Ballermann M, McKenna J, Whishaw I Q
Department of Psychology and Neuroscience, University of Lethbridge, Lethbridge, Alberta, Canada.
Brain Res Bull. 2001 Jan 15;54(2):237-42. doi: 10.1016/s0361-9230(01)00431-2.
The dorsal columns of the spinal cord are a major source of haptic (sense of active touch) and proprioceptive input to the brainstem and sensory-motor cortex. Following injury in primates, there are impairments in two-point discrimination, direction of movement across the skin, and frequency of vibration, and qualitative control of the digits, but simple spatial discriminations recover. In the rat there are qualitative deficits in paw control in skilled reaching, but no sensory deficits have been reported. Because recent investigations of sensory control suggest that sensory functions may be related to specific actions, the present study investigated whether the dorsal columns contribute to hapsis during food grasping in the rat. Adult female Long-Evans rats were trained to reach with a single forepaw for a piece of uncooked pasta or for equivalent sized but tactually different nonfood items. One group was given lesions of the dorsal column ipsilateral to their preferred paw, while the second group served as a control. Postlesion, both groups were tested for skilled reaching success and force application as well as adhesive dot removal and forepaw placing. Performance levels on these tests were normal. Nevertheless, the rats with dorsal column lesions were unable to discriminate a food item from a tactually distinctive nonfood item as part of the reaching act, suggesting that the dorsal columns are important for on-line tactile discriminations, or "haptic actions," which contribute to the normal performance of grasping actions.
脊髓的背柱是向脑干和感觉运动皮层传递触觉（主动触摸感）和本体感觉输入的主要来源。在灵长类动物受伤后，两点辨别、皮肤表面移动方向、振动频率以及手指的定性控制都会出现障碍，但简单的空间辨别能力会恢复。在大鼠中，熟练抓握时爪子控制存在定性缺陷，但尚未有感觉缺陷的报道。由于最近对感觉控制的研究表明感觉功能可能与特定动作相关，本研究调查了背柱在大鼠抓取食物过程中对触觉是否有贡献。成年雌性Long-Evans大鼠经过训练，用单只前爪抓取一块生意大利面或大小相同但触觉不同的非食物物品。一组大鼠其偏好爪子同侧的背柱被损伤，而第二组作为对照。损伤后，对两组大鼠进行熟练抓握成功率、施力情况以及去除粘贴点和前爪放置等测试。这些测试的表现水平均正常。然而，背柱损伤的大鼠在抓取动作中无法区分食物和触觉上有明显差异的非食物物品，这表明背柱对于在线触觉辨别或“触觉动作”很重要，而这有助于抓握动作的正常执行。
