Spontaneous Eye Blink Research Articles

Eye Blink Rates and Eyelid Twitches as a Non-Invasive Measure of Stress in the Domestic Horse.

Simple SummaryEye blink rate has been used as an indicator of stress in humans and, due to its non-invasive nature, could be useful to measure stress in horses. Horses exhibit both full and half blinks as well as eyelid twitches. We exposed 33 horses to stressful situations such as separation from herdmates, denied access to feed and sudden introduction of a novel object, and determined that full and half eye blinks decrease in these situations. Feed restriction was the most stressful for the horse as indicated by increased heart rate, restless behaviour and high head position. The decrease in eye blink rate during feed restriction was paralleled with an increase in eyelid twitches. There was no increase in eyelid twitches or heart rate with the other treatments indicating that the horses did not find these overly stressful, but they did focus their attention more during these situations. Observation of eye blinks and eyelid twitches can provide important information on the stress level of horses with a decrease in eye blinks and an increase in eyelid twitches in stressful environments.Physiological changes provide indices of stress responses, however, behavioural measures may be easier to determine. Spontaneous eye blink rate has potential as a non-invasive indicator of stress. Eyelid movements, along with heart rate (HR) and behaviour, from 33 horses were evaluated over four treatments: (1) control—horse in its normal paddock environment; (2) feed restriction—feed was withheld at regular feeding time; (3) separation—horse was removed from visual contact with their paddock mates; and (4) startle test—a ball was suddenly thrown on the ground in front of the horse. HR data was collected every five s throughout each three min test. Eyelid movements and behaviours were retrospectively determined from video recordings. A generalized linear mixed model (GLIMMIX) procedure with Sidak’s multiple comparisons of least squares means demonstrated that both full blinks (16 ± 12b vs. 15 ± 15b vs. 13 ± 11b vs. 26 ± 20a full blinks/3 min ± SEM; a,b differ p < 0.006) and half blinks (34 ± 15ab vs. 27 ± 14bc vs. 25 ± 13c vs. 42 ± 22a half blinks/3 min ± SEM; a,b,c differ p < 0.0001) decreased during feed restriction, separation and the startle test compared to the control, respectively. Eyelid twitches occurred more frequently in feed restriction (p < 0.0001) along with an increased HR (p < 0.0001). This study demonstrates that spontaneous blink rate decreases while eyelid twitches increase when the horse experiences a stressful situation.

Attentional blink and putative noninvasive dopamine markers: Two experiments to consolidate possible associations

Adaptive behavioral control involves a balance between top-down persistence and flexible updating of goals under changing demands. According to the metacontrol state model (MSM), this balance emerges from the interaction between the frontal and the striatal dopaminergic system. The attentional blink (AB) task has been argued to tap into the interaction between persistence and flexibility, as it reflects overpersistence—the too-exclusive allocation of attentional resources to the processing of the first of two consecutive targets. Notably, previous studies are inconclusive about the association between the AB and noninvasive proxies of dopamine including the spontaneous eye blink rate (sEBR), which allegedly assesses striatal dopamine levels. We aimed to substantiate and extend previous attempts to predict individual sizes of the AB in two separate experiments with larger sample sizes (N = 71 & N = 65) by means of noninvasive behavioral and physiological proxies of dopamine (DA), such as sEBR and mood measures, which are likely to reflect striatal dopamine levels, and color discrimination, which has been argued to tap into the frontal dopamine levels. Our findings did not confirm the prediction that AB size covaries with sEBR, mood, or color discrimination. The implications of this inconsistency with previous observations are discussed.

Is the Glasses-Free 3-Dimensional Display System More Effective for Complex Video-Assisted Thoracic Surgery? A Self-Controlled Study Ex Vivo.

