Effects of startle on cognitive performance and physiological activity revealed by fNIRS and thermal imaging

Abstract

Sudden and threatening stimuli can trigger a startle reflex, a stereotyped physiological response that may lead to a brief cognitive incapacitation. Better understanding this reaction would be beneficial to safety-critical occupational domains. We characterized some physiological correlates of the startle response while participants completed a difficult task (Toulouse N-back task) tapping executive functions. During the task, loud and threatening sounds were presented unpredictably to trigger a startle reflex. Brain activity and facial skin temperature were measured in 34 participants using functional near-infrared spectroscopy (fNIRS) and functional infrared thermal imaging (fITI), respectively. In the high difficulty condition, participants were generally less efficient, but their performance improved slightly following startle in the high difficulty condition. Brain activity in the right prefrontal cortex was also higher following startle, potentially reflecting a compensatory overactivation to sustain performance. Interestingly, higher trait-anxiety was associated with lower task performance, still following startle in the high difficulty condition. Finally, we found a decrease in temperature of the right eye and right cheek as well as an increase in the nose temperature following startle. These results underscore the complexity of startle-induced cognitive and physiological dynamics, which may have implications for occupational settings where managing sudden stressors is crucial.

Keywords: Auditory startle; Executive control network; Facial temperature; Mental workload; fITI; fNIRS.

Fig. 1

Score at the NASA task load index questionnaire administered after the TNT for each difficulty condition. Error bars represent the standard error of the mean. *** p < .001.

Fig. 2

Performance at the TNT. Error bars represent the standard error of the mean. ** p < .01; *** p < .001.

Fig. 3

Association between trait anxiety and performance at the TNT. The smooth line represents the 95% confidence interval of the regression line.

Fig. 4

HbO changes during the TNT as a function of type of sound. Error bars represent the standard error of the mean.

Fig. 5

Mean temperature changes relative to baseline following sound onset in the different face regions.

Fig. 6

Toulouse N-back task (TNT) comprising 60-second blocks of mental calculation alternating between the 0-back and the 2-back condition (14 blocks total) ending with a 30-second rest period.

Fig. 7

Illustration of the experimental setup. The TNT task is displayed on the screen.

Fig. 8

fNIRS montage.

Fig. 9

Face landmarks and their surrounding areas in which temperature changes from baseline were averaged.