Lab for Clinical & Integrative Neuroscience, School of Behavioral and Brain Sciences, The University of Texas at Dallas, USA.
Lab for Clinical & Integrative Neuroscience, School of Behavioral and Brain Sciences, The University of Texas at Dallas, USA.
Prog Neurobiol. 2017 Jun;153:1-17. doi: 10.1016/j.pneurobio.2017.03.010. Epub 2017 Apr 11.
It is suggested that the brain undergoes plastic changes in order to adapt to changing environmental needs. Sensory deprivation results in decreased input to the brain leading to adaptive or maladaptive changes. Although several theories hypothesize the mechanism of these adaptive and maladaptive changes, the course of action taken by the brain heavily depends on the age of incidence of damage. The growing body of literature on the topic proposes that maladaptive changes in the brain are instrumental in creating phantom percepts, defined as the perception of a sensory experience in the absence of a physical stimulus. The current article reviews the mechanisms of adaptive and maladaptive plasticity in the brain in congenital, early, and late-onset sensory deprivation in conjunction with the phantom percepts in the different sensory domains. We propose that the mechanisms of adaptive and maladaptive plasticity fall under a universal construct of updating hierarchical Bayesian prediction errors. This theory of the Bayesian brain hypothesizes that the brain constantly compares its internal milieu with changing environmental cues and either adjusts its predictions or discards the change, depending on the novelty or salience of the external stimulus. We propose that adaptive plasticity reflects both successful bottom-up compensation and top-down updating of the model while maladaptive plasticity reflects failure in one or both mechanisms, resulting in a constant prediction-error. Finally, we hypothesize that phantom percepts are generated by the brain as a solution to this prediction error and are thus a manifestation of unsuccessful adaptation to sensory deprivation.
有人认为，大脑会发生可塑性变化，以适应环境需求的变化。感觉剥夺会导致大脑输入减少，从而导致适应性或不良性变化。虽然有几种理论假设了这些适应性和不良性变化的机制，但大脑采取的行动过程在很大程度上取决于损伤发生的年龄。关于这个主题的大量文献表明，大脑的不良性变化在产生幻觉感知中起着重要作用，幻觉感知是指在没有物理刺激的情况下感知到一种感觉体验。本文综述了先天性、早期和晚期感觉剥夺时大脑适应性和不良性可塑性的机制，并结合不同感觉域中的幻觉感知进行了讨论。我们提出，适应性和不良性可塑性机制属于更新分层贝叶斯预测误差的普遍结构。贝叶斯大脑理论假设，大脑会不断将其内部环境与变化的环境线索进行比较，并根据外部刺激的新颖性或显著性来调整其预测或放弃变化。我们提出，适应性可塑性反映了自上而下的模型更新和自下而上的补偿的成功，而不良性可塑性反映了一种或两种机制的失败，导致持续的预测误差。最后，我们假设幻觉感知是大脑为了解决这种预测误差而产生的，因此是对感觉剥夺适应不良的表现。
