Access and organization of goal-derived categories after traumatic brain injury

This study examined the access and organization of goal-derived categories in semantic memory with a group of chronic traumatic brain injured TBI adults and a group of age and gender-matched neurologically-intact controls. Goal-derived categories are developed by individuals for use in specialized contexts to achieve a goal, such as 'things to take on a camping trip.' Categories were presented to subjects in two task contexts: category verification and exemplar generation. Overall, the TBI subjects were able to accurately identify and organize category exemplars within particular categories. Interestingly, the TBI subjects produced significantly more total responses than the neurologically-intact subjects on exemplar generation; however, a high percentage of their responses (one-third) were inaccurate, consisting of out-of-set responses and repetitions. These findings suggest that difficulties in retrieval may exist in the presence of relatively intact access and organization of goal-derived category structure. The results are discussed relative to deficits in the executive control of verifying goal-directed behaviour and incomplete category representation.