The hyper-sentient addict: an exteroception model of addiction.

BACKGROUND Exteroception involves processes related to the perception of environmental stimuli important for an organism's ability to adapt to its environment. As such, exteroception plays a critical role in conditioned response. In addiction, behavioral and neuroimaging studies show that the conditioned response to drug-related cues is often associated with alterations in brain regions including the precuneus/posterior cingulate cortex, an important node within the default mode network dedicated to processes such as self-monitoring. OBJECTIVE This review aimed to summarize the growing, but largely fragmented, literature that supports a central role of exteroceptive processes in addiction. METHODS We performed a systematic review of empirical research via PubMed and Google Scholar with keywords including 'addiction', 'exteroception', 'precuneus', and 'self-awareness', to identify human behavioral and neuroimaging studies that report mechanisms of self-awareness in healthy populations, and altered self-awareness processes, specifically exteroception, in addicted populations. RESULTS Results demonstrate that exteroceptive processes play a critical role in conditioned cue response in addiction and serve as targets for interventions such as mindfulness training. Further, a hub of the default mode network, namely, the precuneus, is (i) consistently implicated in exteroceptive processes, and (ii) widely demonstrated to have increased activation and connectivity in addicted populations. CONCLUSION Heightened exteroceptive processes may underlie cue-elicited craving, which in turn may lead to the maintenance and worsening of substance use disorders. An exteroception model of addiction provides a testable framework from which novel targets for interventions can be identified.