Median nerve stimulation combined with high gamma band activity can map the hand motor cortex during awake states, but its effectiveness declines with loss of consciousness. In five patients undergoing awake craniotomy, the sensitivity of mapping using the short-latency average envelope remained relatively stable, dropping only from 100% awake to about 82% during deeper anesthesia stages. In contrast, mapping based on average power deteriorated more sharply, from 100% awake to around 21% at the deepest stage. The long-latency average envelope also showed reduced sensitivity as consciousness declined, with a slope coefficient significantly smaller than that for short-latency responses. These results suggest that short-latency envelope-based mapping is more robust across different conscious states.
Rumination, a repetitive self-focused thinking style common in depression, is linked to abnormalities in the default mode network (DMN) of the brain. This study used a novel continuous-state paradigm to directly induce rumination or distraction in healthy participants across three MRI scanners. Results showed that during rumination, connectivity within the DMN generally decreased compared to distraction. Specifically, connectivity increased between the core and medial temporal lobe subsystems and decreased between the core and dorsal medial prefrontal cortex subsystem, as well as within the medial temporal lobe subsystem. Behavioral measures of rumination negatively correlated with connectivity between the core and dorsal medial prefrontal cortex subsystems, suggesting that rumination involves altered interactions among DMN components.