Fig 1 - uploaded by Dana Maslovat
Content may be subject to copyright.
Rectified EMG traces of a typical participant in: A) the control (non-startle) condition, B) the ST-0 condition, where the SAS was presented with the go-signal, C) the ST-400 condition, where the SAS was presented 400 ms prior to the go-signal. Black traces represent voluntary responses to the go-signal, and grey traces represent StartReact responses to the SAS. ECR = extensor carpii radialis; SCM = sternocleidomastoid.
Source publication
Response preparation in simple reaction time (RT) tasks has been modeled as an increase in neural activation to a sub-threshold level, which is maintained until the go-signal. However, the amount of time required for response preparation following a warning signal (WS) is currently unclear, as experiments typically employ long foreperiods to ensure...
Contexts in source publication
Context 1
... tests indicated that startle RTs in both the long (98.8 ms, SD = 23.8) and short (99.0 ms, SD = 16.9) ITI tasks were significantly shorter than control RTs (see Figure 1 A & B for representative individual data from the long ITI task for a control and startle trial, respectively), with no significant difference between the tasks for SAS trials. However, in the control conditions premotor RT was significantly shorter in the long ITI task (201.8 ms, SD = 23.8) ...
Context 2
... order to evaluate the premotor RT data, it was necessary to determine if the participant was involuntarily responding at short latency in response to the SAS, or voluntarily responding later to the visual go-signal (as instructed). For example, Figure 1C displays representative individual data showing a StartReact response in the ST-400 condition (grey line; note the presence of SCM and ECR activity shortly following the SAS), as well as a trial from the ST-400 condition where there was an early SCM burst in response to the SAS but a later voluntary response was made to the IS (black line). ...
Context 3
... tests indicated that startle RTs in both the long (98.8 ms, SD = 23.8) and short (99.0 ms, SD = 16.9) ITI tasks were significantly shorter than control RTs (see Figure 1 A & B for representative individual data from the long ITI task for a control and startle trial, respectively), with no significant difference between the tasks for SAS trials. However, in the control conditions premotor RT was significantly shorter in the long ITI task (201.8 ms, SD = 23.8) ...
Context 4
... order to evaluate the premotor RT data, it was necessary to determine if the participant was involuntarily responding at short latency in response to the SAS, or voluntarily responding later to the visual go-signal (as instructed). For example, Figure 1C displays representative individual data showing a StartReact response in the ST-400 condition (grey line; note the presence of SCM and ECR activity shortly following the SAS), as well as a trial from the ST-400 condition where there was an early SCM burst in response to the SAS but a later voluntary response was made to the IS (black line). ...
Similar publications
A substantial body of research in the past few decades has converged on the idea that the so-called "sense of agency", the feeling of being in control of our own actions, arises from the integration of multiple sources of information at different levels. In this study, we investigated whether a measurable sense of agency can be detected for mental...
Citations
... Our estimates of the time required to prepare an accurate motor plan were substantially faster than prior estimates using SAS (Carlsen and Mackinnon 2010;MacKinnon et al. 2013;Smith et al. 2019) or proprioceptive inputs (Heckman and Perreault 2019). Smith and colleagues used a traditional reaction time task with a fixed time of 500 ms between presentation of the motor target and the cue to move; a SAS was presented at 100-ms intervals beginning with target presentation. ...
... Smith and colleagues used a traditional reaction time task with a fixed time of 500 ms between presentation of the motor target and the cue to move; a SAS was presented at 100-ms intervals beginning with target presentation. They found that accurate movements could occasionally be triggered 100 ms after target presentation and preparation of an accurate movement continued until 300-400 ms after target presentation (Smith et al. 2019). Another study found that the time required to prepare a motor plan was influenced by the temporal predictability of the cue to move occurring in 500 ms for a highly predictable cue and over a longer period for a less predictable cue (Carlsen and Mackinnon 2010). ...
... This approach decouples preparation of a motor action from the initiation of movement, allowing them to occur independently and overlap in time (Lara et al. 2018). In addition, the short time between target presentation and the cue to move created an urgency not present in other SAS paradigms examining the time course of motor planning (Carlsen and Mackinnon 2010;Alibiglou and MacKinnon 2012;Maslovat et al. 2017;Smith et al. 2019). ...
