Can delay-period activity explain working memory?
Can delay-period activity explain working memory?
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延迟期活动可以解释工作记忆吗？
DOI：
10.1152/jn.01002.2003
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发表时间：
2005
影响因子：
2.5
通讯作者：
Ringo,JamesL
中科院分区：
文献类型：
--
作者：
Sobotka,Stanislaw;Diltz,MarkD;Ringo,JamesL
工作记忆任务通常会导致大脑皮层神经元延迟期放电率升高。当这种改变的神经元放电率，称为延迟活动，表现出刺激特异性时，它是工作记忆神经元机制的一个很好的候选者。如果延迟活动确实是记忆的载体，那么在延迟期间干扰延迟活动的实验性操作也应该破坏行为表现。我们在两只猕猴身上验证了这一假设，在这两只猕猴身上，我们只使用了两张视觉图像，并进行了延迟的样本匹配任务(延迟时间：8或10 S)。在每一次试验中，随机选择其中一张图像作为样本。在对照实验中(无干扰刺激)，猴子的正确识别率为74.3%。3种电刺激水平(弱刺激：0.25A-S序列；中刺激：1-S序列；强刺激：4 S)在延迟期给予海马结构或眶-额、眶下皮质，分别使成绩下降到71.4%、66.8和58.0%(均显著低于对照组，P<；0.05为轻度刺激，P<；0.0001为其他刺激水平)。共记录到334个细胞，分别来自颞下皮质和前额叶皮质。(P<；0.05)在记录到的细胞中，约有三分之一的细胞存在明显的刺激特定延迟活动。对于对照试验中的这些细胞，首选和非首选图像之间的延迟期尖峰率的平均差异为26%。在轻度刺激的试验中，电刺激将这一差异降低到20%(P<；0.0005)，在中等刺激的试验中，这一差异减少到14%(P<；0.05)，而在强刺激的试验中，这一差异仅减少到4%(P<；0.05)。这些结果，增加电刺激降低了神经元的选择性，同时降低了行为表现，直接支持延迟活动是延迟期记忆的载体的假说。
Working-memory tasks often lead to elevated delay-period discharge rates in cortical neurons. When this altered neuronal discharge rate, called delay activity, shows stimulus specificity, it is a good candidate for a neuronal mechanism of working memory. If the delay activity is indeed the carrier of memory, then experimental manipulation during the delay period that disrupts delay activity should also disrupt behavioral performance. We tested this hypothesis in two macaque monkeys with a delayed matching-to-sample task (delay time: 8 or 10 s) in which only two visual images were used. In each trial, one of the images was randomly chosen as the sample. In control trials (without disruptive stimulation), the monkeys performed at the level of 74.3% correct recognition. Three electrical stimulation levels (mild: a 0.25-s train of electrical pulses; medium: 1-s train; strong: 4 s), delivered to the hippocampal formation or to the orbito-frontal and inferotemporal cortices during delay period, decreased the performance to 71.4, 66.8, and 58.0% respectively (all are significantly less than control performance,P< 0.05 for mild stimulation andP< 0.0001 for other stimulation levels). Three hundred and thirty-four cells were recorded from inferotemporal (211 cells) and prefrontal (123 cells) cortices. Significant (P< 0.05) stimulus-specific delay activity was found in about one-third of recorded cells. For these cells in control trials, the mean difference in delay-period spike rates between preferred and nonpreferred images was 26%. The electrical stimulation reduced this difference to 20% (not a statistically significant reduction) in trials with mild stimulation, to 14% (P< 0.05) with medium stimulation, and just to 4% (P< 0.0005) with strong stimulation. These results, that increasing electrical stimulation reduced neuronal selectivity and at the same time reduced behavioral performance, directly support the hypothesis that delay activity is the carrier of memory through the delay period.