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PubMed2005

[The relationship between visual perception and postural control in falls of the elderly living in local communities].

We have examined the relationship between visual sense information, such as perception data and postural control, and falls among elderly people aged 65 years or over living in Nishibiwajima-cho, Aichi Prefecture. Of 286 participants, 204 were enrolled and analyzed, after excluding those with a visual acuity of less than 0.3, or the activities of daily living (ADL) index of less than 11. In the analysis group, 52 people (25.2%) had already had experience of falls. Two-way analysis of variance showed that intensity of dynamic visual stimulation and the presence or absence of falls had a significant effect on body sway, although no interaction was observed. These results indicate that body sway is increased in those who have experience of falls, and that strong visual stimulation is associated with body sway. This suggests that greater dynamic visual stimulation is likely to increase the risk of falls.

Accidental Falls↗
PubMed1989

The development of separability in visual perception.

Under conditions that do not allow focused attention, reports of illusory conjunctions (i.e. errors that wrongly recombine the features of different objects) constitute evidence of the separate registering of features at an early processing level. The occurrence of illusory conjunctions was used to determine whether there is preattentive analysis of component dimensions (colour and form) and of parts of shapes (triangles and arrows) in young children aged 5 to 8 years. Evidence of preattentive analysis was found, even for the youngest children, for colour and form but not for parts of shapes. Although developmental effects hardly reached significance, inspection of abilities assumed to affect the illusory conjunctions phenomenon suggests that at the preattentive stage children can integrate spatially separate segments but lack the capacity to fully analyse connected segments.

Adult↗
PubMed2005

Creating a meaningful visual perception in blind volunteers by optic nerve stimulation.

A blind volunteer, suffering from retinitis pigmentosa, has been chronically implanted with an optic nerve visual prosthesis. Vision rehabilitation with this volunteer has concentrated on the development of a stimulation strategy according to which video camera images are converted into stimulation pulses. The aim is to convey as much information as possible about the visual scene within the limits of the device's capabilities. Pattern recognition tasks were used to assess the effectiveness of the stimulation strategy. The results demonstrate how even a relatively basic algorithm can efficiently convey useful information regarding the visual scene. By increasing the number of phosphenes used in the algorithm, better performance is observed but a longer training period is required. After a learning period, the volunteer achieved a pattern recognition score of 85% at 54 s on average per pattern. After nine evaluation sessions, when using a stimulation strategy exploiting all available phosphenes, no saturation effect has yet been observed.

Artificial Intelligence↗
PubMed1990

The Charles Bonnet syndrome. Visual perceptive dysfunction in sensory deprivation.

We present a series of four patients with the Charles Bonnet syndrome, which is characterized by recurrent vivid visual hallucinations in the presence of normal cognition and insight. It usually occurs in elderly people with ophthalmic pathology causing severe visual sensory deprivation. Our experience suggests that this syndrome is frequently overlooked or misdiagnosed by both ophthalmologists and psychiatrists. To our knowledge this is only the second series of cases of the syndrome in the American literature.

Adult↗
PubMed2005

Flexibility of spatial averaging in visual perception.

The classical receptive field (RF) concept-the idea that a visual neuron responds to fixed parts and properties of a stimulus-has been challenged by a series of recent physiological results. Here, we extend these findings to human vision, demonstrating that the extent of spatial averaging in contrast perception is also flexible, depending strongly on stimulus contrast and uniformity. At low contrast, spatial averaging is greatest (about 11 min of arc) within uniform regions such as edges, as expected if the relevant neurons have orientation-selective RFs. At high contrast, spatial averaging is minimal. These results can be understood if the visual system is balancing a trade-off between noise reduction, which favours large areas of averaging, and detail preservation, which favours minimal averaging. Two distinct populations of neurons with hard-wired RFs could account for our results, as could the more intriguing possibility of dynamic, contrast-dependent RFs.

Contrast Sensitivity↗