Left out: The effect of handedness on fMRI activation in memory paradigms
- 1Department of Psychology, Brigham Young University, Provo, UT, United States
- 2MindCORE Neuroimaging Facility, University of Pennsylvania, Philadelphia, PA, United States
Abstract
About 11% of the population is left-handed, a significant minority of the potential participant pool for functional MRI (fMRI) studies. However, convention in fMRI research dictates these potential participants be excluded due to the supposition that left-handed (LH) people may have different lateralization of neural functioning than right-handed (RH) people. This difference in lateralization may cause different areas of the brain to be activated by the same task. The current study investigates the lateralization differences between LH (n = 54) and RH (n = 55) participants during encoding and recognition memory tasks for verbal and non-verbal stimuli. Additionally, we measured participants’ language laterality index by administering a semantic fluency task. We found no difference between groups’ behavioral memory performance for either verbal or non-verbal stimuli. Similarly, we found no group differences in fMRI activation for either verbal or non-verbal material at encoding or retrieval. When we split groups according to language lateralization, we observed more activation in right-lateralized participants for word retrieval only. To measure whether including LH in fMRI studies would dilute results, we performed Monte Carlo simulations with subsets of our data for sample sizes from n = 10 to 50 with the number of LH in each sample ranging from k = 0 to 9. Similarity metrics between activation maps for the all-RH sample and samples that include LH participants were robust, especially for large sample sizes (e.g., Dice similarity coefficients >0.9 when n = 50). Taken together, these results indicate that the inclusion of left-handed participants does not have a strong detrimental effect on memory-related fMRI activation. On this basis, we advocate for the inclusion of left-handed participants in cognitive neuroscience of memory research.
Related
- Precision fMRI reveals that the language network exhibits adult-like left-hemispheric lateralization by 4 years of age
- A spatio-temporal fingerprints with hierarchical activation refinement for predicting task activation maps from resting-state fMRI
- Large-Vessel Venous Signal Confounds Apparent Amygdala Activation in BOLD fMRI
- Dimensional and Categorical Predictors of Theory of Mind Network Activation: A transdiagnostic fMRI Study in Psychiatric Inpatients
- Cognitive Control as a Brake on the Depression–Internet Addiction Link: Task-Based fMRI Evidence from Activation and Task-Modulated Functional Connectivity
BibTeX
@article{goulding2026left,
title = {{Left out: The effect of handedness on fMRI activation in memory paradigms}},
author = {Loriana Goulding and Isaac Hamm and C. Brock Kirwan},
journal = {Imaging Neuroscience},
year = {2026},
month = nov,
doi = {10.1162/imag.a.1441},
url = {https://doi.org/10.1162/imag.a.1441},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Left out: The effect of handedness on fMRI activation in memory paradigms
AU - Loriana Goulding
AU - Isaac Hamm
AU - C. Brock Kirwan
PY - 2026
DA - 2026/11/03
JO - Imaging Neuroscience
DO - 10.1162/imag.a.1441
UR - https://doi.org/10.1162/imag.a.1441
AB - About 11% of the population is left-handed, a significant minority of the potential participant pool for functional MRI (fMRI) studies. However, convention in fMRI research dictates these potential participants be excluded due to the supposition that left-handed (LH) people may have different lateralization of neural functioning than right-handed (RH) people. This difference in lateralization may cause different areas of the brain to be activated by the same task. The current study investigates the lateralization differences between LH (n = 54) and RH (n = 55) participants during encoding and recognition memory tasks for verbal and non-verbal stimuli. Additionally, we measured participants’ language laterality index by administering a semantic fluency task. We found no difference between groups’ behavioral memory performance for either verbal or non-verbal stimuli. Similarly, we found no group differences in fMRI activation for either verbal or non-verbal material at encoding or retrieval. When we split groups according to language lateralization, we observed more activation in right-lateralized participants for word retrieval only. To measure whether including LH in fMRI studies would dilute results, we performed Monte Carlo simulations with subsets of our data for sample sizes from n = 10 to 50 with the number of LH in each sample ranging from k = 0 to 9. Similarity metrics between activation maps for the all-RH sample and samples that include LH participants were robust, especially for large sample sizes (e.g., Dice similarity coefficients >0.9 when n = 50). Taken together, these results indicate that the inclusion of left-handed participants does not have a strong detrimental effect on memory-related fMRI activation. On this basis, we advocate for the inclusion of left-handed participants in cognitive neuroscience of memory research.
SN - 2837-6056
ER -