The Journal of Neuroscience, March 1, 1999, 19(5):1885-1894
Complete Compensation in Skilled Reaching Success with Associated
Impairments in Limb Synergies, after Dorsal Column Lesion in the
Rat
John E.
McKenna and
Ian Q.
Whishaw
Department of Psychology and Neuroscience, University of
Lethbridge, Alberta, Canada, T1K 3M4
Each of the dorsal columns of the rat spinal cord conveys primary
sensory information, by way of the medullary dorsal column nucleus, to
the ventrobasal thalamus on the contralateral side; thus the dorsal
columns are an important source of neural input to the sensorimotor
cortex. Damage to the dorsal columns causes impairments in synergistic
proximal or whole-body movements in cats and distal limb impairments in
primates, particularly in multiarticulated finger movements and tactile
foviation while handling objects, but the behavioral effects of
afferent fiber lesions in the dorsal columns of rodents have not been
described. Female Long-Evans rats were trained to reach with a
forelimb for food pellets and subsequently received lesions of the
dorsomedial spinal cord at the C2 level, ipsilateral to their preferred
limb. Reaching success completely recovered within a few days of dorsal column lesion. Nevertheless, a detailed analysis of high-speed video
recordings revealed that rotatory limb movements (aiming, pronation,
supination, etc.) were irreversibly impaired. Compensation was achieved
with whole-body and alternate limb movements. These results indicate
the following: (1) in the absence of the dorsal columns, other
sensorimotor pathways support endpoint success in reaching; (2) sensory
input conveyed by the dorsal columns is important for both proximal and
distal limb movements used for skilled reaching; and (3) detailed
behavioral analyses in addition to endpoint measures are necessary to
completely describe the effects of dorsal column lesions.
Key words:
dorsal column; lesion; skilled movement; recovery of
function; forelimb; food handling; reaching; spinal cord; injury; rat
Copyright © 1999 Society for Neuroscience 0270-6474/99/1951885-10$05.00/0
