Evoked compound action potential (ECAP)-controlled closed-loop spinal cord stimulation in an experimental model of neuropathic pain in rats.

BACKGROUND: Preclinical models of spinal cord stimulation (SCS) are lacking objective measurements to inform translationally applicable SCS parameters. The evoked compound action potential (ECAP) represents a measure of dorsal column fiber activation. This measure approximates the onset of SCS-induced sensations in humans and provides effective analgesia when used with ECAP-controlled closed-loop (CL)-SCS systems. Therefore, ECAPs may provide an objective surrogate for SCS dose in preclinical models that may support better understanding of SCS mechanisms and further translations to the clinics. This study assessed, for the first time, the feasibility of recording ECAPs and applying ECAP-controlled CL-SCS in freely behaving rats subjected to an experimental model of neuropathic pain. METHODS: Adult male Sprague-Dawley rats (200-300 g) were subjected to spared nerve injury (SNI). A custom-made six-contact lead was implanted epidurally covering T11-L3, as confirmed by computed tomography or X-ray. A specially designed multi-channel system was used to record ECAPs and to apply ECAP-controlled CL-SCS for 30 min at 50 Hz 200 µs. The responses of dorsal column fibers to SCS were characterized and sensitivity towards mechanical and cold stimuli were assessed to determine analgesic effects from ECAP-controlled CL-SCS. Comparisons between SNI rats and their controls as well as between stimulation parameters were made using omnibus analysis of variance (ANOVA) tests and t-tests. RESULTS: The recorded ECAPs showed the characteristic triphasic morphology and the ECAP amplitude (mV) increased as higher currents (mA) were applied in both SNI animals and controls (SNI SCS-ON and sham SCS-ON). Importantly, the use of ECAP-based SCS dose, implemented in ECAP-controlled CL-SCS, significantly reduced mechanical and cold hypersensitivity in SNI SCS-ON animals through the constant and controlled activation of dorsal column fibers. An analysis of conduction velocities of the evoked signals confirmed the involvement of large, myelinated fibers. CONCLUSIONS: The use of ECAP-based SCS dose implemented in ECAP-controlled CL-SCS produced analgesia in animals subjected to an experimental model of neuropathic pain. This approach may offer a better method for translating SCS parameters between species that will improve understanding of the mechanisms of SCS action to further advance future clinical applications.

EgoActive: Integrated Wireless Wearable Sensors for Capturing Infant Egocentric Auditory-Visual Statistics and Autonomic Nervous System Function 'in the Wild'.

There have been sustained efforts toward using naturalistic methods in developmental science to measure infant behaviors in the real world from an egocentric perspective because statistical regularities in the environment can shape and be shaped by the developing infant. However, there is no user-friendly and unobtrusive technology to densely and reliably sample life in the wild. To address this gap, we present the design, implementation and validation of the EgoActive platform, which addresses limitations of existing wearable technologies for developmental research. EgoActive records the active infants' egocentric perspective of the world via a miniature wireless head-mounted camera concurrently with their physiological responses to this input via a lightweight, wireless ECG/acceleration sensor. We also provide software tools to facilitate data analyses. Our validation studies showed that the cameras and body sensors performed well. Families also reported that the platform was comfortable, easy to use and operate, and did not interfere with daily activities. The synchronized multimodal data from the EgoActive platform can help tease apart complex processes that are important for child development to further our understanding of areas ranging from executive function to emotion processing and social learning.

A perceptual field test in object experts using gaze-contingent eye tracking.

A hallmark of expert object recognition is rapid and accurate subordinate-category recognition of visually homogenous objects. However, the perceptual strategies by which expert recognition is achieved is less known. The current study investigated whether visual expertise changes observers' perceptual field (e.g., their ability to use information away from fixation for recognition) for objects in their domain of expertise, using a gaze-contingent eye-tracking paradigm. In the current study, bird experts and novices were presented with two bird images sequentially, and their task was to determine whether the two images were of the same species (e.g., two different song sparrows) or different species (e.g., song sparrow and chipping sparrow). The first study bird image was presented in full view. The second test bird image was presented fully visible (full-view), restricted to a circular window centered on gaze position (central-view), or restricted to image regions beyond a circular mask centered on gaze position (peripheral-view). While experts and novices did not differ in their eye-movement behavior, experts' performance on the discrimination task for the fastest responses was less impaired than novices in the peripheral-view condition. Thus, the experts used peripheral information to a greater extent than novices, indicating that the experts have a wider perceptual field to support their speeded subordinate recognition.

