The propagation of the activity of the hippocampus, crucial for memory consolidation and other deliberative functions of the brain

A study published in the journal Current Biology this March has revealed a mechanism for the propagation of the effects of a specific activity of the hippocampus in the brain in resting state. A crucial process for memory consolidation and the establishment of many of the deliberative processes that take place when the brain is not paying attention or is not dedicated to performing a specific task.

A study coordinated by Gustavo Deco, ICREA research professor and director of the Center for Brain and Cognition (CBC) of the Department of Information and Communication Technologies (DTIC) at Pompeu Fabra University, with Raphael Kaplan, a member of his team and first author of the study, with the participation of a group of international scientists from research centres in Germany, Belgium, the United Kingdom and Switzerland.

The default mode network or DMN is a neural network in which different anatomical locations of the brain are involved: temporal, prefrontal and parietal regions, all of them related to episodic memory, and whose activity is highly correlated with one another and different from other brain neural networks. This network is activated, preferably, when the subject is not involved in any specific task, that is to say, in states of brain rest, in wakefulness, in deliberative processes, when thinking about others, oneself, in the past or when planning the future.

On the other hand, in the hippocampus are there patterns of specific oscillatory networks in this region of the brain and this activity has been associated with memory consolidation. It has been seen in a mouse model and in humans that after a period of learning the electrical stimulation of the hippocampus interferes with memory consolidation.

The authors of the study published in Current Biology, using electrophysiological techniques applied to the brains of anaesthetised primates, have confirmed a noticeable increase in the activity of the DMN neuronal network after oscillations of the networks of the hippocampus, an increase that is not seen in other types of activity in this region. In particular, the authors have found this increase when the DMN neural network is in action and just after oscillatory activity, and not in other states of rest.

According to Gustavo Deco, coordinator of this research, “our results suggest that the activity of local specific neural oscillatory networks of the hippocampus propagate through the DMN neural networks”, “this finding is the first step to understanding how the local activity of the hippocampus spreads on a large scale through the dynamics of states of brain rest”, added Deco, which is involved in the consolidation of past experiences and the planning of future behaviour.

Reference work:

Raphael Kaplan, Mohit H. Adnikari, Rikkert Hindriks, Dante Mantini, Yusuke Murayama, Nikos K. Logothetis, Gustavo Deco (2016), “Hippocampal Sharp-Wave Ripples Influence. Selective Activation of the Default Mode Network”, Current Biology, 26, 686-691, 7 Marchtp://dx.doi.org/10.1016/j.cub.2016.01.017.