Visual perceptual processing is unaffected by cognitive fatigue.

Cognitive fatigue (CF) can lead to an increase in the latency of simple reaction time, although the processes involved in this delay are unknown. One potential explanation is that a longer time may be required for sensory processing of relevant stimuli. To investigate this possibility, the current study used a visual inspection time task to measure perceptual processing speed before and after a CF (math and memory) or non-fatiguing (documentary film) intervention. Subjective fatigue and simple reaction time significantly increased following the CF, but not the non-fatiguing intervention, confirming that CF was induced. Conversely, there was no effect of CF on inspection time task performance. It was therefore concluded that the speed of perceptual processing is not significantly impacted by CF, and thus is unlikely to underlie CF-related reaction time increases. Instead, increases in simple reaction time latency in CF may be due to delays in response preparation or initiation.

Increased EMG-EMG coherence in the theta and alpha bands during bimanual force modulation.

During the execution of movements, error correction processes have been inferred by EEG activation at oscillation frequencies in the theta (4-8 Hz) and alpha (8-12 Hz) bands. The current study examined whether evidence for error detection and correction could be found at the muscular level through the use of EMG-EMG coherence, which quantifies the amount of synchronous EMG activity between limbs in the frequency domain. Participants (n = 13) performed a bimanual force production task involving either wrist flexors or extensors under conditions in which the force was to be held constant or continuously modulated. As predicted, the modulation of changing force output resulted in significantly greater force variability and increased EMG-EMG coherence throughout the theta and alpha band for both flexor and extensor responses. These results are consistent with EEG activation frequencies associated with error correction, motor reprogramming and sustained attention and indicate that evidence for these cortical processes can also be observed at the muscular level in the form of correlated EMG frequency content between limbs.

Startle-triggered responses indicate reticulospinal drive is larger for voluntary shoulder versus finger movements.

Recent primate studies have implicated a substantial role of reticulospinal pathways in the production of various voluntary movements. A novel way to assess the relative reticulospinal contributions in humans is through the use of a "StartReact" paradigm where a startling acoustic stimulus (SAS) is presented during a simple reaction time (RT) task. The StartReact response is characterized by short-latency triggering of a prepared response, which is attributed to increased reticulospinal drive associated with startle reflex activation. The current study used a StartReact protocol to examine differences in reticulospinal contributions between proximal and distal effectors by examining EMG onset latencies in lateral deltoid and first dorsal interosseous during bilateral shoulder or finger abduction. The magnitude of the StartReact effect, and thus relative reticulospinal drive, was quantified as the difference in RT between startle trials in which startle-reflex related EMG activation in the sternocleidomastoid (SCM) was present (SCM +) versus absent (SCM -). A significantly larger StartReact effect was observed for bilateral shoulder abduction versus bimanual finger abduction and a higher incidence of SCM + trials occurred in the proximal task. Additionally, both startle reflex and response-related EMG measures were larger on SCM + trials for the shoulder versus finger task. These results provide compelling novel evidence for increased reticulospinal activation in bilateral proximal upper-limb movements.

Investigating motor preparation in synchronous hand and foot movements under reactive vs. predictive control.

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, where the movement is self-paced, the motor commands are organized such that the displacement onset occurs relatively synchronously, requiring the EMG onset of the foot to precede that of the hand. The current study used a startling acoustic stimulus (SAS), which can involuntarily trigger a prepared response, to investigate whether these results are due to differences in a pre-programmed timing structure of the responses. Participants performed synchronous movements of the right heel and right hand under both reactive and predictive modes of control. The reactive condition involved a simple reaction time (RT) task, whereas the predictive condition involved an anticipation-timing task. On selected trials, a SAS (114 dB) was presented 150 ms prior to the imperative stimulus. Results from the SAS trials revealed that while the differential timing structures between the responses was maintained under both reactive and predictive control, the EMG onset asynchrony under predictive control was significantly smaller following the SAS. These results suggest that the timing between the responses, which differs between the two control modes, is pre-programmed; however, under predictive control, the SAS may accelerate the internal timekeeper, resulting in a shortened between-limb delay.

Slowed reaction times in cognitive fatigue are not attributable to declines in motor preparation.

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.

