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Biomedical subjects

W A Richards

Publications and source records attributed to W A Richards.

17 recordsLinked to original sources
PubMed2006

Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance.

RATIONALE: Although psilocybin has been used for centuries for religious purposes, little is known scientifically about its acute and persisting effects. OBJECTIVES: This double-blind study evaluated the acute and longer-term psychological effects of a high dose of psilocybin relative to a comparison compound administered under comfortable, supportive conditions. MATERIALS AND METHODS: The participants were hallucinogen-naïve adults reporting regular participation in religious or spiritual activities. Two or three sessions were conducted at 2-month intervals. Thirty volunteers received orally administered psilocybin (30 mg/70 kg) and methylphenidate hydrochloride (40 mg/70 kg) in counterbalanced order. To obscure the study design, six additional volunteers received methylphenidate in the first two sessions and unblinded psilocybin in a third session. The 8-h sessions were conducted individually. Volunteers were encouraged to close their eyes and direct their attention inward. Study monitors rated volunteers' behavior during sessions. Volunteers completed questionnaires assessing drug effects and mystical experience immediately after and 2 months after sessions. Community observers rated changes in the volunteer's attitudes and behavior. RESULTS: Psilocybin produced a range of acute perceptual changes, subjective experiences, and labile moods including anxiety. Psilocybin also increased measures of mystical experience. At 2 months, the volunteers rated the psilocybin experience as having substantial personal meaning and spiritual significance and attributed to the experience sustained positive changes in attitudes and behavior consistent with changes rated by community observers. CONCLUSIONS: When administered under supportive conditions, psilocybin occasioned experiences similar to spontaneously occurring mystical experiences. The ability to occasion such experiences prospectively will allow rigorous scientific investigations of their causes and consequences.

Adult↗
PubMed1992

Curvature and separation discrimination at texture boundaries.

Visual discrimination of contour curvature was investigated by using contours defined by the locus of points at which the phase of a square-wave grating was shifted by 180 degrees (a texture boundary). Curvature-increment thresholds were measured for contour curvatures from 0.31 to 10.65 deg-1, for grating spatial frequencies of 4.0 and 16.0 cycles per degree (cpd), and for gratings in either sine or cosine phase at the point of maximum curvature. Thresholds for these conditions were compared with curvature discrimination at black-white edges. Grating phase had no effect on performance at any curvature or grating frequency, but 16.0-cpd gratings produced a threshold elevation at all curvatures by an average factor of 2.4. Two-line separation discrimination was also measured for lines defined by texture boundaries. These data can be predicted by a model incorporating end-stopped complex cells of a type reported physiologically in primate area V2.

Form Perception↗
PubMed1989

Mechanisms of contour curvature discrimination.

Visual processing of contour curvature was investigated by measuring increment thresholds for curvatures from 0.31 to 25.4 deg-1. Curvature discrimination was assessed for three classes of stimuli: simple curved contours, high-frequency bandpass-filtered contours, and low-pass-filtered contours. High-frequency bandpass filtering had no effect on discrimination at low curvatures and only a modest effect at high curvatures. In contrast, low-pass filtering caused substantial threshold elevations at all curvatures. Thus the data lead to the surprising conclusion that high-spatial-frequency, orientation-selective mechanisms dominate curvature processing over the entire range of curvatures tested, a conclusion at odds with previous suggestions that large, low-spatial-frequency filters are involved in analyzing low curvatures. The data are explained accurately by a two-process model for curvature extraction: at high curvatures the local-processing model proposed by Wilson [J. Opt. Soc. Am. A. 2, 1191 (1985)] fits the data well, whereas at low curvatures orientations are compared at points displaced a fixed distance along the tangent to the curve.

Biomechanical Phenomena↗
PubMed1988

Visual perception of moving parts.

