Freezing behavior
Freezing behavior, also called the freeze response or being petrified, is a reaction to specific
Physiology
Studies suggest that specific areas of the brain are known to either elicit or inhibit (in the case of lesions) freezing behavior in subjects. The regions include the basolateral amygdala and the hippocampus.
One such study, conducted by Ann E. Power et al., investigated the effects of lesions in the basolateral amygdala.
Another study, conducted by Gisquet-Verrier et al., tested the effects of the hippocampus, in three experiments, on both the freezing behavior and avoidance.[3] The rats were lesioned with ibotenic acid, and were tested against a control group. They first investigated changes from conditioned fear, and results showed that lesions to the hippocampus did not alter freezing behavior and marginally affected avoidance. Next, they tested single conditioning sessions, and it was found that freezing behavior remained unchanged while avoidance was disrupted. Finally, they tested conditioning with a larger stimulus (footshock intensity). It was found that avoidance was unaltered while freezing behavior decreased. Not only did these investigations show that the hippocampus is involved with freezing behavior, but avoidance and freezing behavior do not seem to have similar ways of being quantified when it comes to fear conditioning.
Neurotransmitters
It has been experimentally tested that particular areas of the brain are involved with freezing behavior. As mentioned before, Ann E. Power investigated the effect of
- Serotonin[4]
- GABA[5]
- Oxytocin[5]
- Dopamine[5]
- Epinephrine[6]
- Cortisol[7]
- Antipsychotic drugs[8]
- Methamphetamine[9]
- Monoamine oxidase inhibitors[10]
Hashimoto et al. investigated the effects of conditioned fear on serotonin and freezing behavior in rats.[4] Through in vivo microdialysis, certain concentrations of extracellular serotonin in the rat brain were able to be measured. It was found that conditioned fear stress increased the levels of the serotonin in the medial prefrontal cortex. This increase was correlated with an increased freezing behavior that was observed. The rats were then given an inhibitor for the extracellular serotonin, which resulted in a reduced freezing behavior. It can be suggested from these results that inhibition of serotonin can decrease freezing behavior and, also, anxiety.
Not only does serotonin influence freezing behavior, but it has been shown that
Methamphetamine has also been shown to potentially affect freezing behavior.[9] Tsuchiya et al. conducted a study investigating the effect of methamphetamine pretreatment on freezing behavior. Rats were given the drug over a week, ramping up the doses. After that, there was a five-day period without any drugs administered. The rats were then subjected to conditioned fear stress. Repeated but not single methamphetamine pretreatment resulted in a significantly increased freezing behavior. This evidence suggests that previous exposure to chronic methamphetamine results in an increased sensitivity to subsequent stress than a control group.
Just as neurotransmitters influence freezing behavior,
Hormones
It has been shown that parts of the brain are involved in freezing behavior and that neurotransmitters and similar chemicals influence freezing behavior, as well. In a related manner, hormones,
See also
References
- ^ Ressler, K., Emory University Dept. of Psychiatry and Behavioral Sciences (18 Nov 2009). "Lecture".
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