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Biomedical subjects

H E Ross

Publications and source records attributed to H E Ross.

At least 55 records · Page 3Linked to original sources
PubMed1983

Optic-flow and cognitive factors in time-to-collision estimates.

Time-to-collision (Tc) estimates were obtained from twenty-four subjects who viewed film clips for varying lengths of time. The film clips showed the view from a moving car travelling towards a stationary target car, but ended 100 m before reaching the target. Viewing time varied from 2 to 6 s, approach velocity from 40 to 100 km h-1, and Tc from 3.6 to 9.0s. It was hypothesised that, if time were needed to calculate Tc, the accuracy of Tc estimates would increase with viewing time up to some maximum. However, the results showed no effect of viewing time, and this was taken to indicate that estimates were based upon information directly available from the changing optic array at the eye of the observer. A significant velocity effect was found, accuracy increasing with velocity. Since velocity was inversely correlated with Tc, this probably implies that accuracy decreases with increasing Tc. Sex differences were found, with males giving higher and more accurate estimates than females. The relevance of these findings to the nature of Tc information is discussed.

Adolescent↗
PubMed1981

Wundt's views on sensations of innervation: a reevaluation.

It is sometimes stated that Wundt believed in the primacy of 'sensations of innervation' in the control of eye and limb position, to the exclusion of afferent feedback. Wundt's own statements on the subject are traced through the six editions of the Grundzüge: he believed that sensations of innervation were a contributory factor along with peripheral feedback; but in the fourth edition he dropped the term and subsumed them under 'central sensations of senses', because increased neurophysiological knowledge made a literal interpretation of the original term impossible. In the fifth edition he developed a more precise model of central processes, described as 'sensory costimulation', and an additional idea of 'reproduced' or conditioned sensations. He mentions clinical evidence on the perception of eye and limb position of weight by paralysed and other subjects. This evidence is discussed in relation to modern theories. It is concluded that Wundt's later theories have some similarities with modern "hybrid' theories of efference-contingent afference.

Afferent Pathways↗
PubMed1980

Distortion and adaptation in underwater sound localization.

Sounds should be localized at more medial positions under water than in air, because the values of the interaural temporal and intensity differences are reduced in water. Thirteen blindfolded divers were required to move a pointer towards the apparent location of a sound source under water, and they showed significant errors towards the median plane. In a second experiment, five divers were tested in air before and after underwater training at swimming towards a sound source. The search patterns of these divers showed systematic errors towards the median plane. A comparison of the first and second air tests showed some evidence of an aftereffect away from the median plane, discounting the most lateral angles (80 degrees left and right) where little effect would be expected. It is concluded that both a distortion of localization and some adaptation to the distortion occur under water.

Auditory Perception↗
PubMed1979

Genetic and environmental factors in orientation anisotropy: a field study in the British Isles.

Visual acuity for the detection of gratings at four orientations was measured for groups of ten boys and ten girls aged five to seven years, from the following four populations: Scots in Glasgow, Pakistanis in Glasgow, Gaels in Stornoway (Outer Hebrides) and East Anglians in Littleport (Cambridgeshire fenlands). The Glaswegians, both Scottish and Pakistani, showed the normal pattern of anisotropy, with poorest acuity for oblique orientations; the East Anglians showed no significant anisotropy; while the Gaels were unusual in showing poorest horizontal acuity. A group of fourteen Pakistani children in Stornoway differed slightly from a matched group of Gaels. The group differences bore little relation to the visual environments, and were probably due to genetic or cultural factors. The relatively poor horizontal acuity of the Gaels was not correlated with astigmatism. Sex differences were also found, with the boys showing higher mean acuity and a higher ratio between vertical and oblique acuity.

Child↗
PubMed1978

Social functioning and self-care in hospitalized psychogeriatric patients.

