Resting heart rate variability modulates the effects of concurrent working memory load on affective startle modification

Vagally mediated heart rate variability (vmHRV) is thought to index top–down control processes in emotion regulation. According to the Generalized Unsafety Theory of Stress (GUTS), resting vmHRV indexes top–down resources that are needed to inhibit subcortical threat circuits, which is important for context-appropriate affective responding. Although this notion has been supported by studies of affective startle (SR) modification, direct evidence that top–down resources are the linking mechanism between vmHRV and context-appropriate affective responding has been lacking. To investigate this possible mechanism, college-aged participants (n = 92) were recruited to complete a picture viewing task and a concurrent working memory (WM) task. Concurrent WM load was manipulated, and the auditory SR stimulus was delivered while viewing affective pictures. Electrocardiography and electromyography were recorded to assess vmHRV and SR eyeblink, respectively. Results showed that WM load attenuated affective SR modification. As expected, the attenuating effects of load on affective SR modification were stronger among low vmHRV relative to high vmHRV individuals, indicating that vmHRV is linked to context-appropriate affective responding through the mechanism of top–down resources. These results support the GUTS and suggest that atypical affective responding among low vmHRV individuals is attributed to the lack of WM resources. Our findings highlight the relation between vmHRV and top–down resources that have been implicated in emotion regulation and contribute to a better understanding of emotion dysregulation in psychopathology.