Comparative Development of Somatic Sensory Cortex

Johnson, John Irwin

doi:10.1007/978-1-4615-3824-0_6

Cited by 80 publications

(83 citation statements)

References 242 publications

(419 reference statements)

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“…The position of the posterior-lateral somatosensory region described here is similar to the parietal ventral (PV) area that has been described in a variety of mammals (Disbrow et al 2000;Johnson 1990;Krubitzer et al 1986). In line with a homology of the posterior-lateral somatosensory region and PV, electrophysiological analysis in rats demonstrated polysensory responses in this cortical region (Menzel and Barth 2005).…”

Section: Comparative Considerationssupporting

confidence: 67%

Cortical Organization in the Etruscan Shrew (Suncus etruscus)

Roth-Alpermann

Anjum

Naumann

et al. 2010

Journal of Neurophysiology

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Cortical organization in the Etruscan shrew is of comparative interest because of its small size and because the Etruscan shrew is an amazing tactile hunter. Here we investigated cortical organization in Etruscan shrews by electrophysiological mapping. We developed an anesthesia protocol for this very small mammal in which we combined massive application of local anesthesia, very slow induction of general anesthesia, and passive cooling. Under this anesthesia regime, we characterized auditory, visual, and somatosensory cortical responses. We found that large parts of shrew cortex respond to such stimuli. Of the responsive sites, a small fraction (∼14%) responded to visual stimuli in a caudally located region. Another small fraction of sites (∼11%) responded to auditory stimuli in a centrally located region. The majority of sites (∼75%) responded to tactile stimuli. We identified two topographically organized somatosensory areas with small receptive fields referred to as putative primary somatosensory cortex and putative secondary somatosensory cortex. In a posterior-lateral region that partially overlaps with piriform cortex, we observed large somatosensory receptive fields and often polysensory responses. In an anterior-lateral region that partially overlaps with piriform cortex, we observed large unimodal somatosensory receptive fields. Our findings demonstrate a remarkable degree of tactile specialization in Etruscan shrew cortex.

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Section: Comparative Considerationssupporting

confidence: 67%

Cortical Organization in the Etruscan Shrew (Suncus etruscus)

Roth-Alpermann

Anjum

Naumann

et al. 2010

Journal of Neurophysiology

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“…The orientation of S1 is similar to that described for a range of other placental mammals that have a similar body plan (Fig. 6) (Kaas, 1983(Kaas, , 1993Johnson, 1990;Krubitzer et al, 1993;Krubitzer, 1995). However, S1 is located in a relatively rostral location, supporting the suggestion from our recordings that a large amount of cortex is devoted to processing visual inputs.…”

Section: Discussionsupporting

confidence: 87%

Organization of the somatosensory cortex in elephant shrews (E. edwardii)

2006

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The superorder Afrotheria consists of a diverse group of mammals, including elephants, hyraxes, dugongs, sea cows, aardvarks, tenrecs, golden moles, and elephant shrews. Recent studies suggest this clade diverged from other placental mammals 100 million years ago and thus may represent the sister group to the remaining placental mammals. Despite this important taxonomic position, relatively few studies have investigated cortical organization in these species. Here we present results of an investigation of the somatosensory cortex in the Cape elephant shrew (Elephantulus edwardii). Using multiunit electrophysiological recording techniques, we identified a topographic map of the elephant shrew's body in a location and orientation consistent with the primary somatosensory cortex (S1). The elephant shrew's elongated snout, extensive facial vibrissae, and long tongue accounted for a large portion of the somatosensory representation, located in a relatively rostral area of cortex. Evidence for an additional somatosensory area, presumed to be secondary somatosensory cortex (S2), was found just lateral to S1. Visual and auditory responsive areas were also identified and the extent of visual cortex appeared to be quite large in these highly visual mammals. Despite the elephant shrew's exceptionally well-developed eyes, ears, and vibrissae, there were no anatomical correlates to sensory areas, or body part representations (e.g., barrels), that could be identified in the flatted cortex. Anat Rec Part 288A: 859-866, 2006. 2006

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“…Our analysis of sensorimotor cortex can be expanded with data from other clades (Monotremes) (Krubitzer et al, 1995) and more species (Johnson, 1990), but the basic conclusions remain unchanged. Early mammals had small brains with little neocortex.…”

Section: Early Mammalsmentioning

confidence: 99%

Evolution of somatosensory and motor cortex in primates

2004

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Inferences about how the complex somatosensory systems of anthropoid primates evolved are based on comparative studies of such systems in extant mammals. Experimental studies of members of the major clades of extant mammals suggest that somatosensory cortex of early mammals consisted of only a few areas, including a primary area, S1, bordered by strip-like rostral and caudal somatosensory fields, SR and SC. In addition, the second somatosensory area, S2, and the parietal ventral area, PV, were probably present. S1, S2, and PV were activated independently via parallel projections from the ventroposterior nucleus, VP. Little posterior parietal cortex existed, and it was unlikely that a separate primary motor area, M1, existed until placental mammals evolved. Early primates retained this basic organization and also had a larger posterior parietal region that mediated sensorimotor functions via connections with motor and premotor areas. The frontal cortex included M1, dorsal and ventral premotor areas, supplementary motor area, and cingulate motor fields. Ventroposterior superior and ventroposterior inferior nuclei were distinct from the ventroposterior nucleus in the thalamus. In early anthropoid primates, areas S1, SR, and SC had differentiated into the fields now recognized as areas 3b, 3a, and 1. Areas 3b and 1 contained parallel mirror-image representations of cutaneous receptors and a parallel representation in area 2 was probable. Serial processing became dominant, so that neurons in areas 1, S2, and PV became dependent on area 3b for activation. Posterior parietal cortex expanded into more areas that related to frontal cortex. Less is known about changes that might have occurred with the emergence of apes and humans, but their brains were larger and posed scaling problems most likely solved by increasing the number of cortical areas and reducing the proportion of long connections. © 2004 Wiley-Liss, Inc. Key words: galago; premotor; sensorimotor; tarsier; thalamus; ventroposterior nucleusHumans have exceptional sensorimotor skills that appear to be unique in the extent to which they can be individualized and specialized by experience and training. We commonly observe remarkable skills as we view highly trained athletes and musicians, and there are many examples from other activities as well. Such performances stand in contrast to the simple and sometimes clumsy sensorimotor behavior of opossums and laboratory rats. However, vast differences in abilities are to be expected if we consider the differences in the sensorimotor systems of various mammals.The first premise of this review is that early mammals had small brains in proportion to body size, and these brains contained rather simple sensorimotor systems. Furthermore, these simple sensorimotor systems have been retained with little modification in a range of distantly related extant mammals. By using the methods of modern neuroscience to study the sensorimotor systems of these mammals, together with a cladistic character anal-*Correspondence to:

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Comparative Development of Somatic Sensory Cortex

Cited by 80 publications

References 242 publications

Cortical Organization in the Etruscan Shrew (Suncus etruscus)

Cortical Organization in the Etruscan Shrew (Suncus etruscus)

Organization of the somatosensory cortex in elephant shrews (E. edwardii)

Evolution of somatosensory and motor cortex in primates

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