SULCAL VARIABILITY IN THE ALZHEIMERS BRAIN - CORRELATIONS WITH COGNITION

We mapped the three dimensional (3D) extents and variability of select ed sulci in the Alzheimer's brain and explored the relationship betwee n sulcal pattern and patient's cognitive performance. High-resolution MRIs of 10 patients with probable Alzheimer's disease (AD) were Linear ly transformed into a standard ''normalized'' 3D atlas (known as the T alairach coordinate system) and, on each relevant slice, contours of t he left and right Sylvian fissure, anterior and posterior calcarine, c allosal, parietooccipital, and cingulate sulci and the floor of the te mporal horn of the lateral ventricle were traced. These landmarks were chosen because of their relative invariant location across individual s and because they demarcate functional boundaries relevant in AD. The sulcal contours were resolved into two-dimensional surfaces that cut through a brain volume. All 10 patients' sulcal surfaces were averaged to determine their mean spatial locations in the Talairach coordinate system. The 3D spatial extents of each patient's sulci were compared with their disease severity based on neuropsychological performance. T he 3D sulcal variability, within the ''normalized'' atlas space, range d from 4.0 mm for the left callosal sulcus to 9.1 mm for the left Sylv ian fissure. Significant correlations were found among the spatial ext ents for the posterior floor of the right temporal horn of the lateral ventricle (r = -0.89, p < 0.001 for vertical extent) and right anteri or calcarine sulcus (r = -0.75, p < 0.01 for anterior-posterior extent ) with copying ability of the Rey-Osterrieth Complex Figure; the right anterior calcarine also had a significant relationship (r = -0.72, p = 0.02 for anterior-posterior extent) with performance on the Block De sign subtest from the Wechsler Adult Intelligence Scale-Revised. Verba l fluency performance measured by the Controlled Oral Word Association Test was significantly related to the left cingulate (r = 0.91, p < 0 .001 for anterior-posterior extent, and r = -0.82, p < 0.01 for vertic al extent) and right cingulate (r = -0.72, p less than or equal to 0.0 2 for vertical extent) sulci. This exploratory study is the first to e valuate the relationship between 3D sulcal variability and cognition; our preliminary findings suggest that the 3D pattern of sulci in the A D brain is related to the severity of the disease as reflected by cogn itive performance. In the Talairach brain atlas, sulcal variability, w ithin an AD population, approaches 1 cm. This large variability requir es correction when functional imaging data are transformed into the Ta lairach atlas space to ''normalize'' individual morphologic difference s.