Complementarity of linguistic and prosodic processes in the intact brain

Despite considerable speculation in the research literature regarding the complementarity of functional lateralization of prosodic and linguistic processes in the normal intact brain, few studies have directly addressed this issue. In the present study, behavioral laterality indices of emotional prosodic and traditional linguistic speech functions were obtained for a sample of healthy young adults, using the dichotic listening method. After screening for adequate emotional prosody and linguistic recognition abilities, participants completed the Fused Rhymed Words Test (FRWT; Wexler & Halwes, 1983) and the Dichotic Emotion Recognition Test (DERT; McNeely & Netley, 1998). Examination of the difference in ear asymmetries for these measures within individuals revealed a complementary pattern in 78% of the sample. However, the correlation between laterality quotients for the FRWT and DERT was near zero, supporting Bryden's model of "statistical" complementarity (e.g., Bryden, 1990).

The temporal locus of transfer of training between hands: an interference study

Two experiments are presented which used a dual-task interference procedure to examine the temporal locus of lateral transfer of training. In Experiment 1, 120 undergraduates practised a sequential tapping task with either the left or the right hand, and then switched to the opposite, untrained hand for the test trials. Performance of an unrelated bulb-gripping task with the opposite hand during test trials but not during training trials effectively eliminated transfer of training between the hands for this skill. Because this contradicted the findings of Hicks, Frank and Kinsbourne (J. Gen. Psychol., 107 (1982) 277-281), we then attempted to replicate their study in a second experiment, with 48 subjects. Subjects who gripped a table leg during training trials performed as well during test trials as subjects who did not. We concluded (a) that transfer of training between the hands (cerebral hemispheres) occurs relatively late, when the individual switches to the untrained hand, and (b) that motor overflow is not critical to lateral transfer of training. These data are compatible with a callosal access model of interhemispheric interaction.

Asymmetrical movement overflow in children depends on handedness and task characteristics

Unintentional movement overflow between the hands was examined in 176 right-handed children in grades 2, 4, and 6. A significant multivariate hand difference was observed for contralateral but not for ipsilateral overflow during rapid repetitive movements and discrete finger placement tasks. Individual ANOVAs revealed greater overflow from left to right hands during forearm pronation/supination (a rapid repetitive task) but the reverse during finger-displacement tasks. Hand differences in contralateral overflow were also observed in 19 left-handed children, with greater overflow from right to left hands observed for two tasks. These data support previous reports of asymmetrical overflow, but suggest that the presence and direction of the phenomenon depends on the nature of the intended movement and on handedness.

Asymmetrical transfer of training between hands: implications for interhemispheric communication in normal brain

Two experiments are presented which investigated claims of asymmetrical transfer of training between the hands/hemispheres. In Experiment 1, 96 right- and left-handed male undergraduates practiced an inverted-reversed printing task with either the right or the left hand. Transfer to the opposite hand was then compared to same-hand transfer, in a between-subject design. In Experiment 2, 176 right-handed boys and girls were tested at ages 7, 9, and 11 years. For right-handed subjects in both experiments, the left hand benefited more from opposite-hand training than did the right. The reverse was true for left-handers in Experiment 1, although one group (who wrote with the "inverted" position) showed little transfer in either direction. Two current models of interhemispheric interaction do not satisfactorily explain these findings. A third model, based on cross-activation, may provide a more effective alternative.