Trouble doing two differently timed actions at once: What is the problem?

It is nearly impossible to concurrently initiate and execute two motor actions with independent timing. For example, it is difficult to tap one rhythm with the right hand while tapping a different rhythm with the left hand, even after these rhythms have been practiced individually. However, if this task is restructured so that it is represented internally as one action done by two hands rather than as two actions, one with each hand, these same rhythms can be produced easily. These findings, which indicate that motor action is limited to a single time base, are in marked contrast with the fact that it is easy to mechanically generate two independent rhythms simply by using mechanisms that are not linked to each other. After an in-depth review of the extensive research on this topic we propose a new theoretical interpretation. This attributes the difficulty to a fundamental constraint that prevents initiation of any motor action until after completion of programming the internal code that controls timing. The timing code is volatile in the sense that it must be generated immediately prior to the action to be controlled and then it must be implemented without delay. This constraint, which has been studied as it applies to single motor actions, can be extended to concurrent motor actions where it can account for the difficulty in doing two differently timed actions at once. Additional phenomena which may be attributed to this constraint are described in a concluding section. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A TMS-induced cortical silent period delays the contralateral limb for bimanual symmetrical movements and the reaction time delay is reduced on startle trials.

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 with the final motor output stage. The current study examined the impact of a unilateral TMS silent period on the RT and interlimb timing of bilateral wrist extension. In addition, because a loud, startling acoustic stimulus (SAS) can result in the involuntary release of preprogrammed actions via increased reticulospinal activation, it was of interest whether startle-induced speeding of response initiation would moderate the impact of the TMS-induced RT delay. Participants performed blocks of unilateral and bilateral wrist extension in response to an acoustic (82 dB) go-signal. On selected trials, either TMS was applied to the left motor cortex 70 ms before the expected EMG response onset, a SAS (120 dB) replaced the go-signal, or both TMS and SAS were delivered. Results showed that TMS led to a significant RT delay in the right limb during both unimanual and bimanual extension but had no impact on the left limb initiation. In addition, the magnitude of the right limb RT delay was smaller when the response was triggered by a SAS. These results imply that preplanned bimanually synchronous movements are susceptible to lateralized dissociation late into the cortical motor output stage and movements triggered by startle involve increased reticulospinal output.NEW & NOTEWORTHY Bilateral responses are typically planned synchronously and performed symmetrically. Here, we show that delaying the initiation of one limb using transcranial magnetic stimulation (TMS) to produce a cortical silent period does not impact the other limb during bimanual movements. Also, the TMS-induced delay is reduced when a startling acoustic stimulus (SAS) triggers the movement. These results confirm that tightly coupled bilateral responses can be dissociated by contralateral TMS- and SAS-triggered responses involve greater reticulospinal output.

Response preparation of a secondary reaction time task is influenced by movement phase within a continuous visuomotor tracking task.

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 preparation of a secondary reaction time task. Participants (n = 20) performed a continuous tracking task with their left hand that involved cyclical and targeted wrist flexion and extension. Occasionally, a probe reaction time task requiring isometric wrist extension was performed with the right hand in response to an auditory stimulus (80 or 120 dB) that was triggered when the left hand passed through one of 10 locations identified within the movement cycle. On separate trials, transcranial magnetic stimulation was applied over the left primary motor cortex and triggered at the same 10 stimulus locations to assess corticospinal excitability associated with the probe reaction time task. Results revealed that probe reaction times were significantly longer and motor-evoked potential amplitudes were significantly larger when the left hand was in the middle of a movement cycle compared with an endpoint, suggesting that response preparation of a secondary probe reaction time task was modulated by the phase of movement within the continuous primary task. These results indicate that primary motor task requirements can impact preparation of a secondary task, reinforcing the importance of considering primary task characteristics in dual-task experimental design.

Retrospective composite analysis of StartReact data indicates sex differences in simple reaction time are not attributable to response preparation.

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.

Response triggering by an acoustic stimulus increases with stimulus intensity and is best predicted by startle reflex activation.

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.

Bimanual but not unimanual finger movements are triggered by a startling acoustic stimulus: evidence for increased reticulospinal drive for bimanual responses.

