# A questionnaire measure of adult attachment anxiety correlates with frontal hemispheric asymmetry in sleep spindle activity

## TL;DR

This study found that higher right frontal sleep spindle activity is linked to higher adult attachment anxiety, suggesting a neural marker for emotional traits.

## Contribution

The study introduces a novel link between frontal sleep spindle asymmetry and adult attachment anxiety, independent of neuroticism.

## Key findings

- Right frontal slow spindle lateralization correlates with higher attachment anxiety.
- The relationship between spindle lateralization and attachment anxiety remains significant after controlling for neuroticism.
- Attachment avoidance–independence is not associated with frontal spindle lateralization.

## Abstract

Subjects with high levels of attachment anxiety and neuroticism were proposed to be characterized by higher relative right rather than left frontal activity. Since sleep spindles are argued to reflect enhanced offline neuroplasticity, higher spindle activity measured over the right frontal areas relative to the corresponding left frontal ones could index higher attachment anxiety and neuroticism. Our aim was to explore the relationship between the lateralization patterns of frontally dominant slow sleep spindles and questionnaire measures of adult attachment anxiety and neuroticism. Thirty-four healthy subjects (male = 19; Mage = 31.64; SDage = 9.5) were enrolled in our preliminary study. Second night EEG/polysomnography records and questionnaire measures of personality (Zuckerman–Kuhlman Personality Questionnaire) and adult attachment (Relationship Scales Questionnaire) were collected. Frontal slow sleep spindles were measured by the Individual Adjustment Method (IAM), whereas hemispheric asymmetry indexes of spindle occurrence rate, duration, and amplitude were derived as normalized left–right differences (electrode pairs: Fp1–Fp2, F3–F4, and F7–F8). Relative right lateralization of frontolateral and frontopolar slow sleep spindle density and mid-frontal slow spindle duration were associated with attachment anxiety, but spindle lateralization was less closely related to neuroticism. The relationships between frontal slow spindle laterality and attachment anxiety remained statistically significant even after controlling for the effect of neuroticism, whereas attachment avoidance–independence was not correlated with frontal slow spindle lateralization. Right frontal lateralization of slow sleep spindle activity might indicate attachment status in terms of the negative view of the self.

The online version contains supplementary material available at 10.1007/s41105-022-00426-0.