns. There were marked individual differences among participants. Poorer performance was associated with carrying a diagnosis of organic brain syndrome and with a number of other background variables. There was empirical evidence that immediate sequential memory and ability to handle categories can be discriminatively measured. A wide variety of qualitative behavioral phenomena was described. The findings were interpreted in terms of an information-processing model.

Aged↗
PubMedDate not supplied

[Use of discourse analysis for evaluation of the condition of patients with dementia of the Alzheimer type].

The study was concerned with the ability to discourse in a group of 10 patients with minor or moderately severe disturbances in Alzheimer disease and in a control group of healthy subjects. The aim the study was to answer the question whether patients with this disease have language deficits, and if they have, then at what level they appear and what is their influence on the communication ability. The experimental task included production of a narrative and a procedural discourse. The results were analysed from the standpoint of grammar of clauses and their informative contents. The analysis showed that the patients had no deficit in respect to the extent of the discourse, its complexity and grammar correctness. However, errors were found in the contents of the discourse. In particular, the discourse of the patients had a greater number of irrelevant and incorrect propositions. The possible explanation of the demonstrated deficit pattern is discussed stressing the importance of progmatic and cognitive factors. The conclusion is that language disorders in these patients should not be regarded as a type of aphasia.

Aged↗