Patrick Haggard’s research while affiliated with University College London and other places

The spinal cord is the key bridge between the brain and the body. However, scientific understanding of healthy spinal cord function has historically been limited because noninvasive measures of its neural activity have proven exceptionally challenging. In this work, we describe a novel recording and analysis approach to obtain non-invasive, high-resolution images of the electrical activity of the spinal cord in humans (Electrical Spinal Imaging, ESI). ESI is analytically simple, easy to implement, and data-driven: it does not involve template-based strategies prone to produce spurious signals. Using this approach we provide a detailed description and physiological characterization of the spatiotemporal dynamics of the peripheral, spinal and cortical activity elicited by somatosensory stimulation. We also demonstrate that attention modulates post-synaptic activity at spinal cord level. Our method has enabled four new insights regarding spinal cord activity. (1) We identified three distinct responses in the time domain: sP9, sN13 and sP22. (2) The sP9 is a traveling wave reflecting the afferent volley entering the spinal cord through the dorsal root. (3) In contrast, the sN13 and sP22 reflect segmental post-synaptic activity. (4) While the sP9 response is first seen on the dorsal electrodes ipsilateral to the stimulated side, the sN13 and sP22 were not lateralised with respect to the side of stimulation. (5) Unimodal attention strongly modulates the amplitude of the sP22, but not that of the sP9 and sN13 components. The proposed method offers critical insights into the spatiotemporal dynamics of somatosensory processing within the spinal cord, paving the way for precise non-invasive functional monitoring of the spinal cord in basic and clinical neurophysiology.

The capacity for voluntary action is a distinctive feature of human minds. However, experimental studies of volition struggled to capture defining features of human voluntariness. Here we developed a competitive game which incentivised participants to innovate their action choices to find the right time to avoid a collision with an opponent who predicted the timing of the participant’s action choice. One group of participants received explicit information about the competitor’s action-selection rules, while a second group had no information about the competitor. Both groups showed increased behavioural stochasticity when adapting to a competitor who punished participant’s choice biases. However, the group who had no explicit information generated their action choices in a way that avoided the action that the competitor was likely to take. In contrast, the group who explicitly knew the competitor’s action-selection rules avoided the same action they took in preceding trials so that the competitor could not easily exploit the participant’s behavioural patterns. These findings suggest that people can develop beliefs about other agents in the social environment within which they work, and can adapt voluntary action choices accordingly. However, explicit explanations about the other agent facilitate model-based planning in the voluntary generation of novel action patterns.

Skin stimuli reach the brain via multiple neural channels specific for different stimulus types. These channels interact in the spinal cord, typically through inhibition. Inter-channel interactions can be investigated by selectively stimulating one channel and comparing the sensations that result when another sensory channel is or is not concurrently stimulated. Applying this logic to thermal–mechanical interactions proves difficult, because most existing thermal stimulators involve skin contact. We used a novel non-tactile stimulator for focal cooling (9 mm²) by using thermal imaging of skin temperature as a feedback signal to regulate exposure to a dry-ice source. We could then investigate how touch modulates cold sensation by delivering cooling to the human hand dorsum in either the presence or absence of light touch. Across three signal detection experiments, we found that sensitivity to cooling was significantly reduced by touch. This reduction was specific to touch, as it did not occur when presenting auditory signals instead of the tactile input, making explanations based on distraction or attention unlikely. Our findings suggest that touch inhibits cold perception, recalling interactions of touch and pain previously described by Pain Gate Theory.

In everyday life, decision-makers need to integrate information from various sources which differ in how reliable the correct information is provided. The present study addressed whether people can optimally use explicit information about the trustworthiness of the information source and whether people know how information sources affect their decisions. In each trial, we presented a sequence of six information sources which indicated a correct colour (red or blue) each with a different level of reliability. Each source was explicitly labelled the reliability percentage, i.e., the likelihood that a source provides correct information. Participants were asked to decide which colour was more likely to be correct. In the first series of three experiments, we found that participants failed to make use of explicit reliability cues optimally. In particular, participants were less able to use reliably wrong information sources (reliability below 50%) than reliably correct information sources (reliability above 50%), even though these two types of information sources were equally informative. In addition, participants failed to ignore the colour displayed by unreliable sources (50% reliability), although these sources gave just random information for a binary decision. In the second series of two experiments, we asked participants, after each choice, to report their subjective feelings of whether they followed or opposed a colour suggested by sources with a specific reliability percentage. We found that the ratings of the participant's influence report tracked the amount of evidence which supported the choice they just made. Further, participants were able to introspect their own choice bias guided by unreliable information sources. These findings suggest that human choice behaviour deviates from Bayesian integration. However, people have a good metacognitive monitoring of how their decisions are driven by external stimuli.