Evaluations of social disability have been found useful in determining factors of diagnostic, therapeutic and prognostic significance in the management of psychogeriatric patients. A random sample of 100 psychogeriatric patients aged 65 or over admitted to three Toronto hospitals were studied prospectively. Standardized clinical and social interview schedules were used to assess patients' mental state, self-care capacity, social isolation, burden on the family and household contribution before admission. These assessments were carried out to determine their significance with respect to diagnosis and outcome. Self-care capacity, as measured by the Activities of Daily Living Performance Test or by informant report, was related to diagnosis and outcome measures in this sample. Social isolation was significantly correlated with length of hospital stay. Burden on the family was not found to be significantly associated with diagnosis or outcome although there was a tendency for patients with organic disorders to present more difficulties for their families. The severe burden imposed on relatives suggests the need for utilization of community social and medical services to provide relief for families of psychogeriatric patients. The implications for management are considered in the light of the above findings.

Activities of Daily Living↗
PubMed1977

Psychogeriatric hospital admissions from the community and institutions.

In a sample of 100 psychogeriatric admissions to three Toronto hospitals, the elderly in other institutions, including old age and nursing homes, and those living alone in the community were over-represented. Patients who had lived with relatives, on the other hand, were found to be at low risk for psychogeriatric hospitalization. These three groups of patients were compared using information obtained from psychiatric and social interviews with patients and informants, usually close relatives. Identification of specific needs for the various groups and the implication of these differences for the improvement of psychogeriatric care and prevention of unnecessary hospitalization are discussed. Institutional residents suffered more major physical illness, were less able to maintain functional independence, were referred more often for harmful behavior, were more socially isolated, and had a poorer outcome than community patients. Patients living along lacked familial support, but were not otherwise more socially isolated that those living with relatives, and showed no other deficits. The subjective and objective burdens on the patients' families before admission were considerable. The results are consistent with previous literature on the elderly.

Activities of Daily Living↗
PubMed1977

Social disability in chronic psychiatric patients.

The authors measured the social functioning of 147 chronic psychiatric patients using a rating scale originally devised for use with the mentally retarded, the Adaptive Behavior Scale (ABS). They found that social deficits were more widespread and generally more severe among chronic psychiatric patients than among institutionalized mentally subjects. Chronic undifferentiated schizophrenic patients showed the most comprehensive deterioration; other groups, such as neurotic patients, women, and the elderly, had more limited impairments. The authors suggest that the ABS can be useful in establishing the limits of social functioning of chronic psychiatric patients.

Adult↗
PubMed1976

Did Ptolemy understand the moon illusion?

Ptolemy is often wrongly credited with an explanation of the moon illusion based on the size-distance invariance principle. This paper elucidates the two Ptolemaic accounts: one in the Almagest, based on atmospheric refraction, and the other in the Optics, based on the difficulty of looking upwards. It is the latter passage which has been thought to refer to size-distance invariance, but it is more probable that it refers to the idea that the visual rays are diminished by the force of gravity (i.e. that the retinal image is reduced in size). Alhazen was probably the first author to explain the illusion by the size-distance invariance principle, and Roger Bacon the first to explain the enlarged apparent distance of the horizon by the presence of intervening objects. Della Porta was the first to credit Ptolemy with these explanations, and this mistake was repeated by many subsequent authors.

Astronomy↗
PubMed1976

The direction of apparent movement during transient pressure vertigo.

Pressure vertigo or alternobaric vertigo is the type of vertigo normally associated with relative overpressure in the middle ear. As with other types of vertigo, it should occur only if there is unequal stimulation of the left and right vestibular systems: there should be a lawful relation between the orientation of the head, the side of the overpressured ear, and the direction of apparent movement. Few published accounts give information on all these aspects. This paper reports some old and new cases which suggests that, when the head is upright during the ascent, overpressure in the right ear causes apparent bodily and visual movement to the right (clockwise), while overpressure in the left ear has the opposite effect. Horizontal orientation of the head probably reduces the vertigo. There are no detailed and unequivocal reports of pressure vertigo during descent, or with the head inverted. Some reports exist of tumbling sensations and of tilting of the visual scene, but the exact circumstances are unclear.

Diving↗