First trial and StartReact effects induced by balance perturbations to upright stance

2013 ◽  
Vol 110 (9) ◽  
pp. 2236-2245 ◽  
Author(s):  
A. D. Campbell ◽  
J. W. Squair ◽  
R. Chua ◽  
J. T. Inglis ◽  
M. G. Carpenter
Keyword(s):  
Startle Response ◽  
Support Surface ◽  
Wrist Movement ◽  
Repeated Presentation ◽  
Trial Effect ◽  
Acoustic Stimuli ◽  
Postural Responses ◽  
Startreact Effect ◽  
Startling Stimulus ◽  
Repeated Test

Postural responses (PR) to a balance perturbation differ between the first and subsequent perturbations. One explanation for this first trial effect is that perturbations act as startling stimuli that initiate a generalized startle response (GSR) as well as the PR. Startling stimuli, such as startling acoustic stimuli (SAS), are known to elicit GSRs, as well as a StartReact effect, in which prepared movements are initiated earlier by a startling stimulus. In this study, a StartReact effect paradigm was used to determine if balance perturbations can also act as startle stimuli. Subjects completed two blocks of simple reaction time trials involving wrist extension to a visual imperative stimulus (IS). Each block included 15 CONTROL trials that involved a warning cue and subsequent IS, followed by 10 repeated TEST trials, where either a SAS (TESTSAS) or a toes-up support-surface rotation (TESTPERT) was presented coincident with the IS. StartReact effects were observed during the first trial in both TESTSAS and TESTPERT conditions as evidenced by significantly earlier wrist movement and muscle onsets compared with CONTROL. Likewise, StartReact effects were observed in all repeated TESTSAS and TESTPERT trials. In contrast, GSRs in sternocleidomastoid and PRs were large in the first trial, but significantly attenuated over repeated presentation of the TESTPERT trials. Results suggest that balance perturbations can act as startling stimuli. Thus first trial effects are likely PRs which are superimposed with a GSR that is initially large, but habituates over time with repeated exposure to the startling influence of the balance perturbation.

First Trial Postural Reactions to Unexpected Balance Disturbances: A Comparison With the Acoustic Startle Reaction

2010 ◽  
Vol 104 (5) ◽  
pp. 2704-2712 ◽  
Author(s):  
Lars B. Oude Nijhuis ◽  
John H. J. Allum ◽  
Josep Valls-Solé ◽  
Sebastiaan Overeem ◽  
Bastiaan R. Bloem
Keyword(s):  
Muscle Activation ◽  
Acoustic Startle ◽  
Muscle Synergy ◽  
Trunk Muscles ◽  
Common Element ◽  
Startle Reaction ◽  
Support Surface ◽  
Postural Reactions ◽  
Acoustic Stimuli ◽  
Postural Responses

Unexpected support-surface movements delivered during stance elicit “first trial” postural reactions, which are larger and cause greater instability compared with habituated responses. The nature of this first trial reaction remains unknown. We hypothesized that first trial postural reactions consist of a generalized startle reaction, with a similar muscle synergy as the acoustic startle response, combined with an automatic postural reaction. Therefore we compared acoustic startle responses to first trial postural reactions. Eight healthy subjects stood on a support surface that unexpectedly rotated backwards 10 times, followed by 10 startling acoustic stimuli, or vice versa. Outcome measures included full body kinematics and surface EMG from muscles involved in startle reactions or postural control. Postural perturbations and startling acoustic stimuli both elicited a clear first trial reaction, as reflected by larger kinematic and EMG responses. The ensuing habituation rate to repeated identical stimuli was comparable for neck and trunk muscles in both conditions. Onset latencies in neck muscles occurred significantly later for first trial perturbations compared with startle responses, but earlier in trunk muscles. Our results show that platform tilting initially induces reactions larger than needed to maintain equilibrium. For neck and trunk muscles, these first trial postural reactions resembled acoustic startle reflexes. First trial postural reactions may be triggered by interaction of afferent volleys formed by somatosensory and vestibular inputs. Acoustic startle reactions may also be partially triggered by vestibular inputs. Similar muscle activation driven by vestibular inputs may be the common element of first trial postural responses and acoustic startle reactions.

Startle induces early initiation of classically conditioned postural responses

2012 ◽  
Vol 108 (11) ◽  
pp. 2946-2956 ◽  
Author(s):  
A. D. Campbell ◽  
R. Chua ◽  
J. T. Inglis ◽  
M. G. Carpenter
Keyword(s):  
Center Of Pressure ◽  
Motor Preparation ◽  
Support Surface ◽  
Conditioning Paradigm ◽  
Acoustic Stimuli ◽  
Postural Responses ◽  
Hip Kinematics ◽  
Surface Translation ◽  
Classically Conditioned ◽  
Insight Into

