Observation of Emerging Hand Preference Reflected in Hemispheric EEG Patterns in Infants with Typical Development

Authors

Kashish H. Chainani, University of Southern CaliforniaFollow
Riley Elmer, University of Southern CaliforniaFollow
Erika G. Mora, University of Southern CaliforniaFollow
Beth A. Smith, University of Southern CaliforniaFollow

Abstract

ABSTRACT

Reaching behavior in infants typically emerges around 4 months of age. Neural mechanisms reflected in reaching behavior are crucial for understanding brain organization, cognitive processing, and typical neuromotor development.

PURPOSE:

This study investigates the relationship between emerging hand bias and hemispheric electroencephalography (EEG) activity in infants with typical development. We hypothesize that within subjects, brain activation (EEG relative power) will be greater in the left hemisphere (C3) in infants with right reach bias (RB) and greater in the right hemisphere (C4) in infants with left reach bias (LB), with no significant differences between hemispheres for infants with no reach bias (NB).

METHODS:

Infants with typical development (N=38, M age = 4.72 months) wore a 32 channel EEG cap and were observed while reaching for a midline presented toy. Reach bias (LB: n = 10, RB: n = 13, NB: n = 15) was determined from video coded reaches. EEG data were preprocessed to extract relative power (proportion of a frequency band activation relative to total activation) from left (C3) and right (C4) motor cortex electrodes in delta (2–4 Hz), theta (4–6 Hz), and alpha (6–9 Hz) bands. Relative power was compared across hemispheres and bias groups using paired statistical tests.

RESULTS:

Within subjects, infants with RB showed greater contralateral (C3) than ipsilateral (C4) activation in delta (MC3=0.0066; SDC3=0.0035) (MC4=0.0049; SDC4=0.0028), theta (MC3=0.0024; SDC3=0.0015) (MC4=0.0017; SDC4=0.0011), and alpha bands (MC3=0.00086; SDC3=0.00053) (MC4=0.00064; SDC4=0.00043) (p ≤ 0.0081), with large effect sizes (0.71–0.88); differences remained for all bands after statistical corrections for multiple comparisons. Infants with LB and NB showed no significant hemispheric differences (p ≥ 0.108, effect sizes ≤0.45).

CONCLUSION:

Infants with RB exhibited greater activation in the contralateral motor cortex (C3), across frequency bands. In contrast, infants with LB and NB showed no consistent hemispheric asymmetry. These results may suggest that early hand reaches demonstrate lateralized neural activity. While limitations include small sample size and few reaches, this preliminary work aids in understanding the early correlates of motor development and infant brain organization.

Recommended Citation

Chainani, Kashish H.; Elmer, Riley; Mora, Erika G.; and Smith, Beth A. (2025) "Observation of Emerging Hand Preference Reflected in Hemispheric EEG Patterns in Infants with Typical Development," International Journal of Exercise Science: Conference Proceedings: Vol. 14: Iss. 5, Article 76.
Available at: https://digitalcommons.wku.edu/ijesab/vol14/iss5/76