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.

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.

scholarly journals Stabilometric Correlates of Motor and Motor Imagery Expertise

2022 ◽  
Vol 15 ◽  
Author(s):  
Franck Di Rienzo ◽  
Pierric Joassy ◽  
Thiago Ferreira Dias Kanthack ◽  
François Moncel ◽  
Quentin Mercier ◽  
...  
Keyword(s):  
Motor Imagery ◽  
Center Of Pressure ◽  
Balance Control ◽  
Motor Preparation ◽  
Visual Modality ◽  
Training Experience ◽  
Motor Expertise ◽  
Postural Responses ◽  
Expertise Level ◽  
Balance Skill

Motor Imagery (MI) reproduces cognitive operations associated with the actual motor preparation and execution. Postural recordings during MI reflect somatic motor commands targeting peripheral effectors involved in balance control. However, how these relate to the actual motor expertise and may vary along with the MI modality remains debated. In the present experiment, two groups of expert and non-expert gymnasts underwent stabilometric assessments while performing physically and mentally a balance skill. We implemented psychometric measures of MI ability, while stabilometric variables were calculated from the center of pressure (COP) oscillations. Psychometric evaluations revealed greater MI ability in experts, specifically for the visual modality. Experts exhibited reduced surface COP oscillations in the antero-posterior axis compared to non-experts during the balance skill (14.90%, 95% CI 34.48–4.68, p < 0.05). Experts further exhibited reduced length of COP displacement in the antero-posterior axis and as a function of the displacement area during visual and kinesthetic MI compared to the control condition (20.51%, 95% CI 0.99–40.03 and 21.85%, 95% CI 2.33–41.37, respectively, both p < 0.05). Predictive relationships were found between the stabilometric correlates of visual MI and physical practice of the balance skill, as well as between the stabilometric correlates of kinesthetic MI and the training experience in experts. Present results provide original stabilometric insights into the relationships between MI and expertise level. While data support the incomplete inhibition of postural commands during MI, whether postural responses during MI of various modalities mirror the level of motor expertise remains unclear.

scholarly journals Postural responses exhibit multisensory dependencies with discordant visual and support surface motion

2004 ◽  
Vol 14 (4) ◽  
pp. 307-319 ◽  
Author(s):  
Emily A. Keshner ◽  
Robert V. Kenyon ◽  
Jessica Langston
Keyword(s):  
Support Surface ◽  
Wide Field ◽  
Stimulus Amplitude ◽  
Visual Inputs ◽  
Postural Responses ◽  
Wide Field Of View ◽  
Postural System ◽  
Surface Translation ◽  
Anterior Posterior

The purpose of this study was to identify how the postural system weights coincident yet discordant disturbances of the visual and proprioceptive/vestibular systems. Eleven healthy subjects (25–38 yrs) received either fore-aft translations of an immersive, wide field-of-view visual environment (0.1 Hz, ± 3.7 m/sec), or anterior-posterior translations of the support surface (0.25 Hz, ± 15 cm/sec), or both concurrently. Kinematics of the head, trunk, and shank were collected with an Optotrak system and angular motion of each segment plotted across time. With only support surface translation, segmental responses were small (1°–2°) and mostly opposed the direction of sled translation. When only the visual scene was moving, segmental responses increased as the trial progressed. When the inputs were presented coincidentally, response amplitudes were large even at the onset of the trial. Mean RMS values across subjects were significantly greater with combined stimuli than for either stimulus presented alone and areas under the power curve across subjects were significantly increased at the frequency of the visual input when both inputs were presented. Thus, intra-modality dependencies were observed, such that responses to the visual inputs significantly increased and responses to the somatosensory signals reflected the stimulus amplitude only when the two inputs were combined. We believe it unlikely that the role of any single pathway contributing to postural control can be accurately characterized in a static environment if the function of that pathway is context dependent.

scholarly journals Age-Related Changes in Human Posture Control: Motor Coordination Tests

1990 ◽  
Vol 1 (1) ◽  
pp. 87-96 ◽  
Author(s):  
R.J. Peterka ◽  
F.O. Black
Keyword(s):  
Motor Coordination ◽  
Center Of Pressure ◽  
Human Subjects ◽  
Body Sway ◽  
Support Surface ◽  
Age Related ◽  
Postural Responses ◽  
Surface Displacements ◽  
Normal Human ◽  
Motor Tests

Postural responses to support surface displacements were measured in 214 normal human subjects ranging in age from 7 to 81 y. Motor tests measured leg muscle electromyographic (EMG) latencies, body sway, and the amplitude and timing of changes in center of pressure displacements in response to sudden forward and backward horizontal translations of the support surface upon which the subjects stood. There were small increases in both EMG latencies and the time to reach the peak amplitude of center of pressure responses with increasing age. The amplitude of center of pressure responses showed no change with age if the amplitude measures were normalized by a factor related to subject height. In general, postoral responses to sudden translations showed minimal changes with age, and all age-related trends that were identified were small relative to the variability within the population.

