Perhaps one of the hardest things to understand about the brain is the way that it is organized into networks. In this post, I will discuss a 2015 study, on the brain structures involved in delayed gratification, that makes this complex subject a bit easier to grasp.
Against this background, it is interesting to consider a study published in July 2015 by Andrew R. Abela and his colleagues, entitled "Hippocampal interplay with nucleus accumbens is critical for decisions about time". Abela is talking about the interplay between two brain structures that have usually been regarded as having very different overall functions: in the case of the hippocampus, memory and planning (you retrieve memories to plan your future actions more effectively), and in the case of the nucleus accumbens, pleasure.
What makes this study so interesting is that it shows how an elaborate behaviour that enables an animal to delay gratification requires a dialogue between two brain structures, each of which is involved in a particular aspect of that behaviour: the nucleus accumbens in the experience of pleasure, the hippocampus in planning a delay before enjoying that experience. It is therefore the connections joining these two distinct brain structures that enable the emergence of the behaviour, further demonstrating the importance of a networked conception of the brain. This particular experiment examined the brains of rats, but showed that even in these animals, the brain is already employing a sort of neuronal recycling to accomplish a new, more complex task.
This concept of neuronal recycling also helps us to better understand how various parts of the brain that evolved in response to certain evolutionary pressures long, long ago can be reused now for other purposes, in particular in the human brain, which is now evolving in an entirely different environment. One good example of how productive this approach can be is the development of the hypothesis of a common evolutionary origin for spatial orientation and declarative memory in humans (which again, as it happens, involves the hippocampus).