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New Approach to Brain Mapping Identifies Region Responsible for Fluid Intelligence

Researchers employ cognitive testing and lesion-deficit mapping to find the origin of fluid intelligence

Holden Galusha

Holden Galusha is the associate editor for Lab Manager. He was a freelance contributing writer for Lab Manager before being invited to join the team full-time. Previously, he was the...

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Crystallized and fluid intelligence are two theorized systems of intelligence. Crystallized intelligence, which is essentially the ability to apply past knowledge to problem solving, grows throughout life and is coupled with memory. Conversely, fluid intelligence is the ability to solve novel problems with no prior experience to draw from. Fluid intelligence is closely associated with performance in certain activities, especially abstract tasks like mathematics.

Like virtually all proposed theories of intelligence, however, this idea of intelligence remains open for debate. For instance, we don’t know if fluid intelligence is a singular cognitive ability or the cumulative result of several abilities. To investigate the nature of fluid intelligence and how it relates to the brain, researchers have typically used functional imaging (fMRI) techniques in tandem with lesion-deficit mapping, in which they study the cognitive abilities of patients whose brains have been damaged in certain areas. However, lesion-deficit mapping can be difficult to carry out, and fMRI results can be misleading. Consequently, there has never been a clear consensus on the nature of fluid intelligence.

To address this, researchers from the University of College London and University of College London Hospitals teamed up to investigate fluid intelligence in a new way. Their new study, published in Brain, evaluated the cognitive abilities of 227 brain tumor and stroke patients using the Raven Advanced Progressive Matrices (APM) test, which is “the best-established test of fluid intelligence.” They then employed a new approach to lesion-deficit mapping to clarify the complex anatomical patterns found in common brain injuries, such as stroke. Together, the test results and lesion-deficit mapping technique allowed the researchers to find which patients performed worst on the APM test according to their injuries.

The team found that fluid intelligence was impaired mostly in patients with right frontal lobe lesions. This type of damage is commonly found in tumor, stroke, and traumatic brain injury patients, as well as those suffering with dementia. Lead author Lisa Cipolotti, professor at the UCL Queen Square Institute of Neurology, said, “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. This supports the use of APM in a clinical setting as a way of assessing fluid intelligence and identifying right front lobe dysfunction.”