Matching Items (8)

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I Can’t Stand Thinking Anymore: An Analysis of Directed Attention on Posture

Description

Maintaining upright balance and postural control is a task that most individuals perform everyday with ease and without much thought. Although it may be a relatively easy task to

Maintaining upright balance and postural control is a task that most individuals perform everyday with ease and without much thought. Although it may be a relatively easy task to perform, research has shown that changes in cognitive (or “attentional”) processes are reflected in the movements of sway. The purpose of this dissertation is to understand the relationship between attention and posture when attention is directly or indirectly shifted away from posture. Using a dual-task paradigm, attention was shifted directly by instructing participants to prioritize the balance task (minimize sway in a unipedal stance) or prioritize the cognitive task (minimize errors in an auditory n-back task) and indirectly by changing the difficulty level of the cognitive task (0-back vs. 2-back task). Postural sway was assessed using sample entropy (SampEn), standard deviation, (SD) and sway path (SP) of trunk movements to measure the regularity, variability, and overall distance of sway travelled, respectively. Dual-task behavior was examined when participants were in a controlled (i.e., non-fatigued) state (Experiment 1), in a state of physical fatigue (Experiment 2), and in a state of mental fatigue (Experiment 3). Across all three experiments, indirectly shifting attention away from posture in the more difficult 2-back task induced less regularity (higher SampEn) and variability (smaller SD) in postural sway. Directly shifting attention away from posture, by prioritizing the cognitive task, induced less regularity (higher SampEn) and a longer path length (higher SP) in Experiment 1, however this effect was not significant for the fatigued participants in Experiments 2 and 3. Neither physical fatigue (Experiment 2) or mental fatigue (Experiment 3) negatively affected postural sway or cognitive performance. Overall, the findings from this dissertation contribute to the relationship between movement regularity and attention in posture, and that the postural behavior that emerges is sensitive to methods in which attention is manipulated (direct, indirect) and fatigue (physical, mental).

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Created

Date Created
  • 2019

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Psychophysical and neural correlates of auditory attraction and aversion

Description

This study explores the psychophysical and neural processes associated with the perception of sounds as either pleasant or aversive. The underlying psychophysical theory is based on auditory scene analysis, the

This study explores the psychophysical and neural processes associated with the perception of sounds as either pleasant or aversive. The underlying psychophysical theory is based on auditory scene analysis, the process through which listeners parse auditory signals into individual acoustic sources. The first experiment tests and confirms that a self-rated pleasantness continuum reliably exists for 20 various stimuli (r = .48). In addition, the pleasantness continuum correlated with the physical acoustic characteristics of consonance/dissonance (r = .78), which can facilitate auditory parsing processes. The second experiment uses an fMRI block design to test blood oxygen level dependent (BOLD) changes elicited by a subset of 5 exemplar stimuli chosen from Experiment 1 that are evenly distributed over the pleasantness continuum. Specifically, it tests and confirms that the pleasantness continuum produces systematic changes in brain activity for unpleasant acoustic stimuli beyond what occurs with pleasant auditory stimuli. Results revealed that the combination of two positively and two negatively valenced experimental sounds compared to one neutral baseline control elicited BOLD increases in the primary auditory cortex, specifically the bilateral superior temporal gyrus, and left dorsomedial prefrontal cortex; the latter being consistent with a frontal decision-making process common in identification tasks. The negatively-valenced stimuli yielded additional BOLD increases in the left insula, which typically indicates processing of visceral emotions. The positively-valenced stimuli did not yield any significant BOLD activation, consistent with consonant, harmonic stimuli being the prototypical acoustic pattern of auditory objects that is optimal for auditory scene analysis. Both the psychophysical findings of Experiment 1 and the neural processing findings of Experiment 2 support that consonance is an important dimension of sound that is processed in a manner that aids auditory parsing and functional representation of acoustic objects and was found to be a principal feature of pleasing auditory stimuli.