The efficacy of sensory neural entrainment on acute and chronic pain: A systematic review and meta-analysis.

Background: Changes to the power of neural oscillations in cortical and sub-cortical structures can change pain perception. Rhythmic sensory stimulation is a non-invasive method that can increase power in specific frequencies of neural oscillations. If the stimulation frequency targets those frequencies related to pain perception, such as alpha or theta frequencies, there can be a reduction in perceived pain intensity. Thus, sensory neural entrainment may provide an alternative to pharmacological intervention for acute and chronic pain. This review aimed to identify and critically appraise the evidence on the effectiveness of sensory entrainment methods for pain perception. Methods: We undertook a systematic search across Medline, Embase, PsycInfo, Web of Science and Scopus in November 2020 to identify studies investigating the efficacy of sensory entrainment on adults. We assessed studies for their quality using the PRISMA checklist. A random-effects model was used in a meta-analysis to measure the effect of entrainment on pain perception. Results: Our systematic review yielded nine studies fitting the search criteria. Studies investigated the effect of visual and auditory entrainment on pain intensity rating, electrophysiological markers of pain and amount of analgesia needed during surgery. The meta-analysis suggests that alpha (8-13 Hz) sensory entrainment is effective for acute pain perception, whereas theta (4-7 Hz) entrainment is effective for chronic pain. Conclusions: Although there is heterogeneity in the current evidence, our review highlights the potential use of sensory entrainment to affect acute and chronic pain. Further research is required regarding the timing, duration and frequency of the stimulation to determine the best application for maximum efficacy.

Seven-months-old infants show increased arousal to static emotion body expressions: Evidence from pupil dilation.

Human body postures provide perceptual cues that can be used to discriminate and recognize emotions. It was previously found that 7-months-olds' fixation patterns discriminated fear from other emotion body expressions but it is not clear whether they also process the emotional content of those expressions. The emotional content of visual stimuli can increase arousal level resulting in pupil dilations. To provide evidence that infants also process the emotional content of expressions, we analyzed variations in pupil in response to emotion stimuli. Forty-eight 7-months-old infants viewed adult body postures expressing anger, fear, happiness and neutral expressions, while their pupil size was measured. There was a significant emotion effect between 1040 and 1640 ms after image onset, when fear elicited larger pupil dilations than neutral expressions. A similar trend was found for anger expressions. Our results suggest that infants have increased arousal to negative-valence body expressions. Thus, in combination with previous fixation results, the pupil data show that infants as young as 7-months can perceptually discriminate static body expressions and process the emotional content of those expressions. The results extend information about infant processing of emotion expressions conveyed through other means (e.g., faces).

Feeling the music: The feel and sound of songs attenuate pain.

Background: Extensive research has demonstrated that music and touch can separately attenuate perceived pain intensity. However, little research has investigated how auditory and tactile stimulation can synergistically enhance pain attenuation by music. In the current study, we investigated whether tactile stimulation can enhance music-induced analgesia for noxious force stimulation on the fingertip. Methods: We systematically applied force to 34 listeners' fingertips to induce pain. We then compared the force measurement (in Newton) that gave rise to the same perceived moderate pain intensity when listeners were presented their self-selected liked or disliked song with auditory-only, tactile-only and auditory-tactile stimulation. Higher force indicated less perceived pain. The tactile stimulation were low-frequency modulations extracted from the songs and presented as vibrations on the wrist. Results: The results showed a significant interaction between song preference and stimulation condition. Listeners had higher force measurements at the same moderate pain for their liked compared to disliked song only in the auditory-tactile condition. They also had higher force measurements for their liked song with auditory-tactile stimulation compared to the other remaining conditions except for the liked song with auditory-only stimulation. Conclusions: The addition of tactile stimulation enhanced music-induced analgesia which reduced subjective pain intensity. The findings suggest that combined auditory and tactile stimulation may increase the affective content of self-selected preferred music, which may stimulate affective and motivation mechanisms which inhibit pain transmission.

The effect of magnetic resonance imaging on mercury release from dental amalgam at 3T and 7T.

