The role of the basal ganglia in monitorization of frontal lobe function

Objective. To review current understanding of the mechanisms controlling the activity of the frontal lobes and consider simple explanations of hypotheses regarding this. Development. We describe the basic functional anatomy of the frontal cortex and its relation to the basal ganglia by means of five parallel fronto-subcortical circuits (motor, oculomotor, dorsolateral, orbitofrontal and anterior cingulate. From the functional point of view we emphasize that the frontal cortex can keep certain zones active in relation to relevant tasks, and can be very flexible. These properties form the so-called anterior attention system. We describe various recent models explaining frontal cortical activity in these terms, and emphasize those based on fronto-subcortical circuits. These circuits control motor, cognitive, social and emotional behaviour. Conclusions. The cortical activity of the frontal lobes is regulated by various parallel, segregated fronto-subcortical circuits. These circuits permit the selection and maintenance of activity of particular cortical regions regarding relevant conduct, whilst irrelevant conduct is inhibited, In this way they constitute the basic functional mechanism of the attention system described above. For prediction of the relevance or irrelevance of the consequences of each new stimulus, the anterior cingulate cortex probably establishes comparisons with previous situations which have already been stored together with certain 'somatic markers' which indicate their emotional significance for the organism. This cortex fulfils the anatomical conditions necessary for regulation of the activity of the basal ganglia together with the whole frontal cortex so as to permit behaviour which is orderly from the time aspect.