Electric stimulation fMRI of the perforant pathway to the rat hippocampus

Nikos Logothetis, Santiago Canals, Michael Beyerlein, Yusuke Murayama, Nikos K. Logothetis

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    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. © 2008 Elsevier Inc. All rights reserved.
    Original languageEnglish
    Pages (from-to)978-986
    Number of pages8
    Issue number7
    Publication statusPublished - Sept 2008


    • Electric microstimulation
    • Electrophysiology
    • fMRI
    • Functional connectivity
    • Hippocampus


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