Since we claim to be neuroscientists, we thought we should allocate a few blog posts to the nitty gritty details of neuroscience research. To start things off, we have a post on Parvalbumin interneurons. They are a subset of interneurons that express parvalbumin, a calcium binding protein.
In 2013, Donato et al. reported that there are two different types of Parvalbumin neurons in our cortex and hippocampus. One type expresses low levels of Parvalbumin (PV), low levels of GAD67 (enzyme that makes GABA neurotransmitter) and receive higher inhibitory inputs- referred to here as Low PV plasticity cells; and the other expresses high levels of PV and GAD67 and receive higher excitatory input- referred to as High PV plasticity cells.
These two populations of PV cells play an important role in two distinct learning paradigms. Low PV plasticity cells seem to be important for gradual/incremental learning (such as Morris water maze task or Rotorod). Whereas, high PV plasticity cells seem to be important for definite learning (such as fear conditioning). The authors claim PV plasticity cells are important for memory consolidation in both types of learning.
In a recently published paper, the group puts forth a mechanism for the role of PV plasticity cells in memory consolidation. They claim dopamine signaling sustains PV plasticty and strengthens the memory.
Mice are subjected to definite learning tasks, or incremental learning tasks, which is followed by measuring the fraction of the two types of PV cells. High PV cells (green) are more abundant after a definite learning task. On the other hand, low PV cells (blue) are higher after an incremental learning task. The time point at which they are expressed seems to be important as well. When the expression of PV is inhibited by drugs, it affects the consolidation of memory. The team goes on to show dopamine signalling underlies this plasticity.
Two key findings here are- 1) the time slots within which dopamine signaling is vital (0-6 hrs and 10-16 hours after the learning stimulus) and 2) dopamine signaling can strengthen the memory consolidation.
- Karunakaran S, Chowdhury A, Donato F, Quairiaux C, Michel CM, Caroni P. PV plasticity sustained through D1/5 dopamine signaling required for long-term memory consolidation. Nat Neurosci. 2016 Mar;19(3):454-64. doi: 10.1038/nn.4231.
- Donato F, Rompani SB, Caroni P. Parvalbumin-expressing basket-cell network plasticity induced by experience regulates adult learning. Nature. 2013 Dec 12;504(7479):272-6. doi: 10.1038/nature12866.