The photic blink reflex as an index of photophobia.

Two recent studies of eye closure triggered by intense luminance increase suggest that this behavior reflects the melanopsin-based retinal activity known to underlie photophobia, the pathological aversion to light (Kardon, 2012; Kaiser et al., 2021). Early studies of the photic blink reflex (PBR) are reviewed to help guide future research on this possible objective index of photophobia. Electromyographic recordings of the lid-closure muscle, orbicularis oculi, reveal distinct bursts with typical onset latencies of 50 and 80 ms, R50 and R80, respectively. The latter component appears to be especially sensitive to visual signals from intrinsically photosensitive retinal ganglion cells (ipRGCs) and to prior trigeminal nociceptive stimuli. The authors argue that the R80's function, in addition to protecting the eyeballs from physical contact, is to shape the upper and lower eyelids into a narrow slit to restrict incoming light. This serves to prevent retinal bleaching or injury, while allowing continued visual function.

Unconsciously registered items reduce working memory capacity.

The assumption that the contents of consciousness correspond to those of working memory (WM) is challenged by evidence that stimuli masked from awareness can be retained for several seconds (Soto et al., 2011; Bergström & Eriksson, 2015). To assess whether conscious and unconscious items compete in a unitary WM store we conducted an experiment in which some of the memory items in an array were masked from conscious sight using continuous flash suppression (CFS) while others remained visible. After a retention interval, participants decided whether the probed item (either masked or visible) had changed its orientation. Behavioral results indicated that change detection for visible items was significantly impaired when masked items were present, suggesting that masked items either displaced or reduced the precision of visible items in WM. However, change detection for masked items was at chance levels, indicating that these items were not stored. The unsuccessful attempt to encode them may have drawn upon a common pool of attentional resources needed to retain or retrieve visible items. Contralateral Delay Activity, an EEG index of net WM load, failed to temporally localize this interference.

Learning to deal with delayed outcomes: EEG oscillatory and slow potentials during the prefeedback interval.

It is well established that the stimulus-preceding negativity (SPN) decreases in amplitude as a task is mastered, a phenomenon generally attributed to the reduction in anticipatory attention as feedback becomes less needed. Typically, the experiments supporting this assumption have used relatively short delays (<3 s). However, we found in a previous study that this decline in amplitude, although present during the 2.5-s prefeedback delay of a patterned key-pressing task, was absent with an 8-s delay. We reexamined this finding using a 6-s delay and found that the SPN diminished at frontal sites as participants learned a sequence of four keypress durations, but that this modulation was limited to the early half of the delay (maximum at 2 s). Decline of lateralized sensorimotor theta activity across trials was also limited to early portions of the delay. These findings suggest that processes other than anticipatory attention to feedback may be more relevant for explaining SPN diminution. Such processes could include adjustment and maintenance of action-outcome expectancies (e.g., forward models) during the prefeedback interval.

Vestigial auriculomotor activity indicates the direction of auditory attention in humans.

Unlike dogs and cats, people do not point their ears as they focus attention on novel, salient, or task-relevant stimuli. Our species may nevertheless have retained a vestigial pinna-orienting system that has persisted as a 'neural fossil' within in the brain for about 25 million years. Consistent with this hypothesis, we demonstrate that the direction of auditory attention is reflected in sustained electrical activity of muscles within the vestigial auriculomotor system. Surface electromyograms (EMGs) were taken from muscles that either move the pinna or alter its shape. To assess reflexive, stimulus-driven attention we presented novel sounds from speakers at four different lateral locations while the participants silently read a boring text in front of them. To test voluntary, goal-directed attention we instructed participants to listen to a short story coming from one of these speakers, while ignoring a competing story from the corresponding speaker on the opposite side. In both experiments, EMG recordings showed larger activity at the ear on the side of the attended stimulus, but with slightly different patterns. Upward movement (perking) differed according to the lateral focus of attention only during voluntary orienting; rearward folding of the pinna's upper-lateral edge exhibited such differences only during reflexive orienting. The existence of a pinna-orienting system in humans, one that is experimentally accessible, offers opportunities for basic as well as applied science.

