Age differences in visual evoked potential estimates on interhemishperic transfer.

Abstract

Twenty-six younger (ages 18-36 years) and 19 older (ages 60-88 years) healthy right-handed men and women were tested for interhemispheric transfer by using visual evoked potentials to laterally presented checkerboards. Interhemispheric transfer time (IHTT) was estimated by subtracting latencies for both P100 and N160 peaks of the waveform contralateral to the stimulus from the waveform ipsilateral to the stimulus for homologous sites. The quality of interhemispheric transfer was estimated by comparing peak-to-peak amplitudes for homologous sites. IHTT did not change across age, but there was a suppression of the waveform over the indirectly stimulated hemisphere in the older participants. The significance of this finding for age-related changes in functions mediated by the corpus callosum is discussed.The functions of the corpus callosum (CC) are beginning to be understood (see Hoptman & Davidson, 1994, for a review).It plays a critical role in information transfer between the cerebral hemispheres. In addition, interhemispheric interaction, which is primarily mediated by the CC, is beneficial under

Age-related differences in interhemispheric visuomotor integration measured by the redundant target effect.

“…Previous research investigating the CUD in healthy older adults have reported equivocal results; some studies have demonstrated significant increases in the magnitude of the CUD compared to younger adults (Jeeves & Moes, 1996;Reuter-Lorenz & Stanczak, 2000;Schulte et al, 2004;Schulte et al, 2005), while others have found no such effect (Hoptman, Davidson, Gudmundsson, Schreiber, & Ershler, 1996). The validity of the CUD as an index of callosal transmission time has been called into question by studies in which only approximately between half to two thirds of participants showed positive CUDs, suggesting that the simple anatomical model on which the CUD is based may be invalid (Saron & Davidson, 1989;Davidson, Leslie, & Saron, 1990).…”

“…The role of the corpus callosum in mediating the CUD has gained support from the findings that the CUD increases dramatically, often to around 70 ms, in patients who have had partial or complete callosotomies and those with callosal agenesis, although there are considerable individual differences (Corballis et al, 2003;Roser & Corballis, 2002;Roser & Corballis, 2003). Previous research investigating the CUD in healthy older adults have reported equivocal results; some studies have demonstrated significant increases in the magnitude of the CUD compared to younger adults (Jeeves & Moes, 1996;Reuter-Lorenz & Stanczak, 2000;Schulte et al, 2004;Schulte et al, 2005), while others have found no such effect (Hoptman, Davidson, Gudmundsson, Schreiber, & Ershler, 1996). The validity of the CUD as an index of callosal transmission time has been called into question by studies in which only approximately between half to two thirds of participants showed positive CUDs, suggesting that the simple anatomical model on which the CUD is based may be invalid (Saron & Davidson, 1989;Davidson, Leslie, & Saron, 1990).…”

Differential Effects of Aging on the Functions of the Corpus Callosum

“…Recent work by Jeeves and Moes (1996) showed that healthy adults between the ages of 60 and 82 years show a significant increase in the magnitude of the CUD compared to younger adults. Typically, the early components of the ERPs, such as the P100, are smaller in the hemisphere ipsilateral to the stimulated visual field (crossed condition) compared to those recorded from the contralateral hemisphere (uncrossed condition; for a review, see Hoptman et al, 1996). Their ERP measures of sensorimotor events were more revealing, however.…”

Fiber tract-driven topographical mapping (FTTM) reveals microstructural relevance for interhemispheric visuomotor function in the aging brain

“…Several studies indicate that the CUD is affected in older adults (Jeeves and Moes, 1996; Reuter-Lorenz and Stanczak, 2000; Schulte et al, 2004). Although not all studies could find an increase in the magnitude of the CUD in older adults (Hoptman et al, 1996), recent DTI studies have revealed correlations between subtle variations in regional white matter callosal microstructure and behavioral measures of interhemispheric transfer time and cognitive ability (Muetzel et al, 2008; Sullivan et al, 2010; Wolf et al, 2012). Fractional anisotropy (FA), an index of white matter fiber integrity, of anterior callosal regions is lower than in posterior regions and typically decreases disproportionally with advancing age (region of interest analyses: Pfefferbaum and Sullivan, 2003; Pfefferbaum et al, 2000, 2005; Salat et al, 2005; fiber tracking analyses: Stadlbauer et al, 2008; Sullivan et al, 2006, 2010; Zahr et al, 2009; stereology in postmortem human brains: Hou and Pakkenberg, 2011).…”