OBJECTIVES: To measure mercury release from standardised hydroxyapatite/amalgam constructs during MRI scanning and investigate the impact of static field strength and radiofrequency (RF) power on mercury release. METHODS: Amalgam was placed into 140 hydroxyapatite disks and matured for 14-days in artificial saliva. The solution was replaced, and samples split into five groups of 28 immediately prior to MRI. One group had no exposure, and the remainder were exposed to either a 3T or 7T MRI scanner, each at high and low RF power. Mercury concentration was measured by inductively coupled plasma mass spectrometry. Groups were compared using one-way ANOVA, and two-way ANOVA for main effects/ interaction of field strength/ RF power. RESULTS: Mercury concentration was increased in the 7T groups (high/ low: 15.43/ 11.33 ng mL-1) and 3T high group (3.59) compared to control (2.44). MRI field strength significantly increased mercury release (p < .001) as did RF power (p = .030). At 3T, mercury release was 20.3 times lower than during maturation of dental amalgam, and for the average person an estimated 1.50 ng kg-1 of mercury might be released during one 3T investigation; this is substantially lower than the tolerable weekly intake of 4,000 ng kg-1. CONCLUSION: Mercury release from amalgam shows a measurable increase following MRI, and the magnitude changes with magnetic field strength and RF power. The amount of mercury released is small compared to release during amalgam maturation. Amalgam mercury release during MRI is unlikely to be clinically meaningful and highly likely to remain below safe levels.

Three- and six-year-old children are sensitive to natural body expressions of emotion: An event-related potential emotional priming study.

Body movements provide a rich source of emotional information during social interactions. Although the ability to perceive biological motion cues related to those movements begins to develop during infancy, processing those cues to identify emotions likely continues to develop into childhood. Previous studies used posed or exaggerated body movements, which might not reflect the kind of body expressions children experience. The current study used an event-related potential (ERP) priming paradigm to investigate the development of emotion recognition from more naturalistic body movements. Point-light displays (PLDs) of male adult bodies expressing happy or angry emotional movements while narrating a story were used as prime stimuli, whereas audio recordings of the words "happy" and "angry" spoken with an emotionally neutral prosody were used as targets. We recorded the ERPs time-locked to the onset of the auditory target from 3- and 6-year-old children, and we compared amplitude and latency of the N300 and N400 responses between the two age groups in the different prime-target conditions. There was an overall effect of prime for the N300 amplitude, with more negative-going responses for happy PLDs compared with angry PLDs. There was also an interaction between prime and target for the N300 latency, suggesting that all children were sensitive to the emotional congruency between body movements and words. For the N400 component, there was only an interaction among age, prime, and target for latency, suggesting an age-dependent modulation of this component when prime and target did not match in emotional information. Overall, our results suggest that the emergence of more complex emotion processing of body expressions occurs around 6 years of age, but it is not fully developed at this point in ontogeny.

Bird expertise does not increase motion sensitivity to bird flight motion.

While motion information is important for the early stages of vision, it also contributes to later stages of object recognition. For example, human observers can detect the presence of a human, judge its actions, and judge its gender and identity simply based on motion cues conveyed in a point-light display. Here we examined whether object expertise enhances the observer's sensitivity to its characteristic movement. Bird experts and novices were shown point-light displays of upright and inverted birds in flight, or upright and inverted human walkers, and asked to discriminate them from spatially scrambled point-light displays of the same stimuli. While the spatially scrambled stimuli retained the local motion of each dot of the moving objects, it disrupted the global percept of the object in motion. To estimate a detection threshold in each object domain, we systematically varied the number of noise dots in which the stimuli were embedded using an adaptive staircase approach. Contrary to our predictions, the experts did not show disproportionately higher sensitivity to bird motion, and both groups showed no inversion cost. However, consistent with previous work showing a robust inversion effect for human motion, both groups were more sensitive to upright human walkers than their inverted counterparts. Thus, the result suggests that real-world experience in the bird domain has little to no influence on the sensitivity to bird motion and that birds do not show the typical inversion effect seen with humans and other terrestrial movement.

A Search Advantage for Horizontal Targets in Dynamic Displays.

Several lines of evidence point to the existence of a visual processing advantage for horizontal over vertical orientations. We investigated whether such a horizontal advantage exists in the context of top-down visual search. Inspired by change detection studies, we created displays where a dynamic target -- a horizontal or a vertical group of five dots that changed contrast synchronously -- was embedded within a randomly flickering grid of dots. The display size (total dots) varied across trials, and the orientation of the target was constant within interleaved blocks. As expected, search was slow and inefficient. Importantly, participants were almost a second faster finding horizontal compared to vertical targets. They were also more efficient and more accurate during horizontal search. Such findings establish that the attentional templates thought to guide search for known targets can exhibit strong orientation anisotropies. We discuss possible underlying mechanisms and how these might be explored in future studies.

