Abstract # 2249 Poster # 134:

Scheduled for Friday, June 22, 2007 05:00 PM-07:00 PM: Session 14 (South Main Hall) Poster Presentation

Freestanding Bipedal Posture Significantly Increases Consistency of Hand Preference in Adult Rhesus Monkeys (Macaca mulatta)

J. Christenson1, K. A. Chiodo1,2 and A. J. Bennett1
1Department of Physiology/Pharmacology and Department of Pediatrics, Wake Forest University School of Medicine, Medical Center Blvd., Winston Salem, NC 27157, USA, 2Program in Neuroscience, Wake Forest University School of Medicine
     Previous research demonstrates that bipedal posture affects both the direction and consistency of hand preference in many primate species; however, relatively little is known about the effect of postural instability on behavioral lateralization in monkeys. We examined hand preference in 22 male rhesus monkeys, twelve adult and ten adolescent. Lateral bias was compared in performance of three tasks varying in postural demands. Monkeys retrieved a small food item from a quadrupedal (QUAD), assisted bipedal (ABR), or freestanding bipedal posture. Freestanding bipedal posture was induced by positioning a small food item held from a pole above the monkey (fishing pole task; FPT). The FPT elicited significantly more consistent lateral biases in reaching when compared to the QUAD task [F(2,20)=3.69, p=0.04]. By contrast, there was no difference in consistency or direction of lateral bias between QUAD and ABR [p<0.10]. An age effect was also observed, with adults displaying increased consistency of lateral biases as postural instability increased between the three tasks, whereas the adolescents exhibited no difference in consistency between tasks [F(2,19)=3.31, p=0.05]. This study demonstrates that the FPT can be used successfully to elicit freestanding bipedal reaches in rhesus monkeys and that this postural demand increases the expression of behavioral laterality. Taken together, these results provide supportive evidence for the hypothesis that postural instability may be important to the evolution of strong behavioral asymmetries in primates. Supported by grant AA011997.