Top-down and bottom-up processes in the extrastriate cortex of cirrhotic patients: an ERP study.
OBJECTIVE
This study aims to evaluate the efficiency of top-down and bottom-up processes in the extrastriate cortex of cirrhotic patients without overt hepatic encephalopathy (HE).


METHODS
Reaction times (RTs), accuracy and event-related potentials (ERPs) were recorded during the execution of a visual Simon task in 17 cirrhotic patients and 10 healthy controls. Amplitude and latency of the P1 and N1 (indexes of bottom-up processes) and of the N2pc (index of top-down processes) were measured.


RESULTS
Patients were slower than controls, and patients with minimal HE (MHE) were slower than patients without MHE. The distribution analysis of RTs showed that the Simon effect decays with slower RTs in all the groups and that the shape of the distribution was different in MHE patients. No differences were found between cirrhotic patients and controls for P1 and N1 amplitude and latency. In contrast, N2pc latency was delayed in cirrhotic patients compared to controls independently of MHE.


CONCLUSIONS
In the extrastriate cortex of cirrhotic patients without HE, top-down processes are altered whereas bottom-up processes are preserved.


CONCLUSIONS
The analysis of exogenous and endogenous visual components of ERPs provides a model to study the functional dissociation between top-down and bottom-up processes inside the extrastriate cortex.
Schiff
Sami
S
Department of Clinical and Experimental Medicine, University of Padua, Via Giustiniani, 2, 35128, Padova, Italy. sami.schiff@unipd.it
Mapelli
Daniela
D
Vallesi
Antonino
A
Orsato
Raffaele
R
Gatta
Angelo
A
Umiltà
Carlo
C
Amodio
Piero
P
D001921:Brain / Q000503:physiopathology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006501:Hepatic Encephalopathy / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008103:Liver Cirrhosis / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011930:Reaction Time