PT - JOURNAL ARTICLE AU - Christoph Pfeiffer AU - Silvia Ruffieux AU - Lars Jönsson AU - Maxim L. Chukharkin AU - Alexei Kalaboukhov AU - Minshu Xie AU - Dag Winkler AU - Justin F. Schneiderman TI - A 7-channel high-<em>T</em><sub>c</sub> SQUID-based on-scalp MEG system AID - 10.1101/534107 DP - 2019 Jan 01 TA - bioRxiv PG - 534107 4099 - http://biorxiv.org/content/early/2019/01/31/534107.short 4100 - http://biorxiv.org/content/early/2019/01/31/534107.full AB - Due to their higher operating temperature, high-Tc superconducting quantum interference devices (SQUIDs) require less thermal insulation than the low-Tc sensors that are utilized in commercial magnetoen-cephalography (MEG) systems. As a result, they can be placed closer to the head, where neuromagnetic fields are higher and more focal, potentially leading to higher spatial resolution. The first such on-scalp MEG measurements using high-Tc SQUIDs have shown the potential of the technology. In order to be useful for neuroscience and clinical applications, however, multi-channel systems are required. Herein, we present a 7-channel on-scalp MEG system based on high-Tc SQUIDs. The YBCO SQUID magnetometers are arranged in a dense, head-aligned hexagonal array inside a single, liquid nitrogen-cooled cryostat. The spacing between the magnetometers and the head is adjustable down to 1 mm. The sensors are side-mounted on the cryostat that is mounted on an articulated armature for recordings on arbitrary head locations of a seated subject. We demonstrate white noise levels of 50-130 fT/Hz1/2 at 10 Hz, sensor-to-sensor crosstalk values of &lt;0.6%, and single-fill operation times of 16 hours. We validate the system with MEG recordings of visual alpha modulation and auditory evoked fields. The system is thus useful for densely and sensitively sampling neuromagnetic fields over any ∼ 10 cm2 patch of the scalp surface over the course of a day.