9/9/2023 0 Comments Blinkk suicideWhen partitioned into low (n = 16) and high (n = 17) reactive groups, the high reactive group showed a highly significant decrease in SBR during the IT period compared to baseline (11.1 ± 1.09 blinks per min to 6.2 ± 0.95 blinks per min, t 1,30 = − 2.9, p = 0.008) and a significant increase in SBR from baseline during the CT period (11.1 ± 1.09 blinks per min to 15.6 ± 1.71 blinks per min, t 1,30 = 2.7, p = 0.012). Using the horse as a model species, the aim of this study was twofold, firstly, to validate SBR as a putative measure of stress against conventional measures of stress (HRV and salivary cortisol), and secondly, to assess the timing and consistency of the SBR response during a stress event. This suggests that the SBR response to stress could vary depending on (1) when it is measured in relation to the stressor exposure and (2) the type of stressor. Potentially threatening stimuli may require cognitive effort to verify it as a threat thus reducing SBR at the early stage of stressor presentation. Human studies have shown a reduction in SBR during periods of attention and cognitive effort 20, 22, 23, 24, 25. The latter reflects this neurotransmitter’s functional role in eliciting motivation and learning processes during homeostatic behavioural responses to stress 17, 18.Īlthough the majority of evidence demonstrates that SBR increases during stress 19, 20 other work in horses has reported a decrease in SBR when presented with a potentially stressful event 21. SBR significantly increases in monkeys through the sub-cutaneous injection of dopamine agonists (apomorphine) and significantly blocked with dopamine antagonists (sulpiride) 16 and CNS dopamine levels significantly increase during stressful events. The link between SBR and stress appears to be mediated via dopaminergic activity. during punctuation pauses whilst reading 12), during pauses while listening to a speech 13 and also during information retrieval and memory 14, 15. Blinks also reflect cognitive processes during attention, with blink rate increasing when attentional demand is low (e.g. Spontaneous blinks have several functions, they are essential for corneal lubrication and also appear to be important for resetting eye movements during the correction of fixation errors 11. Spontaneous blink rate (SBR) has previously been used to measure stress responses in humans and may provide a non-invasive method for measuring stress in a range of species 10. The results are also not instantly available, requiring at least some degree of processing and analysis. The primary disadvantage associated with these methods is that they require specialist equipment and training in how to collect and/or analyse the data. Conventional methods of quantifying stress include measuring plasma and saliva cortisol levels 2, 3, 4, eye temperature 5, 6, heart rate and heart rate variability 7, 8, 9. Measuring animal stress is fundamentally important to ensuring reasonable levels of animal welfare 1. We have demonstrated that SBR is a valid fast alternative measure of stress in horses, but the initial 'startle' response must be considered when using this parameter as a measure of animal stress. For the entire sample, SBR correlated with heart rate variability and salivary cortisol. For horses reactive to clipping, the initial reduction in SBR was followed by an increase above baseline whereas the SBR of the non-reactive horses quickly returned to baseline. For the entire sample, there was a reduction in SBR (startle response) during the first minute of clipping. SBR was measured before and during a low-stress event (sham clipping) and compared with heart rate variability and salivary cortisol. Here we investigated the use of SBR as a measure of stress in the domestic horse. Spontaneous blink rate (SBR) has previously been used to measure stress responses in humans and may provide a non-invasive method for measuring stress in other animal species. Conventional methods of quantifying stress (cortisol levels, heart rate/heart rate variability) require specialist equipment and are not instantly available. Measuring animal stress is fundamentally important for assessing animal emotional state and welfare.
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