نسبت EEG تتا/بتا در رابطه با مدوله ترس واکنش مهار، کنترل توجه و صفات عاطفی

Abstract Power density-ratios of fast and slow frequency spectrum-bands can be calculated from resting-state electroencephalography (EEG) recordings. A well-established phenomenon is that slow wave/fast wave ratios (SW/FW) are increased in attention-deficit/hyperactivity disorder. Several researchers have also begun to study relationships between SW/FW and affect. This work suggests that increased SW/FW may reflect reduced frontal cortical control over subcortical affective approach drive. The present study (n = 28) aimed to further examine this notion by testing several predictions derived from it. In line with these predictions, SW/FW was found to correlate negatively with fearful modulation of response inhibition in an emotional go/no-go task and with self-reported attentional control. Results also suggested a positive relation between SW/FW and trait approach motivation and a negative relation to anxiety, as predicted. These results are consistent with previous studies and support the notion that SW/FW may provide a useful tool in the study of affect and emotion regulation.

Results 2.1. Self-report measures—emotional traits and attentional control An expected significant positive correlation was found between STAI-t and BIS (r = .753; p < .001). There was an expected negative correlation for ACS and STAI-t (r = −.358; p = .031; one-tailed). BAS Drive was positively correlated to θ/β ratio (r = .430; p = .022) as expected. No other significant bivariate correlations were observed. Since STAI-t and ACS were expected to both correlate negatively to θ/β ratio while a negative correlation was also expected between these two predictors, partial correlations between θ/β ratio and the one, controlling for the other were calculated. When controlling for ACS, the negative partial correlation between STAI-t and θ/β ratio was r = −.386; p = .047. Note that these p-values are not corrected for multiple testing and correlations to a total of five emotional self-report measures were tested. The ACS was negatively correlated to θ/β ratio (r = −.395; p = .037) as expected; when controlling for STAI-t, the negative partial correlation was r = −.505; p = .007. 2.2. EEG measures Table 1 provides mean power density measures for θ, δ, and β, and θ/β and δ/β ratios for all electrodes. As can be seen, SW/FW ratios tend to be greater for midline compared to lateral recordings, specifically for more anterior recordings. Also, θ/β ratios tend to decrease from frontal to parietal recordings. Table 1. Mean power density values for the θ, δ, and β EEG frequency bands and θ/β and δ/β ratios, for the 9 recording sites separately. Higher ratio scores reflect relatively more slowly compared to fast wave power. F3 Fz F4 C3 Cz C4 P3 Pz P4 θ 4.740 (3.489) 6.066 (5.279) 4.754 (3.659) 4.444 (3.308) 6.253 (4.401) 4.335 (3.076) 4.213 (3.178) 4.990 (4.025) 4.105 (3.156) δ 18.075 (10.388) 19.402 (11.048) 17.798 (10.665) 16.547 (10.243) 20.010 (11.243) 16.668 (10.042) 18.655 (13.178) 19.515 (12.062) 17.571 (11.818) β .706 (.320) .720 (.337) .738 (.320) .671 (.331) .777 (.377) .692 (.330) .701 (.342) .779 (.378) .707 (.340) θ/β 7.143 (3.886) 9.134 (5.776) 6.882 (4.013) 7.471 (4.776) 8.901 (5.274) 6.972 (4.319) 6.542 (3.855) 6.897 (4.240) 6.243 (3.752) δ/β 28.739 (15.705) 31.070 (17.508) 26.817 (14.275) 29.289 (19.099) 29.768 (16.630) 27.973 (16.600) 29.913 (18.228) 28.478 (16.223) 27.936 (16.345) Table options 2.3. Emotional go/no-go See Table 2 for a summary of EGNG data. Correct responses to happy go cues were made faster than to fearful go cues, as expected (t(27) = 5.65; p < .001; d = .55). As expected, participants were more likely to respond with a false alarm to happy cues than to fearful cues; t(27) = 3.60; p = .001; d = .61). Comparison of d-prime scores showed that happy faces were also discriminated better than fearful faces: t(27) = 3.84; p = .001; d = .69. Finally, beta was greater for fearful faces than for happy faces (t(27) = 3.2; p = .004; d = .59), indicating a more inhibited response bias toward fearful than happy faces, as predicted. Because of the strong d-prime difference between the face-types (demonstrating differential discriminability), only beta-derived