MRI stereoscope: a miniature stereoscope for human neuroimaging.
Ip IB., Alvarez I., Tacon M., Parker AJ., Bridge H.
Stereoscopic vision enables the perception of depth. To study the brain mechanisms behind stereoscopic vision using non-invasive brain imaging ('MRI'), scientists need to reproduce the independent views of the left and right eyes in the brain scanner using 'dichoptic' displays. However, high quality dichoptic displays are technically challenging and costly to implement in the MRI scanner. The novel miniature stereoscope system ('MRI stereoscope') is an affordable and open-source tool that displays high-quality dichoptic images inside the MRI scanner. The MRI stereoscope takes advantage of commonly used display equipment, the MRI head coil, and a display screen. To validate the MRI stereoscope, binocular disparity stimuli were presented in a 3T MRI scanner while neural activation was recorded using functional MRI in six human participants. The comparison of large binocular disparities compared to disparities close to zero evoked strong responses across dorsal and ventral extra-striate visual cortex. In contrast, binocularly anti-correlated stimuli, which are not perceived in depth, did not evoke comparable activation. These results are the proof-of-concept that the MRI stereoscope can deliver dichoptic images that produce the perception of stereoscopic depth during acquisition of MR responses. Application of the MRI stereoscope to neuroscience can help to address important questions in perception and consciousness.Significance StatementIndependent stimulation of the left and right eye is a prerequisite to studying perception and consciousness through the binocular visual system. Yet, such 'dichoptic' displays are not widely used in neuroimaging due to the technical challenges of delivering high-quality dichoptic displays in the MRI scanner. We present a demonstration of a novel, miniature MRI stereoscope, produced in a mechanical workshop using commonly available materials that overcomes these challenges. Our device can accelerate research into the biological basis of binocular vision by providing a low-cost, high quality device to display dichoptic images for neuroscientific research.