The relative contributions of reticulospinal versus corticospinal pathways for movement production are thought to be dependent on 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 greater reticulospinal drive. The current study investigated whether a difference in the relative contribution of reticulospinal drive to a bimanual versus unimanual finger movement could be assessed using a StartReact protocol. The StartReact effect refers to the early and involuntary initiation of a prepared movement when a startle reflex is elicited. A decreased response latency on loud stimulus trials where a startle reflex is observed in sternocleidomastoid (SCM+ trials) confirms the StartReact effect, which is attributed to increased reticulospinal drive associated with engagement of the startle reflex circuitry. It was predicted that a StartReact effect would be absent for the predominantly corticospinal-mediated unimanual finger movement but present for the bimanual finger movement due to stronger reticulospinal drive. Results supported both predictions as reaction time was statistically equivalent for SCM+ and SCM- trials during unimanual finger movements but significantly shorter for SCM+ trials during bimanual finger movements. These results were taken as strong and novel evidence for increased reticulospinal output for bimanual finger movements.NEW & NOTEWORTHY The relative contributions of reticulospinal and corticospinal pathways to movement initiation are relatively unknown but appear to depend on the involved musculature. Here, we show that unimanual finger movements, which are predominantly initiated via corticospinal pathways, are not triggered at short latency by a startling acoustic stimulus (SAS), while bimanual finger movements are triggered by the SAS. This distinction is attributed to increased reticulospinal drive for bilateral responses.

Programming of action timing cannot be completed until immediately prior to initiation of the response to be controlled.

We consider, in depth, findings from across 6 decades regarding generating a motor response in a simple reaction-time (i.e., delayed response) paradigm. The early results robustly show a response complexity effect whereby the more response elements, the longer the simple reaction time (RT). This effect is puzzling because it indicates that preparation of some aspect of a response cannot be completed prior to the simple RT interval even though a precue had identified the response in advance. Results obtained during the past 10 years indicate that this finding reflects a restriction in advance preparation of the code that controls timing of the onsets for elements making up the response. This code cannot be prepared prior to the simple RT interval even though the parameters to be achieved by the response can be established earlier so that the difficulty of their selection does not influence RT. The general principle that emerges from these studies is that the abstract goal for a response can be determined in advance, but programming of action timing cannot be completed until immediately prior to initiation of the response to be controlled. We suggest that this restriction may arise because limitations in working memory prevent temporary storage of the timing code even though the abstract response goal can be stored until needed. Regardless of its origin, the limitation regarding preparation of response timing represents a fundamental feature in control of motor action.

An unperceived acoustic stimulus decreases reaction time to visual information in a patient with cortical deafness.

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 during a visual RT task to a patient with profound bilateral cortical deafness and an intact auditory brainstem response. Despite being unable to consciously perceive sound, RT was reliably shortened (~100 ms) on trials where the unperceived acoustic stimulus was presented, confirming the presence of multisensory response enhancement. Although the exact locus of this enhancement is unclear, these results cannot be attributed to involvement of the auditory cortex. Thus, these data provide new and compelling evidence that activation from subcortical auditory processing circuits can contribute to other cortical or subcortical areas responsible for the initiation of a response, without the need for conscious perception.

Increased auditory stimulus intensity results in an earlier and faster rise in corticospinal excitability.

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 responsible for the auditory stimulus intensity effect, transcranial magnetic stimulation (TMS) was applied at various times during the simple RT interval (equivalent to 0, 30, 45, 60, and 75% of baseline RT) to examine changes in corticospinal excitability after a go-signal of varying intensity (60, 70, 80, or 90 dB). Premotor RT data confirmed a stimulus intensity effect whereby the 90 dB stimulus resulted in faster RTs than all other intensities. Analysis of motor evoked potential (MEP) amplitude elicited by TMS across stimulus intensity conditions revealed that in the 80 dB and 90 dB conditions, corticospinal excitability began to increase earlier from baseline (pre-stimulus) levels, supporting the detection hypothesis. In addition, MEP amplitude increased at a greater rate during the RT interval for the 90 dB condition, indicative of impacts on response initiation. These results indicate that stimulus intensity effects result from a combination of earlier detection and faster initiation.

Startle and the StartReact Effect: Physiological Mechanisms.

