F. Clasca et al., INSULAR CORTEX AND NEIGHBORING FIELDS IN THE CAT - A REDEFINITION BASED ON CORTICAL MICROARCHITECTURE AND CONNECTIONS WITH THE THALAMUS, Journal of comparative neurology, 384(3), 1997, pp. 456-482
The insular areas of the cerebral cortex in carnivores remain vaguely
defined and fragmentarily characterized. We have examined the cortical
microarchitecture and thalamic connections of the insular region in c
ats, as a part of a broader study aimed to clarify their subdivisions,
functional affiliations, and eventual similarities with other mammals
. We report that cortical areas, which resemble the insular fields of
other mammals, are located in the cat's orbital gyrus and anterior rhi
nal sulcus. Our data suggest four such areas: (a) a ''ventral agranula
r insular area'' in the lower bank of the anterior rhinal sulcus, arch
itectonically transitional between iso- and allocortex and sparsely co
nnected to the thalamus, mainly with midline nuclei; (b) a ''dorsal ag
ranular insular area'' in the upper bank of the anterior rhinal sulcus
, linked to the mediodorsal, ventromedial, parafascicular and midline
nuclei; (c) a ''dysgranular insular area'' in the anteroventral half o
f the orbital gyrus, characterized by its connections with gustatory a
nd viscerosensory portions of the ventroposterior complex and with the
ventrolateral nucleus; and (d) a ''granular insular area'', dorsocaud
al in the orbital gyrus, which is chiefly bound to spinothalamic-recip
ient thalamic nuclei such as the posterior medial and the ventroposter
ior inferior. Three further fields are situated caudally to the insula
r areas. The anterior sylvian gyrus and dorsal lip of the pseudosylvia
n sulcus, which we designate ''anterior sylvian area'', is connected t
o the ventromedial, suprageniculate, and lateralis medialis nuclei. Th
e fundus and ventral bank of the pseudosylvian sulcus, or ''parainsula
r area'', is associated with caudal portions of the medial geniculate
complex. The rostral part of the ventral bank of the anterior ectosylv
ian sulcus, referred to as ''ventral anterior ectosylvian area'', is h
eavily interconnected with the lateral posterior-pulvinar complex and
the ventromedial nucleus. Present results reveal that these areas inte
ract with a wide array of sensory, motor, and limbic thalamic nuclei.
In addition, these data provide a consistent basis for comparisons wit
h cortical fields in other mammals. (C) 1997 Wiley-Liss, Inc.