Nelken Israel, Bizley Jennifer K, Nodal Fernando R, Ahmed Bashir, King Andrew J, Schnupp Jan W H
Department of Neurobiology, Interdisciplinary Center for Neural Computation, The Hebrew University, Jerusalem, Israel.
J Neurophysiol. 2008 Apr;99(4):1928-41. doi: 10.1152/jn.00469.2007. Epub 2008 Feb 13.
We used optical imaging of intrinsic signals to study the large-scale organization of ferret auditory cortex in response to complex sounds. Cortical responses were collected during continuous stimulation by sequences of sounds with varying frequency, period, or interaural level differences. We used a set of stimuli that differ in spectral structure, but have the same periodicity and therefore evoke the same pitch percept (click trains, sinusoidally amplitude modulated tones, and iterated ripple noise). These stimuli failed to reveal a consistent periodotopic map across the auditory fields imaged. Rather, gradients of period sensitivity differed for the different types of periodic stimuli. Binaural interactions were studied both with single contralateral, ipsilateral, and diotic broadband noise bursts and with sequences of broadband noise bursts with varying level presented contralaterally, ipsilaterally, or in opposite phase to both ears. Contralateral responses were generally largest and ipsilateral responses were smallest when using single noise bursts, but the extent of the activated area was large and comparable in all three aural configurations. Modulating the amplitude in counter phase to the two ears generally produced weaker modulation of the optical signals than the modulation produced by the monaural stimuli. These results suggest that binaural interactions seen in cortex are most likely predominantly due to subcortical processing. Thus our optical imaging data do not support the theory that the primary or nonprimary cortical fields imaged are topographically organized to form consistent maps of systematically varying sensitivity either to stimulus pitch or to simple binaural properties of the acoustic stimuli.
我们使用内在信号的光学成像技术来研究雪貂听觉皮层对复杂声音的大规模组织。在连续刺激过程中，通过具有不同频率、周期或耳间水平差异的声音序列来收集皮层反应。我们使用了一组频谱结构不同但具有相同周期性且因此唤起相同音高感知的刺激（点击序列、正弦调幅音和迭代波纹噪声）。这些刺激未能在成像的听觉区域中揭示出一致的周期拓扑图。相反，不同类型的周期性刺激的周期敏感性梯度有所不同。我们使用单耳对侧、同侧和双耳宽带噪声突发以及对侧、同侧或以相反相位呈现给双耳的不同水平宽带噪声突发序列来研究双耳相互作用。使用单个噪声突发时，对侧反应通常最大，同侧反应最小，但在所有三种听觉配置中激活区域的范围都很大且相当。与单耳刺激产生的调制相比，对双耳进行反相幅度调制通常会产生较弱的光信号调制。这些结果表明，在皮层中看到的双耳相互作用很可能主要是由于皮层下处理。因此，我们的光学成像数据不支持这样的理论，即所成像的初级或非初级皮层区域在地形上有组织地形成对刺激音高或声刺激的简单双耳特性的系统变化敏感性的一致图谱。
