The claustrum of the ferret: afferent and efferent connections to lower and higher order visual cortical areas

Nina Patzke,Giorgio M Innocenti,Paul R Manger

doi:10.3389/fnsys.2014.00031

Abstract

The claustrum, a subcortical telencephalic structure, is known to be reciprocally interconnected to almost all cortical regions; however, a systematic analysis of claustrocortical connectivity with physiologically identified lower and higher order visual cortical areas has not been undertaken. In the current study we used biotinylated dextran amine to trace the connections of the ferret claustrum with lower (occipital areas 17, 18, 19 and 21) and higher (parietal and temporal areas posterior parietal caudal visual area (PPc), posterior parietal rostral visual area (PPr), 20a, 20b, anterior ectosylvian visual area (AEV)) order visual cortical areas. No connections between the claustrum and area 17 were observed. Occipital visual areas 18, 19 and 21 revealed a reciprocal connectivity mainly to the caudal part of the claustrum. After injection into parietal areas PPc and PPr labeled neurons and terminals were found throughout almost the entire rostrocaudal extent of the dorsal claustrum. Area 20b revealed reciprocal connections mainly to the caudal-ventral claustrum, although some labeled neurons and terminals were observed in the dorso-central claustrum. No projection from the claustrum to areas AEV and 20a could be observed, though projections from AEV and 20a to the claustrum were found. Only injections placed in areas PPr and AEV resulted in anterogradely labeled terminals in the contralateral claustrum. Our results suggest that lower order visual areas have clearly defined connectivity zones located in the caudal claustrum, whereas higher order visual areas, even if not sending and/or receiving projections from the entire claustrum, show a more widespread connectivity.

Highlights

The claustrum is a thin subcortical unlaminated telencephalic structure located between the dorsal striatopallidal complex, the putamen, and the insular cortex, or claustrocortex in mammals that lack the insular formation and a sylvian fissure
As a control we examined the potential connections with the dorsal lateral geniculate nucleus and observed labeled cells (Figure 3A)
SUMMARY With the exceptions of areas AEV and 20a, all visual areas that we analyzed appear to be reciprocally connected with the ipsilateral claustrum and the highest density of retrogradely labeled cells were found in the caudal third of the claustrum

Summary

Introduction

The claustrum is a thin subcortical unlaminated telencephalic structure located between the dorsal striatopallidal complex, the putamen, and the insular cortex, or claustrocortex in mammals that lack the insular formation and a sylvian fissure. Various anatomical tract-tracing experiments, mostly in cats and monkeys, and in other species, have demonstrated that the claustrum is reciprocally interconnected to almost all cortical regions. Those cortical regions for which claustrocortical connectivity has been observed include: visual cortex, parieto-occipital and posterior parietal cortex, temporal and temporopolar cortex, motor and premotor cortex, prefrontal cortex, cingulate cortex, the frontoparietal operculum, somatosensory cortex, prepiriform olfactory cortex and the entorhinal cortex (for details see TannéGariépy et al, 2002; Edelstein and Denaro, 2004; Crick and Koch, 2005). Tractographic anatomical studies in humans have demonstrated claustral projections to the superior frontal, precentral, postcentral, posterior parietal, orbitofrontal, prefrontal, temporal and occipital cortical regions (Fernández-Miranda et al, 2008)

Methods

Results

Discussion

Conclusion