Startling acoustic stimuli (SAS) induce the early release of prepared motor responses. The current study used SAS, in conjunction with a classical conditioning paradigm, to examine advanced motor preparation of conditioned postural responses (PRs). After generalized startle responses were induced, standing posture was perturbed in 2 blocks of 15 Conditioning trials, where in each trial the onset of a nonstartling auditory cue [i.e., a conditioned stimulus (CS)] preceded a leftward support-surface translation. Upon completion of each block, a single trial was conducted. After block 1, a CS-Only trial was used to induce conditioned PRs in the absence of balance perturbations. After block 2, a post-Conditioning Startle trial that involved a CS subsequently followed by a SAS was used to examine motor preparation of conditioned PRs. PRs were quantified in terms of center of pressure displacements, ankle and hip kinematics, as well as surface electromyography of proximal and distal bilateral muscle pairs. Results indicated that repeated experience with cued balance perturbations led to PR conditioning and, more importantly, motor preparation of PRs. Conditioning was evidenced in biomechanical and electromyographic responses observed in CS-Only trials, as well as the progressive changes to evoked response parameters during repeated Conditioning trials. SAS presented in post-Conditioning Startle trials evoked early onsets of biomechanical and electromyographic responses, while preserving relative response parameters that were each distinct from generalized startle responses. These results provide important insight into both the consequences of using cues in dynamic postural control studies and the neural mechanisms governing PRs.

Organization of postural responses following a rotational support surface perturbation, after TKA: Sagittal plane rotations

2007 ◽  
Vol 25 (1) ◽  
pp. 112-120 ◽  
Author(s):  
William H. Gage ◽  
James S. Frank ◽  
Stephen D. Prentice ◽  
Peter Stevenson
Keyword(s):  
Sagittal Plane ◽  
Support Surface ◽  
Surface Perturbation ◽  
Postural Responses

Activity of neuromuscular compartments in lateral gastrocnemius evoked by postural corrections during stance

1993 ◽  
Vol 70 (6) ◽  
pp. 2337-2349 ◽  
Author(s):  
D. C. Dunbar ◽  
J. M. Macpherson
Keyword(s):  
Three Dimensional ◽  
Area Under The Curve ◽  
Gluteus Medius ◽  
Emg Activity ◽  
Support Surface ◽  
Lateral Gastrocnemius ◽  
Tuning Curves ◽  
Postural Responses ◽  
Upward Displacement ◽  
Neuromuscular Compartments

1. The electromyographic (EMG) activity of the four neuromuscular compartments in lateral gastrocnemius (LG) of cats was investigated to determine whether these intramuscular subdivisions could be activated differentially during automatic postural corrections. EMG electrodes were surgically implanted into each of the four compartments of left LG-LG1, LG2, LG3, and LGm--in two cats. Electrodes were also implanted into soleus and gluteus medius for comparative purposes. 2. Quiet quadrupedal stance was disturbed first by linearly translating the cats on a movable platform in each of 16 different horizontal directions. Mechanical events during corrections were characterized in terms of the three-dimensional forces exerted by each paw on the platform. EMG and force traces were quantified (area under the curve) and normalized, and tuning curves were constructed that relate muscle response and force change to direction of platform movement. 3. In a second series of trials, translations were presented along one direction only over a series of six velocities ranging from 5 to 16 cm/s. The third series of perturbations, termed the pop-up, consisted of a rapid upward displacement of the support under the left hindlimb only over a series of six amplitudes ranging from 1 to 10 mm. Evoked EMG activity and average change in force were normalized and regressions were computed onto velocity and amplitude, respectively. The slopes of the regressions were compared. 4. EMG tuning curves associated with the multidirectional horizontal translations revealed no differential activity across LG compartments. Similarly, there was no statistical difference among the slopes of the regressions within LG. In contrast, soleus exhibited significantly different slopes from LG for the regressions. Thus it is concluded that LG compartments are not differentially activated during automatic postural responses to perturbations of the support surface.

Interaction between acoustic startle and habituated neck postural responses in seated subjects

2007 ◽  
Vol 102 (4) ◽  
pp. 1574-1586 ◽  
Author(s):  
Jean-Sébastien Blouin ◽  
Gunter P. Siegmund ◽  
J. Timothy Inglis
Keyword(s):  
Startle Response ◽  
Acoustic Startle ◽  
Acoustic Startle Response ◽  
Neck Muscles ◽  
Whole Body ◽  
Neck Muscle ◽  
Postural Response ◽  
Root Mean Square Amplitude ◽  
Postural Responses ◽  
Spatial Changes

Postural and startle responses rapidly habituate with repeated exposures to the same stimulus, and the first exposure to a seated forward acceleration elicits a startle response in the neck muscles. Our goal was to examine how the acoustic startle response is integrated with the habituated neck postural response elicited by forward accelerations of seated subjects. In experiment 1, 14 subjects underwent 11 sequential forward accelerations followed by 5 additional sled accelerations combined with a startling tone (124-dB sound pressure level) initiated 18 ms after sled acceleration onset. During the acceleration-only trials, changes consistent with habituation occurred in the root-mean-square amplitude of the neck muscles and in the peak amplitude of five head and torso kinematic variables. The subsequent addition of the startling tone restored the amplitude of the neck muscles and four of the five kinematic variables but shortened onset of muscle activity by 9–12 ms. These shortened onset times were further explored in experiment 2, wherein 16 subjects underwent 11 acceleration-only trials followed by 15 combined acceleration-tone trials with interstimulus delays of 0, 13, 18, 23, and 28 ms. Onset times shortened further for the 0- and 13-ms delays but did not lengthen for the 23- and 28-ms delays. These temporal and spatial changes in EMG can be explained by a summation of the excitatory drive converging at or before the neck muscle motoneurons. The present observations suggest that habituation to repeated sled accelerations involves extinguishing the startle response and tuning the postural response to the whole body disturbance.

