Research has shown how our brain combines internal and external information to create a complete view of the world.

There is a gate for sensory information - a specific cluster of neural circuits - which combines information from the external world (sensory stimulation) with information on our internal state such as hunger, fear or stress.

This region, called the ‘habenula’, is responsible for sending certain bits of sensory information down the line of neural processing, to be run against our set of memories and emotions.

Working with a European academic research initiative called NERF, expert Emre Yaksi has used both neurobiology and nano-scale engineering to study brain function at multiple levels.

Yaksi says the habenula appears to help regulate one element of the huge amount of processing our brains perform.

“Our brain has high levels of spontaneous activity, even in the absence of sensory stimulation. We think that this spontaneous neural activity in combination with sensory stimulation results in a particular internal state of the habenula,” Dr Yaksi said.

“By this functional organization the habenula acts as a kind of switch board, selecting certain sensory information and sending it to the downstream brainstem areas. Thus, the habenula regulates our behaviour.”

“It will be interesting to test whether experience or learning can alter the functional organization of these circuits,” he said.

The investigations into the role of habenula were undertaken with a zebrafish brain as a stand-in for human.

Zebrafish has become a common model organism for neurological research.

To find out how brains combine external and internal stimuli, researchers Suresh Kumar Jetti, Nuria Vendrell Llopis and Emre Yaksi focused on the dorsal habenula (dHb) in zebrafish. The dHb is an equivalent of the habenula in mammals and relays information from the sensory areas to the brain region that regulates animal behaviour under stress conditions.

Researchers say that in the case of the zebrafish, the dHb receives input from cells of the olfactory bulb, thus odours can trigger distinct behaviours (e.g. feeding, courtship, alarm).

The ongoing spontaneous activity in neurons was thought to be associated with several neurological phenomena, such as sleep, or the learning and sensory process.

The researchers observed that dHb is highly active even in the absence of any sensory stimulation. They also showed that the spontaneous activity of dHb is not random but highly structured in the spatial clusters of neurons.