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Implantable sensors for recording neural activity are often used for a variety of applications, including epilepsy studies. Current versions of these recorders are highly-invasive impractical implants and undesirable in daily life. To address this, for the first time we present a novel fully- implantable and passive system for recording characteristic epileptic activity. In this paper, we focus on recording interictal epileptiform discharges (IEDs), known indicators of clinical significance. IEDs can serve to identify the location of seizure onset zones. Notably, in the case of temporal lobe epilepsy (TLE). Here, we present IED signals recorded using neural probes previously tested with our system and demonstrated to be capable of sensing signals as low as 15 μVpp in amplitude. These recordings refer to actual animal experiments and are indicative of the broad spectrum of neural signals that can be recorded. 

Implantable systems are often employed to perform continuous high-resolution recordings of neural activity. These systems frequently require invasive procedures when implanting and maintaining effective operation. This causes major interruptions to daily life. Previous work demonstrated an in vitro minimum detectable signal (MDS) of 15 μV in amplitude and RF sensitivity down to - 135 dBm. This suggests the possibility of detecting diminutive biopotentials in a wireless fully-passive manner. Here, for the first time, we validate this system through a series of in vivo electrophysiological recordings including both spontaneous cardiac activity and sensory evoked neural activity, with amplitudes ranging from a few microvolts to millivolts and across a spectrum of frequencies. We also present design considerations and the development of probes for neurosensing to accomplish detectability of biopotentials in the tens of microvolts in rats. The developed probes show improved impedance matching with the neurosensing system. Specifically, the new probes showed an impedance several orders of magnitude lower than those commercially available, thereby significantly improving signal detection. Notably, the presented in vivo validation of this technology has great future clinical implications in neuroscience as it offers a wireless and unobtrusive device for neurological research, monitoring, and therapeutic purposes.