Bio-analog dissipative structures and principles of biological behavior.

The place of living organisms in the natural world is a nearly perennial question in philosophy and the sciences; how can inanimate matter yield animate beings? A dominant answer for several centuries has been to treat organisms as sophisticated machines, studying them with the mechanistic physics and chemistry that have given rise to technology and complex machines. Since the early 20th century, many scholars have sought instead to naturalize biology through thermodynamics, recognizing the precarious far-from-equilibrium state of organisms. Erwin Bauer was an early progenitor of this perspective with ambitions of "general laws for the movement of living matter". In addition to taking a thermodynamic perspective, Bauer recognized that organisms are fundamentally behaving systems, and that explaining the physics of life requires explaining the origins of intentionality, adaptability, and self-regulation. Bauer, like some later scholars, seems to advocate for a "new physics", one that extends beyond mechanics and classical thermodynamic, one that would be inclusive of living systems. In this historical review piece, we explore some of Bauer's ideas and explain how similar concepts have been explored in modern non-equilibrium thermodynamics and dissipative structure theory. Non-living dissipative structures display end-directedness, self-maintenance, and adaptability analogous to organisms. These findings also point to an alternative framework for the life sciences, that treats organisms not as machines but as sophisticated dissipative structures. We evaluate the differences between mechanistic and thermodynamic perspectives on life, and what each theory entails for understanding the behavior of organisms.

Foraging Dynamics and Entropy Production in a Simulated Proto-Cell.

All organisms depend on a supply of energetic resources to power behavior and the irreversible entropy-producing processes that sustain them. Dissipative structure theory has often been a source of inspiration for better understanding the thermodynamics of biology, yet real organisms are inordinately more complex than most laboratory systems. Here we report on a simulated chemical dissipative structure that operates as a proto cell. The simulated swimmer moves through a 1D environment collecting resources that drive a nonlinear reaction network interior to the swimmer. The model minimally represents properties of a simple organism including rudimentary foraging and chemotaxis and an analog of a metabolism in the nonlinear reaction network. We evaluated how dynamical stability of the foraging dynamics (i.e., swimming and chemotaxis) relates to the rate of entropy production. Results suggested a relationship between dynamical steady states and entropy production that was tuned by the relative coordination of foraging and metabolic processes. Results include evidence in support of and contradicting one formulation of a maximum entropy production principle. We discuss the status of this principle and its relevance to biology.

The importance of visual control and biomechanics in the regulation of gesture-speech synchrony for an individual deprived of proprioceptive feedback of body position.

Do communicative actions such as gestures fundamentally differ in their control mechanisms from other actions? Evidence for such fundamental differences comes from a classic gesture-speech coordination experiment performed with a person (IW) with deafferentation (McNeill, 2005). Although IW has lost both his primary source of information about body position (i.e., proprioception) and discriminative touch from the neck down, his gesture-speech coordination has been reported to be largely unaffected, even if his vision is blocked. This is surprising because, without vision, his object-directed actions almost completely break down. We examine the hypothesis that IW's gesture-speech coordination is supported by the biomechanical effects of gesturing on head posture and speech. We find that when vision is blocked, there are micro-scale increases in gesture-speech timing variability, consistent with IW's reported experience that gesturing is difficult without vision. Supporting the hypothesis that IW exploits biomechanical consequences of the act of gesturing, we find that: (1) gestures with larger physical impulses co-occur with greater head movement, (2) gesture-speech synchrony relates to larger gesture-concurrent head movements (i.e. for bimanual gestures), (3) when vision is blocked, gestures generate more physical impulse, and (4) moments of acoustic prominence couple more with peaks of physical impulse when vision is blocked. It can be concluded that IW's gesturing ability is not based on a specialized language-based feedforward control as originally concluded from previous research, but is still dependent on a varied means of recurrent feedback from the body.

Functional Interdependence in Coupled Dissipative Structures: Physical Foundations of Biological Coordination.

