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Biomedical subjects

G Leisman

Publications and source records attributed to G Leisman.

12 recordsLinked to original sources
PubMed1978

Aetiological factors in dyslexia: I saccadic eye movement control.

A study was performed to examine the character of saccadic eye movement in dyslexic and normal children and normal adults. No significant differences were noted between 20 normal and 20 dyslexic children, but significant differences were noted between both groups of children and the adult population. Results were explained as reflecting no measured difference in duration/amplitude and velocity/amplitude functions in dyslexic and normal children, thereby indicating no differences in their saccadic eye-movement control functions. Observed differences between normal adult and child populations are explained.

Adolescent↗
PubMed1978

Aetiological factors in dyslexia: II. ocular-motor programming.

A study is presented in which the preprogramming of saccadic eye movements is examined in normal (16 boys, 4 girls) and dyslexic subjects (19 boys, 1 girl), as well as the patterning of occular-motor differences between subjects, which is consistent with the previous study in which no differences in saccadic control are demonstrated between groups of subjects.

Child↗
PubMed1977

Return sweep latency in reading with a paralyzed eye.

The study concerned the distribution of directional control of eye movement in reading. With the paralysis of the right eye, progressive movements of the left eye were possible, but regressive movements were cancelled, being observed as drift. Base-out prism placed over the non-paralyzed eye allowed for the re-establishment of regressive movements. The results for this subject were explained on the basis of a large retinal error marker having been established. With the paralysis of one eye, base-out prisms reduce that error.

Eye Movements↗
PubMed1977

Ocular-motor effects on the human electroencephalogram.

In response to the findings that gross vertical and horizontal eye deviation can be associated with facilitation of the human EEG alpha rhythm, an hypothesis is suggested that the deviation of gaze which exceeds a critical angle and results in a loss of subjective ocular stability is related to the occurrence of the paradoxical alpha effect.

Adult↗
PubMed1977

Ocular-motor function and information processing: implications for the reading process.

This paper discusses the dichotomy between continually moving eyes and the lack of blurred visual experience. A discontinuous model of visual perception is proposed, with the discontinuities being phase and temporally related to saccadic eye movements. It is further proposed that deviant duration and angular velocity characteristics of saccades in patients with hypertonic motor impairment relate to information processing defects. Stabilized retinal image procedures, which control for the effects of eye movements, significantly increase the ability of these patients actively to recall information presented for periods of less than three sec. A model of the reading process is presented based on these findings that addresses itself to the specific components of an interactions between eye movement, information transmission and information processing.

Alpha Rhythm↗
PubMed1976

Assessment of visual field impairment by objective technique.

An objective psychophysical technique for investigating visual fields by averaged scalp potentials evoked by pattern gratings of alternating contrast and by sinusoidally modulated flicerking light is applied to a child with a right homonomous hemianopsia. This technique illustrates a value, in obtaining clinical data on visual fields in situations were subjective perimetry is difficult to administer or where conservating diagnostic methods do not yield evidence of pathology.

Child↗
PubMed1975

Characteristics of saccadic eye movements in attentionally handicapped patients.

Some characteristics of saccadic eye movements were investigated electro-oculographically in hemiplegic attentionally handicapped patients and normal subjects under stationary and moving target situations. The velocity of saccadic eye movements was greater and the duration shorter in hemiplegic than in normal subjects. Greater variability of angular velocity and amplitude functions, and of duration and amplitude functions was found among hemiplegic subjects than among normal. The results were explained, in part, by possible differences in the strength of extra-ocular muscle contraction, variables associated with inhibitory control and learning variables.

Adolescent↗