S. Lee Hong

Information Control Company

Parkinson’s disease (PD) is characterized as a chronic and progressive neurodegenerative disorder that results in a variety of debilitating symptoms, including bradykinesia, resting tremor, rigidity, and postural instability. Research spanning several decades has emphasized basal ganglia dysfunction, predominantly resulting from dopaminergic cell l...

Decline in neural, cognitive, sensori-motor and muscular functioning are generally considered as separate domains in aging research. This situation makes the aging literature a puzzle of individual pieces of knowledge in various subfields that requires an integrative view of aging in the neuro-musculo-skeletal system (NMSS). Growing evidence demons...

The goal of this study was to test whether the “loss of the complexity” hypothesis can be applied to compare the metabolic patterns of mouse models with known differences in metabolic and endocrine function as well as life span. Here, we compare the complexity of locomotor activity and metabolic patterns (energy expenditure, VO2, and respiratory qu...

Almost unequivocally, aging and neurodegeneration lead to deficits in neural information processing. These declines are marked by increased neural noise that is associated with increased variability or inconsistency in behavioral patterns. While it is often viewed that these problems arise from dysregulation of dopamine (DA), a monoamine modulator,...

Random number generators (RNGs) are the foundation of strong security and privacy measures. With an increasing number of smart devices being connected to the Internet, the demand for secure communication will only increase. An important outgrowth of Internet-connected devices is the embedding of sensors. Yet, there remains a paucity of good protoco...

Background Active video games (AVGs) capable of inducing physical activity offer an innovative approach to combating childhood obesity. Unfortunately, children’s AVG game play decreases quickly, underscoring the need to identify novel methods for player engagement. Narratives have been demonstrated to influence behaviors. Objective The objective o...

Medical physiology is generally studied as a static and complicated system where dynamic processes are captured as flow charts. From this perspective, when “X” increases, “Y” decreases, captured as feedback loops and cascades, or, after “A” happens, then “B” takes place. Such a static and sequential view on human physiology lends itself well to the...

Weakness predisposes seniors to a fourfold increase in functional limitations. The potential for age-related degradation in nervous system function to contribute to weakness and physical disability has garnered much interest of late. In this study, we tested the hypothesis that weaker seniors have impairments in voluntary (neural) activation and in...

We evaluated kinematics of people with Parkinson's disease (PD) and age-matched controls during cued and uncued reaching movements. Maximum hand velocity, its variability and shoulder-to-shoulder coupling, quantified by phase locking value (PLV), were compared between PD (n=14) and Control (n=4). The PD group achieved significantly lower maximum ha...

Growing evidence demonstrates that aging not only leads to structural and functional alterations of individual components of the neuro-musculo-skeletal system (NMSS) but also results in a systemic re-organization of interactions within and between the different levels and functional domains. Understanding the principles that drive the dynamics of t...

Responses are quicker to predictable stimuli than if the time and place of appearance is uncertain. Studies that manipulate target predictability often involve overt cues to speed up response times. However, less is known about whether individuals will exhibit faster response times when target predictability is embedded within the inter-trial relat...

http://journal.frontiersin.org/Journal/10.3389/fnagi.2014.00140/abstract

Too often overlooked, normal motor function is one of the most critical components of the human existence. The ability to move rests at the core of quality of life, due to the freedom that independent mobility offers. Despite its central role in everyday life, motor function is sometimes viewed as independent from and subsidiary to cognitive functi...

SK is an 84-year-old woman diagnosed with essential tremor (ET) but no cognitive deficits. In this experiment, we tested the effects of mental rotation (a form of additional cognitive load) during reaching behavior (with the right hand) on the tremor profile of the non-moving left hand. We observed a marked increase in tremor and its variability, a...

The symposium presented a multi-dimensional approach to cognitive-motor interplay. In Temprado & Hong presentation, merits of the dynamical systems and complexity approaches were more particularly emphasized.

Age-related muscle weakness causes a staggering economic, public, and personal burden. Most research has focused on internal muscular mechanisms as the root cause to strength loss. Here, we briefly discuss age-related impairments in the brain and peripheral nerve structures that may theoretically lead to muscle weakness in old age. Neuronal atrophy...

In Huntington's disease (HD), motor symptoms develop prior to the widespread loss of neurons in striatum and cerebral cortex. The aim of this study was to examine dysfunctional patterns of corticostriatal communication during spontaneously occurring behaviors in a transgenic mouse model of HD. Local field potentials (LFPs) were recorded from two cl...

This paper seeks to present a new perspective on the aging brain. Here, we make connections between two key phenomena of brain aging: (1) increased neural noise or random background activity; and (2) slowing of brain activity. Our perspective proposes the possibility that the slowing of neural processing due to decreasing nerve conduction velocitie...