Dogs, cats, monkeys and other animals perk their ears in the direction of sounds they are interested in. Humans and their closest ape relatives, however, appear to have lost this ability. Some humans are able to wiggle their ears, suggesting that some of the brain circuits and muscles that allow automatic ear movements towards sounds are still present. This may be a 'vestigial feature', an ability that is maintained even though it no longer serves its original purpose. Now, Strauss et al. show that vestigial movements of muscles around the ear indicate the direction of sounds a person is paying attention to. In the experiments, human volunteers tried to read a boring text while surprising sounds like a traffic jam, a baby crying, or footsteps played. During this exercise, Strauss et al. recorded the electrical activity in the muscles of their ears to see if they moved in response to the direction the sound came from. In a second set of experiments, the same electrical recordings were made as participants listened to a podcast while a second podcast was playing from a different direction. The individuals' ears were also recorded using high resolution video. Both sets of experiments revealed tiny involuntary movements in muscles surrounding the ear closest to the direction of a sound the person is listening to. When the participants tried to listen to one podcast and tune out another, they also made ear 'perking' movements in the direction of their preferred podcast. The results suggest that movements of the vestigial muscles in the human ear indicate the direction of sounds a person is paying attention to. These tiny movements could be used to develop better hearing aids that sense the electrical activity in the ear muscles and amplify sounds the person is trying to focus on, while minimizing other sounds.

Anterior insula activity and the effect of agency on the Stimulus-Preceding Negativity.

If you know that you are the author of a freely chosen action and that you bear responsibility for its outcome, then you are said to have "a sense of agency." When there is a delay between action and outcome, this response must be remembered if you are to learn from the experience. Previous studies have shown that the Stimulus-Preceding Negativity (SPN) recorded during the delay interval is larger under conditions that foster a sense of agency. In an EEG experiment (N = 27), we confirmed that the SPN is larger when participants have a choice between two responses in a gambling task as compared to when there is only a single button and the computer determines the monetary outcome. This SPN agency effect was largest over right prefrontal cortex and it did not vary significantly between trial blocks in which only gains or only losses were possible. Participants in a second experiment (N = 26) performed the same task while activity in anterior insular cortex, a known SPN generator, was measured via functional magnetic resonance image (fMRI). An essentially identical pattern of results was obtained: Activity was greater on choice than no-choice trials, especially for the right hemisphere, and no effect of contextual valence was observed. Although parallel observations such as these cannot warrant causal inference, our findings are consistent with the assumption that anterior insular cortex contributes to the effect of agency on the SPN.

Changes in the stimulus-preceding negativity and lateralized readiness potential during reinforcement learning.

According to reinforcement learning theory, dopamine-dependent anticipatory processes play a critical role in learning from action outcomes such as feedback or reward. To better understand outcome anticipation, we examined variation in slow cortical potentials and assessed their changes over the course of motor-skill acquisition. Healthy young adults learned a series of precisely timed, key press sequences. Feedback was delivered at a delay of either 2.5 or 8 s, to encourage use of either the striatally mediated, habit learning system or the hippocampus-dependent, episodic memory system, respectively. During the 2.5-s delay, the stimulus-preceding negativity (SPN) was shown to decline in amplitude across trials, confirming previous results from a perceptual categorization task (Morís, Luque, & Rodríguez-Fornells, 2013). This falsifies the hypothesis that SPN reflects specific outcome predictions, on the assumption that the ability to make such predictions should improve as a task is mastered. An SPN was also evident during the 8-s delay, but it increased in amplitude across trials. At the conclusion of the 8-s but not the 2.5-s prefeedback interval, a reversed-polarity lateralized readiness potential (LRP) was noted. It was suggested that this might indicate maintenance of an action representation for comparison with the feedback display. If so, this would constitute the first direct psychophysiological evidence for a popular hypothetical construct in quantitative models of reinforcement learning, the so-called eligibility trace.

Prepulse inhibition and facilitation of the postauricular reflex, a vestigial remnant of pinna startle.

If the postauricular reflex (PAR) is to be used effectively in studies of emotion and attention, its sensitivity to basic modulatory effects such as prepulse inhibition and facilitation must be determined. Two experiments were carried out with healthy young adults to assess the effects of transient and sustained visual prestimuli on the pinna-flexion response to trains of startle probes. In the first experiment, participants passively viewed a small white square. It was displayed from 1,000 ms prior to onset of a train of noise bursts until the end of that train. Relative to no-prepulse control trials, PAR amplitude was inhibited, possibly due to the withdrawal of attentional resources from the auditory modality. In the second experiment, participants performed a visual oddball task in which irrelevant trains of startle probes followed most briefly displayed task stimuli (checkerboards). Prepulse inhibition was observed when a transient stimulus preceded the first probe at a lead time of 100 ms. Amplitude facilitation was observed at longer lead times. In addition to documenting the existence of prepulse inhibition and facilitation, the data suggest that the PAR is not elicited by visual stimuli, that temporal expectancy does not influence its amplitude or latency, and that this vestigial microreflex is resistant to habituation. Results are interpreted in light of a recent theory that the human PAR is a highly degraded pinna startle, in which the reflex arc no longer includes the startle center (nucleus reticularis pontis caudalis).