Objective. Considering the demerits of a high-definition 2-dimensional (HD-2D) system, with its lack of stereopsis, and a conventional 3-dimensional (C-3D) system, which results in a dimmed image, we have recently developed a glasses-free 3-dimensional (GF-3D) display system for reconstruction surgeries such as video-assisted thoracic surgery (VATS) for tracheal reconstruction. Methods. Thoracic surgeons were invited to complete thoracoscopic continuous suture of a transected porcine trachea using the HD-2D, C-3D, and GF-3D systems on separate mornings in randomized order. The duration, numbers of stitches, and distance between every 2 stitches were recorded for every procedure. The surgeons' spontaneous eye blink rate was recorded for 5 minutes before the procedure and the last 5 minutes of the procedure. Results. Fifteen volunteers successfully completed the tracheal reconstruction procedures in this study. Both C-3D (0.403 ± 0.064 stitch/min, P < .001) and GF-3D (0.427 ± 0.079 stitch/min, P < .001) showed significant advantages in speed compared with HD-2D (0.289 ± 0.065 stitch/min). Both C-3D (2.536 ± 2.223 mm, P < .001) and GF-3D (2.603 ± 2.159 mm, P < .001) showed significant advantages in accuracy compared with HD-2D (3.473 ± 3.403 mm). Both HD-2D (1.240 ± 0.642, P < .001) and GF-3D (1.307 ± 0.894, P < .001) showed significant advantages in eye fatigue compared with C-3D (3.333 ± 1.44). Conclusions. All 3 available display systems are efficient for complex VATS. With the help of stereopsis, surgeons can achieve faster operation using C-3D and GF-3D systems in a thoracoscopic simulated setting. GF-3D may be a more effective display system for VATS reconstruction in terms of speed, accuracy, and eye fatigue during operations.

Objective assessment of blinking and facial expressions in Parkinson’s disease using a vertical electro-oculogram and facial surface electromyography

Objective: Hypomimia is a common and early symptom of Parkinson’s disease (PD), which reduces the ability of PD patients to manifest emotions. Currently, it is visually evaluated by the neurologist during neurological examinations for PD diagnosis, as described in task 3.2 of the Movement Disorder Society—Unified Parkinson’s Disease Rating Scale (MDS-UPDRS). Since such an evaluation is semi-quantitative and affected by inter-variability, this paper aims to measure the physiological parameters related to eye blink and facial expressions extracted from a vertical electro-oculogram (VEOG) and facial surface electromyography (fsEMG) to differentiate PD patients from healthy control subjects (HCs). Approach: The spontaneous eye blink rate-minute (sEBR), its maximum amplitude (BMP), and facial cutaneous muscle activity were measured in 24 PD patients and 24 HCs while the subjects looked at a visual-tester composed of three main parts: static vision, dynamic vision and reading silently. Specificity and sensitivity for each parameter were calculated. Main results: The VEOG and the fsEMG allowed the identification of some parameters related to eye blink and facial expressions (i.e. sEBR, BMP, frontal and peribuccal muscular activities), being able to distinguish between PD patients and HCs with high sensitivity and specificity. Significance: The demonstration that the combination of parameters related to eye blink and facial expressions can discriminate (with high accuracy) between PD patients versus HCs, thus resulting in a useful tool to support the neurologist in objective assessment of hypomimia for improving PD diagnosis.

Individual differences in baseline oculometrics: Examining variation in baseline pupil diameter, spontaneous eye blink rate, and fixation stability.

Individual differences in baseline oculometrics (baseline pupil diameter, spontaneous eye blink rate, fixation stability), and their relation with cognitive abilities, personality traits, and self-report assessments were examined. Participants performed a baseline eye measure in which they were instructed to stare at a fixation point onscreen for 5 min. Following the baseline eye measure, participants completed a questionnaire asking what they were thinking about during the baseline eye measure. Participants also completed various cognitive ability measures assessing working memory capacity, attention control, and off-task thinking. Finally, participants completed a number of questionnaires assessing personality, Attention Deficit/Hyperactivity Disorder symptomology, mind wandering, and morningness-eveningness. Overall, the vast majority of correlations with the baseline eye measures were weak and nonsignificant, suggesting that these associations may not be very robust. The results also demonstrated the importance of examining what participants are thinking about during the baseline measure. These results add to the growing body of findings suggesting inconsistent relations between different baseline eye measures and various individual differences constructs.