Motor dysfunction is a consistently reported but understudied aspect of schizophrenia. Postural sway area was examined in individuals with schizophrenia under four conditions with different amounts of visual and proprioceptive feedback: eyes open or closed and feet together or shoulder width apart. The nonlinear complexity of postural sway was asse...

DFA-AP eyes X group interaction (singly versus dually diagnosed schizophrenia participants) post-hoc pair-wise comparisons. (DOC)

DFA-AP eyes X base interaction post-hoc pair-wise comparisons. (DOC)

DFA-AP eyes X base interaction (exclusion for past alcohol dependence) post-hoc pair-wise comparisons. (DOC)

Sway area eyes X group interaction post-hoc pair-wise comparisons. (DOC)

DFA-AP eyes X group interaction (exclusion for past alcohol dependence) post-hoc pair-wise comparisons. (DOC)

This paper expands on recent findings that link dynamic patterns of striatal activity with patterns of movement and exploration in wild-type and transgenic mice (R6/2) that model Huntington disease (HD), a fatally inherited neurological condition. Here, with HD as a backdrop, we further develop the concept of entropy conservation in brain and behav...

Various studies have suggested that postural sway is controlled by at least two subsystems. Rambling-Trembling analysis is a widely accepted methodology to dissociate the signals generated by these two hypothetical subsystems. The core assumption of this method is based on the equilibrium point hypothesis which suggests that the central nervous sys...

Huntington's disease (HD) is an inherited condition that results in neurodegeneration of the striatum, the forebrain structure that processes cortical information for behavioral output. In the R6/2 transgenic mouse model of HD, striatal neurons exhibit aberrant firing patterns that are coupled with reduced flexibility in the motor system. The aim o...

This study was designed to investigate the effects of increasing movement frequency of a single limb on the degree of similarity and coherence of the motor outflow in the non-active limb. Twelve young adults performed a series of unilateral hand-clapping tasks (horizontal and vertical in 25-s trials) while seated. Individuals began the movements at...

Constricted affect (CA) is a cardinal negative symptom of schizophrenia-spectrum disorders. It is unclear whether behaviorally-defined CA occurs in individuals with schizotypy-those with the personality organization reflective of schizophrenia liability. Moreover, it is unclear whether CA contributes to real world dysfunction in this population. Th...

Structural, neurochemical, and functional abnormalities have been identified in the brains of individuals with bipolar disorder, including in key brain structures implicated in postural control, i.e. the cerebellum, brainstem, and basal ganglia. Given these findings, we tested the hypothesis that postural control deficits are present in individuals...

Over the last two decades, various measures of entropy have been used to examine the complexity of human postural control. In general, entropy measures provide information regarding the health, stability and adaptability of the postural system that is not captured when using more traditional analytical techniques. The purpose of this study was to e...

Theoretical and empirical evidence suggests that impaired time perception and the neural circuitry contributing to internal timing mechanisms may contribute to severe psychiatric disorders, including mood disorders. The structures that are involved in subsecond timing, i.e., cerebellum and basal ganglia, have also been implicated in the pathophysio...

In many H-reflex studies, the modulation of the H-reflex is usually compared relative to the normal EMG activity within the muscle. Such comparisons enable the investigators to infer whether the change in the amplitude of the H-reflex was independent of normally occurring muscle activity. This interpretation of the H-reflex is regarded as H-reflex...

Uncertainty and predictability have remained at the center of the study of human attention. Yet, studies have only examined whether response times (RT) or fixations were longer or shorter under levels of stimulus uncertainty. To date, no study has examined patterns of stimuli and responses through a unifying framework of uncertainty. We asked 29 co...

The entropy conservation framework describes the task-organism-environment system as a system where entropy remains a conserved quantity that is redistributed for the purposes of motor adaptation. In this paper, potential applications for the entropy conservation framework in the areas of ergonomics and human factors are presented. First, a brief o...

Emotional expression is an essential function for daily life that can be severely affected in some psychological disorders. Laboratory-based procedures designed to measure prosodic expression from natural speech have shown early promise for measuring individual differences in emotional expression but have yet to produce robust within-group prosodic...

This study examined the hypothesis that the stability of rhythmic motor patterns increases with developmental age in children. Children aged 6 and 10 years and adults (18- to 23-year-olds) rocked back and forth at their preferred amplitude and frequency while seated on a wooden box placed atop a force platform. Participants performed the seated roc...

A multiple time scales landscape model is presented that reveals structures of performance dynamics that were not resolved in the traditional power law analysis of motor learning. It shows the co-existence of separate processes during and between practice sessions that evolve in two independent dimensions characterized by time scales that differ by...

This study examined what changes occur in upper-limb bilateral coordination during clapping as the movement frequency requirements were increased to the maximum. Subjects were required to begin the clapping action at approximately 1Hz and gradually increase the movement speed until their maximal frequency was achieved. Hand and finger displacement...

