Medical Research Council Institute of Hearing Research, School of Medicine, University of Nottingham, University Park, Nottingham, UK.
Department of Psychology, American University of Beirut, Riad El-Solh, Beirut, Lebanon.
Cereb Cortex. 2019 Jan 1;29(1):410-428. doi: 10.1093/cercor/bhy267.
It is commonly assumed that the human auditory cortex is organized similarly to that of macaque monkeys, where the primary region, or "core," is elongated parallel to the tonotopic axis (main direction of tonotopic gradients), and subdivided across this axis into up to 3 distinct areas (A1, R, and RT), with separate, mirror-symmetric tonotopic gradients. This assumption, however, has not been tested until now. Here, we used high-resolution ultra-high-field (7 T) magnetic resonance imaging (MRI) to delineate the human core and map tonotopy in 24 individual hemispheres. In each hemisphere, we assessed tonotopic gradients using principled, quantitative analysis methods, and delineated the core using 2 independent (functional and structural) MRI criteria. Our results indicate that, contrary to macaques, the human core is elongated perpendicular rather than parallel to the main tonotopic axis, and that this axis contains no more than 2 mirror-reversed gradients within the core region. Previously suggested homologies between these gradients and areas A1 and R in macaques were not supported. Our findings suggest fundamental differences in auditory cortex organization between humans and macaques.
人们普遍认为，人类听觉皮层的组织类似于猕猴的听觉皮层，其中初级区域（或“核心”）沿音调拓扑轴（音调拓扑梯度的主要方向）拉长，并沿该轴分为多达 3 个不同的区域（A1、R 和 RT），具有独立的、镜像对称的音调拓扑梯度。然而，直到现在，这一假设才得到验证。在这里，我们使用高分辨率超高场（7T）磁共振成像（MRI）来描绘 24 个个体半球中的人类核心并绘制音调图。在每个半球中，我们使用有原则的定量分析方法评估音调梯度，并使用 2 种独立的（功能和结构）MRI 标准来描绘核心。我们的研究结果表明，与猕猴相反，人类核心是垂直于而不是平行于主要音调拓扑轴拉长的，并且该轴在核心区域内不超过 2 个镜像反转的梯度。之前在猕猴中提出的这些梯度与 A1 和 R 区之间的同源性并没有得到支持。我们的研究结果表明，人类和猕猴的听觉皮层组织存在根本差异。
