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This study investigated a novel multi-electrode-array (MEA) design capable of long-term and highly selective recordings of axonal signals using PDMS microtunnels. We successfully grew neurons in culture so that only axons extended through narrow (10 µm wide by 3 µm high) and long (750 µm) microtunnels under which multiple electrodes were integrated. This permitted the recording of relatively large (up to 200 µV) electrical signals, including the propagation speed and direction of these travelling action potentials. To further demonstrate the operation of the device as a diagnostic tool for drug screening assays, the drug mepivacaine was applied in washout experiments. Here, we identified significant changes in mean spiking rate and conduction velocity.

The reverberation time (RT) is an important parameter for characterizing the quality of an auditory space. Sounds in reverberant environments are subject to coloration. This affects speech intelligibility and sound localization. Many state-of-the-art audio signal processing algorithms, for example in hearing-aids and telephony, are expected to have the ability to characterize the listening environment, and turn on an appropriate processing strategy accordingly. Thus, a method for characterization of room RT based on passively received microphone signals represents an important enabling technology. Current RT estimators, such as Schroeder's method, depend on a controlled sound source, and thus cannot produce an online, blind RT estimate. Here, a method for estimating RT without prior knowledge of sound sources or room geometry is presented. The diffusive tail of reverberation was modeled as an exponentially damped Gaussian white noise process. The time-constant of the decay, which provided a measure of the RT, was estimated using a maximum-likelihood procedure. The estimates were obtained continuously, and an order-statistics filter was used to extract the most likely RT from the accumulated estimates. The procedure was illustrated for connected speech. Results obtained for simulated and real room data are in good agreement with the real RT values.

A microstamping technique has been developed for high-resolution patterning of proteins on glass substrates for the localisation of neurons and their axons and dendrites. The patterning process uses a microfabricated polydimethylsiloxane stamp with micrometer length features to transfer multiple types of biomolecules to silane-derivatised substrates, using glutaraldehyde as a homobifunctional linker. To test the efficacy of the procedure, substrates are compared in which poly-d-lysine (PDL) was physisorbed and patterned by photoresist with those stamped with PDL. Fluorescein isothiocyanate labelled poly-l-lysine was used to verify the presence and uniformity of the patterns on the glass substrates. As a biological assay, B104 neuroblastoma cells were plated on stamped and physisorbed glass coverslips. Pattern compliance was determined as the percentage of cells on the pattern 8 h after plating. Results indicate that the stamping and photoresist patterning procedure are equivalent. Substrates stamped with PDL had an average pattern compliance of 52.6 +/- 4.4%, compared to 54.6 +/- 8.1% for physisorbed substrates. Measures of background avoidance were also equivalent. As the procedure permits successive stamping of multiple proteins, each with its own micropattern, it should be very useful for defining complex substrates to assist in cell patterning and other cell guidance studies.