12Head motion during MRI scanning influence estimates of cortical morphology. 13 Previous studies have found that older adults demonstrate greater head motion than 14 younger adults, while other studies have found task-related differences in head motion.
15Cortical morphology also differ with age, as measured by cortical thickness, fractal 16 dimensionality, and gyrification. Here I replicated all three of these prior findings 17 within a larger dataset than these results have been demonstrated previously, with a 18 sample size of more than 600 adults across the adult lifespan (Centre for Ageing and 19 Neuroscience, CamCAN). Furthermore, I additionally test for the influence of head 20 motion on cortical fractal dimensionality and gyrification; effects were statistically 21 significant in some cases, but small in magnitude.
22HEAD MOTION, AGING, AND BRAIN MORPHOLOGY 3 Age differences in head motion and estimates of cortical morphology 23 131Of particular interest, I also examined the influence of head motion on the cortical 132 morphology estimates. For all three measures, head motion explained only a small 133 amount of additional variance beyond age, as shown in Table 1. Nonetheless, head 134 motion from the movie scan did explain significant additional variance, as measured 135 by ∆BIC, however, this only accounted for an additional 1% variance. In the model of 136 cortical thickness including head motion from the movie scan (but not the interaction), 137 age related changes corresponded to −0.0398 mm/decade, while head motion 138 contributed −0.0135 mm/(mm/min).