Acoustic Blink Reflex Research Articles

Emotional reactivity related to the electrode position changes along anterio-posterior direction in subthalamic stimulation for Parkinson’s disease

Objectives Considering the functional organization of the subthalamic nucleus (STN), we hypothesized that STN-DBS might have a differential impact on emotional reactivity in relation to the electrode position within the STN. We aimed to assess this objectively using affective modulation of the acoustic blink reflex (ABR). Methods ABR elicited during the viewing of rewarding, fearful and neutral pictures was recorded in 10 off-medicated PD patients with the STN-DBS switched ON and OFF. The active electrode contact positions in the STN were determined on T1-weighted MRI. The relation of ABR magnitude on DBS electrode position was assessed using linear regression. Results The ABR magnitude from all picture categories was related to the electrode position in both the ON (p Conclusions The STN-DBS probably drove the electrode-position related effect on emotional activation along the anterio-posterior direction. This effect, however, was not stimulus category specific suggesting rather general increase in emotional arousal. Key message Emotional reactivity changes due to DBS showed anterio-posterior gradient within the STN.

Sex, Food and Threat: Startling Changes after Subthalamic Stimulation in Parkinson's Disease

BackgroundChanges in motivational processing may play a role in weight gain and other non-motor side effects in Parkinson's disease (PD) patients treated with deep brain stimulation of the subthalamic nucleus. Objective/hypothesisWe aimed to assess changes in aversive and appetitive motivational activation using modulation of the acoustic blink reflex (ABR) by rewarding and aversive stimuli. MethodsABR elicited during the viewing of erotic, food, aversive and neutral pictures was recorded in 11 off-medicated patients with the subthalamic stimulation switched ON and OFF, and in 11 control subjects. ResultsABR to erotic stimuli was larger in patients in the ON compared to the OFF condition and controls (P < 0.01). Aversive stimuli caused a larger increase in the ABR in patients with the ON condition than in controls (P < 0.05). Additionally, we found a negative correlation of the ABR magnitude to food pictures in the ON condition with weight gain following subthalamic stimulation (P < 0.01, after adjustment to OFF condition). ConclusionsOur results suggest that subthalamic stimulation affects motivational processing. Subthalamic stimulation may disturb appetitive engagement by erotic cues and increase aversive activation in PD patients. Additionally, postoperative weight gain may be related to changes in the processing of food cues due to subthalamic stimulation.

Augmented startle responses in opsoclonus-myoclonus syndrome

We report a 3-year-old boy with opsoclonus-myoclonus syndrome (OMS) who presented with exaggerated startle responses to unexpected auditory stimuli during an episode of myoclonic status. An augmented blink reflex was also observed clinically and electrophysiologically. Based on the assumption that hyperexcitability in the lower pontine tegmentum may be responsible for the acoustic startle and blink reflex in OMS, we considered that increased excitability of independent but neighboring structures, including the pontine paramedian reticular formation, may cause OMS symptoms.

Reciprocal modulation of eye‐blink and pinna‐flexion components of startle during reward anticipation

Because expectancies play a central role in current theories of dopaminergic neuron function, it is important to develop measures of reward anticipation processes. In the present study, reflexogenic bursts of white noise were presented to 39 healthy young adults as they awaited rewards and punishments in a gambling-like task. The rewards were small pieces of chocolate; the punishments, segments of bitter-tasting banana peel. Consistent with prior research on affective valence, postauricular reflexes were larger prior to rewards than punishments, whereas the reverse was true for acoustic blink reflexes. We theorized that potentiation of the postauricular reflex prior to consuming appetizing food is related to the priming of ear-retraction musculature during nursing in our remote ancestors.

