Indelibility of Subcortical Emotional Memories

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Indelibility of Subcortical Emotional Memories

• Joseph E. LeDouxLizabeth RomanskiAndrew
  XagorasisLaboratory of NeurobiologyCornell
  University Medical College
• Summarized by Shauna Overgaard

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Ivan Pavlov

• Conditioned Reflexes
• Conditioned Stimulus (CS)
• Unconditioned Stimulus (US)Classical
  Conditioning

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LeDoux et al. 1984,1985,1986,1987, 1988

• Classical conditioning is mediated by projections
  from the thalamus to the amygdala.

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Affect

• Occurs after cognition in a sequential
  processing chain.
• or
• At least some aspect of emotional processing
  are organized in parallel to cortical functions.

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Is this Rule or Exception?
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Triune BrainPaul MacLean

• www.kheper.net/topics/intelligen
  ce/MacLean.htm

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Question and Findings

• Q Is visual fear conditioning, like auditory
  fear conditioning, mediated subcortically?
• A 1. Visual conditioning does not depend upon
  the integrity of the visual cortex.
• 2. Emotional memories established in the absence
  of the visual cortex persisted (resisted
  extinction) for unusually long periods of time.

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Locations of Auditory and Visual Cortices

• http//www.newhorizons.org/neuro/diamond_aging.gif

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Auditory Pathway
Nolte, 2002.  The Human Brain  An Introduction
to its Functional Anatomy, 5th Ed
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The pathway of electric signals on the optic
nerve to the visual cortex.

• http//scien.stanford.edu/class/psych221/projects/
  06/cukur/intro_files/image020.jpg

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Typical Lesion of Visual Cortex

• LeDoux, J, Romanski, L, Xagoraris, A (1989).
  Indelibility of subcortical emotional memories.
  Journal of Cognitive Science. 1, 238-243.

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What did LeDoux Do?

• Four groups of rats were given visual cortex
  lesions (VC) or sham operation (SH).
• Twenty days later, rats were given eitherpaired
  (P) or random (R) presentations of the CS
  (flashing light) and US (foot shock).
• SH VC

Pn11 Rn6
Pn10 Rn5
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Method Cont.

• Fear Conditioning the suppression of drinking by
  the CS
• Basal Lick Rate time elapsed in completing 5
  licks upon box entrance and 100 licks before CS
  presentation.
• Licking During CS the difference between the
  latency to complete 100 licks before and after
  the onset of the CS.

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The difference in time to complete 100 licks
before and after the onset of the CS.
LeDoux, J, Romanski, L, Xagoraris, A (1989).
Indelibility of subcortical emotional memories.
Journal of Cognitive Science. 1, 238-243
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Results

• Visual Cortex lesions did not interfere with
  acquisition
• - With onset of the CS, SH and VC given P
  training stopped drinking.
• - SH and VC given R training continued
  drinking.
• Visual fear conditioning is mediated by
  subcortical sensory pathways.

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Results Cont.

• With each administration of the extinction test
  the CS suppressed licking less in the sham
  operated group than in the visual cortex lesioned
  group.
• The performance of the lesioned group, did not
  change significantly over the course of 5 tests.
• LeDoux, J, Romanski, L, Xagoraris, A (1989).
  Indelibility of subcortical emotional memories.
  Journal of Cognitive Science. 1, 238-243.

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Results Cont.

• Extinction was greatly prolonged, if not
  prevented, by cortical ablation.
• http//www.wilsonsalmanac.com/
  images2/pavlov6.jpg

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Why no extinction?

• Amygdala Performs primary role of formation and
  storage/processing and memory of emotional
  reactions. Thalamus

http//www.ibiblio.org/rcip/images/Amy
gdala500_500.jpg
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Implications

• Lesions of visual cortex may prolong extinction
  by preventing the relay of visual inputs to areas
  such as the frontal cortex and/or hippocampus.
• Emotional memories established in the absence of
  sensory cortex, probably by way of
  thalamo-amygdala projections, are relatively
  indelible.
• Emotional behavior may extinguish, but the
  underlying association is not lost.