A disorder of metamemory, expressed as unawareness of mnemonic ability, is typically associated with the profound amnesia of Korsakoff's Syndrome (KS). A similar but less severe type of limited awareness can also occur in non-KS alcoholism and is observed as an impairment in generating Feeling-of-Knowing (FOK) predictions about future recognition performance. We previously found that FOK accuracy was selectively related to volumes of the insula in alcoholics involved in the present study. Unknown, however, are the neural substrates of unawareness of memory impairment in alcoholism. A task-activated fMRI paradigm served to identify neural nodes and networks implicated in inaccurate self-estimation of mnemonic ability in sober alcoholics while they made prospective FOK judgments in an episodic memory paradigm. Lower activation in the right insula correlated with greater overestimations of future memory abilities in alcoholics. Weaker connectivity of the right insula with the left dorsal anterior cingulate cortex, a node of the salience network, and stronger connectivity of the right insula with the right ventromedial prefrontal cortex (vmPFC), a node of the default mode network (DMN), co-occurred in alcoholics relative to the controls. Specifically, alcoholics, who failed to desynchronize insula-vmPFC activity, had greater overestimation of their memory predictions and poorer recognition performance. This study provides novel support that deviant functional activation and connectivity involving the right insula, a hub of the salience network, appears to participate in disrupting metamemory functioning in alcoholics. Compromised FOK performance might result from disturbance of the switching mechanism between brain networks serving self-referential processes (i.e., DMN network) and networks serving externally-driven activities like memory monitoring (i.e., fronto-parietal network). Thus, compromise in insular network coupling could be a neural mechanism underlying anosognosia for subtle mnemonic impairment in nonamnesic alcoholism.
Adult Aged