ABSTRACT The instrument requested is a whole-cortex high-density magnetoencephalography (MEG) system that is needed to continue performing NIH-funded brain research: the Megin Triux neo 306-channel whole-head MEG system which has 100% helium recovery and is able to record up to 128 channels of EEG simultaneously. The requested MEG unit will replace an 18-year-old 306-channel VectorView UCSD Core-facility MEG purchased in 2004 – the oldest surviving such unit in the US, which is beyond end-of-life, deteriorating, wasteful of helium, and no longer supported by the manufacturer Megin. The Triux neo is two generations beyond the current VectorView but uses identical sensor configurations so that all software is fully compatible between models, and our prior/ongoing NIH-funded experiments can be continued on the new system without interruption. The new instrument will be housed within the current high-performance 3-layer magnetically shielded room and will have additional software and hardware features to permit recordings of cortical activity with excellent signal-to-noise, with millisecond temporal resolution, and 1-mm spatial resolution in phantom studies. The system includes behavioral stimulation equipment and computers to control perceptual, cognitive, and motor experiments. The current old MEG system established in 2005 comprises the official UCSD MEG Core Facility, and is the only MEG unit in Southern California, and one of only two MEG units in California (the other is at UCSF). The proposed replacement Core MEG instrument will be located within UCSD's multi-departmental, multi-institutional Qualcomm Institute (QI), and will be operated and administered through the same successful infrastructure since its founding in 2005. The UCSD MEG Core Facility already is the hub of a broad research effort that serves many research programs funded by NIH, VA, DOD, and NSF, as well as nongovernmental funding sources. Major Users of the proposed MEG instrument come from the Radiology, Psychiatry, Neuroscience, and Cognitive Science Departments at UCSD, as well as San Diego State University, UC Davis, UC Irvine; and is available to researchers from other institutions. MEG directly and instantaneously reflects synaptic current flows. It thus has excellent temporal resolution and complements the good spatial resolution provided by fMRI. Researchers using the MEG can also access fMRI at the nearby UCSD Center for Functional MRI (CFMRI), which provides a wide range of relevant collaborative expertise, including advanced techniques for localizing distributed cortical sources by integrating MEG and EEG with structural and functional MRI. The featured NIH-supported projects that will immediately benefit from the MEG system include ongoing MEG studies of nicotine and cannabis on young-adult brain function; effects of cannabis and cumulative adversity on brains of young-adults with HIV; pediatric traumatic brain injury; and studying memory in epilepsy patients.