Impaired Prepulse Inhibition and Prepulse-Elicited Reactivity but Intact Reflex Circuit Excitability in Unmedicated Schizophrenia Patients: a Comparison With Healthy Subjects and Medicated Schizophrenia Patients

Deficient sensorimotor gating as indexed by prepulse inhibition (PPI) of the startle response has been reported repeatedly in patients suffering from schizophrenia. According to the widely accepted "protective hypothesis," PPI reflects the protection of ongoing information processing against interference by other stimuli. Alternatively, it has been proposed that PPI might be regulated by startle reflex circuit excitability. In the present study, we evaluated these 2 conceptually divergent approaches underlying the regulation of PPI. To this end, we assessed sensorimotor gating as indexed by PPI, the reactivity to the prepulse-alone stimulus indexed as prepulse-elicited reactivity (PPER), and acoustic blink reflex excitability in terms of paired pulse suppression (PPS) within a single recording session in 13 unmedicated and 24 medicated (11 first break) schizophrenia patients in comparison to 43 healthy control subjects. The results showed that PPI was significantly reduced in unmedicated, but not in medicated schizophrenia patients. Furthermore, unmedicated patients could be distinguished from the medicated patients and control subjects in terms of PPER. In contrast to PPI, PPS did not differ between patients and control subjects. These findings are in line with the "protective hypothesis" of PPI and indicate that reduced sensorimotor gating in schizophrenia patients might be based on a reduced perception and/or processing of the prepulse stimulus. The extent to which PPER may or may not be causally associated with sensorimotor gating in schizophrenia has to be further investigated in human and animal studies.

Facilitation as well as inhibition of the blink reflex by a visual prepulse requires intact striate cortex

Objective The role of visual cortex in modulation of the human eye blink reflex was assessed. Methods Participants were 13 patients with unilateral striate cortex damage. Nonreflexogenic gratings were presented in their intact or blind hemifield prior to white noise or air puff blink-eliciting stimuli. Results Inhibition of reflex amplitude was observed at asynchronies ranging from about 120 to 600 ms for visible but not invisible prepulses. Facilitation by intact-hemifield gratings was observed for (1) the latency of the acoustic blink reflex, (2) the amplitude of the disynaptic cutaneous blink reflex, R1, and (3) the latency of voluntary hand-grip reactions to the reflexogenic stimuli. These facilitatory effects were absent on trials with blind-hemifield prepulses. Conclusions An intact V1 is required for prepulse facilitation as well as inhibition. Significance These results extend a popular model of sensorimotor gating deficits in schizophrenia.

Diagnostic potential of acoustic startle reflex, acoustic blink reflex, and electro-oculography in progressive supranuclear palsy: a prospective study.

We carried out a prospective study to analyze the diagnostic potential of acoustic startle reflex (ASR), acoustic blink reflex (ABR) and electro-oculography (EOG) in early stages of atypical parkinsonian syndrome. The study was carried out in a consecutive series of 41 patients clinically diagnosed as atypical parkinsonism (mean time from first symptoms of 38 months and follow-up of 26 months). The three procedures were carried out immediately after the first clinical evaluation. ASR and ABR were elicited by auditory stimuli while the patient was attending to a simple reaction time task. Outcome measures were: ASR (absence/presence, latency), ABR (absence/presence, latency) and EOG (suggestive/not suggestive of progressive supranuclear palsy [PSP]). Final clinical diagnosis was carried out by two neurologists blind to the neurophysiological results. A study of diagnostic sensitivity and odds ratio (OR) calculation for the PSP diagnosis was carried out. Neurophysiological examination showed the following sensitivity/specificity (%) for the diagnosis of PSP: ASR: 100/89; ABR 85/89; EOG 100/72. OR values were: ASR: 0.011; ABR: 0.037; EOG: 0.038. The three tests taken simultaneously showed a sensitivity of 100% and a specificity of 95%. The three neurophysiological tests investigated provided sensitive and specific measures with predictor value in early stages of atypical parkinsonian syndrome.

