A nonlinear model for hippocampal cognitive prosthesis: memory facilitation by hippocampal ensemble stimulation.

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.

Interference in clinical chemistry assays by the hemoglobin-based oxygen carrier, Hemospan.

OBJECTIVE: To evaluate interference by the hemoglobin-based oxygen carrier Hemospan on clinical laboratory assays. DESIGN AND METHODS: Interfering Hemospan concentrations were determined for general chemistry and cardiac marker analytes in pooled serum and the corresponding hemolysis index was calculated. RESULTS: Hemospan did not interfere with 20 of 35 analytes. Hemospan produced a negative interference in serum creatinine, amylase, alkaline phosphatase, uric acid, and GGT assays and a positive interference in serum phosphate, LDH, iron, triglycerides, total protein, AST, cholesterol, magnesium, and albumin assays, and appeared to positively bias the serum cardiac troponin I (cTnI) assay only when cTnI is present in the sample. CONCLUSIONS: We present a report of assays affected by Hemospan and the threshold concentrations for interference. This study highlights the importance of interference studies in understanding the effects of hemoglobin-based oxygen carriers on results reported by the clinical laboratory.