New Science Paper Published: MacAskill Lab, NPP

A new paper published in Science from the MacAskill lab in NPP, led by graduate student Karyna Mishchanchuk, shows that a part of the brain called the hippocampus is really important for a key strategy we use to make decisions called ‘hidden state inference’. 

But what is hidden state inference? Imagine you’re texting with a friend.  Because you can’t see them in person, you can’t directly tell if they’re happy, sad, or stressed. This is because their emotional state is hidden - you can’t observe happiness or sadness directly through text messages. However, what we often do is notice things like how quickly they respond, whether their messages are short or detailed, if they’re using lots of emojis, or if they say something like "I'm tired."
 
We then use these clues to make an educated guess about how our friend is feeling. For example, if they reply with quick, one-word answers and don’t use their usual emojis, we will often infer they’re feeling down or distracted. If they’re texting with lots of emojis and longer messages, you might infer they’re in a good mood.
 
This is what we mean by hidden state inference - our attempt to understand our friend’s unseen emotional state based on the subtle cues in their messages.

In this paper, Karyna found that the hippocampus is key for this process - mice without a functioning hippocampus couldn’t use hidden state inference anymore. She also found that the way the hippocampus supports hidden state inference is similar to how it supports spatial navigation and memory – which means we can use decades of beautiful work studying spatial navigation (inc. Nobel prize work from John O’Keefe’s lab at UCL!) to help us better understand this process

The reason we are really excited about this is that we have known for a long time that patients with mental health disorders such as schizophrenia or depression often have trouble with problems that require hidden state inference, and also have alterations in the functioning of their hippocampus. Up until now we didn’t really know how these were connected – but our paper shows that you need the proper functioning of hippocampus for solving these problems! 

We think that our study might provide a basis on which we can investigate how these changes in hippocampus function might lead to the increased risk of mental health disorders. Our goal now is to use these findings to investigate how these changes in hippocampal function might lead to the increased risk of mental illness, and how we might go about designing new treatments to help reverse these increased risk in the future.

Hidden state interence paper

Overview: the paper shows that hippocampal neurons represent the different hidden states required to perform hidden state inference.