Fig. 1: High-dimensional stimulation evokes neural responses closely resembling natural firing patterns.
From: Towards precise synthetic neural codes: high-dimensional stimulation with flexible electrodes
a Schematic illustration of implanted neural MEA in a sensory cortex microcircuit model implemented in NEST. Each cortical layer (L2/3, L4, L5, L6) consists of a population of excitatory and inhibitory neurons. Extracellular electrical stimulation recruits neurons based on a simplified induced intracellular current model, which is inversely proportional to the distance from the stimulation site35,36. For clarity, only 16 electrodes of the MEA are shown in the column, although all 32 electrodes were used in the simulation. b Raster plots showing neural activity recorded from 3858 neurons at baseline and under different stimulation configurations for 60 s. All neurons receive independent Poisson background inputs, with layer and population-specific rates. Stimulation is performed by grouping 32 electrodes into 1, 2, 4, 8, 16, and 32 independent stimulation groups, with within-group electrodes sending identical current pulses. Each group’s pulse times are drawn from a Poisson distribution at 10 Hz, with an amplitude of 2 µA. c Natural (black) and stimulated (blue) neural states. Firing rates are calculated in 500 ms windows with 400 ms overlap for each group of electrodes. The resulting time-series matrix, with rows as time samples and columns as electrode indices, is projected into a 3D subspace using principal component analysis (PCA). Stimulated neural states are then projected onto the 3D PCA subspace derived from the baseline data, allowing for a direct comparison to the baseline neural activity manifold. An ellipsoid is fitted to the lower-dimensional data to estimate volume under both conditions. d The number of PCA components required to explain 85% of the variance increases as the number of independent stimulation groups increases. e The volume overlap between the baseline and stimulation-evoked manifolds increases as the number of independent stimulation groups increases. a adapted from ref. 35. licensed under CC BY-NC 3.0.
