Mapping synaptic cortico-claustral connectivity in the mouse

The claustrum is an intriguing brain structure, featuring the highest connectivity per regional volume in the brain. It is a thin and elongated structure enclosed between the striatum and the insular cortex, with widespread reciprocal connections with the sensory modalities and prefrontal cortices. Retinotopic and somatotopic organizations have been described in the claustrum, and anatomical studies in cats, monkeys, and rats have demonstrated topographic organization of cortico-claustral connections. In this study we mapped the projections from cortical modalities (visual, auditory, somatosensory, motor, and olfactory), and prefrontal regions (anterior cingulate cortex and orbitofrontal cortex) to the claustrum in mice. Utilizing expression of a virally encoded synaptic anterograde tracer, AAV-SynaptoTag, followed by 3D reconstruction of the cortical projections, we performed a comprehensive study of the organization of these projections within the mouse claustrum. Our results clearly demonstrate a dorsoventral laminar organization of projections from the sensory cortices to the claustrum, whereas frontal inputs are more extensive and overlap with the inputs from the sensory cortices. In addition, we find evidence supporting a core/shell organization of the claustrum. We propose that the overlap between the frontal inputs and the inputs from the sensory modalities may underlie executive regulation of the communication between the claustrum and the cortical modalities. J. Comp. Neurol. 525:1381 –1402, 2017. © 2016 Wiley Periodicals, Inc.

Mapping synaptic cortico‐claustral connectivity in the mouse

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(20/01/2024, 15:36:10 )

CLA connections: frontal inputs “overlap” with sensory inputs, which might underly executive regulation

“Our results clearly demonstrate a dorsoventral laminar organization of projections from the sensory cortices to the claustrum, whereas frontal inputs are more extensive and overlap with the inputs from the sensory cortices” (Atlan et al., 2017, p. 1381)

“We propose that the overlap between the frontal inputs and the inputs from the sensory modalities may underlie executive regulation of the communication between the claustrum and the cortical modalities” (Atlan et al., 2017, p. 1381)

“Excitation of the different sensory modalities elicits responses in claustral neurons, which typically exhibit a low firing rate in the absence of stimuli

(Segundo and Machne, 1956; Olson and Graybiel, 1980; Sherk and LeVay, 1981b; Remedios et al., 2010)” (Atlan et al., 2017, p. 1381)

CLA segregation Does the claustrum integrate or segregate sensory information

“leaves open the issue of whether claustral neurons integrate or segregate sensory information, a crucial issue for understanding the function of the claustrum” (Atlan et al., 2017, p. 1382)

Low number of CLA visual inputs

“Primary visual inputs, observed in the claustrum of mice Vi#1 and Vi#2, were relatively sparse, exclusively ipsilateral” (Atlan et al., 2017, p. 1387)

CLA organization

“In this study we investigated the organization of cortical inputs to the claustrum in mice” (Atlan et al., 2017, p. 1391)

“1) Inputs to the claustrum display a dorsoventral organization; 2) Inputs to the claustrum display a lateral preference, with visual, auditory and olfactory inputs projecting preferably ipsilaterally, while motor inputs project contralaterally,” (Atlan et al., 2017, p. 1391)

“Hierachy of information processing within” CLA

“This organization suggests the potential for a hierarchy of information processing within the claustrum, where internal and external layers may receive segregated inputs.” (Atlan et al., 2017, p. 1396)

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