A study of gene expression in the living human brain.

A central goal of neuroscience is to advance knowledge of the molecular basis of human brain function. Most molecular studies of the human brain have been performed using tissue from postmortem brain donors rather than living people. The assumption underlying this practice - which had never been rigorously tested prior to this report - is that the postmortem human brain is an appropriate proxy for the living human brain at the molecular level. Here, this assumption is thoroughly challenged for the first time by comparing human prefrontal cortex gene expression between 275 living samples and 243 postmortem samples. Vast differences in gene expression were found between the living and postmortem human brain. Expression levels differed significantly for nearly 80% of genes, and this finding was not a consequence of any potential technical or biological confounders of the gene expression data. Postmortem brain gene expression signatures of Alzheimer's disease, schizophrenia, Parkinson's disease, bipolar disorder, and autism spectrum disorder were shown to be inaccurate representations of disease processes occurring in the living brain. In light of these findings, the use of postmortem tissue as a proxy for living tissue in human brain research should be reconsidered. To advance knowledge of the molecular basis of human brain function, the study of tissue from living people should be prioritized.