Specific methodological details are available on the “Documentation” tab at http://aging.brain-map.org/.  In short, collection of tissue samples from temporal and parietal neocortex, parietal white matter, and hippocampus was done by manual macrodissection.  Tissue was immediately transferred to prepared tubes where RNA was isolated using the RNeasy Lipid Tissue Mini Kit (Qiagen #78404) as per manufacturer’s instructions.  RNA was then quantified on a Nanodrop 8000 spectrophotometer (Thermo Scientific, Wilmington, DE) and normalized to 5ng/μl before RNA QC was performed using a Bioanalyzer (Agilent Technologies) and RNA Integrity Number (RIN) was recorded. Total RNA (250ng) was used as input into the Illumina TruSeq Stranded Total RNA Sample Prep Kit (RS-122-2203), which uses random hexamer first strand cDNA synthesis and includes rRNA depletion (Ribo-Zero Gold rRNA depletion kit) and fragmentation. At the time of project inception, this sequencing strategy provided the most reliable option for quantification of transcriptomic reads from tissue of widely varying quality, allowing the broadest inclusion of donors from the ACT cohort.  External RNA Controls Consortium (ERCCs) at a 1:10,000 dilution were spiked into each sample.  RNA sequencing was done on Illumina HighSeq 2500 using v4 chemistry, producing a minimum of 30 million 50bp paired-end clusters per sample. Expression Analysis, Inc. (Morrisville, NC) performed both the TruSeq Stranded Sample Prep as well as the Illumina sequencing.