Movement goals are an essential component of motor planning, altering voluntary and involuntary motor actions. While there have been many studies of motor planning, it is unclear if motor goals influence voluntary and involuntary movements at similar latencies. The objectives of this study were to determine how long it takes to prepare a motor action and to compare this time for voluntary and involuntary movements. We hypothesized a prepared motor action would influence voluntarily and involuntarily initiated movements at the same latency. We trained subjects to reach with a forced reaction time paradigm and used a startling acoustic stimulus (SAS) to trigger involuntary initiation of the same reaches. The time available to prepare was controlled by varying when one of four reach targets was presented. Reach direction was used to evaluate accuracy. We quantified the time between target presentation and the cue or trigger for movement initiation. We found that reaches were accurately initiated when the target was presented 48 ms before the SAS and 162 ms before the cue to voluntarily initiate movement. While the SAS precisely controlled the latency of movement onset, voluntary reach onset was more variable. We, therefore, quantified the time between target presentation and movement onset and found no significant difference in the time required to plan reaches initiated voluntarily or involuntarily (∆ = 8 ms, p = 0.2). These results demonstrate that the time required to plan accurate reaches is similar regardless of if they are initiated voluntarily or triggered involuntarily. This finding may inform the understanding of neural pathways governing storage and access of motor plans.
... Furthermore, when the response has been prepared and held in advance, the response latency relative to the go-signal is largely indicative of initiation processes 1 , which have been shown to be accelerated when the go-signal is replaced with a loud acoustic stimulus capable of eliciting a reflexive startle response 6,7 . In these experiments the startling acoustic stimulus (SAS) results in a much shorter RT latency, yet the execution of the response is largely unaffected 3,8 ; critically however, this so-called "StartReact" effect only occurs when the response is in a high state of preparation 9,10 . ...
... For example, when presenting a very loud SAS (> 120 dB) in place of or at the same time as the nonstartling go-signal, it is very likely that the high intensity SAS will provide the necessary input to involuntarily trigger the response, as the participant would be expected to be at a high level of preparation when the auditory stimulus is presented. However, response triggering may or may not occur when the stimulus intensity is lower, when the SAS is presented substantially earlier than the usual time of the go-signal (i.e., when preparation level is not maximized) 10,26,30 , or during dual-task performance 31,32 . ...
In a simple reaction time task, the presentation of a startling acoustic stimulus has been shown to trigger the prepared response at short latency, known as the StartReact effect. However, it is unclear under what conditions it can be assumed that the loud stimulus results in response triggering. The purpose of the present study was to examine how auditory stimulus intensity and preparation level affect the probability of involuntary response triggering and the incidence of activation in the startle reflex indicator of sternocleidomastoid (SCM). In two reaction time experiments, participants were presented with an irrelevant auditory stimulus of varying intensities at various time points prior to the visual go-signal. Responses were independently categorized as responding to either the auditory or visual stimulus and those with or without SCM activation (i.e., SCM+/−). Both the incidence of response triggering and proportion of SCM+ trials increased with stimulus intensity and presentation closer to the go-signal. Data also showed that participants reacted to the auditory stimulus at a much higher rate on trials where the auditory stimulus elicited SCM activity versus those that did not, and a logistic regression analysis confirmed that SCM activation is a reliable predictor of response triggering for all conditions.
... Unfortunately, it is difficult to estimate by how much the onset is advanced. For example, if the EMG onset is advanced by 80 ms (Smith et al. 2019), we might have expected to see an increase in the number of trials at 200 ms interval. However, TMS pulses at 200 ms might also advance movement onset, in which case the additional counts from speeded trials at −280 ms would not be observed. ...
In reaction time (RT) tasks corticospinal excitability (CSE) rises just prior to movement. This is preceded by a paradoxical reduction in CSE, when the time of the imperative ("GO") stimulus is relatively predictable. Because RT tasks emphasise speed of response, it is impossible to distinguish whether reduced CSE reflects a mechanism for withholding prepared actions, or whether it is an inherent part of movement preparation. To address this question, we used transcranial magnetic stimulation (TMS) to estimate CSE changes preceding 1) RT movements; 2) movements synchronized with a predictable signal (predictive timing or PT movements); and 3) self-paced movements. Results show that CSE decreases with a similar temporal profile in all three cases, suggesting that it reflects a previously unrecognised state in the transition between rest and movement. Although TMS revealed reduced CSE in all movements, the TMS pulse itself had different effects on movement times. TMS given ~200 ms before the times to move speeded the onset of RT and self-paced movements, suggesting that their initiation depends on a form of trigger that can be conditioned by external events. On the contrary, PT movements did not show this effect, suggesting the use of a different triggering strategy prioritizing internal events.
... This may hint at a potential effect of raised attention and expectation of discomfort during active TMS. Decreased response times and possibly even enhanced facilitation may occur, e.g., due to the more startling effect from active as compared to sham TMS (Smith et al. 2019), although sham coils are specifically designed to simulate the extracortical effects of TMS. The increment in response time differences between active and sham TMS at anterior stimulation targets might thus indicate that such an unspecific effect at all stimulation sites was abolished by TMS-induced inhibition within area 44, but not within area 45. ...
