Jablonka Jan Antoni, Binkowski Robert, Kazmierczak Marcin, Sadowska Maria, Sredniawa Władysław, Szlachcic Aleksandra, Urban Paulina
Faculty of Biology, University of Warsaw, Warsaw, Poland.
Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY, United States.
Front Neurosci. 2021 Jul 9;15:631328. doi: 10.3389/fnins.2021.631328. eCollection 2021.
Despite the fact that there is a growing awareness to the callosal connections between hemispheres the two hemispheres of the brain are commonly treated as independent structures when peripheral or cortical manipulations are applied to one of them. The contralateral hemisphere is often used as a within-animal control of plastic changes induced onto the other side of the brain. This ensures uniform conditions for producing experimental and control data, but it may overlook possible interhemispheric interactions. In this paper we provide, for the first time, direct proof that cortical, experience-dependent plasticity is not a unilateral, independent process. We mapped metabolic brain activity in rats with 2-[C] deoxyglucose (2DG) following experience-dependent plasticity induction after a month of unilateral (left), partial whiskers deprivation (only row B was left). This resulted in ∼45% widening of the cortical sensory representation of the spared whiskers in the right, contralateral barrel field (BF). We show that the width of 2DG visualized representation is less than 20% when only contralateral stimulation of the spared row of whiskers is applied in immobilized animals. This means that cortical map remodeling, which is induced by experience-dependent plasticity mechanisms, depends partially on the contralateral hemisphere. The response, which is observed by 2DG brain mapping in the partially deprived BF after standard synchronous bilateral whiskers stimulation, is therefore the outcome of at least two separately activated plasticity mechanisms. A focus on the integrated nature of cortical plasticity, which is the outcome of the emergent interactions between deprived and non-deprived areas in both hemispheres may have important implications for learning and rehabilitation. There is also a clear implication that there is nothing like "control hemisphere" since any plastic changes in one hemisphere have to have influence on functioning of the opposite one.
尽管人们越来越意识到大脑半球之间的胼胝体连接，但当对其中一个半球进行外周或皮质操作时，大脑的两个半球通常被视为独立的结构。对侧半球常被用作大脑另一侧诱导的可塑性变化的动物体内对照。这确保了产生实验数据和对照数据的条件一致，但可能会忽略可能的半球间相互作用。在本文中，我们首次提供了直接证据，证明皮质的、依赖经验的可塑性不是一个单侧的、独立的过程。在单侧（左侧）部分触须剥夺（仅保留B排）一个月后，我们用2-[C]脱氧葡萄糖（2DG）对大鼠进行经验依赖性可塑性诱导后，绘制了其大脑代谢活动图。这导致右侧对侧桶状皮质区（BF）中保留触须的皮质感觉表征扩大了约45%。我们发现，在固定动物中仅对保留的触须排进行对侧刺激时，2DG可视化表征的宽度小于20%。这意味着由经验依赖性可塑性机制诱导的皮质图谱重塑部分依赖于对侧半球。因此，在标准同步双侧触须刺激后，通过2DG脑图谱在部分剥夺的BF中观察到的反应是至少两种分别激活的可塑性机制的结果。关注皮质可塑性的整合性质，即两个半球中剥夺和未剥夺区域之间新兴相互作用的结果，可能对学习和康复具有重要意义。同样明显的是，不存在“对照半球”这样的东西，因为一个半球的任何可塑性变化都必然会影响另一侧半球的功能。
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