title: Information content with low- vs. high-T(c) SQUID arrays in MEG recordings: the case for high-T(c) SQUID-based MEG.
abstract: BACKGROUND
  Magnetoencephalography (MEG) is a method of studying brain activity via recordings of the magnetic field generated by neural activity. Modern MEG systems employ an array of low critical-temperature superconducting quantum interference devices (low-Tc SQUIDs) that surround the head. The geometric distribution of these arrays is optimized by maximizing the information content available to the system in brain activity recordings according to Shannon's theory of noisy channel capacity.
  
  
  METHODS
  Herein, we present a theoretical comparison of the performance of low- and high-Tc SQUID-based multichannel systems in recordings of brain activity.
  
  
  RESULTS
  We find a high-Tc SQUID magnetometer-based multichannel system is capable of extracting at least 40% more information than an equivalent low-Tc SQUID system. The results suggest more information can be extracted from high-Tc SQUID MEG recordings (despite higher sensor noise levels than their low-Tc counterparts) because of the closer proximity to neural sources in the brain.
  
  
  METHODS
  We have duplicated previous results in terms of total information of multichannel low-Tc SQUID arrays for MEG. High-Tc SQUID technology theoretically outperforms its conventional low-Tc counterpart in MEG recordings.
  
  
  CONCLUSIONS
  A full-head high-Tc SQUID-based MEG system's potential for extraction of more information about neural activity can be used to, e.g., develop better diagnostic and monitoring techniques for brain disease and enhance our understanding of the working human brain.
authors.affiliation: MedTech West and the Institute of Neuroscience and Physiology, Sahlgrenska Academy and the University of Gothenburg, Gothenburg, Sweden. Electronic address: justin.schneiderman@neuro.gu.se.
authors.forename: Justin F
authors.initials: JF
authors.lastname: Schneiderman
mesh_terms: D000465:Algorithms; D001921:Brain / Q000502:physiology; D001931:Brain Mapping / Q000295:instrumentation*; D003198:Computer Simulation; D006257:Head; D006801:Humans; D007257:Information Theory; D015225:Magnetoencephalography / Q000295:instrumentation*; D060306:Magnetometry
keywords: Channel capacity; High-T(c) SQUID; MEG; Neuroimaging; SQUID-sensor arrays; Total information