Sex differences in ERP Neurodynamics and Scalp Topography of Emotional Memory Marc E. Lavoie Emma Glaser, Adrianna Mendrek Department of Psychiatry and neuroscience University of Montréal Centre de recherche de l’Institut Universitaire en Santé Mentale de Montréal MONTRÉAL CANADA First I want to thank the organizers for the opportunity to present our data about…

Context In a comprehensive review of literature on ERP and emotions, it was noted that very few studies have controlled for sex (Oloffson, Polich & Sequeira ., 2008). But those that have, typically observed important differences between men and women (Olofsson, Polich & Sequeira et al., 2008). Several other studies have also found sex differences with respect to emotional valence, especially in response to unpleasant images (Bradley et al., 1992; Kemp et al., 2004; Lithari et al., 2010) In a comprehensive review of literature, Olofsson et al. (2008), noted that very few studies have controlled for sex, but those that have, typically observed important differences between men and women. have found sex differences with respect to valence, especially in unpleasant images (Bradley et al., 1992; Kemp et al., 2004; Lithari et al., 2010)

Emotional pictures recognition (performances: RT, accuracy, etc…) Experimenting with men and women counfounded Better recognition to high arousal images (Neumann et al., 2007; Gasbarri et al, 2006). Delayed reaction times for unpleasant as compared to pleasant pictures (van Strien et al., 2009).

Emotional pictures and brain activity (Event-Related Potentials) With men and women coufounded Larger parietal P300 and late positivity (LPP) amplitudes to emotional vs neutral pictures (McNeely et al., 2004; Schupp et al., 2000). Emotional valence affect earlier frontal-central components Emotional arousal affect later and more parietal components (Dolcos & Cabeza., 2002). Sex comparison (Glaser et al., 2012) Sex differences are sensitive to both valence and arousal. ERP responses are affected at different times in the processing stream., N200, P300 and LPP (Glaser et al., 2012). Even if there is no such study combining ERPs and emotional pictures episodic memory comparing control and Sz, we can underline that: Controls generally showed larger late positive components amplitudes to emotional vs neutral pictures. At least one research showed that emotional valence affect earlier frontal-central components while emotional arousal affect later and more parietal components (Dolcos & Cabeza., 2002).

Questions Emotional valence as well as arousal impact on performance and ERP topography. Sex differences in performances are also observed during memory tasks. What about emotional memory ? What are the scalp distribution and the possible generating sources of these sex differences.

Aims and hypotheses Aims Hypotheses Investigate sex differences in emotional memory : Valence and arousal independently. Brain scalp topography of N200/P300 component Hypotheses Based on prior research and existing literature we hypothesize : an interaction between memory, valence and arousal that will be reflected in performance and brain activity. Larger old/new effect in women for the treatment of valence and arousal. Sex differences in scalp topography and source localization of the old/new effect. So, our aims is twofold: First, we examined whether recognition performance would be affected by emotional images controlled for both valence and arousal level ratings. Second, we investigated sex differences in emotional memory, while valence and arousal remained independent. To our knowledge, this has not been systematically performed at both the behavioral and electrophysiological level. Based on prior research and existing literature, we hypothesized that there will be an ERP interaction between memory, valence and arousal. Moreover, we predict sex differences in the old/new effect for the treatment of the various categories of valence and arousal images.

Participants Measures Design Protocol Methodology Participants Measures Design Protocol

Participants and evaluation 17 Men 17 Women Handedness: All right handers Mean age: 30 yrs old (ns group differences) Intelligence: Raven test (Normal range) SES: Comparable SES in both groups For the women: control for hormonal status and menstrual cycle 4-8 days (Champagne et al., 2012).

Psychophysiological measures ERPs were obtained from 54 EEG electrodes Two components were extracted 200-400 ms (N200) 400-500 ms (P300) N200

Arousal valence International Affective Picture System - norms [orthogonal design] high High arousal- Low valence (Unpleasant) High arousal- High valence (Pleasant) High arousal- High valence (Pleasant) High arousal- High valence (Pleasant) High arousal- High valence (Pleasant) High arousal- Low valence (Unpleasant) High arousal- Low valence (Unpleasant) High arousal- Low valence (Unpleasant) Arousal Low arousal- Low valence (Unpleasant) Low arousal- High valence (Pleasant) Low arousal- Low valence (Unpleasant) Low arousal- High valence (Pleasant) Low arousal- High valence (Pleasant) Low valence unpleasant pleasant

Episodic memory protocol Study design 200 images Study phase (100 items) Test phase (100 new + 100 old) 25 images per category LV – LA LV – HA HV – LA HV - HA 40 minutes study-test delay 4000 ms 2000 ms - variable Unpleasant Pleasant old new Keyboard press

Statistics MANOVA factorial design Sex (2) by Memory (2) X valence (2) X arousal (2) X hemisphere (2) Standard Low Resolution Brain Electromagnetic Tomography (sLORETA) T-test of the old-new effect

Reaction times Performance Frontal N200 Central LPC Results Reaction times Performance Frontal N200 Central LPC

Reaction times No sex difference in response to pleasant images. Reduced memory effect in women to unpleasant high arousal compare to low arousal. [ Memory by valence by sex F(1,32)=10.14, p<.005 ] [ Memory by arousal by sex F(1,32)=7.29, p<.01 ] High Low There is a general delay of Reaction Times in response to high arousal images, while the valence have no significant impact on RT. The controls and Sz responded similarly We are replicating previous results with controls. However, we didn’t find that delayed RT for pleasant in Sz. High Low Pleasant Unpleasant