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 in the observed reduction in reaction time (RT). In this review, we outline the various neurophysiological explanations underlying the StartReact effect and summarize the data supporting, and at times opposing, each possibility. Collectively, the experimental results do not unequivocally support a single explanation and we suggest the most parsimonious mechanism may involve a hybrid framework involving a distribution of neural pathways. Specifically, we propose that multiple node networks at the cortical, brainstem, and spinal levels are involved in response preparation and initiation, and the relative contributions of these structures depends on the type of stimulus delivered and the type of movement required. This approach may lead to greater understanding of the pathways involved in response preparation, initiation, and execution for both healthy and motor disordered populations.

StartReact effects are dependent on engagement of startle reflex circuits: support for a subcortically mediated initiation pathway.

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 electromyographic activity in startle reflex-related muscles such as the sternocleidomastoid (SCM); however, there is debate regarding the specific neural pathways involved in the StartReact effect. Some research has implicated a subcortically mediated pathway, which would predict different response latencies depending on the presence of a startle reflex. Alternatively, other research has suggested that this effect involves the same pathways responsible for voluntary response initiation and simply reflects higher preparatory activation levels, and thus faster voluntary initiation. To distinguish between these competing hypotheses, the present study assessed preparation level during a simple reaction time (RT) task involving wrist extension in response to a control tone or a SAS. Premotor RT and startle circuitry engagement (as measured by SCM activation) were determined for each trial. Additionally, preparation level at the go signal on each trial was measured using motor-evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS). Results showed that SAS trial RTs were significantly shorter (P = 0.009) in the presence of startle-related SCM activity. Nevertheless, preparation levels (as indexed by MEP amplitude) were statistically equivalent between trials with and without SCM activation. These results indicate that the StartReact effect relates to engagement of the startle reflex circuitry rather than simply being a result of an increased level of preparatory activation.NEW & NOTEWORTHY The neural mechanism underlying the early triggering of goal-directed actions by a startling acoustic stimulus (SAS) is unclear. We show that although significant reaction time differences were evident depending on whether the SAS elicited a startle reflex, motor preparatory activation was the same. Thus, in a highly prepared state, the short-latency responses associated with the StartReact effect appear to be related to engagement of startle reflex circuitry, not differences in motor preparatory level.

Influence of kinesthetic motor imagery and effector specificity on the long-latency stretch response.

The long-latency "reflexive" response (LLR) following an upper limb mechanical perturbation is generated by neural circuitry shared with voluntary control. This feedback response supports many task-dependent behaviors and permits the expression of goal-directed corrections at latencies shorter than voluntary reaction time. An extensive body of literature has demonstrated that the LLR shows flexibility akin to voluntary control, but it has not yet been tested whether instruction-dependent LLR changes can also occur in the absence of an overt voluntary response. The present study used kinesthetic motor imagery (experiment 1) and instructed participants to execute movement with the unperturbed contralateral limb (experiment 2) to explore the relationship between the overt production of a voluntary response and LLR facilitation. Activity in stretched right wrist flexors were compared with standard "do not-intervene" and "compensate" conditions. Our findings revealed that on ~40% of imagery and ~50% of contralateral trials, a response occurred during the voluntary epoch in the stretched right wrist flexors. On these "leaked" trials, the early portion of the LLR (R2) was facilitated and displayed a similar increase to compensate trials. The latter half of the LLR (R3) showed further modulation, mirroring the patterns of voluntary epoch activity. By contrast, the LLR on "non-leaked" imagery and contralateral trials did not modulate. We suggest that even though a hastened voluntary response cannot account for all instruction-dependent LLR modulation, the overt execution of a response during the voluntary epoch in the same muscle(s) as the LLR is a prerequisite for instruction-dependent facilitation of this feedback response.NEW & NOTEWORTHY Using motor imagery and contralateral responses, we provide novel evidence that facilitation of the long-latency reflex (LLR) requires the execution of a response during the voluntary epoch. A high proportion of overt response "leaks" were found where the mentally simulated or mirrored response appeared in stretched muscle. The first half of the LLR was categorically sensitive to the appearance of leaks, whereas the latter half displayed characteristics closely resembling activity in the ensuing voluntary period.

