Lesions of Periaqueductal Gray Dissociate-Conditioned Freezing From Conditioned Suppression Behavior in Rats

Lesion of the ventral periaqueductal gray reduces conditioned fear but does not change freezing induced by stimulation of the dorsal periaqueductal gray.

Previously-reported evidence showed that freezing to a context previously associated with footshock is impaired by lesion of the ventral periaqueductal gray (vPAG). It has also been shown that stepwise increase in the intensity of the electrical stimulation of the dorsal periaqueductal gray (dPAG) produces alertness, then freezing, and finally escape. These aversive responses are mimicked by mi...

Rats’ location during conditioned suppression training

Role of amygdala in conditioned and unconditioned fear generated in the periaqueductal gray.

The amygdala and ventral portion of the periaqueductal gray (vPAG) are crucial for the expression of the contextual freezing behavior. However, it is still unclear whether the amygdala also plays a role in defensive behaviors induced by electrical stimulation of the dorsal periaqueductal gray (dPAG). In the present study, rats were implanted with electrodes into dPAG for determination of the th...

Stimulus modality effects on transformations of conditioned enhancement and conditioned suppression in rats.

Unconditioned and conditioned effects of house-light offset and acoustic white noise on barpressing behavior maintained by intermittent food reinforcement were tested in male hooded rats. Presentations of these stimuli prior to their acquiring signal value initially tended to depress and then to enhance barpressing rate, but generally the rate of the on-going barpressing was lower during the li...

Conditioned respiratory threat in the subdivisions of the human periaqueductal gray

The sensation of breathlessness is the most threatening symptom of respiratory disease. The different subdivisions of the midbrain periaqueductal gray (PAG) are intricately (and differentially) involved in integrating behavioural responses to threat in animals, while the PAG has previously only been considered as a single entity in human research. Here we investigate how these individual PAG co...