There are countless three-dimensional interpretations of a set of points moving in a two-dimensional image. A unique visual interpretation of motion thus requires assumptions about the types of structure likely to be found in the three-dimensional world. We propose that the human visual system favors articulated structures in its interpretations. An articulated structure is a rigid body with moving parts that themselves are rigid and rotate in fixed planes with respect to the body. (A bicycle is an example.) We claim that an image consisting of just two moving points is seen as an articulated structure (when their motion is consistent with one), even though countless other interpretations are possible, including a rigid one of a rod moving in space. An experiment is presented in support of our claim, and a well-known display from an old experiment is reinterpreted as a special case of an articulated structure.

Humans↗
PubMed1982

Color vision and image intensities: when are changes material?

The difficulty in understanding a biological system or its components without some idea of its goals has been emphasized by Marr. In this paper, a preliminary goal for color vision is proposed and analyzed. That goal is to determine where changes of material occur in a scene (using only spectral information). The goal is challenging because the effects of many processes (shadowing, shading from surface orientation changes, highlights, variations in pigment density) are confounded with the effects of material changes in the available image intensities. We show there is a minimal and unique condition, the spectral crosspoint that rejects instances of these confounding processes. (If plots are made of image intensity versus wavelength from two image regions, and the plots intersect, we say that there is a spectral crosspoint.) An operator is designed to detect crosspoints; it turns out to resemble double-opponent cells described in primate visual cortex.

Color Perception↗
PubMed1982

Equation counting and the interpretation of sensory data.

Many problems in biological information processing require the solution to a complex system of equations in many unknown variables. An equation-counting procedure is described for determining whether such a system of equations will indeed have a unique solution, and under what conditions the solution should be interpreted as 'correct'. Three examples of the procedure are given for illustration, one from auditory signal processing and two from vision.

Animals↗
PubMed1976

MDA-assisted psychotherapy with neurotic outpatients: a pilot study.

Ten neurotic patients (five males and five females) were treated over a period of 2 to 6 months (mean, 4.1) as outpatients. The study allowed for a maximum of 75 hours of psychotherapy (mean, 51.55 hours). During the course of treatment, two to four (mean, 3.5) administrations of MDA (3,4-methylenedioxyamphetamine) were employed as adjunctive aids in an effort to enhance the psychotherapeutic process. The mean duration of the drug sessions was 8 hours (range, 6 to 14 hours). The first administration of MDA took place when, in the therapist's judgment, sufficient rapport had been established with the patient. All patients received an initial dose of 75 mg of MDA; subsequent dosage was allowed to range up to 200 mg. On these occasions, the drug appeared to be well tolerated with no serious side effects or complications observed. Psychometric assessments were obtained pre- and post-treatment, employing the Minnesota Multiphasic Personality Inventory (MMPI), Wittenborn Psychiatric Rating Scales (WPRS), and Brief Psychiatric Rating Scale (BPRS). In addition, follow-up evaluations were obtained 6 months after the termination of therapy by the use of the MMPI, WPRS, BPRS, and a Social History Questionnaire (SHQ) which had also been administered before treatment was initiated. Clinically, the impression was obtained that psychotherapy and the adjunctive use of MDA appeared to facilitate improvement in these patients. This impression was substantiated by significant reductions in scores on the psychometric assessments measuring depression, anxiety, and obsessive-compulsive traits. The meaures evaluating the sense of well-being and self-actualization also were encouraging. Although some of the patients were not as responsive as others, there were no observations to suggest that the condition of any of these patients had become worse.

Adjustment Disorders↗
PubMedDate not supplied

Prepooled cryoprecipitate for treatment of hemophilia A.

Lyophilized factor VIII concentrates, because of their convenience, are the most commonly used products for providing antihemophilic factor to patients with hemophilia A. Heightened concerns about associated complications indicate that cryoprecipitate usage will increase in the immediate future. We present a protocol for making cryoprecipitate more usable by "prepooling" individual units of cryoprecipitate in an "open" system. Our experience indicates this approach is safe, effective and acceptable to patients, including those on home therapy programs.

Factor VIII↗