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Neuroimage. 2015 Feb 15;107:229-241. doi: 10.1016/j.neuroimage.2014.10.039. Epub 2014 Oct 22.

Optogenetic fMRI reveals distinct, frequency-dependent networks recruited by dorsal and intermediate hippocampus stimulations.

Author information

1
Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA.
2
Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.
3
Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA.
4
Department of Neuroscience, University of California, Los Angeles, CA 90095, USA.
5
Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Neuroscience, University of California, Los Angeles, CA 90095, USA; Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA.
6
Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA; Department of Psychology, University of California, Los Angeles, CA 90095, USA.
7
Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA; Department of Neurosurgery, Stanford, CA 94305, USA. Electronic address: ljinhy@stanford.edu.

Abstract

Although the connectivity of hippocampal circuits has been extensively studied, the way in which these connections give rise to large-scale dynamic network activity remains unknown. Here, we used optogenetic fMRI to visualize the brain network dynamics evoked by different frequencies of stimulation of two distinct neuronal populations within dorsal and intermediate hippocampus. Stimulation of excitatory cells in intermediate hippocampus caused widespread cortical and subcortical recruitment at high frequencies, whereas stimulation in dorsal hippocampus led to activity primarily restricted to hippocampus across all frequencies tested. Sustained hippocampal responses evoked during high-frequency stimulation of either location predicted seizure-like afterdischarges in video-EEG experiments, while the widespread activation evoked by high-frequency stimulation of intermediate hippocampus predicted behavioral seizures. A negative BOLD signal observed in dentate gyrus during dorsal, but not intermediate, hippocampus stimulation is proposed to underlie the mechanism for these differences. Collectively, our results provide insight into the dynamic function of hippocampal networks and their role in seizures.

KEYWORDS:

Brain mapping; Functional MRI; Hippocampus; Optogenetics; Seizure

PMID:
25462689
PMCID:
PMC4409430
DOI:
10.1016/j.neuroimage.2014.10.039
[Indexed for MEDLINE]
Free PMC Article

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