Our eyes are constantly making saccades, or little jumps. Yet the world appears to us as a smooth whole. Somehow, the brain's visual system "knows" where the eyes are about to move and is able to adjust for that movement. In a paper published online this week in Nature, researchers at the University of Pittsburgh and the National Eye Institute (NEI) for the first time provide a circuit-level explanation as to why.
"This is a classic problem in neuroscience," says Marc Sommer, assistant professor of neuroscience at Pitt, who coauthored the paper with Robert Wurtz, senior investigator at NEI, one of the National Institutes of Health. "People have been searching for a circuit to accomplish this stability for the last 50 years, and we think we've made good progress with this study."
In 1950, Nobel laureate Roger Sperry hypothesized that when the brain commands the eyes to move, it also sends a corollary discharge, or internal copy, of that command to the visual system. Sommer and Wurtz showed in a 2002 Science paper that a pathway from brainstem to frontal cortex conveys a corollary discharge signal in the brains of monkeys. They suggested that this pathway might cause visual neurons of the cortex to suddenly shift their receptive field--their window on the world--just before a saccade. Such neurons with shifting receptive fields had been discovered by Pitt Professor of Neuroscience Carol Colby and colleagues in 1992.
In their current paper, which will be published in the Nov. 16 print edition of Nature, Sommer and Wurtz completed the circuit. They showed that the receptive fields in cortex are shifted because of the corollary discharge from the brainstem. To do this, they exploited the fact that the signals are relayed via the thalamus, a crucial intermediary. By knocking out the relay neurons, they interrupted the pathway. They found that receptive field shifts were curtailed by more than half.
A similar circuit is likely to exist in human brains, the researchers say. With this study, Sommer and Wurtz also provide a framework for studying corollary discharge in other sensory systems, such as hearing: Even when you move your head around, you still hear sounds around you as coming from the same place.
In future studies, Sommer and his graduate students at Pitt will perform the first direct test of the visual stability hypothesis. To determine whether shifting receptive fields are responsible for visual stability, the shifts will be disrupted in monkeys trained to detect visual motion. The monkeys could then report whether their world appears to be moving around abnormally as eye movements are made.
Karen Hoffmann | EurekAlert!
Antarctic Ice Sheet mass loss has increased
14.06.2018 | Technische Universität Dresden
WAKE-UP provides new treatment option for stroke patients | International study led by UKE
17.05.2018 | Universitätsklinikum Hamburg-Eppendorf
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
20.06.2018 | Materials Sciences
20.06.2018 | Information Technology
20.06.2018 | Information Technology