Evidence for a vestigial pinna-orienting system in humans.

Although some people can voluntarily move their ears, overt reflexive control of the pinnae has been lost during the course of primate evolution. Humans and apes do not move their ears to express emotion, they do not defensively retract them when startled, and they do not point them at novel, salient, or task-relevant stimuli. Nevertheless, it is the thesis of this review that neural circuits for pinna orienting have survived in a purely vestigial state for over 25 million years. There are three lines of evidence: (1) Shifting the eyes hard to one side is accompanied by electromyographic (EMG) activity in certain ear muscles and by a barely visible (2-3 mm) curling of the dorsal edge of the pinna. (2) The capture of attention by a novel, unexpected sound emanating from behind and to one side has been found to trigger a weak EMG response in the muscle behind the corresponding ear. (3) Reflexive EMG bursts recorded during a selective attention task suggested that subjects were unconsciously attempting to orient their ears toward the relevant sounds. In addition to pinna orienting, the possibility that pinna startle might have survived in a vestigial state is also considered. It is suggested that the postauricular reflex to sudden, intense sounds constitutes a vestigial startle response, but that the reflex arc is dominated by a pathway that bypasses the main organizing center for startle.

Modulation of eyeblink and postauricular reflexes during the anticipation and viewing of food images.

One of the goals of neuroscience research on the reward system is to fractionate its functions into meaningful subcomponents. To this end, the present study examined emotional modulation of the eyeblink and postauricular components of startle in 60 young adults during anticipation and viewing of food images. Appetitive and disgusting photos served as rewards and punishments in a guessing game. Reflexes evoked during anticipation were not influenced by valence, consistent with the prevailing view that startle modulation indexes hedonic impact (liking) rather than incentive salience (wanting). During the slide-viewing period, postauricular reflexes were larger for correct than incorrect feedback, whereas the reverse was true for blink reflexes. Probes were delivered in brief trains, but only the first response exhibited this pattern. The specificity of affective startle modification makes it a valuable tool for studying the reward system.

The nursing hypothesis: an evolutionary account of emotional modulation of the postauricular reflex.

The postauricular reflex (PAR) is anomalous because it seems to be potentiated during positive emotions and inhibited during negative states, unlike eyeblink and other components of the startle reflex. Two evolutionary explanations based on simian facial emotion expressions were tested. Reflexes were elicited while 47 young adult volunteers made lip pursing or grimacing poses and viewed neutral, intimidating, or appetitive photos. The PAR was enhanced during appetitive slides, but only as subjects carried out the lip-pursing maneuver. These results support the nursing hypothesis, which assumes that infant mammals instinctively retract their pinnae while nursing in order to comfortably position the head. Appetitive emotions prime the ear-retraction musculature, even in higher primates whose postauricular muscles are vestigial.

Decomposition of warning effects in Parkinson's disease.

Neutral warning signals speed voluntary reactions by reducing temporal uncertainty and by triggering a brief burst of arousal. We attempted to isolate the phasic arousal mechanism in people with Parkinson's disease (PD) using a clock display to minimize temporal uncertainty. In this condition, the speeding of responses in a color-discrimination task by an accessory stimulus was the fully equivalent to the effect in age-matched control subjects. This indicates preserved phasic arousal in PD. Temporal preparation based on warning cues also appeared to be normal. By contrast, in a condition with high temporal uncertainty, the accessory stimulus (an air puff to the foot) impaired accuracy for the patients but not the neurologically normal subjects. The data are consistent with the view that PD disrupts internal but not external control of alertness.

Waiting to perceive: reward or punishment?

Neurobiological accounts of the dopaminergic reward system and psychophysiological explanations of the error-related negativity (ERN) both emphasize the comparison of expected versus actual outcome for voluntary actions. The stimulus-preceding negativity (SPN) constitutes a valuable index of that expectation, in that it has high temporal resolution and its anatomical, cognitive and affective correlates have been reasonably well characterized. This review links established findings regarding the SPN to current research on the dorsal and ventral attention systems, somatic marker hypothesis, ERN, the reward system and relevant neurological and psychiatric findings. Special emphasis is given to the pre-feedback SPN and its origin within anterior insular cortex.

Visual working memory deficits in patients with Parkinson's disease are due to both reduced storage capacity and impaired ability to filter out irrelevant information.

