Neuroscientists have found an apathy switch in the brain

(ORDO NEWS) — Scientists from the United States and Canada have discovered a new function of a tiny little-studied region in the very center of the brain – habenula.

It acts as a switch that determines the periods when the body is ready to work in search of reward, and when it should stop and rest.

The study may be useful in developing methods to combat apathy, anxiety and depressive disorders.

Habenula is a tiny region of the thalamic region of the brain involved in processing pain signals from sensory neurons, regulating sleep and wake cycles, and shaping mood. However, its exact role in these processes is still not fully understood.

In a new study, a group of scientists from Cornell (USA) and Montreal (Canada) universities decided to analyze in more detail the role of the lateral part of the habenula in the development of anxiety and depressive conditions, identified in previous studies.

To do this, they used laboratory mice, whose brains were injected with viral vectors in such a way that neurons in the studied part of the brain fluoresced brightly when excited, but stopped doing so when inactive.

The signal from neurons was recorded along a fiber optic thread passing through the skull and part of the brain directly to the lateral habenula.

During the experiments, mice were placed in a special sound-absorbing box with a hole on one side and a drinking bowl with water on the other.

When a light was turned on near the hole, the mouse responded to this conditioned signal and stuck its nose into the hole, for which it was rewarded with a few drops of water (with a certain probability depending on the test being performed).

Neuroscientists have found an apathy switch in the brain 2
Scheme of viral vector injection and optical fiber placement (A). Fluorescent dye expression in lateral habenula neurons (B)

So, in one version of the experiment, when mice with a probability of 80% received water for a successfully completed task, neurons in the lateral habenula were excited as soon as the animals got drunk and stopped “working”.

The authors achieved a similar result by completely turning off the drinker. After several unsuccessful attempts to get a reward, the rodents abandoned the task, and the desired neurons immediately began to fluoresce.

In addition, the scientists noticed that if the neurons of the lateral habenula were specifically blocked, the mice would make significantly more attempts to complete the task even without receiving a reward.

Thus, the authors of the study believe that the region of the brain they studied could be a suitable target for the treatment of disorders associated with apathy – the lack of desire for any activity.

This symptom is characteristic not only of mental disorders such as depression or schizophrenia, but also diseases such as Parkinson’s disease, in which patients experience a state of apathy, but without showing a depressed mood.

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