III. Abstract
A fundamental prerequisite for social interaction is the ability to understand the
meaning and intentions of others’ actions. More evidence is emerging to suggest the
presence of shared neural representations of experience in both the first and thirdperson stance. Support has come from the discovery of common neural activity during
both action execution and action observation, namely the mirror neuron system (MNS).
The work in this thesis sought to explore shared neural representations of one’s own
and of others’ actions, rewards and errors along a number of different lines, and how
this could be modulated by different contexts. This was also investigated in terms of
schizophrenia, as patients are known to have deficits in social cognition.
In the first three studies, the EEG mu rhythm suppression was used as an index of mirror
neuron-related motor cortex activity. The first two studies demonstrated,
independently, that greater mu suppression was produced when observing actions that
were relevant to the self, as opposed to the other, and to actions that were rewarding as
opposed to those that were neutral. In the third study, it was shown that patients with
schizophrenia also exhibited a reward-related modulation of the mu suppression during
action observation, and furthermore, that the mu suppression was related to psychotic
negative symptoms and empathy. The fourth study also used EEG to investigate reward
and error-related neural activity, and found that the event-related potentials (ERPs)
associated with one’s own rewards and errors (i.e. the feedback-related negativity and
error-related negativity) also resembled the ERPs associated with others’ rewards and
errors. In addition, an ERP associated with others’ feedback (the P300) was substantially
influenced by expectation. Lastly, a study exploring the relationship between the
prosocial neuropeptide oxytocin and social approach and avoidance behaviour in a
schizophrenia population revealed that individual differences in endogenous oxytocin
levels related to the avoidance of negative emotional stimuli.
In conclusion, it is evident that the internal mental and external environmental context
can shape the interpretation of others’ behaviour, and in particular, the perception of
others’ actions, rewards and errors. These studies suggest that some contextual
modulations of the MNS found in previous studies may have been driven by underlying
influences of self-relevance and reward that were intrinsic to the nature of the perceived
stimuli. This also implies that the emergence and development of the MNS, and the
associated cognitive functions related to shared neural representations of one’s own and
of other’s experience, may also be facilitated by the reward-associations made to other
people’s behaviours, which can also be coloured by the context in which other’s actions
are observed. The influence of reward and self-relevance on the MNS may also have
implications on the development and persistence of social cognitive deficits seen in
schizophrenia. To summarize, a synthesis of these findings is put forward that also aims
to integrate other findings and theoretical frameworks related to learning, perception
and action in the frame of social interaction.