NEMAR and OpenNeuro

OpenNeuro ( is a free and open platform for validating and sharing BIDS-compliant MRI, PET, MEG, EEG, and iEEG data. OpenNeuro is the most popular platform for sharing neuroimaging data. As of Aug. 6, 2022, OpenNeuro hosts 723 public datasets comprising 27,847 participants.

What is BIDS? Neuroimaging experiments result in complicated data sets that can be arranged in many different ways. Until recently, there was no consensus on how to organize and share data obtained in neuroimaging experiments. Lack of consensus (or standard) lead to misunderstandings and time wasted rearranging data or rewriting scripts that expect a certain structure. The Brain Imaging Data Structure (BIDS), we describe a simple and easy-to-adopt way of organizing neuroimaging and behavioral data.

Why NEMAR? NEMAR is a clone and partner of OpenNeuro for MEG, EEG, and iEEG data (MEEG), supported by an NIH grant (5R24MH120037-03). The collaboration between Stanford (Russ Poldrack, the creator of OpenNeuro) and the UCSD team (Scott Makeig, Amit Majumdar, and Arnaud Delorme) is meant to provide additional MEEG tools for datasets made available for public downloads. This involves additional data quality checks (flat channels, amount of noise in EEG) and automatically preprocessed data using standard MEEG data processing pipelines. NEMAR also offers to compute resources through the NSG portal directly on the stored datasets (since NSG and NEMAR share the same infrastructure at the San Diego Supercomputer Center).

Is there a difference if I download data from NEMAR or OpenNeuro? No, there is no difference between the data being downloaded. NEMAR download only offers ZIP file downloads, while OpenNeuro offers a variety of advanced methods. We made ZIP download available because of the problem people sometimes encounter on OpenNeuro. Also, OpenNeuro uses the Amazon cloud, and download speeds are usually about ten times slower than transfers from the San Diego Supercomputer Center.

Can I upload data to NEMAR? No, you cannot. To upload data, use the OpenNeuro portal. Once a dataset is made public on OpenNeuro, within 24 hours, the dataset will automatically appear on NEMAR if it is an EEG, MEG, or iEEG dataset.