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Biomedical subjects

E Greene

Publications and source records attributed to E Greene.

At least 19 recordsLinked to original sources
PubMed2003

Transcription defects induced by repeat expansion: fragile X syndrome, FRAXE mental retardation, progressive myoclonus epilepsy type 1, and Friedreich ataxia.

Fragile X mental retardation syndrome, FRAXE mental retardation, Progressive myoclonus epilepsy Type I, and Friedreich ataxia are members of a larger group of genetic disorders known as the Repeat Expansion Diseases. Unlike other members of this group, these four disorders all result from a primary defect in the initiation or elongation of transcription. In this review, we discuss current models for the relationship between the expanded repeat and the disease symptoms.

Base Sequence↗
PubMed2001

Verbal aggression in Alzheimer's disease. Clinical, functional and neuropsychological correlates.

OBJECTIVES: To determine the clinical, functional and neuropsychological correlates of verbal aggression in Alzheimer's disease in a group of consecutive first attendees to a memory clinic. METHODS: 150 people were evaluated and diagnosed as suffering with probable Alzheimer's disease. These people were tested using the Behave-AD for the presence of verbal aggression, delusions, depression and agitation. They were also assessed with cognitive, functional and neuropsychological scales. RESULTS: Twenty-eight per cent of this group of Alzheimer patients had exhibited some verbal aggression in the preceding month. Male gender (p = 0.022), the presence of paranoid and delusional ideation (p = 0.003) and agitation (p = 0.042) were significantly associated with verbal aggression in a stepwise backward logistic regression analysis. CONCLUSION: The presence of verbal aggression should prompt the clinician to search for delusional ideation, which may respond to pharmacotherapy.

Aged↗
PubMed2001

Recurrent falls are associated with increased length of stay in elderly psychiatric inpatients.

OBJECTIVES: To identify factors which may contribute to prolonged length of stay in an elderly psychiatric inpatient setting. DESIGN: Retrospective case note study. METHODS: A list of all patients over the age of 65 discharged from a private psychiatric hospital over a three-year period excluding those with a length of stay of over 365 days was obtained (n = 1147). A random sample of 150 patients was selected from the study population. A case note study was then performed looking at a number of variables which have been postulated to affect length of stay. The resulting data was analysed using multivariate statistics. RESULTS: There was no statistically significant association found between baseline factors (including age, gender, cognitive impairment, marital status, order of admission and preadmission living arrangement) and length of stay. Having recurrent falls whilst an inpatient was associated with prolonged hospital stay (p = 0.0006). CONCLUSION: Experiencing recurrent falls whilst an inpatient is associated with prolonged length of stay. Recurrent falls in the elderly may be associated with both physical illness and the use of psychotropic medications. A prospective study examining factors contributing to falls would be important in decreasing fall risk and reducing length of stay.

Accidental Falls↗
PubMed2001

Idiosyncratic profiles of collinearity error using segments and dot pairs.

It is well known that judgments of oblique line segments are more variable and less accurate than are judgments of horizontal or vertical segments, i.e., the "oblique effect." A prior study from our laboratories confirmed these differentials for a task in which the collinearity of segments at various angular positions was judged. Further, that study found that each observer manifests a distinct, idiosyncratic profile of errors across the 360 degrees range. These error tendencies are conspicuous in models derived by harmonic analysis, and we describe significant excursions of a given model as "delta errors." The present experiments found complex profiles of delta error with various stimulus and test conditions. A given subject manifested similar models of delta error when judging collinearity of dot pairs versus line segments. In the prior work the segments to be judged were asymmetrically positioned upon the test sheet. However, the asymmetric positioning is not responsible for the errors, as the present work found errors excursions with a round display field. Similar profiles of delta error were found when subjects were allowed to mark an open space, versus being required to respond at a specific distance (indicated by a target circle). This addresses questions of whether the error should be measured as an angle. In the two final experiments, we present evidence that the source of delta error within the nervous system is at the point of binocular synthesis of the information from the two eyes, or beyond, and the effects are not due to errors of reaching. Potential neural substrates for these complex, idiosyncratic error tendencies are discussed.

Discrimination Learning↗
PubMed2001

The effects of limiting punitive damage awards.

