A neurological disorder caused by a deficiency of vitamin B1 (thiamine). The principal symptoms are confusion, oculomotor abnormalities (gaze palsy and nystagmus), and ataxia. The disorder is most frequently associated with chronic alcoholism but is also found in cases of pernicious anemia, gastric cancer, and malnutrition. These symptoms are likely to resolve with thiamine treatment, although most individuals then develop severe retrograde and anterograde amnesia as well as impairment in other areas of cognitive functioning, including executive functions.