Attention modulates sensory suppression during back movements

Modulation of attention to pain by goal-directed action: a somatosensory evoked potentials approach

Background

Attentional processes are modulated by current goal pursuit. While pursuing salient cognitive goals, individuals prioritize goal-related information and suppress goal-irrelevant ones. This occurs in the context of pain too, where nonpain cognitive goal pursuit was found to have inhibitory effects on pain-related attention. Crucially, how pursuing nonpain motor goals affects pain-related somatosensory attention is still unknown. The aim of this study was to investigate whether nonpain motor goal pursuit would attenuate pain-related somatosensory attention.

Methods

Healthy volunteers (N = 45) performed a robotic arm conditioning task where movements were paired with conflicting (pain and reward), threatening (only pain) or neutral (no pain and no reward) outcomes. To increase the motivational value of pursuing the nonpain motor goal, in the conflicting condition participants could receive a reward for a good motor performance. To examine somatosensory attention during movement, somatosensory evoked potentials (SEPs; N120 and P200) were obtained in response to innocuous tactile stimuli administered on a pain-relevant or pain-irrelevant body location. We expected that the threat of pain would enhance somatosensory attention. Furthermore, we expected that the possibility of getting a reward would inhibit this effect, due to pain-reward interactions.

Results

Against our predictions, the amplitude of the N120 did not differ across movement types and locations. Furthermore, the P200 component showed significantly larger SEPs for conflicting and threat movements compared to neutral, suggesting that the threat of pain increased somatosensory attention. However, this effect was not modulated by nonpain motor goal pursuit, as reflected by the lack of modulation of the N120 and P200 in the conflicting condition as compared to the threat condition. This study corroborates the idea that pain-related somatosensory attention is enhanced by threat of pain, even when participants were motivated to move to obtain a reward.

Dissociable effects of attention and expectation on perceptual sensitivity to action-outcomes

Self-generated sensations evoke attenuated neural response - physiological attenuation - and is perceived with less intensity - perceptual attenuation. This phenomenon is referred as sensory attenuation and is proposed to reflect the silencing of predicted sensations. The present study aimed to investigate the independent contribution of expectation and attention on sensory attenuation. The expectation associated with the stimulus feature and the focus of attention was manipulated independently by orthogonal cues. We found pronounced sensory attenuation at the unattended location when the stimulus was self-generated (Experiment 1). When the stimulus was externally-generated (Experiment 2), sensory attenuation was observed at the attended location. Sensory attenuation of expected action-outcome was not observed when the attention cue was uninformative (Experiment 3A). The findings corroborate the claim from Bayesian models that attention mediates sensory attenuation. The results also highlight the paradoxes in Bayesian proposals of perception-action interaction.

Motor action changes pain perception: a sensory attenuation paradigm in the context of pain

ABSTRACT

A large body of evidence indicates how pain affects motor control, yet the way the motor system influences pain perception remains unclear. We present 2 experiments that investigated sensory attenuation of pain implementing a 2-alternative forced choice paradigm. Particularly, healthy participants received painful stimuli on a moving and nonmoving hand during the execution or the preparation of reaching motor actions. At the end of each trial, they indicated on which hand they perceived the stimulus stronger. The point of subjective equality was obtained to measure sensory attenuation. The intensity (experiment 1) and the threat value (experiment 2) of the pain stimuli were manipulated between-subjects to examine their impact on sensory attenuation. Results of experiment 1 (N = 68) revealed that executing a motor action attenuates pain processing in the moving hand. Sensory attenuation during motor preparation alone occurred with stronger stimulus intensities. Sensory attenuation was not affected by the intensity of the pain stimuli. Results of experiment 2 (N = 79) replicated the phenomenon of sensory attenuation of pain during motor action execution. However, sensory attenuation was not affected by the threat value of pain. Together these findings indicate that executing, but not preparing, a motor action affects pain processing in that body part. No significant associations were found between sensory attenuation indices and inhibitory control abilities or pain catastrophizing, vigilance and rumination. These results provide insight into the inhibitory effects of motor actions on pain processing, suggesting that pain perception is a dynamic experience susceptible to individuals' actions in the environment.

