QOL-06. What impact does a posterior fossa tumor in childhood have on motor procedural learning? Group performance depending on radiotherapy status and individual differences on a perceptivo-motor sequence learning task and a motor adaptative task (IMPALA prospective study)

INTRODUCTION: Procedural memory (PM) is a skill learning system that allows, through training, the automatization of procedures and progressive improvement of performances. The aim of this work was to explore the impact of a posterior fossa tumor (PFT) on PM. We hypothesized that motor adaptation, depending on cortico-cerebellar system, was impaired in PFT survivors treated with and without radiotherapy, and motor sequence learning, depending on cortico-striatal system, was only impaired in PFT treated with radiotherapy. METHODS: We investigated PM in 60 participants from the IMPALA study (NCT04324450) divided into three groups: 39 cured from a PFT in childhood (22 irradiated (PFT+RT group) and 17 non-irradiated (PFT group)) and 21 healthy volunteers (Control group) matched on age, sex and handedness with the PFT+RT group. We used a visuo-motor learning test, the Serial Reaction Time task (SRTT) and a motor adaptation task (MAT) of backwards handwriting. ANOVA and mixed models were used for statistical analysis. RESULTS: SRTT performance analysis showed an effect of Block in specific sequence learning (F(1)48.70,p<0.001) with a preserved specific learning in the three groups. However individual differences were observed with 7/22 patients in PFT+RT group and 4/17 in PFT group who did not have specific learning. MAT performance analysis showed an effect of interaction between Orientation (forward or backward) and Group for speed (F(2)15.58,p<0.001), linearity (F(2)8.39,p<0.001) and amplitude standard deviation (F(2)15.70,p<0.001) traducing an impairment both in PFT+RT and PFT groups, more marked in the PFT+RT group. CONCLUSION: We showed impairment, predominantly on motor adaptation but also, at individual level, in motor sequence learning whose origin requires additional work. This study brings new insights on the long-term impact of a PFT in childhood on a rarely investigated part of memory that is PM.