Biology subjects

Markos, C.

Publications and source records attributed to Markos, C..

3 recordsLinked to original sources

bioRxiv2023

In vivo multi-site electrophysiology enabled by flexible optrodes towards bi-directional spinal cord interrogation

Optical neural interfaces combining optogenetics and electrophysiology have been demonstrated as powerful tools for distinguishing the causal roles of neural circuits in the nervous system. Functional optrodes for multipoint stimulation and recording have already been demonstrated in the brain. However, soft and flexible multimodal optrodes for the purpose of probing the spinal cord have remained undeveloped. Here, we present the design and fabrication of a novel optrode for multi-site optical stimulation and electrical recording in the spinal cord by combining optical fiber drawing of polymer material, laser micromachining, and integration of tungsten microelectrodes in a monolithic fiber-based structure. The results from space-resolved scattering measurements, electrochemical impedance spectroscopy, and an acute in vivo electrophysiology experiment in an anesthetized rodent suggest this probe as a potential novel interface, which can serve as a part of therapeutic strategies against neurological conditions and injury in the spinal cord.

neuroscience↗

bioRxiv2022

Mapping whole brain effects of infrared neural stimulation with positron emission tomography

The combination of neuroimaging and targeted neuromodulation is a crucial tool to gain a deeper understanding of neural networks at a circuit level. Infrared neurostimulation (INS) is a promising optical modality that allows to evoke neuronal activity with high spatial resolution without need for the introduction of exogenous substances in the brain. Here, we report the use of whole-brain functional [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) imaging during INS in the dorsal striatum, performed using a multifunctional soft neural probe. We demonstrate the possibility to identify multi-circuit connection patterns in both cortical and subcortical brain regions within a single scan. By using a bolus plus infusion FDG-PET scanning protocol, we were able to observe the metabolic rate evolution in these regions during the experiments and correlate its variation with the onset of the INS stimulus. Due to the focality of INS and the large amount of viable molecular targets for PET, this novel approach to simultaneous imaging and stimulation is highly versatile. This pilot study can pave the way to further understand the brain connectivity on a global scale.

neuroscience↗

bioRxiv2022

Opsin-free optical neuromodulation and electrophysiology enabled by a soft monolithic infrared multifunctional neural interface

Controlling neuronal activity with high spatial resolution using multifunctional and minimally invasive neural interfaces constitutes an important step towards developments in neuroscience and novel treatments for brain diseases. While infrared neuromodulation is an emerging technology for controlling the neuronal circuitry, it lacks soft implantable monolithic interfaces capable of simultaneously delivering light and recording electrical signals from the brain while being mechanically brain-compatible. Here, we have developed a soft fibre-based device based on high-performance thermoplastics which are >100-fold softer than silica glass. The presented fibre-implant is capable of safely neuromodulating the brain activity in localized cortical domains by delivering infrared laser pulses in the 2 m spectral region while recording electrophysiological signals. Action and local field potentials were recorded in vivo in adult rats while immunohistochemical analysis of the tissue indicated limited microglia and monocytes response introduced by the fibre and the infrared pulses. We expect our devices to further enhance infrared neuromodulation as a versatile approach for fundamental research and clinically translatable therapeutic interventions.

neuroscience↗