Speed accuracy composite score Men showed more efficient performances to : unpleasant images. high arousal images. Women showed more efficient performances to: Pleasant images. Valence by sex: F(1,32)=15.80, p < 0.001 Arousal by sex: F(1,32)=5.69, p < 0.05 The speed-accuracy composite score is obtained by subtracting normalized reaction times from the normalized discrimination accuracy score (Pr) recorded in our task, thus eliminating potential speed/accuracy tradeoff effects in the data; the higher the score, the more efficient the performance (see Section 2.3 for details). Further ANOVAs showed arousal was only significant in men (Fig. 1A), demonstrating greater efficiency for high arousal a valence effect was significant in men showing a more efficient performance for low valence – unpleasant images (F(1,16)=8.28, p 0.05) A valence effect was also significant in women showing a more efficient performance for pleasant images High arousal Equation to eliminate potential speed/accuracy tradeoff effects in the data: Composite score = Normalized (RT – Pr). Unpleasant Pr = Hits - FA

Frontal region (200-500 ms post-stimulus) (Sex by valence x arousal by hemisphere effect) Left hemisphere Right hemisphere Women: Right hemisphere memory effect in pleasant (high valence). Left hemisphere effect with unpleasant (low valence). Pleasant Unpleasant

Frontal region (200-500 ms post-stimulus) (Sex by arousal by hemisphere effect) Left hemisphere Right hemisphere Women: Left hemisphere memory effect in response to pleasant (high or low arousal). Right hemisphere frontal effect to unpleasant (high or low arousal). Pleasant Unpleasant High arousal Low arousal

200-500 ms post-stimulus frontal region = valence effect in high arousal (Sex by valence x arousal by hemisphere effect) Left hemisphere Right hemisphere Men in response to high arousal: Relative to women, men showed a frontal memory effect that was Reduced Equivalent scalp topography of the memory effect for pleasant and unpleasant images Left hemisphere Right hemisphere Pleasant Unpleasant

(200-500 ms post-stimulus) parietal region = valence effect in low arousal (Sex by valence x arousal by hemisphere effect) Left hemisphere Right hemisphere Men in response to low arousal: Relative to women, men showed a parietal memory effect Larger in the left hemisphere. Equivalent scalp topography for pleasant and unpleasant images Left hemisphere Right hemisphere Pleasant Unpleasant

What are the sex differences in terms of ERP current source density and emotions?

sLORETA P300 source density Sex differences contrast of the old-new effect (per valence and arousal) Pleasant Unpleasant High arousal Sex differences in the superior frontal gyrus (BA11) memory effect for high arousal pleasant and unpleasant images. Pleasant Unpleasant Low arousal Sex differences in the parietal memory effect for low arousal pleasant and unpleasant images (left superior parietal lobule – BA7) .

Conclusions

Conclusion Sex differences in memory performances Men showed more efficient performances to unpleasant and high arousal images, while women showed more efficient performances to pleasant ones. Sex differences and cortical activation (200 - 500 ms) Women showed a left hemisphere memory effect in response to pleasant (high or low arousal). Women showed a right hemisphere frontal effect to unpleasant (high or low arousal). Sex differences in brain localization of source density. Superior frontal gyrus (BA11) for high arousal. Left superior parietal lobule (BA7) for low arousal.

Discussion Important findings from imaging studies showed that successful encoding of emotional memory activates the left amygdala in women but the right amygdala in men (Cahill et al., 2004, Cahill et al., 2001, Canli et al., 2002 and Mackiewicz et al., 2006). It is easier to remember emotionally arousing events than it is to recall those that are neutral (Bradley, Greenwald, Petry, & Lang, 1992). This phenomenon is known as the emotional enhancement of memory (EEM) (Sommer et al., 2008 and Talmi et al., 2008). Sex-related differences have become a new focus in the study of emotional memory (Cahill, 2006). An important finding from imaging studies is that successful encoding of emotional memory activates the left amygdala in women but the right amygdala in men (Cahill et al., 2004, Cahill et al., 2001, Canli et al., 2002 and Mackiewicz et al., 2006). This female-left/male-right effect of amygdala activity was coined the “sex-related lateralization of amygdala function” (Cahill, 2003), or the “sex-related difference” in the present study. Other recent studies, however, have failed to find this effect (Kensinger and Schacter, 2006, Kensinger and Schacter, 2008 and Talmi et al., 2008), although the reason for this inconsistency remains to be elucidated.

Take home message Valence and arousal of photographic images must be carefully selected in an emotional memory paradigm. Future experiments in emotional memory must take into account sex differences.

Future directions Hormonal status and repeated measures design. Effects of psychotic symptoms on emotional memory. Brain imaging … and many other things.

The team.. M Hernandez | M. Germain | J. Jimenez | M. Lavoie | C. Hosatte-Ducassy | E. Glaser Neuropsychologist EEG tech Psychiatrist Director summer student RA And also… Dr Adrianna Mendrek and Nadia Lakis (not present in this picture) Sponsored by: Canadian Institute of Health Research National Science and Engineer Research Council