Action-related auditory ERP attenuation is not modulated by action effect relevance

Event-related potentials (ERPs) elicited by self-induced sounds are often smaller than ERPs elicited by identical, but externally generated sounds. This action-related auditory ERP attenuation is more pronounced when self-induced sounds are intermixed with similar sounds generated by an external source. The current study explored whether attentional factors contributed to this phenomenon. Participants performed tone-eliciting actions, while the action-tone contingency and the set of additional action effects (tactile only, tactile and visual) were manipulated in a blocked manner. Previous action-tone contingence-effects were replicated, but the addition of other sensory action consequences did not influence the magnitude of auditory ERP attenuation. This suggests that the amount of attention allocated to concurrent non-auditory action effects does not substantially affect the magnitude of action-related auditory ERP attenuation and is on a par with the assumption that action-related auditory ERP attenuation might be related to the process of distinguishing self-induced stimuli from externally generated ones.

Now You Feel It, Now You Don't: The Effect of Movement, Cue Complexity, and Body Location on Tactile Change Detection

OBJECTIVE

To evaluate the effects that movement, cue complexity, and the location of tactile displays on the body have on tactile change detection.

BACKGROUND

Tactile displays have been demonstrated as a means to address data overload by offloading the visual and auditory modalities. However, change blindness-the failure to detect changes in a stimulus when changes coincide with another event or disruption in stimulus continuity-has been demonstrated to affect the tactile modality and may be exacerbated during movement. The complexity of tactile cues and locations of tactile displays on the body may also affect the detection of changes in tactile patterns. Limitations to tactile perception need to be examined.

METHOD

Twenty-four participants performed a tactile change detection task while sitting, standing, and walking. Tactile cues varied in complexity and included low, medium, and high complexity cues presented to the arm or back.

RESULTS

Movement adversely affects tactile change detection as hit rates were the highest while sitting, followed by standing and walking. Cue complexity affected tactile change detection: Low complexity cues resulted in higher detection rates compared with medium and high complexity cues. The arms exhibited better change detection performance than the back.

CONCLUSION

The design of tactile displays should consider the effect of movement. Cue complexity should be minimized and decisions about the location of a tactile display should take into account body movements to support tactile perception.

APPLICATION

The findings can provide design guidelines to inform tactile display design for data-rich, complex domains.

Hypervigilance for Bodily Sensations in the Back During a Movement Task in People With Chronic and Recurrent Low Back Pain

OBJECTIVES

The current study assessed the role of hypervigilance for bodily sensations in the back in long-term low back pain problems.

METHODS

People with chronic low back pain, recurrent low back pain, and no low back pain were compared on the extent to which they attended to somatosensory stimuli on the back during a movement task. To measure hypervigilance, somatosensory event-related potentials (SEPs) to task-irrelevant tactile stimuli on the back were measured when preparing movements in either a threatening or a neutral condition, indicated by a cue signaling possible pain on the back during movement or not.

RESULTS

Results showed stronger attending to stimuli on the back in the threat condition than in the neutral condition, as reflected by increased amplitude of the N96 SEP. However, this effect did not differ between groups. Similarly, for all 3 groups the amplitude of the P172 was larger for the threatening condition, suggesting a more general state of arousal resulting in increased somatosensory responsiveness. No significant associations were found between somatosensory attending to the back and theorized antecedents such as pain catastrophizing, pain-related fear, and pain vigilance.

DISCUSSION

The current study confirmed that individuals preparing a movement attended more toward somatosensory stimuli at the lower back when anticipating back pain during the movement, as measured by the N96 SEP. However, no differences were found between participants with chronic low back pain or recurrent low back pain, or the pain-free controls.

Age effects on sensorimotor predictions: What drives increased tactile suppression during reaching?

