Anthony N Carlsen

University of Ottawa · School of Human Kinetics

Synchronizing hand and foot movements under reactive versus predictive control results in differential timing structures between the responses. Under reactive control, where the movement is externally triggered, the electromyographic (EMG) responses are synchronized, resulting in the hand displacement preceding the foot. Under predictive control, w...

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 an...

Background Transcranial direct current stimulation (tDCS) has been shown to modulate cortical motor excitability and improve bradykinesia symptoms in Parkinson's disease. It is unclear how targeting different cortical motor areas with tDCS may differentially influence upper limb function for individuals diagnosed with PD. Objective This study inve...

Bimanual actions are typically initiated and executed in a temporally synchronous manner, likely due to planning bilateral commands as a single motor "program." Applying high intensity transcranial magnetic stimulation (TMS) to the motor cortex can result in a contralateral cortical silent period that delays reaction time (RT), if timed to coincide...

The simultaneous performance of two motor tasks is challenging. Currently, it is unclear how response preparation of a secondary task is impacted by the performance of a continuous primary task. The purpose of the present experiment was to investigate whether the position of the limb performing the primary cyclical tracking task impacts response pr...

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 mot...

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...

Objective Bradykinesia, defined as slowness of movements, is among the most functionally debilitating symptoms of Parkinson’s disease (PD). Hypoactivation of cortical neurons in supplementary motor area (SMA) has been linked to the progression of bradykinesia symptoms. This study investigated the influence of transcranial direct current stimulation...

The relative contributions of reticulospinal versus corticospinal pathways for movement production are thought to be dependent upon the type of response involved. For example, unilateral distal movements involving the hand and finger have been thought to be primarily driven by corticospinal output, whereas bilateral responses are considered to have...

Responding to multiple stimuli of different modalities has been shown to reduce reaction time (RT), yet many different processes can potentially contribute to multisensory response enhancement. To investigate the neural circuits involved in voluntary response initiation, an acoustic stimulus of varying intensities (80, 105, or 120 dB) was presented...

It has been well documented that a prepared response can be triggered at short latency following the presentation of a loud acoustic stimulus that evokes a reflexive startle response. Different hypotheses have been proposed for this so-called "StartReact" effect, although there is still much debate surrounding the physiological mechanisms involved...

Increasing the intensity of auditory stimuli has been shown to produce faster simple reaction times (RTs). Typical explanations for this effect involve earlier detection of the more intense stimulus; however, these explanations fail to consider how stimulus intensity may impact response initiation processing. To investigate the mechanism responsibl...

The "StartReact" effect refers to the rapid involuntary triggering of a prepared movement in response to a loud startling acoustic stimulus (SAS). This effect is typically confirmed by the presence of short latency EMG activity in startle reflex-related muscles such as the sternocleidomastoid (SCM); however, there is debate regarding the specific n...

Recent research has suggested that visual discrimination and detection may be enhanced during movement preparation and execution, respectively. The current study examined if visual perceptual processing is augmented prior to or during a movement through the use of an Inspection Time (IT) task. The IT task involved briefly presenting (e.g., 15–105 m...

Corticospinal output pathways have typically been considered to be the primary driver for voluntary movements of the hand/forearm; however, more recently, reticulospinal drive has also been implicated in the production of these movements. While both pathways may play a role, the reticulospinal tract is thought to have stronger connections to flexor...

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...

A distinct learning advantage has been shown when participants control their knowledge of results (KR) scheduling during practice compared to when the same KR schedule is imposed on the learner without choice (i.e., yoked schedules). Although the learning advantages of self-controlled KR schedules are well-documented, the brain regions contributing...

During reaction time (RT) tasks, participants respond faster to multiple stimuli from different modalities as compared to a single stimulus, a phenomenon known as the redundant signal effect (RSE). Explanations for this effect typically include coactivation arising from the multiple stimuli, which results in enhanced processing of one or more respo...

Humans are able to proactively inhibit a particular motor response when provided with a precue in a bimanual selective stopping task (e.g., Maybe Stop Right Hand). We investigated how preparation affects proactive selective inhibition, as previous experiments have been performed in a paradigm where the ability to prepare responses ahead of the go-s...

