Neurochemical correlates of mind-wandering and meta-awareness

Mind-wandering is a frequent occurrence in daily life, diverting attention away from both goal-oriented behaviour and internal mental operations. The experience of mind-wandering varies both in the degree to which an individual is aware of their attentional state (meta-awareness) and in their intention to mind-wander. Prior research links mind-wandering with the brain's default mode network. However, the association between mind-wandering and the concentration of excitatory (glutamate) and inhibitory (GABA+) neurotransmitters has largely been unexplored. Here, in 46 (34 female and 12 male) human participants, we employed 7T magnetic resonance spectroscopy to explore associations between neurochemicals in left prefrontal cortex (PFC), right intraparietal sulcus (IPS) and right primary motor cortex (M1), and subtypes of mind-wandering. Across three behavioural paradigms, we employed self-caught mind-wandering probes as a proxy measure for meta-aware mind-wandering, and probe-caught to assess mind-wandering that occurs without meta-awareness. Results showed that mind-wandering associations with neurochemical concentrations varied by brain region, cognitive task, and the nature of mind-wandering. Specifically, probe-caught mind-wandering during the 2-back task and self-caught mind-wandering during the FT-RSGT was associated with neurochemical concentrations in the PFC. In addition, intentional mind-wandering was associated with GABA+ in the M1 for the 2-Back (probe caught) and FT-RSGT (self-caught). Unintentional mind-wandering was as associated with E/I balance in the PFC for the FT-RSGT (probe caught) and 2-Back (self-caught). These findings provide insights into the neurochemical basis of mind-wandering. The propensity to mind-wander, as well as meta-awareness and intentionality of mind-wandering, appear to depend on the demands of different tasks.<b>Significance statement</b> Mind-wandering - the failure to stay on task - has implications in a wide range of applied contexts. Further, when paired with neuroimaging, studying mind-wandering sheds light on the neurophysiological processes associated with cognitive control. A key neuroimaging research gap concerns the neurochemical basis of mind-wandering. Here, we explored associations between neurochemical concentrations across three cortical regions with mind-wandering, in three distinct tasks. The relationships varied across regions, tasks and the nature of the mind-wandering. These findings indicate that neurochemical concentrations, and particularly the excitatory balance of neurochemicals, predict mind-wandering propensity.