Due to all these complexities and to concerns regarding the reliability and concordance of microarray data, especially when samples with only subtle differences in gene expression are analyzed, it has been recommended (Pedotti, et al., 2008) that two different platforms be used simultaneously. Also, international consortia and technical groups have been formed to standardize microarray technology, specifically those related to data validation and presentation (Kawasaki, 2006). Yet, despite all of its disadvantages, microarray analysis has enabled the measurement of thousands of genes in a single RNA sample simultaneously, and this has made the technology especially valuable for studies of global patterns of gene expression. Correspondingly, since 1995, there has been an exponential increase of the number of gene expression studies using microarrays. As a result of this interest, our current knowledge of transcriptomes in the human brain is based on reports of studies that used microarray techniques for transcriptome profiling.
