Creutzfeldt-Jakob disease in unusually young patients who consumed venison.

BACKGROUND: Creutzfeldt-Jakob disease (CJD) in humans and chronic wasting disease (CWD) in deer and elk occur in the United States. Recent reports of 3 unusually young patients with CJD who regularly consumed deer or elk meat created concern about the possible zoonotic transmission of CWD. OBJECTIVE: To examine the possible transmission of CWD to humans. PATIENTS: Three unusually young patients (aged 28, 28, and 30 years) with CJD in the United States during 1997-2000. METHODS: We reviewed medical records and interviewed family members and state wildlife and agriculture officials. Brain tissue samples were tested using histopathologic, immunohistochemical, immunoblot, or prion protein gene analyses. MAIN OUTCOME MEASURES: Presence or absence of established CJD risk factors, deer and elk hunting in CWD-endemic areas, and comparison of the evidence for the 3 patients with that of a zoonotic link between new variant CJD and bovine spongiform encephalopathy. RESULTS: None of the patients had established CJD risk factors or a history of travel to Europe. Two patients hunted game animals and 1 was a daughter of a hunter. Unlike patients with new variant CJD, the 3 patients did not have a unique neuropathologic manifestation, clinicopathologic homogeneity, uniformity in the codon 129 of the prion protein gene, or prion characteristics different from those of classic variants. CONCLUSIONS: Although the occurrence of 3 unusually young patients with CJD who consumed venison suggested a possible relationship with CWD, our follow-up investigation found no strong evidence for a causal link. Ongoing CJD surveillance remains important for continuing to assess the risk, if any, of CWD transmission to humans.

A comparison between argon laser and microsuture anastomosis of the rat uterine horn.

For assessment of the use of the argon laser for tubal anastomosis, the uterine horns of 12 Sprague-Dawley rats were surgically divided and then anastomosed, 6 by argon laser photocoagulation and 6 by the conventional technique of microsurgery. After a 4- to 6-week postsurgical period subjects were reexamined. All microsutured anastomoses were fully patent and continuous, with no apparent fibrosis. Four of six laser subjects had complete occlusion; the other two exhibited patencies between 10% and 20% of normal luminal area. Although initially producing satisfactory union, argon laser photocoagulation proved highly tissue traumatic, resulting in poor regeneration of the anastomotic site.

Position-linked interference in forming simple visual groups.

Experiments with 2-element visual groups reveal a form of interference that has several interesting properties. Observers judged the orientation of an imaginary line formed by 2 pixels (the target) while attempting to ignore a third pixel (the noise). Noise interfered with performance, even when it was made distinct from the target in various ways. This interference was strongly position linked; a single equation described the interference pattern for many different target-noise configurations. Maximum interference was observed not when the noise was closest to the target but when it was at a distance of half the separation between target pixels. Some initial findings were consistent with the idea that visual grouping reflects the operation of visual channels with Gabor-like receptive-field profiles. But subsequent results implicated processes that automatically construct visual boundaries.

Preattentive equivalence of multicomponent Gabor textures in the central and peripheral visual field.

Similarity ratings were obtained to determine the minimum number of Gabor components that would produce a comparison texture that appeared preattentively similar to a 64-component standard texture. All textures were chosen to be both specifiable by a relatively small number of localized spectral components and sufficiently complex to approximate natural textures. The number of component orientations in the set of comparison textures was found to be a particularly important determinant of texture discrimination in that its effect on rated similarity was largely independent of the total number of components making up the texture. Textures were also presented at 0.75 degree and 20 degrees eccentricity, with the latter magnified by a factor of either 2 or 4. The overall similarity rating did not change with either magnification, whereas the critical number of orientations, defined as the number of orientations above which rated similarity was constant, did change for the higher magnification. The latter finding is consistent with the proposition that higher-order discriminations are mediated by higher cortical areas that integrate information across the visual field. Finally, the phase-bandwidth of a set of coherent textures was also varied in order to determine whether more explicit differences in the spatial structure of stimuli might affect rated similarity. In contrast to the results for component orientation, the ratings, obtained at 0.75 degree and 20 degrees, were different even when the phase-bandwidth stimuli were magnified by a factor of 4.

Large and rapid improvement in form discrimination accuracy following a location precue.

