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Abstract:
Abstract: It is generally assumed that right-handedness is a
uniquely human trait (Hiscock & Kinsbourne 1995). In rats,
although population asymmetry has been reported for spatial,
emotional, and auditory processing (Denenberg et al. 1978, Glick
and Ross 1981, Lamendola & Bever 1997, Fitch et al. 1993) and
for brain lesion effects (Robinson 1979), a population bias in paw
use has not been firmly established. This study was designed to
investigate whether a carefully controlled testing environment
would reveal stable long-term population level paw biases in rats
and whether neonatal stimulation would modulate the expression of
directional lateralization in paw preference. We ran both handled
(n= 26) and control (n= 26) groups in a self designed
reach-to-grasp task at two months and eight months of age. Our
results indicate a stable right-paw population bias in the control
rats (60% right; 25% left; 15 ambidextrous) across multiple days of
testing and over a six month period. We also found that neonatal
stimulation shifted the population paw bias from the right to left
(t= 1.92, p= 0.030). These results suggest that a phylogenetic
continuity exists in not only spatial, emotional, and auditory
processing asymmetry but in hand-dominance as well, and that the
development of paw dominance is sensitive to early life
experience.
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