The featured paper is ‘Usefulness of event-related potentials in the assessment of mild cognitive impairment’ by Papaliagkas and colleagues (freely available here).
In the background the authors introduce the cognitive evoked related potentials and the major wave components – P300, N200 and slow waves which correspond to different aspects of stimulus evaluation whilst also noting that they know of no published research into the relationship between slow waves and mild cognitive impairment. They also note that the P300 component could be an important marker of cognitive function.
There were multiple aims stated in this study which included an examination of the differences in ERP components between different age groups and also between people with MCI and controls. They also wanted to see if ERP’s could be used in the diagnosis of MCI and in identifying those that convert to dementia.
The researchers used a discriminatory task which involves the subject distinguishing two tones and counting tones of a particular type. The technical aspects of the EEG acquisition are described and subjects were tested twice to confirm the waveforms. The data was then analysed according to the latencies and amplitudes of the ERP components both within groups and between groups.
Roughly 2/3 of the patient group were female while gender in the control group was evenly represented. The mean age in the groups was roughly 68 years. There were a large number of results given the number of in-group and between-group comparisons and the component waveforms that were analysed. However there were a few main findings of interest
(1) Firstly within the control group there was found to be a dependent relationship between the P300, N200 and slow wave components in keeping with the component waveform generators being coupled.
(2) Within the MCI group there was evidence of decoupling of the waveform generators
(3) In the small number of people that converted from MCI to dementia there was a significantly delayed latency in the N200 waveform compared to those with MCI that did not convert. Thus a cut-off point of 287 ms gave 100% sensitivity and 91% specificity.
While this is a small study, it produces several testable and clinically relevant hypotheses.
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