Browsing by Author "Hart, William"

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    Biological Considerations of Optical Interfaces for Neuromodulation
    (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2019-07) Hart, William; Kameneva, Tatiana; Wise, Andrew; Stoddart, Paul
    The success of devices such as cochlear implants and pacemakers has led to increasing interest in new applications of artificial neural interfaces, ranging from brain–computer interfaces to vagus nerve stimulators. Both the established and emerging applications of neural interfaces have highlighted the need for improvements in spatial selectivity and reduced invasiveness, which in turn has driven growing interest in optical interfaces. The delivery of light to—and collection of light from—neural tissue presents distinct challenges for optical devices. This review presents the status of optical interface technologies with a focus on biological considerations, such as biocompatibility, thermal loading, and tissue response. Attention is also paid to factors affecting the portability of optical interfaces, and issues around reliability and manufacturing that need to be considered for successful translation. Indeed, it is imperative that engineers work closely with physiologists, clinicians, and patients when developing devices for research and the clinic. Finally, emerging trends and the potential for new technologies to disrupt the field are discussed. While many engineering challenges remain to be overcome, the achievements to date suggest that optical neuromodulation techniques have significant potential to be deployed in future for a wide range of practical therapeutic applications.
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    Combined optogenetic and electrical stimulation of auditory neurons increases effective stimulation frequency—an in vitro study
    (IOP Publishing, 2020-01) Hart, William; Richardson, Rachael; Kameneva, Tatiana; Thompson, Alex; Wise, Andrew; Fallon, James; Stoddart, Paul; Needham, Karina
    OBJECTIVE: The performance of neuroprostheses, including cochlear and retinal implants, is currently constrained by the spatial resolution of electrical stimulation. Optogenetics has improved the spatial control of neurons in vivo but lacks the fast-temporal dynamics required for auditory and retinal signalling. The objective of this study is to demonstrate that combining optical and electrical stimulation in vitro could address some of the limitations associated with each of the stimulus modes when used independently. APPROACH: The response of murine auditory neurons expressing ChR2-H134 to combined optical and electrical stimulation was characterised using whole cell patch clamp electrophysiology. MAIN RESULTS: Optogenetic costimulation produces a three-fold increase in peak firing rate compared to optical stimulation alone and allows spikes to be evoked by combined subthreshold optical and electrical inputs. Subthreshold optical depolarisation also facilitated spiking in auditory neurons for periods of up to 30 ms without evidence of wide-scale Na+ inactivation. Significance These findings may contribute to the development of spatially and temporally selective optogenetic-based neuroprosthetics and complement recent developments in "fast opsins".