Somatosensory brainstem, thalamus, and cortex of the California sea lion (Zalophus californianus). Issue 9 (27th February 2016)

• Record Type: Journal Article
• Authors: Sawyer, Eva K.; Turner, Emily C.; Kaas, Jon H.
• Is Part Of: Journal of comparative neurology. Volume 524:Issue 9(2016)
• Page Start: 1957
• Page End: 1975
• Publication Date: 2016-02-27
• Subjects: sensory system -- touch -- pinniped -- barrelettes -- AB_887876 -- AB_2187552 -- AB_2313581 -- AB_2313606; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.23984
• Languages: English
• ISSNs: 0021-9967

Abstract

ABSTRACT: Pinnipeds (sea lions, seals, and walruses) are notable for many reasons, including their ape‐sized brains, their adaptation to a coastal niche that combines mastery of the sea with strong ties to land, and the remarkable abilities of their trigeminal whisker system. However, little is known about the central nervous system of pinnipeds. Here we report on the somatosensory areas of the nervous system of the California sea lion ( Zalophus californianus) . Using stains for Nissl, cytochrome oxidase, and vesicular glutamate transporters, we investigated the primary somatosensory areas in the brainstem, thalamus, and cortex in one sea lion pup and the external anatomy of the brain in a second pup. We find that the sea lion's impressive array of whiskers is matched by a large trigeminal representation in the brainstem with well‐defined parcellation that resembles the barrelettes found in rodents but scaled upward in size. The dorsal column nuclei are large and distinct. The ventral posterior nucleus of the thalamus has divisions, with a large area for the presumptive head representation. Primary somatosensory cortex is located in the neocortex just anterior to the main vertical fissure, and precisely locating it as we do here is useful for comparing the highly gyrified pinniped cortex with that of other carnivores. To our knowledge this work is the first comprehensive report on the central nervous system areas for any sensory system in a pinniped. The results may be useful both in the veterinary setting and for comparative studies related to brain evolution. J. Comp. Neurol. 524:1957–1975, 2016. © 2016 Wiley Periodicals, Inc. Abstract : We investigated the histochemical and cytoarchitectural anatomy of the somatosensory nuclei in the brainstem and thalamus along with the primary somatosensory cortex in the California sea lion. Organizational features common to the brains of rodents, such as the well‐developed representation of the trigeminal system, can be found in these large carnivores.