Mental challenges, a game of balance

What happens in our brain when we think, remember, or focus on a task? These are among the fundamental questions that neuroscience seeks to answer. Up to now, research aimed at understanding individual behavior has tended to focus separately on metabolic activity within specific brain regions and on that of the entire brain network.
A key goal of researchers is to integrate this information with non-invasive methods, to understand the physiological functioning of the healthy human brain. Such approaches may also help develop new tools to better understand brain disorders. A step in this direction was taken by a research group from the Center for Mind/Brain Sciences (CIMeC) of the University of Trento.

The results of the research have been published in the journal Pnas, underscoring its relevance and impact within the scientific community. The study has two co-first authors: Francesca Saviola, who carried out the work during her doctorate in Cognitive and Brain Sciences at Cimec under the supervision of Jorge Jovicich (professor of Neuropsychology and Cognitive Neurosciences at the Center), and Stefano Tambalo, head technician of the Magnetic Resonance and Neuroimaging Laboratory at Cimec. Saviola is currently a scientist at the École Polytechnique Fédérale de Lausanne (EPFL). During her PhD, she undertook a research visit at EPFL in the Laboratory of Medical Image Processing and Analysis (MIP:Lab) of Prof. Dimitri Van De Ville, supported by the ISMRM Research Exchange Program. This visit established a collaboration that was instrumental in developing the methodology applied in this study.

About the study. Imagine that you are in the traffic driving an automatic car. There are two pedals: the accelerator and the brake. A proper balance between accelerating and braking is essential to reach your destination safely and avoid accidents. This is similar to what happens in the human brain when it is engaged in a cognitive activity. On one hand, neuronal excitability, i.e. the ability of a neuron to react to stimuli by generating nerve impulses, acts like the accelerator. On the other, the inhibition of neuronal activity functions as the brake, reducing or blocking this function when necessary. The balanced interplay between excitation and inhibition is fundamental for communicating, processing signals, and responding to stimuli.
The research group explored how this delicate balance changes when the brain faces increasingly complex mental tasks.
A key innovation of the study is that its authors were able to monitor, in real time and in a non-invasively, how the balance between excitation and inhibition in neurons shifts during cognitive tasks, alongside the dynamics of brain networks.

The results of the study. The study reveals how the brain alternates between states of strong stability and transient states in which connections are reorganized, a mechanism that is mediated by both chemical and vascular factors supporting complex cognitive processes.
Real-time monitoring of metabolism and brain activity showed that the brain's chemical signals and communication networks operate in synchrony within seconds, like a finely tuned orchestra keeping time. When cognitive demands increase, this balance can be disrupted, pushing the brain into a more stable but less flexible state.
The study combined spectroscopy with the functional mapping of the brain networks and was conducted using magnetic resonance neuroimaging, a technique that allows researchers to study both the structure and function of the brain by measuring dynamic changes in physiological and neural processes. While this approach can be used for basic research, it holds potential for use in more complex clinical contexts.
"We found that changes in brain metabolism and blood oxygenation level rise and fall in synchrony. This points to a shared regulatory mechanism that enables the brain to remain flexible and responsive to external stimuli", explain Francesca Saviola and Stefano Tambalo.
Understanding the temporal dimension through which metabolism and vascular response interact to drive on-demand reconfiguration of brain networks and information processing is essential to better understand and reframe cognitive disorders in terms of disrupted synchronicity or impaired coupling of neural signals.
"Our work – underlines Jorge Jovicich – opens new perspectives on how the brain helps us to stay focused, adaptable and resilient during a cognitive task. This knowledge may one day inspire novel approaches to the treatment of neurological and psychiatric disorders".