A Nonlinear Model for Hippocampal Cognitive Prosthesis: Memory Facilitation by Hippocampal Ensemble Stimulation

Abstract

Collaborative investigations have characterized how multineuron hippocampal ensembles encode memory necessary for subsequent successful performance by rodents in a delayed nonmatch to sample (DNMS) task and utilized that information to provide the basis for a memory prosthesis to enhance performance. By employing a unique nonlinear dynamic multi-input/multi-output (MIMO) model, developed and adapted to hippocampal neural ensemble firing patterns derived from simultaneous recorded CA1 and CA3 activity, it was possible to extract information encoded in the sample phase necessary for successful performance in the nonmatch phase of the task. The extension of this MIMO model to online delivery of electrical stimulation delivered to the same recording loci that mimicked successful CA1 firing patterns, provided the means to increase levels of performance on a trial-by-trial basis. Inclusion of several control procedures provides evidence for the specificity of effective MIMO model generated patterns of electrical stimulation. Increased utility of the MIMO model as a prosthesis device was exhibited by the demonstration of cumulative increases in DNMS task performance with repeated MIMO stimulation over many sessions on both stimulation and nonstimulation trials, suggesting overall system modification with continued exposure. Results reported here are compatible with and extend prior demonstrations and further support the candidacy of the MIMO model as an effective cortical prosthesis.

Hippocampal Microcircuits, Functional Connectivity, and Prostheses

“…Given also its pivotal roles in memory functions, it has been one of the most studied regions in the brain, and the first target of neural engineers in building cortical prostheses that can restore cognitive functions (Berger et al 2005(Berger et al , 2011Hampson et al 2012Hampson et al , 2013. In this chapter, we will describe the hippocampal microcircuit with an emphasis on its functional consequences in the context of building hippocampal memory prostheses for restoring memory functions.…”

A reconfigurable architecture for real-time prediction of neural activity

“…Our test data are acquired from the male Long-Evans rats aged from four to six months which are trained to perform the delayed nonmatch-to-sample (DNMS) task [11]. The hippocampal neuronal firing activities are recorded by the multielectrode array when the rats are performing the task.…”

Neurons and networks organizing and sequencing memories

“…Factors such as LTP promote the chance that groups of neurons with multiple synaptic connections will tend to fire in coordinated spatiotemporal patterns that underlie information processing for specific sensory events when frequently repeated. In previous investigations a nonlinear multi-input multi-output (MIMO) math model was employed to analyze cell firing across large neuron populations in the same structures (Berger et al 2011; Hampson et al, 2012b; Hampson et al, 2012c). In those studies it was demonstrated that the derived spatiotemporal firing patterns across all cells in the population were hierarchical, and provided important information-specific ‘firing codes’ during performance of complex memory tasks.…”