ENSAYO DE LA RESISTENCIA A LA COMPRESIÓN (ASTM C39 / NTP 339.034)

To investigate the difference between the Ps-Dm effect across Info-Cue and No-Cue conditions, the cue epoch (0-3000ms) was divided into two time windows (0-1000ms and 1000ms-3000ms).

5.4.2.1 400-1000 ms: Early waves

A repeated measures analysis in this time window revealed a significant main effect of Cue

condition F (1, 27) = 12.88, p = .001, η2p = .323, indicated an overall larger positivity for the

Info-Cues (M = 5.21, SE = 1.61) than for the No-Cue condition (M = -3.66, SE = .96), and a

significant main effect of Valence F (1, 27) = 4.58, p = .041, η2_{p = .145, indicated that}

electrical potentials pertaining to the anticipation of negative pictures elicited more positive going deflection (M = 3.79, SE = 1.36) than the anticipation of neutral pictures (M = 1.05, SE = 1.14). A significant interaction was found for the Cue × Memory × Laterality F (1, 27) = 4.57, p = .015, η2p = .145. Subsidiary analysis revealed a significant interaction for Memory × Laterality F (1, 27) = 4.03, p = .023, η2p = .130 for the Info-Cue condition only. Further ANOVA analysis showed that this memory effect was not significant at any scalp site (Fs < 1.90, Ps > .179). Overall, these findings showed that regardless of valence, brain potentials for the Informative remembered cues were different from the No-Cue condition.

122 5.4.2.2 1000-3000ms: Late waves with -200 baseline

The Valence × Memory × Anteriority × Laterality, F (1, 27) = 3.745, p = .030, η2p = .122

interaction was significant. To elucidate this interaction, a Memory × Anteriority × Laterality ANOVA was further computed for negative and neutral cues, separately. For negative cues,

this interaction was found to be non-significant F (1, 27) = 2.145, p = .127, η2p = .074.

However, for neutral cues a marginally significant interaction was found for Memory ×

Anteriority, F (1, 27) = 3.742, p = .064, η2p = .122. However, decomposing the interaction

revealed no reliable effects for Memory at Anterior, F (1, 27) = .859, p = .362, η2p = .031 or

posterior electrodes, F (1, 27) = .082, p = .776, η2p = .003. Another significant interaction

was found for Cue × Memory × Laterality F (1, 27) = 6.40, p = .003, η2p = .192. Subsidiary

analysis revealed a significant Memory × Laterality F (1, 27) = 3.43, p = .040, η2p = .113,

interaction for Informative cues, but not for the No-Cue F (1, 27) = 2.96, p = .060, η2p =

.099. This Memory × Laterality interaction for the Info-Cue condition was driven by an

effect of memory visible at midline scalp site F (1, 27) = 6.695, p = .015, η2p = .199 but not

at the left F (1, 27) = 1.20, p = .282, η2p = .043 and right F (1, 27) = 1.79, p = .192, η2p =

.062 site (see figure 5.4).

123 Figure 5.5: ERP waveform and Scalp maps representing cue related activity across picture

valence.

a) ERP waveform plotted on left, midline, and right electrodes for cue-related activity according to subsequent memory (Remembered vs. Forgotten items) and cues (Informative vs. No Cue). Amplitude in microvolts is on the y-axis and time in milliseconds is on the x-axis.

b) Scalp maps plotting ‘remembered’ minus ‘ forgotten’ mean ERP amplitude scores for 400-1000ms

c) Scalp maps plotting ‘remembered’ minus ‘ forgotten’ mean ERP amplitude scores for 1000-3000ms.

5.4.2.3 1000-3000ms: Late waves with -1200 baseline

Separate analysis was performed for the sustained anticipatory period which is the period from 1000 time 3000ms when the cue disappears from the screen. For this purpose, a new -1200ms baseline period selected after using a 15 Hz filter to exclude the influence of neural activity generated due to the presence and absence of cue. Repeated measures ANOVA was conducted for the whole sustained anticipatory epoch with factors, Cue × Valence × Memory × Anteriority × Laterality. Interaction of interest Cue × Valence ×

Memory × Anteriority × Laterality was non-significant F (1, 27) = 1.02, p = .37, η2p = .037.

