Modeling the Nonlinear Dynamic Interactions of the Lateral and the Medial Perforant Path of the Hippocampal Dentate Gyrus

We present a new method to characterize the nonlinearities resulting from the co-activity of two pathways that converge on a common postsynaptic element. We investigated the nonlinear dynamic interactions between the lateral perforant pathway (LPP) and the medial perforant pathway (MPP) of the hippocampal dentate gyms, and the effects of these cross-pathway interactions on granule cell output. A third order Volterra-Poisson modeling approach was implemented to capture the interactions between the two pathways. The kernels presented pathway specific signatures as they capture the nonlinear dynamics of each pathway individually in the form of self-kernels, and the nonlinear interactions between the two pathways in the form of cross-kernels. Data were collected in-vitro from acute slices of adult rats via a multi-electrode array recording system. The stimuli were dual-site random impulse trains with Poisson distributed inter-impulse intervals. The recorded responses from the granule cells were population spikes, simplified as discrete impulses with variable amplitudes. Our results indicated that the third order nonlinear interactions between the LPP and the MPP needs to be included in the model in order to achieve adequate predictive accuracy and indicate that this approach can be generalized to complex interactions between distinct inputs to the same set of neurons