Effects of Maintaining Touch Contact on Predictive and Reactive Balance

2007 ◽  
Vol 97 (4) ◽  
pp. 2686-2695 ◽  
Author(s):  
Leif Johannsen ◽  
Alan M. Wing ◽  
Vassilia Hatzitaki
Keyword(s):  
Time Course ◽  
Center Of Pressure ◽  
The Body ◽  
Contact Forces ◽  
Quiet Standing ◽  
Support Surface ◽  
Light Touch ◽  
Postural Control System ◽  
Postural Responses ◽  
Body Self

Light touch contact between the body and an environmental referent reduces fluctuations of center of pressure (CoP) in quiet standing although the contact forces are insufficient to provide significant forces to stabilize standing balance. Maintenance of upright standing posture (with light touch contact) may include both predictive and reactive components. Recently Dickstein et al. (2003) demonstrated that reaction to temporally unpredictable displacement of the support surface was affected by light touch raising the question whether light touch effects also occur with predictable disturbance to balance. We examined the effects of shoulder light touch on SD of CoP rate (dCoP) during balance perturbations associated with forward sway induced by pulling on (voluntary), or being pulled by (reactive), a hand-held horizontal load. Prior to perturbation, SD dCoP was lower with light touch, corresponding to previous findings. Immediately after perturbation, SD dCoPAP was greater with light touch in the case of voluntary pull, whereas no difference was found for reflex pull. However, in the following time course, light touch contact again resulted in a significantly lower SD dCoP and faster stabilization of SD dCoP. We conclude that shoulder light touch contact affects immediate postural responses to voluntary pull but also stabilization after voluntary and reflex perturbation. We suggest that in voluntary perturbation CoP fluctuations are differentially modulated in anterioposterior and mediolateral directions to maintain light touch, which not only provides augmented sensory feedback about body self-motion, but may act as a “constraint” to the postural control system when preparing postural adjustments.

Alteration of Postural Responses Due to Chronic Recurrent Low Back Pain

2004 ◽  
Author(s):  
Sharon M. Henry ◽  
Juvena R. Hitt ◽  
Stephanie L. Jones ◽  
Janice Y. Bunn
Keyword(s):  
Low Back Pain ◽  
Back Pain ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Force Plate ◽  
Support Surface ◽  
Low Back ◽  
Joint Torques ◽  
Postural Responses ◽  
Recurrent Low Back Pain

This study characterized postural responses in subjects with (n=26, 39 ± 13 yrs) and without (n=24, 32 ± 10 yrs) chronic ( >6 months), recurrent low back pain (LBP) in response to support surface translations, randomly delivered in 12 different horizontal directions. Using kinematic, force plate and anthropometric data, the net center of pressure (CP), total body center of mass (CM), and net joint torques (sagittal and frontal planes) at the ankle, knee, hip and trunk were examined to characterize the neuromuscular responses in the two subject groups. LBP subjects exhibited larger anterior and posterior CM displacements compared to NLBP (p = 0.0267) and smaller anterior and posterior CP displacements (p <0.0001). Overall, torque responses in persons with LBP were smaller, delayed and developed more quickly compared to NLBP subjects and the responses were non-directionally specific. These data suggest the automatic postural control of subjects with LBP is altered such that there is an overall stiffening strategy for LBP subjects, which is reflected in the reduced CP displacement and the smaller and delayed torque responses.

scholarly journals Mechanical effort predicts the selection of ankle over hip strategies in nonstepping postural responses

2016 ◽  
Vol 116 (4) ◽  
pp. 1937-1945 ◽  
Author(s):  
Maarten Afschrift ◽  
Ilse Jonkers ◽  
Joris De Schutter ◽  
Friedl De Groote
Keyword(s):  
Muscle Activity ◽  
Postural Instability ◽  
Mechanical Work ◽  
Support Surface ◽  
Upright Posture ◽  
Relative Importance ◽  
Postural Response ◽  
Postural Responses ◽  
Surface Translation ◽  
Selection Of

