Abstract:
Damage to the frontal structures may lead to a diverse set of changes in cognitive, behavioral, or emotional domains. While lesion studies have demonstrated distinct impairments related to pathology in different frontal regions, it is clear that the frontal lobe syndrome is not restricted to damage to frontal regions. Therefore, the broad range of impairments in executive functioning evident in neurologic disease is often referred to as the dysexecutive syndrome. This review provides an overview of how executive functioning has been traditionally defined and measured. The components of executive function such as planning, cognitive flexibility and set-shifting, initiation and self-generation, response inhibition, serial ordering and sequencing, are discussed with respect to traditional measures and neural substrates. This is followed by profiles of frontal-executive dysfunction in aging, traumatic brain injury, frontotemporal dementia, and Parkinson's disease. Since no one specific neurologic disorder has a predilection to damage isolated to the frontal lobes, profiles of the dysexecutive syndrome are related to damage to several regions in addition to the frontal lobes. Finally, there is a discussion of ecological validity and the impact of executive deficits on everyday functioning. The recent development of executive tests with greater ecological validity is reviewed and discussed, and suggestions for future directions for research are provided.