Despite dramatic advances in the sophistication of tools for measuring prosodic and content channels of expression from natural speech, methodological issues have limited the simultaneous measurement of those channels for laboratory research. This is particularly unfortunate, considering the importance of emotional expression in daily living and ho...

This experiment tested the hypothesis that human motor adaptation can be represented as the conservation of entropy across the task, organism, and environment. Healthy young individuals generated a submaximal isometric force with the index finger of their dominant hand. Subjects performed this task under different task demands (error tolerance) and...

Visual information is essential in human motor control, and especially in the continuous modulation of isometric force. The gain of visual feedback, that is, the amount of space used to represent change in force, has been shown to affect both the magnitude and time-dependent properties of variability in the force output. However, little is known re...

This study tested the hypothesis that postural complexity increases as the coupling across the axes of motion decreases as children get older. Children aged 6 and 10 years and young adults (18-23 years) were seated on a wooden box placed atop a force platform that recorded their mediolateral and anteroposterior center of pressure (COP) motion with...

The human motor system is highly adaptable with the ability to adjust its movement patterns under constantly changing task and environmental constraints. In this paper we develop the position that the probabilistic nature of human action can be characterized by entropies at the level of the organism, task, and environment. Systematic changes in mot...

This experiment examined the changes in entropy of the coordination of isometric force output under different levels of task demands and feedback from the environment. The goal of the study was to examine the hypothesis that human motor adaptation can be characterized as a process of entropy conservation that is reflected in the compensation of ent...

This experiment examined the hypothesis that aging reduces the coupling between system components, resulting in a loss of complexity in behavior. Young (18-23 years), old (60-65 years), and older old (70-75 years) subjects performed rhythmical movement and postural tasks with the index finger. Irregularity of the acceleration dynamics was lower dur...

This experiment investigated the effects of spatial (gain) and temporal (frequency) properties of visual feedback on the control of isometric force output. Participants performed an index finger isometric force production task with five different levels of visual gain and four feedback frequencies. There was a significant effect of gain on mean and...

The authors investigated the time scales of the learning of a mirror-tracing task to reexamine G. S. Snoddy's (1926) original claim and the received theoretical view (A. Newell & P. S. Rosenbloom, 1981) that motor learning follows a power law. Adult participants (N = 16) learned the tracing task in either a normal or a reversed visual-image conditi...

This study examined the effects of ice-induced plantar desensitization and the withdrawal of visual feedback on the magnitude and time-dependent structure of postural sway variability. The magnitude of variability was quantified as the area of an ellipse enclosing 95% of the center of pressure (COP) time-series during normal and tandem stances. The...

The aim of this study was to investigate the postural center of pressure (COP) and surface muscle (EMG) dynamics of young adult participants under conditions where they were required to voluntarily produce random and regular sway motions in contrast to that of standing still. Frequency, amplitude and regularity measures of the COP excursion and EMG...

This experiment examined the magnitude and structure of force variability in isometric index finger force production tasks at 5, 15, 25, 35, 45, 55, 65, 75, 85, and 95% of maximal force in two different finger orientations. In the finger flexion task, the participants generated a downward isometric force through index finger flexion. In the finger...

The paper addresses the process of human physiological development and aging from the perspective complexity at the structural level and functional levels. The goal is to present a view of the human lifespan as a continuous increase in structural complexity of the human system, resulting in increased independence of the physiological subsystems. Th...

We investigated the relationship between macroscopic entropy and microscopic complexity of the dynamics of body rocking and sitting still across adults with stereotyped movement disorder and mental retardation (profound and severe) against controls matched for age, height, and weight. This analysis was performed through the examination of center of...

The authors examined the effects of learning on the change in the organization of the mechanical and dynamical degrees of freedom in 5 men who performed a ski-simulator task. A 3-dimensional analysis of the motion of the total-body center of mass and the segmental centers of mass (head, torso, thighs, and shanks) over practice showed that the recru...

This experiment examined the acquisition of the global and local dynamics of the changes in the total body center of mass-platform and inter-limb coordination motions over the course of practice (20, 30 s trials each day for 7 days) in the ski-simulator task. Four blocks of trials, representative of early, moderate, and extensive practice were anal...

Abstract ,Skilled human movement,is apparently easily produced and highly coordinated despite the high number of degrees of freedom controlled during its execution. Here, we examine the learning of a whole body movement over practice from three levels of analysis: 1) elemental, 2)

This study examined the effects of practice on the behavior of the limb segments in a whole-body movement task. 5 male participants completed 7 practice sessions comprising 20 practice trials, each lasting 30s on the ski-simulator task. Kinematic data in 3-dimensions were obtained for the positions of the segmental centers of mass of the head, tors...

Includes abstract. Includes bibliographical references (leaves 116-120). Thesis (M.S.)--Ithaca College, 2004.