How does the brain perceive motion? PD Dr. Dirk Jancke explores this question by means of a special optical method. He reviews recent findings with voltage-sensitive dyes in a special section of the journal Neurophotonics that honors Prof. Amiram Grinvald, one of the most influencing researchers in this field.
Boosting the voltage
Dirk Jancke has given the phrase "a light-bulb moment" a whole new meaning. In his laboratory he turns the activity of brain cells into light, using fluorescent dyes with a particular attribute: They change their spectral properties in response to voltage changes. That means, if a brain cell is activated, the voltage over the cell membrane increases and the dye starts to fluoresce more. This imaging technique is called "voltage-sensitive dye imaging" or in short VSDI. It is a groundbreaking technique that led to many new findings in neuroscience. "Voltage-sensitive indicators are providing us with the best spatiotemporal resolution we can currently achieve in our experiments. That means, with VSDI we can observe widespread activity across the brain's surface in milliseconds and across several square millimeters.", explains Jancke.
Research on optical illusions
Jancke learned how to use VSDI during his time as a postdoc in the laboratory of Prof. Amiram Grinvald at the Weizmann Institute of Science in Israel. "He is one of the pioneers in research on voltage-sensitive dyes. As a postdoc in his laboratory I benefited greatly from his expertise.", says Jancke. During that period he was able to observe how a wave of activity spreads over the visual cortex, when the brain processes visual motion. Instead of a real, physical motion, Jancke used an optical illusion that created the impression of movement. Building up his own Optical Imaging Lab at Ruhr-University Bochum he continued his research on visual brain processing and extended his previous findings.
Recent experiments performed in his laboratory with VSDI showed for example, that the brain processes a quick counterchange of luminance at two neighboring locations as a signal of motion. The cause may be that neuronal information, indicating a change from bright to dark is processed faster than a change from dark tobright. This phenomenon creates an asymmetric and rapid spread, which can be visualized through VSDI as a wave of activity across the brain. Such mechanism might be useful for the sensitive detection of body motion against "noisy" backgrounds, especially in case of camouflage. Jancke is looking forward to find out which mechanisms in the brain he will be able to observe next with VSDI. He is certain, that in the future optical techniques will help to gain many more insights into the way the brain functions.
Parts of the research were financially supported by the Collaborative Research Centre 874 at the Ruhr University Bochum, funded by the Deutsche Forschungsgemeinschaft. Since 2010 the interdisciplinary research consortium investigates how memory develops and how sensory input is processed within the brain.
D. Jancke (2017): Catching the voltage gradient—asymmetric boost of cortical spread generates motion signals across visual cortex: a brief review with special thanks to Amiram Grinvald. Neurophotonics, DOI: 10.1117/1.NPh.4.3.031206.
Link to the publication:
PD Dr. Dirk Jancke
Optical Imaging Lab
Institute for Neural Computation
Ruhr Universität Bochum
Tel: 0234 32 27845
Text: Judith Merkelt