The Independent Effects of Attention and Lead Stimulus Properties on the Acoustic Blink Reflex

Abstract The effects of attention to a lead stimulus and of its sensory properties on modulation of the acoustic blink reflex were investigated. Participants performed a reaction time task cued by an acoustic or a visual lead stimulus. In Experiment 1, half the participants were presented with sustained lead stimuli. For the remainder, the lead stimulus was discrete and consisted of two brief presentations that marked the onset and offset of a stimulus-free interval. In Experiment 2, sustained lead stimuli were presented at a low or high intensity. The attentional demands of the task enhanced blink latency and magnitude modulation during acoustic and visual lead stimuli, with blink modulation being largest at a late point during the lead stimulus. Independent of the attentional effects, blink latency and magnitude modulation were larger during sustained than during discrete acoustic lead stimuli, whereas there was no difference for visual lead stimuli. Increases in the intensity of the lead stimulus enhanced blink modulation regardless of lead stimulus modality. Attention to a lead stimulus and the properties of the lead stimulus appear to have independent effects on blink reflex modulation.

Electromyographical differentiation between the acoustic blink and startle reflex. Implications for studies investigating startle behavior.

Recent evidence suggests that electromyographic activity in the orbicularis oculi muscle occurring in response to sudden acoustic stimuli consists of two overlapping components: the blink and the startle reflex. The aim of the present study was to identify these two components in acoustically elicited eyeblink responses and to analyze their differential modulation by weak acoustic prepulses. The prevalence, latency and amplitude characteristics of double EMG peaks in pulse-alone and prepulse-pulse trials (PP) with 30 ms and 100 ms interstimulus intervals were assessed in 16 healthy volunteers.EMG responses with two peaks were registered in 42.6 % of the pulse-alone trials and in 56.2 % of the PP30 and 48.7 % of the PP100 trials, respectively. Prepulse inhibition of the amplitude was greater for the second peak (14.2 % (P2) vs. -11.5 % (P1) in PP30 trials; 62.6 % (P2) vs. 32.3 % (P1) in PP100 trials), resulting also in higher P1/P2 amplitude ratios in prepulse-pulse trials (P1/P2: 62.9 % in pulse-alone, 92.6 % in PP30 and 100.1 % in PP100 trials). In conclusion, double peaks are a common phenomenon in human studies of acoustically elicited blink responses. It is postulated that the first peak represents the auditory blink reflex, whereas the second peak corresponds to the startle reflex, which may be more susceptible to prepulse inhibition. This complexity should be taken into account in clinical studies of the modulation of the startle reflex.

Blink Startle Modulation During Anticipation of Pleasant and Unpleasant Stimuli

Abstract The present research investigated blink startle modulation during the anticipation of pleasant, unpleasant, or neutral pictures. In Experiment 1 (N = 18), participants were presented with three different tone-picture pairings. Tones differed in pitch and were followed by pleasant, neutral or unpleasant pictures. Acoustic blink reflexes were elicited during some tones and during stimulus free intervals. Blink facilitation during tones that preceded pleasant and unpleasant pictures was larger than during the tone that preceded neutral pictures. Experiment 2 (N = 10) assessed whether this difference was due to a difference in the presentation frequency of the three conditions. No difference in blink facilitation between the conditions was found when pictures of flowers and mushrooms replaced the pleasant and unpleasant pictures, indicating that picture content was instrumental in causing the differential blink facilitation in Experiment 1. The results from Experiment 1 seem to indicate that startle modulation during the anticipation of pictorial material reflects the interest in or the arousal associated with the pictures rather than picture valence.

Fear conditioned potentiation of the acoustic blink reflex in patients with cerebellar lesions

OBJECTIVETo investigate whether the human cerebellum takes part in fear conditioned potentiation of the acoustic blink reflex.METHODSA group of 10 cerebellar patients (eight patients with lesions involving the medial cerebellum,...

Midazolam effects on prepulse inhibition of the acoustic blink reflex.

