Although these findings highlight the complexity of gene expression and exon usage in the human brain, there are several potential limitations in our data that warrant discussion. Foremost, we used stringent criteria in order to faithfully characterize general transcriptional patterns and minimize false positives, rather than to capture all the changes that may occur. Also, we analyzed dissected tissue samples that contain multiple cell types, thus diluting the genetic contribution and dynamic range of genes expressed in a more cell type specific manner. Current limitations prevent us from using cell type specific approaches in systematically analyzing the spatiotemporal transcriptome. Furthermore, the number of brains and regions analyzed so far is not sufficient to fully investigate the whole magnitude of transcriptional changes or the full range of eQTLs. Application of sequencing technology will allow even more in-depth analysis of the transcriptome and discovery of novel and low-expressing transcripts and their associated spatiotemporal patterns. Finally, while specific patterns of expression are often linked to equally specialized biological processes, it is important to keep in mind that the relationship between mRNA and protein
