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 Pub Med 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.