Affordable Access

The slowed brain: Cortical oscillatory activity in hepatic encephalopathy

Authors
Journal
Archives of Biochemistry and Biophysics
0003-9861
Publisher
Elsevier
Publication Date
Volume
536
Issue
2
Identifiers
DOI: 10.1016/j.abb.2013.04.004
Keywords
  • Critical Flicker Frequency (Cff)
  • Electroencephalography (Eeg)
  • Magnetoencephalography (Meg)
  • Oscillations
  • Slowing
  • Synchronization
Disciplines
  • Biology
  • Medicine

Abstract

Abstract Oscillatory activity of the human brain has received growing interest as a key mechanism of large-scale integration across different brain regions. Besides a crucial role of oscillatory activity in the emergence of other neurological and psychiatric diseases, recent evidence indicates a key role in the pathophysiology of hepatic encephalopathy (HE). This review summarizes the current knowledge on pathological alterations of oscillatory brain activity in association with liver dysfunction and HE in the context of spontaneous brain activity, motor symptoms, sensory processing, and attention. The existing literature demonstrates a prominent slowing of the frequency of oscillatory activity as shown for spontaneous brain activity at rest, with respect to deficits of motor behavior and motor symptoms, and in the context of visual attention processes. The observed slowing extends across different subsystems of the brain and has been confirmed across different frequency bands, providing evidence for ubiquitous changes of oscillatory activity in HE. For example, the frequency of cortico-muscular coherence in HE patients appears at the frequency of the mini-asterixis (⩽12Hz), while cirrhotics without overt signs of HE show coherence similar to healthy subjects, i.e. at 13–30Hz. Interestingly, the so-called critical flicker frequency (CFF) as a measure of the processing of an oscillating visual stimulus has emerged as a useful tool to quantify HE disease severity, correlating with behavioral and neurophysiological alterations. Moreover, the CFF reliably distinguishes patients with manifest HE from cirrhotics without any signs of HE and healthy controls using a cut-off frequency of 39Hz. In conclusion, oscillatory activity is globally slowed in HE in close association with HE symptoms and disease severity. Although the underlying causal mechanisms are not yet understood, these results indicate that pathological changes of oscillatory activity play an important role in the pathophysiology of HE.

There are no comments yet on this publication. Be the first to share your thoughts.