Controlling memory and resolving interference : prefrontal contributions to flexible behavior

Flow does the brain meet shifting task demands? The experiments and formal theoretical framework presented in this dissertation characterize the cognitive and neural processes by which flexible performance is enabled during task switching. Chapter 1 reviews major findings and controversies in the task switching literature, highlighting (1) evidence that behavioral switch costs may derive from proactive interference due to the facilitated retrieval of irrelevant competitors from long-term memory and (2) the consistent finding of activation in ventrolateral prefrontal cortex (VLPFC) during task switching. These observations motivate the hypothesis that left VLPFC may resolve proactive interference arising from long-term memory during a task switch. Chapters 2 and 3 describe three fMRI experiments conducted in experimental contexts independent of task switching that directly link left mid-VLPFC (Brodmann's Area 45; inferior frontal gyrus pars triangularis) to a post-retrieval selection process that resolves proactive interference from irrelevant representations retrieved from long-term memory. Chapter 4 introduces a computational model that derives its task switch cost from interference due to performance-dependent changes in its associative structure, and that resolves this interference through a control process that biases retrieved conceptual representations. Critically, a conflict signal, derived from retrieved conceptual representations in the model, is shown to be characteristic of the pattern of response in left mid-VLPFC during an fMRI experiment that manipulates preparation and interference in task switching. Furthermore, this pattern dissociates left mid-VLPFC from other regions active during a task switch.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Brain and Cognitive Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Badre, David

Advisor dc:contributor.advisor

• Anthony D. Wagner.

• Brain and Cognitive Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/32518

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/32518