Brain and Behavior Discovery Institute, Medical College of Georgia, Augusta, Georgia, United States of America.
PLoS One. 2011 Jan 31;6(1):e15342. doi: 10.1371/journal.pone.0015342.
Adult learning-induced sensory cortex plasticity results in enhanced action potential rates in neurons that have the most relevant information for the task, or those that respond strongly to one sensory stimulus but weakly to its comparison stimulus. Current theories suggest this plasticity is caused when target stimulus evoked activity is enhanced by reward signals from neuromodulatory nuclei. Prior work has found evidence suggestive of nonselective enhancement of neural responses, and suppression of responses to task distractors, but the differences in these effects between detection and discrimination have not been directly tested. Using cortical implants, we defined physiological responses in macaque somatosensory cortex during serial, matched, detection and discrimination tasks. Nonselective increases in neural responsiveness were observed during detection learning. Suppression of responses to task distractors was observed during discrimination learning, and this suppression was specific to cortical locations that sampled responses to the task distractor before learning. Changes in receptive field size were measured as the area of skin that had a significant response to a constant magnitude stimulus, and these areal changes paralleled changes in responsiveness. From before detection learning until after discrimination learning, the enduring changes were selective suppression of cortical locations responsive to task distractors, and nonselective enhancement of responsiveness at cortical locations selective for target and control skin sites. A comparison of observations in prior studies with the observed plasticity effects suggests that the non-selective response enhancement and selective suppression suffice to explain known plasticity phenomena in simple spatial tasks. This work suggests that differential responsiveness to task targets and distractors in primary sensory cortex for a simple spatial detection and discrimination task arise from nonselective increases in response over a broad cortical locus that includes the representation of the task target, and selective suppression of responses to the task distractor within this locus.
成人学习诱导的感觉皮层可塑性导致与任务最相关的信息的神经元中动作电位率增强，或者对一种感觉刺激反应强烈但对其比较刺激反应较弱的神经元中动作电位率增强。当前的理论表明，这种可塑性是由来自神经调制核的奖励信号增强目标刺激诱发的活动引起的。先前的工作已经发现了暗示非选择性增强神经反应和抑制对任务干扰的证据，但在检测和区分任务中，这些效应之间的差异尚未直接测试。使用皮质植入物，我们在猕猴感觉皮层中定义了在连续、匹配、检测和区分任务期间的生理反应。在检测学习期间观察到神经反应的非选择性增加。在区分学习期间观察到对任务干扰的反应抑制，这种抑制是特定于在学习之前采样任务干扰的皮质位置的。感受野大小的变化是作为对恒定幅度刺激有显著反应的皮肤区域来测量的，这些区域变化与反应变化平行。从检测学习之前到区分学习之后，持久的变化是对任务干扰有反应的皮质位置的选择性抑制，以及对目标和对照皮肤位置有选择性的皮质位置的反应性的非选择性增强。与之前的研究观察结果进行比较表明，非选择性反应增强和选择性抑制足以解释简单空间任务中的已知可塑性现象。这项工作表明，在简单的空间检测和区分任务中，初级感觉皮层对任务目标和干扰的反应差异来自于对包括任务目标表示的广泛皮质位置的反应的非选择性增加，以及对该位置的任务干扰的反应的选择性抑制。
