Brain Structure and Function

, Volume 220, Issue 2, pp 781–801 | Cite as

Diffusion tensor imaging of hippocampal network plasticity

  • Alejandra Sierra
  • Teemu Laitinen
  • Olli Gröhn
  • Asla PitkänenEmail author
Original Article


Diffusion tensor imaging (DTI) has become a valuable tool to investigate white matter integrity in the brain. DTI also gives contrast in gray matter, which has been relatively little explored in studies assessing post-injury structural abnormalities. The present study was designed to compare white and gray matter reorganization in the rat hippocampus after two epileptogenic brain injuries, status epilepticus (SE) and traumatic brain injury (TBI), using ex vivo high-resolution DTI. Imaging was performed at 6–12 months post-injury and findings were compared to histological analyses of Nissl, myelin, and Timm-stained preparations from the same animals. In agreement with the severity of histological damage, fractional anisotropy (FA), axial (D ||) and radial (D ) diffusivities, and mean diffusivity (MD) measurements were altered in the order SE > TBI ipsilaterally > TBI contralaterally. After SE, the most severe abnormalities were found in the dentate gyrus and CA3b–c subfields, in which the mean FA was increased to 125 % (p < 0.001) and 143 % (p < 0.001) of that in controls, respectively. In both subfields, the change in FA was associated with an increase in D || (p < 0.01). In the stratum radiatum of the CA1, FA was decreased to 81 % of that in controls (p < 0.05) which was associated with an increase in D (p < 0.01). After TBI, DTI did not reveal any major abnormalities in the dentate gyrus. In the ipsilateral CA3b–c, however, FA was increased to 126 % of that in controls (p < 0.01) and associated with a mild decrease in D (p < 0.05). In the stratum radiatum of the ipsilateral CA1, FA was decreased to 88 % of that in controls (p < 0.05). Our data demonstrate that DTI reveals subfield-specific abnormalities in the hippocampus with remarkable qualitative and quantitative differences between the two epileptogenic etiologies, suggesting that DTI could be a valuable tool for follow-up of focal circuitry reorganization during the post-injury aftermath.


Diffusion tensor imaging Epilepsy Epileptogenesis Hippocampus Magnetic resonance imaging Mossy fiber sprouting Myelin Status epilepticus Traumatic brain injury 



Axial diffusivity


Radial diffusivity


Diffusion tensor imaging


Fractional anisotropy


Fluid percussion injury


Mean diffusivity


Magnetic resonance imaging


Region of interest


Status epilepticus


Traumatic brain injury



This study was supported by the Academy of Finland (A.S., O.G., A.P.), Sigrid Juselius Foundation (A.P.), and UEF-Brain strategic funding from the University of Eastern Finland. We thank Ms. Maarit Pulkkinen for assistance in histology, Dr. Jari Nissinen and Dr. Tamuna Bolkvadze for technical assistance, MSc Juha-Pekka Niskanen for drawing the diffusion ellipsoids, and Dr. Nick Hayward for revising the language of the manuscript.

Supplementary material

Supplementary Video 1 (MPG 1415 kb)

Supplementary Video 2 (MPG 1415 kb)

Supplementary Video 3 (MPG 1415 kb)

Supplementary Video 4 (MPG 1415 kb)

Supplementary Video 5 (MPG 1415 kb)

429_2013_683_MOESM6_ESM.tif (1.2 mb)
Supplementary Figure 1. Examples of diffusion ellipsoids prepared from the control group and from two individual rats in the SE and TBI groups. Note the region specific difference in the orientation (color of the ellipsoid) as well as axial and radial diffusivities (shape of the ellipsoid) between individual animals (TIFF 1239 kb)
429_2013_683_MOESM7_ESM.docx (17 kb)
Supplementary Table 1 (DOCX 16 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Alejandra Sierra
    • 1
  • Teemu Laitinen
    • 1
  • Olli Gröhn
    • 1
  • Asla Pitkänen
    • 1
    • 2
    Email author
  1. 1.Department of Neurobiology, A. I. Virtanen Institute for Molecular SciencesUniversity of Eastern FinlandKuopioFinland
  2. 2.Department of NeurologyKuopio University HospitalKuopioFinland

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