Motion‐defined letter detection and recognition in patients with multiple sclerosis

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Abstract
Two important distinctions in visual perception are (1) between the detection and recognition of shapes (e.g., letters), and (2) between the recognition of shapes defined by a difference in brightness and the recognition of shapes defined by a difference in motion. We report that 6 of 10 patients with multiple sclerosis showed impaired recognition for motion‐defined (Md) letters, although the detection of Md letters was normal as were both detection and recognition of luminance‐defined letters. We have shown that this was not a function of acuity loss or the loss of ability to detect motion or a general failure of recognition per se, but was confined to a loss of ability to recognize Md letters. The neurological implications of these findings are discussed, and it is suggested that the Md letter test be used by others interested in the central pathology of visual disorders.