Mesoscopic calcium imaging in head-unrestrained non-human primates using a lensless microscope

Abstract Mesoscopic calcium imaging enables studies of cell-type specific neural activity over large sections of the cortex and over multiple cortical areas. A growing body of literature from multiple animal models suggests that this neural activity can be different when animals are free to move their bodies compared to when they are restrained. Unfortunately, existing systems for imaging calcium dynamics over large areas of the brain in non-human primates (NHPs) are large table-top devices that require researchers to restrain the animal’s head so that it remains under the lens of the microscope. Here, we demonstrate the first fluorescent imaging device, which is capable of imaging mesoscale calcium activity in non-human primates that are free to move their heads. We successfully miniaturized our system by replacing lenses with an optical phase mask and computational algorithms that reconstruct images from complex sensor data. The resulting lensless microscope can fit comfortably on top of the heads of the NHPs, allowing the animals to move their heads freely while imaging. We demonstrate over 20 mm 2 field of view in the primary visual cortex of rhesus macaques. With this approach we measured the first orientation columns maps from a head-unrestrained macaque. Our work establishes functional mesoscopic imaging using a head-mounted lensless microscope as a powerful approach for studying neural activity in head-unrestrained NHPs. These experiments can help reveal the relationship between neural activity and behavior under more naturalistic conditions.