Although it shares cognitive neuroscience’s roots, cognitive neuropsychology has developed into a discrete discipline. While cognitive neuroscience studies neural organisation of the brain, cognitive neuropsychology concerns itself with the brain’s functional architecture; Coltheart (2010) describes this as a distinction between brain and mind. According to, among others, Coltheart (2002, cited Coltheart, 2010) this makes cognitive neuropsychology a branch of cognitive psychology rather than neuroscience.
Patient case studies have played a critical role in developing cognitive neuropsychology into a separate discipline, although data from case studies can support and even progress cognitive neuroscientific findings about neural architecture. Cognitive neuroscientific research has identified dorsal and ventral visual pathways (e.g. Shapley, 1995, cited Pike and Edgar, 2010) in the brain, known respectively as the ‘where’ and the ‘what’ pathways. A case study of patient DF by Milner and Goodale (1995, cited Pike and Edgar, 2010) found impairment in face and object recognition and visual discrimination, suggesting damage to the ventral pathway. When asked to pick up a small disc, the width of which she could not judge, the distance between DF’s index finger and thumb correlated highly with the actual disc width, suggesting that she was able to guide action using size information unavailable to conscious report. Milner and Goodale went on to develop the ventral/dorsal dissociation theory by suggesting that the ventral ‘what’ pathway processes object recognition while the dorsal ‘where’ system drives action in relation to an object (Goodale and Milner, 1992; Milner and Goodale, 1995, both cited Pike and Edgar, 2010). Thus a patient case study built on a theory about neural structure to develop a theory about cognitive processes.
Initially patients with brain damage were studied with the aim of understanding and treating their disorder. This was the case for Phineas Gage, who developed behavioural changes after a tamping iron passed through his brain in 1848 (Harlow, 1868, cited Jansari, 2010). However, progress in the field of cognitive psychology has enabled the development of complex theoretical models of cognitive function and improved research techniques. Advances in technology have given researchers the tools to view damaged brains before death and compare them to normally functioning, intact brains. As a result, a more challenging aim of cognitive neuropsychology has emerged: understanding and explaining normal cognitive processes. This is achieved by studying a deficit in cognitive function in a brain-damaged patient and making inferences about intact cognition. For example, Shallice and Warrington’s (1970, cited Hitch, 2010) investigation of patient KF with acquired brain damage showed that he had an impaired auditory digit span but normal intelligence and performance in long-term learning and memory and understanding spoken language....
