Hackett T A, Stepniewska I, Kaas J H
Department of Psychology, Vanderbilt University, Nashville, TN 37240, USA.
Eur J Neurosci. 1999 Mar;11(3):856-66. doi: 10.1046/j.1460-9568.1999.00492.x.
Auditory cortex of macaque monkeys is located on the lower bank of the lateral sulcus and the adjoining superior temporal gyrus. This region of cortex contains a core of primary-like areas surrounded by a narrow belt of associated fields. Adjacent to the lateral belt on the superior temporal gyrus is a parabelt region which contains at least two subdivisions (rostral and caudal). In previous studies we defined the parabelt region as cortex with topographic cortical connections with the belt areas surrounding the core, and connections with the dorsal and magnocellular divisions of the medial geniculate complex, but minimal connections with the core region and ventral division of the medial geniculate complex. The callosal connections of the parabelt auditory cortex were determined by placing injections, of up to six distinguishable tracers, into different locations of the parabelt region in each of four macaque monkeys. The results indicated that the strongest callosal projections arise from homotopic areas in parabelt cortex, and they roughly matched the rostrocaudal levels of the medial and lateral belt cortex. Weaker callosal inputs to the parabelt originate from the corresponding levels of the superior temporal gyrus and superior temporal sulcus. The core region does not contribute significant callosal projections to the parabelt region. The results provide further support for the conclusion that the parabelt region represents a third level of auditory cortical processing beyond direct activation by primary subcortical and cortical auditory structures.
猕猴的听觉皮层位于外侧沟的下缘和相邻的颞上回。该皮层区域包含一个类似初级区域的核心，周围环绕着一条狭窄的相关区域带。在颞上回上，与外侧带相邻的是一个旁带区域，该区域至少包含两个亚区（吻侧和尾侧）。在之前的研究中，我们将旁带区域定义为与围绕核心的带状区域具有地形学皮层连接，并且与内侧膝状体复合体的背侧和大细胞部分有连接，但与核心区域和内侧膝状体复合体的腹侧部分连接极少的皮层。通过向四只猕猴的每只猕猴的旁带区域的不同位置注射多达六种可区分的示踪剂，确定了旁带听觉皮层的胼胝体连接。结果表明，最强的胼胝体投射来自旁带皮层的同位区域，并且它们大致与内侧和外侧带皮层的前后水平相匹配。对旁带的较弱胼胝体输入来自颞上回和颞上沟的相应水平。核心区域对旁带区域没有显著的胼胝体投射。这些结果为以下结论提供了进一步的支持，即旁带区域代表了除初级皮层下和皮层听觉结构的直接激活之外的听觉皮层处理的第三个层次。
