Agnosia (including Prosopagnosia and Anosognosia)

The neuropsychological disorder known as agnosia refers to the impairment of stimulus recognition in one modality in the absence of perceptual deficits, memory problems, and general intellectual impairment. This disorder is intriguing, both scientifically and clinically, and its study has contributed to shed light on how the normal visual system functions. Here, we focus specifically on the neuropsychological studies of agnosia and provide a broad overview of the wide range of impairments characterized by lack of knowledge, including visual agnosia, prosopagnosia, agnosia for words, tactile agnosia and color agnosia. A separate section is devoted to anosognosia, which is the denial of illness or of the symptoms of a particular disease usually associated with a specific brain damage.