Department of Psychology, University of Iowa, Iowa City, Iowa 52242, USA.
J Neurosci. 2012 May 16;32(20):6841-50. doi: 10.1523/JNEUROSCI.0284-12.2012.
Eyeblink conditioning (EBC) was used in the current study to examine the mechanisms underlying the ontogeny of associative motor learning in rats. Eyeblink conditioning emerges ontogenetically between postnatal day 17 (P17) and P24 in rats. Previous studies used electrical stimulation to show that the ontogeny of EBC is influenced by developmental changes in input from the medial auditory thalamus to the pontine nuclei, which in turn affects input to the cerebellum. The current study used tetrode recordings to examine the ontogeny of medial auditory thalamic sensory responses to the conditioned stimulus (CS) and learning-related activity during EBC. Rat pups were implanted with multiple tetrodes in the medial nucleus of the medial geniculate (MGm) and suprageniculate (SG) and trained on delay EBC on P17-P19, P24-P26, or P31-P33 while recording spike activity. Developmental changes in MGm and SG sensory-related activity were found during a pretraining session with unpaired presentations of the auditory CS and periorbital stimulation unconditioned stimulus (US). Substantial developmental changes were observed in learning-related activity in the MGm and SG during CS-US paired training. The ontogenetic changes in learning-related activity may be related to developmental changes in input to the medial auditory thalamus from the amygdala and cerebellum. The findings suggest that the ontogeny of associative motor learning involves developmental changes in sensory input to the thalamus, amygdala input to the thalamus, thalamic input to the pontine nuclei, and cerebellar feedback to the thalamus.
眨眼条件反射（EBC）被用于当前研究中，以考察大鼠联想性运动学习的个体发生机制。在大鼠中，眨眼条件反射在出生后第 17 天（P17）到 P24 之间出现个体发生。先前的研究使用电刺激表明，眨眼条件反射的个体发生受从中耳内侧丘系到脑桥核的输入的发育变化的影响，这反过来又影响到小脑的输入。当前的研究使用四极管记录来研究内侧听觉丘脑对条件刺激（CS）的感觉反应以及眨眼条件反射期间的学习相关活动的个体发生。在 P17-P19、P24-P26 或 P31-P33 期间，在接受延迟眨眼条件反射训练的同时，在内侧膝状体（MGm）和上膝状体（SG）的内侧核中植入多个四极管，并记录尖峰活动。在未配对呈现听觉 CS 和眶周刺激非条件刺激（US）的预训练期间，发现 MGm 和 SG 的感觉相关活动发生了发育变化。在 CS-US 配对训练期间，在 MGm 和 SG 中观察到学习相关活动的大量发育变化。学习相关活动的个体发生变化可能与杏仁核和小脑向内侧听觉丘脑的输入的发育变化有关。研究结果表明，联想性运动学习的个体发生涉及到丘脑的感觉输入、杏仁核向丘脑的输入、丘脑向脑桥核的输入以及小脑向丘脑的反馈的发育变化。
