Individual Differences in Neurobehavioral Measures of Laterality and Interhemispheric Function as Measured by Dichotic Listening

Abstract

This article presents analysis of dichotic listening performance in 57 healthy men and women aged 20 to 72 years. The data are presented as a means to cover 2 theoretical issues relevant to the biobehavioral study of laterality and interhemispheric relations. First, the sensitivity of dichotic listening performance to factors such as sex, age, and their interactions was examined. Dichotic listening asymmetry scores were found to vary as a function of sex, age, handedness, and family history of developmental language disorders. The effects of sex and age were then explored in relation to a comparison of nonforced and unilaterally focused test conditions. The results suggest that even within a healthy, normative sample of human participants, individuals vary not only in their underlying perceptual asymmetries for auditory input, but also in the manner in which such asymmetries interact with other higher order cognitive functions.

Dichotic listening asymmetry: Sex differences and menstrual cycle effects

“…Sex differences in dichotic listening across the life span (Cowell & Hugdahl, 2000) paralleled effects independently observed in corpus callosum anatomy (Cowell, Allen, Zalatimo, & Denenberg, 1992). Jointly, these studies (Cowell & Hugdahl, 2000;Cowell et al, 1992) suggest that as hormone levels decrease in women between the third and fifth decades of life, increases in anterior corpus callosum size may lead to less separation (i.e., greater connection) of left and right hemispheres, and, in turn, to the observed decrease in REA. In men, the anterior callosum decreased with age after the third decade of life, possibly contributing to greater separation of left and right hemispheres, and, in turn, to the increase in REA.…”

“…Sex differences in dichotic listening, with males having a greater REA than women, have been reported in some (Cowell & Hugdahl, 2000;Weekes et al, 1995) but not all studies (Foundas et al, 2006;Hiscock et al, 1994). In the current study a significant sex difference in laterality was found only when men were compared to women at the Low-EP phase.…”

“…Cowell and Hugdahl (2000) showed age-related decrease in the right ear advantage in women compared to age-related increase in men from age 20 to 70 years. In that study, sex differences were more prominent as age increased.…”

“…Some studies have shown larger asymmetry in men than women (Cowell & Hugdahl, 2000;Weekes, Zaidel, & Zaidel, 1995) while others have not (Demarest & Demarest, 1981;Foundas, Corey, Hurley, & Heilman, 2006;Hiscock & MacKay, 1985). Cowell and Hugdahl (2000) showed that REA decreased with age in women and increased with age in men across the adult lifespan. Thus, the male-greaterthan-female asymmetry was more prominent in older compared to younger adults.…”

“…Thus, a smaller corpus callosum has been associated with greater functional separation of the hemispheres (Hines, Chiu, McAdams, Bentler, & Lipcamon, 1992;Pollmann, Maertens, von Cramon, Lepsien, & Hugdahl, 2002;Reinvang, Bakke, Hugdahl, Karlsen, & Sundet, 1994). Sex differences in dichotic listening across the life span (Cowell & Hugdahl, 2000) paralleled effects independently observed in corpus callosum anatomy (Cowell, Allen, Zalatimo, & Denenberg, 1992). Jointly, these studies (Cowell & Hugdahl, 2000;Cowell et al, 1992) suggest that as hormone levels decrease in women between the third and fifth decades of life, increases in anterior corpus callosum size may lead to less separation (i.e., greater connection) of left and right hemispheres, and, in turn, to the observed decrease in REA.…”