Experimental studies have shown that a continuum of ankle and hip strategies is used to restore posture following an external perturbation. Postural responses can be modeled by feedback control with feedback gains that optimize a specific objective. On the one hand, feedback gains that minimize effort have been used to predict muscle activity during perturbed standing. On the other hand, hip and ankle strategies have been predicted by minimizing postural instability and deviation from upright posture. It remains unclear, however, whether and how effort minimization influences the selection of a specific postural response. We hypothesize that the relative importance of minimizing mechanical work vs. postural instability influences the strategy used to restore upright posture. This hypothesis was investigated based on experiments and predictive simulations of the postural response following a backward support surface translation. Peak hip flexion angle was significantly correlated with three experimentally determined measures of effort, i.e., mechanical work, mean muscle activity and metabolic energy. Furthermore, a continuum of ankle and hip strategies was predicted in simulation when changing the relative importance of minimizing mechanical work and postural instability, with increased weighting of mechanical work resulting in an ankle strategy. In conclusion, the combination of experimental measurements and predictive simulations of the postural response to a backward support surface translation showed that the trade-off between effort and postural instability minimization can explain the selection of a specific postural response in the continuum of potential ankle and hip strategies.

scholarly journals Do Aging and Tactile Noise Stimulation Affect Responses to Support Surface Translations in Healthy Adults?

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Marius Dettmer ◽  
Amir Pourmoghaddam ◽  
Beom-Chan Lee ◽  
Charles S. Layne
Keyword(s):  
Older Adults ◽  
Healthy Aging ◽  
Mixed Model ◽  
Center Of Pressure ◽  
Support Surface ◽  
Older Individuals ◽  
Postural Response ◽  
Postural Perturbation ◽  
Low Level ◽  
Postural Responses

Appropriate neuromuscular responses to support surface perturbations are crucial to prevent falls, but aging-related anatomical and physiological changes affect the appropriateness and efficiency of such responses. Low-level noise application to sensory receptors has shown to be effective for postural improvement in a variety of different balance tasks, but it is unknown whether this intervention may have value for improvement of corrective postural responses. Ten healthy younger and ten healthy older adults were exposed to sudden backward translations of the support surface. Low-level noise (mechanical vibration) to the foot soles was added during random trials and temporal (response latency) and spatial characteristics (maximum center-of-pressure excursion and anterior-posterior path length) of postural responses were assessed. Mixed-model ANOVA was applied for analysis of postural response differences based on age and vibration condition. Age affected postural response characteristics, but older adults were well able to maintain balance when exposed to a postural perturbation. Low-level noise application did not affect any postural outcomes. Healthy aging affects some specific measures of postural stability, and in high-functioning older individuals, a low-level noise intervention may not be valuable. More research is needed to investigate if recurring fallers and neuropathy patients could benefit from the intervention in postural perturbation tasks.

scholarly journals Postural Responses to Sudden Horizontal Perturbations in Tai Chi Practitioners

2021 ◽  
Vol 18 (5) ◽  
pp. 2692
Author(s):  
Jernej Sever ◽  
Jan Babič ◽  
Žiga Kozinc ◽  
Nejc Šarabon
Keyword(s):  
Tai Chi ◽  
Center Of Pressure ◽  
Well Being ◽  
Vertical Movement ◽  
Control Group ◽  
Age Difference ◽  
Positive Effects ◽  
Postural Responses ◽  
Force Increase ◽  
Load Release

Tai Chi has been shown to elicit numerous positive effects on health and well-being. In this study, we examined reactive postural control after sudden unloading horizontal perturbations, which resembled situations encountered during Tai Chi. The study involved 20 participants, 10 in the Tai Chi group (age: 37.4 ± 7.8 years), who had been regularly training the push-hand technique for at least 7 years, and 10 in the control group, consisting of healthy adults (age: 28.8 ± 5.0). Perturbations were applied at three different positions (hips, shoulders, and arms) via the load-release paradigm. Twenty measurements were carried out for each perturbation position. We measured peak vertical and horizontal forces on the ground (expressed percentage of body mass (%BM)), peak center of pressure displacement and peak horizontal and vertical velocities at the knee, hip and shoulder joints. The Tai Chi group exhibited smaller increases in vertical ground reaction forces when perturbations were applied at the hips (11.5 ± 2.1 vs. 19.6 ± 5.5 %BW; p = 0.002) and the arms (14.1 ± 4.2 vs. 23.2 ± 8.4 %BW; p = 0.005). They also responded with higher horizontal force increase after hip perturbation (16.2 ± 3.2 vs. 13.1 ± 2.5 %BW; p < 0.001). Similar findings were found when observing various outcomes related to velocities of vertical movement. The Tai Chi group also showed lower speeds of backward movement of the knee (p = 0.005–0.009) after hip (0.49 ± 0.13 vs. 0.85 ± 0.14 m/s; p = 0.005) and arm perturbations (0.97 ± 0.18 vs. 1.71 ± 0.29 m/s; p = 0.005). Center of pressure displacements were similar between groups. Our study demonstrated that engaging in Tai Chi could be beneficial to reactive postural responses after sudden perturbations in a horizontal direction; however, future interventional studies are needed to directly confirm this. Moreover, because of the age difference between the groups, some confounding effects of age cannot be ruled out.

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