Mathematical models of central pattern generators in locomotion: II. Single limb models for locomotion in the cat

Three mathematical models of central pattern generation for locomotion in the single limb of the cat are presented. In each model, the activities in populations of neurons controlling limb joint flexors and extensors are described by a system of nonlinear differential equations. Each solution of the system for a different set of parameters corresponds to a simulation of some gait of the cat. Model I is based on unit generators for each limb joint muscle group and assumes that flexors inhibit their paired extensors, but not vice-versa. Model IIa assumes that flexors and extensors are mutually inhibitory, but that only the flexors have inherent oscillatory capability. Model IIb assumes flexors and extensors are mutually inhibitory and that both flexors and extensors have oscillatory capability. The properties of each of these models are explored, compared and contrasted, and discussed in relation to the experimental literature. All three models are shown to be capable of generating patterns consistent with various stepping rates of the cat and to show appropriate muscle sequencing and flexor-extensor interactions. Further, all three models exhibit smooth initiation and termination of stepping. However, Model I seems to provide a more parsimonious account of producing changes in stepping rate and is preferred, therefore, over models IIa and IIb.     

Mathematical Models of Central Pattern Generators in Locomotion

Possible neural connective patterns and functions with respect to interlimb coordination are studied theoretically with a mathematical model of the central pattern generating system for cat locomotion. Activities in populations of neurons controlling limb joint flexors and extensors in all four limbs are represented by a system of nonlinear differential equations. Solutions of the system for various parameter values simulate various gaits of the cat. The model is shown to be capable of generating all gaits of the cat and accounting for corresponding phase changes in interlimb coordination. The model also exhibits smooth changes of gait, and smooth initiation and termination of stepping. Further, within each limb, muscle sequencing, step cycle phases, and flexor-extensor interactions can be studied. The model suggests that one of the simplest mechanisms for a central command system to change the gait is via inhibition of specific interlimb propriospinal pathways. In a final section, properties of both proposed single limb and interlimb models are reviewed with specific reference to planning future experimental and theoretical studies.     

Soul-making theodicy and compatibilism: new problems and a new interpretation

In the elaboration of his soul-making theodicy, John Hick agrees with a controversial point made by compatibilists Antony Flew and John Mackie against the free will defense. Namely, Hick grants that God could have created humans such that they would be free to sin but would, in fact, never do so. In this paper, I identify three previously unrecognized problems that arise from his initial concession to, and ultimate rejection of, compatibilism. The first problem stems from the fact that in two important texts, Hick rejects compatibilism (after having endorsed it as effective against the free will defense) for different and seemingly contradictory reasons. His various explanations of soul-making theodicy’s relationship to compatibilism are therefore in conflict. The second problem is closely related to the first. It turns out that when Hick’s concession to compatibilism is closely examined, soul-making theodicy appears unable to explain the existence of moral evil. The final problem consists in understanding why Hick would have made any concessions to compatibilism in the first place given that he ultimately opts for incompatibilist free will. After identifying these three problems, I develop a distinctive way in which to interpret Hick’s soul-making theodicy that solves the first two. This distinctive interpretation, moreover, has the added benefit of solving another, well-recognized problem that has long plagued Hick’s exposition: the problem of the hypnotist metaphor. Finally, I address the third problem by suggesting a rationale for Hick’s initial concession to the compatibilists.     

VA Puget Sound Telemental Health Service to rural veterans: a growing program

The VA Puget Sound Health Care System Telemental Health program connects veterans with psychologists, psychiatrists, and social workers via live clinical video teleconferencing. Providers deliver care to veterans in rural Veteran Affairs medical centers, community-based outpatient clinics and residences, and thus, increase access to specialty mental health care for rural and medically underserved veteran communities.     

