Region of Brain Responsible for Fluid Intelligence Located

Researchers in London have mapped the parts of the brain that supports “fluid intelligence,” which is the brain’s ability to solve problems without prior experience. Arguably the defining feature of human cognition, fluid intelligence predicts educational and professional success, social mobility, health, and longevity and also correlates with cognitive abilities like memory. Fluid intelligence is thought to be a key feature involved in “active thinking,” a set of complex mental processes such as those involved in abstraction, judgment, attention, strategy generation and inhibition. Such skills can all be used in everyday activities, from organizing a dinner party to filling out a tax return.

But despite its central role in human behavior, whether fluid intelligence is a single cognitive ability or a cluster and its relationship to the rest of the brain have been contentious topics in the research community. To establish which parts of the brain are necessary for a certain ability, researchers must study patients in whom that part is either missing or damaged. Such “lesion-deficit mapping” studies are difficult to conduct owing to the challenge of identifying and testing patients with focal brain injury. Consequently, previous studies have mainly used functional imaging (fMRI) techniques, which can be misleading.

But the new study, led by University College London Queen Square Institute of Neurology and National Hospital for Neurology and Neurosurgery at UCLH, investigated 227 patients who had suffered either a brain tumor or stroke to specific parts of the brain. The study used Raven Advanced Progressive Matrices (APM), the best-established test of fluid intelligence. APM contains multiple choice visual pattern problems of increasing difficulty; each problem presents an incomplete pattern of geometric figures and requires selection of the missing piece from a set of multiple possible choices.

The researchers then introduced a novel “lesion-deficit mapping” approach to disentangle the intricate anatomical patterns of common forms of brain injury, such as stroke. The approach treated the relations between brain regions as a mathematical network whose connections describe the tendency of regions to be affected together, either because of the disease process or in reflection of common cognitive ability. This enabled researchers to disentangle the brain map of cognitive abilities from the patterns of damage, allowing them to map the different parts of the brain and determine which patients did worse in the fluid intelligence task according to their injuries.

They found that impaired fluid intelligence was largely confined to patients with right frontal lesions. Alongside brain tumors and stroke, such damage is often found in patients with a range of other neurological conditions, including traumatic brain injury and dementia.

 “Our findings indicate for the first time that the right frontal regions of the brain are critical to the high-level functions involved in fluid intelligence, such as problem solving and reasoning,” says lead author Professor Lisa Cipolotti of UCL Queen Square Institute of Neurology. “This supports the use of APM in a clinical setting, as a way of assessing fluid intelligence and identifying right frontal lobe dysfunction.

Cipolotti adds that combining novel lesion-deficit mapping with detailed investigation of APM performance in a large sample of patients provides crucial information about the neural basis of fluid intelligence. “More attention to lesion studies is essential to uncover the relationship between the brain and cognition, which often determines how neurological disorders are treated.”

The findings were published recently in Brain, a peer-reviewed journal.