A Diffusion Tensor Imaging Analysis of the Hippocampus and Emotion
Neuroimaging
Laboratory
Tawny Meredith-Duliba, J. Michael Williams, PhD & Karol Osipowicz, PhD
Department of Psychology, Drexel University
Department of Psychology
Department of Psychology
Department of Psychology
Analyses
INTRODUCTION
This project tested a general theory that one primary
function of the hippocampus is to encode the
emotional tone of memories so that memories have
emotional valence when recalled in the future.
Following this encoding, information is then stored in
corresponding areas of the cortex. The
hippocampus is a “pass through” system, in which
sensory information from the cortex passes through
the hippocampus, acquires encoded emotional
information from the limbic system and is then
conveyed to storage areas in the cortex. Lesion of
the hippocampus interrupts this communication
system and sensory information is not stored.
§  Tractography
§  Active regions on fMRI for pictures were
imported as seed regions
§  Generalized deterministic fiber tracking
algorithm with quantitative anisotropy
Figure 1. Tracts correlated with total memory score OBJECTIVE
Our general objective was to use DTI to identify
tracts relevant to hippocampal activation, one that is
representative of the interface between sensory
systems in the cortex and the limbic systems of
emotion generation and expression.
METHOD
Figure 2. Hippocampal regions ac:ve during visual memory encoding DTI ANALYSIS
Imaging Procedures
§  All participants were screened for Neurological,
Psychiatric, or Psychological Disorders and for
Contraindications to MRI.
Neuroimaging data were collected at Temple
University Hospital on a 3.0 T Siemens Verio
scanner using a 12-channel Siemens head coil.
§  Connectometry – used to identify tracts with
connectivity difference
§  Multiple regression – Scores for overall recall,
Emotional and Neutral recall were correlated.
§  A t-score threshold of 1.5 was used to select
fiber directions correlated with score.
§  A deterministic fiber tracking algorithm was
conducted to connect these fiber directions
using the whole brain as the ROI.
§  Tracks with length greater than 60 mm were
collected. The seeding density was 15 seed(s)
per mm^3.
§  To estimate the false discovery rate, a total of
1000 randomized permutations were applied to
the group label to obtain the null distribution of
the track length.
RESULTS
Sample
§  21 Healthy Normal Adults (10 males); age: 25 (4)
years; education: 17 (2) years (90.5% right
handed); recruited from Drexel University
Community
Department of Psychology
A total of 30 diffusion sampling directions were acquired;
The b-value was 1000 s/mm2.
Processing
§  Reconstruction
§  Subject specific Brain Mask creation
§  QSDR – q-space diffeomorphic reconstruction
with a diffusion sampling length ratio of 1.25. The
output resolution was 2 mm. (Yeh et al.
Neuroimage, 2011)
§  SPM Normalization to MNI space.
§  Each subject’s QSDR was averaged to create a
local skeleton
Regarding total memory score, the left hippocampus was
more integrated than the right and predominately
involved the posterior areas of the hippocampus (see
Figure 1 and 2).
No tracts were significantly correlated with memory
scores for neutral stimuli. Emotion stimuli accounted for
all the associations.
CONCLUSION
The relationship between memory performance and
tractography appears to be primarily driven by memory
for emotional stimuli.