The presentation of a startling acoustic stimulus (SAS) in a simple reaction time (RT) task significantly reduces RT due to the involuntary early initiation of a prepared movement; however, the underlying neural mechanism remains unclear. It has been proposed that a SAS triggers a cortically stored motor program by involuntarily increasing initiati...

During continuous bimanual coordination, in-phase (IP; 0° relative phase) and anti-phase (AP; 180° relative phase) patterns can be stably performed without practice. Paradigms in which participants are required to intentionally switch between these coordination patterns have been used to investigate the interaction between the performer's intention...

In a typical go/no-go task a single imperative stimulus is presented each trial, either a go or no-go stimulus. Participants are instructed to initiate a known response upon appearance of the go-signal and withhold the response if the no-go signal is presented. It is unclear whether the go-response is prepared in advance of the imperative stimulus...

Increased reaction times (RT) during choice-RT tasks stem from a requirement for additional processing as well as reduced motor-specific preparatory activation. Transcranial direct current stimulation (tDCS) can modulate primary motor cortex excitability, increasing (anodal stimulation) or decreasing (cathodal stimulation) excitability in underlyin...

During a simple reaction time (RT) task, movements can be initiated early and involuntarily through presentation of a loud startling acoustic stimulus (SAS), a phenomenon termed the StartReact effect. In order to infer that activity in startle-related structures led to the early response triggering, it is important to observe a concurrent startle r...

In a stop-signal task participants are instructed to initiate a movement in response to a go-signal, but to inhibit this movement if an infrequent stop-signal is presented after the go. Reaction time (RT) in a stop-signal task is typically longer compared to a simple-RT task, which may be attributed to a reduced readiness to initiate the response c...

Increasing the complexity of a movement has been shown to result in longer simple reaction time (RT), which has been attributed to sequencing or timing requirements following the go-signal. However, RT differences may also be due to differences in corticospinal excitability (CE) as previous studies have found an enhanced excitatory state of cortico...

When a startling acoustic stimulus (SAS) is presented during a simple reaction time (RT) task it can trigger the prepared response through an involuntary initiation pathway. Previous research modelling the effects of presenting a SAS at various intervals following a non-startling auditory imperative signal (IS) suggested that involuntary initiation...

A loud acoustic stimulus that elicits a startle reflex has long been used to study the neurophysiology of cortical and subcortical neural circuits. More recent investigations have shown that startle can act as an early trigger for prepared actions, suggesting a brainstem role in the preparation and initiation of actions. However, in order to attrib...

Recent work has shown that preplanned motor programs can be rapidly released via fast conducting pathways using a startling acoustic stimulus. Our question was whether the startle-elicited response might also release a recently learned internal model, which draws on experience to predict and compensate for expected perturbations in a feedforward ma...

Previous studies have used a secondary probe reaction time (RT) task to assess attentional demands of a primary task. The current study used a startling acoustic stimulus (SAS) in a probe RT paradigm to test the hypothesis that attentional resources would be directly related to limitations in response preparation. Participants performed an easy or...

When a startling acoustic stimulus (SAS) is presented in a simple reaction time (RT) task, response latency is significantly shortened. The present study used a SAS in a psychological refractory period (PRP) paradigm to determine if a shortened RT1 latency would be propagated to RT2. Participants performed a simple RT task with an auditory stimulus...

Movements that are executed or imagined activate a similar subset of cortical regions, but the extent to which this activity represents functionally equivalent neural processes is unclear. During preparation for an executed movement, presentation of a startling acoustic stimulus (SAS) evokes a premature release of the planned movement with the spat...

The present study investigated whether differences in reaction time (RT) between movements initiated to a visual cue (directly cued) versus movements initiated to a location other than the visual cue (indirectly cued) arise because of varying levels of inhibition within the motor system during response preparation. Unlike typical visuomotor mental...

A recent study by Marinovic et al. (J. Neurophysiol., 2013, 109: 996–1008) used a loud acoustic stimulus to probe motor preparation in a simple reaction time (RT) task. Based on decreasing RT latency and increases in motor output measures as the probe stimulus approached the “go” stimulus, the authors concluded that response-related activation incr...

The learning advantages of self-controlled feedback schedules compared to yoked schedules have been attributed to motivational influences and/or information-processing activities with many researchers adopting the motivational perspective in recent years. Chiviacowsky and Wulf (2005) found retention performance could be equally optimized when the f...

