FRONTAL-LOBE DEFICITS AFTER HEAD-INJURY - UNITY AND DIVERSITY OF FUNCTION

Deficits of ''executive function'' are commonly described following ei ther focal frontal lobe lesions or the diffuse pathology of closed hea d injury. Here, correlational methods were used to investigate common elements in different tests conventionally used to measure executive d eficits. Conventional executive (CONVEX) tests, sometimes adapted to g ive a variety of performance scores, were administered to a sample of 90 head-injured patients, along with a range of other clinical and neu ropsychological measures. Following on from previous reports showing d eficits in general intelligence or Spearman's g after frontal lobe les ions, tests relating to g were administered in a more detailed follow- up of 24 patients. The data showed uniformly low correlations between CONVEX tests, no higher indeed than correlations with others tests in the battery. Extracting more detailed scores in search of executive su bfunctions such as switching or impulse control simply produced yet lo wer correlations. Though correlations between CONVEX tests were weak, the common element that these tests did share was closely related to g and to a phenomenon we call goal neglect, or disregard of a known tas k requirement. In this head-injured sample, goal neglect and g were re lated more to generalised atrophy than to focal lesions. We suggest th at g reflects a process of forming an effective task plan by activatio n of multiple goals or action constraints. Most tests, including CONVE X tests, are to some extent sensitive to this process. Beyond this ver y general component, individual CONVEX tests may measure little of bro ad significance.