Interhemispheric collaboration during digit and dot number-matching in younger and older adults

Digit and dot number-matching stimuli were used to replicate findings reported for younger adults by Patel and Hellige (2007) and to explore whether performance would differ for younger versus older participants. Participants were to make numerical matches of digits only, dots only, and digits and dots mixed conditions to determine whether reaction time (RT), percentage error, and efficiency scores that combine latency and accuracy for match trials were better on within- versus across-hemisphere trials. Sixty-six younger and 42 older participants were screened with the Mini-Mental State Examination (MMSE) and the Geriatric Depression Scale. They performed the three experimental conditions and were assessed with Digit Span Forward and Backward subscales from the Wechsler Adult Intelligence Scale-III. Results for younger adults demonstrated a within-hemisphere advantage for the Digits and Mixed conditions and an across-hemisphere advantage for the Dots condition, consistent with previous literature. Older participants showed a stronger within-hemisphere advantage for the Digits condition compared with younger participants and no advantage for within- or across-hemisphere processing for the Mixed condition when RT was considered, but they performed similarly to younger adults when efficiency scores were used and showed a relative across-hemisphere advantage for the Dots condition. Although RT suggests age-related differences in how information is distributed across the hemispheres of the brain, more comprehensive efficiency scores indicate that younger and older adults appear to use similar strategies in the coordination of interhemispheric transfer of information. MMSE scores regardless of age were related to type of task but not to across- versus within-hemisphere performance.