1. 1
Electrophysiological recordings The EEG activity was continuously recorded from 32 active electrodes mounted on an elastic cap (ActiCap, Brain Products, Munich, Germany) according to the extended International 10–20 System. A linked-mastoid reference was used. The ground electrode was at AFz. Vertical and horizontal eye movements were recorded by electrode pairs positioned in a bipolar montage above and below the left eye and on each outer canthus, respectively. The EEG signal was amplified, filtered ( Hz), and digitized at 1000 Hz. The impedence of all electrodes was kept below 10 kΩ.
Word recognition memory task Stimuli were 120 Italian words of common use ranging between 4 and 10 letters in length. Words were presented on the center of a computer screen for 600 ms, with a variable inter-trial interval of at least 5000 ms and were preceded by a fixation point for 700 ms.
The experimental protocol was divided in six blocks. Each block consisted of a learning phase and a test phase. During the learning phase, subjects were asked to read aloud and to memorize a list of 10 words. The test phase began immediately after the completion of the learning phase. Ten words from the learning phase and 10 new words were presented in a randomized order. Subjects were requested, in a yes–no recognition task, to judge whether the presented word had been already shown in the learning phase (‘old’) or not (‘new’). Verbal responses were collected.
Data analysis
Behavioural data The measures used to quantify the behavioral performance was the discrimination index (i.e. the proportion of hits minus the proportion of false alarms). Independent sample t-test has been used to compare the discrimination index between the two groups.
ERP data Continuous EEG was off-line bandpass filtered between 0.01 and 30 Hz and segmented into epochs of 1000 ms starting 200 ms prior to stimulus presentation. A baseline correction using the activity in the 200 ms that preceded the onset of the word appearance was applied. Epochs were separately averaged for ‘old’ and ‘new’ condition.
The mean amplitudes in two consecutive time windows after the onset of the word ( ms and 500–800 ms) were calculated for each condition and separately entered in a mixed analyses of variance (ANOVA) with ‘group’ (HF vs no-HF) as between-subjects factor, and ‘experimental condition’ (Old and New), ‘electrode’ (Frontal, Central, and Parietal), and ‘laterality’ (Left, Midline, and Right) as within-subject factors.
Post hocs were performed using paired t-tests and Bonferroni correction for multiple comparisons. All test were two-tailed and significance was set at P < 0.05.
CONCLUSION
Present findings support the relationship between LVEF and cognitive performance. These data suggest that ERPs may reveal possible functional brain abnormalities that might be not observed at behavioral levels in patients without overt heart failure.
METHODS
Participants:
Twenty-five male patients with CAD (13 without [LVEF > 55%] and 12 with [LVEF < 40%] left ventricular dysfunction), and a Mini Mental State Examination score > 25 were enrolled (Table 1).
OBJECTIVE
The relationship between left ventricular ejection fraction (LVEF) and cognitive performance in patients with coronary artery disease (CAD) without overt heart failure is still under debate. In the present study we combine behavioral measures and event-related potentials (ERPs) to verify whether electrophysiological correlates of recognition memory (Old/New effect) is modulate differently as a function of LVEF.
REFERENCES
Jefferson AL et al. Relation of left ventricular ejection fraction to cognitive aging (from the Framingham Heart Study). Am J Cardiol. 2011;108:
Jurgens CY, Faulkner KM, Lee CS. Phenotypic profiling of cognitive impairment risk among patients with heart failure: a literature review of the usefulness of cardiac-related variables. Eur J Cardiovasc Nurs. 2013;12:
Vogels RL et al. Cognitive impairment in heart failure: a systematic review of the literature. Eur J Heart Fail May;9(5):440-9.
Patients without left ventricular dysfunction [LVEF > 55%]
RESULTS
Event-related potential correlates of word recognition memory in patients
with coronary artery disease Giovannelli F,1,2 Simoni D,3 Baldasseroni S,3 Tarantini F,3 Pratesi A,3 Bartoli N,3 Foschini A,3 Giganti F,1 Cincotta M,2 Viggiano MP1
1Dipartimento di Neuroscienze, Psicologia, Area del Farmaco, Salute del Bambino (NEUROFARBA), Università degli Studi di Firenze
2UO di Neurologia, Azienda Sanitaria di Firenze
3SOD di Cardiologia e Medicina Geriatrica, Dip. di Medicina Sperimentale e Clinica, Università degli Studi di Firenze
Patients with left ventricular dysfunction [LVEF < 40%]
Behavioural data
The accuracy (as measured by the discrimination index) was lower in the group with LV dysfunction compared to the group without LV dysfunction, however this difference was not significant (Table 2).
ERP data
For the time window ms after the word presentation, the interactions ‘group’ x ‘experimental condition’ x ‘electrode’ was significant (P < 0.05). Post hoc comparisons revealed that old-new effect (more positive-going waveforms for old items compared with new items) emerged on the fronto-central electrodes in the group of patients without LV dysfunction (LVEF > 55%), but not in the group with LF dysfunction (LVEF < 40%).
No significant differences emerged in the ms time window.