Preferential arborization of dendrites and axons of parvalbumin- and somatostatin-positive GABAergic neurons within subregions of the mouse claustrum

概要

The claustrum is a thin subcortical nucleus located between the insular cortex and the
striatum. This small nucleus has abundant reciprocal excitatory connections with almost the entire
cerebral cortex (Atlan et al., 2017; Wang et al., 2017; Zingg et al., 2018; Marriott et al., 2021;
Shelton et al., 2022; Wang et al., 2022) and coordinates activity in the individual cortices (Crick
and Koch, 2005; Smythies et al., 2012). Indeed, claustral neurons synchronously regulate cortical
activity during slow-wave sleep in mice (Narikiyo et al., 2020) and reptiles (Norimoto et al., 2020).
The excitatory connections between the claustrum and each cortical area have been further
demonstrated to play key roles in various physiological functions (Goll et al., 2015; Chia et al.,
2020), such as salience detection, attention, and regulation of impulsivity with claustrofrontocortical connections (White et al., 2018; Liu et al., 2019; Chia et al., 2020; Terem et al.,
2020; Atlan et al., 2021); contextual memory with claustro-medial entorhinal cortical connections
(Kitanishi and Matsuo, 2017); and motor response related to selection tasks with claustrosomatosensory cortical connections (Chevee et al., 2022).
The claustrum has been divided into three subregions by chemoarchitecture and
cytoarchitecture (Binks et al., 2019). Parvalbumin (PV) immunoreactivity is higher in the central
area of the claustrum—the core region—than in the surrounding area (Real et al., 2003; Davila et
al., 2005), while the surroundings—the shell region—selectively display strong immunoreactivity
for vesicular glutamate transporter 2 (VGluT2) (Real et al., 2006). Further, the central part of the
claustrum shows a high density of neurons (Obst-Pernberg et al., 2001) and appears to correspond
to the core region (Real et al., 2003). In addition, the shell region can be subdivided into ventral
and dorsal parts by the extended boundary line between the dysgranular and agranular insular
cortex (DI and AI) (Johnson et al., 2014; Binks et al., 2019). Although immunoreactivity for
neuronal nuclei (NeuN) has been used to identify the claustrum (Kitanishi and Matsuo, 2017), the
consistency of the core and shell subregional delineation based on PV and/or VGluT2
immunoreactivity (chemoarchitecture) and that based on cytoarchitecture is undetermined.
These three subregions—core region and dorsal and ventral shell regions—have distinct
reciprocal connections with each cortical area. Anterograde and retrograde tracing studies have
demonstrated reciprocal connections between the claustral subregions and cerebral cortex:
claustral glutamatergic neurons in the core region send outputs to and receive inputs from the
retrosplenial and visual cortices; those in the dorsal shell region connect with the motor and
somatosensory cortices; and those in the ventral shell region have connections with the entorhinal
cortex (Atlan et al., 2017; Marriott et al., 2021; Ham and Augustine, 2022; Shelton et al., 2022).
This topographical organization suggests that the subregional structures would serve as functional
modules via excitatory connections with the cerebral cortex (Chia et al., 2020; Smith et al., 2020;
Marriott et al., 2021; Ham and Augustine, 2022). ...

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