Cross-modal plasticity of verbal memory in the blind

粗大通道游戏性指的是这样一个概念，即大脑皮层通常对感觉通道作出反应，当其通常的输入被破坏时，变得对来自其他感觉通道的输入做出反应。在盲人受试者中，视觉皮质处理体感和听觉信息。最近的一项功能成像研究发现，言语记忆、回忆和动词生成显著激活了早期失明人类的初级视觉皮质。枕叶激活的程度与随后的词汇记忆和动词生成任务的成绩呈正相关。这些研究提出了一个未经验证的假设，即初级视觉皮质可能是调节早期盲人优秀言语记忆表现的神经底物。我们想用两个实验来检验这一假设。第一个实验(使用功能磁共振成像，fMRI)将在早期和晚期盲人和有视力的对照组中，识别与成功的言语记忆编码和提取以及动词生成相关的大脑皮层区域的激活程度。预期的结果是早期盲人组的视皮层受累增加。在第二个实验中，经颅磁刺激(TMS)对早期失明受试者的言语记忆编码和动词生成有不良影响，但对晚期失明受试者和视力正常的受试者没有影响。TMS实验是必要的，以确定枕叶激活和记忆能力改善之间的因果联系。

Gross-modal playsticity refes to the concept that the cortex normally responsive to ohne sensory modality, when depreived of its usual input, becomes repsonsive to inputs from other sensory modalities. In blind subjects, the visual cortex processes somatosensory and auditory information. A recent functional imaging study foundt that verbal memory recall and verb generation significantly activated the primary visual cortex in early blind humas. The magnitude of occipital activation was positively correlated with subsequent performence on verbal memory and verb generation tasks. These relusts raised the untested hypothesis that the primary visual cortex may be the neural substrate mediating superior verbal memory performance in early blind individuals. We want to test this hypothesis with two experiments. The first experiment (using functional Magnetic Resonance Imaging, fMRI) will identify the magnitude of activation in corical areas associated with successful verbal memory encoding and retrieval, and with verb generation, in early and late blind individuals and sighted controls. The expected outcome is incrased involvement of the visual cortex in the early blind group. In the second experiment, we Transcranial Magnetic Stimulation; TMS) will habe deleterious effects on verbal memory encoding and verb generation in early blind subjecs, but not in late blind subject nor sighted controls. The TMS experiment is necessary to identify a cause-effect link between occipital activation and improved memory performance.