An MRI protocol for anatomical and functional evaluation of the California sea lion brain

Abstract

We describe a research MRI protocol for ​in vivo​ evaluation of pinniped brains using standard human clinical MRI hardware and pulse sequences. Our intended application is to study development of California sea lions (​Zalophus californianus​) exposed ​in utero​ to domoic acid (DOM) produced by harmful algae blooms in the coastal Pacific Ocean. In cases where the fetus survives to birth, exposure to the toxin ​in utero​ could result in developmental abnormalities leading to neurological and behavioral deficits. Prior studies on sea lions naturally exposed to DOM as adults have demonstrated hippocampal atrophy and altered mesial temporal connectivity. This MRI protocol is therefore intended to depict the hippocampal formation as the primary region of interest, and to provide longitudinal measures of brain functional and structural connectivity as well as quantitative anatomical evaluations. Scan quality and utility are assessed by comparison with prior studies in live and post mortem sea lion brains. We include the first determination of cerebral blood flow mapping using MRI, and also the first fiber tractography using diffusion-weighted imaging from a live sea lion brain. The protocol also facilitates screening for common neurological pathologies, including tumors, trauma and hemorrhages. We believe the protocol would be suitable for any pinniped that can fit inside a human MRI scanner.

Vocal learning as a preadaptation for the evolution of human beat perception and synchronization

“…Furthermore, related to a point made by Schachner [102], the intensive operant training Ronan received in synchronizing movements to sounds (first with metronomes, later with music), combined with the heightened plasticity of juvenile mammalian brains [103], raises the question of whether Ronan developed unusually strong auditory–motor forebrain circuitry compared to normal sea lions. This could be addressed via structural brain imaging of auditory–motor forebrain connections in Ronan compared to conspecifics without early auditory–motor training, using recently developed in vivo magnetic resonance imaging (MRI) protocols for sea lions [104].…”

Xenotransplantation of porcine progenitor cells in an epileptic California sea lion (Zalophus californianus): illustrative case

“…15 A recent demonstration that porcine embryonic MGE progenitors migrate and differentiate into GABA-expressing interneurons in a manner similar to that described for murine embryonic MGE progenitors used for cell transplantation therapy 10 established this porcine cell source as a viable candidate for treating larger animals. Because California sea lions with DA toxicosis represent a well-characterized example of acquired epilepsy in wildlife, and because prior studies described unilateral hippocampal atrophy with loss of inhibitory hippocampal interneurons in some of these animals, 6,16 it is not entirely surprising that successful MGE-based treatment of a sea lion mimics prior mouse studies.…”

Xenotransplantation of porcine progenitor cells in an epileptic California sea lion (Zalophus californianus)

“…Because California sea lions with DA toxicosis represent a wellcharacterized example of acquired epilepsy in wildlife 5 , and prior studies describe unilateral hippocampal atrophy with loss of inhibitory hippocampal interneurons in some of these animals 7,16 it is not entirely surprising that successful MGE-based treatment of a sea lion mimics prior mouse studies.…”