Coordination within and between organisms is one of the most complex abilities of living systems, requiring the concerted regulation of many physiological constituents, and this complexity can be particularly difficult to explain by appealing to physics. A valuable framework for understanding biological coordination is the coordinative structure, a self-organized assembly of physiological elements that collectively performs a specific function. Coordinative structures are characterized by three properties: (1) multiple coupled components, (2) soft-assembly, and (3) functional organization. Coordinative structures have been hypothesized to be specific instantiations of dissipative structures, non-equilibrium, self-organized, physical systems exhibiting complex pattern formation in structure and behaviors. We pursued this hypothesis by testing for these three properties of coordinative structures in an electrically-driven dissipative structure. Our system demonstrates dynamic reorganization in response to functional perturbation, a behavior of coordinative structures called reciprocal compensation. Reciprocal compensation is corroborated by a dynamical systems model of the underlying physics. This coordinated activity of the system appears to derive from the system's intrinsic end-directed behavior to maximize the rate of entropy production. The paper includes three primary components: (1) empirical data on emergent coordinated phenomena in a physical system, (2) computational simulations of this physical system, and (3) theoretical evaluation of the empirical and simulated results in the context of physics and the life sciences. This study reveals similarities between an electrically-driven dissipative structure that exhibits end-directed behavior and the goal-oriented behaviors of more complex living systems.

Easier Said Than Done? Task Difficulty's Influence on Temporal Alignment, Semantic Similarity, and Complexity Matching Between Gestures and Speech.

Gestures and speech are clearly synchronized in many ways. However, previous studies have shown that the semantic similarity between gestures and speech breaks down as people approach transitions in understanding. Explanations for these gesture-speech mismatches, which focus on gestures and speech expressing different cognitive strategies, have been criticized for disregarding gestures' and speech's integration and synchronization. In the current study, we applied three different perspectives to investigate gesture-speech synchronization in an easy and a difficult task: temporal alignment, semantic similarity, and complexity matching. Participants engaged in a simple cognitive task and were assigned to either an easy or a difficult condition. We automatically measured pointing gestures, and we coded participant's speech, to determine the temporal alignment and semantic similarity between gestures and speech. Multifractal detrended fluctuation analysis was used to determine the extent of complexity matching between gestures and speech. We found that task difficulty indeed influenced gesture-speech synchronization in all three domains. We thereby extended the phenomenon of gesture-speech mismatches to difficult tasks in general. Furthermore, we investigated how temporal alignment, semantic similarity, and complexity matching were related in each condition, and how they predicted participants' task performance. Our study illustrates how combining multiple perspectives, originating from different research areas (i.e., coordination dynamics, complexity science, cognitive psychology), provides novel understanding about cognitive concepts in general and about gesture-speech synchronization and task difficulty in particular.

Mitochondrial dynamics and bioenergetics regulated by netrin-1 in oligodendrocytes.

Mitochondria are dynamic organelles that produce energy and molecular precursors that are essential for myelin synthesis. Unlike in neurons, mitochondria in oligodendrocytes increase intracellular movement in response to glutamatergic activation and are more susceptible to oxidative stress than in astrocytes or microglia. The signaling pathways that regulate these cell type-specific mitochondrial responses in oligodendrocytes are not understood. Here, we visualized mitochondria migrating through thin cytoplasmic channels crossing myelin basic protein-positive compacted membranes and localized within paranodal loop cytoplasm. We hypothesized that local extracellular enrichment of netrin-1 might regulate the recruitment and function of paranodal proteins and organelles, including mitochondria. We identified rapid recruitment of mitochondria and paranodal proteins, including neurofascin 155 (NF155) and the netrin receptor deleted in colorectal carcinoma (DCC), to sites of contact between oligodendrocytes and netrin-1-coated microbeads in vitro. We provide evidence that Src-family kinase activation and Rho-associated protein kinase (ROCK) inhibition downstream of netrin-1 induces mitochondrial elongation, hyperpolarization of the mitochondrial inner membrane, and increases glycolysis. Our findings identify a signaling mechanism in oligodendrocytes that is sufficient to locally recruit paranodal proteins and regulate the subcellular localization, morphology, and function of mitochondria.

Gesture-speech physics in fluent speech and rhythmic upper limb movements.

