Agnosia

Agnosia is a disorder in which basic sensory functions (vision, hearing, touch) are intact but the brain cannot process and interpret this sensory information meaningfully. The patient sees the object but cannot recognize what it is.

The most common types are visual agnosia, auditory agnosia, tactile agnosia, and prosopagnosia (inability to recognize faces). These disorders arise from damage to the relevant association cortices of the brain.

Underlying causes include stroke, head trauma, brain tumors, encephalitis, and degenerative diseases such as Alzheimer's. Diagnosis is made through detailed neuropsychological evaluation and brain imaging.