Familiarity revealed by involuntary eye movements on the fringe of awareness

Involuntary eye movements during fixation of gaze are typically transiently inhibited following stimulus onset. This oculomotor inhibition (OMI), which includes microsaccades and spontaneous eye blinks, is modulated by stimulus saliency and anticipation, but it is currently unknown whether it is sensitive to familiarity. To investigate this, we measured the OMI while observers passively viewed a slideshow of one familiar and 7 unfamiliar facial images presented briefly at 1 Hz in random order. Since the initial experiments indicated that OMI was occasionally insensitive to familiarity when the facial images were highly visible, and to prevent top-down strategies and potential biases, we limited visibility by backward masking making the faces barely visible or at the fringe of awareness. Under these conditions, we found prolonged inhibition of both microsaccades and eye-blinks, as well as earlier onset of microsaccade inhibition with familiarity. These findings demonstrate, for the first time, the sensitivity of OMI to familiarity. Because this is based on involuntary eye movements and can be measured on the fringe of awareness and in passive viewing, our results provide direct evidence that OMI can be used as a novel physiological measure for studying hidden memories with potential implications for health, legal, and security purposes.

Selective attention, not cognitive load, elicited fewer eyeblinks in a concealed information test

The concealed information test (CIT), a memory detection test, compares physiological responses to crime-related and crime-unrelated items. This study elucidated processes involving spontaneous eyeblinks during the CIT by manipulating participants’ intention to conceal. Thirty-four participants committed mock theft. In the CIT, wherein eyeblinks are measured simultaneously with autonomic responses, the secret group concealed the crime-related item, whereas the no-secret group did not. As a result, heart rate (HR) was modulated by the intention of concealment in autonomic measures, whereas the effect of concealment on the decrease of eyeblinks was not found to be significant. In addition, the latency of the first eyeblink was longer for the crime-related item in both groups. These results imply that CIT eyeblinks mainly involve the process of selective attention for the item, and the latency of the first eyeblink reflects a delay in attentional disengagement from the item. This study also suggested that there is still room for improvement in simultaneously measuring eyeblinks and autonomic responses in the CIT.

Examining the link between reward and response inhibition in individuals with substance abuse tendencies

BackgroundSubstance use problems are often characterized by dysregulation in reward sensitivity and inhibitory control. In line with this representation, the goal of this investigation was to determine how substance abuse tendencies among university students affect incentivized response inhibition. Additionally, this study examined whether striatal dopamine moderates the impact of substance use on response inhibition performance. MethodsThe sample included ninety-eight university students. Participants completed this prospective experimental study at an on-campus laboratory. All participants completed substance abuse and disinhibition subscales of the Externalizing Spectrum Inventory-Brief Form. Using a within-subjects design, participants then performed the Stop Signal Task under both neutral (unrewarded) and reward conditions, in which correct response cancellations resulted in a monetary reward. Striatal tonic dopamine levels were operationalized using spontaneous eyeblink rate. ResultsThe outcome measures were Stop Signal Reaction Time (SSRT) performance in the unrewarded and rewarded phases of the task. A hierarchical linear regression analysis, controlling for trait disinhibition, age, gender, and cigarette smoking status, identified an interactive effect of substance use and striatal dopamine levels on incentivized SSRT. Substance abuse tendencies were associated with slower SSRT and thus poorer inhibitory control under reward conditions among individuals with low levels of striatal dopamine (F = 7.613, p = .007). ConclusionsThis work has implications for research examining advanced drug use trajectories. In situations in which rewards are at stake, drug users with low tonic dopamine may be more motivated to seek those rewards at the expense of regulating inhibitory control.

Substance use is associated with reduced devaluation sensitivity.

