Neural mechanisms of planning: A computational analysis using event-related fMRI

Abstract

To investigate the neural mechanisms of planning, we used a novel adaptation of the Tower of Hanoi (TOH) task and event-related functional MRI. Participants were trained in applying a specific strategy to an isomorph of the five-disk TOH task. After training, participants solved novel problems during event-related functional MRI. A computational cognitive model of the task was used to generate a reference time series representing the expected blood oxygen level-dependent response in brain areas involved in the manipulation and planning of goals. This time series was used as one term within a general linear modeling framework to identify brain areas in which the time course of activity varied as a function of goal-processing events. Two distinct time courses of activation were identified, one in which activation varied parametrically with goal-processing operations, and the other in which activation became pronounced only during goal-processing intensive trials.Regions showing the parametric relationship comprised a frontoparietal system and include right dorsolateral prefrontal cortex [Brodmann's area (BA 9)], bilateral parietal (BA 40͞7), and bilateral premotor (BA 6) areas. Regions preferentially engaged only during goal-intensive processing include left inferior frontal gyrus (BA 44). The implications of these results for the current model, as well as for our understanding of the neural mechanisms of planning and functional specialization of the prefrontal cortex, are discussed. P lanning is ubiquitous in our daily lives: we plan our workday, our child's birthday party, the most efficient route through the grocery store, and the organization of a manuscript such as this one. At a finer time scale, planning occurs when we solve multicolumn addition problems or puzzles such as the Tower of London (TOL) or Tower of Hanoi (TOH). It is at this time scale that we investigate the neural circuitry involved in the planning process.Since its introduction as a task to study planning from the information-processing perspective by Simon in 1975 (1), the TOH has been a prototype task in the study of high-level cognition and problem-solving behavior (2-4). TOH and TOL have been widely used in studies of patient populations as well (5-6), whereas recent neuroimaging studies have used TOL to map planning behavior onto brain activity (7-9).Recent research has investigated the role of brain areas such as the prefrontal cortex in the service of planning. However, Goel and Grafman (10) have suggested that, whereas patient populations (5, 6) and frontal patients (11,12) show deficits in performing planning tasks, a more precise analysis in terms of information-processing mechanisms is necessary to map functionality onto explicit cognitive mechanisms. By analyzing strategy use of their patient data in terms of formally specified information-processing models as described by Simon (1), these investigators identified the focal points of difficulty in TOH in frontal patients as deficiencies in short-term memory as well as difficulties...

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Reciprocal neural response within lateral and ventral medial prefrontal cortex during hot and cold reasoning

“…Reasoning with neutral content resulted in greater activation in L/DLPFC cortex (over and above the neutral baseline) than reasoning with emotionally salient content (over and above the emotionally salient baseline). Consistent with this role, the L/DLPFC has been implicated in a series of "executive" cognitive tasks including the WCST (Drewe, 1974;Stuss et al, 2000), Tower of London (Fincham et al, 2002;Rowe et al, 2001;Shallice, 1988), the Stroop task (Perret, 1974;Weekes and Zaidel, 1996), design fluency (Jones-Gotman and Milner, 1977), cognitive estimation (Smith and Milner, 1984), planning and design (Goel and Grafman, 2000;, and tasks (like humor appreciation) requiring the "breaking of mental sets" (Goel and Dolan, 2001a;Shammi and Stuss, 1999).…”

Brain Activation in the Prefrontal Cortex during Motor and Cognitive Tasks in Adults

“…The finding suggested that these patients had deficits in inhibition control rather than planning. Nonetheless, the contribution of the PFC during the Tower of Hanoi has been verified by studies using functional Magnetic Resonance Imaging (fMRI) [7] and electroencephalogram (EEG) [8] [9]. Increased prefrontal-parietal intrahemispheric correlation was observed during the Tower of Hanoi task in both left and right hemispheres [9].…”