Given that Parkinson's disease broadly affects frontostriatal circuitry, it is not surprising that the disorder is associated with a reduction of working memory. We tested whether this reduction is due to diminished storage capacity or impaired ability to exclude task-irrelevant items. Twenty-one medication-withdrawn patients and 28 age-matched control subjects performed a visuospatial memory task while their electroencephalograms were recorded. The task required them to remember the orientations of red rectangles within the half of the screen that was cued while ignoring all green rectangles. Behavioural and electroencephalogram measures indicated that patients with Parkinson's disease were impaired at filtering out distracters, and that they were able to hold fewer items in memory than control subjects. The results support recent suggestions that the basal ganglia help control access to working memory.

Stimulus-preceding negativity is modulated by action-outcome contingency.

We investigated the relationship between action-outcome contingency and stimulus-preceding negativity (SPN), a motivationally sensitive event-related potential. Neuroimaging studies have shown that insular cortex (a known source of the SPN) is more activated prior to rewards that are contingent on prior correct action than rewards that are given gratuitously. We compared two gambling tasks, one in which the participant attempted to guess the profitable key-press option (choice) and one in which rewards were simply given at random (no-choice). The SPN that developed in anticipation of feedback was larger in the choice condition, especially at right anterolateral sites. These findings suggest that the SPN specifically reflects the expectation of response reinforcement, rather than anticipatory attention toward emotionally salient stimuli.

Compatibility between stimulated eye, target location and response location.

Responses to stimuli are faster when the stimulus location spatially corresponds to the required response (standard Simon effect). Recently, a similar effect has been observed with monocular stimuli. Responses were faster when the response location and the stimulated eye corresponded (monocular Simon effect). It has been suggested that distinct mechanisms may underlie these two Simon effects. Here, we attempted to study these two mechanisms simultaneously. For mean reaction time, a finding of perfect additivity was obtained. These behavioral data coupled with surface electrophysiological measures support the view that two different mechanisms contribute independently to the monocular and standard Simon effect.

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.

The speeding of voluntary reaction by a warning signal.

Warning signals can shorten reaction time (RT) via either a top-down mechanism, temporal attention, or a bottom-up one, phasic arousal. The goal of this review article is to identify the locus at which these processes influence RT. Electrophysiological and behavioral evidence indicate that the chronometric locus for both modulatory effects lies mainly within a narrow window at the center of the stimulus-response interval. This interval presumably encompasses late perceptual, response selection, and early motor processes. Phasic arousal is theorized to reduce the threshold for response selection within a circuit involving the supramarginal gyrus. A blind-sight study indicates that conscious, cortical level processing is necessary for temporal attention, at least when the warning signal is visual.

Separation of phasic arousal and expectancy effects in a speeded reaction time task via fMRI.

Sixteen neurologically normal volunteers performed a 2-choice speeded reaction time (RT) task in which the imperative was the change in color of a clock hand. During trial blocks with low temporal uncertainty (good clock condition), this imperative stimulus occurred at a fixed location (e.g., 2:00). In the bad clock condition, the clock was unpredictive of imperative onset. On half of both good and bad clock trials, a task-irrelevant, cutaneous accessory stimulus accompanied the imperative. The speeding of reactions by the accessory was associated with activation primarily in and near the supramarginal gyrus of the parietal lobe. Contrasts of good- versus bad-clock conditions revealed activation in a variety of perceptual, motor, and executive control regions. Apart from interactions within the cerebellum and left anterior insula, there was little overlap between structures influenced by the arousal and expectancy manipulations.

Closely spaced stressful life events precede the onset of benign essential blepharospasm and hemifacial spasm.

BACKGROUND: The purpose of this study was to assess the possible role of major stressful life events, complicated grief, and depression in the pathogenesis of benign essential blepharospasm (BEB) and hemifacial spasm (HFS). METHODS: This was a case-control study involving 23 participants with BEB/HFS and 23 control subjects, comparing the frequency of major stressful life events, depression on the Beck Depression Inventory-II, and complicated grief on the Inventory of Complicated Grief. RESULTS: There was no difference in the rate of depression or complicated grief between participants with BEB/HFS (57%) and control subjects (48%). Participants with BEB/HFS experienced a significantly (P = 0.0048) shorter time interval between two major stressful life events (median, 0.3 year) than did the control group (median, 3.0 years). The proportion of participants who had suffered two major stressful lifetime events separated by 1 year or less was significantly greater for participants with BEB/HFS than for control subjects (P = 0.0007). CONCLUSIONS: The onset of BEB and HFS was often preceded by a major lifetime stressor. The development of these conditions was significantly related to the number of stressful life events occurring within the preceding year rather than to the total number of stressful life events. Subjects who sustain closely spaced stressful life events may be at increased risk of developing BEB and HFS.