The Postauricular Reflex as a Measure of Attention and Positive Emotion

The postauricular reflex is a muscular reaction that occurs behind the ear in response to short, abrupt sounds. Its magnitude increases with louder eliciting sounds, rotating the eyes in the direction of the eliciting sound, and flexing the head forward. The reflex exhibits prepulse inhibition, especially during attention to complex foreground stimuli. Its magnitude is larger (or potentiated) during pleasant than during neutral pictures, sounds, and videos that are highly arousing. This pattern is particularly evident for erotic, food, and nurturant scenes, suggesting it assesses more than just appetitive processing. This reflex’s potentiation varies across development; positively correlates with personality traits associated with well-being; and negatively correlates with such psychopathologies as depression, schizophrenia, and opioid dependence. It appears distinct from and uncorrelated with the startle blink reflex. New data suggest that activity in left frontal areas generates postauricular reflex potentiation during pleasant versus neutral pictures.

Clarifying domains of internalizing psychopathology using neurophysiology

Current initiatives such as the National Institute of Mental Health's Research Domain Criteria project aim to reorganize classification of mental disorders along neurobiological lines. Here, we describe how consideration of findings from psychiatric research employing two physiological measures with distinct neural substrates – the startle blink reflex and the error-related negativity (ERN) – can help to clarify relations among disorders entailing salient anxiety or depressive symptomatology. Specifically, findings across various studies and reviews reveal distinct patterns of association for both the startle blink reflex and the ERN with three key domains of psychopathology: (1) Fear (or phobic) disorders (distinguished by increased startle to unpleasant stimuli, but normal-range ERN). (2) Non-phobic anxiety disorders and negative affect (associated with increased ERN, increased startle across all types of emotional stimuli and increased baseline startle) and, more tentatively (3) Major depression (for which patterns of response for both startle and ERN appear to vary, as a function of severity and distinct symptomatology). Findings from this review point to distinct neurobiological indicators of key psychopathology domains that have been previously demarcated using personality and diagnostic data. Notably, these indicators exhibit more specificity in their relations with these three domains than has been seen in quantitative-dimensional models. Implications of these findings are discussed.