猫の聴覚領からおこる投射線維群について

Prolection Fibers from the Auditory Cortex of the Cat

I．はじめに

　猫の聴覚領がSulcus suprasylviusにかこまれた内側の域にあることを，Kornmüller（'37）^12），Woollard ＆ Harpman（'39）^24），Bremer ＆ Dow（'39）^3），Waller（'40）^22）およびAdes（'41）^1）らが明らかにした。ついでこの領域は，Woolsey ＆ Walzl（'42）^25），Rose（'49）^19），Rose ＆ Woolsey（'49）^20），Lilly（'51）^13），Mickle ＆ Ades（'51，'52）^14）15），Hind（'53）^9），Perl ＆ Casby（'54）^17），Butler，Diamond ＆ Neff（'57）^4），Diamond ＆ Neff（'57）^8），Diamond，Chow ＆ Neff（'58）^7）らにより，形態学的および電気生理学的に一層詳細にされ，さらにA_I，A_II，E_pI，E_pII，InsulaおよびA_IIIなどの一層こまかな亜域に区分されるようになった。他方，これまで，この聴覚領からおこる投射線維群についての報告は少なく，とくに上記のように細分された各亜域からおこるものについては，一部の簡単な報告（Whitlock ＆ Nauta '56^23），Desmedt ＆ Mechelse '59）^6）を除き，その大部分が明らかにされていない。

　Eighteen cat brains containing surgical lesions in the auditory cortical area and its neighbouring gyri were studied by use of the Nauta staining technique for degeneration fibers.

　In the auditory cortical area there is more numerous projection fibers than those reported previously. These projection fibers, however, are classified into two fiber systems, the first and the second, by aid of the suprasylvian sulcus which separates the auditory cortical area from the surrounding gyri.

　The first projecting fiber system originating in the inner portion from the suprasylvian sulcus (the auditory cortical area) is composed of several projecting fibers which enter the ipsilateral medial geniculate body, the bilateralinferior colliculi and adlacent gray matters, and the dorsal nucleus of the lateral lemniscusof the lesion side. The connecting relations oft: lose fibers to the auditory cortjcal subdivisions are as follows: the AⅠ area projects massively all fibers belonged to the first fibersystem, whereas the AⅡ area has sparse projections to the medial genjculate body, and theinferior colliculus and adjacent gray matter ofthe homolateral side. The AⅢ area and, insome cases of animals, also E_pH project in anearly same manner as AⅡ has, The E_pI andIn areas, however, have no prolections contained within this first system.

　The second prolecting fiber system takes itsorigin only not in the auditory cortlcal area, but also in the surrounding cortical area. Among fiber groups belonged to this fiber system. The striatal nuclear group terminating in theputamen and caudate nucleus arises from notonly the auditory cortical subdivisions withthe first projecting fiber system, but also thosewithout it. Very spare prolections of the amygdaloid nuclear group, terminating in the lateral amygdaloid nucleus, is originating fromthe AⅢ and AⅡ areas and, though in somecases, also E_pH area. The pontile nuclear gro. up, ending in the pontile nuclei and reticulartegmental nucleus, is arislng from the AⅡ areaand the anterior portion of the AⅠ and AⅡ areas which are located in the ectosylvlan anterior gyrus. The ventro. posterior thalamic nuclear group being distributed to the ventroposterior thalamic, the main sensory nucleusof the trigeminal nerve, the cuneate nucleusand the gracile nucleus is emanating from theAⅢ area. The superior collicular group entering the ventral nuceus of the Iateral genjculate body, the pulvinar and the superficialgray layer of the superior colliculus is star. ting from the E_pI and E_pH, although is not inall cases of animals.