Many everyday tasks require sequences of multiple goals and subgoals. For example, the goal of making a sandwich may contain the subgoals of toasting the bread and spreading a condiment, which themselves consist of sequences of subgoals (e.g. getting a knife, opening the jar, etc.). Our ability to guide these actions flexiblyis known as cognitive control, and this is a primary function of the frontal cortex. Recent research has suggested that the frontal cortex is organized along the rostrocaudal axis to control cognitive tasks at different levels of abstraction (goals to sub-subgoals), or hierarchically. Most of this work, however, used non-sequential tasks;therefore, it has been only assumed that similar control mechanisms will support hierarchical control over sequences of tasks. This leaves at least three unanswered questions fundamental to our understanding of frontal lobe and cognitive control function, generally: 1) does the rostrocaudal organization of frontal cortex support hierarchical control of task sequences;2) what are the dynamics of the control and monitoring throughout task sequences;and 3) how does the control of task sequences change with learning. These three questions will be addressed across our three aims by using functional magnetic resonance imaging (fMRI) to investigate the following hypotheses: 1) the hierarchical control of task sequences is supported by the rostrocaudal organization of frontal cortex;2) monitoring will occur either in a sustained manner (throughout) or in a transient manner (at the beginning/end) for familiar task sequences;and 3) monitoring will transition from occurring in a sustained fashion over novel sequences to occurring transiently at sequence boundaries in familiar sequences with learning. The insight into the monitoring and control of task sequences that will be gained will be fundamental to the understanding of how we perform everyday tasks. This understanding is particularly crucial to the quality of life of those patients who have fronta lobe dysfunction or damage. Such patients often cannot live independently because they have trouble planning and monitoring the task sequences that are commonly required.
Patients with frontal cortical damage or dysfunction often are unable to live independently due to their inability to properly monitor and control the sequences of tasks that are common in everyday life. Although much is known about the mechanism by which the frontal cortex exerts this control over non-sequential tasks, comparatively little is known about the dynamics and structure of the brain areas that subserve sequences of tasks. The current project aims to directly investigate and broaden our knowledge of the neural systems that support the control of task sequences, which would provide the basis for progress towards frontal patients having a higher quality of life with better diagnoses and improved therapies.
|Desrochers, Theresa M; Chatham, Christopher H; Badre, David (2015) The Necessity of Rostrolateral Prefrontal Cortex for Higher-Level Sequential Behavior. Neuron 87:1357-68|