Updated November 29th, 2022
Research Spotlight
Extrahippocampal Seizure and Memory Circuits Overlap
"The last thing I remember...” is how patients often describe their seizures, where they cannot remember events preceding the seizure. Naik and colleagues used modern brain mapping techniques to visualize neurons activated during the storage of a spatial memory task and a seizure. The authors probed key structures such as the medial prefrontal cortex, retrosplenial cortex, dentate gyrus, and mediodorsal thalamus and found the overlap between learning- and seizure-activated neurons. As seizures spread, they go along the memory circuits, which may explain why they erase specific memories.
Multiscale Computer Modeling of Spreading Depolarization in Brain Slices
Spreading depolarization (SD) is a slow-moving wave of electrical and ionic imbalances in brain tissue and is a hallmark of several neurological disorders. Kelley and colleagues developed a multiscale computer model of brain slices with realistic neuronal densities, ions, and oxygenation. This model shows that SD is exacerbated by and causes hypoxia, resulting in strong SD dependence on slice thickness. This model also predicts that the velocity of SD propagation is not dependent on its initiation, but instead on tissue properties, including the amount of extracellular space and the total area of neuronal membrane, suggesting faster SD following ischemic stroke or traumatic brain injury.
Discounting of future rewards and punishments in rats
Humans and animals often have to choose between future rewards and punishments. They typically favor sooner over later rewards. However, it is less clear if they like to defer unpleasant events into the future since future pain would be less bad than the same pain today, or if they, by contrast, accelerate future unpleasant events to get it over with. To decide between these possibilities, rats made choices between different combinations of sooner or later mild electric shocks and sooner or later food rewards. Zech, Schäble, and Kalenscher found that rats neither reliably preferred sooner over later shocks, nor later over sooner shocks. Instead, their choices were consistent with a novel hypothesis that shocks have negative, time-dependent spill-over effects on the value of subsequent rewards. In line with this idea, the authors found that, depending on how close in time a shock occurred before a reward, rats could be brought to prefer later over sooner rewards, akin to an increase in self-control.
A blue light-sensitive protein expressed throughout the brain influences mouse behavior. Upton and colleagues have identified a role for the non-visual opsin, encephalopsin (Opn3), in modulating the startle reflex using mouse genetic models. These findings demonstrate that not only do the opsin family of G protein-coupled receptors regulate homeostatic functions of the brain, but they play a key role in regulating behavior as well.