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At least 73 records · Page 4Linked to original sources
PubMed1977

The development in very young children of tacit knowledge concerning visual perception.

The purpose of this study of early social-cognitive development was to assess the very young child's behaviorally expressed knowledge of people's visual-attentional acts and abilities. Boys and girls (N = 60) 1, 1 1/2, 2, 2 1/2, and 3 years of age were tested in their homes with their mother's help. Three sorts of tasks were used: 1. Percept production. The child's task was to produce a visual percept in the other. Examples include pointing to objects ("productive pointing") and a wide variety of object-showing problems. 2. Percept deprivation. The opposite, exemplified by a variety of object-hiding problems. 3. Percept diagnosis. The child's task was to determine what the other was already visually attending to, either by looking where his or her finger was pointed ("receptive pointing") or where his eyes were directed. It was found that the majority of 1-year-olds produced and comprehended pointing, and would sometimes hold out a toy to show it, but did little else. The 3-year-olds were at ceiling on virtually all tasks. At 1 1/2 years, children usually showed a picture by holding it flat so that both they and the other could see it. Jrom 2 on, they usually turned it toward the other in the adult fashion. Very few children of any age showed egocentrically--i.e., orienting the picture so only they could see it. By age 2, the children solved what were presumably novel showing problems for them: e.g., successfully showing to another a picture pasted on the inside bottom of a hollow cube. Hiding ability emerged later than showing ability but seemed well established by age 3. The role of the other's eyes in seeing appeared to be quite well understood at least by age 2-2 1/2. As examples, children of this age took the other's hands away from her or his eyes before trying to show her something, and could usually tell where she was looking from her eye orientation alone. These age trends presumably reflect important developments in the area of social interaction and communication, as well as with respect to cognition about percepts.

Age Factors↗
PubMed1991

Cortical blindness and residual vision: is the "second" visual system in humans capable of more than rudimentary visual perception?

We studied 12 patients with static cortical blindness to evaluate residual vision after destruction of area 17 and to assess the visual capacity of the subcortical "second" visual system in humans. In each case, the cause was bilateral infarction of the occipital lobes. Five patients had total blindness, and four had residual rudimentary vision (RRV), characterized by homonymous areas of light perception in the peripheral field and ability to detect moving objects. Only three patients had the ability to read; two of these had spared macular vision, and the other had spared left homonymous hemimaculae and spared temporal crescent. Neuroimaging and visual evoked potentials (VEPs) correlated with the extent of the visual dysfunction. Total destruction of area 17 bilaterally was associated with total permanent visual loss. The larger the amount of spared visual cortex, the better the vision. Positron emission tomography (PET) or single photon emission computed tomography (SPECT) demonstrated retained metabolic activity in islands of preserved area 17 in patients with some residual vision. VEPs were present in totally blind individuals. We conclude that, in humans, useful visual function is preserved only when a critical amount of area 17 is spared. The subcortical second system may participate in the generation of VEPs, but is incapable of conscious visual perception.

Aged↗
PubMed1991

[Prosopagnosia. A rare disorder of visual perception].

Prosopagnosia is a rare neurological sign, characterized by disturbance of recognition of faces. It is important to remember that prosopagnosia can appear as a result of a brain injury, and as such may be a major disability to the patient. We report a case of a nine year old boy with prosopagnosia due to brain injury at the age of 18 months. The main injury was localized to the boy's left hemisphere, but his right hemisphere was probably also affected. Most post mortem examinations of patients suffering from prosopagnosia show bilateral or right-sided parietal, temporal and occipetal pathological changes.

Agnosia↗
PubMed1992

Optical imaging of architecture and function in the living brain sheds new light on cortical mechanisms underlying visual perception.

Long standing questions related to brain mechanisms underlying perception can finally be resolved by direct visualization of the architecture and function of mammalian cortex. This advance has been accomplished with the aid of two optical imaging techniques with which one can literally see how the brain functions. The upbringing of this technology required a multi-disciplinary approach integrating brain research with organic chemistry, spectroscopy, biophysics, computer sciences, optics and image processing. Beyond the technological ramifications, recent research shed new light on cortical mechanisms underlying sensory perception. Clinical applications of this technology for precise mapping of the cortical surface of patients during neurosurgery have begun. Below is a brief summary of our own research and a description of the technical specifications of the two optical imaging techniques. Like every technique, optical imaging also suffers from severe limitations. Here we mostly emphasize some of its advantages relative to all alternative imaging techniques currently in use. The limitations are critically discussed in our recent reviews. For a series of other reviews, see Cohen (1989).

Brain↗