By Richard Liang

Monitoring the electrophysiological signals in the brain is critical for diagnosing and treating neurological diseases. The closer a sensor is to the neurons, the more accurate and precise the readings of neuronal activity can be. While sub-dural electrodes can be placed on the surface of brain tissue, issues like local tissue damage, hemorrhages, and infections can be detrimental to patient health. A study led by Dion Khodagholy from the Neuroscience Institute at New York University attempted to remedy this by developing a more accurate method of noninvasive brain mapping.

The “NeuroGrid” is a conformable neural interface device that minimizes invasiveness while still being able to record the local field potentials (LFPs) and action potentials of neurons on the cortical surface of the brain. It consists of ultrathin electrodes composed of a conducting polymer. These electrodes do not penetrate or disrupt underlying brain tissue but can still accurately monitor a large surface area due to the number of these small electrodes used. The capabilities of NeuroGrids compared to electrocorticography (ECoG), the current clinical sub-dural electrodes for diagnosing neurological disorders, were tested in conscious and anesthetized human test subjects.

Four subjects were each anesthetized with different anesthetic regimes for neurosurgery while one subject was kept awake for functional language mapping. The NeuroGrids were able to show LFP readings when the subjects were anesthetized with either propofol or sevoflurane. However, in subjects that were awake, the NeuroGrids generated more accurate readings of LFPs than the ECoG since it is a finer electrode (10 μm² ) than the conventional clinical electrode (12 mm²). NeuroGrids were also able to record neuronal spikes due to its high-density of sensors. ECoG readings also decreased precipitously with increasing distance from the site of neuronal action, while NeuroGrid readings decreased at a steady linear rate. With further testing, more accurate and precise ways to diagnose neurological disorders with minimal invasiveness can be developed.

References:

• Khodagholy, et al., Organic electronics for high-resolution electrocorticography of the human brain. Science Advances (2016)
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