An event-related brain potential study of encoding and retrieval during spatial working memory in systemic lupus erythematosus
Objective: Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease that can affect almost any organ of the body, including the brain. One of the most common cognitive deficits in SLE patients is in working memory (WM), which involves short-term storage and manipulation of information. This study compared SLE patients and controls on behavioral and electrophysiological measures in order to determine if there was a disturbance in WM in SLE and specifically, if the deficit was detectible during Encoding (En) or Retrieval/Response Selection Stages of WM. Method: The present proposal examined differences in WM between 34 SLE patients and 32 healthy controls using event-related brain potentials (ERPs) that were obtained during a visual-spatial WM task that assessed En and Retrieval stages of WM. Seventeen patients with diffuse neuropsychiatric syndromes (dNPSLE) were also compared with healthy controls in subsequence analyses. ERPs were derived from the ongoing electroencephalographic (EEG) data obtained during the WM task. Amplitude and latency for the P3 ERP component were obtained for both En and Response Selection. Results: SLE patients had significantly longer reaction times (RT) than controls, but did not differ from controls for retrieval accuracy. Further, SLE patients (particularly for dNPSLE) had generally lower P3 amplitude than controls and this difference was most profound during the Retrieval Stage of WM. The SLE group had longer latency than controls during match trails of the Retrieval Stage, but not during En or non-match trails. Conclusion: Prolonged P3 latency (reflecting slowed central processing speed) and reduced P3 amplitude (reflecting increased task difficulty) supports the notion that deficits in visual-spatial WM are present in SLE, particularly during the Retrieval/Response Selection Stage.