Spatial organization of facial vibrissae and cortical barrels in the guinea pig and golden hamster

Abstract

The arrangements of vibrissae in guinea pigs and golden hamsters were previously reported to be different from those in mice and rats. Whereas the mystacial pads in mice and rats include four straddlers and five rows of vibrissae, guinea pigs were described to possess six rows of irregularly aligned mystacial vibrissae and no straddlers, and golden hamsters to include seven vibrissal rows and also no straddlers. We found that all of these four species possess similar vibrissal arrangements within the mystacial pad. To demonstrate this similarity, we developed a new method of sinus hair visualization in flattened and cleared preparations of the mystacial pad. Intrinsic muscles of the mystacial pad that were revealed in thick histological preparations showed clearly the structural and functional relationships between straddlers and vibrissal rows. To verify this finding, and to extend the knowledge of vibrissal cortical representations in guinea pigs and golden hamsters, we have investigated the spatial organization and the functional vibrissal representations of barrels in the posteromedial barrel subfield (PMBSF) of these rodents. The barrel morphology was clearly preserved in Nissl-stained sections and sections processed for cytochrome oxidase of flattened cerebral cortices. We demonstrate that the vibrissal arrangement in the mystacial pad is replicated in the PMBSF of guinea pigs and golden hamsters and that this arrangement is similar to that found in mice and rats. To facilitate comparative studies, these findings strongly recommend the use, in guinea pigs and golden hamsters, of the same classifications and nomenclatures that are used in mice and rats to describe mystacial vibrissae and cortical barrels.

The evolution of active vibrissal sensing in mammals: evidence from vibrissal musculature and function in the marsupial opossumMonodelphis domestica

“…Intrinsic muscles that couple rostral and caudal whiskers within the same row have also been described in mice (Dörfl, 1982), hamsters (Wineski, 1985), guinea pigs (Haidarliu and Ahissar, 1997), rats (Haidarliu et al, 2010) and shrews (Yohro, 1977), lending confidence to the view that this may be a primitive mammalian trait. A new finding in the opossum is the layout of the inverted straddlers in the dorsocaudal area of the pad, and the presence of oblique intrinsic muscles in the two dorsal whisker rows.…”

“…Compared with other mammals in which whisking has been recorded (see Mitchinson et al, 2011), the opossum has relatively few whiskers, indeed far fewer than hamsters (Wineski, 1985;Haidarliu and Ahissar, 1997), rats (Haidarliu et al, 2010), mice (Dörfl, 1982) and shrews (Kulikov, 2011). Amongst rodents, the layout of the guinea pig mystacial pad is perhaps more similar to that of the opossum (Haidarliu and Ahissar, 1997), containing a row of nasal whiskers and only two whiskers in row A.…”

“…In the rat, intrinsic muscles connect the straddler whiskers β to both rows B and C, and γ with both rows C and D (Haidarliu and Ahissar, 1997) (Fig.1F). However, in the opossum, the situation is inverted, as whisker B1 connects to, or 'straddles' the two large caudal whiskers (α and β), such that the dorsal-most part of the B1 intrinsic muscle attaches to the ventral part of α, and the ventralmost part of the B1 intrinsic muscle attaches to the dorsal part of β (Fig.2B,C).…”

“…Amongst rodents, the layout of the guinea pig mystacial pad is perhaps more similar to that of the opossum (Haidarliu and Ahissar, 1997), containing a row of nasal whiskers and only two whiskers in row A.…”

Subcortical barrelette-like and barreloid-like structures in the prosimian galago ( Otolemur garnetti )

“…Details of the reagents used for the immunohistocemisty can be found in Table S1. The skin of the face was removed from four animals, of which three were cleared with xylene to remove skin pigmentation while leaving blood sinuses visible (17). One was stored in 10% (wt/vol) formaldehyde and then processed for hematoxylin and eosin.…”