It is commonly understood that hand gesture and speech coordination in humans is culturally and cognitively acquired, rather than having a biological basis. Recently, however, the biomechanical physical coupling of arm movements to speech vocalization has been studied in steady-state vocalization and monosyllabic utterances, where forces produced during gesturing are transferred onto the tensioned body, leading to changes in respiratory-related activity and thereby affecting vocalization F0 and intensity. In the current experiment (n = 37), we extend this previous line of work to show that gesture-speech physics also impacts fluent speech. Compared with nonmovement, participants who are producing fluent self-formulated speech while rhythmically moving their limbs demonstrate heightened F0 and amplitude envelope, and such effects are more pronounced for higher-impulse arm versus lower-impulse wrist movement. We replicate that acoustic peaks arise especially during moments of peak impulse (i.e., the beat) of the movement, namely around deceleration phases of the movement. Finally, higher deceleration rates of higher-mass arm movements were related to higher peaks in acoustics. These results confirm a role for physical impulses of gesture affecting the speech system. We discuss the implications of gesture-speech physics for understanding of the emergence of communicative gesture, both ontogenetically and phylogenetically.

Dissipative Structures, Organisms and Evolution.

Self-organization in nonequilibrium systems has been known for over 50 years. Under nonequilibrium conditions, the state of a system can become unstable and a transition to an organized structure can occur. Such structures include oscillating chemical reactions and spatiotemporal patterns in chemical and other systems. Because entropy and free-energy dissipating irreversible processes generate and maintain these structures, these have been called dissipative structures. Our recent research revealed that some of these structures exhibit organism-like behavior, reinforcing the earlier expectation that the study of dissipative structures will provide insights into the nature of organisms and their origin. In this article, we summarize our study of organism-like behavior in electrically and chemically driven systems. The highly complex behavior of these systems shows the time evolution to states of higher entropy production. Using these systems as an example, we present some concepts that give us an understanding of biological organisms and their evolution.

Energy flows in gesture-speech physics: The respiratory-vocal system and its coupling with hand gestures.

Expressive moments in communicative hand gestures often align with emphatic stress in speech. It has recently been found that acoustic markers of emphatic stress arise naturally during steady-state phonation when upper-limb movements impart physical impulses on the body, most likely affecting acoustics via respiratory activity. In this confirmatory study, participants (N = 29) repeatedly uttered consonant-vowel (/pa/) mono-syllables while moving in particular phase relations with speech, or not moving the upper limbs. This study shows that respiration-related activity is affected by (especially high-impulse) gesturing when vocalizations occur near peaks in physical impulse. This study further shows that gesture-induced moments of bodily impulses increase the amplitude envelope of speech, while not similarly affecting the Fundamental Frequency (F0). Finally, tight relations between respiration-related activity and vocalization were observed, even in the absence of movement, but even more so when upper-limb movement is present. The current findings expand a developing line of research showing that speech is modulated by functional biomechanical linkages between hand gestures and the respiratory system. This identification of gesture-speech biomechanics promises to provide an alternative phylogenetic, ontogenetic, and mechanistic explanatory route of why communicative upper limb movements co-occur with speech in humans.

Acoustic information about upper limb movement in voicing.

We show that the human voice has complex acoustic qualities that are directly coupled to peripheral musculoskeletal tensioning of the body, such as subtle wrist movements. In this study, human vocalizers produced a steady-state vocalization while rhythmically moving the wrist or the arm at different tempos. Although listeners could only hear and not see the vocalizer, they were able to completely synchronize their own rhythmic wrist or arm movement with the movement of the vocalizer which they perceived in the voice acoustics. This study corroborates recent evidence suggesting that the human voice is constrained by bodily tensioning affecting the respiratory-vocal system. The current results show that the human voice contains a bodily imprint that is directly informative for the interpersonal perception of another's dynamic physical states.

Grasp Affordances in Bistable Perception of the Necker Cube.

Stimulus-response compatibility effects illustrate the mutual depen-dence of perception and action processes. Ellis and Tucker (2000) showed that object identification was facilitated when the response required a grip that was compatible with the stimulus. In the current study, we extend grip-compatibility effects to perception of the Necker cube. Participants reported the perceived orientation of a Necker cube by orienting a hand-held cube into a compatible or an incompatible position. Participants in the incompatible condition were quickly attracted to the FRB (front-side right bottom) percept, consistent with previous work. However, participants in the compatible condition showed an extended period of metastability, switching between the two perceptual states about equally. A second experiment replicated these results and showed that a control condition in which responses were made with a key press produced intermediate levels of metastability. These results are interpreted in terms of the dynamics of bistable perception.

Gesture-speech physics: The biomechanical basis for the emergence of gesture-speech synchrony.

