title: Spatial information enhanced by non-spatial information in hippocampal granule cells.
abstract: The hippocampus organizes sequential memory composed of non-spatial information (such as objects and odors) and spatial information (places). The dentate gyrus (DG) in the hippocampus receives two types of information from the lateral and medial entorhinal cortices. Non-spatial and spatial information is delivered respectively to distal and medial dendrites (MDs) of granule cells (GCs) within the molecular layer in the DG. To investigate the role of the association of those two inputs, we measured the response characteristics of distal and MDs of a GC in a rat hippocampal slice and developed a multi-compartment GC model with dynamic synapses; this model reproduces the response characteristics of the dendrites. Upon applying random inputs or input sequences generated by a Markov process to the computational model, it was found that a high-frequency random pulse input to distal dendrites (DDs) and, separately, regular burst inputs to MDs were effective for inducing GC activation. Furthermore, when the random and theta burst inputs were simultaneously applied to the respective dendrites, the pattern discrimination for theta burst input to MDs that caused slight GC activation was enhanced in the presence of random input to DDs. These results suggest that the temporal pattern discrimination of spatial information is originally involved in a synaptic characteristic in GCs and is enhanced by non-spatial information input to DDs. Consequently, the co-activation of two separate inputs may play a crucial role in the information processing on dendrites of GCs by usefully combing each temporal sequence.
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hayakawa
authors.affiliation: Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Samura
authors.affiliation: Division of Membrane Physiology, Department of Cell Physiology, NIPS, Aichi, Japan.
authors.forename: Tadanobu Chuyo
authors.initials: TC
authors.lastname: Kamijo
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sakai
authors.affiliation: Graduate School of Brain Sciences, Tamagawa University, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Aihara
keywords: Dentate gyrus; Granule cell model; Spatial and non-spatial information; Temporal pattern discrimination