Determination of hemispheric emotional valence in individual subjects: a new approach with research and therapeutic implications

Abstract

Background: Much has been theorized about the emotional properties of the hemispheres. Our review of the dominant hypotheses put forth by Schore, Joseph, Davidson, and Harmon-Jones on hemispheric emotional valences (HEV) shows that none are supported by robust data. Instead, we propose that individual's hemispheres are organized to have differing HEVs that can be lateralized in either direction.

Methods: Probe auditory evoked potentials (AEP) recorded during a neutral and an upsetting memory were used to assess HEV in 28 (20 F) right-handed subjects who were either victims of childhood maltreatment (N = 12) or healthy controls. In a sub-population, we determined HEV by emotional response to lateral visual field stimulation (LVFS), in which vision is limited to one, then the other hemifield. We compare a number of morphometric and functional brain measures between individuals who have right-negative versus left-negative HEV.

Results: Using AEPs to determine HEV, we found 62% of controls and 67% of maltreated subjects had right negative HEV. There was a strong interaction between HEV-laterality and gender, which together accounted for 60% of individual variability in total grey matter volume (GMV). HEV-laterality was associated with differences in hippocampal volume, amygdala/hippocampal ratios, and measures of verbal, visual and global memory. HEV-laterality was associated also with different constellations of symptoms comparing maltreated subjects to controls. Emotional response to LVFS provided a convenient and complementary measure of HEV-laterality that correlated significantly with the HEVs determined by AEPs.

Conclusion: Our findings suggest that HEV-laterality, like handedness or gender, is an important individual difference with significant implications for brain and behavioral research, and for guiding lateralized treatments such as rTMS.

Figure 1

Total grey matter volume by gender and hemispheric emotional valence. This graph shows the total grey matter volume determined by FreeSurfer for male and female subjects with right and left hemispheric emotional valence by probe auditory evoked potentials.

Figure 2

AEP by left plus right amygdala/hippocampal ratios. A scatter plot of the relation between LI_AEP and the left plus right amygdala/hippocampal ratios. (r = -.86, p = .000).

Figure 3

Effect size for abuse is increased when D_AEP and interactions are in model. This shows the increases in effect size for abuse when Model 1 (Univariate ANOVA with group, gender and group × gender as factors) is used compared with Model 2 (Univariate ANOVA with group, gender, D_AEP and their interactions as factors).

Figure 4

Effect size for abuse for subjects with right and for those with left negative HEV. This figure shows that the effect size for abuse (versus control) changed, sometimes drastically, when two series of univariate ANOVAs were performed with each of 14 psychological variables (ASIQ_T, DES, HAM_D, MISS, and the 10 subscales of the SCL-90) as the dependent variable and group and gender as the independent variables. In the first series (in yellow), data from the 18 subjects with a right negative HEV were used, and in the second (in green), data from the 10 subjects from the left negative HEV group were used.

Figure 5

Total grey matter volume by gender and HEV by LVFS. This figure shows the total grey matter volume for males and females by the direction of their hemispheric emotional valence determined by LVFS.