Cohen Jeremy D, Castro-Alamancos Manuel A
Deptartment of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Ln., Philadelphia, PA 19129, USA.
J Neurophysiol. 2005 Mar;93(3):1486-97. doi: 10.1152/jn.00958.2004. Epub 2004 Nov 3.
Learning of motor skills may occur as a consequence of changes in the efficacy of synaptic connections in the primary motor cortex. We investigated if learning in a reaching task affects the excitability, short-term plasticity, and long-term plasticity of horizontal connections in layers II-III of the motor cortex. Because training in this task requires animals to be food-deprived, we compared the trained animals with similarly food-deprived untrained animals and normal controls. The results show that the excitability, short-term plasticity, and long-term plasticity of the studied horizontal connections were unaffected by motor learning. However, stress-related effects produced by food deprivation and handling significantly enhanced the expression of long-term depression in these pathways. These results are compatible with the hypothesis that the acquisition of a complex motor skill produces bi-directional changes in synaptic strength that are distributed throughout the complex neural networks of motor cortex, which remains synaptically balanced during learning. The results are incompatible with the idea that learning causes large unidirectional changes in the population response of these neural networks, which may occur instead during certain behavioral states, such as stress.
运动技能的学习可能是初级运动皮层中突触连接效能变化的结果。我们研究了在一项伸手任务中的学习是否会影响运动皮层II-III层水平连接的兴奋性、短期可塑性和长期可塑性。由于该任务的训练要求动物处于食物剥夺状态，我们将训练动物与同样处于食物剥夺状态的未训练动物以及正常对照进行了比较。结果表明，所研究的水平连接的兴奋性、短期可塑性和长期可塑性不受运动学习的影响。然而，食物剥夺和处理产生的应激相关效应显著增强了这些通路中长时程抑制的表达。这些结果与以下假设相符：复杂运动技能的习得会在整个运动皮层复杂神经网络中产生双向的突触强度变化，且在学习过程中突触保持平衡。这些结果与学习会导致这些神经网络群体反应出现大的单向变化的观点不相符，这种单向变化可能反而发生在某些行为状态下，比如应激状态。