Substance use has been linked to impairments in reward processing and decision-making, yet empirical research on the relationship between substance use and devaluation of reward in humans is limited. We report findings from two studies that tested whether individual differences in substance use behavior predicted reward learning strategies and devaluation sensitivity in a nonclinical sample. Participants in Experiment 1 (N = 66) and Experiment 2 (N = 91) completed subscales of the Externalizing Spectrum Inventory and then performed a two-stage reinforcement learning task that included a devaluation procedure. Spontaneous eye blink rate was used as an indirect proxy for dopamine functioning. In Experiment 1, correlational analysis revealed a negative relationship between substance use and devaluation sensitivity. In Experiment 2, regression modeling revealed that while spontaneous eyeblink rate moderated the relationship between substance use and reward learning strategies, substance use alone was related to devaluation sensitivity. These results suggest that once reward-action associations are established during reinforcement learning, substance use predicted reduced sensitivity to devaluation independently of variation in eyeblink rate. Thus, substance use is not only related to increased habit formation but also to difficulty disengaging from learned habits. Implications for the role of the dopaminergic system in habitual responding in individuals with substance use problems are discussed.

Spontaneous Eye Blink Patterns in Dry Eye: Clinical Correlations.

To evaluate spontaneous eye blink patterns and their correlations with clinical tests in dry eye disease (DED). Twenty-five DED patients and 25 healthy subjects were included in this prospective case-controlled study. Clinical evaluations included the Ocular Surface Disease Index (OSDI), lipid layer thickness (LLT), spontaneous eye blink pattern analysis, fluorescein tear film break-up time (FBUT), and so on. Eye blinks were recorded for 20 seconds with a high-speed camera. Eye blink patterns were divided into the following five phases: the eyelid closing phase (ECP), eyelid closed phase (CDP), early opening phase (EOP), late opening phase (LOP), and interblink intervals (IBI). The correlations between blink parameters and clinical tests were analyzed. Compared with the control group, mean ECP, CDP, and EOP were significantly longer in DED patients (P < 0.001, P = 0.029, and P < 0.001, respectively). DED patients also had significantly shorter LOP and blink intervals (both P < 0.001) and more partial blinks as compared with control subjects (P = 0.001). FBUT was negatively correlated with ECP (r = -0.618, P=0.001) and the number of partial blinks (r = -0.413, P = 0.040). There was a positive correlation between OSDI and the number of partial blinks (r = 0.446, P = 0.026). The LLT coefficient of variation (LLT-CV) also showed a positive correlation with ECP, CDP, and LOP (P = 0.001, P = 0.050, P = 0.049, respectively). Corneal and conjunctival staining was positively correlated with ECP, CDP, and the number of blinks (r = 0.449, P = 0.024; r = 0.526, P = 0.007; r = 0.456, P = 0.022, respectively) and negatively correlated with IBI (r = -0.420, P = 0.037). Partial blinks, prolonged eyelid closed time and short blink intervals were the three main characteristics of DED patients' spontaneous blink patterns.

The (Dis)Pleasures of Creativity: Spontaneous Eye Blink Rate during Divergent and Convergent Thinking Depends on Individual Differences in Positive and Negative Affect

AbstractPrevious research has demonstrated that individual differences in affect and motivation predict divergent and convergent thinking performance, two thinking processes involved in creative idea generation. Individual differences in affect and motivation also predict spontaneous eye blink rate (sEBR) during divergent and convergent thinking; and sEBR predicts divergent and convergent thinking performance. This study investigates experimentally whether the relationship between sEBR and divergent and convergent thinking depends on individual differences in affect and motivation. Eighty‐two participants completed the Emotion/motivation‐related Divergent and Convergent thinking styles Scale (EDICOS; G. Soroa et al., 2015), performed the alternative uses task (AUT; divergent thinking) or the remote associates task (RAT; convergent thinking), while their sEBR was captured with an eye‐tracker. The results showed that individual differences in positive affect positively correlated with sEBR for the AUT, whereas individual differences in negative affect positively correlated with sEBR for the RAT. Furthermore, the interaction between individual differences in positive and negative affect and sEBR predicted divergent and convergent thinking performance. The contribution of our study is therefore that individual differences in positive and negative affect can both positively correlate with sEBR during divergent and convergent thinking; and that this predicts divergent and convergent thinking performance.

