Empathy Is Moderated by Genetic Background in Mice

Abstract

Empathy, as originally defined, refers to an emotional experience that is shared among individuals. When discomfort or alarm is detected in another, a variety of behavioral responses can follow, including greater levels of nurturing, consolation or increased vigilance towards a threat. Moreover, changes in systemic physiology often accompany the recognition of distressed states in others. Employing a mouse model of cue-conditioned fear, we asked whether exposure to conspecific distress influences how a mouse subsequently responds to environmental cues that predict this distress. We found that mice are responsive to environmental cues that predict social distress, that their heart rate changes when distress vocalizations are emitted from conspecifics, and that genetic background substantially influences the magnitude of these responses. Specifically, during a series of pre-exposure sessions, repeated experiences of object mice that were exposed to a tone-shock (CS-UCS) contingency resulted in heart rate deceleration in subjects from the gregarious C57BL/6J (B6) strain, but not in subjects from the less social BALB/cJ (BALB) strain. Following the pre-exposure sessions, subjects were individually presented with the CS-only for 5 consecutive trials followed by 5 consecutive pairings of the CS with the UCS. Pre-exposure to object distress increased the freezing responses of B6 mice, but not BALB mice, on both the CS-only and the CS-UCS trials. These physiological and behavioral responses of B6 mice to social distress parallel features of human empathy. Our paradigm thus has construct and face validity with contemporary views of empathy, and provides unequivocal evidence for a genetic contribution to the expression of empathic behavior.

Observation of Distressed Conspecific as a Model of Emotional Trauma Generates Silent Synapses in the Prefrontal-Amygdala Pathway and Enhances Fear Learning, but Ketamine Abolishes those Effects

“…Previous studies have shown that exposure to distressed conspecific in rodents acts as unconditional stimulus (US) in both contextual and cued fear conditioning (Chen et al, 2009;Jeon et al, 2010;Yusufishaq and Rosenkranz, 2013) and enhances active avoidance learning performed in a different context immediately after the exposure (Knapska et al, 2010). Here we found enhanced PA learning 24 h after OF, which implies lasting modifications of the fear learning circuits.…”

“…Such exposures interrupt ongoing activities (Church, 1959), increase depression and anxiety-like behaviors (Warren et al, 2013), and elicit fear learning (Chen et al, 2009;Jeon et al, 2010;Yusufishaq and Rosenkranz, 2013). Emotionally salient stimuli generally recruit the dorsomedial prefrontal cortex (dmPFC) and the basolateral amygdala (BLA), which have strong reciprocal projections (Hubner et al, 2014;McDonald, 1998) and are involved in fear learning (Gilmartin et al, 2014;Marek et al, 2013;Senn et al, 2014), including contextual learning during observational fear (Amano et al, 2010;Jeon et al, 2010).…”

Prosocial primates: selfish and unselfish motivations

“…Probably, this mechanism is a mammalian universal, given that part of its assumed neural underpinnings were first discovered in macaques (e.g. mirror neurons; Rizzolatti et al 1996) and that emotional contagion (often considered the starting point of empathy) is increasingly studied in rodents (Langford et al 2006;Chen et al 2009;Grenier & Lü thi 2010). Mirroring mechanisms permit one individual to resonate with the emotional state of another, thus priming this individual for actions appropriate to the other's state, such as when a mother is distressed at hearing the distress calls of her young resulting in comforting behaviour (Panksepp 1996).…”

Towards Artificial Empathy

“…An example is an experiment with mice where one mouse (temporally called "A") observes another mouse receiving an electric shock accompanied by a tone. Eventually, A freezes in response to the tone even though A has never experienced the shock [8]. Here, A's freezing behavior is triggered by its emotional reaction and might be interpreted as a sign of emotional contagion.…”