Ensemble coding of crowd speed using biological motion.

The accurate perception of human crowds is integral to social understanding and interaction. Previous studies have shown that observers are sensitive to several crowd characteristics such as average facial expression, gender, identity, joint attention, and heading direction. In two experiments, we examined ensemble perception of crowd speed using standard point-light walkers (PLW). Participants were asked to estimate the average speed of a crowd consisting of 12 figures moving at different speeds. In Experiment 1, trials of intact PLWs alternated with trials of scrambled PLWs with a viewing duration of 3 seconds. We found that ensemble processing of crowd speed could rely on local motion alone, although a globally intact configuration enhanced performance. In Experiment 2, observers estimated the average speed of intact-PLW crowds that were displayed at reduced viewing durations across five blocks of trials (between 2500 ms and 500 ms). Estimation of fast crowds was precise and accurate regardless of viewing duration, and we estimated that three to four walkers could still be integrated at 500 ms. For slow crowds, we found a systematic deterioration in performance as viewing time reduced, and performance at 500 ms could not be distinguished from a single-walker response strategy. Overall, our results suggest that rapid and accurate ensemble perception of crowd speed is possible, although sensitive to the precise speed range examined.

Detection of Simulated Tactile Gratings by Electro-Static Friction Show a Dependency on Bar Width for Blind and Sighted Observers, and Preliminary Neural Correlates in Sighted Observers.

The three-dimensional micro-structure of physical surfaces produces frictional forces that provide sensory cues about properties of felt surfaces such as roughness. This tactile information activates somatosensory cortices, and frontal and temporal brain regions. Recent advances in haptic-feedback technologies allow the simulation of surface micro-structures via electro-static friction to produce touch sensations on otherwise flat screens. These sensations may benefit those with visual impairment or blindness. The primary aim of the current study was to test blind and sighted participants' perceptual sensitivity to simulated tactile gratings. A secondary aim was to explore which brain regions were involved in simulated touch to further understand the somatosensory brain network for touch. We used a haptic-feedback touchscreen which simulated tactile gratings using digitally manipulated electro-static friction. In Experiment 1, we compared blind and sighted participants' ability to detect the gratings by touch alone as a function of their spatial frequency (bar width) and intensity. Both blind and sighted participants showed high sensitivity to detect simulated tactile gratings, and their tactile sensitivity functions showed both linear and quadratic dependency on spatial frequency. In Experiment 2, using functional magnetic resonance imaging, we conducted a preliminary investigation to explore whether brain activation to physical vibrations correlated with blindfolded (but sighted) participants' performance with simulated tactile gratings outside the scanner. At the neural level, blindfolded (but sighted) participants' detection performance correlated with brain activation in bi-lateral supplementary motor cortex, left frontal cortex and right occipital cortex. Taken together with previous studies, these results suggest that there are similar perceptual and neural mechanisms for real and simulated touch sensations.

A scalable data transmission scheme for implantable optogenetic visual prostheses.

OBJECTIVE: This work described a video information processing scheme for optogenetic forms of visual cortical prosthetics. APPROACH: The architecture is designed to perform a processing sequence: Initially simplifying the scene, followed by a pragmatic visual encoding scheme which assumes that initially optical stimulation will be stimulating bulk neural tissue rather than driving individual phosphenes. We demonstrate an optical encoder, combined with what we called a zero-run length encoding (zRLE) video compression and decompression scheme-to wirelessly transfer information to an implantable unit in an efficient manner. In the final step, we have incorporated an even power distribution driver to prevent excessive power fluctuations in the optogenetic driving. SIGNIFICANCE: The key novelty in this work centres on the completeness of the scheme, the new zRLE compression algorithm and our even power distributor. MAIN RESULTS: Furthermore, although the paper focusses on the algorithm, we confirm that it can be implemented on real time portable processing hardware which we will use for our visual prosthetics.

Look up to the body: An eye-tracking investigation of 7-months-old infants' visual exploration of emotional body expressions.

