Analysis of the studies of the perception of fragmented images: global description and perception using local features.

This report presents an analysis of studies of the visual perception of fragmented images. Two approaches to the description of brain functioning during the solution of this task are considered: studies of the perception of the statistical properties of global whole images and studies of the perception of images in terms of local higher-order informative features. These approaches describe two different mechanisms which the human brain may use for recognizing incomplete images. Studies performed using the Gollin test (measurement of recognition thresholds for fragmented outline images during gradual construction of the outline) are given most attention. In solving this task, the visual system extracts the statistical properties of the whole image. Local higher-order informative features are used by the brain as additional sources of information about the image. The role of this source increases on learning a given alphabet of stimuli. In accordance with a matched filtration model, the fragmented images used in the Gollin test are perceived as a whole structure, compared with a reference which is stored in memory and selected using the selective attention mechanism. At the primary filtration step and the matched filtration step, the recognition thresholds of images in the Gollin test reflect the processes of extracting the signal from noise. The Gollin test can be used as a differential tool for the diagnosis of different types of cognitive impairments.