Fig. 2: Neuro-stack as a wearable platform for recording neural activity during ambulatory behavior in humans.
a, An example research participant wearing the backpack carrying the Neuro-stack system, a single board computer with a TPU and a battery, to allow for recording of single-neuron and LFP activity during ambulatory behavior. The participant was also wearing an eye-tracking device that keeps track of head direction, pupil size changes and eye movements. Data captured from the eye-tracker were synchronized with the neural data using a programmable LED that is visible on the eye-tracker world-view camera. Wireless communication among the Neuro-stack, eye-tracker and other external monitoring devices is enabled through a Wi-Fi access point on the TPU device. b, Neural activity was recorded during an ambulatory task where participants walked repeatedly (ten times) between two opposite corners of a 5 × 5 ft2 room (from X to Y; Extended Data Fig. 2b). Example video frame from the eye-tracking world-view camera as an example participant approached point Y in the room (bottom). c, Neural activity (line noise removed, voltage-normalized separately for each channel) from 12 micro-electrode channels (1–6: hippocampus, 6–12: anterior cingulate) during the ambulatory walking task from an example participant. d, Ten seconds of filtered data from channel 12 (arrows point to corresponding sections on c and e). e, A raster plot of two single units isolated (Cluster0 and Cluster1) from channel 12. f, Cluster0 from channel 12 and its corresponding ISI histogram (right). All detected single-unit waveforms are plotted together with mean (black line) ± s.d. (dotted black line). g, Cluster1 from channel 12 and its corresponding ISI histogram (right). All detected single-unit waveforms are plotted together with mean (black line) ± s.d. (dotted black line). h, Top–down view of the hospital room layout in which an example participant walked back and forth repeatedly between points X and Y within a small area of the hospital room (~25 ft2). Points A and B represent points 1/3 and 2/3 of the XY path, respectively, and are used to define the boundary versus inner areas of the room. i, Increase in theta (3–12 Hz) bandpower when participants were located near the environmental room boundary (h, BY) compared to the inner area of the room (h, AB). *P = 5.7 × 10−5 (two-sided permutation test, n = 16 channels). On each box, the central bolded black line indicates the median, and the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers extend to the most extreme data points, minima on the bottom and maxima on the top.
