This study investigates the functional connectivity between the posterior cingulate cortex (PCC) and medial frontal gyrus/ventral anterior cingulate cortex (MFG/vACC) during a working memory task and at rest. It explores how this connectivity relates to performance on the working memory task. The results show that these two regions are functionally connected in both conditions. Moreover, performance on the working memory task was positively correlated with the strength of this functional connection not only during the task but also at rest. This suggests that these regions are components of a network that may facilitate or monitor cognitive performance rather than being disengaged during cognitive tasks. The study also raises the possibility that individual differences in coupling strength between these two regions at rest predict differences in cognitive abilities important for this working memory task. The findings support the idea that the default mode network is not simply deactivated during cognitive tasks but may still be engaged in a way that supports cognitive processing. The study also highlights the importance of examining both activation and deactivation patterns in understanding brain function. The results suggest that functional connectivity between these regions is related to cognitive performance, challenging the view that interactions within the default mode network detract from cognitive performance. The study also has implications for understanding cognitive impairments in conditions such as Alzheimer's disease, where decreased connectivity within the default mode network is associated with cognitive dysfunction. Overall, the study provides insights into the role of brain connectivity in cognitive performance and highlights the importance of examining connectivity patterns in understanding individual differences in cognitive abilities.This study investigates the functional connectivity between the posterior cingulate cortex (PCC) and medial frontal gyrus/ventral anterior cingulate cortex (MFG/vACC) during a working memory task and at rest. It explores how this connectivity relates to performance on the working memory task. The results show that these two regions are functionally connected in both conditions. Moreover, performance on the working memory task was positively correlated with the strength of this functional connection not only during the task but also at rest. This suggests that these regions are components of a network that may facilitate or monitor cognitive performance rather than being disengaged during cognitive tasks. The study also raises the possibility that individual differences in coupling strength between these two regions at rest predict differences in cognitive abilities important for this working memory task. The findings support the idea that the default mode network is not simply deactivated during cognitive tasks but may still be engaged in a way that supports cognitive processing. The study also highlights the importance of examining both activation and deactivation patterns in understanding brain function. The results suggest that functional connectivity between these regions is related to cognitive performance, challenging the view that interactions within the default mode network detract from cognitive performance. The study also has implications for understanding cognitive impairments in conditions such as Alzheimer's disease, where decreased connectivity within the default mode network is associated with cognitive dysfunction. Overall, the study provides insights into the role of brain connectivity in cognitive performance and highlights the importance of examining connectivity patterns in understanding individual differences in cognitive abilities.