Vestibular prepulse inhibition of the human blink reflex.

OBJECTIVE: Auditory and somatosensory prepulses are commonly used to assess prepulse inhibition (PPI). The effect of a vestibular prepulse upon blink reflex excitability has not been hitherto assessed. METHODS: Twenty-two healthy subjects and two patients with bilateral peripheral vestibular failure took part in the study. Whole body yaw rotation in the dark provided a vestibular inertial prepulse. Blink reflex was electrically evoked after the end of the rotation. The amplitude of R1 and the area-under-the-curve (area) of the blink reflex R2 and R2c responses were recorded and analysed. RESULTS: A vestibular prepulse inhibited the R2 (p < 0.001) and R2c area (p < 0.05). Increasing the angular acceleration did not increase the R2 and R2c inhibition (p > 0.05). Voluntary suppression of the vestibulo-ocular reflex did not affect the magnitude of inhibition (p > 0.05). Patients with peripheral vestibular failure did not show any inhibition. CONCLUSIONS: Our data support a vestibular gating mechanism in humans. SIGNIFICANCE: The main brainstem nucleus mediating PPI - the pedunculopontine nucleus (PPN) - is heavily vestibular responsive, which is consistent with our findings of a vestibular-mediated PPI. Our technique may be used to interrogate the fidelity of brain circuits mediating vestibular-related PPN functions. Given the PPN's importance in human postural control, our technique may also provide a neurophysiological biomarker of balance.

The effect of sunglass filters on contrast sensitivity, monocular eye closure, and blinking rate in people with intermittent exotropia.

CLINICAL RELEVANCE: Transient monocular eye closure and photosensitivity under bright light have been reported in people with intermittent exotropia (IXT). The exact mechanism of these symptoms has not been established. BACKGROUND: This study examines the effect of sunglass filters on contrast sensitivity (CS), transient monocular eye closure, and blinking rate under bright light in people with IXT. METHODS: Forty participants with IXT and complaints of photosensitivity were included in the study. The binocular CS test was performed under mesopic and photopic conditions with and without glare, and with and without two filters with different grades of light transmission (filter 1: 44-80%; filter 2: 20-43% light transmittance). The effect of two filters on transient eye closure, contrast sensitivity, and blinking rate was assessed under bright light. Also, participants were divided into 3 groups based on their degree of control of fusion (good, fair, and poor control). RESULTS: The mean age of the participants was 12.0 years ± 8.0 (standard deviation) (range: 7-40 years). There was no significant difference between the age (p = 0.139), stereopsis (p = 0.134), as well as the near and far degree of deviation (p = 0.516, and p = 0.237) between the three groups of fusion control. Under mesopic conditions with glare, mean binocular CS was significantly higher with filters (p < 0.001). Without filters, 57.5% of the participants exhibited monocular eye closure under a photopic setting with additional glare. No participant showed eye closure using filter 2. People in the poor control group showed exodeviation before monocular eye closure (62.5% without filter and 12.5% with filter 1, p = 0.01). The blinking rate decreased from 36.0 ± 4.0 blinks per minute without filter to 21.0 ± 3.0 using filter 1, and 20.0 ± 3.0 with filter 2. CONCLUSION: In people with IXT, wearing sunglass filters of different transmittance reduces monocular eye closure and blinking rate under bright light. To improve these symptoms, sunglasses can be considered for IXT.

Harnessing technology to measure individual differences in spatial thinking in early childhood from a relational developmental systems perspective.

According to the Relational Developmental Systems perspective, the development of individual differences in spatial thinking (e.g., mental rotation, spatial reorientation, and spatial language) are attributed to various psychological (e.g., children's cognitive strategies), biological (e.g., structure and function of hippocampus), and cultural systems (e.g., caregiver spatial language input). Yet, measuring the development of individual differences in spatial thinking in young children, as well as the psychological, biological, and cultural systems that influence the development of these abilities, presents unique challenges. The current paper outlines ways to harness available technology including eye-tracking, eye-blink conditioning, MRI, Zoom, and LENA technology, to study the development of individual differences in young children's spatial thinking. The technologies discussed offer ways to examine children's spatial thinking development from different levels of analyses (i.e., psychological, biological, cultural), thereby allowing us to advance the study of developmental theory. We conclude with a discussion of the use of artificial intelligence.

