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Isn’t it extraordinary that we can record and retrieve memories of our lives all the time? The ability to make new memories and retrieve old ones is often associated with rhythmic electrical activity in a structure of the brain called hippocampus, as damage to this structure results in an impairment of memory. Abhilasha Joshi and her colleagues have discovered a novel population of nerve cells outside the hippocampus that regulate the rhythmic firing of specialised nerve cells within the hippocampus.

How communities of nerve cells in different brain regions facilitate the rhythmic activity of nerve cells in the hippocampus is still a major challenge in neuroscience. In order to understand this phenomenon, Abhilasha Joshi and her colleagues studied the different kinds of nerve cells in a brain region (the septum) that sends inhibitory input to the hippocampus. They have discovered a novel population of rhythmic inhibitory neurons, and named them Teevra (Sanskrit) cells based on the sound of their firing (see figures).

They show that Teevra cells coordinate cortical information flow through synchronisation of nerve cell activity by targeting a small area of the hippocampus and by selecting a few key neurons, which in turn influence large neuronal assemblies encoding memories. Such studies help us to understand the precise temporal structure of neuronal activity and help us understand the organisational principles underlying temporal windows for memory.

Left: Teevra cell innervates a specialised population of nerve cells in the hippocampus predominantly in the CA3 region.

Right: Artwork by Anuja Gopidas depicts the Teevra cell (blue, axon red) in the midst of a Mandala, a South-Asian symbolism used here to represent the complexity of signatures of the distinct features that define neuronal types in the brain. The lines and curves reveal musical notes reminding us of the songs of neurons as they communicate through electrical signals and the word 'Teevra' written in major scripts of the world expressing the sharing of scientific knowledge and co-operation of scientists. Below the Mandala is the electrical recording of brain waves (theta oscillation, yellow) as the mouse explores the world and the rhythmic electrical signals (blue) sent by the Teevra cell as it participates in the representation of information.

Transliteration by Rimjhim Dobhal

  • Behavior-Dependent Activity and Synaptic Organization of Septo-hippocampal GABAergic Neurons Selectively Targeting the Hippocampal CA3 Area. Abhilasha Joshi, Minas Salib, Tim James Viney, David Dupret, Peter Somogyi. Neuron 2017, 96:1342-1357.e5.