The effect of response complexity on simple reaction time occurs even with a highly predictable imperative stimulus.

It is well known that increasing the complexity of the required response results in a corresponding increase in simple reaction time (RT). This "response complexity effect" has typically been attributed to increased time required to prepare some aspect of the response; however, most studies examining the response complexity effect have used an unpredictable foreperiod, which does not allow for optimal preparation to occur. Thus, it is conceivable that response complexity effects are influenced by an inability to predict the occurrence of the go-signal. In order to examine this possibility, participants (N = 36) were randomly assigned to one of four groups that differed in predictability of the go signal: 1) 2500-3500 ms random foreperiod; 2) 3000 ms constant foreperiod; 3) 1000 ms constant foreperiod; 4) 3000 ms constant foreperiod with a 1000 ms countdown timer. Participants performed one of three different key-press responses in a simple RT paradigm: 1) single key-press; 2) three key-presses with an equal/isochronous time interval between presses; 3) three key-presses with an unequal/non-isochronous time interval between presses. Results confirmed that while the countdown timer group had an overall reduced RT, response complexity effects were present and of similar magnitude for all groups in all testing blocks. This confirms that predictability of the go signal does not affect the response complexity effect.

High-intensity transcranial magnetic stimulation reveals differential cortical contributions to prepared responses.

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. Although both pathways may play a role, the reticulospinal tract is thought to have stronger connections to flexor muscles than to extensors. Similarly, movements involuntarily triggered via a startling acoustic stimulus (SAS) are believed to receive greater reticular input than voluntary movements. To investigate a differential role of reticulospinal drive depending on movement type or acoustic stimulus, corticospinal drive was transiently interrupted using high-intensity transcranial magnetic stimulation (TMS) applied during the reaction time (RT) interval. This TMS-induced suppression of cortical drive leads to RT delays that can be used to assess cortical contributions to movement. Participants completed targeted flexion and extension movements of the wrist in a simple RT paradigm in response to a control auditory go signal or SAS. Occasionally, suprathreshold TMS was applied over the motor cortical representation for the prime mover. Results revealed that TMS significantly increased RT in all conditions. There was a significantly longer TMS-induced RT delay seen in extension movements than in flexion movements and a greater RT delay in movements initiated in response to control stimuli compared with SAS. These results suggest that the contribution of reticulospinal drive is larger for wrist flexion than for extension. Similarly, movements triggered involuntarily by an SAS appear to involve greater reticulospinal drive, and relatively less corticospinal drive, than those that are voluntarily initiated. NEW & NOTEWORTHY Through the use of the transcranial magnetic stimulation-induced silent period, we provide novel evidence for a greater contribution of reticulospinal drive, and a relative decrease in corticospinal drive, to movements involuntarily triggered by a startle compared with voluntary movements. These results also provide support for the notion that both cortical and reticular structures are involved in the neural pathway underlying startle-triggered movements. Furthermore, our results indicate greater reticulospinal contribution to wrist flexion than extension movements.

Visual processing is diminished during movement execution.

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 ms) a "pi" figure with differing leg lengths, which was then immediately masked for 400 ms to prevent retinal afterimages. Participants were subsequently required to choose which of the two legs was longer. In Experiment 1, participants (n = 28) completed the IT task under three movement conditions: no-movement (NM), foreperiod (FP), and peak velocity (PV). In the NM condition, participants solely engaged in the IT paradigm. In the FP condition, the IT stimulus was presented prior to movement execution when response planning was expected to occur. Finally, in the PV condition, participants made a rapid movement to a target, and the IT stimulus was presented when their limb reached peak velocity. In Experiment 2, participants (n = 18) also performed the IT task in the PV and NM condition; however, vision of the limb's motion was made available during the PV trials (PV-FV) to investigate the potential influence of visual feedback on IT performance. Results showed no significant differences in performance in the IT task between the NM and FP conditions, suggesting no enhancement of visual processing occurred due to response preparation (Experiment 1). However, IT performance was significantly poorer in the PV condition in comparison to both the NM and FP conditions (Experiment 1), and was even worse when visual feedback was provided (Experiment 2). Together, these findings suggest that visual perceptual processing is degraded during execution of a fast, goal-directed movement.