Spontaneous eyeblinks are sensitive to sequential learning

Although sequential learning and spontaneous eyeblink rate (EBR) have both been shown to be tightly related to cerebral dopaminergic activity, they have never been investigated at the same time. In the present study, EBR, taken as an indirect marker of dopaminergic activity, was investigated in two resting state conditions, both before and after visuomotor sequence learning in a serial reaction time task (SRT) and during task practice. Participants’ abilities to produce and manipulate their knowledge about the sequential material were probed in a generation task. We hypothesized that the time course of spontaneous EBR might follow the progressive decrease of RTs during the SRT session. Additionally, we manipulated the structure of the transfer blocks as well as their respective order, assuming that (1) fully random trials might generate a larger psychophysiological response than an unlearned but structured material, and (2) a second (final) block of transfer might give rise to larger effects given that the sequential material was better consolidated after further practice. Finally, we tentatively hypothesized that, in addition to their online version, spontaneous EBR recorded during the pre- and post-learning resting sessions might be predictive of (1) the SRT learning curve, (2) the magnitude of the transfer effects, and (3) performance in the generation task. Results showed successful sequence learning with decreased accuracy and increased reaction times (RTs) in transfer blocks featuring a different material (random trials or a structured, novel sequence). In line with our hypothesis that EBR reflects dopaminergic activity associated with sequential learning, we observed increased EBR in random trials as well as when the second transfer block occurred at the end of the learning session. There was a positive relationship between the learning curve (RTs) and the slope of EBR during the SRT session. Additionally, inter-individual differences in resting and real-time EBR predicted the magnitude of accuracy and RTs transfer effects, respectively, but they were not related to participants’ performances during the generation task. Notwithstanding, our results suggest that the degree of explicit sequential knowledge modulates the association between the magnitude of the transfer effect in EBR and SRT performance. Overall, the present study provides evidence that EBR may represent a valid indirect psychophysiological correlate of dopaminergic activity coupled to sequential learning.

A potential link between gambling addiction severity and central dopamine levels: Evidence from spontaneous eye blink rates

Accumulating evidence points at similarities between substance use disorders (SUD) and gambling disorder on the behavioral and neural level. In SUD, attenuation of striatal D2/3-receptor availability is a consistent finding, at least for stimulating substances. For gambling disorder, no clear association with striatal D2/3-receptor availability has been unveiled so far. With its presumably negligible dopaminergic toxicity, possible differences in receptor availability in gambling disorder might constitute a vulnerability marker. Spontaneous eye blink rate (sEBR) is discussed as a potential proxy measure for striatal dopamine D2/3-receptor availability. Here we examined sEBR in 21 male problem gamblers and 20 healthy control participants. In addition, participants completed a screening questionnaire for overall psychopathology and self-reported measures of alcohol and nicotine consumption. We found no significant difference in sEBR between gamblers and controls. However, in gamblers, sEBR was negatively associated with gambling severity and positively associated with psychopathology. A final exploratory analysis revealed that healthy controls with low sEBR displayed higher alcohol and nicotine consumption than healthy participants with high sEBR. Although the exact association between dopamine transmission and sEBR is still debated, our findings reveal that sEBR is sensitive to inter-individual differences in gambling disorder severity in problem gamblers.

Contrast sensitivity and motion discrimination in cannabis users.

