Ringo J L
Department of Physiology, University of Rochester Medical School, NY 14642.
Exp Brain Res. 1993;96(3):387-403. doi: 10.1007/BF00234108.
Low-level electrical stimulation through electrodes in the medial temporal lobe (MTL) was used to disrupt the performance of chiasm-split macaques working in a delayed matching-to-sample (DMS) visual memory task. The stimulation was below afterdischarge threshold and did not distract the animals. Nonetheless, stimulation caused severe deficits when delivered either during encoding or retrieval stages. Substantially less deficit appeared when stimulation was delivered during the retention interval. Stimulation levels which led to significant disruption on the DMS task had no effect on a discrimination task using the same kinds of images. Unilateral electrical stimulation delivered to MTL in one hemisphere during encoding and to MTL in the other hemisphere during retrieval produced an effective disruption, suggesting that the unilateral stimulation during the encoding period disrupts the encoding on that side while unilateral stimulation delivered to the opposite side during the retrieval period prevents the retrieval of the (now unilateral) memory. This suggestion is supported by control experiments in which significantly less disruption was caused by unilateral electrical stimulation delivered during both the encoding and the retrieval period if the stimulation was delivered to the same side in both periods. The electrical stimulation was further used to determine that interhemispheric access by one hemisphere to memories placed in the other was excellent. This was done, in these split-chiasm monkeys, by using unilateral stimulation to limit memory formation to just one hemisphere, then testing interhemispheric access by routing the test through the "ignorant" hemisphere (using just the ipsilateral eye). Successful interhemispheric access was obtained with either the anterior commissure or with the splenium of the corpus callosum (the other interhemispheric forebrain pathways having been cut). The electrical stimulation was also used to determine that the visual inputs even though entering via just one eye and one hemisphere, lead to bilateral memory formation. In this case each hemisphere was tested separately during retrieval by delivering disruptive levels of the electrical stimulation to the MTL of the other hemisphere.
通过内侧颞叶（MTL）中的电极进行低水平电刺激，以干扰在延迟匹配样本（DMS）视觉记忆任务中工作的视交叉切开猕猴的表现。刺激低于后放电阈值，且不会分散动物注意力。尽管如此，在编码或检索阶段进行刺激时会导致严重缺陷。在保持间隔期间进行刺激时，缺陷明显减少。导致DMS任务出现显著干扰的刺激水平对使用相同类型图像的辨别任务没有影响。在编码期间对一个半球的MTL进行单侧电刺激，并在检索期间对另一个半球的MTL进行单侧电刺激，会产生有效的干扰，这表明编码期间的单侧刺激会破坏该侧的编码，而在检索期间对另一侧进行单侧刺激会阻止（现在是单侧的）记忆的检索。这一观点得到了对照实验的支持，在对照实验中，如果在编码和检索期间都将单侧电刺激施加到同一侧，则造成的干扰会显著减少。电刺激还被用于确定一个半球对置于另一个半球中的记忆的半球间访问能力良好。在这些视交叉切开的猴子中，通过使用单侧刺激将记忆形成限制在仅一个半球，然后通过“不知情”的半球（仅使用同侧眼睛）进行测试来检验半球间访问。通过前连合或胼胝体压部（其他半球间前脑通路已被切断）都获得了成功的半球间访问。电刺激还被用于确定视觉输入即使仅通过一只眼睛和一个半球进入，也会导致双侧记忆形成。在这种情况下，在检索期间通过向另一个半球的MTL施加干扰水平的电刺激来分别测试每个半球。
