A Role for the Claustrum in Salience Processing?

Abstract

The claustrum (CLA) is a subcortical structure, present only in mammals, whose function remains uncertain. Previously, using resting-state functional magnetic resonance imaging (rs-fMRI) in awake head-fixed rats, we found evidence that the CLA is part of the rodent homolog of the default mode network (DMN; Smith et al., 2017 ). This network emerged as strong functional connections between the medial prefrontal cortex (mPFC), mediodorsal (MD) thalamus, and CLA in the awake state, which was not present following administration of isoflurane anesthesia. In the present report, we review evidence indicating that the rodent CLA also has connections with structures identified in the rodent homolog of the salience network (SN), a circuit that directs attention towards the most relevant stimuli among a multitude of sensory inputs (Seeley et al., 2007 ; Menon and Uddin, 2010 ). In humans, this circuit consists of functional connections between the anterior cingulate cortex (ACC) and a region that encompasses both the CLA and insular cortex. We further go on to review the similarities and differences between the functional and anatomical connections of the CLA and insula in rodents using both rs-fMRI and neuroanatomical tracing, respectively. We analyze in detail the connectivity of the CLA with the cingulate cortex, which is a major node in the SN and has been shown to modulate attention. When considered with other recent behavior and physiology studies, the data reveal a role for the CLA in salience-guided orienting. More specifically, we hypothesize that limbic information from mPFC, MD thalamus, and the basolateral amygdala (BLA) are integrated by the CLA to guide modality-related regions of motor and sensory cortex in directing attention towards relevant (i.e., salient) sensory events.

The Zebrafish Amygdaloid Complex – Functional Ground Plan, Molecular Delineation, and Everted Topology

“…This hypothesis is consistent with embryonic eversion processes as well (Folgueira et al, 2012). During larval and juvenile stages, the eversion gains in complexity through radial migratory processes and the overgrowing of the dorsal pallium by both the DM (putative pallial amygdala) and the MP (Mueller et al, 2008(Mueller et al, , 2011Mueller, 2012).…”

“…In mammals (right side), we find the opposite situation. Here, the amygdaloid complex is located in the anterior ventral depth of the brain covered by the enlarged isocortex (modified after Mueller et al, 2011;Mueller, 2012). For molecular definition of pallial, subpallial, and EmT-derived (EmT-d) amygdaloid territories see Table 1.…”

“…Previous studies showed also that the zebrafish DM is involved in associative learning and endocannabinoid signaling critical for its function (von Trotha et al, 2014;Lau et al, 2011;Ruhl et al, 2015Ruhl et al, , 2017. As a result, the zebrafish amygdala needs to be understood as a mosaic of conserved and acquired characteristics much like other parts of the zebrafish brain (Costagli et al, 2002;Wullimann and Mueller, 2004b;Adolf et al, 2006;Northcutt, 2008;Mueller, 2012).…”

Altered Default Mode Network and Salience Network Functional Connectivity in Patients with Generalized Anxiety Disorders: An ICA‐Based Resting‐State fMRI Study

“…The insular cortex is subsequently used as a “seed region” for an independent component analysis of its functional connectivity patterns. The known functions and modalities processed in these brain regions include attention, sensation, visceral activity, affection, and limbic system, and thus, investigators speculate that this network processes perceptual salience and thus termed it the “salience network” [ 23 ]. The discovery of the SN also reveals an interesting clinical relationship: the strength of functional connectivity within the SN is strongly related to the visual analog scores from a prescan anxiety assessment.…”

“…The discovery of the SN also reveals an interesting clinical relationship: the strength of functional connectivity within the SN is strongly related to the visual analog scores from a prescan anxiety assessment. This correlation suggests a tight link between the strength of the SN and states of vigilance [ 23 ]. These findings are also confirmed by recent studies.…”