Cross-modal plasticity of verbal memory in the blind

粗模态可玩性指的是通常对一种感觉模态有反应的皮层，当其通常的输入被剥夺时，会对来自其他感觉模态的输入产生反应。盲人的视觉皮层处理体感和听觉信息。最近的一项功能成像研究发现，语言记忆、回忆和动词生成显著激活了早期盲人的初级视觉皮层。枕部激活的大小与随后在言语记忆和动词生成任务中的表现呈正相关。这些结果提出了一个未经验证的假设，即初级视觉皮层可能是早期失明个体优越的言语记忆表现的神经基质。我们想用两个实验来验证这个假设。第一个实验（使用功能性磁共振成像，fMRI）将确定在早期和晚期失明个体和视力正常对照中，与成功的言语记忆编码和检索以及动词生成相关的皮质区域的激活程度。预期的结果是在早期失明组中视觉皮层的参与增加。在第二个实验中，我们采用经颅磁刺激；经颅磁刺激（TMS）会对早期失明受试者的言语记忆编码和动词生成产生有害影响，但对晚期失明受试者和视力正常对照组没有影响。颅磁刺激实验是必要的，以确定枕部激活和改善记忆性能之间的因果关系。

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.