Price J L, Slotnick B M
J Comp Neurol. 1983 Mar 20;215(1):63-77. doi: 10.1002/cne.902150106.
A combination of electrophysiological and anatomical techniques was used to determine the sites of termination of olfactory projections to the thalamus and the distribution of the cells of origin of these projections within the olfactory cortex. Following electrical stimulation of the olfactory bulb, short-latency unit responses were recorded not only in the central segment of the mediodorsal thalamic nucleus but also in the ventral and anterior parts of the submedial thalamic nucleus. Responses were not obtained in the ventral or lateral parts of the mediodorsal nucleus, in the dorsal part of the submedial nucleus, or in the intralaminar nuclei between the mediodorsal and submedial nuclei. The cells of origin of the projection were identified by making injections of horseradish peroxidase conjugated to wheat germ agglutinin (HRP WGA) into the thalamus and examining the olfactory cortex for retrogradely labeled cells. Following injections into the mediodorsal nucleus, labeled cells were found in the polymorphic cell zone deep to the olfactory tubercle, in the ventral endopiriform nucleus deep to the piriform cortex, and in an equivalent position deep to the periamygdaloid and lateral entorhinal cortices. After injections into the submedial nucleus, a smaller number of labeled cells were found in similar locations, except that they were restricted to the rostral olfactory cortical areas and were not found deep to the lateral part of the piriform cortex. Retrogradely labeled cells and anterogradely labeled axons were also found in the lateral orbital and ventral agranular insular areas of the prefrontal cortex with injections into the mediodorsal nucleus, and in the ventrolateral orbital area with injections into the submedial nucleus. Anterograde tracing experiments, using the autoradiographic method, have confirmed these results. Injections of 3H-leucine deep to the junction between the anterior piriform cortex and the olfactory tubercle label axons in both the central segment of the mediodorsal nucleus and the ventral part of the submedial nucleus, while injections deep to the posterior piriform cortex label axons in the mediodorsal nucleus only. Within the mediodorsal nucleus, the projection also appears to be organized so that fibers which arise more rostrally terminate ventrolaterally in the central segment, while fibers which arise more caudally terminate more dorsomedially. These results indicate that there is a substantial and possibly dual thalamocortical mechanism available for processing of olfactory stimuli.
采用电生理和解剖学技术相结合的方法，来确定嗅觉投射至丘脑的终止部位，以及这些投射的起源细胞在嗅觉皮质内的分布。在电刺激嗅球后，不仅在丘脑背内侧核的中央段记录到了短潜伏期单位反应，而且在丘脑内侧核的腹侧和前部也记录到了反应。在丘脑背内侧核的腹侧或外侧部、丘脑内侧核的背侧部，以及丘脑背内侧核与丘脑内侧核之间的板内核中均未记录到反应。通过将与小麦胚凝集素结合的辣根过氧化物酶（HRP WGA）注入丘脑，并检查嗅觉皮质中逆行标记的细胞，来确定投射的起源细胞。向丘脑背内侧核注射后，在嗅结节深部的多形细胞区、梨状皮质深部的腹侧内梨状核，以及杏仁周皮质和外侧内嗅皮质深部的相应位置发现了标记细胞。向丘脑内侧核注射后，在类似位置发现的标记细胞数量较少，但它们仅限于嗅皮质的前部区域，在梨状皮质外侧部深部未发现。向丘脑背内侧核注射时，在前额叶皮质的外侧眶区和腹侧无颗粒岛叶区域也发现了逆行标记细胞和顺行标记轴突；向丘脑内侧核注射时，在腹外侧眶区发现了逆行标记细胞和顺行标记轴突。使用放射自显影法的顺行追踪实验证实了这些结果。在前梨状皮质与嗅结节之间的交界处深部注射³H-亮氨酸，可标记丘脑背内侧核中央段和丘脑内侧核腹侧部的轴突，而在后梨状皮质深部注射则仅标记丘脑背内侧核的轴突。在丘脑背内侧核内，投射似乎也是有组织的，使得起源于更靠前部位的纤维在中央段的腹外侧终止，而起源于更靠后部位的纤维在更背内侧终止。这些结果表明，存在一种实质性的、可能是双重的丘脑皮质机制可用于处理嗅觉刺激。
