Using two newly developed types of reasoning tests, a team of researchers at UCL and UCLH has identified key brain regions that are essential for logical thinking and problem-solving. The results will help to increase our understanding of how the human brain supports reasoning skills that enable us to comprehend, draw conclusions, and deal with new and novel problems. Findings from the study, which involved patients with unilateral focal frontal or posterior lesions, and healthy controls, could also have significant clinical applications, the researchers suggested, as the two new tests can help identify cognitive impairments that would otherwise go undetected.
“Our findings show a close connection between the right frontal brain network involved in reasoning and the right frontal brain network essential for fluid intelligence (our ability to solve problems without prior experience),” said Lisa Cipolotti, FMedSci, a professor at UCL Queen Square Institute of Neurology and Department of Neuropsychology, UCLH, and senior author of the team’s published paper in Brain. “This suggests that a common area of the brain plays a critical role in both reasoning and fluid intelligence.”
Cipolotti and colleagues reported on their work in a paper titled, “A right frontal network for analogical and deductive reasoning.” The paper’s lead and corresponding author is Joseph Mole, PhD, DClinPsy, CPsychol, at UCL Queen Square Institute of Neurology and Department of Neuropsychology, UCLH.
“Reasoning skills are central to many of humanity’s greatest intellectual endeavors: mathematics, philosophy, and science, to name but a few,” the authors wrote. “Two of the most well-studied types of reasoning are analogical reasoning (AR) and deductive reasoning (DR).” However, they pointed out, our understanding of the relationship between reasoning abilities and their neuroanatomical basis remains “surprisingly limited.”
Analogical reasoning is the process of identifying similarities between relationships and is held to underpin our ability to solve problems by transferring information from one set of relationships to another. Deductive reasoning, in contrast, is the ability to derive a logical conclusion from a set of premises that are held to be true. This form of reasoning is thought to be critical for solving problems with determinate solutions, as well as identifying when solutions cannot be determined.
To determine which brain areas are necessary for a certain ability, researchers study patients with brain lesions that may be caused by stroke or brain tumors. This approach, known as “lesion-deficit mapping,” is the most powerful method for localizing function in the human brain. However, studying brain injuries can be difficult and time-consuming because researchers need a large number of patients with specific brain damage. This kind of damage can affect how a person thinks, feels, or moves. However, very few research centers have access to enough patients to conduct these studies effectively.
As a result, previous studies have mainly relied on functional imaging (fMRI) techniques in healthy individuals. However, these results can sometimes be misleading as they provide correlational rather than causal evidence. As the authors pointed out, “An important caveat of fMRI techniques is that they cannot reliably differentiate regions activated in the exercise of a cognitive ability from those necessary for it.”
For their newly reported study, the researchers used lesion-deficit mapping to investigate 247 patients with unilateral focal brain lesions in either the left or right frontal (front) or posterior (back) regions of the brain. An additional 81 healthy individuals served as controls. “Lesion studies on patients with focal, unilateral, brain damage, caused by pathologies such as brain tumor or stroke, offer a unique opportunity to further our understanding of the neurocognitive architecture underpinning reasoning,” the investigators noted. “In contrast to studies using functional neuroimaging, focal lesion studies provide causal—rather than correlational—evidence.”
For their reported study, and to assess the reasoning skills of the participants, the researchers developed two new tests. One is a verbal deductive reasoning task—a type of puzzle where participants are asked to find relationships between words to solve problems—which included questions such as: “If Sarah is smarter than Diana and Sarah is smarter than Heather, is Diane smarter than Heather?”
The other is a nonverbal analogical reasoning task—a type of puzzle where participants are asked to use pictures, shapes, or numbers to figure out logical patterns and solve problems—with questions such as, “Which set of numbers is 1,2,3 most similar to—5,6,7 or 6,5,7?”
The test results showed that people with damage to the right frontal lobe had a much harder time on both tests compared to those with damage in other areas. These individuals made about 15% more mistakes than the other patients and healthy individuals. The results of their behavioral and neuroimaging analyses converged to implicate a right frontal network in analogical reasoning test (ART) and deductive reasoning test (DRT) performance, the team noted. “Combining detailed analysis of performance on novel reasoning tests with graph-based lesion-deficit mapping in a large cohort has provided novel insights into the neural basis of reasoning.”
Mole said, “Our study explores how the front right part of the brain helps people think and solve new problems. It also shows that our two new tests can help detect reasoning problems in individuals with brain damage, improving diagnosis and treatment.” Added Cipolotti, “By combining a detailed cognitive investigation in a large sample of brain-damaged patients with advanced lesion mapping techniques—developed by professor Parashkev Nachev and his team at the UCL Queen Square Institute of Neurology—we have deepened our understanding of the complex and, so far, poorly understood, neural structures underlying human reasoning.”
The researchers believe that their findings could have significant clinical implications, as the two new tests can help identify cognitive impairments that would otherwise go undetected. “Our findings imply that a right frontal network is critical for aspects of AR and DR,” they stated. “They also suggest that the ART and DRT are promising new tests, capable of evaluating reasoning abilities and identifying right frontal lobe dysfunction.”
With further validation and implementation, the team aims to make their new reasoning tests widely available in the NHS, addressing an unmet need for tools specifically designed for assessing right frontal lobe dysfunction. “Our findings suggest that the ART and DRT may provide useful information in clinical practice,” they stated. “To date, only a very small number of clinical tests have been shown capable of detecting right frontal lobe dysfunction. Translating the ART and DRT into clinical practice may address this unmet need. Notably, both tests also lack ceiling effects: an issue that applies to many existing neuropsychological tests.”