From frontal neurobehavioral disorders to executive processes

Abstract

Following the initial case report on Phineas Gage, research in the first half of the XXth century showed that damage to the frontal cortex can result in a variety of behavioral changes. In the 1960s, the introduction of experimental neuropsychological tasks marked the start of attempts to define the cognitive impairments behind these behavioral changes. From an historical perspective, this talk will focus on major conceptual accounts of frontal behavioral and cognitive disorders. Firstly, the presence of a working memory deficit in cognitive dysexecutive disorders has been evidenced by animal studies in which the dorsolateral prefrontal cortex is seen to be involved in the temporary storage of information during delayed-response tasks. Secondly, Luria suggested that the clinical diversity of frontal syndromes masked more specific impairments in situations that require goal setting, action initiation and inhibition, planning, execution of sequences (involving set-shifting and maintenance), and verification. These abilities were grouped together as executive functions by Lezak. These essential contributions enabled executive functions to be defined as central, supramodal functions that control other cognitive and behavioral abilities, and that operate predominantly in non-routine situations or in routine situations in which self-activation is required to optimize efficiency. Although a large number of tests have been initially designed to account for behavioral changes, the underlying mechanisms remain to be determined for multiple changes. Few disorders such as hypoactivity with apathy are partly accounted for by cognitive impairment. However, other dysexecutive behavioral changes are not associated with cold-cognition tests. Further advances are likely to result from the development of tests that target the socioemotional processes underlying overt behavioral changes. In the same vein, a number of laboratory experiments have provided promising paradigms for the assessment of creativity and adaptive behavior. This talk will focus on recent theoretical approaches and advances of neurobehavioral disorders. Better identification of impaired processes is expected to improve their management including remediation strategies and rehabilitation.