Medical Research: What is the background for the NeuroGrid device?
Dr. Buzsaki: The main form of communication among neurons in the brain occurs through action potentials (‘spikes’). Understanding the mechanisms that translate spikes of individual neurons into perceptions, thoughts, and actions requires the ability to monitor large populations of neurons at the spatial and temporal resolution of their interactions.
We developed a novel, organic material-based, ultra-conformable, biocompatible and scalable neural interface array (the ‘NeuroGrid’) with neuron-size density electrodes capable of acquiring action potential of individual neurons from the surface of the brain.
The NeuroGrid has several innovative characteristics that overcome limitations in current methods of surface recording:
(i) light-weight and conformable architecture to establish stable electrical and mechanical contacts, thereby ensuring minimal damage to underlying tissue;
(ii) efficient abiotic/biotic interface resulting in a high signal to noise ratio and the ability to resolve spikes. This is achieved by using conducting polymers as the interfacing material. Conducting polymers are mix conductors, they can conduct electronics and ionic currents hence they can efficiently transduce ion based neural activity into electronic signals
(iii) scalable neuron-size density electrodes to allow isolation and characterization of multiple individual neurons’ action potential across the cortical surface.
Medical Research: What are the main findings from your early findings in rats and humans?
Dr. Buzsaki: We have recorded action potentials from superficial cortical layers of rodents and humans with high fidelity and extended duration with highly conformable, non-penetrating NeuroGrids. The high signal to noise ratio of the acquired signals permitted analysis of entrainment of spiking activity to brain oscillations. We were also able to acquire multiunit spike-resolution data from epilepsy surgery patients with this biocompatible array, highlighting its translational potential.
Medical Research What should clinicians and patients take away from your report?
Dr. Buzsaki: The NeuroGrid’s ultra-thin (4 µm) and conformable architecture allows it to closely follow the fine irregularities of the neocortical surface topography. In contrast to conventional clinical subdural ECoG arrays, NeuroGrid can be folded and inserted into brain regions currently inaccessible to recording with surface electrodes. Clinically, this feature will facilitate acquiring data directly from the cortex lining fissures and sulci in the human brain, areas that can harbor difficult to diagnose epileptic lesions.
Furthermore, the NeuroGrid is composed of ‘soft’ organic electronics; it has high mechanical compatibility with brain tissue compared to ‘hard’ electronics, minimizing long-term impact on the cortical surface.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Buzsaki: Although numerous hurdles must be overcome for safe and reliable recordings in patients, large-scale, chronically recorded data generated by the NeuroGrid has broad applicability to the understanding of physiologic and pathologic network activity, control of brain-machine interfaces, and therapeutic closed-loop stimulation in brain disease.