The production of movement in a simple reaction time task can be separated into two time periods: the foreperiod, which is thought to include preparatory processes, and the reaction time interval, which includes initiation processes. To better understand these processes, transcranial magnetic stimulation has been used to probe corticospinal excitab...

Transcranial direct current stimulation (tDCS) is a non-invasive stimulation method that can induce transient polarity-specific neuroplastic changes in cortical excitability lasting up to 1 h post-stimulation. While excitability changes with stimulation over the primary motor cortex have been well documented, the functional effects of stimulation o...

Coordinated bimanual oscillatory movements often involve one of two intrinsically stable phasing relationships characterized as in-phase (symmetrical) or anti-phase (asymmetrical). The in-phase mode is typically more stable than anti-phase and if movement frequency is increasing during anti-phase movements, a spontaneous transition to the in-phase...

Aim: To reevaluate the previous hypothesis that greater reductions in self-paced exercise intensity in the heat are mediated by early differences in the rate of body heat storage (S). Methods: Eight trained volunteers cycled in 19 °C/1.8 kPa (COOL), 25 °C/1.2 kPa (NORM), and 34 °C/1.6 kPa (HOT), while maintaining an RPE of 16. Potential differen...

The current study examined the process of response initiation in a simple reaction time (RT) task using a startling acoustic stimulus (SAS), which has been shown to trigger a prepared movement through an involuntary initiation pathway. The SAS was presented within the RT interval (concurrent with, and 25, 50, 75, 100, and 125ms following the "go" s...

The present study was designed to investigate the mechanism associated with dual-task interference in a psychological refractory period (PRP) paradigm. We used a simple reaction time paradigm consisting of a vocal response (R1) and key-lift task (R2) with a stimulus onset asynchrony (SOA) between 100ms and 1500ms. On selected trials we implemented...

Previous research has shown that the supplementary motor area (SMA) is critical in movement inhibition. Recently it was shown that applying transcranial direct current stimulation (tDCS) over SMA affected participants' ability to inhibit their movement in a stop-signal reaction time task (Hsu et al., 2011). Of interest in the current study was whet...

Targeted reciprocal aiming movements are pervasive in everyday life, but it is unclear how the timing parameters between task elements affect the preparation of these movements. This study used a loud (124 dB) startling acoustic stimulus (SAS) to probe how changes in the pause time between the outward and return components of a reciprocal aiming ta...

Muscles involved in rapid, targeted movements about a single-joint often display a triphasic (agonist - antagonist - agonist) electromyographic (EMG) pattern. Early work using movement perturbations suggested that for short movements, the entire EMG pattern was prepared and initiated in advance (Wadman et al. 1979), whereas more recent TMS evidence...

Previous investigations comparing direct versus indirectly cued movements have consistently shown that indirectly cued movements take longer to prepare (Neely and Heath, 2010) and involve the recruitment of additional brain areas (Connolly et al., 2000). This increase in processing time has been associated with the additional cognitive transformati...

The purpose of the current study was to examine the relationship between movement preparation and excitability of subcortical motor circuits, as measured by the reflexive response to a startling acoustic stimulus. We compared the size and incidence of activation in the sternocleidomastoid (startle indicator) from participants completing either a si...

This study investigated whether different rates of decline in self-selected work rate (W) were mediated by early differences in heat storage. Five males cycled at a W to maintain a perceived exertion of 16 (Borg scale) at 35°C and 25°C. Heat production (Hprod) was estimated via indirect calorimetry. Esophageal (Tes) and skin (Tsk) temperatures, as...

In this review we provide a summary of the observations made regarding advance preparation of the motor system when presenting a startling acoustic stimulus (SAS) during various movement tasks. The predominant finding from these studies is that if the participant is prepared to make a particular movement a SAS can act to directly and quickly trigge...

In reaction time (RT) tasks where fast ballistic movements are required, the requisite action is generally preplanned to enable the quickest responses. When a loud acoustic stimulus (e.g., >120 dB) that elicits a startle response is presented during the preplanning phase, the movement is triggered involuntarily and at a sufficiently short enough la...

