Communication by speech is a strictly human characteristic. Evolution of language was dependent on the development of underlying psychological functions. For language to emerge from the signal and sound systems common to many species, the human brain had to evolve to a point whereby it could integrate the vocalisations of the speech organs and also decipher and store linguistic data. Language is viewed, therefore, as one of the highest and most complex of cerebral functions, and subsequently language breakdown or dysfunction as one of the most sensitive indicators of brain damage or change. The diversity of clinical presentation from patients presenting with similar trauma, support such non-predictability of effect, when structure/function links are made purely on the basis of cortical damage. Wernicke's area, within the posterior language zone, appears to be of central importance in the comprehension and production of language through both speech and writing.