The effect of age on interhemispheric transfer time: an event related potential study

The present study sought to investigate the effects of aging on interhemispheric transfer time (IHTT). Poffenberger (1912) devised a behavioural paradigm thought to be a measure of IHTT. In this paradigm IHTT is estimated by calculating the crossed-uncrossed difference (CUD); the difference in speed of response between responses made in response to stimuli contralateral to responding hand (crossed) and those made by hands ipsilateral to the stimuli (uncrossed). IHTT can also be estimated through event related potentials (ERPs) by calculating latency differences between the waveforms over the ipsilateral and contralateral hemispheres. Results from previous experiments comparing younger and older participants with these two methods are inconsistent. Twenty three younger (18-25 years) and 23 older (65-77 years) participants had their electroencephalogram (EEG) recorded whilst completing the Poffenberger paradigm. IHTT estimates from the two measures were compared between the groups. Older participants were found to have a faster IHTT estimate from the P1 ERP component compared to younger participants. This result is in contrast to the current literature. Replication of this result is recommended before firm conclusions about its implications can be made.