Cracking the Space-Time Code of Your Neural Self

…..researchers addressed the question of how an untrained brain can generate well-ordered sequences of activity. They found this requires two conditions to be met: First, a small portion of the neurons’ projected output – their connections to downstream neurons – have to prefer a specific direction. Second, neighboring neurons need to share that preferred direction. “That means that the connections of nerve cells depend on directional preferences and are spatially linked to each other. This is the key to the generation of sequential activity in neuronal networks,” explains Sebastian Spreizer. If the network is wired according to these rules, it creates a type of activity landscape similar to geographic hills and valleys. In the context of this metaphor, the sequences of neuronal activity are like the rivers in a landscape. Small changes in the spatial fabric of the nerve cells generate certain temporal and spatial sequences of neuronal activity.

To verify the model, the shapes and connections to neighboring neurons must be measured. “Interestingly, neuromodulators – chemical substances such as dopamine, for example – can produce the connectivity in the brain required above, and in a dynamic way that is dependent on context,” says Ad Aertsen. That gives the network the opportunity to generate different sequences of neuronal activity. Yet, not all of these will be functionally relevant. As a result, the researchers in Freiburg and Stockholm have concluded that learning mechanisms can be developed in order to select for rewarding sequences, thereby making meaningful behavior possible.