Hyperemotionality and Enhanced Tonic Immobility after Septal Lesions in the Rabbit

Abstract

Large lesions of the septal region in the rabbit increased tonic immobility as measured by the number of successful inductions and by duration of immobility. Open field activity was also increased. Septally lesioned rabbits also exhibited increased emotionality, although the topography of the ''septal syndrome'' in these rabbits was different from that described for rats. The septally lesioned rabbits exhibited increases in fear reactions such as thumping, escape responses and vocalization when caught, rather than increased aggressiveness. The results are discussed in terms of loss of inhibition of species-typical responses after septal damage.

Tonic immobility as an evolved predator defense: Implications for sexual assault survivors.

“…TI habituates over repeated testing (e.g., Crawford, 1977; Gallup, 1974a; Ratner, 1967), with genetic differences in susceptibility to and duration of TI correlating with strain differences in emotionality and fear (e.g., Erhard & Mendl, 1999; Erhard et al., 1999; Gallup, Ledbetter, & Maser, 1976). Finally, studies examining the neurobiology underlying TI provide evidence for the role of fear in producing and maintaining the response, as various manipulations designed to alter the level of fear, including lesions of the limbic system, particularly septal lesions and lesions of the amygdala (e.g., Brady & Nauta, 1953; Davies et al., 2002; Woodruff & Lippincott, 1976), administration of tranquilizers (e.g., Gallup, Nash, & Brown, 1971; Maser et al., 1974), and administration of fear‐potentiating chemicals such as adrenalin (e.g., Braud & Ginsberg, 1973; Thompson & Jensen, 1979; Thompson & Joseph, 1978; Thompson, Piroch, Fallen, & Hatton, 1973; Thompson, Scuderi, & Boren, 1977) alter susceptibility to and/or duration of the TI response. Collectively, this work shows that actively influencing extent of fear (either up or down) has a substantial effect on TI, either by prolonging or attenuating the response, as well as reducing or increasing the number of inductions necessary to elicit it.…”