Mental rotation of hands and objects in ageing and Parkinson’s disease: Implications for understanding motor imagery

Motor imagery (MI) supports motor learning and performance, having the potential to be a useful tool for neurorehabilitation. However, MI ability may be impacted by ageing and neurodegeneration, which could limit its therapeutic effectiveness. MI is often assessed through a hand laterality task (HLT), whereby laterality judgements are typically slower for hands presented at orientations corresponding to physically more difficult postures (a “biomechanical constraint” effect). Performance is also found to differ between back and palm views of the hand, suggesting the differential involvement of visual and sensorimotor strategies. While older adults are generally found to be slowed and show increased biomechanical effects, few studies have examined the effects of both ageing and Parkinson’s disease (PD).The present study compared healthy younger (YA), healthy older (OA) and PD groups on HLT performance from both palm and back views, as well as an object-based (letter) mental rotation task. OA and PD groups were slower than YA, particularly when judging laterality from the back view, and exhibited increased biomechanical constraint effects for the palm. While response times were generally similar between OA and PD groups, the PD group showed reduced accuracy in the back view. Moreover, object rotation was slower and less accurate only in the PD group. The results indicate that different mechanisms are involved in mental rotation of hands viewed from the back or palm, consistent with previous findings, and demonstrate particular effects of ageing and PD when judging the back view. Alongside findings from studies of explicit MI, this suggests a greater alteration of visual than kinaesthetic MI with ageing and neurodegeneration, with additional impairment of object-based visual imagery in PD. The findings are also discussed in relation to different perspectives in MI and the integration of visual and kinaesthetic representations.

A Tale of Two Motives: Endogenous Time Preference, Cash-in-Advance Constraints and Monetary Policy

This paper demonstrates the effects of modeling an endogenous rate of time preference and two cash-in-advance constraints. If the constraint is levied on consumption and capital goods, time preference effects are neutral and cash-in-advance constraint effects invert the Tobin Effect. If the constraint applies solely to consumption goods, opposing motives are offsetting and monetary policy is super neutral.

A Tale of Two Motives: Endogenous Time Preference, Cash-in-Advance Constraints and Monetary Policy

This paper demonstrates the effects of modeling an endogenous rate of time preference and two cash-in-advance constraints. If the constraint is levied on consumption and capital goods, time preference effects are neutral and cash-in-advance constraint effects invert the Tobin Effect. If the constraint applies solely to consumption goods, opposing motives are offsetting and monetary policy is super neutral.

Size-Induced Constraint Effects on Crack Initiation and Propagation Parameters in Ductile Polymers

Fracture mechanics are of high interest for the engineering design and structural integrity assessment of polymeric materials; however, regarding highly ductile polymers, many open questions still remain in terms of fully understanding deformation and fracture behaviors. For example, the influence of the constraint and specimen size on the fracture behavior of polymeric materials is still not clear. In this study, a polymeric material with an elastic plastic deformation behavior (ABS, acrylonitrile butadiene styrene) is investigated with regard to the influence of constraint and specimen size. Different single-edge notched bending (SENB) specimen sizes with constant geometrical ratios were tested. The material key curve was used to investigate differences in the constraint, where changes for small and large specimen sizes were found. Based on a size-independent crack resistance curve (J–R curve), two apparent initiation parameters (J0.2 and Jbl) were determined, namely, the initiation parameter Jini (based on the crack propagation kinetics curve) and the initiation parameter JI,lim (based on an ESIS TC 4 draft protocol). It was found that J0.2 and Jbl could be used as crack initiation parameters whereby Jini and JI,lim are indicative of the onset of stable crack growth.

Feature Gluttony

This article develops a new approach to a family of hierarchy-effect inducing configurations, with a focus on Person Case Constraint effects, dative-nominative configurations, and copula constructions. The main line of approach in the recent literature is to attribute these effects to failures of φ-Agree or, more specifically, failures of nominal licensing or case checking. We propose that the problem in these configurations is unrelated to nominal licensing, but is instead the result of a probe participating in more than one Agree dependency, a configuration we refer to as feature gluttony. Feature gluttony does not in and of itself lead to ungrammaticality; rather, it can create irresolvably conflicting requirements for subsequent operations. We argue that in the case of clitic configurations, a probe that agrees with more than one DP creates an intervention problem for clitic doubling. In violations involving morphological agreement, gluttony in features may result in a configuration with no available morphological output.