Models of executive functioning

Abstract

Scientists have approached executive functioning (EF) from a variety of perspectives, including neuroanatomical, neurochemical, evolutionary, syndrome-based, and statistical. Many have attempted to concisely define EF and executive dysfunction (EdF) by listing functions or underlying operations, while others have focused on its neuroanatomical or neurophysiological correlates. There is some degree of overlap among these descriptions, but no consensus. Perhaps the confusion regarding exactly what constitutes EF reflects the ways in which it has been examined historically. Early studies were adult-based , examining behaviors produced by brains that had already developed. These studies, while informative about adults with acquired EdF, did not take into account issues of development, such as how an insult impacts EF in a still-developing brain or how neurodevelopmental disorders impact brain and function. Early work in the field primarily examined the effects of insults to the frontal lobes , which led to a circular argument that “damage to the frontal lobes causes EdF, therefore EF must be regulated by the frontal lobes.” This was later refined and modified with attribution of EF to the prefrontal cortex (PFC), but the assumption of one-to-one correspondence between function and structure, with limited consideration of the rich network we now know is involved in EF, remained the dominant model. Yet this model failed to account for evidence of intact functioning after removal of the frontal lobe, EdF experienced after damage to other brain areas, or evidence of EdF in the absence of a known neurologic insult (as is the case with some of the neurodevelopmental disorders).