Biomedical subjects

J N De Roach

Publications and source records attributed to J N De Roach.

5 recordsLinked to original sources

PubMed1992

Auditory P300 studies in schizophrenic subjects and their first degree relatives.

Nineteen subjects with schizophrenia, 6 subjects with related disorders (schizophrenic spectrum disorders (S.S.D.)), and 20 unaffected first degree relatives from a sample of schizophrenic pedigrees, together with 35 normal control subjects, had auditory P300 evoked responses measured, using the "odd-ball" paradigm for stimulation. Bipolar recording on the midline (CZOZ) and two contralateral sites (CZ-mastoid) was carried out. It was found that approximately 40% of schizophrenics/S.S.D.'s had abnormal P300 responses. Abnormalities were seen in latency, RMS response voltage and in the left side response--right side response cross correlation coefficient. Schizophrenics/S.S.D.s showed responses which were topographically different than those of normal controls. Significant left-side/right-side response voltage asymmetry was not observed. In our study, only 10% of unaffected relatives of schizophrenics/S.S.D.'s showed abnormal P300 responses.

Adolescent↗

PubMed1989

Neural networks--an artificial intelligence approach to the analysis of clinical data.

This paper describes an approach to the pattern recognition problem of categorizing evoked response waveforms, using that branch of artificial intelligence known as neural networking. A total of 19 subjects (38 eyes) were exposed to a reversing chequerboard pattern, and the resulting Pattern electroretinogram (PERG) recorded. This was repeated for each of the subjects at contrast levels of 75%,50% and 25%, with the resulting response becoming less pronounced as the contrast level was decreased. The subjects were also given an Arden contrast sensitivity test, and the resulting scores recorded for each eye. The averaged responses from each of the 3 contrast levels for each of the 38 eyes tested were used as the input to a computer simulated 3-input per neuron cascaded neural network. The output and weighting parameters for the individual neurons were then varied until the network was able to optimally classify the PERG results on the basis of the Arden contrast sensitivity scores. The neural network was thus taught to recognize patterns in the PERG responses in much the same way that an experienced clinician might. A second neural network was similarly taught to classify the PERG responses on the basis of a clinician's subjective rating of each of the responses.

Adult↗

PubMed1984

Dyslexia: saccadic eye movements.

This paper describes an extensive study of the parameters of saccadic eye movement in a group of 28 poor-reading children and a comparative normally reading group of 31 children. Ages ranged from 6.0 to 16.9 yr. Poor readers had normal intelligence but were lagging by at least two years in reading ability as compared to their peer age group. Parameters studied in refixation eye movements included saccadic latency, accuracy, velocity, and acceleration, as well as differences in latency for abduct and adduct movements. Shapes of saccades were also studied. It was shown that eye-movement performance in simple saccadic refixation was not distinguishably different for poor readers and normal readers, even though in reading, which requires higher processing, eye-movement characteristics are quite different. Maturational changes for various saccadic eye-movement parameters were also examined for the normal and poor reading groups.

Adolescent↗

PubMed1984

Smooth pursuit eye movements in normal and dyslexic children.

This paper describes a detailed study of horizontal eye movements associated with visual tracking of a smoothly moving target. Essentially all children, even at target velocities as low as 5 degrees/sec., show some saccadic eye movements superimposed on smooth tracking movements. Detailed analysis of pursuit eye-movements from a group of 26 poor readers and 34 normal controls (8 to 13 yr.) showed that about 25% of poor readers have an abnormally raised saccadic component in smooth pursuit. This suggests that studies of eye movements during tracking of smoothly moving targets at low velocity, combined with a quantitative approach to data analysis, may be useful for early detection of a significant proportion of poor-reading children.

Child↗

PubMed1984

A detailed study of sequential saccadic eye movements for normal- and poor-reading children.

This paper presents the results of an in-depth study of parameters characterizing sequenced saccadic eye movements for a group of dyslexic children and a comparative normal control group with ages in the range greater than 8.0 yr. and less than 13.0 yr. No parameters were statistically different for the two groups, which supports the findings of Brown, et al. and contradicts the findings of Pavlidis. Our results indicate that sequenced saccadic eye movements are not diagnostically useful for early detection of dyslexia.

Child↗