In response to concerns that jury awards in tort cases are excessive and unpredictable, nearly every state legislature has enacted some version of tort reform that is intended to curb extravagant damage awards. One of the most important and controversial reforms involves capping (or limiting) the maximum punitive damage award. We conducted a jury analogue study to assess the impact of this reform. In particular, we examined the possibility that capping punitive awards would cause jurors to inflate their compensatory awards to satisfy their desires to punish the defendant, particularly in situations where the defendant's conduct was highly reprehensible. Relative to a condition in which punitive damages were unlimited, caps on punitive damages did not result in inflation of compensatory awards. However, jurors who had no option to award punitive damages assessed compensatory damages at a significantly higher level than did jurors who had the opportunity to do so. We discuss the policy implications of these findings.

Adult↗
PubMed2001

The effects of defendant conduct on jury damage awards.

Laws of negligence dictate that jurors' decisions about damages be influenced by the severity of plaintiffs' injuries and not by the reprehensibility of defendants' conduct. The authors simulated an automobile negligence trial to assess whether jurors' decisions are in accord with those expectations. Conduct of the defendant and severity of the plaintiff's injuries were manipulated. Jurors listened to the evidence, completed predeliberation questionnaires, deliberated as a jury, and completed postdeliberation questionnaires. Severity of the plaintiff's injury had a strong impact on damage awards, but evidence related to the defendant's conduct was also influential, particularly when the plaintiffs injuries were mild. Here, jurors with any conduct-related evidence gave larger damage awards than jurors with no conduct-related evidence. Findings suggest an effect of defendant conduct on damage awards that may be mediated by judgments that the defendant was negligent.

Adolescent↗
PubMed2001

Evaluating models of collinearity judgment for reliability and scale.

In prior work from this laboratory, we have examined how accurately subjects can judge collinearity, i.e. alignment, as a function of the angular position of stimulus elements. In those experiments, subjects were presented with a line segment (or a pair of dots) which varied across the 360 degrees range of angular positions, and were required to select and mark a point which was perceived as being collinear. We found that the models of error for each subject consisted of a complex set of peaks and valleys which are herein described as delta excursions. The error tendencies appeared to be idiosyncratic, in that each subject manifested a different profile of these excursions. Here we report the results of three experiments. In the first, we tested subjects across five sessions, and found that the five models of error were fairly comparable for a given subject. In the second and third experiments, we tested at close intervals of angular position, and found evidence for localized sources of error. We continue to find that the error model for each subject is idiosyncratic, and argue that the excursions may be due to defects in a system which combines responses from position-encoding fields that vary in size.

Analysis of Variance↗
PubMed2001

Further consideration of size illusions in random dot stereograms.

It has been suggested that many geometric illusions are caused by the application of depth or size constancy rules to an image which does not have sufficient cues to establish that the elements lie in a flat plane. Thus, converging lines are taken as depth cues, and the attributed depth provides the basis for adjusting the perceived size of stimulus elements. It this is the case, one should not see a distortion of relative size if the disparity cues provide for strong statification, i.e., localization in depth of the linear perspective cues. This expectation is challenged by demonstrations that show distortions of relative size using random-dot stereograms. In 1971 Julesz provided such examples but did not comment on the implications for theories of depth. Here we redemonstrate these distortion of length and size in autostereograms which contain the Ponzo and Corridor configurations. The illusory distortions can be seen in the cyclopean view even though the linear perspective elements are well stratified. We suggest that the processing of binocular disparity cues, as required for judgments of absolute distance, may involve the dorsal stream of vision, i.e., activity passing into and including the parietal lobe. Pictorial cues, on the other hand, are likely passed through the ventral stream into the temporal lobe. The analysis of depth by this system provides for size constancy and, possibly, the calibration of relative motion.

Cues↗
PubMed2000

Disruptive sexual selection for plumage coloration in a passerine bird.

The theory of sexual selection was developed to explain the evolution of highly exaggerated sexual ornaments. Now supported by vast empirical evidence, sexual selection is generally considered to favour individuals with the most extreme trait expression. Here we describe disruptive selection on a sexual ornament, plumage coloration, in yearling male lazuli buntings (Passerina amoena). In habitats with limited good-quality nesting cover, the dullest and the brightest yearlings were more successful in obtaining high-quality territories, pairing with females and siring offspring, than yearlings with intermediate plumage. This pattern reflects the way that territorial adult males vary levels of aggression to influence the structure of their social neighbourhood. Adult males showed less aggression towards dull yearlings than intermediate and bright ones, permitting the dull yearlings to settle on good territories nearby. Fitness comparisons based on paternity analyses showed that both the adults and dull yearlings benefited genetically from this arrangement, revealing a rare example of sexually selected male-male cooperation.

