IMPAIRED ASSOCIATIVE LEARNING IN CHRONIC-FATIGUE-SYNDROME

PATIENTS with chronic fatigue syndrome (CFS) report cognitive difficul ties (impaired attention, memory and reasoning). Neuropsychological te sts have failed to consistently find cognitive impairments to the degr ee reported by CFS patients. We tested patients with CFS and sedentary controls in protocols designed to measure sensory reactivity and acqu isition of the classically conditioned eyeblink response. Patients wit h CFS exhibited normal sensitivity and responsivity to acoustic stimul i. However, CFS patients displayed impaired acquisition of the eyeblin k response using a delayed-type conditioning paradigm. Sensitivity and responsivity to the airpuff stimulus were normal. In the absence of s ensory/motor abnormalities, impaired acquisition of the classically co nditioned eyeblink response indicates an associative deficit. These da ta suggest organic brain dysfunction within a defined neural substrate in CFS patients. (C) 1998 Rapid Science Ltd.