The phenomenon of gesture-speech synchrony involves tight coupling of prosodic contrasts in gesture movement (e.g., peak velocity) and speech (e.g., peaks in fundamental frequency; F0). Gesture-speech synchrony has been understood as completely governed by sophisticated neural-cognitive mechanisms. However, gesture-speech synchrony may have its original basis in the resonating forces that travel through the body. In the current preregistered study, movements with high physical impact affected phonation in line with gesture-speech synchrony as observed in natural contexts. Rhythmic beating of the arms entrained phonation acoustics (F0 and the amplitude envelope). Such effects were absent for a condition with low-impetus movements (wrist movements) and a condition without movement. Further, movement-phonation synchrony was more pronounced when participants were standing as opposed to sitting, indicating a mediating role for postural stability. We conclude that gesture-speech synchrony has a biomechanical basis, which will have implications for our cognitive, ontogenetic, and phylogenetic understanding of multimodal language. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

The quantification of gesture-speech synchrony: A tutorial and validation of multimodal data acquisition using device-based and video-based motion tracking.

There is increasing evidence that hand gestures and speech synchronize their activity on multiple dimensions and timescales. For example, gesture's kinematic peaks (e.g., maximum speed) are coupled with prosodic markers in speech. Such coupling operates on very short timescales at the level of syllables (200 ms), and therefore requires high-resolution measurement of gesture kinematics and speech acoustics. High-resolution speech analysis is common for gesture studies, given that field's classic ties with (psycho)linguistics. However, the field has lagged behind in the objective study of gesture kinematics (e.g., as compared to research on instrumental action). Often kinematic peaks in gesture are measured by eye, where a "moment of maximum effort" is determined by several raters. In the present article, we provide a tutorial on more efficient methods to quantify the temporal properties of gesture kinematics, in which we focus on common challenges and possible solutions that come with the complexities of studying multimodal language. We further introduce and compare, using an actual gesture dataset (392 gesture events), the performance of two video-based motion-tracking methods (deep learning vs. pixel change) against a high-performance wired motion-tracking system (Polhemus Liberty). We show that the videography methods perform well in the temporal estimation of kinematic peaks, and thus provide a cheap alternative to expensive motion-tracking systems. We hope that the present article incites gesture researchers to embark on the widespread objective study of gesture kinematics and their relation to speech.

Predictors for recovery of macular function after surgery for primary macula-off rhegmatogenous retinal detachment.

PURPOSE: To determine predictors of best-corrected postoperative visual acuity (VA) in patients who underwent surgical intervention for macula-off rhegmatogenous retinal detachment. MATERIALS AND METHODS: Primary macula-off retinal detachments from the University of Colorado Primary Rhegmatogenous Retinal Detachment Database (2012-2017) were reviewed. The primary outcome measure was a postoperative VA of 20/40 or better at least 6 months after surgery. Patient demographics, medical history, duration of central vision loss before surgery, examination findings, operative technique, and postoperative findings were analyzed as possible predictors of postoperative visual recovery to 20/40 or better. Chi-square or Fisher's exact test was used to compare categorical variables, and Wilcoxon rank sum test was used for continuous variables. A multivariable logistic regression analysis was used to determine the adjusted odds ratios and 95% confidence intervals for variables that were significant in the univariable analyses. Statistical significance was set at p < 0.05. RESULTS: One hundred thirty-one patients met inclusion criteria. Eighty-one (61.8%) patients achieved a postoperative VA of 20/40 or better 6 or more months after surgery. Patients with a single retinal break were more likely than patients with more than one break to reach a postoperative VA of 20/40 or better (76.9% vs. 55.4%, p = 0.021). Patients with a better preoperative logMAR VA had better postoperative VA (p = 0.021). Duration of central vision loss prior to surgical repair was not related to final postoperative VA in this particular study. CONCLUSION: Postoperative recovery of visual acuity to 20/40 or better was significantly more common in patients with a single retinal break as well as in patients with better preoperative visual acuity. Duration of central vision loss prior to surgical repair was not significantly associated with postoperative VA.

Particle Flock Motion at Air-Water Interface Driven by Interfacial Free Energy Foraging.

