Sustained concentration (also known as vigilance) produces a different type of memory than a momentary startle, and these differences are linked to different signaling molecules in mice brains. Researchers used optogenetics neuroscience to help visualize these dynamics in the living mouse brain, observing fast and slow molecular pathways that support memory function. These processes occur in brain cells known as astrocytes, revealing yet another important way these cells assist neurons.
Norepinephrine, or noradrenaline, is a neurotransmitter and a hormone that prepares the body for action. Previous research has shown that norepinephrine release is necessary to modify synapses, the connections between neurons that form and consolidate memories. Astrocytes are important mediators of these changes, and the researchers wanted to see what happens in these cells when mice learn in real-time.
The researchers used optogenetics neuroscience to stimulate brain cells with light to induce norepinephrine release. They concentrated on noradrenergic neurons originating in the locus coeruleus, a brain region. The release of norepinephrine triggered two distinct molecular events, the first involving calcium activity and the second cAMP, an important signaling molecule. Calcium levels in astrocytes increased quickly after norepinephrine was released, whereas cAMP levels increased slowly but steadily. These fast and slow dynamics are important because calcium increases synaptic plasticity, or the ability of cells to form new memory connections, whereas cAMP increases energy metabolism for memory consolidation.