Impaired decision making in hepatic encephalopathy relates to attenuated BOLD-signal in the right inferior parietal cortex

Aim: Impaired decision-making is observed in Hepatic Encephalopathy (HE). The underlying brain mechanisms of this metabolically induced behavioural alteration are not known. The aim of this functional MRI (fMRI) study was to identify brain regions showing differences in BOLD-response between controls and cirrhotic patients without manifest HE. Methods: 10 healthy controls, 9 patients with non-manifest HE (5 HE 0; 4 minimal [mHE]) were studied. For each volunteer 221 fMRI images (26 behavioural trials) were acquired (whole brain coverage) with a Siemens Vision 1.5T scanner. During an experimental session intrafoveal light stimulation was performed via a polymer-optical fiber test system. Probands had to indicate the onset of a flickering impression of an red light (critical flicker frequency [CFF]). BOLD signal at CFF threshold detection was measured and compared with the signal during observation of the steady red light. Results: Decision-related BOLD-activation was decreased in patients with HE 0 and mHE compared to controls particularly in the right inferior parietal lobe (IPL). Analysis of psychophysiological interactions suggests impaired effective connectivities between the IPL, the anterior cingulate cortex, the dorso-lateral prefrontal cortex, the prefrontal polar cortex and the motion-sensitive visual area V5. The findings provide evidence of an early impaired perceptual decision making in patients with HE 0 and mHE. Also altered cerebral function during non-decision making situations for passive viewing conditions was founded. Conclusion: We identified a distributed network of functionally impaired brain regions using a tool for analysis of CFF and fMRI in patients with HE 0 and mHE. By using a combination of CFF analysis and fMRI scanning we identified the neural correlate of CFF-threshold and detected significant differences in BOLD-activation between controls and patients with HE 0 as well as mHE.

Key words

BOLD-signal - Critical Flicker Frequency - Hepatic Encephalopathy - clinical study - functional MRI