AbstractInteroception is the general sensitivity towards internal bodily signals. Interoceptive responses are crucial for homeostatic control and guide motivational behaviour, through generation of affective feelings, mainly integrated by the insular cortex. Alexithymia, a personality construct characterized by difficulties in identifying such feelings, is implicated in the development and maintenance of alcohol use disorders (AUD). An emergent theory suggests that alexithymia, rather than being a problem with verbal labelling, is the outcome of an interoceptive failure. Interestingly, disruption of interoceptive processes in alcohol-dependent individuals correlates positively with alexithymia and subjective alcohol craving ratings. In this work, I explored the relationship between interoception, alexithymia and alcohol use.
An online survey was designed to characterise the causal relationship between self-assessment of alexithymia, sensitivity to bodily sensations and alcohol consumption, in a normative sample (N=600). A second study involving magnetic resonance spectroscopy measured the neurochemical and structural neural correlates of alcohol use within the insular cortex. A third study objectively measured interoception (interoceptive accuracy) in social drinkers and tested the impact of intranasal oxytocin on accuracy scores. A fourth experiment, involving multiband functional magnetic resonance imaging, tested further the impact of intranasal oxytocin on behavioural and neural correlates of social emotional processing (operationalized as empathy for pain) in alcohol users. Finally, the last experiment quantified dynamic brainbody interactions (via measurement of blood pressure) in alexithymia.
I found that alexithymia and difficulties in identifying feelings mediated the relationship between bodily sensations and alcohol consumption, suggesting that difficulties in identifying feelings might be the outcome of an interoceptive failure, apparently predisposing to AUD. This phenomenon can be explained, in part, by differences in insular glutamatergic neurochemistry and structural integrity associated with alcohol use. At the behavioural level, social alcohol use was not directly associated with impaired interoceptive accuracy. However, intranasal oxytocin improved interoceptive accuracy on the discrimination task compared to placebo in heavy drinkers, but not in low-tomoderate drinkers. This finding suggests reduced flexibility of attentional resource-allocation between internal and external environmental signals, in heavy drinkers. Importantly, this impairment can be corrected by acute intranasal oxytocin. Finally, I found that arousal was associated with better performances. No significant relationship between alexithymia and alcohol intake was observed.
In conclusion, this thesis demonstrates the role that interoception plays in alexithymia and AUD, by considering and integrating behavioural, physiological and neural dimensions. My observations motivate the need to take into account interoceptive processes and (other) regulatory impairments in the treatment of AUD. Therapeutic modulation of interoception can potentially reduce alexithymic features and consequently decrease the likelihood of AUD.
|Date of Award||May 2018|
|Supervisor||Hugo Critchley (Supervisor)|