New advances in understanding schizophrenia

Schizophrenia is a chronic psychiatric disorder that affects approximately 1% of the population. It combines hallucinations, delusions and thought disorders with less visible but highly debilitating symptoms such as reduced motivation and cognitive difficulties. 
Two recent studies involving researchers from the GIN's "Brain, Behaviour and Neuromodulation" team at GIN, in collaboration with the LPNC (Grenoble) and CRNL (Lyon, PsyR² team) laboratories, shed new light on these clinical dimensions by discovering two underlying brain mechanisms: early sensory processing and effort allocation capacity.

"These studies are important because they provide a better understanding of certain key and highly complex mechanisms that cause the debilitating symptoms of schizophrenia" explains Professor Clément Dondé, psychiatrist and researcher at GIN, who led these studies. "Disruption in the early processing of environmental auditory stimuli contributes to cognitive disorders, while abnormalities in effort cost processing are involved in motivational disorders. These clinical manifestations are the main causes of disability in people with schizophrenia.’

When hearing impairs decision-making

In an initial study, researchers sought to understand why people with schizophrenia have difficulty distinguishing between two sounds, and to determine whether these difficulties stem from a sensory problem or a problem with decision-making based on this perception. 
Thirty subjects with schizophrenia and 30 control subjects performed an auditory discrimination task (tone matching). Beyond analysing simple performance (correct answers, reaction time), the researchers applied a computational drift-diffusion model (DDM) to break down the decision-making process. 
They observed that subjects with schizophrenia accumulate sensory information more slowly (reduced drift rate) and show an additional cost in non-decision times (perception or motor response). These observations suggest that auditory deficits result not only from poor sensory perception, but also from the way in which perceived sound is translated into behavioural response.

When effort is poorly adjusted

In the second study, 25 subjects with schizophrenia and 25 control subjects performed a dynamic effort task: for 30 seconds, they had to vary their physical effort (by pressing a lever) to earn money, depending on the difficulty imposed and the incentive (amount offered). The results show that subjects with schizophrenia are less able to adjust their effort to the incentive, spend less time above the required threshold and earn less than healthy subjects. 
This is not simply a lack of motivation, but rather a problem with adaptive effort decision-making. In other words, the ‘cost/benefit calculation’ of effort is impaired, which limits engagement in goal-directed behaviour. 

Better understanding for better treatment

"Now that these mechanisms are better characterised in terms of behaviour, the next step, which is already underway in the laboratory, is to carry out brain imaging and electroencephalogram tests to identify their cerebral bases, which could become therapeutic targets for non-invasive brain stimulation," explains Prof. Clément Dondé.  "These advances offer real hope for the development of more effective and targeted treatments for people affected by schizophrenia."
 

References : 
Characterizing early auditory deficits in schizophrenia using drift-diffusion modeling
Dondé C, Pereira M, Nalborczyk L, Roux P, Faivre N, Brunelin J. Schizophr Res. 2025 Jul 29;284:23-31. doi: 10.1016/j.schres.2025.07.024. Online ahead of print. PMID: 40737765

Impaired effort allocation in schizophrenia. 
Blouzard E, Cignetti F, Meyniel F, Pouchon A, Polosan M, Bastin J, Dondé C. 
Schizophr Res Cogn. 2025 Jul 15;42:100378. doi: 10.1016/j.scog.2025.100378. eCollection 2025 Dec. PMID: 40697646 Free PMC article.