Electric stimulation fMRI of the perforant pathway to the rat hippocampus

Abstract The hippocampal formation is a brain system that is implicated in learning and memory. The major input to the hippocampus arrives from the entorhinal cortex (EC) to the dentate gyrus (DG) through the perforant path. In the present work, we have investigated the functional properties of this...

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Bibliographic Details
Published in:Magnetic resonance imaging 2008-09, Vol.26 (7), p.978-986
Main Authors: Canals, Santiago, Beyerlein, Michael, Murayama, Yusuke, Logothetis, Nikos K
Format: Article
Language:English
Subjects:
Animals
Brain Mapping - methods
Dentate Gyrus - physiology
Electric microstimulation
Electric Stimulation
Electrodes, Implanted
Electrophysiology
Entorhinal Cortex - physiology
fMRI
Functional connectivity
Hippocampus
Hippocampus - physiology
Image Processing, Computer-Assisted
Magnetic Resonance Imaging - methods
Male
Perforant Pathway - physiology
Radiology
Rats
Rats, Sprague-Dawley
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Summary:Abstract The hippocampal formation is a brain system that is implicated in learning and memory. The major input to the hippocampus arrives from the entorhinal cortex (EC) to the dentate gyrus (DG) through the perforant path. In the present work, we have investigated the functional properties of this connection by concomitantly applying electrophysiological techniques, deep-brain electric microstimulation and functional magnetic resonance imaging in anesthetized rats. We systematically delivered different current intensities at diverse stimulation frequencies to the perforant path while recording electrophysiological and blood-oxygenation-level-dependent (BOLD) signals. We observed a linear relationship between the current intensity used to stimulate the hippocampal formation and the amplitude and extension of the induced BOLD response. In addition, we found a frequency-dependent spatial pattern of activation. With stimulation protocols and train frequencies used for kindling, the activity strongly spreads ipsilaterally through the hippocampus, DG, subiculum and EC.
ISSN:0730-725X
1873-5894
DOI:10.1016/j.mri.2008.02.018