Summary: Efficient, brain-wide white matter connections form a network that supports general cognitive ability. Higher fractional anisotropy across these pathways is linked to higher IQ.
Source: National University of Ireland Galway
An international team led by researchers at NUI Galway has identified how brain wiring relates to general cognitive ability (IQ).
Using diffusion tensor imaging (DTI), the study examined how subtle differences in the brain’s white matter — the wiring that connects distinct brain regions — relate to intelligence. The project pooled data from multiple institutions through the ENIGMA Schizophrenia Working Group to compare healthy individuals and people with schizophrenia, seeking to clarify how white matter organization contributes to cognitive performance.
The analysis included 1,717 participants in total, combining brain MRI scans and standardized measures of cognitive function from both healthy volunteers and patients diagnosed with schizophrenia. Over 40 researchers across several countries contributed to harmonizing data collection and analysis, applying a common pipeline so results could be reliably compared across sites. The work was published in The American Journal of Psychiatry and led by Dr. Laurena Holleran, Lecturer in Clinical Neuroscience, and Professor Gary Donohoe of NUI Galway’s School of Psychology and Centre for Neuroimaging, Cognition and Genomics.
Lead author Dr. Laurena Holleran emphasized the study’s scale and relevance: to date, this is the largest meta-analysis linking brain structure and cognitive function in schizophrenia. She noted that understanding the neural basis of cognition is crucial for developing treatments that target cognitive deficits, which are not adequately addressed by current therapies. Cognitive impairments strongly predict real-world outcomes — such as employment and social functioning — so clarifying their biological roots matters for patient care and recovery.
Previous studies often highlighted specific grey matter regions — including temporal, parietal and frontal lobes — as central to intelligence. However, this large-scale analysis found that intelligence is closely related to the integrity of white matter across the entire brain. In other words, efficient, widespread connectivity rather than a single localized area appears to underlie general cognitive ability.
Professor Gary Donohoe, senior author of the study, explained the main advances: the link between brain structure and intelligence involves white matter as well as grey matter; it depends on the combined integrity of the brain’s wiring rather than any single tract; and critically, the pattern of association between white matter and IQ is similar for people with schizophrenia and for healthy individuals. While patients with schizophrenia tended to have lower fractional anisotropy and lower IQ on average, the relationship between connectivity and cognitive ability was comparable in both groups. This suggests that the role of white matter in shaping cognitive function is general rather than disorder-specific.
Source:
National University of Ireland Galway
Media contact:
Sheila Gorham – National University of Ireland Galway
Image source:
The image is in the public domain.
Original research (closed access):
“The Relationship Between White Matter Microstructure and General Cognitive Ability in Patients With Schizophrenia and Healthy Participants in the ENIGMA Consortium.” Laurena Holleran et al., American Journal of Psychiatry. DOI: 10.1176/appi.ajp.2019.19030225
Abstract (summary)
Objective:
Recent research has reported widespread white matter microstructural abnormalities in schizophrenia, but how these changes translate to cognitive function is unclear. Prior studies produced heterogeneous results, so this study used a coordinated meta-analytic approach within the ENIGMA Consortium to clarify the relationship between white matter structure and general cognitive ability (IQ) in schizophrenia and in healthy controls.
Methods:
The meta-analysis combined data from 11 ENIGMA sites, including 760 patients with schizophrenia and 957 healthy participants. For each site, researchers used principal component analysis to derive a global fractional anisotropy component (gFA) and fractional anisotropy components for six long association tracts (LA-gFA) previously implicated in cognitive function.
Results:
Across the full sample, global fractional anisotropy (gFA) significantly accounted for variation in cognitive performance (Hedges’ g = 0.27, 95% CI = 0.17–0.36). Similar effect sizes were observed separately in patients (g = 0.20, 95% CI = 0.05–0.35) and healthy participants (g = 0.32, 95% CI = 0.18–0.45). Comparable associations emerged for the long association tract component (LA-gFA): full sample effect size = 0.28 (95% CI = 0.18–0.37); patient group = 0.23 (95% CI = 0.09–0.38); healthy group = 0.31 (95% CI = 0.18–0.44).
Conclusions:
The findings provide robust evidence that general cognitive ability is related to global structural connectivity in the brain. Higher fractional anisotropy — reflecting better-organized white matter — is associated with higher IQ. Although schizophrenia patients, on average, showed lower fractional anisotropy and lower cognitive scores, the comparable effect sizes across groups indicate a general relationship between white matter integrity and intelligence rather than one confined to a specific diagnosis.