Processing of a visual stimulus can be improved by precuing its location. Most previous precue studies have used reaction time as the dependent measure and have found large effects; but when form discrimination accuracy has been used, precue effects have been relatively small. The present experiments yielded large, short-latency precue effects on form discrimination accuracy. A small square precue was briefly presented near one of four possible target locations. Then one of four possible targets (T-like figures) was presented in each location, followed by a mask. Observers attempted to identify the target that had been presented in the cued location. In experiment 1, target duration, cue-to-target distance, and cue-target onset asynchrony (SOA) were varied. Target discriminability (d') increased markedly with increasing precue-target SOA, even at very short SOAs. Thus, there was no evidence for a delay in the onset of precue effects (caused, for example, by the need to shift attention across the visual field). Performance was best for precues that were closest to the target, thus ruling out a forward masking explanation of the effect. Finally SOA and target duration interacted strongly - longer precue SOAs resulted in larger effects of target duration. In experiment 2, this interaction was replicated using an additional target duration and longer SOAs. One interpretation of this result is that focal attention increases the rate at which information can be extracted from a visual location.

Importance of precue location in directing attention.

In location-precuing experiments, accuracy in discrimination of T-like characters improves with increasing time between the precue and the target. In this experiment, two central and two peripheral cue locations were examined using 13 different cue-target intervals from 0 to 234 msec. Accuracy was the same when trials were cued from the two peripheral locations (two thirds distance between fixation and target or distal to the target location). Centrally cued trials (cues at fixation or next to fixation) resulted in slower onset of attentional effects than peripherally cued trials, but there was greater accuracy at long cue-target intervals for central than for peripheral cues. Data are compared to previously published research.

Benefits from attention depend on the target type in location-precued discrimination.

In previous research, we found that precuing of attention to a target location greatly improved discrimination of targets that differed in line arrangement, but had little effect on discrimination of targets that differed in line orientation. In the present research, a number of other targets that represent various feature differences were used. The new data are consistent with and extend our earlier findings by showing that (1) there is some effect of precuing with all targets tested, and (2) the size of precuing effects varies in a complex way with the nature of the target. Moreover, the difficulty of the discrimination cannot explain the size of the precuing effects. A framework for understanding the events occurring during trials in the location-cuing paradigm is presented and applied to these results.

Time course of visual extrapolation accuracy.

In two experiments, we examined the extrapolation of a constant-velocity motion along a fixed circular path in the frontal plane. A target moved over an arc of 90 deg and then disappeared. Observers were to assume that the motion continued at the original velocity. After a variable time, a line appeared at another point on the circle to mark the end of the (invisible) 'motion'. Observers decided whether or not the target would have passed this end line, and gave a pass/no-pass response. In Experiment 1, a time course was established for the observed loss in accuracy with increasing duration of invisible motion. Two models of accuracy loss were constructed and tested. Both models assume that (1) extrapolation is performed by 'tracking' the position of the hidden target, and (2) there is no systematic velocity error in tracking, only random variation in tracker velocity. Both models predicted changes in hit and false alarm rates well, except in a condition where response asymmetries were present. In Experiment 2, the hypothesis that observers were tracking the hidden target was assessed by presenting a moving distractor during part of the trial. The presence of the distractor reduced performance under some conditions, suggesting that target tracking was occasionally disrupted. Grossly unequal distributions of pass/no-pass responses were observed for the fastest (8 deg/sec) and slowest (4 deg/sec) target velocities. However, the variable tracker models, using the parameter values from the first experiment, made accurate predictions for the 6 deg/sec condition, in which response distribution was nearly equal. Thus, there may be no need to posit systematic velocity error in motion tracking during extrapolation. The time course of accuracy decline can be accounted for by random variation in tracker velocity when response bias is absent.

Allocation of attention in texture segregation, visual search, and location-precuing paradigms.

Is there a common mechanism (or set of mechanisms) that controls the allocation of spatial attention in texture segregation, visual search, and location-precuing tasks? This question was addressed by comparing data from a new set of experiments on texture segregation, in which a common set of stimuli was used across the three paradigms. However, when we ranked the scores for the targets on texture segregation speed, search rate, and improvement due to precuing effects, agreement between these measures was less than perfect. Further analyses of these results led to the following conclusions: (a) speed of texture segregation is affected by perceptual aspects of the display other than the attentional salience of a particular target; (b) visual search rate and the size of precuing effects are strongly related over most of the set of targets we used; and (c) some cases in which search rate was not consistent with size of precue effects may be related to the presence of nearby distractors in the search task.

Central and peripheral precuing of forced-choice discrimination.

There are suggestions in the literature that spatial precuing of attention with peripheral and central cues may be mediated by different mechanisms. To investigate this issue, data from two previous papers were reanalysed to investigate the complete time course of precuing target location with either: (1) a peripheral cue that may draw attention reflexively, or (2) a central, symbolic cue that may require attention to be directed voluntarily. This analysis led to predictions that were tested in another experiment. The main result of this experiment was that a peripheral cue produced its largest effects on discrimination performance within 100 msec, whereas a central cue required approximately 300 msec to achieve maximum effects. In conjunction with previous findings, the present evidence for time differences between the two cuing conditions suggests that more than one process is involved in the spatial precuing of attention.

Attention in visual search: multiple search classes.

