Abstract
Startle eyeblink reflex is a valid non-invasive tool for studying attention, emotion and psychiatric disorders. In the absence of any experimental manipulation, the general (or baseline) startle reflex shows a high inter-individual variability, which is often considered task-irrelevant and therefore normalized across participants. Unlike the above view, we hypothesized that greater general startle magnitude is related to participants’ higher anxiety level. 111 healthy young women, after completing the State-Trait Anxiety Inventory (STAI), were randomly administered 10 acoustic white noise probes (50 ms, 100 dBA acoustic level) while integrated EMG from left and right orbicularis oculi was recorded. Results showed that participants with greater state anxiety levels exhibited larger startle reflex magnitude from the left eye (r109 = 0.23, p < 0.05). Furthermore, individuals who perceived the acoustic probe as more aversive reported the largest anxiety scores (r109 = 0.28, p < 0.05) and had the largest eyeblinks, especially in the left eye (r109 = 0.34, p < 0.001). Results suggest that general startle may represent a valid tool for studying the neural excitability underlying anxiety and emotional dysfunction in neurological and mental disorders.
Highlights
The startle reflex is a quick and automatic protective response elicited by an abrupt and intense stimulation
The present study aimed to demonstrate, in a large sample of 111 female participants, that part of the large interindividual variance in general startle reactivity is explained by anxiety levels
With the present experiment we aimed to demonstrate a relationship between anxiety levels and general startle amplitude
Summary
The startle reflex is a quick and automatic protective response elicited by an abrupt and intense stimulation. Amplitude of the general startle reflex showed a good intraindividual coherence across time (Larson et al, 2000), but it revealed a high inter-individual variability, which has been often considered from researchers as a task-irrelevant noise and subtracted by task-related responses or normalized among participants by T-score (equivalent to z-score) transformation (Berg and Balaban, 1999; Blumenthal et al, 2005; see for a review of emotion-related startle modulation response in clinical samples: Vaidyanathan et al, 2009) Instead, this variability in general startle reactivity showed a good correlation with the magnitude of threat-potentiated startle (Grillon and Baas, 2002; Bradford et al, 2014) and may reflect the resting state activity of brain areas, including both limbic and paralimbic structures, which have a key role both in the modulation of the startle reflex and in important processes such as sustained fear and anxiety.
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