The Frontal Lobes and Hierarchical Organization of Cognitive Control

The Jacksonian theory of hierarchical control has had a clear impact on the development of modern neuroscience. Hughlings Jackson's concepts of hierarchical control pertained to the structural organization of the central nervous system rather than to cognitive constructs. Perseverations occupy a special place within the rich phenomenologic domain of cognitive pathology associated with frontal lobe damage. In cases with massive frontal lobe lesions, however, task demands may be minimal and still precipitate perseveration and perseverative responses may be observed even in the execution of simple motor tasks. An extensive literature leads to the conclusion that massive, focal prefrontal damage almost invariably implies the presence of perseveration characterized by horizontal and vertical pervasiveness. Cognitive involution due to diffuse disease in humans can be viewed as dominated by frontal lobe dysfunction. An illustration of double dissociation principles appears to be provided by applications of both structural and functional brain-imaging techniques in investigations of the schizophrenic syndrome.