This research from the NeuroAI Lab of Martin Schrimpf, part of EPFL's Schools of Computer and Communication Sciences and Life Sciences, uses AI models to predict exactly where to stimulate the brain to evoke images of faces and specific objects in the users instead of simply evoking spots of light. The models developed at EPFL were used by Dutch researchers for live trials on sighted monkeys. The preliminary results, presented in April at the International Conference on Learning Representations, show very promising implications for vision in humans as well. "The motivation for this project is that there are many people with visual deficits that are irreparable, in the sense that somewhere along the visual processing stream, starting with the retina, there is a deficit which cannot be repaired," says Johannes Mehrer, a scientist in the NeuroAI lab who led the research. "One way of tackling this problem is to develop a visual prosthesis."

Closed-loop neuroscience experimentation, where recorded neural activity is used to modify the experiment on-the-fly, is critical for deducing causal connections and optimizing experimental time. Thus while new optical methods permit on-line recording (via Multi-photon calcium imaging) and stimulation (via holographic stimulation) of large neural populations, a critical barrier in creating closed-loop experiments that can target and modulate single neurons is the real-time inference of neural activity from streaming recordings. In particular, while multi-photon calcium imaging (CI) is crucial in monitoring neural populations, extracting a single neuron's activity from the fluorescence videos often requires batch processing of the video data. Without batch processing, dimmer neurons and events are harder to identify and unrecognized neurons can create false positives when computing the activity of known neurons. We solve these issues by adapting a recently proposed robust time-trace estimator---Sparse Emulation of Unused Dictionary Objects (SEUDO) algorithm---as a basis for a new on-line processing algorithm that simultaneously identifies neurons in the fluorescence video and infers their time traces in a way that is robust to as-yet unidentified neurons. To achieve real-time SEUDO (realSEUDO), we introduce a combination of new algorithmic improvements, a fast C-based implementation, and a new cell finding loop to enable realSEUDO to identify new cells on-the-fly with no warm-up period. We demonstrate comparable performance to offline algorithms (e.g., CNMF), and improved performance over the current on-line approach (OnACID) at speeds of 120 Hz on average. This speed is faster than the typical 30 Hz framerate, leaving critical computation time for the computation of feedback in a closed-loop setting.

To fill this gap, we introduce a nonparametric causal inference framework for analyzing "closed-loop" designs, which use

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