Summary: Researchers implicate the inferior frontal junction area in controlling behavior and executive function.
Source: Max Planck Institute
For our social life and our profession we must be able to deal with our environment and other people. Executive functions, meaning the basic intellectual abilities that control human thought and action, help us to do this. These include selective attention, otherwise known as the ability to concentrate on one stimulus and suppress others, or the working memory, with which we can retain and manipulate information. These functions also enable us to plan actions and to divide them into individual steps.
However, some people do not succeed, finding it difficult to focus, plan their actions in a goal-oriented manner, and they have poor control over their impulses and emotions. They suffer from a condition called dysexecutive syndrome, which is often caused by craniocerebral trauma or a stroke.
One of those affected is a 56-year-old patient from Leipzig. She had suffered several strokes that hit a strategically very important region of the brain: The so-called inferior frontal junction area (IFJ) in the frontal lobe of the cerebral cortex in both hemispheres. The injury meant she was no longer able to pass basic psychological tests. These include, for example, the planning task zoo visit, in which a person is required to plan a tour of a zoo in accordance with various guidelines, or the Stroop test, which measures how well someone can suppress disturbing, unimportant stimuli in order to concentrate on an actual task.
The special feature of the examined patient: The lesion was limited to the IFJ alone, in both hemispheres of the brain equally (see figure). Normally, a stroke injures larger areas of the brain or is not restricted to such a defined area. In addition, it rarely affects the homologous areas in both hemispheres of the brain at the same time. As difficult as the situation is for the patient, it offers a unique opportunity for science to investigate the role of this region for executive functions.
“From functional MRI examinations on healthy persons, it was already known that the IFJ is increasingly activated when selective attention, working memory and the other executive functions are required. However, the final proof that these executive abilities are located there has not yet been provided,” explains Matthias Schroeter, first author of the underlying study and head of the research group “Cognitive Neuropsychiatry” at MPI CBS. However, causal evidence of such functional-anatomical relationships can only be obtained when the areas are actually switched off–and thus the abilities actually located there fail. “We were able to provide this proof with the help of this patient.”
And not only that; in addition to the classic approach — assigning individual functions to a specific brain region on the basis of brain damage and the corresponding impairments — the researchers also took the opposite approach: the “big data” approach via databases. These portals contain information from tens of thousands of participants from many psychological tests and the brain areas activated in the process. With their help, the researchers were able to predict the patient’s impairments solely on the basis of the brain damage determined by brain scans. Experts refer to this as symptom reading, a method which could be used in the future to adapt a therapy to individual patients and their brain damage without having to test it in detail.
“If patients suffer from a loss of executive functions after an accident or stroke, for example, they are usually less able to regenerate the other affected abilities because they find it difficult to plan for them,” said Schroeter. “In future, when the lesion images and databases provide us with more detailed information on which regions, and hence abilities, have failed, we will be able to adapt the therapy even more specifically.
About this neuroscience research article
Source: Max Planck Institute Media Contacts: Verena Müller – Max Planck Institute Image Source: The image is in the public domain.
From correlational approaches to meta-analytical symptom reading in individual patients: Bilateral lesions in the inferior frontal junction specifically cause dysexecutive syndrome
Background Executive functions describe a wide variety of higher order cognitive processes allowing the modification of thought and behavior in response to changing contexts. Recent comprehensive quantitative and systematic meta-analyses on functional imaging studies in healthy subjects identified the inferior frontal junction (IFJ), located at the junction of the inferior frontal sulcus and the inferior precentral sulcus, as essential for executive functions. Lesion studies in patients are necessary for confirmation of this finding. Case presentation We present, as a proof of concept, a 56 year old woman with bilateral ischemic lesions in the IFJ caused by multiple stroke-related brain infarcts in the bilateral territory of the middle cerebral artery. Comprehensive neuropsychological testing revealed specific deficits in executive functions, namely working memory, task switching, inhibitory control, interference resolution, fluency, and complex executive function tests focusing on action planning and problem solving abilities. Memory functions were within the normal range. Furthermore, we applied comprehensive meta-analyses to validate the importance of the IFJ for executive functions. (i) Lesions in the patient’s brain in the IFJ coincide with regional activation in functional imaging studies for working memory, task switching, and the Stroop task. (ii) Lesions in the patient’s IFJ should affect a frontoparietal network as shown with connectivity analyses. (iii) We introduce a new analysis tool – Meta-Analytical Reading of Symptoms (MARS) – that enables prediction of clinical symptoms from imaging data in individual patients.
Conclusions Our study confirms the importance of the IFJ as the causal agent, in a frontoparietal network, for dysexecutive syndrome. As a lesion study, it goes beyond correlational imaging approaches. The new meta-analytical symptom reading approach can be applied in other patients and diseases. It has a high potential to foster individualized diagnosis and therapy in clinical settings in the framework of personalized medicine.