Anterior cingulate neurons display subregion-specific interaction with frontal eye fields revealed by anti-/orthodromic stimulation and resting-state imaging.

The anterior cingulate cortex (ACC) influences saccade generation in the frontal eye fields (FEF), but the nature of this interaction remains unclear. Although prior imaging studies have suggested that ACC interacts with FEF, few studies have confirmed this by electrophysiological recordings. This study aimed to characterize the functional connectivity between ACC and medial and lateral FEF during cognitive saccade tasks. We combined resting-state functional MRI (rs-fMRI) with single-unit electrophysiology in macaque monkeys performing memory-guided saccade and pro-/antisaccade tasks. Anti- and orthodromic stimulation was used to electrophysiologically identify ACC neurons with monosynaptic connections to and mono- or polysynaptic connections from FEF, respectively. Anti- and orthodromically identified ACC neurons were predominantly connected with medial FEF, which showed stronger positive functional connectivity with ACC compared to lateral FEF. However, lateral FEF sites yielded greater correlation between task selectivity and positive functional connectivity with ACC: this stronger functional connectivity was particularly related to the postsaccadic and reward periods of different cognitive saccade tasks. With combined imaging and electrophysiology, our findings provide converging evidence for functional interactions between ACC and FEF, especially the goal-directed medial FEF regions. The correlation between functional connectivity and task-related neuronal selectivity supports ACC's interaction with FEF in the modulation of saccade generation. Additionally, we report evidence that mono- and polysynaptic connections may be related to positive functional connectivity, but we found no such relationship for negative functional connectivity (anticorrelations). These results advance our understanding of prefrontal cortical interactions in oculomotor behavior and the electrophysiological mechanisms of positive and negative resting-state functional connectivity.NEW & NOTEWORTHY The main novelty of this study is the combination of single-unit electrophysiology with resting-state functional MRI (fMRI). This work is of special interest to the emerging clinical relevance of negative functional connectivity, as researchers and clinicians examine the neurophysiological underpinnings of these anticorrelated networks.