Effects of Situational Judgment Test Format on Reliability and Validity

Single-response situational judgment tests (SRSJTs) differ from multiple-response SJTs (MRSJTS) in that they present test takers with edited critical incidents and simply ask test takers to read over the action described and evaluate it according to its effectiveness. Research comparing the reliability and validity of SRSJTs and MRSJTs is thus far extremely limited. The study reported here directly compares forms of a SRSJT and MRSJT and explores the reliability, convergent validity, and predictive validity of each format. Results from this investigation present preliminary evidence to suggest SRSJTs may produce internal consistency reliability, convergent validity, and predictive validity estimates that are comparable to those achieved with many traditional MRSJTs. We conclude by discussing practical implications for personnel selection and assessment, and future research in psychological science more broadly.     

Alcohol-aggression expectancies and dispositional rumination moderate the effect of alcohol consumption on alcohol-related aggression and hostility

Alcohol consumption increases aggression, but only in some drinkers. This study extends previous work to show how expectancies for alcohol-induced aggression and dispositional rumination moderate the link between alcohol consumption and alcohol-related aggression and hostility in a sample of 285 men and women. Alcohol-aggression expectancies and quantity of alcohol interacted to predict alcohol-related hostility and aggression. Trait rumination moderated the effect of alcohol consumption on aggressive acts. Finally, women who ruminated were more likely to report alcohol-related aggression than were men who ruminated. These results suggest that alcohol expectancies for aggression and rumination constitute two important cognitive facilitators of alcohol-related aggression and hostility, and that gender plays an important role in these relations.     

Alcohol‐aggression expectancies and dispositional aggression moderate the relationship between alcohol consumption and alcohol‐related violence

Alcohol consumption increases aggression, but only in some drinkers. This study examines how expectancies for alcohol‐induced aggression and dispositional aggression moderate the link between alcohol consumption and alcohol‐related violence, building on previous studies that have employed limited measures of alcohol‐related violence and included few women. A sample of 212 men and women reported their alcohol consumption, alcohol‐aggression expectancies, dispositional aggression, and incidents of alcohol‐related aggressive acts. Alcohol‐aggression expectancies and quantity of alcohol consumed interacted to predict alcohol‐related aggression. Alcohol‐aggression expectancies covaried with alcohol‐related aggressive acts, particularly in heavier drinkers. Dispositional aggression also correlated with alcohol‐related aggression among heavier drinkers. These results help identify that alcohol might increase aggression only among heavy drinkers who expect alcohol to increase aggression or who are dispositionally aggressive. Aggr. Behav. 32:517–527, 2006. © 2006 Wiley‐Liss, Inc.     

Mathematical models of central pattern generators in locomotion: I. Current problems

As a background for subsequent studies of mathematical models of central pattern generators in locomotion (Stafford & Barnwell, 1985a, b) relevant aspects of the literature on locomotion are reviewed, concepts of locomotion discussed, and extant models considered. Advantages and disadvantages of present models are discussed, and the need for mathematical models is emphasized. It is shown that realistic models of pattern generation in locomotion must take numerous factors into account, including phases of step cycle, muscle sequencing, gait and interlimb coordination, initiation and cessation of locomotion, and many aspects of neuromuscular control and function.     

Mathematical models of central pattern generators in locomotion: III. Interlimb model for the cat

Possible neural connective patterns and functions with respect to interlimb coordination are studied theoretically with a mathematical model of the central pattern generating system for cat locomotion. Activities in populations of neurons controlling limb joint flexors and extensors in all four limbs are represented by a system of nonlinear differential equations. Solutions of the system for various parameter values simulate various gaits of the cat. The model is shown to be capable of generating all gaits of the cat and accounting for corresponding phase changes in interlimb coordination. The model also exhibits smooth changes of gait, and smooth initiation and termination of stepping. Further, within each limb, muscle sequencing, step cycle phases, and flexor-extensor interactions can be studied. The model suggests that one of the simplest mechanisms for a central command system to change the gait is via inhibition of specific interlimb propriospinal pathways. In a final section, properties of both proposed single limb and interlimb models are reviewed with specific reference to planning future experimental and theoretical studies.