Remote effects of hippocampal damage on default network connectivity in the human brain |
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Authors: | Lars Frings Joachim Spreer Kathrin Wagner |
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Institution: | 1.Epilepsy Center,Albert-Ludwigs-University of Freiburg,Freiburg,Germany;2.Gerontopsychiatry and Neuropsychology Section, Department of Psychiatry and Psychotherapy,Albert-Ludwigs-University of Freiburg,Freiburg,Germany;3.Freiburg Brain Imaging,Albert-Ludwigs-University of Freiburg,Freiburg,Germany;4.Department of Neuroradiology,Albert-Ludwigs-University of Freiburg,Freiburg,Germany;5.Neurozentrum,Universit?tsklinikum,Freiburg,Germany |
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Abstract: | In the healthy human brain the hippocampus is known to work in concert with a variety of cortical brain regions. It has recently
been linked to the default network of the brain, with the precuneus being its core hub. Here we studied the remote effects
of damage to the hippocampus on functional connectivity patterns of the precuneus. From 14 epilepsy patients with selective,
unilateral hippocampal sclerosis and 8 healthy control subjects, we acquired functional MRI data during performance of an
object-location memory task. We assessed functional connectivity of a functionally defined region in the precuneus, which
showed the typical properties of the default network: significant task-related deactivation, which was reduced in patients
compared to control subjects. In control subjects, a largely symmetrical pattern of functional coherence to the precuneus
emerged, including canonical default network areas such as ventral medial prefrontal cortex, inferior parietal cortex, and
the hippocampi. Assessment of group differences within the default network areas revealed reduced connectivity to the precuneus
in ipsilesional middle temporal gyrus and hippocampus in left hippocampal sclerosis patients compared to controls. Furthermore,
left hippocampal sclerosis patients showed lower connectivity than right hippocampal sclerosis patients in left middle temporal
gyrus, ventral medial prefrontal cortex, and left amygdala. We report remote effects of unilateral hippocampal damage on functional
connectivity between distant brain regions associated with the default network of the human brain. These preliminary results
underline the impact of circumscribed pathology on functionally connected brain regions. |
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