BioInfoBank Library

The ability to control a prosthetic device directly from the neocortex has been demonstrated in rats, monkeys and humans. Here we investigate whether neural control can be accomplished in situations where (1) subjects have not received prior motor training to control the device (naive user) and (2) the neural encoding of movement parameters in the cortex is unknown to the prosthetic device (naive controller). By adopting a decoding strategy that identifies and focuses on units whose firing rate properties are best suited for control, we show that naive subjects mutually adapt to learn control of a neural prosthetic system. Six untrained Long-Evans rats, implanted with silicon micro-electrodes in the motor cortex, learned cortical control of an auditory device without prior motor characterization of the recorded neural ensemble. Single- and multi-unit activities were decoded using a Kalman filter to represent an audio "cursor"(90 ms tone pips ranging from 250 Hz to 16 kHz) which subjects controlled to match a given target frequency. After each trial, a novel adaptive algorithm trained the decoding filter based on correlations of the firing patterns with expected cursor movement. Each behavioral session consisted of 100 trials and began with randomized decoding weights. Within 7 +/- 1.4 (mean +/- SD) sessions, all subjects were able to significantly score above chance (P < 0.05, randomization method) in a fixed target paradigm. Training lasted 24 sessions in which both the behavioral performance and signal to noise ratio of the peri-event histograms increased significantly (P < 0.01, ANOVA). Two rats continued training on a more complex task using a bilateral, two-target control paradigm. Both subjects were able to significantly discriminate the target tones (P < 0.05, Z-test), while one subject demonstrated control above chance (P < 0.05, Z-test) after 12 sessions and continued improvement with many sessions achieving over 90% correct targets. Dynamic analysis of binary trial responses indicated that early learning for this subject occurred during session 6. This study demonstrates that subjects can learn to generate neural control signals that are well suited for use with external devices without prior experience or training.

OBJECTIVE: To use metaphase II (MII) bovine oocytes as a model for MII human oocyte cryopreservation and to determine the effect of different previtrification equilibration temperatures, vitrification solutions, zona slitting, and first polar body biopsy on in vitro and in vivo developmental competence of MII human oocytes after the CryoLoop vitrification method. DESIGN: In vitro and in vivo studies. SETTING: A private infertility clinic. PATIENT(S): Women undergoing infertility treatment. INTERVENTION(S): Metaphase II stage bovine and MII human oocytes underwent first polar body biopsy before cryopreservation in different vitrification conditions, and human oocytes were fertilized by intracytoplasmic sperm injection after warming. The resulting embryos were transferred into women undergoing infertility treatment. MAIN OUTCOME MEASURE(S): Postvitrification morphologic survival, in vitro blastocyst development, and clinical outcome after ET. RESULT(S): The equilibration temperature had a significant effect on cryosurvival of both bovine and human oocytes. High (97%-99%) postvitrification survival was achieved for both MII bovine and human oocytes, and high fertilization (90%-97%) at 35 degrees C to 37 degrees C, blastocyst development (18%-45%), and pregnancy (50%) rates were achieved at 35 degrees C with 5.0 mol/L ethylene glycol + 1.3 mol/L dimethyl sulfoxide for MII human oocytes that underwent first polar body biopsy. CONCLUSION(S): Previtrification equilibration temperature had a profound effect on the postthaw developmental competence of MII human oocytes in vitro and in vivo. The CryoLoop vitrification of first polar body-biopsied MII human oocytes in the presence of 5 mol/L ethylene glycol plus 1.3 mol/L dimethyl sulfoxide gave the best results in terms of fertilization, embryo development, and implantation rates.

We hypothesized that re-entry into the cell cycle may be associated with reactive gliosis surrounding neural prostheses, and that administration of a cell cycle inhibitor (flavopiridol) at the time of surgery would reduce this effect. We investigated the effects of flavopiridol on recording quality and impedance over a 28 day time period and conducted histology at 3 and 28 days post-implantation. Flavopiridol reduced the expression of a cell cycle protein (cyclin D1) in microglia surrounding probes at the 3 day time point. Impedance at 1kHz was decreased by drug administration across the study period compared to vehicle controls. Correlations between recording (SNR, units) and impedance metrics revealed a small, but statistically significant, inverse relationship between these variables. However, the relationship between impedance and recording quality was not sufficiently strong for flavopiridol to result in an improvement in SNR or the number of units detected. Our data indicate that flavopiridol is an effective, easily administered treatment for reducing impedance in vivo, potentially through inhibiting microglial encapsulation of implanted devices. This strategy may be useful in stimulation applications, where reduced impedance is desirable for achieving activation thresholds and prolonging the lifetime of the implanted power supply. While improvements in recording quality were not observed, combination of flavopiridol with a second strategy which enhances neuronal signal detection may enhance these results in future studies.