In a choice reaction time (RT) paradigm, providing partial advance information (a precue) about the upcoming response has been shown to decrease RT, presumably due to preprogramming of the precued parameters. When advance information about a particular aspect of a movement is provided (precued), several different strategies might be used to prepare...

We investigated the processes underlying stimulus-response compatibility by using a lateralized auditory stimulus in a simple and choice reaction time (RT) paradigm. Participants were asked to make either a left or right key lift in response to either a control (80dB) or startling (124dB) stimulus presented to either the left ear, right ear, or bot...

When an acoustic stimulus that is sufficiently intense to elicit a startle response is delivered in conjunction with the "go" signal in a simple reaction time (RT) task, RT is greatly reduced. It has been suggested that this effect is due to the startle interacting with voluntary response channels to directly trigger the pre-programmed action. Alte...

Recent studies have used a loud (> 120 dB) startle-eliciting acoustic stimulus as a probe to investigate early motor response preparation in humans. The use of a startle in these studies has provided insight into not only the neurophysiological substrates underlying motor preparation, but also into the behavioural response strategies associated wit...

In the present experiment, the temporal predictability of response time was systematically manipulated to examine its effect on the time course of motor pre-programming and release of the intended movement by an acoustic startle stimulus. Participants performed a ballistic right wrist extension task in four different temporal conditions: 1) a varia...

For synchronous bimanual movements, we have shown that a different amplitude can be prepared for each limb in advance and this preparation improves with practice (Maslovat et al. 2008). In the present study, we tested whether an asynchronous bimanual movement can also be prepared in advance and be improved with practice. Participants practiced (160...

When one or more response dimensions in a choice reaction time (RT) task are provided beforehand (or precued), RT decreases, indicating that the precued part of a response was prepared in advance. In this study, a startling acoustic stimulus was used to investigate the amount of preprogramming that occurs when part of the response is precued becaus...

Recent studies using a reaction time (RT) task have reported that a preprogrammed response could be triggered directly by a startling acoustic stimulus (115-124 dB) presented along with the usual "go" signal. It has been suggested that details of the upcoming response could be stored subcortically and are accessible by the startle volley, directly...

Previous findings from experiments involving anticipation-timing tasks have indicated that a point in time may exist after which a participant is committed to producing a pre-programmed movement. For example, if a "stop" signal is given too long after a "go" signal but prior to movement initiation, the response is often still produced. It has been...

The purpose of the current study was to examine the effects of practice on the advance preparation of an asymmetrical bimanual movement. Participants performed 170 trials of a discrete bimanual aiming movement where the right arm moved twice the amplitude of the left, in response to an auditory "go" signal. During three of the first and last ten tr...

Presenting a startling stimulus in a simple reaction time (RT) task, can involuntarily trigger the pre-programmed response. However, this effect is not seen when the response is programmed following the imperative stimulus (IS) providing evidence that a startle can only trigger pre-programmed responses. In a "Go/No-go" (GNG) RT task the response ma...

Recent experiments have reported increased endpoint accuracy for movements performed in the lower vs. the upper visual field, suggesting that there is superior feedback-based processing in the lower visual field owing to a visuomotor subsystem processing advantage. Differences, however, in the perceptual subsystem may also play a role in the lower...

Recent experiments pairing a startling stimulus with a simple reaction time (RT) task have shown that when participants are startled, a prepared movement was initiated earlier in comparison to voluntary initiation. It has been argued that the startle acts to trigger the response involuntarily. However, an alternative explanation is that the decreas...

Previous research has shown that a startle 'go' stimulus, presented at a constant latency with respect to a warning stimulus, is capable of eliciting an intended voluntary movement in a simple reaction time (RT) task at very short latencies without involvement of the cerebral cortex (Carlsen et al. in Exp Brain Res 152:510-518, 2003; J Motor Behav...

The purpose of this experiment was to examine the potential interaction between visual and vestibular inputs as participants walked towards 1 of 3 targets located on a barrier 5m away. Visual and vestibular inputs were perturbed with displacing prisms and galvanic vestibular stimulation (GVS), respectively. For each target there were three vision c...

Displacing prisms and galvanic stimulation were used to examine visual-vestibular interactions during target-directed gait. Participants walked towards a wall 6 m away. After taking four steps, a target on the wall, located directly in front or to the right of the participant, was illuminated. Participants continued walking towards the target. Galv...