Spared unconscious influences of spatial memory in diencephalic amnesia

Abstract

Spatial memory is crucial to our daily lives and in part strongly depends on automatic, implicit memory processes. This study investigates the neurocognitive basis of conscious and unconscious influences of object-location memory in amnesic patients with Korsakoff's syndrome (N = 23) and healthy controls (N = 18) using a process-dissociation procedure in a computerized spatial memory task. As expected, the patients performed substantially worse on the conscious memory measures but showed even slightly stronger effects of unconscious influences than the controls. Moreover, a delayed test administered after 1 week revealed a strong decline in conscious influences in the patients, while unconscious influences were not affected. The presented results suggest that conscious and unconscious influences of spatial memory can be clearly dissociated in Korsakoff's syndrome.

Fig. 1

Schematic overview of the rooms task (actual picture size approx. 20 × 25 cm) during the learning and the test phase. In the Include trials (a) of the test participants had to relocate the objects to the positions they had occupied previously while in the Exclude trials (b), they needed to allocate the object to a different location (choice of three). In case the original location could not be remembered, in both conditions participants had to place the object in the first location that came to mind. Objects that had not been shown during the learning phase were introduced to determine chance performance (c)

Fig. 2

Estimates of conscious (a) and unconscious (b) memory influences for the Korsakoff amnesia patients and the controls in the immediate recall and the delayed recall conditions