Animals↗
PubMed2000

Compensating plaintiffs and punishing defendants: is bifurcation necessary?

Critics of the civil jury have proposed several procedural reforms to address the concern that damage awards are capricious and unpredictable. One such reform is the bifurcation or separation of various phases of a trial that involves multiple claims for damages. The purpose of this study was to assess the effects of bifurcating the compensatory and punitive damages phases of a civil tort trial. We manipulated the wealth of the defendant and the reprehensibility of the defendant's conduct (both sets of evidence theoretically related to punitive but not to compensatory damages) across three cases in a jury analog study. We wondered whether jurors would misuse the punitive damages evidence in fixing compensatory damages and whether bifurcation would effectively undo this practice. Our findings indicated that mock jurors did not improperly consider punitive damages evidence in their decisions about compensation. Moreover, bifurcation had the unexpected effect of augmenting punitive damage awards. These findings raise questions about the merits of bifurcation in cases that involve multiple claims for damages.

Crime Victims↗
PubMed2000

Individual differences in collinearity judgment as a function of angular position.

Previous research indicates that perceived orientation and/or alignment of segments and points can vary as a function of the angular position of the stimulus elements. Several studies show that the variability of the responses is least and accuracy of judgment is greatest where segments and dots are aligned with a cardinal axis. Additionally, some report assimilation of judgments toward the nearest cardinal axis--that is, the segments (or dots) are seen as being closer to the horizontal or vertical than is true. The present research confirms that judgments of collinearity are least variable and most accurate when the segment being judged is aligned with a cardinal axis. However, we do not find any consistent tendency for cardinal axis assimilation. Plotting the collinearity error (delta) as a function of angular position (phi), we find a distinctive profile of oscillation for each subject. Furthermore, subjects who were evaluated in two sessions showed very similar profiles of delta oscillation from Day 1 to Day 2. Harmonic analysis indicated a wide-ranging pattern of significant components. The components at the 4th harmonic and below were more likely to be significant, but each subject showed differential loadings in terms of which of the components were significant, as well as in the sign and amplitude of significant components. These results may reflect idiosyncratic fixation tendencies, or individual differences in the design of neural mechanisms that encode the angular positions of stimuli.

Humans↗
PubMed1998

Red squirrels, Tamiasciurus hudsonicus, produce predator-class specific alarm calls

Red squirrels, can produce alarm calls when they detect a potential predator. Observations of natural interactions between red squirrels and large birds, and predator-presentation experiments in the field, showed that red squirrels produce acoustically different alarm calls in response to aerial danger (live birds and a model hawk flown towards them) versus danger approaching from the ground (dogs and humans). The alarm call produced in response to aerial danger is acoustically convergent on the 'seet' alarm call produced by many species of passerine birds in response to raptors. The squirrels' 'seet' alarm is a short, low-amplitude, high-frequency call. These characteristics make the call difficult to localize, and is in a frequency range that is poorly perceived by raptors. Red squirrels produce much louder, wide-bandwidth bark calls in response to terrestrial danger. This is the first demonstration of predator-class specific alarm calls of red squirrels. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

A test of the gravity lens theory.

Naito and Cole [1994, in Contributions to Mathematical Psychology: Psychometrics and Methodology Eds G H Fischer and D Laming (New York: Springer)] provide a configuration which they describe as the Gravity Lens illusion. In this configuration, four small dots are presented in proximity to four large disks, and one is asked to compare the slope of an imaginary line which connects one pair of dots with the slope of a line which connects the other pair. In fact the slopes are the same, i.e. their axes are parallel, but because of the positioning of the large disks they appear to be at different orientations. Naito and Cole propose that the perceptual bias is analogous to the effects of gravity on the metrics of physical space, such that mental projections in the vicinity of a disk (or an open circle) are distorted just as the path of light is bent as it passes a massive body such as a star. Here we provide a simple test of this concept by having subjects judge alignments of dots which lie near tangents to a circle. Subjects were asked to project straight lines through pairs of stimulus dots, selecting and marking points in open space which were collinear with each pair. As would be predicted by the Gravity Lens theory, the locations selected by subjects were displaced from straight lines. However, the error magnitudes were substantially larger for judgments of dot pairs which had an oblique alignment, as compared with dot pairs which were aligned with a cardinal axis. This differential of effect as a function of stimulus orientation is not predicted by the gravity concept.

