Supplementary Material

CSF Analysis

CSF levels of T-tau and P-tau were analyzed using INNOTEST enzyme-linked immunosorbent assays (ELISAs) (Fujirebio Europe N.V., Gent, Belgium). Neurofilament light chain (NFL) concentrations were determined using the NF-light method (UmanDiagnostics, Umeå, Sweden) and YKL-40 (also known as chitinase-3-like protein 1, CHI3L1) was measured using the Human Chitinase 3-like 1 Quantikine ELISA Kit (R&D systems, Minneapolis, MN). The soluble APP isoforms α and β (sAPPα, sAPPβ) were measured using the MSD sAPPα/sAPPβ Multiplex Assay (Meso Scale Discovery, Rockville, MD).

Neuropsychological Assessment

Research neuropsychological assessment included Recognition Memory Tests (RMT)[1,2], and tests of posterior cortical functions including the VOSP Object Decision [3] or space perception (VOSP Number Location test) tests, the Graded Difficulty Arithmetic test[4], and Graded Difficulty Spelling test[5]. Those individuals fulfilling clinical criteria for PCA [6] who also performed above the 5th percentile on a memory test and below the 5th percentile on at least two of the four tests of posterior functions were additionally defined as fulfilling neuropsychology criteria for PCA (n-PCA)[7]. Those with impairment on both memory tests were defined as fulfilling research neuropsychology criteria for typical AD (n-tAD).

1. Warrington E (1984) Recognition Memory Test. NFER-Nelson, Windsor, UK

2. Warrington EK (1996 ) The Camden Memory Tests. Psychology Press

3. Warrington EK, James M (1991) A new test of object decision: 2D silhouettes featuring a minimal view. Cortex; a journal devoted to the study of the nervous system and behavior 27 (3):370-383

4. Jackson M, Warrington EK (1986) Arithmetic skills in patients with unilateral cerebral lesions. Cortex; a journal devoted to the study of the nervous system and behavior 22 (4):611-620

5. Baxter DM, Warrington EK (1994) Measuring dysgraphia: a graded-difficulty spelling test. Behavioural neurology 7 (3):107-116. doi:10.3233/BEN-1994-73-401

6. Tang-Wai DF, Graff-Radford NR, Boeve BF, Dickson DW, Parisi JE, Crook R, Caselli RJ, Knopman DS, Petersen RC (2004) Clinical, genetic, and neuropathologic characteristics of posterior cortical atrophy. Neurology 63 (7):1168-1174

7. Lehmann M, Crutch SJ, Ridgway GR, Ridha BH, Barnes J, Warrington EK, Rossor MN, Fox NC (2011) Cortical thickness and voxel-based morphometry in posterior cortical atrophy and typical Alzheimer's disease. Neurobiology of aging 32 (8):1466-1476. doi:10.1016/j.neurobiolaging.2009.08.017