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Why do some memories last a lifetime while others fade away?

Leonardo Bonetti stood in front of an MRI machine © Simon Fischel

A groundbreaking new study sheds light on this mystery by uncovering hidden patterns of brain activity that support long-term memory. Using a framework inspired by thermodynamics, scientists have developed a novel approach to understanding how different brain regions work together to shape cognition. 

The second law of thermodynamics tell us that all complex living systems operate far from equilibrium, leading to the emergence of the ‘arrow of time’. This results in their dynamic activity being time-irreversible. The human brain is no exception, and is an example of a superbly complex system with many interactions between a wide array of specialised brain areas. Inferring which brain regions are engaging in a significant interaction that is facilitating cognition remains an important challenge in neuroscience. Inspired by the study of thermodynamics, the time-irreversibility of neural activity can be used to identify key groups of regions whose interactions underlie cognition at a number of scales.

In a study published in the journal PNAS, the ‘DiMViGI’ framework was presented for measuring the irreversibility of neural recordings across different levels of interaction. Human participants engaged in a long-term memory task that tested their ability to identify variations of a short musical piece. When they were able to correctly identify the piece, their brain dynamics, recorded with magnetoencephalography, were analysed using a graph-theoretic method, that quantified the irreversibility of regional interactions. The striking results show that the thermodynamics-inspired method was able to differentiate between significant and insignificant interactions between groups of brain regions.

 

Read the full story on the Department of Psychiatry website.