Considering sulcal width rather than cortical thickness to assess brain atrophy in ageing: a large multi-sample study

International audienceRecent developments in neuroimaging have popularized the use of cortical thickness as a morphological biomarker to assess local cerebral atrophy. Based on several considerations, it is suggested that exploring another fold-related atrophy feature such as sulcal opening could provide novel insights in assessing changes in the aging brain. In this study, two large cohorts are employed to compare the performances of cortical thickness and sulcal span in relation to cognition and the evaluation of localized atrophy. Using the first cohort, which comprises individuals from the general population (n1=20,541), age trajectories were delineated cross-sectionally and fitted on piecewise linear models to define critical ages at acceleration points. Upon examination of these critical ages, called tipping-point ages, it became evident that sulcal opening exhibited greater and earlier sensitivity to neurodegeneration compared to cortical thickness. An investigation into the relevance of the selected mathematical model is subsequently conducted, using the second cohort (n$_2$=2,323) of subjects with very mild to mild cognitive impairment or isolated subjective cognitive complaints while not demented. Effects of neuropsychological impairment on the trajectories were evaluated in a hypothesis-driven fashion by correlating local atrophy acceleration with diverse cognitive test scores. Taken together, our results show the potential of an understudied fold-based feature in investigating regional cerebral atrophy and offer new insights on physio-pathological processes during aging