From flocks of birds and sheep to colonies of bacteria, complex patterns and self-motion are found in all hierarchies of nature. Artificial nonliving systems provide useful insight, since living systems are complicated and may involve cognitive issues not found in nonliving matter. Herein, we report naturally flocking irregularly shaped benzoquinone (BQ) particles on the air-water interface that cross a gate. In this open system designed with absence of external control, the particle flock moves by Marangoni "surfing" driven by slow dissolution of weakly surface active BQ postulated to create inhomogeneous interfacial tension fields. The particle flocks move collectively through a gate placed in the air-water interface to the side that has higher interfacial tension. Position-sensitive surface tension measurements used for the first time in a multiparticle Marangoni motion system show unequivocally that flock motion and gate crossing proceed to areas of slightly higher interfacial tension. Flock crossing is accompanied by a low-high differential interfacial tension change from one side of the gate to the other, with the flock moving to the side with higher interfacial tension. Thus, the flocks move because they are foraging for interfacial free energy.

Oscillatory dynamics of an electrically driven dissipative structure.

Physical systems open to a flow of energy can exhibit spontaneous symmetry breaking and self-organization. These nonequilibrium self-organized systems are known as dissipative structures. We study the oscillatory mode of an electrically driven dissipative structure. Our system consists of aluminum beads in shallow oil, which, when subjected to a high voltage, self-organize into connected 'tree' structures. The tree structures serve as pathways for the conduction of charge to ground. This system shows a variety of spatio-temporal behaviors, such as oscillating movement of the tree structures. Utilizing a dynamical systems model of the electromagnetic phenomena, we explore a potential mechanism underlying the system's behavior and use the model to make additional empirical predictions. The model reproduces the oscillatory behavior observed in the real system, and the behavior of the real system is consistent with predictions from the model under various constraints. From the empirical results and the mathematical model, we observe a tendency for the system to select modes of behavior with increased dissipation, or higher rates of entropy production, in accord with the proposed Maximum Entropy Production (MEP) Principle.

Thermal- and Magnetic-Sensitive Particle Flocking Motion at the Air-Water Interface.

Collective self-motion of particulate systems provides novel opportunities for developing flocking and sensing functions from seemingly inanimate objects. In this paper, we report videos documenting spontaneous collective flocking of multiple irregularly shaped macroscopic benzoquinone (BQ) particles at the air-water interface. Self-propulsion occurs due to the Gibbs-Marangoni effect surface tension gradients generated by the BQ particles. The air-water interface develops inhomogeneous interfacial tension fields created by differential dissolution at points and edges of BQ particles, causing interfacial tension variations along the solid-liquid-air interfaces. Responses of irregularly shaped BQ particles to these driving forces do not result in random motion but lead to a cooperative hydrodynamic flocking. Curiously, the flocking behavior was very evident for irregularly shaped particles but not observed for symmetric circular BQ disks. The flock responds to changes in its local environment as it forages for interfacial free energy. It exhibits warm and cool thermotaxis and thus can sense local temperature changes. Also, though a single magnetic bead is not confined to a part of the Petri dish by an applied magnetic field, when this magnetic bead is a member of a flock in which all of the other beads are not magnetic, the flock as a whole moves and hovers around the region where the field is maximum. In other words, the magnetic bead becomes a kind of "sensor" for the flock to respond to a magnetic field, the response being a drift in the direction of the field.

Entrainment and Modulation of Gesture-Speech Synchrony Under Delayed Auditory Feedback.

Gesture-speech synchrony re-stabilizes when hand movement or speech is disrupted by a delayed feedback manipulation, suggesting strong bidirectional coupling between gesture and speech. Yet it has also been argued from case studies in perceptual-motor pathology that hand gestures are a special kind of action that does not require closed-loop re-afferent feedback to maintain synchrony with speech. In the current pre-registered within-subject study, we used motion tracking to conceptually replicate McNeill's () classic study on gesture-speech synchrony under normal and 150 ms delayed auditory feedback of speech conditions (NO DAF vs. DAF). Consistent with, and extending McNeill's original results, we obtain evidence that (a) gesture-speech synchrony is more stable under DAF versus NO DAF (i.e., increased coupling effect), (b) that gesture and speech variably entrain to the external auditory delay as indicated by a consistent shift in gesture-speech synchrony offsets (i.e., entrainment effect), and (c) that the coupling effect and the entrainment effect are co-dependent. We suggest, therefore, that gesture-speech synchrony provides a way for the cognitive system to stabilize rhythmic activity under interfering conditions.