The human body is an important source of information to infer a person's emotional state. Research with adult observers indicate that the posture of the torso, arms and hands provide important perceptual cues for recognising anger, fear and happy expressions. Much less is known about whether infants process body regions differently for different body expressions. To address this issue, we used eye tracking to investigate whether infants' visual exploration patterns differed when viewing body expressions. Forty-eight 7-months-old infants were randomly presented with static images of adult female bodies expressing anger, fear and happiness, as well as an emotionally-neutral posture. Facial cues to emotional state were removed by masking the faces. We measured the proportion of looking time, proportion and number of fixations, and duration of fixations on the head, upper body and lower body regions for the different expressions. We showed that infants explored the upper body more than the lower body. Importantly, infants at this age fixated differently on different body regions depending on the expression of the body posture. In particular, infants spent a larger proportion of their looking times and had longer fixation durations on the upper body for fear relative to the other expressions. These results extend and replicate the information about infant processing of emotional expressions displayed by human bodies, and they support the hypothesis that infants' visual exploration of human bodies is driven by the upper body.

Comparable search efficiency for human and animal targets in the context of natural scenes.

In a previous series of studies, we have shown that search for human targets in the context of natural scenes is more efficient than search for mechanical targets. Here we asked whether this search advantage extends to other categories of biological objects. We used videos of natural scenes to directly contrast search efficiency for animal and human targets among biological or nonbiological distractors. In visual search arrays consisting of two, four, six, or eight videos, observers searched for animal targets among machine distractors, and vice versa (Exp. 1). Another group searched for animal targets among human distractors, and vice versa (Exp. 2). We measured search slope as a proxy for search efficiency, and complemented the slope with eye movement measurements (fixation duration on the target, as well as the proportion of first fixations landing on the target). In both experiments, we observed no differences in search slopes or proportions of first fixations between any of the target-distractor category pairs. With respect to fixation durations, we found shorter on-target fixations only for animal targets as compared to machine targets (Exp. 1). In summary, we did not find that the search advantage for human targets over mechanical targets extends to other biological objects. We also found no search advantage for detecting humans as compared to other biological objects. Overall, our pattern of findings suggests that search efficiency in natural scenes, as elsewhere, depends crucially on the specific target-distractor categories.

Non-literal understanding and psychosis: Metaphor comprehension in individuals with a diagnosis of schizophrenia.

Previous studies suggest that understanding of non-literal expressions, and in particular metaphors, can be impaired in people with schizophrenia; although it is not clear why. We explored metaphor comprehension capacity using a novel picture selection paradigm; we compared task performance between people with schizophrenia and healthy comparator subjects and we further examined the relationships between the ability to interpret figurative expressions non-literally and performance on a number of other cognitive tasks. Eye-tracking was used to examine task strategy. We showed that even when IQ, years of education, and capacities for theory of mind and associative learning are factored in as covariates, patients are significantly more likely to interpret metaphorical expressions literally, despite eye-tracking findings suggesting that patients are following the same interpretation strategy as healthy controls. Inhibitory control deficits are likely to be one of multiple factors contributing to the poorer performance of our schizophrenia group on the metaphor trials of the picture selection task.

Interactions between Conscious and Subconscious Signals: Selective Attention under Feature-Based Competition Increases Neural Selectivity during Brain Adaptation.

Efficient perception in natural environments depends on neural interactions between voluntary processes within cognitive control, such as attention, and those that are automatic and subconscious, such as brain adaptation to predictable input (also called repetition suppression). Although both attention and adaptation have been studied separately and there is considerable knowledge of the neurobiology involved in each of these processes, how attention interacts with adaptation remains equivocal. We examined how attention interacts with visual and auditory adaptation by measuring neuroimaging effects consistent with changes in either neural gain or selectivity. Male and female human participants were scanned with functional magnetic resonance imaging (fMRI) first while they discriminated repetition of morphed faces or voices and either directed their attention to stimulus identity or spatial location. Attention to face or voice identity, while ignoring stimulus location, solely increased the gain of respectively face- or voice-sensitive cortex. The results were strikingly different in an experiment when participants attended to voice identity versus stimulus loudness. In this case, attention to voice while ignoring sound loudness increased neural selectivity. The combined results show that how attention affects adaptation depends on the level of feature-based competition, reconciling prior conflicting observations. The findings are theoretically important and are discussed in relation to neurobiological interactions between attention and different types of predictive signals.SIGNIFICANCE STATEMENT Adaptation to repeated environmental events is ubiquitous in the animal brain, an automatic typically subconscious, predictive signal. Cognitive influences, such as by attention, powerfully affect sensory processing and can overcome brain adaptation. However, how neural interactions occur between adaptation and attention remains controversial. We conducted fMRI experiments regulating the focus of attention during adaptation to repeated stimuli with perceptually balanced stimulus expectancy. We observed an interaction between attention and adaptation consistent with increased neural selectivity, but only under conditions of feature-based competition, challenging the notion that attention interacts with brain adaptation by only affecting response gain. This demonstrates that attention retains its full complement of mechanistic influences on sensory cortex even as it interacts with more automatic or subconscious predictive processes.