Cannabis use impairs visual attention; however, it is unclear whether cannabis use also impairs low level visual processing or whether low level visual deficits can be related to lower dopaminergic functioning found in cannabis users. To investigate whether spatiotemporal contrast sensitivity and motion discrimination under normal and low luminance conditions differ in cannabis users and non-users. Control (n = 20) and cannabis (n = 21) participants completed a visual acuity test, a saliva test and self-report measures. Spatial and temporal contrast thresholds, motion coherence thresholds for translational and radial motion and the spontaneous eye blink rate were then collected. Cannabis users showed decreased spatial contrast sensitivity under low luminance conditions and increased motion coherence thresholds under all luminance levels tested compared to non-users. No differences in temporal contrast sensitivity were found between the groups. Frequency of cannabis use correlated significantly and negatively with contrast sensitivity, both spatial and temporal, in the cannabis group and higher motion coherence thresholds for radial motion were also associated with more frequent cannabis use in this group. The eye blink rate was significantly lower in cannabis users compared to non-users. The present study shows that cannabis use is associated with deficits in low level visual processing. Such deficits are suggested to relate to lower dopamine, in a similar manner as in clinical populations. The implications for driving safety under reduced visibility (e.g. night) in abstaining cannabis users are discussed.

Influence of mouth and jaw movements on dynamics of spontaneous eye blink activity assessed during slitlamp biomicroscopy

BackgroundTo evaluate oculo‐mandibular interactions during evaluation of spontaneous eye blink rate (SEBR) of normal young adult human subjects while seated at a slitlamp.MethodsRepeat video recordings of five-minutes duration were made on 76 young adult emmetropic subjects aged 18–25-years. The subjects were instructed to direct their gaze horizontally toward a distant target with the entire cornea of the left eye illuminated with a broad beam cobalt blue light. Repeat recordings were made: (a) on the following day in silence in group one; (b) immediately in silence for group two; and (c) immediately either while holding their mouth open slightly or while responding to casual conversation for groups three and four.ResultsFor group one the averaged SEBR values for the first and second recordings were 13.5 and 14.6-blinks/minute, and similar results were obtained for group two if the subjects were relaxed (for example 13.9 and 12.0-blinks/minute). A slight, but statistically significant, time‐related decline in SEBR was usually noted. For non‐relaxed (restless) subjects exhibiting spontaneous mouth and jaw movements while being videographed, the averaged SEBR values were around 27-blinks/minute. For groups three and four, analyses of those individuals who managed to maintain a mouth open posture for the video recordings, the averaged SEBR was 7.2-blinks/minute, while those engaged in casual conversation had an averaged SEBR of 20.3-blinks/minute.ConclusionsMouth and jaw movements and a non‐relaxed state can substantially affect spontaneous eye blinking.

F180. Spontaneous Eye Blink Rate: A Good Proxy for Dopamine?

Dopamine is central to a number of cognitive functions and brain disorders. Given the cost of neurochemical imaging in humans, behavioral proxy measures of dopamine have gained in popularity in the past decade, such as spontaneous eye blink rate (sEBR). Increased sEBR is commonly associated with increased dopamine function based on pharmacological evidence and patient studies. Yet, this hypothesis has not been validated using in vivo measures of dopamine function in humans.

Effect of distance vision and refractive error on the spontaneous eye blink activity in human subjects in primary eye gaze

PurposeTo evaluate whether visual target character and visibility affects spontaneous eye blink rate (SEBR) in primary eye gaze and silence. MethodsVideo recordings were made of young healthy adults who were either emmetropic (n=32) or who wore spectacles for refractive error (range −4.75D and +4.50D (n=31). Emmetropes had 5min recordings made whilst seated and looking towards a distant whiteboard. For spectacle wearers, recordings were made whilst looking towards the whiteboard with a 35mm sized cross, and repeated after spectacle removal. The average number of eye blinks over 5min was assessed, and its intra-subject variability as the coefficient of variation (COV). ResultsOver 5min without a distance target, an average SEBR of 10.4blinks/min was observed in emmetropes with a of COV=38.1%, and a significant increase in SEBR over the 5th minute to 13.6blinks/min. Hyperopes being asked to look towards a distant target showed the essentially same blinking rate of 11.1/min with or without spectacle wear with the intra-subject variability (COV) being 21.3%. Myopic subjects showed a slightly higher SEBR if looking towards a target without their spectacles (12.4 vs. 11.0blinks/min), with the COV being 18.8%. ConclusionsThe studies indicate that some form of visual target could be useful to promote constancy of spontaneous eye blink activity over time, but that a distance visual target (when provided) does not need to be seen clearly.

