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Ventral Medial Prefrontal Cortex and Emotional Perseveration The

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Ventral Medial Prefrontal Cortex and Emotional Perseveration The Powered By Docstoc
					 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,DC20024-
 2188,USA
 DepartmentofPhysiologyandBiophysics,GeorgetownUniversity,Washington,DC20024-2188,USA
 ClinicalNeuroendocrinologyBranch,NIMH,9000RockuillePike,Building10,Room2046,Bethesda,MD20892,USA

 Behavioural Brain Research 146 (2003) 121-130. 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 20-55 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
                  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.

				
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posted:8/22/2011
language:English
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