The Bell Curve and Standarised Scores

In order to assert clinical opinion toward a patients raw data test results from varying sources should be assimilated into a common metric (standardisation). Percentiles tell us the rarity or abnormality of an individual's score. They are easily understandable and communicable but are not linear and so the difference between the 10-20th percentile in comparison to the 20-30th percentile is not necessarily the same. Z scores on the other hand, are linear transformations. They indicate with positive and negative values how many standard deviations a score is away from its mean. However, working in negative can present communication problems and z scores tend to get lost in translation when communicating with non-neuropsychologists. A common alternative is to use T scores (mean=50, SD=10) which offers a balanced level of incrementation. Others prefer index scales (mean 100, SD 15) which are often received with familiarity as they are used in the measurement if IQ. However, the fact that they are used in IQ can bring unwanted misconception when communicating interpretation and opinion.

Executive Function Brief Conceptualisation

Executive function is sometimes thought of as the functional equivalent of the frontal lobes. In 1982 Cummings proposed a fronto-straital circuits account of executive functioning and how it relates to structural circuits between the straitum located subcortically as part of the input to the basal ganglia, and the frontal lobes. In terms of executive function three specific areas are important within the fronto-straital circuits: the dorsolateral prefrontal cortex, which is typically concerned with tradional executive functions of planning, organisation and regulation. The orbitofrontal cortex (behind the orbits of the eye sockets) is more concenred with inhibition and decision making and social cogntion. Whilst the anterior cingulate is concerned with motivation. Dr Simon Gerhand of Bristol's Frenchay Brain Injury Rehabilitation Centre, practically summarises executive tests into the following: Executive function test types. Generativety: verbal fluency, design fluency. These are probably the only executive tests which lateralise. Planning: Tower test, zoo map test, Key search test, SET. Judgement: cognitive estimates, 20 questions, temporal judgement. Inhibition: Stroop, Hayling. Mental flexibility: Trails, Brixton, rule shift, WCST. Social-emotional: Baron Cohen E-Q and faux pas (not standardised) A way of remembering these dichotomies is: 'GP Jim's' model of executive function tests.