Over the past 30 years, studies in the cognitive neuropsychology of acquired dysgraphia have led to develop articulated theories of the functional architecture of the cognitive processes involved in written and oral spelling. More recent analyses of the lesions observed in subjects with highly selective disorders of spelling are beginning to licence explicit hypotheses of the correlations between specific components of the spelling process and their neural substrate.
Current models of spelling assume a distinction between orthographic lexical knowledge (a long-term memory system that represents letter sequences corresponding to familiar words), and orthographic working memory (a short-term memory system that keeps letters active until the target word is written). Collecting data from various sources allows to hypothesise that these two components are also neurally distinct. Left inferior temporal regions (overlapping with those involved in word reading) provide the neural substrate critical for the representation of orthographic lexical knowledge, whereas a region located along the left intraparietal sulcus plays a crucial role for short-term memory processes.