Olfaction modulates cortical arousal independent of perceived odor intensity and pleasantness.

Throughout history, various odors have been harnessed to invigorate or relax the mind. The mechanisms underlying odors' diverse arousal effects remain poorly understood. We conducted five experiments (184 participants) to investigate this issue, using pupillometry, electroencephalography, and the attentional blink paradigm, which exemplifies the limit in attentional capacity. Results demonstrated that exposure to citral, compared to vanillin, enlarged pupil size, reduced resting-state alpha oscillations and alpha network efficiency, augmented beta-gamma oscillations, and enhanced the coordination between parietal alpha and frontal beta-gamma activities. In parallel, it attenuated the attentional blink effect. These effects were observed despite citral and vanillin being comparable in perceived odor intensity, pleasantness, and nasal pungency, and were unlikely driven by semantic biases. Our findings reveal that odors differentially alter the small-worldness of brain network architecture, and thereby brain state and arousal. Furthermore, they establish arousal as a unique dimension in olfactory space, distinct from intensity and pleasantness.

Exploring novel SNPs and candidate genes associated with seed allometry in Pisum sativum L.

Seed size is an important agronomic trait that indicates seed quality. In legumes, pods with equal and larger seeds remain the first preference of farmers and consumers. Genetic understanding related to seed size including seed allometric traits has been limited in the case of peas. To fill this void the findings presented here used the genome-wide association studies (GWAS) to identify novel candidate gene(s) putatively linked with seed size in Pisum sativum L. The study was conducted on 240 Pea Single Plant Plus Collection (PSPPC) panels of pea germplasm. Allometric traits measured included seed_length, seed_width, seed_thickness, seed_volume, seed_biomass, and seed_biomass by volume (SB_V). GWAS was performed using the Genome Association and Prediction Integrated Tool (GAPIT) on R-studio. The Bayesian information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) model provided significant single nucleotide polymorphisms (SNPs) linked with all the seed allometric traits. When analyzed the genomic regions of these SNPs provided a list of candidate genes that may be related to seed size. The present study thus provides a list of significant SNPs and relevant genes viz. Psat2g072000 for seed_length, Psat4g104320 for seed_width, Psat6g125800 and Psat6g125840 for seed_thickness, Psat6g228320 for seed_volume, Psat2g143920 for seed_biomass, and Psat2g120400 for SB_V which may prove useful in the improvement of pea seed size using breeding programs or CRISPR intervention. Understanding the genetic basis of seed size could lead to crop development with desirable seed characteristics, such as equal and larger-sized seeds with maximum yield and higher nutritional content. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-024-01499-6.

Electrophysiological features of the peripheral neuropathy in patients with pathologic biallelic RFC1 repeat expansions.

INTRODUCTION/AIMS: Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is caused by RFC1 expansions. Sensory neuronopathy, polyneuropathy, and involvement of motor, autonomic, and cranial nerves have all been described with RFC1 expansions. We aimed to describe the electrodiagnostic features of patients with RFC1 expansions through multimodal electrophysiological investigations. METHODS: Thirty-five patients, with a median age of 70 years, and pathologic biallelic repeat expansions in the RFC1 gene, were tested for motor and sensory nerve conduction, flexor carpi radialis (FCR) and soleus H-reflexes, blink reflex, electrochemical skin conductance, sympathetic skin response (SSR), and heart rate variability with deep breathing (HRV). RESULTS: Only 16 patients (46%) exhibited the full clinical CANVAS spectrum. Distal motor amplitudes were normal in 30 patients and reduced in the legs of five patients. Distal sensory amplitudes were bilaterally reduced in a non-length dependent manner in 30 patients. Conduction velocities were normal. Soleus H-reflexes were abnormal in 19/20 patients of whom seven had preserved Achilles reflexes. FCR H-reflexes were absent or decreased in amplitude in 13/14 patients. Blink reflex was abnormal in 4/19 patients: R1 latencies for two patients and R2 latencies for two others. Fourteen out of 31 patients (45%) had abnormal results in at least one autonomic nervous system test, either for ESC (12/31), SSR (5/14), or HRV (6/19). DISCUSSION: Less than half of the patients with RFC1 expansions exhibited the full clinical CANVAS spectrum, but nearly all exhibited typical sensory neuronopathy and abnormal H-reflexes. Involvement of small nerve fibers and brainstem neurons was less common.

