Cj. Shi et Md. Cassell, CASCADE PROJECTIONS FROM SOMATOSENSORY CORTEX TO THE RAT BASOLATERAL AMYGDALA VIA THE PARIETAL INSULAR CORTEX, Journal of comparative neurology, 399(4), 1998, pp. 469-491
The pathways by which somatosensory information could be relayed from
the cortex to the amygdaloid complex were investigated by using the an
terograde axonal transport of biocytin following cortical microinjecti
ons. Injections of biocytin into head and limb areas of secondary soma
tosensory cortex (S2) produced heavy labeling of fibers and terminals
in granular and dysgranular parietal insular cortex from bregma to 3.8
mm behind bregma but only extremely sparse labeling in the lateral an
d basolateral amygdaloid nuclei. Biocytin injections into granular par
ietal insular cortex produced a heavy labeling of the subjacent dysgra
nular parietal insular cortex, but only sparse labeling in the basolat
eral amygdala. Biocytin injections into dysgranular parietal insular c
ortex resulted in heavy labeling of the subjacent agranular parietal i
nsular cortex and strong labeling of fibers and terminals in the dorsa
l part of lateral nucleus, with moderate labeling of fibers in the ant
erior and posterior basolateral nuclei, and the central nucleus. Injec
tions into S2 labeled the ventroposterior medial, ventroposterior late
ral and posterior thalamic nuclei; injections in rostral granular and
dysgranular parietal insular cortex labeled the ventral posterior and
parvicellular part of ventroposterior lateral thalamic nuclei; and inj
ections in middle to caudal dysgranular parietal insular cortex labele
d only the posterior nucleus. These results suggest that whereas somat
osensory cortex projects only very sparsely to the amygdala, somatosen
sory-related inputs to the amygdala arise in the dysgranular parietal
insular cortex. The association of dysgranular parietal insular cortex
with the posterior thalamus suggests it may relay nociceptive informa
tion to the amygdala. (C) 1998 Wiley-Liss, Inc.