Contraversive neglect? A modulation of visuospatial neglect in association with contraversive pushing

Objective: Contraversive pushing (CP) is a neurologic disorder characterized by a lateral postural imbalance. Pusher patients actively push toward their contralesional side due to a misperception of the body's orientation in relation to gravity. Although not every patient with CP suffers from spatial neglect (SN), both phenomena are highly correlated in right-hemispheric patients. The present study investigates whether peripersonal visuospatial functioning differs in neglect patients with versus without CP (NP+ vs. NP+ patients). Method: Eighteen right-hemispheric stroke patients with SN were included, of which 17 in a double-blind case-control study and 1 single case with posterior pushing to supplement the discourse. A computer-based visuospatial navigation task, in which lateralized deviation can freely emerge, was used to quantify visuospatial behavior. In addition, visuospatial orienting was monitored using line bisection. Results: Significant intergroup differences were found. The NP+ patients demonstrated a smaller ipsilesional navigational deviation and more cross-over (contralesional instead of ipsilesional deviation) in long line bisection. As such, they demonstrated a contraversive (contralesionally directed) shift in comparison with the NP+ patients. Conclusions: These findings highlight the similarity between 2 systems of space representation. They are consistent with a coherence between the neural processing system that mainly provides for postural control, and the one responsible for nonpredominantly postural, visuospatial behavior

Midpoints versus endpoints: The sacrifices and benefits

On May 25-26, 2000 in Brighton (England), the third in a series of international workshops was held under the umbrella of UNEP addressing issues in Life Cycle Impact Assessment (LCIA). The workshop provided a forum for experts to discuss midpoint vs. endpoint modeling. Midpoints are considered to be links in the cause-effect chain (environmental mechanism) of an impact category, prior to the endpoints, at which characterization factors or indicators can be derived to reflect the relative importance of emissions or extractions. Common examples of midpoint characterization factors include ozone depletion potentials, global warming potentials, and photochemical ozone (smog) creation potentials. Recently, however, some methodologies have adopted characterization factors at an endpoint level in the cause-effect chain for all categories of impact (e.g., human health impacts in terms of disability adjusted life years for carcinogenicity, climate change, ozone depletion, photochemical ozone creation; or impacts in terms of changes in biodiversity, etc.). The topics addressed at this workshop included the implications of midpoint versus endpoint indicators with respect to uncertainty (parameter, model and scenario), transparency and the ability to subsequently resolve trade-offs across impact categories using weighting techniques. The workshop closed with a consensus that both midpoint and endpoint methodologies provide useful information to the decision maker, prompting the call for tools that include both in a consistent framewor

Midpoint estimation applied to the vertical-horizontal illusion

Eighty-three college undergraduates estimated midpoints of vertical lines presented in cued (a letter or figure presented below the line), uncued, and inverted T conditions. Subject\u27s mean estimates were near the geometric midpoint in the two cued conditions, and significantly above the midpoint in the uncued and inverted T conditions. Mean estimates in the inverted T conditions were significantly above those in the uncued condition. These displacements are discussed in relation to previous midpoint estimation findings and theoretical explanations of the vertical-horizontal illusion. The midpoint estimation task is evaluated as an investigative tool in studies of geometric-optical illusions, and recommendations for further study are suggested

Three-dimensional fractal mountains

This study provides a guide to a series of systematic techniques used to create fractal mountains. The fractal mountains are created through an Interactive System for Fractal Mountains (ISFM) . To create the fractal mountains in ISFM a modified midpoint displacement technique in three dimensions is used. Augmenting the midpoint displacement algorithm is a random number generator that provides randomness in the displacement so as to simulate nature. These two algorithms plus an algorithm for lighting and for shading allow the user to develop different types of fractal mountains. When creating a fractal mountain with ISFM, the user has the options of placing the location of the light source for the time of day, of determining the ruggedness or texture of the mountain and of positioning the outline for a mountain range. ISFM generates a fractal mountain or a fractal mountain range on an IRIS workstation. ISFM provides a systematic and tutorial approach to creating fractal mountains that can be easily repeated by others.http://archive.org/details/threedimensional00collCivilian, Naval Postgraduate SchoolApproved for public release; distribution is unlimited

PARTICIPATION IN MULTIPLE-PERIL CROP INSURANCE: RISK ASSESSMENTS AND RISK PREFERENCES OF CRANBERRY GROWERS

To investigate the poor participation rate of cranberry growers in the multiple-peril crop insurance program, a sample of 15 Massachusetts growers was interviewed. According to their risk preferences, a much greater proportion of growers should have insured, than actually did. A possible solution is to match the distribution used by the insurer closer to that believed by the grower. Adjusting each grower's historical yield series for trend brought the historical and subjective mean yields much closer. However, an aggregate test found the effect of adjustment to be insignificant, implying that the avenue for increased participation lies elsewhere.Risk and Uncertainty,

Software Design of an Experimental Management Suite for Evaluating Time-Delayed Teleoperative Simulations

A means of assessing human performance as it relates to telesurgery is critical in an age where computer-assisted surgery is becoming more commonplace in operating rooms around the world. This is particularly true when a human is controlling the robotic instruments over a considerable geographic distance; unpredictable delays in data transmission over a network can degrade the human-computer system performance. As the delay is increased, so too will the overall time to complete a given task along with its associated error rate. However, objective measures on the effect on performance are needed. The methodology developed here is based on Fitts’ paradigm; a framework that can be used to quantify human performance under simulated latency conditions. Data gathered from the software developed in this thesis shows a strong, positive, linear correlation between a subject’s performance and the imposed task latency. This coincides with similar studies performed using the same paradigm, demonstrating the usefulness of such a methodology with respect to systems for telesurgery and training

Action observation and imitation in the healthy brain and in high-functioning adults with autism spectrum conditions

Accurate action perception plays an important role in social interaction enabling us to identify and appropriately respond to the behaviour of others. One such response is automatic imitation, the reflexive copying of observed body movements. Action perception is associated with activity in posterior brain areas, which feed into the Mirror Neuron System (MNS), a network of regions that has been associated with imitation and which is under the regulatory control of frontal brain areas. The fMRI study described in Chapter 2 demonstrated that in healthy adults, action perception can be subdivided into objective and subjective components which are primarily associated with activity in different brain areas. Chapter 3 demonstrated that activity in MNS areas, as measured by MEG, comprises an automatic motoric simulation of the kinematics of observed actions. Chapters 2 and 3 therefore enhance knowledge of the neural mechanisms of action perception in the typical brain. Previous studies have linked Autism Spectrum Conditions (ASC) with action perception and imitation impairments. Chapters 4 and 5 demonstrated that adults with ASC exhibit atypical action perception which is likely due to difficulties with subjective processing (i.e. knowing what a ‘natural’ human movement should look like) rather than with objective visual processing of human motion. Chapter 6 reported a lack of imitation in ASC: whereas typical adults imitated human movements more than robot movements, individuals with ASC failed to imitate. Chapter 7 suggested that problems with imitation in ASC may relate to difficulties with the control of imitation: whereas control participants show increased levels of imitation when in a positive social frame-of-mind individuals with ASC did not. Chapters 4 to 7 have implications for ASC. They suggest that atypical imitation may be due to atypical sensory input to the MNS (i.e. impaired action perception) and/or atypical control of imitation