Investigating the influence of eye-catching effect on mental workload in highway tunnel entrances: a comprehensive analysis of eye blink behavior.

OBJECTIVE: The objective of this study was to investigate the relationship between eye-catching effects and mental workload at highway tunnel entrances. Specifically, the study aimed to analyze drivers' eye blink behavior to gain a comprehensive understanding of how visual attraction at tunnel entrances affects cognitive workload. METHODS: 50 participants were recruited for the naturalistic driving experiment. Four different visually attractive driving scenarios (baseline, landscape-style architecture, tip slogan, and billboard) were selected. Eye-tracking technology was utilized to record and analyze the eye blink behavior of participating drivers. Various metrics, including blink frequency, blink duration, inter-blink interval, and pupil diameter after a blink, were measured and compared across different scenarios. RESULTS: The results of the study demonstrated significant differences in drivers' eye blink behavior across the different experimental scenarios, indicating the influence of visual attraction conditions on mental workload. The presence of eye-catching stimuli (landscape-style architecture, tip slogan, and billboard scenarios) at tunnel entrances resulted in decreased blink frequency, shorter blink duration, longer inter-blink intervals, and larger pupil diameter after a blink compared to when no specific eye-catching stimuli were present (baseline condition). These findings suggest that visual attractions capture drivers' attention, leading to increased cognitive workload and attentional demands. CONCLUSIONS: The findings of this study contribute to the existing literature on driver attention and mental workload, particularly in relation to eye-catching effect in tunnel environments. The presence of eye-catching stimuli at tunnel entrances can distract drivers and increase their mental workload, potentially compromising driving performance and safety. It is crucial for transportation authorities and designers to carefully consider the design and placement of visual attractions in tunnel entrances to minimize distraction and cognitive workload. By doing so, driving safety and performance can be enhanced in tunnel entrances.

[Practical Application of Intelligent Vision Measurement System Based on Deep Learning].

To comprehensively assess the true visual function of clinical dry eye patients and the comprehensive impact of blinking characteristics on functional vision of the human eye, an intelligent vision measurement system has been designed and developed to detect and analyze blinks from the side. The system employs deep learning keypoint recognition technology to analyze eyelid features from a lateral perspective. It presents the data of identified key points for the upper and lower eyelids in a line chart format and annotates the trough of each blink. By setting benchmark values, the system automatically calculates the proportion of complete and incomplete blinks in the tested individuals. The results indicate that the system is stable in performance and accurate in measurement, successfully achieving the anticipated design objectives. It thereby provides reliable technical support for future clinical applications.

Transcranial alternating current stimulation can modulate the blink reflex excitability. Effects of a 10- and 20-Hz tACS session on the blink reflex recovery cycle in healthy subjects.

BACKGROUND: The blink reflex excitability, assessed through paired electrical stimuli responses, has been modulated using traditional non-invasive neurostimulation techniques. Recently, transcranial Alternating Current Stimulation (tACS) emerged as a tool to modulate brain oscillations implicated in various motor, perceptual, and cognitive functions. This study aims to investigate the influence of 20-Hz and 10-Hz tACS sessions on the primary motor cortex and their impact on blink reflex excitability. MATERIALS AND METHODS: Fifteen healthy volunteers underwent 10-min tACS sessions (intensity 1 mA) with active/reference electrodes placed over C4/Pz, delivering 20-Hz, 10-Hz, and sham stimulation. The blink reflex recovery cycle (BRrc) was assessed using the R2 amplitude ratio at various interstimulus intervals (ISIs) before (T0), immediately after (T1), and 30 min post-tACS (T2). RESULTS: Both 10-Hz and 20-Hz tACS sessions significantly increased R2 ratio at T1 (10-Hz: p = 0.02; 20-Hz: p < 0.001) and T2 (10-Hz: p = 0.01; 20-Hz: p < 0.001) compared to baseline (T0). Notably, 20-Hz tACS induced a significantly greater increase in blink reflex excitability compared to sham at both T1 (p = 0.04) and T2 (p < 0.001). CONCLUSION: This study demonstrates the modulatory effect of tACS on trigemino-facial reflex circuits, with a lasting impact on BRrc. Beta-band frequency tACS exhibited a more pronounced effect than alpha-band frequency, highlighting the influential role of beta-band oscillations in the motor cortex on blink reflex excitability modulation.

