2.1.3. Control of illumination and detection

Light sources were controlled by a dedicated source computer, using software created in‐house and connected to a 20 MHz digital input/output card (782608–01, National Instruments) and two BrainBoxes for multiplexing and demultiplexing of signals, as detailed for previous systems (Eggebrecht et al., 2014). This setup enabled sources to be illuminated in highly temporally precise encoding patterns, allowing time and frequency coding of the source responsible for every detected signal. Detected and digitized signals were sent from the ADCs to a separate detector computer, on which another custom‐coded software program presented real‐time displays of light and noise levels and allowed for initiation and termination of data collection. For each time encoded step, a period of 104 μs between measurements allowed for detectors to recover from saturation and the analog‐to‐digital converter to settle, such that signals adjusted to the new light level without measurements bleeding in between time points.