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Agent

Created

Date Created
  • 2014

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Movement kinematics and fractal properties in Fitts' law task

Description

Fractal analyses examine variability in a time series to look for temporal structure

or pattern that reveals the underlying processes of a complex system. Although fractal

property has been found in many

Fractal analyses examine variability in a time series to look for temporal structure

or pattern that reveals the underlying processes of a complex system. Although fractal

property has been found in many signals in biological systems, how it relates to

behavioral performance and what it implies about the complex system under scrutiny are

still open questions. In this series of experiments, fractal property, movement kinematics,

and behavioral performance were measured on participants performing a reciprocal

tapping task. In Experiment 1, the results indicated that the alpha value from detrended

fluctuation analysis (DFA) reflected deteriorating performance when visual feedback

delay was introduced into the reciprocal tapping task. This finding suggests that this

fractal index is sensitive to performance level in a movement task. In Experiment 2, the

sensitivity of DFA alpha to the coupling strength between sub-processes within a system

was examined by manipulation of task space visibility. The results showed that DFA

alpha was not influenced by disruption of subsystems coupling strength. In Experiment 3,

the sensitivity of DFA alpha to the level of adaptivity in a system under constraints was

examined. Manipulation of the level of adaptivity was not successful, leading to

inconclusive results to this question.

Contributors

Agent

Created

Date Created
  • 2019

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Heaviness perception dynamics in the leg and arm

Description

Perceived heaviness of lifted objects has been shown to scale to a ratio of muscle activity and movement during elbow lifts. This scaling reflects the importance of the forces

Perceived heaviness of lifted objects has been shown to scale to a ratio of muscle activity and movement during elbow lifts. This scaling reflects the importance of the forces applied to an object and the resulting kinematics for this perception. The current study determined whether these perceived heaviness dynamics are similar in other lifting conditions. Anatomically sourced context-conditioned variability has implications for motor control. The current study investigated whether these implications also hold for heaviness perception. In two experiments participants lifted objects with knee extension lifts and with several arm lifts and reported perceived heaviness. The resulting psychophysiological functions revealed the hypothesized muscle activity and movement ratio in both leg and arms lifts. Further, principal component regressions showed that the forearm flexors and corresponding joint angular accelerations were most relevant for perceived heaviness during arm lifts. Perceived heaviness dynamics are similar in the arms and legs.

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Agent

Created

Date Created
  • 2016

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Multiscale interactions in psychological systems

Description

For many years now, researchers have documented evidence of fractal scaling in psychological time series. Explanations of fractal scaling have come from many sources but those that have gained

For many years now, researchers have documented evidence of fractal scaling in psychological time series. Explanations of fractal scaling have come from many sources but those that have gained the most traction in the literature are theories that suggest fractal scaling originates from the interactions among the multiple scales that make up behavior. Those theories, originating in the study of dynamical systems, suffer from the limitation that fractal analysis reveals only indirect evidence of multiscale interactions. Multiscale interactions must be demonstrated directly because there are many means to generate fractal properties. In two experiments, participants performed a pursuit tracking task while I recorded multiple behavioral and physiological time series. A new analytical technique, multiscale lagged regression, was introduced to capture how those many psychological time series coordinate across multiple scales and time. The results were surprising in that coordination among psychological time series tends to be oscillatory in nature, even when the series are not oscillatory themselves. Those and other results demonstrate the existence of multiscale interactions in psychological systems.

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Created

Date Created
  • 2016

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Relative phase dynamics in motor-respiratory coordination

Description

Motor-respiratory coordination is the synchronization of movement and breathing during exercise. The relation between movement and breathing can be described using relative phase, a measure of the location in the

Motor-respiratory coordination is the synchronization of movement and breathing during exercise. The relation between movement and breathing can be described using relative phase, a measure of the location in the movement cycle relative to the location in the breathing cycle. Stability in that relative phase relation has been identified as important for aerobic efficiency. However, performance can be overly attracted to stable relative phases, preventing the performance or learning of more complex patterns. Little research exists on relative phase dynamics in motor-respiratory coordination, although those observations underscore the importance of learning more. In contrast, there is an extensive literature on relative phase dynamics in interlimb coordination. The accuracy and stability of different relative phases, transitions between patterns, and asymmetries between components are well understood. Theoretically, motor-respiratory and interlimb coordination may share dynamical properties that operate in their different physiological substrates. An existing model of relative phase dynamics in interlimb coordination, the Haken, Kelso, Bunz model, was used to gain an understanding of relative phase dynamics in the less-researched motor-respiratory coordination. Experiments 1 and 2 were designed to examine the interaction of frequency asymmetries between movement and breathing with relative phase and frequency, respectively. In Experiment 3, relative phase stability and transitions in motor-respiratory coordination were explored. Perceptual constraints on differences in stability were investigated in Experiment 4. Across experiments, contributions relevant to questions of coordinative variability were made using a dynamical method called cross recurrence quantification analysis. Results showed much consistency with predictions from an asymmetric extension of the Haken, Kelso, Bunz model and theoretical interpretation in the interlimb coordination literature, including phase wandering, intermittency, and an interdependence of perception and action. There were, however, notable exceptions that indicated stability can decrease with more natural frequency asymmetries and the connection of cross recurrence measures to categories of variability needs further clarification. The complex relative phase dynamics displayed in this study suggest that movement and breathing are softly-assembled by functional constraints and indicate that motor-respiratory coordination is a self-organized system.