Oculomotor behaviors in youth with an eating disorder: findings from a video-based eye tracking task.

BACKGROUND: The oculomotor circuit spans many cortical and subcortical areas that have been implicated in psychiatric disease. This, combined with previous findings, suggests that eye tracking may be a useful method to investigate eating disorders. Therefore, this study aimed to assess oculomotor behaviors in youth with and without an eating disorder. METHODS: Female youth with and without an eating disorder completed a structured task involving randomly interleaved pro-saccade (toward at a stimulus) and anti-saccade (away from stimulus) trials with video-based eye tracking. Differences in saccades (rapid eye movements between two points), eye blinks and pupil were examined. RESULTS: Youth with an eating disorder (n = 65, Mage = 17.16 ± 3.5 years) were compared to healthy controls (HC; n = 65, Mage = 17.88 ± 4.3 years). The eating disorder group was composed of individuals with anorexia nervosa (n = 49), bulimia nervosa (n = 7) and other specified feeding or eating disorder (n = 9). The eating disorder group was further divided into two subgroups: individuals with a restrictive spectrum eating disorder (ED-R; n = 43) or a bulimic spectrum eating disorder (ED-BP; n = 22). In pro-saccade trials, the eating disorder group made significantly more fixation breaks than HCs (F(1,128) = 5.33, p = 0.023). The ED-BP group made the most anticipatory pro-saccades, followed by ED-R, then HCs (F(2,127) = 3.38, p = 0.037). Groups did not differ on rate of correct express or regular latency pro-saccades. In anti-saccade trials, groups only significantly differed on percentage of direction errors corrected (F(2, 127) = 4.554, p = 0.012). The eating disorder group had a significantly smaller baseline pupil size (F(2,127) = 3.60, p = 0.030) and slower pro-saccade dilation velocity (F(2,127) = 3.30, p = 0.040) compared to HCs. The ED-R group had the lowest blink probability during the intertrial interval (ITI), followed by ED-BP, with HCs having the highest ITI blink probability (F(2,125) = 3.63, p = 0.029). CONCLUSIONS: These results suggest that youth with an eating disorder may have different oculomotor behaviors during a structured eye tracking task. The oculomotor behavioral differences observed in this study presents an important step towards identifying neurobiological and cognitive contributions towards eating disorders.

Video based eye tracking is a promising method for studying differences between individuals with and without a psychiatric disease of interest. While some studies have explored oculomotor behaviors in individuals with an eating disorder, much remains unknown. The present study investigated saccades (fast eye movements between two points), eye blinks and pupil responses between female youth (aged 10­25 years) with and without an eating disorder during a pro-saccade (looking at a point) and anti-saccade (looking away from a point) eye tracking task. Individuals with an eating disorder made more pro-saccade guesses, had a smaller pupil size and blinked less before a trial started. In individuals with a restrictive type eating disorder (e.g., anorexia nervosa restrictive type), pupil responses may have a relationship with emotional dysregulation (poorly regulated emotional responses). Overall, this study represents an important step towards identifying oculomotor behavior differences in individuals with an eating disorder compared to controls.

Blink-induced changes in pupil dynamics are consistent and heritable.

Pupil size and blink rates are heritable but the extent to which they interact with one another has not been properly investigated. Though changes in pupil size due to eye blinks have been reported, they are considered a pupillary artifact. In this study we used the HCP 7T fMRI dataset with resting state eye-tracking data obtained in monozygous and dizygous twins to assess their heritability and their interactions. For this purpose, we characterized the pupil dilation (positive peak) and constriction (negative peak) that followed blink events, which we describe as blink-induced pupillary response (BIPR). We show that the BIPR is highly consistent with a positive dilatory peak (D-peak) around 500ms and a negative constricting peak (C-peak) around 1s. These patterns were reproducible within- and between- subjects across two time points and differed by vigilance state (vigilant versus drowsy). By comparing BIPR between monozygous and dizygous twins we show that BIPR have a heritable component with significant additive genetic (A) and environmental (E) factors dominating the structural equation models, particularly in the time-domain for both D- and C-peaks and amplitude domain for the C-peak. (a2 between 42-49%). Blink duration, pupil size and blink rate were also found to be highly heritable (a2 up to 62% for pupil size). Our study documents an association between BIPR and wakefulness and indicates that BIPR should not be treated as a coincidental artefact, but part of a larger oculomotor system that we label here as Oculomotor Adaptive System, OAS, that is genetically determined.