Tactile suppression refers to the phenomenon that tactile signals are attenuated during movement planning and execution when presented on a moving limb compared to rest. It is usually explained in the context of the forward model of movement control that predicts the sensory consequences of an action. Recent research suggests that aging increases reliance on sensorimotor predictions resulting in stronger somatosensory suppression. However, the mechanisms contributing to this age effect remain to be clarified. We measured age-related differences in tactile suppression during reaching and investigated the modulation by cognitive processes. A total of 23 younger (18-27 years) and 26 older (59-78 years) adults participated in our study. We found robust suppression of tactile signals when executing reaching movements. Age group differences corroborated stronger suppression in old age. Cognitive task demands during reaching, although overall boosting suppression effects, did not modulate the age effect. Across age groups, stronger suppression was associated with lower individual executive capacities. There was no evidence that baseline sensitivity had a prominent impact on the magnitude of suppression. We conclude that aging alters the weighting of sensory signals and sensorimotor predictions during movement control. Our findings suggest that individual differences in tactile suppression are critically driven by executive functions.

Speed of reaction to sensory stimulation is enhanced during movement

We report four experiments on the speed of people's reactions to sensory stimulation while throwing and catching a basketball. Thirty participants participated in Experiment 1, split according to basketball expertise: none, intermediate (6years on average), or advanced (20years or more). The participants had to catch a bouncing basketball. The movement triggered a short tactile pulse in a tactor attached to their wrist to which they made a speeded vocal response (RT). The pulse could be presented either at rest, at two time-points during the reaching movement, or when the hand reached forward to catch the ball. The results indicated that participants responded more rapidly to vibrations on the moving hand relative to preparing or catching the ball, with expert athletes responding significantly faster than novices. In a second experiment, participants made a speeded vocal response to an auditory signal. As in Experiment 1, faster auditory RTs were observed when the hand was moving, as compared to the other time-points. In a third study, the participants responded to a pulse delivered at their resting hand at various time-points corresponding to the average timings of stimulation in Experiment 1. The results revealed comparable RTs across the tested time-points. In a final experiment, the participants made a vocal response to a pulse presented at various time-points while they were throwing the basketball. The results indicated faster tactile RTs while the ball was being thrown. These results are discussed with reference to the literature on goal-directed movements and in terms of current theories of attention and sensory suppression.

Attention Wins over Sensory Attenuation in a Sound Detection Task

‘Sensory attenuation’, i.e., reduced neural responses to self-induced compared to externally generated stimuli, is a well-established phenomenon. However, very few studies directly compared sensory attenuation with attention effect, which leads to increased neural responses. In this study, we brought sensory attenuation and attention together in a behavioural auditory detection task, where both effects were quantitatively measured and compared. The classic auditory attention effect of facilitating detection performance was replicated. When attention and sensory attenuation were both present, attentional facilitation decreased but remained significant. The results are discussed in the light of current theories of sensory attenuation.

Active inference, sensory attenuation and illusions

Active inference provides a simple and neurobiologically plausible account of how action and perception are coupled in producing (Bayes) optimal behaviour. This can be seen most easily as minimising prediction error: we can either change our predictions to explain sensory input through perception. Alternatively, we can actively change sensory input to fulfil our predictions. In active inference, this action is mediated by classical reflex arcs that minimise proprioceptive prediction error created by descending proprioceptive predictions. However, this creates a conflict between action and perception; in that, self-generated movements require predictions to override the sensory evidence that one is not actually moving. However, ignoring sensory evidence means that externally generated sensations will not be perceived. Conversely, attending to (proprioceptive and somatosensory) sensations enables the detection of externally generated events but precludes generation of actions. This conflict can be resolved by attenuating the precision of sensory evidence during movement or, equivalently, attending away from the consequences of self-made acts. We propose that this Bayes optimal withdrawal of precise sensory evidence during movement is the cause of psychophysical sensory attenuation. Furthermore, it explains the force-matching illusion and reproduces empirical results almost exactly. Finally, if attenuation is removed, the force-matching illusion disappears and false (delusional) inferences about agency emerge. This is important, given the negative correlation between sensory attenuation and delusional beliefs in normal subjects--and the reduction in the magnitude of the illusion in schizophrenia. Active inference therefore links the neuromodulatory optimisation of precision to sensory attenuation and illusory phenomena during the attribution of agency in normal subjects. It also provides a functional account of deficits in syndromes characterised by false inference and impaired movement--like schizophrenia and Parkinsonism--syndromes that implicate abnormal modulatory neurotransmission.