体性感覚野からstriatumおよび前障への投射

PROJECTION TO THE STRIATUM AND THE CLAUSTRUM FROM THE SOMATIC SENSORY CORTEX IN MONKEY

I．はじめに

　大脳皮質運動野とstriatum （尾状核＋被殻）や前障との間の神経線維結合についての報告は比較的多く，相互に明瞭な部位局在が認められるという^13）。他方，体性感覚野とstriatumや前障との間の神経線維結合についての報告はまれではあるものの，同様の部位局在の存在は指摘されている^12,19）。しかし，これらは，おおまかなものであり，主に，策1体性感覚野（SI）を対象としていて，第II体性感覚野（SII）については付随的であるにすぎない。それで本研究では，後者を中心に前頭・頭頂弁蓋皮質からの投射を検討したいと思う。

　ところで，体性感覚野の概念は元来が生理学的なものではあるが，その領域は生理学的，解剖学的に必ずしも諸家で一致しているものではない。そこで，私達は視床後腹側核（VP complex）への投射所見を参照しながら，体性感覚野の細区分野（顔野，躯幹四肢域）からstria—tumや前障などへの投射をFink-Heimer^5）を主に使いしらべた。また対照の意味も兼ねてHRP （horseradishperoxidase）法による逆行性の神経線維結合所見も1例かかげた。

Corticostriatal systems of fibers is said to form one of the major out flows from the cerebral cortex. All areas of the cortex contribute to this pro-jection¹²⁾. In recent years, it has been reported that the rostral and the caudal parts of the cerebral cortex project to the rostral and the caudal parts of the striatum respectively and similarly, the medial and the lateral parts of the cerebral cortex project to the medial and the lateral parts of the striatum respectively. Such a kind of corre-spondence has been called the two dimensional organization¹⁵⁾.

In our experiment, injury was caused to the cerebral cortex of Macaca monkey, which allowing the animals to survive for a certain period of time, was subjected to perfusion and fixation. The degenerative fibers were then stained mainly by the method of Fink-Heimer and its modification to investigate the projection from the somatic sensory cortex to the striatum and the claustrum. The results obtained are as follows:

(1) The two dimensional organization, which was already mentoned above, is not definitely observed in regard to the rostro-caudal dimension particulary concerning to the relation between the operucular cortex and the striatum.

(2) There was projection with topographical arrangement from SII to the putamen.

(3) Similar projection from SI was suggested. Further study in a larger series is needed in this regard.

(4) There was almost no projection from Whitsel's SIIr and SIIc²⁷⁾ to the caudate nucleus, but probably from the adjacent posterior operucular cortex. Limited projection was present, on the other hand, from SI to the caudate nucleus.

(5) Projection from the site corresponding to what was described by Benjamin as the"pure taste area"extended over much the same range⁵⁾ as projection from SII facial area to the putamen.

Such projections were unilateral in nature. Contralateral projection was not evident inasmuch as specimens stained by the silver impregnation method are concerned. The possibility of SII tending to be more dense medially and SI latelally was also suggested, although further study in an increased number of specimens is necessary in this regard.

In the claustrum no distinct somatotopical ar-rangement was observed although there was pro-jection from the above mentioned injury in the cortex to the putamen.