Differentiating positive schizotypy and mania risk scales and their associations with spontaneous eye blink rate

Positive schizotypy and mania risk scales are strongly correlated, and both are linked to alterations in striatal dopamine. Previous research has not examined whether these risk scales form distinct factors or whether they are differentially related to other measures of psychopathology risk or striatal dopamine. In the current study (N = 596), undergraduate students completed both positive schizotypy and mania risk scales as well as scales assessing related psychopathology (i.e., negative and disorganized schizotypy; self-reported manic-like episodes). Additionally, we measured spontaneous eye blink rate, which has been consistently associated with striatal dopamine levels. Positive schizotypy and mania risk factors were strongly correlated (factor correlation = 0.73). However, a two-factor model with positive schizotypy and mania risk as separate factors fit significantly better than a one-factor risk model. After removing shared variance, only positive schizotypy was positively associated with both negative and disorganized schizotypy, and only mania risk was related to self-reported manic-like episodes. Furthermore, positive schizotypy was associated with decreased spontaneous eye blink rate, and mania risk was associated with increased spontaneous eye blink rate. Overall, these results suggest that positive schizotypy and mania risk can be distinguished as separate factors and that they might be differentially associated with striatal dopamine measures.

Spontaneous eye blink rate and dopamine synthesis capacity: preliminary evidence for an absence of positive correlation.

Dopamine is central to a number of cognitive functions and brain disorders. Given the cost of neurochemical imaging in humans, behavioural proxy measures of dopamine have gained in popularity in the past decade, such as spontaneous eye blink rate (sEBR). Increased sEBR is commonly associated with increased dopamine function based on pharmacological evidence and patient studies. Yet, this hypothesis has not been validated using in vivo measures of dopamine function in humans. To fill this gap, we measured sEBR and striatal dopamine synthesis capacity using [18F]DOPA PET in 20 participants (nine healthy individuals and 11 pathological gamblers). Our results, based on frequentist and Bayesian statistics, as well as region‐of‐interest and voxel‐wise analyses, argue against a positive relationship between sEBR and striatal dopamine synthesis capacity. They show that, if anything, the evidence is in favour of a negative relationship. These results, which complement findings from a recent study that failed to observe a relationship between sEBR and dopamine D2 receptor availability, suggest that caution and nuance are warranted when interpreting sEBR in terms of a proxy measure of striatal dopamine.

Eye blinks are related to auditory information processing: evidence from a complex speech perception task.

There is increasing evidence that spontaneous eye blinks are related to mental states and can predict performance in certain tasks because of their relation to dopaminergic activity. Moreover, it has been shown that eye blinks while performing visual tasks are preferably executed not before all available information and even the manual response has been processed and given. Thus, blinks provide a natural endpoint of visual information processing. In the present study, we investigate to what degree such functional assignment of eye blinks also applies when only auditory stimuli are processed. For that, we present blink analyses on data of an auditory stock price monitoring task to examine the timing and frequency of blinks relative to the temporal dynamics of the task and different kinds of available cues. Our results show that blinks are meaningfully rather than randomly paced, although no visual information has to be processed. Blinks are significantly accelerated if a no-go trial is indicated which made all the subsequent information irrelevant. Although the stimuli were exclusively auditory, blinks were mostly inhibited during stimulus presentation. Taken together, blinks depend on the information being presented and mark a distinct point in time at which this information is conclusively processed. These findings deliver further support for the usefulness of eyeblink analyses, independently of the modality of the information being processed.