Form Perception↗
PubMed1998

Similar Müller-Lyer effects from operant and comparison response modes.

A one-sided (monopole) version of the Müller-Lyer was used to assess the effect of response mode on the metric distortion associated with the illusion. Two different response modes were tested for comparability. The Operant Mode required the judgment of stimulus span to be indicated by marking a dot on the test page. The Comparison Mode required judgment of equality of two adjoining prepositioned spans. The perceptual effects with the comparison procedure are known to consist of underestimation of spans which are bounded by concave fin-sets and over-estimation of spans which are bounded by convex fin-sets. The question is whether the motor demands of the operant task produce an additional source of metric bias. Analysis indicate a very high correlation of judgments for the two modes of testing. Also, data with either mode of responding closely fit a linear model of the effect, and the model provides comparable index values for the concave and convex versions. These results should mitigate concern about potential motor bias from the operant method and encourage its use as a more efficient procedure for assessing metric distortion.

Distance Perception↗
PubMed1997

Evaluating the decay gradient for collinearity bias with lateral displacement from the axis of induction.

The misperception of alignment which is found in many geometric illusions can be quantified using relatively simple stimulus configurations. Perceived collinearity of one segment (designated as the test segment) is biased by a second segment (designated as the induction segment), with the size of effect being a function of the relative angle between the two segments. The process can be described as angular induction. The strength of bias is greatest when the induction segment is centered at the tip of the test segment. Tong and Weintraub have reported that lateral displacement from the tip, i.e., at right angles to the axis of the induction segment, produces a sharp drop in the strength of effect. This decline is described as a "decay gradient" for the angular induction. One experiment replicates and provides better quantification of this "decay gradient". Two other experiments examine the decay gradient using a pair of induction segments, one on each side of the tip of the test segment. Displacement of the segments (either in the same direction or in opposite directions) produces substantially the same gradient of effect. Therefore, previous evidence of "tandem boosting" of effect for segment pairs does not depend on collinearity among the stimulus components. Finally, a fourth experiment finds that an induction segment which is at a fixed position and orientation differentially affects the influence of a variable induction segment. At some angles the influence of the variable segment is augmented, and at others it is suppressed. These findings are discussed in a neuroreductionist context, and a simple model for angular induction is presented.

Analysis of Variance↗
PubMed1997

Evaluating Müller-Lyer effects using single fin-set configurations.

Four experiments were conducted to study the bias of perceived length for Müller-Lyer configurations that contained a single set of fins (i.e., two segments that join to form a vertex). The experiments manipulated several factors that have been shown to be critical to the effect: (1) version (which way the apex pointed), (2) length of the stimulus span, (3) presence or absence of a line segment in the span being judged, (4) fin length, (5) fin angle, and (6) the zone in which the response was rendered. Using percent error as the index of perceptual distortion, the major finding was that the two versions show an opposite slope for strength of effect as a function of span. When stimulus spans were plotted against response means (not converting to percent error), an almost perfect linear relation was found. These results indicate that the perceptual effects can be modeled as a linear system having two parameters through which the treatments exert their influence. The results are discussed in relation to major theories of mechanism for the Müller-Lyer illusion.

Adult↗
PubMed1996

Synaptic membrane G proteins are complexed with tubulin in situ.

The G proteins G S and Gi1 appear to be capable of binding to tubulin specifically, and it has been suggested that such binding results in G protein activation via direct transfer of GTP. This study was undertaken to demonstrate that consequences of G protein activation by tubulin, i.e., stimulation or inhibition of adenyl cyclase, were dependent on the G proteins expressed as well as unique aspects of the membrane or cytoskeleton in a given cell type. Membranes from rat C6 glioma cells, which express G s alpha but not G i alpha 1, responded to the addition of tubulin with a stable activation of adenyl cyclase. Conversely, membranes from rat cerebral cortex, which contain both G s and G i 1, responded to exogenous tubulin with a stable inhibition of adenyl cyclase. Unlike C6 membranes, cerebral cortex membranes are richly endowed with tubulin, and antitubulin antibodies immunoprecipitated complexes of tubulin and G i 1 and G s from detergent extracts of these membranes. Nearly 90% of the G s alpha from Triton X-114 extracts coimmunoprecipitated with tubulin, suggesting that these proteins exist as a complex in the synaptic membrane. Such complexes may provide the framework for a G protein-cytoskeleton link that participates in the modulation of cellular signal transduction.

Adenylyl Cyclase Inhibitors↗