Postural responses to yaw rotation of support surface

2013 ◽  
Vol 37 (2) ◽  
pp. 296-299 ◽  
Author(s):  
Chiung-Ling Chen ◽  
Shu-Zon Lou ◽  
Hong-Wen Wu ◽  
Shyi-Kuen Wu ◽  
Kwok-Tak Yeung ◽  
...  
Keyword(s):  
Support Surface ◽  
Postural Responses

scholarly journals Responses to Loud Acoustic Stimuli: Short and Long Timescale Effects on Cortical and Sub-Cortical Preparation Reflect Conditional Probability

2020 ◽  
Author(s):  
An T. Nguyen ◽  
James R. Tresilian ◽  
Ottmar V. Lipp ◽  
Dayse Tavora-Vieira ◽  
Welber Marinovic
Keyword(s):  
Conditional Probability ◽  
Auditory Stimulus ◽  
Stimulus Intensity ◽  
Cortical Excitability ◽  
Movement Preparation ◽  
Movement Onset ◽  
Eeg Activity ◽  
Motor Responses ◽  
Acoustic Stimuli ◽  
Startreact Effect

AbstractLoud acoustic stimuli (LAS) can trigger prepared motor responses at very short latencies: the StartReact effect. In this study, we tested the proposal that responses to LAS in the StartReact effect could be explained by stimulus intensity effects combined with movement-related preparation changes on nervous system excitability. Using a simple auditory reaction time task, we induced different levels of preparation by systematically manipulating the conditional probability and temporal location of the auditory stimulus (LAS or non-intense tone). We then examined how preparation-levels influenced motor responses to LAS and non-intense tones, as well as cortical and sub-cortical excitability — reflected by electroencephalographic (EEG) activity before the onset of the auditory stimulus, and the eye-blink startle reflex.On both tone and LAS trials, higher preparation conditions were accompanied with reductions in movement onset time, increased force, as well as enhanced cortical (in auditory and motor areas) and sub-cortical excitability. At the trial-level, we found that enhanced pre-stimulus EEG activity in sensory and motor areas was associated with earlier movement onset on tone trials, and shorter blink onset latencies were associated with earlier movement onset on LAS trials. The results show that movement preparation is associated with wide-spread changes in cortical and sub-cortical excitability, and that movement preparation (combined with stimulus-intensity effects) plays a critical role in shaping responses to both non-intense tones and LAS.

scholarly journals Visual Modulation of Human Responses to Support Surface Translation

2021 ◽  
Vol 15 ◽  
Author(s):  
Mustafa Emre Akçay ◽  
Vittorio Lippi ◽  
Thomas Mergner
Keyword(s):  
Inverted Pendulum ◽  
Significant Degree ◽  
The Body ◽  
Resonance Phenomenon ◽  
Continuous Illumination ◽  
Support Surface ◽  
Position Information ◽  
Eyes Closed ◽  
Postural Responses ◽  
Visual Conditions

Vision is known to improve human postural responses to external perturbations. This study investigates the role of vision for the responses to continuous pseudorandom support surface translations in the body sagittal plane in three visual conditions: with the eyes closed (EC), in stroboscopic illumination (EO/SI; only visual position information) and with eyes open in continuous illumination (EO/CI; position and velocity information) with the room as static visual scene (or the interior of a moving cabin, in some of the trials). In the frequency spectrum of the translation stimulus we distinguished on the basis of the response patterns between a low-frequency, mid-frequency, and high-frequency range (LFR: 0.0165-0.14 Hz; MFR: 0.15–0.57 Hz; HFR: 0.58–2.46 Hz). With EC, subjects’ mean sway response gain was very low in the LFR. On average it increased with EO/SI (although not to a significant degree p = 0.078) and more so with EO/CI (p < 10−6). In contrast, the average gain in the MFR decreased from EC to EO/SI (although not to a significant degree, p = 0.548) and further to EO/CI (p = 0.0002). In the HFR, all three visual conditions produced, similarly, high gain levels. A single inverted pendulum (SIP) model controlling center of mass (COM) balancing about the ankle joints formally described the EC response as being strongly shaped by a resonance phenomenon arising primarily from the control’s proprioceptive feedback loop. The effect of adding visual information in these simulations lies in a reduction of the resonance, similar as in the experiments. Extending the model to a double inverted pendulum (DIP) suggested in addition a biomechanical damping effective from trunk sway in the hip joints on the resonance.

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