The eye-blink response following sudden acoustic noise bursts is part of the startle reflex. The magnitude of the startle response can be attenuated by presentation of a weak stimulus before the 'startle-eliciting' stimulus (prepulse inhibition, PPI). PPI is a stable finding in awake humans but may be altered by anaesthetic drugs. We investigated whether the application of benzodiazepines altered the magnitude of PPI in healthy male volunteers. In an open-label noncontrolled investigation, the effect of the benzodiazepine agonist midazolam on PPI was assessed in the absence and presence of the antagonist flumazenil. After an initial control period of 60 min three consecutive periods, each of 60 min, with progressively increasing concentrations of midazolam were studied (0. 02, 0.06, 0.14 mg kg-1 h-1 ). A final 60 min period during the administration of flumazenil (0.004 mg kg-1 h-1 ) and while the agonist was still present was also studied. Drug was administered intravenuously as a combination of bolus, 50% of total dose and continuous infusion over the 60 min period. Electromyographic (EMG) response of the right orbicularis oculi muscle was used to assess the startle response to noise bursts of 50 ms duration (95 dB(A)). Noise bursts were randomly preceded by nonstartling prepulses (800 Hz sinus, 50 ms duration, 65 dB(A), prepulse to noise interval 120 ms). The magnitude of PPI was calculated by dividing the EMG response to nonprepulsed stimuli by the response to prepulsed stimuli for each individual and period. Eleven subjects participated in the study, two of them were excluded from the statistical analysis because startle responses could not be reliably elicited (final sample size n=9). The magnitude of PPI was inversely related to the concentration of midazolam. This relationship was described by a sigmoidal Emax model, giving an Emax of 0.65+/-0.13, an ED50 of 33.9+/-10.9 ng ml-1 and gamma of 3.5+/-1.0. During infusion of flumazenil and in the presence of midazolam, the magnitude of PPI increased by 0.11 (95% CI, 0-0.22, P</=0.04), which is consistent with its mode of action as a benzodiazepine antagonist. In healthy male volunteers the magnitude of PPI varies according to agonism and antagonism of benzodiazepine receptors, suggesting that the assessment of PPI may be potentially useful to monitor the sedative effect of benzodiazepines in the clinical setting.

Fear‐Potentiated Startle in Humans: Effects of Anticipatory Anxiety on the Acoustic Blink Reflex

The effects of fear/anticipatory anxiety on the acoustic startle reflex were investigated in humans using a paradigm involving anticipation of electric shocks. The eyeblink component of the startle reflex, elicited by an abrupt auditory stimulus, was measured in 9 normal volunteers during either the anticipation of electric shocks (anticipatory anxiety) or periods in which no shocks were anticipated (safe period). The eyeblink was consistently higher in amplitude, and shorter in latency, during periods when the subjects anticipated shocks, compared to the safe periods. This effect could not be attributed solely to a reduction in habituation and was statistically significant before the subjects actually received any shock (a single 30 mA stimulation on the median nerve). These results indicate that anticipatory anxiety can be measured objectively in humans using the fear-potentiated startle reflex in a paradigm not actually requiring any shock. Because a great deal is known about the neuroanatomical and pharmacological mechanisms of fear-potentiated startle in laboratory animals, this test procedure may be especially useful in humans to investigate the neurobiological substrates of anxiety disorders and their pharmacological treatments.

Early selective attention effects on cutaneous and acoustic blink reflexes

In two experiments, selective modulation of the human blink reflex was examined by directing subjects to judge duration of the startling or nonstartling member of an acoustic-cutaneous stimulus pair. The startling stimulus was acoustic in the first experiment and cutaneous in the second. In both experiments, magnitude and onset latency were facilitated when the subjects attended to rather than away from the reflex-eliciting stimulus, although changes in cutaneous reflex size were insignificant. However, a nonselective inhibition of blink magnitude on warned relative to unwarned trials, associated with latency facilitation of the cutaneous reflex, was a stronger effect. The existence of both selective, concordant and nonselective, discordant changes in latency and magnitude could not be explained by a single mechanism. Heart rate changes also suggested that warning initiated some process in addition to attention to intake. The predictability of warned events may play a larger role than has previously been recognized.

The acoustic blink reflex: stimulus dependence, excitability and localizing value.

The acoustic blink reflex was examined in 26 subjects with open eyes and 20 subjects with closed eyes by means of an electrooculogram. Amplitude and excitability are highly dependent on the loudness of the stimulus used and on the opening or closure of the eyelids. Particularly if the eyes are closed, it may be necessary to use a stimulus of high (105-110 dB SPL) intensity (hand-clapping is often not loud enough). If an acoustic blink reflex can be elicited, it can be assumed that certain pontine and mesencephalic structures are intact.