Volumetric mesoscopic electrophysiology: a new imaging modality for the non-human primate.

A new recording method called MePhys uses 992 electrode contacts across 62 shafts implanted in a monkey hemisphere to measure brain activity at a mesoscopic scale, bridging the gap between fMRI, EEG, and microelectrode techniques. By analyzing over 300,000 simultaneously recorded electrode pairs, the method reveals that a subanesthetic dose of ketamine, which mimics aspects of psychosis, induces a pronounced state of functional disconnection and prevents the formation of stable large-scale intrinsic brain states. MePhys offers a complementary window into brain function with unique advantages and limitations.

Study at a glance

Abstract

The primate brain is a densely interconnected organ whose function is best understood by recording from the entire structure in parallel, rather than parts of it in sequence. However, available methods either have limited temporal resolution (functional magnetic resonance imaging), limited spatial resolution (macroscopic electroencephalography), or a limited field of view (microscopic electrophysiology). To address this need, we developed a volumetric, mesoscopic recording approach ( MePhys ) by tessellating the volume of a monkey hemisphere with 992 electrode contacts that were distributed across 62 chronically implanted multi-electrode shafts. We showcase the scientific promise of MePhys by describing the functional interactions of local field potentials between the more than 300,000 simultaneously recorded pairs of electrodes. We find that a subanesthetic dose of ketamine -believed to mimic certain aspects of psychosis- can create a pronounced state of functional disconnection and prevent the formation of stable large-scale intrinsic states. We conclude that MePhys provides a new and fundamentally distinct window into brain function whose unique profile of strengths and weaknesses complements existing approaches in synergistic ways.