EBC scores are related to self-report measures and EEG ratios below. Table 2. Mean (SD in parentheses) RTs, total numbers of hits and false alarms (adjusted for z-transformation), d-prime, and beta values for the emotional go/no-go task (n = 28). Note that the false alarm score in the ‘happy is go’ condition represents the total number of erroneously executed key presses when a fearful face was presented as a no-go cue and vice versa for ‘fearful is go’. RT Hits False alarms d-Prime Beta Happy is go 453 (57) 142.39 (1.59) 8.04 (4.23) −2.89 (.36) .54 (.20) Fearful is go 487 (67)** 142.21 (2.02) 10.82 (4.91)** 2.64 (.36)** .66 (.21)* * p < .005. ** p < .001. Table options As hypothesized, STAI-t was significantly correlated to EBC (r = .395; p = .046) indicating more relative inhibition on fearful cue trials than on happy cue trials in the more anxious subjects. Contrary to expectation, there was no correlation between BIS and EBC (r = .133; p > .1). EBC scores were negatively correlated to δ/β ratio (r = −.435; p = .021) and θ/β ratio (r = −.443; p = .018), indicating that subjects with higher ratios demonstrated attenuated relative inhibition in response to fearful as compared to happy faces, as hypothesized ( Fig. 1). Scatterplot for the relation between log-normalized frontal θ/β ratio and the ... Fig. 1. Scatterplot for the relation between log-normalized frontal θ/β ratio and the expression beta contrast (EBC). Higher EBC score indicates greater relative inhibition to respond to fearful compared to happy go cues. The negative relation depicted here shows that increased θ/β ratio predicts less fearfully inhibited emotional go/no-go behaviour. Figure options 2.4. Locality To assess spatial specificity of the most important relations between SW/FW and outcome measures, correlations for θ/β ratios based on separate frontal and averaged frontal, central and parietal recordings were post hoc compared. Table 3 provides an overview of these correlations. Table 3. Pearson's correlation coefficients between the most relevant outcome measures and θ/β ratios derived from the averaged frontal, central, and parietal recordings. The corresponding p-value is given between parentheses. N = 28. Frontal Central Parietal BAS Drive .430 (.022) .445 (.018) .448 (.017) ACS −.395 (.037) −.376 (.048) −.265 (.173) EBC −.443 (.018) −.363 (.058) −.314 (.104) Table options Averaged frontal and central recordings provide very similar correlations that do not differ significantly according to Steiger tests for comparison of dependent correlation coefficients (largest t = 1.64). Although the correlations between parietal θ/β ratio and two of the three outcome measures are non-significant, only for the relation between θ/β ratio and ACS was there a significant difference, with the central recording showing a stronger correlation than the parietal recording (t(25) = 2.67; p = .013). Thus, sagittal locality seems to matter very little, with apparently stronger correlations for more anterior recordings, but the differences are small and mostly statistically insignificant. 1 2.5. Influence of age Also relations involving age were checked. This showed firstly a very strong negative relation between age and θ/β ratio (r = −.673; p < .001) and a negative relation between age and δ/β ratio (r = −.466; p = .012). Also the relations between age and BAS Drive, ACS, and EBC score were significant, with coefficients very similar (inverse) to the relations between these measures and θ/β ratio. For BAS Drive a negative correlation with age was r = −.431; p = .022, for ACS, a positive correlation with age was r = .414; p = .028, and for EBC score, a positive correlation was r = .429; p = .023. In order to control for the possibility that age might mediate relations between θ/β ratio and the relevant outcome measures (emotional trait, attentional control, and EBC), post hoc separate hierarchical regression analyses were performed with the outcome measures as dependent variables, θ/β entered as predictor in the first block, and age entered in the second block. For none of the outcome measures did these analyses show mediation (adding age never explained significantly more variance and all partial correlations were non-significant; smallest p = .246).