Adaptive Filtering with Fitted Noise Estimate (AFFiNE): Blink Artifact Correction in Simulated and Real P300 Data.

(1) Background: The electroencephalogram (EEG) is frequently corrupted by ocular artifacts such as saccades and blinks. Methods for correcting these artifacts include independent component analysis (ICA) and recursive-least-squares (RLS) adaptive filtering (-AF). Here, we introduce a new method, AFFiNE, that applies Bayesian adaptive regression spline (BARS) fitting to the adaptive filter's reference noise input to address the known limitations of both ICA and RLS-AF, and then compare the performance of all three methods. (2) Methods: Artifact-corrected P300 morphologies, topographies, and measurements were compared between the three methods, and to known truth conditions, where possible, using real and simulated blink-corrupted event-related potential (ERP) datasets. (3) Results: In both simulated and real datasets, AFFiNE was successful at removing the blink artifact while preserving the underlying P300 signal in all situations where RLS-AF failed. Compared to ICA, AFFiNE resulted in either a practically or an observably comparable error. (4) Conclusions: AFFiNE is an ocular artifact correction technique that is implementable in online analyses; it can adapt to being non-stationarity and is independent of channel density and recording duration. AFFiNE can be utilized for the removal of blink artifacts in situations where ICA may not be practically or theoretically useful.

Blink rate during saccadic eye movements: insights from patients with chronic pain.

Chronic pain (CP) significantly impacts quality of life and poses an increasing economic burden on healthcare systems worldwide. This study investigates the relationship between blink rate during saccadic eye movements and pain perception in patients with CP. Ninety-two patients with CP (24 men, 68 women) were assessed using eye-tracking technology during horizontal and vertical saccadic tasks. Pain perception was evaluated using the Central Sensitization Inventory - Part A and the McGill Pain Questionnaire, and anxiety levels were measured using the State-Trait Anxiety Inventory. The results revealed a significant correlation between blink rates in horizontal and vertical tasks (ρ = 0.668, P < 0.001). However, there was no correlation between blink rate and age, pain perception, or anxiety scores. Conversely, measures of pain perception were positively correlated with each other and with anxiety scores. These findings suggest that while blink rate may reflect oculomotor function, it is not directly influenced by pain perception or anxiety in patients with CP. The present study highlights the potential of eye tracking for the comprehensive assessment and management of patients with CP.

The homogenous hippocampus: How hippocampal cells process available and potential goals.

We present here a view of the firing patterns of hippocampal cells that is contrary, both functionally and anatomically, to conventional wisdom. We argue that the hippocampus responds to efference copies of goals encoded elsewhere; and that it uses these to detect and resolve conflict or interference between goals in general. While goals can involve space, hippocampal cells do not encode spatial (or other special types of) memory, as such. We also argue that the transverse circuits of the hippocampus operate in an essentially homogeneous way along its length. The apparently different functions of different parts (e.g. memory retrieval versus anxiety) result from the different (situational/motivational) inputs on which those parts perform the same fundamental computational operations. On this view, the key role of the hippocampus is the iterative adjustment, via Papez-like circuits, of synaptic weights in cell assemblies elsewhere.

Modulation of the somatosensory blink reflex under fear.

