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Chapter 22
Neuropsychology testing the brain
SALLIE BAXENDALE
Institute of Neurology, University College London, National Hospital for Neurology and
Neurosurgery, Queen Square, London, and Epilepsy Society, Chalfont St Peter,
Buckinghamshire
Defining and testing cognitive function
Cognitive function is the process by which an individual takes in information about the world,
makes sense of it and acts upon it. Neuropsychological tests traditionally assess function in
different cognitive domains, all of which can dissociate in the pathological brain. These
domains have a conceptual rather than an anatomical basis, although some anatomical
correlates do exist. The domains include intelligence, language, memory, perception and
executive functions. The way in which a function is tested can to a large extent determine
whether a deficit will be found. For example, there is no single test of ‘verbal memory’.
Memory tests can assess the learning, recall or recognition of different types of verbal
material (narrative vs unstructured) presented during the testing session, in addition to long-
term autobiographical recall and prospective memory skills. The distinction between
declarative memory (encompassing episodic memory the recollection of experiences and
episodes, and semantic memory and knowledge of the world) and procedural memory
(remembering how to do something, e.g. riding a bicycle) can also be made. Again, all of
these abilities have been shown to dissociate in patients with focal lesions.
The majority of neuropsychological tests tap multiple skills from more than one domain. For
example, success on a complex figure recall task, ostensibly a visual memory test, also
requires intact perception and adequate comprehension, concentration and praxis. It follows
therefore that failure on this test may be the result of a breakdown in any one or a number of
these processes. The aim of the neuropsychological assessment is not only to identify and
quantify deficits in cognitive function, but more importantly to try to identify which processes
are breaking down and responsible for the dysfunction. This is normally achieved by the
careful interpretation of an individual’s performance and scores on a wide range of tests.
When is neuropsychology useful in epilepsy?
Neuropsychological test results rarely stand alone but are interpreted in relation to both the
clinical question being asked (be it a diagnostic issue, the lateralisation or localisation of
dysfunction, or the planning of an intervention) and the results from other investigations.
There are numerous factors that can influence an individual’s performance on
neuropsychological tests. Many of these factors are specific to epilepsy and can be fixed,
transient or have a progressive influence (Figure 1).