Modulated stimuli demonstrate asymmetric interactions between hearing and vision.

The nature of interactions between the senses is a topic of intense interest in neuroscience, but an unresolved question is how sensory information from hearing and vision are combined when the two senses interact. A problem for testing auditory-visual interactions is devising stimuli and tasks that are equivalent in both modalities. Here we report a novel paradigm in which we first equated the discriminability of the stimuli in each modality, then tested how a distractor in the other modality affected performance. Participants discriminated pairs of amplitude-modulated tones or size-modulated visual objects in the form of a cuboid shape, alone or when a similarly modulated distractor stimulus of the other modality occurred with one of the pair. Discrimination of sound modulation depth was affected by a modulated cuboid only when their modulation rates were the same. In contrast, discrimination of cuboid modulation depth was little affected by an equivalently modulated sound. Our results suggest that what observers perceive when auditory and visual signals interact is not simply determined by the discriminability of the individual sensory inputs, but also by factors that increase the perceptual binding of these inputs, such as temporal synchrony.

The cortical face network of the prosopagnosic patient PS with fast periodic stimulation in fMRI.

Following brain damage, the patient PS suffers from selective impairment in recognizing individuals by their faces, i.e., prosopagnosia. Her case has been documented in more than 30 publications to date, informing about the nature of individual face recognition and its neural basis. Here we report new functional neuroimaging data obtained on PS with a recently developed fast periodic stimulation functional imaging (FPS-fMRI) paradigm combining high sensitivity, specificity and reliability in identifying the cortical face-selective network (Gao et al., 2018). We define the extent of the large and reliable face-selective activation in the lateral section of the right middle fusiform gyrus, i.e., right FFA, which forms a single cluster of activation lying at the anterior border of the patient's main lesion in the inferior occipital gyrus. The contribution of posterior face-selective responses in the right or left inferior occipital gyrus is ruled out, strongly supporting the view that face-selective activity emerges in the right middle fusiform gyrus of the patient's brain from non-face-selective inputs from early visual areas. Despite this, low-level visual cues, i.e., amplitude spectrum of images, do not contribute to neural face-selective responses anywhere in the patient's cortical face network. This sensitive face-localizer approach also reveals an intact face-selective network anterior to the fusiform gyrus, including clusters in the ventral anterior temporal lobe (occipito-temporal sulcus and temporal pole) and the inferior frontal gyrus, with a right hemispheric dominance. Overall, with the exception of the left inferior occipital gyrus, the cortical face network of the prosopagnosic patient PS appears remarkably similar to typical individuals in non-brain damaged regions. However, unlike in neurotypical adults tested in the present study, including age-matched controls, a novel paradigm based on FPS-FMRI confirms that the patient's face network is insensitive to differences between rapidly presented pictures of unfamiliar individual faces, in line with her prosopagnosia.

An incremental dual-task paradigm to investigate pain attenuation by task difficulty, affective content and threat value.

There is accumulating evidence that task demands and psychological states can affect perceived pain intensity. Different accounts have been proposed to explain this attenuation based either on how limited attentional resources are allocated to the pain stimulus or on how the threat value of the pain stimulus biases attention. However, the evidence for both proposals remains mixed. Here we introduce an incremental dual-task paradigm in which participants were asked to detect pain on their fingertip without any additional tasks during baseline phases or while concurrently detecting visual targets during task phases. The force applied to participants' fingertip in all phases increased incrementally until they detected moderate pain. In Experiment 1, we used coloured shapes and in Experiment 2 we used affective images as visual targets. We also manipulated the threat value of the pain stimulus in Experiment 2. For both experiments, we found that a concurrent task attenuated perceived pain intensity: mean force was significantly greater for the same moderate pain during task compared to baseline phases. Furthermore although task difficulty and affective content did not affect pain perception, the threat value of the pain stimulus moderated the magnitude of pain attenuation.