Learning and plasticity in the human brain

本研究的主要目标是：i）在神经系统损伤或功能障碍的背景下建立大脑处理的差异; ii）确定学习诱导的可塑性改善这种变化的负面后果的潜力。在过去的一年里，我们主要关注自闭症谱系障碍（ASD）和截肢的影响，以及建立伴随学习/训练的大脑结构变化。 1)躯体感觉输入丧失（NCT 00623818） 截肢后，超过90%的人报告他们失去的肢体有幻肢感，通常是疼痛感（幻肢痛或PLP）。目前的一种理论认为，PLP是皮层重组的直接结果，是适应不良可塑性的一个例子。镜子疗法已被用作PLP的治疗。在这种治疗过程中，患者在看镜子的同时移动他们完整的肢体，使其看起来好像他们缺失的肢体在移动。我们目前正在研究截肢的神经后果以及镜像治疗对大脑活动的影响。我们继续招募单侧截肢者，并在四周内用功能磁共振成像监测大脑活动，同时截肢者接受镜像治疗。我们正试图确定PLP的存在是否与躯体感觉和运动皮层的皮层重组相关（类似于我们在黄斑变性参与者中观察到的），以及镜像疗法是否通过减少皮层重组的程度而起作用。 2)自闭症谱系障碍（NCT 01031407） 我们一直在研究自闭症谱系障碍（ASD）的运动处理，决策和注意力，这些过程得到了特征良好的大脑网络的支持。 在运动处理的背景下，以前的研究报告了相互矛盾的结果，一些研究发现ASD的运动处理受损，而另一些研究则没有发现损伤。通过改变允许做出判断的时间，我们发现ASD的运动处理受损，但仅在短时间内。此外，这种表现上的缺陷反映在参与视觉运动处理的大脑区域的活动中，与控制参与者相比，自闭症患者的反应减少。 在注意力的背景下，我们要求参与者进行一个简单的视觉辨别，并测量注意力增强的空间梯度。我们发现，自闭症患者的这种梯度比匹配的对照组参与者更明显（Robertson et al，2013，Journal of Neuroscience）。 3)学习/培训（NCT 00001360） 我们正在对学习不同任务（例如运动序列）的参与者进行长期纵向研究，以确定大脑的结构特性如何随时间变化。 确定成人皮质可塑性的性质、程度和后果，为神经系统损伤或功能障碍后的康复性脑治疗提供了重要的见解。

The primary goals of this research are i) to establish differences in brain processing in the context of nervous system damage or dysfunction, and ii) to determine the potential for learning-induced plasticity to ameliorate the negative consequences of such changes. Over the past year we have primarily focused on Autism Spectrum Disorders (ASD) and the impact of amputation, and on establishing the structural brain changes that accompany learning/training. 1) Loss of somatosensory input (NCT00623818) Following limb amputation, over 90% of people report phantom sensations in their missing limb, often painful sensations (Phantom Limb Pain, or PLP). One current theory suggests that PLP is a direct result of cortical reorganization, an example of maladaptive plasticity. Mirror therapy has been used as a treatment for PLP. During this therapy, patients move their intact limb while looking in a mirror, making it seem as if their missing limb is moving. We are currently investigating the neural consequences of amputation and the impact of mirror therapy on brain activity over time. We are continuing to recruit unilateral limb amputees and monitoring brain activity with fMRI over a period of four weeks while the amputees undergo mirror therapy. We are trying to establish whether the presence of PLP correlates with cortical reorganization in the somatosensory and motor cortex (similar to that observed in our participants with macular degeneration) and whether the mirror therapy works by reducing the extent of cortical reorganization. 2) Autism Spectrum Disorders (NCT01031407) We have been investigating motion processing, decision-making and attention in Autism Spectrum Disorders (ASD), processes that are supported by well-characteristic brain networks. In the context of motion processing, previous studies had reported conflicting results with some studies finding impaired motion processing in ASD and other finding no impairment. By varying the time allowed to make judgments, we found that motion processing in ASD is impaired, but only at short durations. Further, this deficit in performance is reflected in the activity of brain regions involved in visual motion processing, with reduced responses in autistic compared with control participants. In the context of attention, we asked participants to perform a simple visual discrimination and measured the spatial gradient of attentional enhancement. We found that this gradient was sharper in autism than in matched control participants (Robertson et al, 2013, Journal of Neuroscience). 3) Learning/training (NCT00001360) We are conducting a long-term longitudinal study of participants learning different tasks (e.g. motor sequences) to determine how structural properties of the brain change over time. Establishing the nature, degree and consequences of plasticity in the adult cortex provides important insights into the potential for rehabilitative brain therapies following injury or dysfunction in the nervous system.