Background Several studies reported deficits in attention and inhibition in premanifest and manifest Huntington's disease (HD) but results are inconsistent. Understanding the nature of these deficits is important for disease monitoring and potential interventions targeting the earliest changes in HD. Simultaneous clinical and neurophysiological assessment can provide important insights in these complex cognitive processes. Go/No-go tasks are thought to measure attention and response inhibition. The event related potential P3 is hypothesised to be the neurophysiological substrate of attentional and inhibition processes.
Aims To evaluate whether attention and inhibition characteristics in manifest HD patients (MHD) and premanifest HD gene carriers (PMGC) differ from controls.
Methods We studied 14 MHD (mean age 51 years), 15 PMGC (mean age 43 years) and 15 controls (mean age 51 years) with a neuropsychological test and simultaneous EEG recording. The Sustained Attention to Response Task, a simple Go/No-go test hypothesised to measure attentional and inhibition processes, resulted in reaction time (RT) and accuracy data. The EEG assessment yielded data on P3 amplitudes and latencies.
Results The RT pattern during the Sustained Attention to Response Task was remarkably different (p<0.005), with MHD showing a slowing to the end of the task while PMGC and controls remained steady. Also, overall RT in MHD was slowed in comparison with PMGC and controls (p=0.001). In MHD, the number of errors for Go trials was increased (p<0.005), but no differences for No-go errors were found. P3 data showed that for MHD the No-go amplitude was lower than for the other two groups (p<0.05).
Conclusion We demonstrated deficits in inhibition and attention in MHD compared with PMGC and controls. MHD showed a general slowing and a different pattern of RT which in combination with reduced neuronal activity and accuracy is hypothesised to reflect a reduced capacity to effectively allocate attention and diminished inhibition.
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