OBJECTIVE: This study evaluated the isolated and combined effects of fear and PPS paradigms on SBR. METHOD: The prospective study was conducted with healthy participants. After stimulation of the right median nerve at the wrist, bilateral recordings were randomized under the following conditions: First experiment (with the right hand on the chair armrest): i. baseline recordings, ii. while watching fearful facial expressions from the Karolinska Emotional Faces battery (fear), iii. post-watching (post-fear), iv. while watching neutral facial expressions from the same battery (neutral), v. Immediately after viewing (post-neutral). Second experiment (right hand 2 cm away from the right eye, PPS): i. reference condition (PPS), ii. while watching fearful facial expressions (PPS-fear), iii. while watching neutral facial expressions (PPS-neutral). In each condition, SBR latency, area, duration, and amplitudes were measured and compared between conditions. RESULTS: We included 16 participants. SBR could be recorded in 11 (mean age:30.7 ± 5.2, F/M:5/6). First experiment: SBR amplitude was significantly reduced in fear condition (p = 0.008), and SBR area was reduced considerably in fear and post-fear conditions (p = 0.004) compared to the baseline. Second experiment: The SBR area was higher in the PPS (p = 0.009) compared to the baseline and even higher in the fearPPS compared to the PPS (p = 0.038). In neutral or PPS-neutral conditions, the area of the SBR did not change significantly. CONCLUSION: Fear suppressed SBR, but fear increased SBR when a threat stimulus was present. The findings were unrelated to habituation or attention, indicating cortical-amygdala-bulbar connections.

Confidence for intrusion errors during the attentional blink depends on target-defining features.

Research surrounding the attentional blink phenomenon - a deficit in responding to the second of two temporally proximal stimuli when presented 150-500 ms after the first - has used a wide variety of target-defining and response features of stimuli. The typical U-shape curve for absolute performance is robust, surviving across most stimulus features, and therefore changes in performance are discussed as dynamics in an attentional system that are nonspecific a stimulus type. However, the patterns of errors participants make might not show the same robustness, and participants' confidences in these errors might differ - potentially suggesting the involvement of different attentional or perceptual mechanisms. The present research is a comparison of error patterns and confidence in those errors when letter target stimuli are defined by either the color of the letter, the presence of a surrounding annulus, or the color of the annulus. Across three experiments, we show that participants erroneously report stimuli that are further away from T2 and they are similarly confident in specifically their post-target errors as their correct responses when annuli define targets, but not when color of the letter defines targets. Experiment 3 provides some evidence to suggest that this error pattern and associated confidence is time-dependent when the color of the annulus defines the target, but not when the color of the letter defines the target. These results raise questions concerning the nature of the errors and possibly the mechanisms of the attentional blink phenomenon itself.

Assessing blink dynamics with non-noticeable method.

PURPOSE: The purpose of the study was to demonstrate the feasibility of blink dynamics with a contactless, non-noticeable method without any visible light being reflected to the participant's eye by the device, and to investigate the blink dynamics parameters in 39 participants whose blink dynamics were examined with this method. It was also aimed to explain the potential of corneal topography devices for non-noticeable blink dynamics and elucidate some tips to device manufacturers to make them practical. METHODS: A one-minute real-time video image in the meibography module of the scheimpflug camera-based corneal topography device was recorded in the slow motion mode of the mobile phone. Detailed analysis of blink dynamics was made by advancing the video images manually at 10 ms intervals. Lid Closing Time (LCT), Lid Opening Time (LOT), third Interblink Interval times (IBI(3)), fifth Interblink Interval times (IBI(5)), Number of Blinks Per Minute (NoB), Number of Complete Blinks Per Minute (NoCB), Number of Incomplete Blinks Per Minute (NoICB) were investigated. RESULTS: The average NoB, NoCB, and NoICB (blinks/minute) with ± standard deviation (SD) values were found to be 22.9 ± 14.4; 14.5 ± 12.4 and 8.4 ± 8, respectively. The average IBI(3) time(seconds) with ± SD was measured as 3.4 ± 4.5. The average IBI(5) time (seconds) with ± SD was 3.9 ± 3.7 The average LCT time (milliseconds) with ± SD was found to be 91.9 ± 36.9 in the 4 different blinks analyzed. The average LOT time (milliseconds) with ± SD was found to be 582.6 ± 196.5 in the 3 different blinks analyzed. CONCLUSIONS: Blink dynamics can be examined in detail with corneal topography devices in a non-contact, no visible light, and most importantly, non-noticeable manner. Existing video imaging modules of corneal topography devices have the potential to investigate blink dynamics. It is anticipated that the clinical use of blink dynamics, which can be performed practically, will increase, particularly in the monitoring of ocular surface and neurological diseases.

Correlation between bioluminescent blinks and swimming behavior in the splitfin flashlight fish Anomalops katoptron.

