Memory dissociation and metamemory in multiple sclerosis

A previous study by Scarrabelotti and Carroll [60] was the first to use Jacoby's process dissociation procedure [31] with an MS group to investigate memory function, and the first to obtain metamemory judgments about recall under inclusion and exclusion instructions. Twelve months later using different words, 49 MS and 39 matched controls were readministered a word stem completion task, and made metamemory judgments about their performance. The California Verbal Learning Test (CVLT) [18], Stroop [64], and Reitan's Word Finding Test (WFT) [57], tests considered to particularly rely on conscious processing, were also readministered. At year one testing no group differences were identified in word stem completion under indirect, inclusion, or exclusion instructions, nor in conscious and automatic estimates. By contrast in year two, MS subjects remembered significantly fewer words under inclusion, and employed significantly less conscious processing than the control group to achieve remembering. However, estimates of automatic memory processing were the same for both groups. MS subjects equalled controls in the prospective and retrospective monitoring of words they consciously recalled under inclusion instructions, in both years. By contrast, each group was poor at monitoring words completed automatically under exclusion instructions; and by year two, MS subjects were even less able to monitor such material than controls. Finally by the second year, reduced conscious processing was also related to reduced performance on the Stroop, WFT, and CVLT recall and use of semantic clustering. Taken together, these findings indicate that automatic memory processing is intact in MS, but impairment in memory, metamemory, and other cognitive tasks becomes evident over time when they rely on conscious processes.