In the past few years, microarray technology has matured into a commonly used laboratory tool in biomedical research, including neuroscience. A variety of topics in neuroscience have now been investigated using microarray-based approaches. Although the initial microarray publications appeared in the early 1990s, the rst neuroscience microarray study dates to just 1999. To date, several deoxyribonucleic acid (DNA) array studies have been published with a constant and signi - cant increase throughout the years (Figure 18.1). Microarray-based studies in neuroscience encompass neurological, and psychiatric disorders, drug addiction (see later), memory and learning [1,2], and circadian rhythms [3,4]. Arrays have been used to address the topic of human brain evolution comparing the gene expression patterns of Homo sapiens, to those of the close relative Pan troglodytes and other primates (for a review see Ref. [5]).