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Size Gradients of Barreloids in the Rat Thalamus
 

Summary: Size Gradients of Barreloids
in the Rat Thalamus
SEBASTIAN HAIDARLIU* AND EHUD AHISSAR
Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel
ABSTRACT
The spatial organization of the anatomical structures along the trigeminal afferent
pathway of the rat conserves the topographical order of the receptor sheath: The brainstem
barrelettes, thalamic barreloids, and cortical barrels all reflect the arrangement of whiskers
across the mystacial pad. Although both the amount of innervation in the mystacial pad and
the size of cortical barrels were shown previously to exhibit increasing gradients toward the
ventral and caudal whiskers, whether similar gradients existed in the brainstem and thal-
amus was not known. Here, the authors investigated the size gradients of the barreloids in
the ventral posteromedial nucleus of the rat thalamus. Because the angles used to cut the
brain were crucial to this study, the optimal cutting angles were determined first for
visualization of individual barreloids and of the entire barreloid field. Individual barreloids,
arcs, and rows as well as entire barreloid fields were clearly visualized using cytochrome
oxidase staining of brain slices that were cut with the optimal cutting angles. For the first five
arcs (including straddlers), the length of barreloids increased in the direction of dorsal-to-
ventral whiskers and of caudal-to-rostral whiskers. These gradients reveal an inverse rela-
tionship between the size of barreloids and whiskers (length and follicle diameter) along arcs

  

Source: Ahissar, Ehud - Department of Neurobiology, Weizmann Institute of Science

 

Collections: Biology and Medicine