Mrsic-Flogel Thomas D, Versnel Huib, King Andrew J
University Laboratory of Physiology, Parks Road, Oxford OX1 3PT, UK.
Eur J Neurosci. 2006 Feb;23(3):780-92. doi: 10.1111/j.1460-9568.2006.04609.x.
Little is known about the maturation of functional maps in the primary auditory cortex (A1) after the onset of sensory experience. We used intrinsic signal imaging to examine the development of the tonotopic organization of ferret A1 with respect to contralateral and ipsilateral tone stimulation. Sound-evoked responses were recorded as early as postnatal day (P) 33, a few days after hearing onset. From P36 onwards, pure tone stimuli evoked restricted, tonotopically organized patches of activity. There was an age-dependent increase in the cortical area representing each octave, with a disproportionate expansion of cortical territory representing frequencies > 4 kHz after P60. Similar tonotopic maps were observed following stimulation of the contralateral and ipsilateral ears. During the first few weeks following hearing onset, no differences were found in the area of cortical activation or in the magnitude of the optical responses evoked by stimulation of each ear. In older animals, however, contralateral stimuli evoked stronger responses and activated a larger A1 area than ipsilateral stimuli. Our findings indicate that neither the tonotopic organization nor the representation of inputs from each ear reach maturity until approximately 1 month after hearing onset. These results have important implications for cortical signal processing in juvenile animals.
关于感觉经验开始后初级听觉皮层（A1）中功能图谱的成熟情况，人们了解甚少。我们使用内在信号成像技术来研究雪貂A1在对侧和同侧音调刺激下的音调组织发育情况。早在出生后第33天（P33），即听力开始几天后，就记录到了声音诱发反应。从P36开始，纯音刺激诱发了受限的、按音调组织的活动斑块。代表每个八度的皮层区域随年龄增长而增加，在P60之后，代表频率>4 kHz的皮层区域有不成比例的扩展。在对侧和同侧耳朵受到刺激后，观察到了类似的音调图谱。在听力开始后的最初几周内，未发现皮层激活区域或每只耳朵刺激诱发的光学反应大小存在差异。然而，在年龄较大的动物中，对侧刺激诱发的反应更强，并且比同侧刺激激活的A1区域更大。我们的研究结果表明，直到听力开始后约1个月，音调组织和每只耳朵输入的表征才达到成熟。这些结果对幼年动物的皮层信号处理具有重要意义。