Functional imaging data suggest different regions for semantic, syntactic, and phonological processing in an anterior-to-posterior direction along the inferior frontal gyrus. Language mapping by use of neuro-navigated transcranial magnetic stimulation (TMS) is frequently applied in clinical research to identify language-related cortical regions. Recently, we proposed a high spatial resolution approach for more detailed language mapping of cortical sub-areas such as Broca’s region. Here, we employed a phonological picture–word interference paradigm in healthy subjects to reveal functional specialization in Broca’s region for phonological processing. The behavioral phonological priming effect is characterized by accelerated naming responses to target pictures accompanied by phonologically related auditory distractor words. We hypothesized that the inhibitory effects of TMS on language processing would reduce phonological priming only at stimulation sites involved in phonological processing. In active as compared to sham TMS, we found reduced phonological facilitation specifically at sites overlapping with the probabilistic cytoarchitectonic area 44. Our findings complemented functional imaging data by revealing structure–function relationship in Broca’s region. The introduction of a reaction time based interference paradigm into TMS language mapping increases the objectivity of the method and allows to explore functional specificity with high temporal resolution. Findings may help to interpret results in clinical applications.
Introduction:
It is currently unknown how the central nervous system controls ballistic whole-body movements like vertical jumps. Here we set out to study the time frame of generating muscle activation patterns for maximum-effort jumps from different initial postures.
Methods:
We had ten healthy male participants make a slow countermovement from an upright position and initiate a maximal vertical jump as soon as possible following an auditory trigger. The trigger was produced when hip height dropped below one of three preselected values, unknown in advance to the participant, so that the participant was uncertain about the posture from which to initiate the jump. Furthermore, we determined the ensuing bottom postures reached during jumps, and from these postures had the participants perform maximum-effort squat jumps in two conditions: whenever they felt ready, or as soon as possible following an auditory trigger. Kinematics and ground reaction forces were measured, and electromyograms were collected from gluteus maximus, biceps femoris, rectus femoris, vastus lateralis, gastrocnemius and soleus. For each muscle, we detected activation onsets, as well as reaction times defined as the delay between trigger onset and activation onset.
Results:
In the jumps preceded by a slow countermovement, the posture from which to initiate the jump was unknown before trigger onset. Nevertheless, in these jumps, posture-specific muscle activation patterns were already released within 200 ms after trigger onset and reaction times were not longer and jump heights not less than in squat jumps from corresponding bottom postures.
Discussion:
Our findings suggest that the generation of muscle activation patterns for jumping does not start before trigger onset and requires only about 200 ms.
Cognitive fatigue (CF) can result from sustained mental effort, is characterized by subjective feelings of exhaustion and cognitive performance deficits, and is associated with slowed simple reaction time (RT). This study determined whether declines in motor preparation underlie this RT effect. Motor preparation level was indexed using simple RT and the StartReact effect, wherein a prepared movement is involuntarily triggered at short latency by a startling acoustic stimulus (SAS). It was predicted that if decreased motor preparation underlies CF-associated RT increases, then an attenuated StartReact effect would be observed following cognitive task completion. Subjective fatigue assessment and a simple RT task were performed before and after a cognitively fatiguing task or non-fatiguing control intervention. On 25% of RT trials, a SAS replaced the go-signal to assess the StartReact effect. CF inducement was verified by significant declines in cognitive performance (p = 0.003), along with increases in subjective CF (p < 0.001) and control RT (p = 0.018) following the cognitive fatigue intervention, but not the control intervention. No significant pre-to-post-test changes in SAS RT were observed, indicating that RT increases resulting from CF are not substantially associated with declines in motor preparation, and instead may be attributable to other stages of processing during a simple RT task.
Reaction time is accelerated if a loud (startling) sound accompanies the cue-the "StartReact" effect. Animal studies revealed a reticulospinal substrate for the startle reflex; StartReact may similarly involve the reticulospinal tract, but this is currently uncertain. Here we trained two female macaque monkeys to perform elbow flexion/extension movements following a visual cue. The cue was sometimes accompanied by a loud sound, generating a StartReact effect in electromyogram response latency, as seen in humans. Extracellular recordings were made from antidromically identified corticospinal neurons in primary motor cortex (M1), from the reticular formation (RF), and from the spinal cord (SC; C5-C8 segments). After loud sound, task-related activity was suppressed in M1 (latency, 70-200 ms after cue), but was initially enhanced (70-80 ms) and then suppressed (140-210 ms) in RF. SC activity was unchanged. In a computational model, we simulated a motoneuron pool receiving input from different proportions of the average M1 and RF activity recorded experimentally. Motoneuron firing generated simulated electromyogram, allowing reaction time measurements. Only if ≥60% of motoneuron drive came from RF (≤40% from M1) did loud sound shorten reaction time. The extent of shortening increased as more drive came from RF. If RF provided <60% of drive, loud sound lengthened the reaction time-the opposite of experimental findings. The majority of the drive for voluntary movements is thus likely to originate from the brainstem, not the cortex; changes in the magnitude of the StartReact effect can measure a shift in the relative importance of descending systems.SIGNIFICANCE STATEMENT Our results reveal that a loud sound has opposite effects on neural spiking in corticospinal cells from primary motor cortex, and in the reticular formation. We show that this fortuitously allows changes in reaction time produced by a loud sound to be used to assess the relative importance of reticulospinal versus corticospinal control of movement, validating previous noninvasive measurements in humans. Our findings suggest that the majority of the descending drive to motoneurons producing voluntary movement in primates comes from the reticulospinal tract, not the corticospinal tract.
