XB-ART-54731PeerJ January 1, 2018; 6 e4516.
Background: Previous studies have shown that the mammalian thalamus is a key structure for anesthesia-induced unconsciousness and anesthesia-awakening regulation. However, both the dynamic characteristics and probable lateralization of thalamic functioning during anesthesia-awakening regulation are not fully understood, and little is known of the evolutionary basis of the role of the thalamus in anesthesia-awakening regulation. Methods: An amphibian species, the South African clawed frog (Xenopus laevis) was used in the present study. The frogs were immersed in triciane methanesulfonate (MS-222) for general anesthesia. Electroencephalogram (EEG) signals were recorded continuously from both sides of the telencephalon, diencephalon (thalamus) and mesencephalon during the pre-anesthesia stage, administration stage, recovery stage and post-anesthesia stage. EEG data was analyzed including calculation of approximate entropy (ApEn) and permutation entropy (PE). Results: Both ApEn and PE values differed significantly between anesthesia stages, with the highest values occurring during the awakening period and the lowest values during the anesthesia period. There was a significant correlation between the stage durations and ApEn or PE values during anesthesia-awakening cycle primarily for the right diencephalon (right thalamus). ApEn and PE values for females were significantly higher than those for males. Discussion: ApEn and PE measurements are suitable for estimating depth of anesthesia and complexity of amphibian brain activity. The right thalamus appears physiologically positioned to play an important role in anesthesia-awakening regulation in frogs indicating an early evolutionary origin of the role of the thalamus in arousal and consciousness in land vertebrates. Sex differences exist in the neural regulation of general anesthesia in frogs.
PubMed ID: 29576980
PMC ID: PMC5857353
Article link: PeerJ
Article Images: [+] show captions
|Figure 1. Electrode placements and 10 s of typical artifact-free EEG tracings for each channel during Stage I.The intersection of the three dashed lines in the head of X. laevis denotes the lambda (i.e., the vertex where the skull sutures intersect). Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon.|
|Figure 2. The dynamic variations of approximate entropy (ApEn) values (A) and permutation entropy (PE) values (B) for the six brain regions for a randomly selected individual.Note that epochs with artifact were not included. Since the time windows for ApEn (2 s) and PE (10 s) were different, the duration of a given artifact free epoch for the former was shorter than for the latter; thus, the durations of each stage for the former are longer than for the latter. Abbreviations: LT and RT, the left and right telencephalon; LD and RD, the left and right diencephalon; LM and RM, the left and right mesencephalon; I, Stage I (pre-anesthesia stage); II, Stage II (administration stage); III, Stage III (recovery stage); IV, Stage IV (post-anesthesia stage).|
|Figure 3. Correlation analysis between ApEn and the duration of a given stage for the right hemisphere.The correlation between the duration of Stage II and the approximate entropy (ApEn) values of brain structures during Stage I for the right hemisphere (A–C), the correlation between duration of Stage III and the ApEn values of Stage III for the right hemisphere (D–F), and the correlation between the duration of Stage III and the ApEn values of Stage IV for the right hemisphere (G–I).|
|Figure 4. Correlation analysis between PE and the duration of a given stage for the right hemisphere.The correlation between the duration of Stage III and the Permutation entropy (PE) values of brain structures during Stage II for the right hemisphere (A–C), and the correlation between duration of Stage III and the PE values of Stage III for the right hemisphere (D–F).|
References [+] :
Alkire, Toward a unified theory of narcosis: brain imaging evidence for a thalamocortical switch as the neurophysiologic basis of anesthetic-induced unconsciousness. 2000, Pubmed