The frontal lobes (FL), are they a general adaptive global capacity
processor, or a series of fractionated processes? Our lesion studies
focusing on attention have demonstrated impairments in distinct processes
due to pathology in different frontal regions, implying fractionation of
the “supervisory system.” However, when task demands are
manipulated, it becomes evident that the frontal lobes are not just a
series of independent processes. Increased complexity of task demands
elicits greater involvement of frontal regions along a fixed network
related to a general activation process. For some task demands, one or
more anatomically distinct frontal processes may be recruited. In other
conditions, there is a bottom-up nonfrontal/frontal network, with
impairment noted maximally for the lesser task demands in the nonfrontal
automatic processing regions, and then as task demands change, increased
involvement of different frontal (more “strategic”) regions,
until it appears all frontal regions are involved. With other measures,
the network is top-down, with impairment in the measure first noted in the
frontal region and then, with changing task demands, involving a posterior
region. Adaptability is not just a property of FL, it is the fluid
recruitment of different processes anywhere in the brain as required by
the current task. (JINS, 2006, 12, 261–271.)