Ventral Medial Prefrontal Cortex and Emotional Perseveration: The Memory for Prior Extinction Training Maria A. Morgan, Jay Schulkin, Joseph E. LeDoux DepartmentofPsychology,NewYorkUniversity,NewYork,NY,USA CenterforNeuralScience,NewYorkUniversity,4WashingtonPI,Room809,NewYork,NY1003,USA ResearchDepartment,AmericanCollegeofObstetriciansandGynecologists,40912thSt.,SW,Washington,DC ,USA DepartmentofPhysiologyandBiophysics,GeorgetownUniversity,Washington,DC ,USA ClinicalNeuroendocrinologyBranch,NIMH,9000RockuillePike,Building10,Room2046,Bethesda,MD20892,USA Behavioural Brain Research 146 (2003) Online [Available] elsevier.com/locate/bbr. Summarized by Shannon Juedes

How might mPFCv be involved in regulating extinction? An inhibitory association develops in competition with the excitatory association developed during acquisition. IL cortex is the crucial portion of mPFCv involved in extinction. mPFCv is involved in utilizing the inhibitory association that develops during extinction. –Inhibitory is less stable and is dependent on the extinction context for expression. mPFCvs may influence contextual conditioning and extinction by helping to integrate information about the internal environment wit the external environment.

How did this study come about? Lesioned rats exhibited emotional perseveration. Concluded that mPFCv plays a role in regulating fear inhibition during the extinction process. Medial prefrontal cortex is involved in the extinction component of conditioned fear learning.

Prior Studies Morrow et al. – mPFCv lesions disrupt extinction performance, whether lesions were made prior to or following acquisition training. Quirk – The infralimbic cortex of the mPFCv is important for the retention of extinction.

Objectives Two objectives 1.To examine the impact of post-acquisition lesions on the retention and extinction of fear responses 2.To examine the effectiveness of extinction by determining the extent to which reacquisition of fear responses is affected by prior extinction. Lesioned animals would express more fear than controls during reacquisition, which would indicate that prior extinction trials were less effective in guiding their behavior.

Procedure Male Sprague-Dawley rats –Housed in pairs upon arrival for 9 days –Unlimited assess to rat food and water –12-h light:12-h dark cycles –6 days later received 1 day context habituation and 2 days acquisition training Rats in cages for min CS: sound US: shock –Freezing response was the measure of conditioned emotional responding (fear acquisition). –Surgery day after 2 groups—mPFCv (prelimbic/infralimbic cortical regions) and control

Procedure –14-day recovery period –Extinction trials 2 consecutive days of 5 s or fewer spent freezing –2-3min later “reinstating US” Ineffective in reinstating a CR to a CS for both control and lesioned animals –Extinction trials day after

Procedure –Reacquisition training next day 4 groups –Control-delay (6) and mPFCv-delay (8) –Control-no-delay (7) and mPFC-no-delay (9) –Reextinction trials to criterion

Results

When lesioned following acquisition training, mPFCv-lesioned animals responded less to the context than did controls. L animals extinguished their response at the same rate as controls to the context. L animals responded significantly more than control animals to both the context and CS upon reacquisition. L animals showed resistance to extinction during reextinction relative to their own performance during the initial extinction session.

Implications Changes in mPFCv may predispose one to develop fear responses that are difficult to extinguish or otherwise treat. Functional activity in the mPFC and amygdala are inversely related.