Data from visual-search tasks are typically interpreted to mean that searching for targets defined by feature differences does not require attention and thus can be performed in parallel, whereas searching for other targets requires serial allocation of attention. The question addressed here was whether a parallel-serial dichotomy would be obtained if data were collected using a variety of targets representing each of several kinds of defining features. Data analyses included several computations in addition to search rate: (1) target-absent to target-present slope ratios; (2) two separate data transformations to control for errors; (3) minimum reaction time; and (4) slopes of standard deviation as a function of set size. Some targets showed strongly parallel or strongly serial search, but there was evidence for several intermediate search classes. Sometimes, for a given target-distractor pair, the results depended strongly on which character was the target and which was the distractor. Implications from theories of visual search are discussed.

Does attention have different effects on line orientation and line arrangement discrimination?

Visual search and texture segregation studies have led to the inference that stimuli differing in the orientation of their component line segments can be distinguished without focal attention, whereas stimuli that differ only in the arrangement of line segments cannot. In most of this research, the locus of attention has not been explicitly manipulated. In the first experiment presented here, attention was directed to a relevant peripheral target by a cue presented near the target location or at the fovea. Effects of attention on orientation discrimination were assessed in a two-alternative forced-choice task with targets that were either: (1) lines that slanted obliquely to the right or left, or were horizontal or vertical, or (2) Y-like targets that had a short arm leading obliquely right or left of a vertical line. In some groups, a four-alternative forced-choice test with lines at 0 degree, 45 degrees, 90 degrees, and 135 degrees orientations was used. Discrimination of these targets (i.e. targets that differ in the orientation of component line segments) was only minimally facilitated as the time between the onset of the valid cue and the onset of the target (cue-target stimulus onset asynchrony, SOA) was increased from 0 or 17 msec to 267 msec. In contrast, discrimination of targets that did not differ in the orientation of component line segments but differed in line arrangement (T-like characters), was greatly facilitated by longer cue-target SOAs. In Experiment 2, a cue misdirected attention on 20% of the trials. A decrement occurred on incorrectly cued trials in comparison to correctly cued trials for both types of stimuli used (lines and Ts). The results from these experiments suggest that discrimination of line orientation benefits less from focal attention than does discrimination of line arrangement, but that both discriminations suffer when attention must be disengaged from an irrelevant spatial location.

The impact of graphic photographic evidence on mock jurors' decisions in a murder trial: probative or prejudicial?

Although courts in the United States and Canada regularly admit graphic photographs into evidence, little research exists on whether such evidence prejudices the decisions of jurors. Mock jurors (N = 120) read a detailed trial transcript of a murder trial, and were either presented with color, black and white, or no photographs of an actual murder victim. The proportion of guilty verdicts in the color and the black and white photograph conditions was approximately double that in the control condition. Both groups were more likely than the control condition to report emotional distress and physical reactions in response to viewing the photographs. By contrast, there were few differences between groups concerning the extent to which participants felt that the photographs influenced verdicts. Participants in all conditions equally felt that they had acted fairly. Implications surrounding the admissibility of graphic photographic evidence, and the seeming inability of participants to recognize that their judgments were biased, are discussed.

Cyclic AMP content of gingival fluid in women taking oral contraceptives.

Gingival fluid samples were collected from 12 healthy adult women who ranged in age from 19 to 34 years. Seven subjects with normal menstrual cycles who received no medications acted as controls while five subjects who had been using oral contraceptives for a minimum of 17 months constituted the experimental group. The women using birth control pills showed a 53% increase in the gingival fluid volume versus the controls. Radioimmunoassay revealed a mean concentration of cyclic adenosine monophosphate (cAMP) in the gingival fluid of 3.8-10(-6)M in the controls and 1.9-10(-6)M in subjects using oral contraceptives, although the total amount of cAMP present in the fluid from both groups was equal. These gingival fluid cAMP levels were a hundredfold higher than those measured in serum and saliva.

PIP: Dental literature showing that ovarian hormones and oral contraceptives (OCs) can alter the physiologic state of gingival tissues has led to an investigation in which gingival fluid samples were collected from 12 healthy adult women ranging in age from 19 to 34 years. 5 subjects who had been using OCs for at least 17 months constituted the experimental group while 7 received no OCs and formed the control group. Those using OCs exhibited a 53% increase in gingival fluid volume vs. the controls. Radioimmunoassay revealed a mean concentration of cyclic adenosine monophosphate (cAMP) in the gingival f luid of 3.8-10-6M in the controls and 1.9-10-6M in the subjects using OCs although the total amount of cAMP present in the fluid from both groups was the same. These gingival fluid cAMP levels were 100 times higher than those measured in serum and saliva. An association between the amount of cAMP found in the gingival fluid and the duration of OC use has been apparently absent.