Auditory processing disorder (APD), also known as central auditory processing disorder (CAPD) is an umbrella term for a variety of disorders that affect the way the brain processes auditory information. Individuals with APD usually have normal structure and function of the outer, middle and inner ear (peripheral hearing). However, they cannot process the information they hear in the same way as others do, which leads to difficulties in recognizing and interpreting sounds, especially the sounds composing speech. It is thought that these difficulties arise from dysfunction in the central nervous system (i.e., brain). APD has been referred to as dyslexia for the ears. APD does not feature in mainstream diagnostic classifications such as the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). The American Academy of Audiology notes that APD is diagnosed by difficulties in one or more auditory processes known to reflect the function of the central auditory nervous system. APD can affect both children and adults, although the actual prevalence is currently unknown. It has been suggested that males are twice as likely to be affected by the disorder as females, but there are no good epidemiological studies. Problems of this kind originate in the brain rather than the ear. The ears role in hearing is to turn a sound wave into a neural signal. This is then transmitted up the auditory nerve to different brain regions that decode the signal. Studies of adult neurological patients have shown that if certain brain regions are damaged then it can be difficult to interpret what is heard, even though you know a sound occurred. We also know from studies of animals that there are cells in the auditory regions of the brain that respond to specific sound features, such as pitch, duration or spatial location. So it seems entirely plausible that there may be children who have developmental abnormalities of the central auditory system that affect their ability to perceive particular sound features, with consequent knock-on effects on language development. Review articles are the summary of current state of understanding on a particular research topic. They analyze or discuss research previously published by scientist and academicians rather than reporting novel research results. Review article comes in the form of systematic reviews and literature reviews and are a form of secondary literature. Systematic reviews determine an objective list of criteria, and find all previously published original research papers that meet the criteria. They then compare the results presented in these papers. Literature reviews, by contrast, provide a summary of what the authors believe are the best and most relevant prior publications. The concept of "review article" is separate from the concept of peer-reviewed literature. It is possible for a review to be peer-reviewed, and it is possible for a review to be non-peer-reviewed.
Last date updated on July, 2014