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Brain Topography

, Volume 26, Issue 3, pp 468–478 | Cite as

Neurons Activated During Fear Memory Consolidation and Reconsolidation are Mapped to a Common and New Topography in the Lateral Amygdala

  • Hadley C. Bergstrom
  • Craig G. McDonald
  • Smita Dey
  • Gina M. Fernandez
  • Luke R. Johnson
Original Paper

Abstract

A key question in neuroscience is how memory is selectively allocated to neural networks in the brain. This question remains a significant research challenge, in both rodent models and humans alike, because of the inherent difficulty in tracking and deciphering large, highly dimensional neuronal ensembles that support memory (i.e., the engram). In a previous study we showed that consolidation of a new fear memory is allocated to a common topography of amygdala neurons. When a consolidated memory is retrieved, it may enter a labile state, requiring reconsolidation for it to persist. What is not known is whether the original spatial allocation of a consolidated memory changes during reconsolidation. Knowledge about the spatial allocation of a memory, during consolidation and reconsolidation, provides fundamental insight into its core physical structure (i.e., the engram). Using design-based stereology, we operationally define reconsolidation by showing a nearly identical quantity of neurons in the dorsolateral amygdala (LAd) that expressed a plasticity-related protein, phosphorylated mitogen-activated protein kinase, following both memory acquisition and retrieval. Next, we confirm that Pavlovian fear conditioning recruits a stable, topographically organized population of activated neurons in the LAd. When the stored fear memory was briefly reactivated in the presence of the relevant conditioned stimulus, a similar topography of activated neurons was uncovered. In addition, we found evidence for activated neurons allocated to new regions of the LAd. These findings provide the first insight into the spatial allocation of a fear engram in the LAd, during its consolidation and reconsolidation phase.

Keywords

Unbiased stereology Mapping Micro anatomy Stable Topography Pavlovian 

Notes

Acknowledgments

We are very grateful to Dr. Robert Ursano and the Center for the Study of Traumatic Stress (CSTS) for support. We thank Dr. Taiza Figueiredo for advice on the design of the stereology experiment.

Supplementary material

10548_2012_266_MOESM1_ESM.tif (720 kb)
Supplemental Fig. S1. The LAd was aligned across individuals using the entrance to the lateral ventricle as an anatomical landmark. (A) Representative photomicrographs (2 × magnification) of four consecutive 60 μm sections depicting (1) the area rostral to the initial opening of the lateral ventricle (LV), (2) initial opening of the LV (Bregma −3.36), and the LV at (3) Bregma −3.42 and (4) Bregma −3.48 caudal to the initial opening of the LV (B) The area of the LV was significantly different at the section rostral (Bregma −3.32) and caudal (Bregma −3.40) to the section chosen for mapping (Bregma −3.36). Circles represent the mean LV area measurement ± standard error of the mean. The red circle highlights the section used for mapping (Bregma −3.36) (TIFF 720 kb)
10548_2012_266_MOESM2_ESM.docx (12 kb)
Supplemental Table 1. Q-values for all comparisons (mass univariate ANOVA). Q-values < .1 were delineated in grey (DOCX 13 kb)
10548_2012_266_MOESM3_ESM.docx (11 kb)
Supplemental Table 2. (DOCX 12 kb)

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Copyright information

© Springer Science+Business Media New York (outside the USA) 2013

Authors and Affiliations

  • Hadley C. Bergstrom
    • 1
  • Craig G. McDonald
    • 2
  • Smita Dey
    • 4
  • Gina M. Fernandez
    • 2
  • Luke R. Johnson
    • 1
    • 3
    • 4
  1. 1.Departments of Psychiatry and NeuroscienceSchool of Medicine, Uniformed Services University (USU)BethesdaUSA
  2. 2.Department of PsychologyGeorge Mason UniversityFairfaxUSA
  3. 3.Center for the Study of Traumatic Stress (CSTS)School of Medicine, Uniformed Services University (USU)BethesdaUSA
  4. 4.Center for Neuroscience and Regenerative Medicine (CNRM)School of Medicine, Uniformed Services University (USU)BethesdaUSA

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