BACKGROUND: The light organs of the splitfin flashlight fish Anomalops katoptron are necessary for schooling behavior, to determine nearest neighbor distance, and to feed on zooplankton under dim light conditions. Each behavior is coupled to context-dependent blink frequencies and can be regulated via mechanical occlusion of light organs. During shoaling in the laboratory individuals show moderate blink frequencies around 100 blinks per minute. In this study, we correlated bioluminescent blinks with the spatio-temporal dynamics of swimming profiles in three dimensions, using a stereoscopic, infrared camera system. RESULTS: Groups of flashlight fish showed intermediate levels of polarization and distances to the group centroid. Individuals showed higher swimming speeds and curved swimming profiles during light organ occlusion. The largest changes in swimming direction occurred when darkening the light organs. Before A. katoptron exposed light organs again, they adapted a nearly straight movement direction. CONCLUSIONS: We conclude that a change in movement direction coupled to light organ occlusion in A. katoptron is an important behavioral trait in shoaling of flashlight fish.

Attentional Bias, Pupillometry, and Spontaneous Blink Rate: Eye Characteristic Assessment Within a Translatable Nicotine Cue Virtual Reality Paradigm.

Background: Incentive salience processes are important for the development and maintenance of addiction. Eye characteristics such as gaze fixation time, pupil diameter, and spontaneous eyeblink rate (EBR) are theorized to reflect incentive salience and may serve as useful biomarkers. However, conventional cue exposure paradigms have limitations that may impede accurate assessment of these markers. Objective: This study sought to evaluate the validity of these eye-tracking metrics as indicators of incentive salience within a virtual reality (VR) environment replicating real-world situations of nicotine and tobacco product (NTP) use. Methods: NTP users from the community were recruited and grouped by NTP use patterns: nondaily (n=33) and daily (n=75) use. Participants underwent the NTP cue VR paradigm and completed measures of nicotine craving, NTP use history, and VR-related assessments. Eye-gaze fixation time (attentional bias) and pupillometry in response to NTP versus control cues and EBR during the active and neutral VR scenes were recorded and analyzed using ANOVA and analysis of covariance models. Results: Greater subjective craving, as measured by the Tobacco Craving Questionnaire-Short Form, following active versus neutral scenes was observed (F1,106=47.95; P<.001). Greater mean eye-gaze fixation time (F1,106=48.34; P<.001) and pupil diameter (F1,102=5.99; P=.02) in response to NTP versus control cues were also detected. Evidence of NTP use group effects was observed in fixation time and pupillometry analyses, as well as correlations between these metrics, NTP use history, and nicotine craving. No significant associations were observed with EBR. Conclusions: This study provides additional evidence for attentional bias, as measured via eye-gaze fixation time, and pupillometry as useful biomarkers of incentive salience, and partially supports theories suggesting that incentive salience diminishes as nicotine dependence severity increases.

Changes in blink reflex after simultaneous supraorbital and mental nerve stimulations in healthy subjects.

Background/aim: In this study, we investigated the blink reflex (BR) after simultaneous and asynchronous stimulation of two trigeminal nerve branches. The objective was to characterize the physiology of trigeminal and facial circuits. Materials and methods: We performed three sets of experiments: recording BR response i. after supraorbital nerve stimulation (SON), after mental nerve stimulation (MN), and after simultaneous SON and MN stimulation (SON+MN) in 18 healthy individuals; ii. after MN (at an intensity eliciting BR response) preceding SON at various interstimulus intervals (ISIs) in seven healthy subjects; iii after MN (at sensory threshold) preceding SON at various ISIs. We compared the magnitudes of early and late responses. Results: The R1 amplitude after simultaneous SON+MN stimulation was greater than responses after single stimulation of the same branches. After simultaneous stimulations, the R2 and R2c areas under the curve (AUC) were smaller than the arithmetic sums of R2 and R2c AUC obtained after single stimulations. The second experiment provided a recovery excitability curve. In the third step, we obtained facilitation of R1 and inhibition of late responses. Conclusion: The SON+MN stimulation caused an increased R1 circuit excitability compared to the arithmetic sum of the single stimulations; however, magnitudes of late responses did not potentiate. Thus, we have provided evidence for R1 circuit enhancement by simultaneous stimulation in humans, whereas modulation of late responses exhibited a recovery curve similar to that shown for paired SON stimulation.