Simple reaction time (RT) can vary by sex, with males generally displaying faster RTs than females. Although several explanations have been offered, the possibility that response preparation differences may underlie the effect of sex on simple RT has not yet been explored. A startling acoustic stimulus (SAS) can involuntarily trigger a prepared motor response (i.e., StartReact effect), and as such, RT latencies on SAS trials and the proportion of these trials demonstrating startle-reflex EMG in the sternocleidomastoid (SCM) muscle are used as indirect measures of response preparation. The present study employed a retrospective analysis of composite individual participant data (IPD) from 25 datasets published between 2006 and 2019 to examine sex differences in response preparation. Linear mixed effects models assessed the effect of sex on control and SAS RT as well as the proportion of SAS trials with SCM activation while controlling for study design. Results indicated significantly longer control RT in female participants as compared to males (p=.017); however, there were no significant sex differences in SAS RT (p=.441) or the proportion of trials with startle reflex activity (p=.242). These results suggest that sex differences in simple RT are not explained by variations in levels of response preparation but instead may be the result of differences in perceptual processing and/or response initiation processes.
Introduction
The StartReact (SR) effect is the accelerated release of a prepared movement when a startling acoustic stimulus is presented at the time of the imperative stimulus (IS). SR paradigms have been used to study defective control of balance and gait in people with neurological conditions, but differences in emotional state (e.g. fear of failure) may be a potential confounder when comparing patients to healthy subjects. In this study, we aimed to gain insight in the effects of postural threat on the SR effect by manipulating surface height during a postural (lateral step) task and a non-postural (wrist extension) task.
Methods
Eleven healthy participants performed a lateral step perpendicular to the platform edge, and 19 participants performed a wrist extension task while standing at the platform edge. Participants initiated the movement as fast as possible in response to an IS that varied in intensity across trials (80 dB to 121 dB) at both low and high platform height (3.2 m). For the lateral step task, we determined anticipatory postural adjustments (APA) and step onset latencies. For the wrist extension task, muscle onset latencies were determined. We used Wilcoxon signed-rank tests on the relative onset latencies between both heights, to identify whether the effect of height was different for IS intensities between 103 and 118 dB compared to 121 dB.
Results
For both tasks, onset latencies were significantly shortened at 121 dB compared to 80 dB, regardless of height. In the lateral step task, the effect of height was larger at 112 dB compared to 121 dB. The absolute onset latencies showed that at 112 dB there was no such stimulus intensity effect at high as seen at low surface height. In the wrist extension task, no differential effects of height could be demonstrated across IS intensities.
Conclusions
Postural threat had a significant, yet modest effect on shortening of RTs induced by a loud IS, with a mere 3 dB difference between standing on high versus low surface height. Interestingly, this effect of height was specific to the postural (i.e. lateral stepping) task, as no such differences could be demonstrated in the wrist extension task. This presumably reflects more cautious execution of the lateral step task when standing on height. The present findings suggest that applying stimuli of sufficiently high intensity (≥115 dB) appears to neutralize potential differences in emotional state when studying SR effects.
We can observe marked point processes in a wide variety of natural phenomena. Thus, it is important to establish theories and methods for analyzing such observed marked point processes. In a nonlinear time series analysis, the theories are the embedding theorems and the methods are the state space reconstruction from the observed time series. Although it has been revealed that we can reconstruct a state space from a point process without marked values, it has not been clarified yet whether we can reconstruct the state space from a marked point process. Therefore, in this study, we numerically investigated whether a state space could be reconstructed from a marked point process using a delayed coordinate system. To assess the issue, we evaluated the similarity between the interpoint distance distributions on an attractor of the original dynamical system that generated the marked point process and an attractor reconstructed from the marked point process. Results of numerical experiments show that the interpoint distance distributions in the original and reconstructed state spaces are similar, implying that it is possible to reconstruct nonlinear dynamical systems from the observed marked point processes.
