Anterograde tracing of human hippocampus in vitro - a neuroanatomical tract tracing technique for the analysis of local fiber tracts in human brain

Hippocampal slices were obtained from hippocampi of patients with temporal lobe epilepsy or from patients with mass lesions located in the temporal lobe. Hippocampal slices were kept alive in a slice chamber and the anterograde tracer neurobiotin was iontophoretically injected into the granule cell layer of the dentate gyrus. Single injections resulted in the labeling of small groups of granule cells. The axonal arbor of these cells could be partially reconstructed and single mossy fibers could be followed from the soma to the inner molecular layer of the sclerotic dentate gyrus. Electron microscopy revealed asymmetric mossy fiber synapses on spiny neurons in the inner molecular layer, presumably granule cells. These data demonstrate that in vitro anterograde tracing can be employed to study the local connectivity of the human brain at the light and electron microscopic level. (C) 2002 Elsevier Science B.V. All rights reserved.