Cognitive neuropsychology

History

The connection between brain injuries and functions was first documented in the 16th century BC, in the Edwin Smith Papyrus of Ancient Egypt.

In 1522, Italian physician Jacopo Berengario da Carpi wrote in his treatise De Fractura Calvae sive Craniei that brain injuries resulted in vertigo (as well as vomiting, haemorrhages, aphasia). In 1825, French physician Jean-Baptiste Bouillaud proposed that lesions of the frontal lobe were responsible for disturbances in speech.

In 1848, Phineas Gage became a classic subject for studying the connection between the prefrontal cortex and behavior, decision-making, and consequences when an explosion accident pierced his brain with an iron rod.

Cognitive neuropsychology has its roots in the diagram-making approach to language disorder that started in the second half of the 19th century. The discovery that aphasia takes different forms depending on the location of brain damage provided a powerful framework for understanding brain function.

In 1861, Paul Broca reported a post mortem study of an aphasic patient who was speechless apart from a single nonsense word: "Tan". Broca showed that an area of the left frontal lobe was damaged. As Tan was unable to produce speech but could still understand it, Broca argued that this area might be specialised for speech production and that language skills might be localized to this cortical area. Broca did a similar study on another patient, Lelong, a few weeks later. Lelong, like Tan, could understand speech but could only repeat the same five words. After examining his brain, Broca noticed that Lelong had a lesion in approximately the same area as his patient Tan. He also noticed that in the more than 25 patients he examined with aphasia, they all had lesions to the left frontal lobe but there was no damage to the right hemisphere of the brain. From this he concluded that the function of speech was probably localized in the inferior frontal gyrus of the left hemisphere of the brain, an area now known as Broca's area.

Karl Wernicke subsequently reported patients with damage further back in the temporal lobe who could speak but were unable to understand what was said to them, providing evidence for two potentially interconnected language centres. These clinical descriptions were integrated into a theory of language organisation by Lichtheim. Subsequently, these models were used and developed to inform Dejerine's account of reading, Liepmann's theory of action and Lissauer's 1890 account of object recognition and Lewandowsky and Stadelmann's 1908 account of calculation.

However, the early 20th century saw a reaction to the overly-precise accounts of the diagram-making neurologists. Pierre Marie challenged conclusions against previous evidence of Broca's areas in 1906 and Henry Head attacked the whole field of cerebral localisation 1926.

The modern science of cognitive neuropsychology emerged during the 1960s stimulated by the insights of the neurologist Norman Geschwind who demonstrated that the insights of Broca and Wernicke were still clinically relevant. The other stimulus to the discipline was the cognitive revolution and the growing science of cognitive psychology which had emerged as a reaction to behaviorism in the mid-20th century. Psychologists in the mid-1950s acknowledged that the structure of mental information-processing systems could be investigated in scientifically acceptable ways. They developed and applied new cognitive processing models to explain experimental data from not only studies of speech and language but also those of selective attention. Cognitive psychologists and clinical neuropsychologists developed more research collaborations to gain a better understanding of these disorders. The rebirth of neuropsychology was marked by the publishing of two seminal collaborative papers from Marshall & Newcombe (1966) on reading and Warrington & Shallice (1969) on memory. Subsequently, work by pioneers such as Elizabeth Warrington, Brenda Milner, Tim Shallice, Alan Baddeley and Lawrence Weiskrantz demonstrated that neurological patients were an important source of data for cognitive psychologists.

It took less than one decade for neuropsychology to be fully re-established. More achievements in neuropsychology were recognized: the establishment of the first major book discussing neuropsychology using a cognitive approach, Deep Dyslexia, in 1980 after a scientific meeting about the topic in Oxford in 1977, the birth of the Cognitive Neuropsychology journal in 1984, and the publishing of the first textbook of neuropsychology, Human Cognitive Neuropsychology in 1988.

A particular area of interest was memory. Patients with amnesia caused by injuries to the hippocampus in the temporal cortex and midbrain areas (especially the mamillary bodies) were of early interest. A patient with severe case of amnesia will not be able to remember meeting the examiner if they leave the room and return, let alone events of the previous day (episodic memory), but they will still be able to learn how to tie their shoes (procedural memory), remember a series of numbers for a few seconds (short-term memory or working memory) and be able to recall historical events they have learned in school (semantic memory). By contrast, patients may lose their short-term memory abilities while retaining their long term memory functions. Many other studies like this have been done in the field of neuropsychology examining lesions and the effect they have on certain areas of the brain and their functions.

Studies on the amnesic patient Henry Molaison, formerly known as patient H.M., are commonly cited as some of the precursors, if not the beginning of modern cognitive neuropsychology. Molaison had parts of his medial temporal lobes surgically removed to treat intractable epilepsy in 1953. Much of the hippocampus was also removed along with the medial temporal lobes. The treatment proved successful in reducing his dangerous seizures, but left him with a profound but selective amnesia. After the surgery, Molaison was able to remember some big events from before the surgery, such as the stock market crash in 1929, but was confused about many others and could no longer form new memories. This accidental experiment showed scientists how the brain processes different types of memory. Because Molaison's impairment was caused by surgery, the damaged parts of his brain were known, information which was usually not knowable in a time before accurate neuroimaging became widespread. Scientists concluded that while the hippocampus is needed in the creation of new memories, it is not needed in the retrieval of old ones; they are two separate processes. They also realized that the hippocampus and the medial temporal lobes, both of the areas removed from Molaison, are the areas responsible for converting short-term memory to long-term memory.

Much of the early work of cognitive neuropsychology was carried out with limited reference to the detailed localisation of brain pathology. Neuroimaging was relatively imprecise and other anatomically based techniques were also limited. The emphasis of many researchers as late as 1990 was on the analysis of patterns of cognitive deficit rather than on where the injury was located. Despite the lack of detailed anatomical data, studies of reading, language and memory had a number of important implications. The first is that certain cognitive processes (such as language) could be damaged separately from others, and so might be handled by distinct and independent cognitive (and neural) processes. (For more on the cognitive neuropsychological approach to language, see Eleanor Saffran, among others.) The second is that such processes might be localized to specific areas of the brain. Whilst both of these claims are still controversial to some degree, the influence led to a focus on brain injury as a potentially fruitful way of understanding the relationship between psychology and neuroscience.