Coordena??o de ritmos sens?rio-motores durante comportamento explorat?rio em ratos

Autor: Alves, Joseph Andrews Belo
Jazyk: portugalština
Rok vydání: 2016
Předmět:
Zdroj: Repositório Institucional da UFRNUniversidade Federal do Rio Grande do NorteUFRN.
Druh dokumentu: masterThesis
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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
Ao explorar ativamente o ambiente, ratos exibem comportamentos sens?rio-motores r?tmicos com frequ?ncia na faixa teta (5-10 Hz). Dentre esses est?o o sniffing (respira??o ativa e r?pida), o whisking (movimento das vibrissas faciais) e as vocaliza??es ultrass?nicas. Estudos recentes mostraram formas de sincronicidades entre tais ritmos: a protra??o e retra??o das vibrissas est?o associadas em fase, respectivamente, ? inala??o e exala??o respirat?ria; a constri??o das cordas vocais necess?ria para a produ??o vocal, por sua vez, est? condicionada ? fase exalante do sniffing e de retra??o do whisking. Embora essas e outras observa??es indiquem uma intera??o entre ritmos e geradores de padr?es no tronco encef?lico aos quais s?o atribu?dos os movimentos orais, faciais e respirat?rios. Com o intuito de adquirir melhor compreens?o acerca das hierarquias concernentes aos circuitos neurais envolvidos em tais atividades, n?s gravamos simultaneamente o whisking, sniffing e as vocaliza??es em ratos durante livre explora??o social. Para este prop?sito, oito eletrodos foram inseridos cirurgicamente para a aquisi??o de sinais eletromiogr?ficos bilaterais dos m?sculos que controlam as vibrissas e uma c?nula foi implantada por meio de uma perfura??o no osso nasal para o registro do ciclo respirat?rio. Ap?s recupera??o e habitua??o, dois ratos (um implantado e outro de est?mulo) foram posicionados sobre duas plataformas separadas por uma fenda onde possibilitava a explora??o m?tua dos animais. Esses epis?dios foram filmados atrav?s de uma c?mera de alta velocidade (250 Hz) para a captura dos movimentos das vibrissas. As vocaliza??es ultrass?nicas foram detectadas por um microfone suspenso. N?s conduzimos an?lises de fase e frequ?ncia para validar os sinais registrados e caracterizar as a??es rec?procas entre esses ciclos em contextos sociais. Os resultados confirmaram que ambos o whisking e o sniffing ocorrem em turnos nas frequ?ncias teta durante explora??o social. Al?m disso, a esperada rela??o em anti-fase entre os sinais dos grupos musculares que controlam a protra??o e retra??o das vibrissas assim como a forte sincronia com o ciclo respirat?rio foram observadas. Interessantemente, nossos dados sugerem que esta sincronia ? imediatamente dissipada durante a emiss?o de vocaliza??es ultrass?nicas. Em vez disso, n?s presenciamos um novo comportamento de whisking, que consiste em retra??o e protra??o ativas e independentes do ciclo respirat?rio.
When actively exploring the environment, rats exhibit several rhythmic behaviors with frequencies in the theta range (5-10 Hz). These include sniffing (active fast respiration), whisking (movement of the facial vibrissae), and ultrasonic vocalizations. Synchronizations between each pair of these behaviors have been observed in recent studies: vibrissae protraction-retraction is linked to the inhalation-exhalation phase of breathing; constriction of the vocal folds for vocalization, in turn, is locked to the exhalation phase of sniffing; accordingly, vocalizations were observed to synchronize with the retraction phase of whisking. These and other observations point to an interaction of rhythm and pattern generators in the brainstem controlling the coordination of respiratory, oral and facial movements. To better understand the hierarchies among these circuits we simultaneously recorded sniffing, whisking and vocalizations from rats during free social exploration. For this purpose, eight electrodes were inserted surgically to acquire bilateral EMG signals from muscles controlling the protraction and retraction of the whiskers and a cannula was implanted through the nasal bone to record the respiratory cycle. After one week of recovery and habituation, two rats (one implanted and one naive) were placed across a gap where they could explore each other. These interactions were filmed with a high speed camera (250 Hz) to capture whisker movements and ultrasonic vocalizations were recorded from an overhanging microphone. We made frequency and phase analysis to validate the recorded signals and characterize the interplay between these sensorimotor rhythms. Results confirmed that both sniffing and whisking occur in bouts at theta frequencies during social exploration. Furthermore, we observed the expected anti-phase relationship between the EMGs from muscles controlling whisker protraction and retraction as well as their tight synchrony with the sniffing cycle. Interestingly, our data suggests that this synchrony is immediately lost during the emission of ultrasonic vocalizations. Instead, we observed a novel whisking behavior, consisting of active vibrissae protraction and retraction independent of the respiratory cycle.
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