Modular architectonic organization of the insula in the macaque monkey

Abstract

In order to provide a framework for ongoing analyses of the neuronal connections of the insular cortex of the macaque monkey using modern high-resolution methods, we examined its anatomical organization in serial coronal sections stained alternately with Nissl and Gallyas (myelin) techniques. We observed the same 15 distinct architectonic areas in 10 brains. Within the granular, dysgranular, and agranular regions described in prior studies, we identified 4, 4, and 7 distinct areas, respectively. Across brains, these areas have consistent architectonic characteristics, and in flat map reconstructions they display a consistent topological or neighborhood arrangement, despite variations in the size of individual areas between cases. The borders between areas are generally rather sharply defined. Some areas, in particular the dysgranular areas, appear to consistently contain subtle transitions that suggest possible subareas or modules within the well-delimited areas. The presence of a distinct granular area that straddles the fundus of the superior limiting sulcus over its entire posterior-to-anterior extent is consistent with the available evidence on interoceptive thalamocortical projections, and also with the tensile anchor theory of species-specific cortical gyrification. These observations are consonant with the model of homeostatic afferent processing in the primate insula, and they suggest that discrete modules within insular cortex provide the basis for its polymodal integration of all salient activity relevant to ongoing emotional behavior.

Cytoarchitecture and cortical connections of the anterior insula and adjacent frontal motor fields in the rhesus monkey

“…The cytoarchitecture of this region has been described by Mesulan and Mufson (1982a), Galaberda and Pandya (1983), and more recently by Evrard and colleagues (Evrard et al, 2014). This proisocortex has a simple laminar arrangement that is characterized by an outer and inner stratum (Fig.…”

Brain activity changes in a macaque model of oxaliplatin-induced neuropathic cold hypersensitivity

“…A potential reason why the development of novel analgesics to treat CIPN has been unsuccessful to date, is because the rodent CIPN models have poor clinical predictivity. In terms of brain anatomy and function, including those of the SII/Ins, the macaque shares greater similarities with humans than rodents 17, 41 . Brain activity, as measured by fMRI, in the macaque, combined with behavioral outcomes could be used to further understand the mechanism of oxaliplatin-induced neuropathic pain.…”

“…Thus, the primary objective of the current study is to identify regional brain activity in macaques with oxaliplatin-induced peripheral neuropathy using functional magnetic resonance imaging (fMRI). The macaque has an advantage over other experimental animal species in that brain areas involved in pain processing are similar to that of humans 13–17 . This homology between macaques and humans, in combination with the relatively large brain in macaques, allows for direct comparison of imaging data between macaques and humans.…”

The Insula

“…The dorsal posterior insula is involved in interoceptive awareness (Craig, 2003), and more recently, the anterior insula has also been implicated in this process (Zaki et al, 2012). The overall integration of interoception may involve contributions of “discrete modules” (Evrard et al, 2014) and its integration in complex (e.g., salience-related (Borsook et al, 2013b) circuitry and interpretation of sensory inputs to the posterior insula and integration of autonomic control from the anterior insula. Interoception is likely important in migraine since a migraineur’s physiological internal state is different in ictal and interictal states.…”