Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
Neuroimage. 2010 Jan 1;49(1):150-7. doi: 10.1016/j.neuroimage.2009.07.029. Epub 2009 Jul 22.
The monkey's auditory cortex includes a core region on the supratemporal plane (STP) made up of the tonotopically organized areas A1, R, and RT, together with a surrounding belt and a lateral parabelt region. The functional studies that yielded the tonotopic maps and corroborated the anatomical division into core, belt, and parabelt typically used low-amplitude pure tones that were often restricted to threshold-level intensities. Here we used functional magnetic resonance imaging in awake rhesus monkeys to determine whether, and if so how, the tonotopic maps and the pattern of activation in core, belt, and parabelt are affected by systematic changes in sound intensity. Blood oxygenation level-dependent (BOLD) responses to groups of low- and high-frequency pure tones 3-4 octaves apart were measured at multiple sound intensity levels. The results revealed tonotopic maps in the auditory core that reversed at the putative areal boundaries between A1 and R and between R and RT. Although these reversals of the tonotopic representations were present at all intensity levels, the lateral spread of activation depended on sound amplitude, with increasing recruitment of the adjacent belt areas as the intensities increased. Tonotopic organization along the STP was also evident in frequency-specific deactivation (i.e. "negative BOLD"), an effect that was intensity-specific as well. Regions of positive and negative BOLD were spatially interleaved, possibly reflecting lateral inhibition of high-frequency areas during activation of adjacent low-frequency areas, and vice versa. These results, which demonstrate the strong influence of tonal amplitude on activation levels, identify sound intensity as an important adjunct parameter for mapping the functional architecture of auditory cortex.
猴子的听觉皮层包括颞平面（STP）上的一个核心区域，由具有音调组织的 A1、R 和 RT 区域组成，以及周围的带状区和外侧副带状区。产生音调图并证实解剖学上分为核心、带状区和副带状区的功能研究通常使用低幅度的纯音，这些纯音通常限于阈值强度。在这里，我们使用清醒猕猴的功能磁共振成像来确定音调图以及核心、带状区和副带状区的激活模式是否以及如何受到声音强度的系统变化的影响。在多个声音强度水平下，测量了低频和高频纯音组之间相差 3-4 个八度的血氧水平依赖（BOLD）反应。结果显示，在 A1 和 R 之间以及 R 和 RT 之间的假定区域边界处出现了音调核心的音调图反转。尽管这些音调表示的反转在所有强度水平下都存在，但激活的侧向扩散取决于声音幅度，随着强度的增加，相邻带状区的招募增加。STP 上的音调组织也在频率特异性去激活（即“负 BOLD”）中显现出来，这种效应也是强度特异性的。正 BOLD 和负 BOLD 的区域空间交织在一起，可能反映了高频区在相邻低频区激活期间的侧向抑制，反之亦然。这些结果表明音调幅度对激活水平有强烈影响，确定声音强度是映射听觉皮层功能结构的重要附加参数。
