Testing the Darwinian function of lateralization. Does separation of workload between brain hemispheres increase...

Area of Science:

• Neuroscience
• Cognitive Psychology
• Evolutionary Biology

Background:

• Brain lateralization, the asymmetric organization of cognitive functions, is a key feature of brain and behavior across the animal kingdom.
• The evolutionary advantage and impact of brain lateralization on cognitive performance, especially in complex tasks, remain incompletely understood.
• Previous research on lateralization and cognitive performance has yielded inconsistent results, highlighting the need for simultaneous measurement of both.

Purpose of the Study:

• To investigate the influence of the strength and direction of functional brain lateralization on cognitive performance in single- and dual-task conditions.
• To examine the relationship between brain lateralization patterns and performance in visuospatial (mental rotation) and language (word generation) tasks.

Main Methods:

• Seventy-two participants performed mental rotation and word generation tasks individually and concurrently (dual-task).
• Functional Transcranial Doppler sonography was used to assess brain lateralization (strength and direction) during single-task performance.
• A General Linear Model (GLM) analysis evaluated the predictive power of lateralization strength, direction, and pattern, along with sex, on task performance.

Main Results:

• For the mental rotation task, the direction of lateralization significantly affected performance, with left-lateralized individuals showing better results.
• The strength of lateralization positively correlated with performance in the dual-task condition, indicating enhanced efficiency with stronger lateralization.
• No significant associations were found between the pattern of lateralization (contralateral vs. ipsilateral) and performance in either task.

Conclusions:

• The findings suggest that the strength of brain lateralization, rather than its direction or pattern, may contribute to enhanced cognitive performance, particularly under dual-task demands.
• These results do not support the hemispheric crowding hypothesis but provide evidence that lateralization strength could be a target for evolutionary selection.
• Individual variations in cognitive performance may not be explained by the specific pattern of brain lateralization.