Religion is a widespread feature of human life. Religions typically include both distinctive varieties of experience, and also a set of foundational beliefs. An additional, but often overlooked, part of many religions is their expression through specific actions, which we here designate religious motor behaviours. Here we describe these religious motor behaviours, and offer a taxonomy based on the conceptual schemes of movement neuroscience and neurology. Thus, religious rituals include both behaviours characterised by decreased motor output (e.g., ritualistic silence), and behaviours characterised by increased motor output (e.g., ritual dances). Neurology often also distinguishes between movements that are experienced as voluntary or involuntary. We show that this same distinction can also apply to religious experiences, since these may be characterised either by a heightened sense of personal control, or a sense of being controlled by an external, divine source. We then use these conceptual structures of movement neuroscience to investigate examples from a wide range of religious contexts. We thereby categorise religious motor behaviours into different classes, focussing on specific examples: repetitive ritual actions; motor behaviours where the experience of volition is altered, such as automatisms; and possession-like states. We suggest that a scientific approach to these behaviours should include their predominant phenomenological presentation, the accompanying subjective experience of volition, and the underlying neurocognitive mechanisms. This investigation shows rich parallels between religious motor behaviours and motor behaviours observed in neurological disorders, including those that present with functional neurological symptoms. Our approach does not and should not pathologise religious motor behaviours, but rather draws attention to a rich set of non-clinical motor phenomena that highlight important social, cultural and psychological elements of human movement control. Movement neuroscience and religious activity have unexplored overlaps and can usefully learn from each other.

Gesture control systems based on mid-air haptics are increasingly used in infotainment systems in cars, where they can provide rich haptic feedback to improve human-computer interactions. Laboratory studies show that mid-air haptic feedback reduces drivers’ distractions and improve safety. However, it is unclear how the perception of mid-air ultrasound stimuli is affected by prolonged exposure to vibrational noise, e.g., from the steering wheel of a moving vehicle. Studies on vibrotactile adaptation show that perception of mechanical vibration is impaired by prior exposure to stimuli of the same frequency. Here, we investigated the effect of mechanical adaptation on the perception of mid-air ultrasound stimuli. We measured participants’ detection threshold for ultrasound stimuli of different frequencies both before and after exposure to 30 s mechanical vibrations. Across two experiments, we systematically manipulated the frequency and amplitude of the adapting stimulus. We found that exposure to low-frequency mechanical vibrations significantly impaired the detection of low-frequency ultrasound stimuli. In contrast, exposure to high-frequency mechanical vibrations equally impaired perception of both low- and high-frequency ultrasound stimuli. This effect was mediated by the amplitude of the adapting stimulus, with stronger mechanical vibrations producing a larger increase in participants’ detection threshold. Overall, these findings show that perception of mid-air ultrasound stimuli is affected by specific sources of mechanical noise. Crucially, frequency-specificity in the low-frequency band also points toward possible mitigating solutions that could help minimising unwanted desensitization of mechanoreceptor channels during mid-air haptic interactions.

Generating a voluntary action typically involves some experience of conscious intention. Prospective theories propose that conscious intention is a readout of action preparation processes, while retrospective theories view conscious intention as an inference retro-inserted into narratives of one’s own behaviour. Studying conscious intention experimentally is difficult, because (a) eliciting voluntary actions in laboratory settings is problematic, and (b) existing measures of conscious intention using post-action reports could involve post hoc biases. We developed touch-typing versions of a verbal fluency task to elicit voluntary actions to address (a), and then interrupted participants quasi-randomly, asking “Were you about to type your next word?”, to address (b). Across two experiments with 51 participants, we found conscious intention emerged at 1079 ms (SD=1366 ms) and 1258 ms (SD=749 ms) before the estimated time of upcoming action. EEG results showed more reduction of beta-band oscillations and a greater readiness-potential-like deflection prior to probes that elicited reports of conscious intention, compared to probes that did not. Our results offer novel support for prospective theories of conscious intention, and may partly address methodological difficulties of previous studies.

Self vs. external attribution of motions based on vestibular cues is suggested to underlie our coherent perception of object motion and self-motion. However, it remains unclear whether such attribution also underlies sensorimotor responses. Here, we examined this issue in the context of touch. We asked participants to lightly touch a moving object with their thumb while standing still on an unstable surface. We measured both the accuracy of judging the object motion direction and the postural response. If the attribution underlies both object-motion perception and posture control, sensitivity of posture to object motion should decrease with motion speed since high speed motion is unlikely to reflect self-motion. Furthermore, when motion perception is erroneous, there should be a corresponding increase in postural responses. Our results are consistent with these predictions and suggest that self-external attribution of somatosensory motion underlies both object motion perception and postural responses.

When we run our hand across a surface, each finger typically repeats the sensory stimulation that the leading finger has already experienced. Because of this redundancy, the leading finger may attract more attention and contribute more strongly when tactile signals are integrated across fingers to form an overall percept. To test this hypothesis, we re-analysed data collected in a previous study (Arsanova et al., 1), where two probes were moved in different directions on two different fingerpads and participants reported the probes' average direction. Here, we evaluate the relative contribution of each finger to the percept and examine whether multi-digit integration gives priority to the leading finger. Although the hand actually remained static in these experiments, a 'functional leading finger' could be defined with reference to the average direction of the stimuli, and the direction of hand-object relative motion that this implied. When participants averaged the motion direction across fingers of the same hand, the leading finger received a higher weighting than the non-leading finger, even though this biased estimates of average direction. Importantly, this bias disappeared when averaging motion direction across the two hands. Both the reported average direction and its systematic relation to the difference between the individual stimulus directions were explained by a model of motion integration in which the sensory weighting of stimuli depends on the directions of the applied stimuli. Our finding supports the hypothesis that the leading finger, which often receives novel information in natural hand-object interactions, is prioritized in forming our tactile perception.