P 9 Uncoupling memory interaction during off-line consolidation: an fMRI study

Abstract

Background This study focuses on the interaction of procedural and declarative memory contents and its effect on off-line consolidation over wakefulness on a neurophysiological level using fMRI. The finding that disconnecting declarative from implicit procedural motor contents allows off-line consolidation of motor performance over wakefulness but not over sleep ( Brown and Robertson, 2007 ) challenged the idea of separated memory systems ( Cohen and Squire, 1980 ) and lead to the assumption of an interaction during wakefulness but separation during sleep. Word-list learning for instance can uncouple declarative from procedural contents. We hypothesize, this results in diverging neuronal activity after off-line consolidation but no differences should occur, when keeping declarative and procedural aspects together. Methods Therefore, 65 healthy participants conducted a serial reaction time task (SRTT) as a procedural motor learning task in the morning immediately followed by one of four interference tasks or no further tasks (Rest) ( Fig. 1 ). The declarative verbal learning group (VL) learned a word-list consisting of 15 words, their control group (VLC) counted vowels in a nonsense letter string as a attention task based on verbal material. The declarative non-verbal learning group (NVL) played a kind of memory game with the appropriate control group counting squares in a cloud of triangles (NVLC). All participants repeated the SRTT ( Nissen and Bullemer, 1987 ) for a retest after 12 h investigating effects of memory systems” interaction. The SRTT has been conducted in a 3 T MRI scanner. Results In the verbal learning group the BOLD-Signal decreased from learning to testing in the ipsilateral cerebellum as well as in the supplementary motor area. In addition, we found an interaction between the verbal learning group and their appropriate control group and the rest group for BOLD-Signal within in these areas. No comparable effect was evident in the non-verbal groups. Discussion/conclusion Based on our results we ascribe a discharging effect on parts of the motor system to the uncoupling of declarative aspects from procedural learning by an interfering verbal learning task. This effect arose in the ipsilateral cerebellum as well as in the supplementary motor area.