Social buffering ameliorates conditioned fear responses in the presence of an auditory conditioned stimulus

Abstract

Social buffering is a phenomenon in which stress in an animal is ameliorated when the subject is accompanied by a conspecific animal(s) during exposure to distressing stimuli. Previous studies of social buffering of conditioned fear responses in rats have typically used a 3-s auditory conditioned stimulus (CS) as a stressor, observing stress responses during a specified experimental period. Because a 3-s CS is extremely short compared with a typical experimental period, freezing has thus been observed primarily in the absence of the CS. Therefore, it has been unclear whether social buffering ameliorates conditioned fear responses in the presence of the CS. To clarify this issue, the current study assessed the effects of social buffering on conditioned fear responses in the presence of a 20-s CS. We measured the percentage of time spent freezing during the 20-s period following the onset of the CS. When conditioned subjects were exposed to the 20-s CS alone, they exhibited a high percentage of freezing in the presence of the CS. The presence of another non-conditioned rat completely blocked this response. The same result was observed when freezing was observed primarily in the absence of the 3-s CS. In addition, we confirmed that the presence of an associate ameliorated conditioned fear responses induced by a 20-s CS or 3-s CS when the duration and frequency of fear responses was measured. These findings indicate that social buffering ameliorates conditioned fear responses in the presence of an auditory CS.

Keywords: Absence of a CS; Duration of fear responses; Exposure-type social buffering; Percentage of freezing; Presence of a CS.