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Agent

Created

Date Created
  • 2010

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Asymmetries in interpersonal coordination: recruiting degrees-of-freedom stabilizes coordination

Description

The current paper presents two studies that examine how asymmetries during interpersonal coordination are compensated for. It was predicted that destabilizing effects of asymmetries are stabilized through the recruitment and

The current paper presents two studies that examine how asymmetries during interpersonal coordination are compensated for. It was predicted that destabilizing effects of asymmetries are stabilized through the recruitment and suppression of motor degrees-of-freedom (df). Experiment 1 examined this effect by having participants coordinate line movements of different orientations. Greater differences in asymmetries between participants yielded greater spatial deviation, resulting in the recruitment of df. Experiment 2 examined whether coordination of movements asymmetrical in shape (circle and line) yield simultaneous recruitment and suppression of df. This experiment also tested whether the initial stability of the performed movement alters the amount of change in df. Results showed that changes in df were exhibited as circles decreasing in circularity and lines increasing in circularity. Further, more changes in df were found circular (suppression) compared to line (recruitment) movements.

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Created

Date Created
  • 2013

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Natural Correlations of Spectral Envelope and their Contribution to Auditory Scene Analysis

Description

Auditory scene analysis (ASA) is the process through which listeners parse and organize their acoustic environment into relevant auditory objects. ASA functions by exploiting natural regularities in the structure of

Auditory scene analysis (ASA) is the process through which listeners parse and organize their acoustic environment into relevant auditory objects. ASA functions by exploiting natural regularities in the structure of auditory information. The current study investigates spectral envelope and its contribution to the perception of changes in pitch and loudness. Experiment 1 constructs a perceptual continuum of twelve f0- and intensity-matched vowel phonemes (i.e. a pure timbre manipulation) and reveals spectral envelope as a primary organizational dimension. The extremes of this dimension are i (as in “bee”) and Ʌ (“bun”). Experiment 2 measures the strength of the relationship between produced f0 and the previously observed phonetic-pitch continuum at three different levels of phonemic constraint. Scat performances and, to a lesser extent, recorded interviews were found to exhibit changes in accordance with the natural regularity; specifically, f0 changes were correlated with the phoneme pitch-height continuum. The more constrained case of lyrical singing did not exhibit the natural regularity. Experiment 3 investigates participant ratings of pitch and loudness as stimuli vary in f0, intensity, and the phonetic-pitch continuum. Psychophysical functions derived from the results reveal that moving from i to Ʌ is equivalent to a .38 semitone decrease in f0 and a .75 dB decrease in intensity. Experiment 4 examines the potentially functional aspect of the pitch, loudness, and spectral envelope relationship. Detection thresholds of stimuli in which all three dimensions change congruently (f0 increase, intensity increase, Ʌ to i) or incongruently (no f0 change, intensity increase, i to Ʌ) are compared using an objective version of the method of limits. Congruent changes did not provide a detection benefit over incongruent changes; however, when the contribution of phoneme change was removed, congruent changes did offer a slight detection benefit, as in previous research. While this relationship does not offer a detection benefit at threshold, there is a natural regularity for humans to produce phonemes at higher f0s according to their relative position on the pitch height continuum. Likewise, humans have a bias to detect pitch and loudness changes in phoneme sweeps in accordance with the natural regularity.

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Created

Date Created
  • 2017