title: The precision of anatomical normalization in the medial temporal lobe using spatial basis functions.
abstract: We investigated the accuracy of spatial basis function normalization using anatomical landmarks to determine how precisely homologous regions are colocalized. We examined precision in terms of: (1) the number of nonlinear basis functions used by the normalization procedure; (2) the degree of (Bayesian) regularization; and (3) the effect of substituting different templates and how this interacted with the number of basis functions. The face validity of spatial normalization was assessed as a function of these parameters, using the colocalization of homologous landmarks in a test sample of 20 normally developing children and 5 children with bilateral hippocampal pathology. Our results suggest that when optimal normalization parameters are used, anatomical landmarks in the medial temporal lobes are colocalized to within a standard deviation of about 1 mm. When suboptimal parameters are used this standard deviation can increase up to 3 mm. Interestingly the optimal parameters are those that provide a rather constrained normalization as opposed to those that optimize intensity matching at the expense of rendering the warps "unlikely." The implications of our results, for users of voxel-based morphometry, are discussed.
authors.affiliation: Developmental Cognitive Neuroscience Unit, Institute of Child Health, University College London, 30 Guilford Street, London WCIN 1EM, United Kingdom.
authors.forename: C H
authors.initials: CH
authors.lastname: Salmond
authors.forename: J
authors.initials: J
authors.lastname: Ashburner
authors.forename: F
authors.initials: F
authors.lastname: Vargha-Khadem
authors.forename: A
authors.initials: A
authors.lastname: Connelly
authors.forename: D G
authors.initials: DG
authors.lastname: Gadian
authors.forename: K J
authors.initials: KJ
authors.lastname: Friston
mesh_terms: D000293:Adolescent; D000647:Amnesia / Q000473:pathology; D002648:Child; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006624:Hippocampus / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D013702:Temporal Lobe / Q000033:anatomy & histology*