However, analysis revealed a significant main effect of cue condition F (1, 27) = 4.61, p =

.041, η2p = .146, indicated an overall larger negativity for the Info Cue (M = -1.56, SE =

.337) compared to No-Cue condition (M = -1.88, SE = .338). Other significant interaction

was Cue × Valence × Anteriority F (1, 27) = 7.86, p = .009, η2p = .225. For this interaction

further ANOVAs were conducted by cue categories. For No-Cue condition ANOVA revealed

124

for Info-cue condition F (1, 27) = 2.15, p = .154, η2p = .074. Further subsidiary analysis for

Valence categories at each scalp site (anteriority and posterior) revealed no significant difference. Simple effect analysis revealed a non-significant difference between amplitude of negative versus neutral picture for sustained anticipation at anterior F (1, 27) = .043, p =

.837, η2p = .002 and posterior scalp sites F (1, 27) = .811, p = .376, η2p = .029.2800-

3000ms: Stimulus Preceding Negativity (SPN)

A non-significant interaction was found for Cue × Valence, F (1, 27) = 3.75, p = .063, η2p =

.12. No main effects or interactions reached significance (Fs < .667, Ps > .421) for this time window.

5.4.2.4 Cue-related early peaks analysis

A visual examination of the cue-related ERP revealed three positive-going peaks at the anterior scalp site as compared to posterior. To examine if the valence and memory-related differences were captured by any of the earlier peaks after the cue onset, mean amplitudes were extracted from three-time windows: (200-350ms), (350-600ms), (700-800ms).

5.4.2.5 P1: 200-350ms

There was a significant main effect of Cue, F (1, 27) = 36.53, p < .001, η2

p= .575 indicating a

positive-going waveform for Info-Cue (M = 13.53, SE = 2.06) compared to No-Cue (M = .343,

SE = .97) conditions. The main effect of Valence F (1, 27) = 6.86, p < .014, η2

p= .203 was

significant with more positive going deflection for negative cues (M = 8.13, SE = 1.25) than neutral cues (M = 5.74, SE = 1.29). No other main effects or interactions reached significance (F’s < .140, p’s > .711).

5.4.2.6 P2: 350-600ms

A significant interaction between Cue × Valence × Laterality, F (2, 54) = 8.41, p < .001, η2

p= .238 was found. In order to better understand this interaction, a subsidiary Valence × Laterality ANOVA was computed separately for Informative and No-Cue conditions. For the Info-cue, a significant interaction was found for Valence × Laterality F (2, 54) = 7.61, p <

.001, η2

p= .220 indicating that amplitude for negative pictures were more pronounced with

a positive going deflection at midline (M = 75.511, SD = 50.30) compared to right lateralization (M = 45.86, SD = 53.96).

125

Figure 5.6: ERP waveform and Scalp maps representing cue related encoding activity across picture valence for 350-600ms time bin.

a) ERP waveform plotted on left, midline, and right electrodes for cue-related activity according to subsequent memory (Remembered vs. Forgotten items) and cues (Informative vs. No Cue). Amplitude in microvolts is on the y-axis and time in milliseconds is on the x-axis.

b) Scalp maps plotting ‘remembered’ minus ‘forgotten’ mean ERP amplitude scores for 350-600ms.

126 5.4.2.7 P3: 700-800ms

In this window the Valence main effect that appeared in the earlier two time windows (200- 350ms and 350-600ms) disappeared in the time window as the Valence main effect, F (1,

27) = 1.68, p = .206, η2_{p = .059 was non-significant. Main effect of Cue type was significant F}

(1, 27) = 33.92, p = .001, η2_{p = .548, reflecting an overall positivity for the Info-Cue (M = 8.43,}

SE = 1.77) than for the No-Cue condition (M = -2.60, SE = 1.29). No other effects reached significance