Parallel distributed processing and neuropsychology: A neural network model of Wisconsin card sorting and verbal fluency

Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.     

Multiple listing for organ transplantation: autonomy unbounded

Recently, debate about the distribution of scarce organs for transplantation has focused on whether patients should have the right to place themselves on waiting lists at several transplant centers, thereby gaining an advantage over other potential recipients. This article explores the social and ethical issues raised by multiple listing, contrasting policies adopted at the national level with those implemented in New York State. It concludes by examining the implications of the debate for broader questions about entitlement and access to health care.     

Universal health care, American style: a single fund approach to health care reform

With increasing momentum for health care reform, attention is shifting to finance reform that will provide for direct methods for controlling health care spending. This article outlines the two principal paths to direct cost control and outlines a national plan that retains our multiple sources of payment, yet also contains a powerful direct cost control technique: a single fund to finance all health care.     

Low-dimensional chaos maps learning in a model neuropil (olfactory bulb).

Quantification of a chaotic system can be made by calculating the correlation dimension (D2) of the data that the system generates (Packard et al., 1980). The D2 algorithm, however, requires stationarity of the generator, a feature that biological data rarely reflect (Mayer-Kress et al., 1988). So we developed the "point correlation dimension" (PD2), an algorithm that accurately tracks D2 in linked data of different dimensions (Carpeggiani et al., 1991). We now present a mathematical argument that, for stationary data, individual PD2s converge to D2 and we demonstrate that the algorithm rejects contributions made by bursts of noise. Data were obtained from the surface of the olfactory bulb of the conscious rabbit (64 electrodes, 640 Hz each, 1.3 sec epochs) before and after presentation of a novel or habituated odor. D2 could be calculated in only 1 of 10 novel-odor trials, whereas PD2 could be calculated in all. Both algorithms indicated that a novel odor evokes a spatially uniform dimensional increase. The PD2 uniquely exhibited the dimensional decreases that occur during inspiration and the gradients of mean dimension present during the nonstimulated control state. These control gradients remained unchanged without odor experience, but showed spatially specific PD2 increases following odor habituation. It is interpreted that, 1) the PD2 is sensitive, accurate, and appropriate for dimensional assessment of biological data, 2) that during analysis of unfamiliar information a single global process is transiently evoked in the neuropil, and 3) after experience multiple spatially specific processes tonically map the sites of learning.     

Extinction instead of incubation following classical aversive conditioning in dogs.

Two dogs received a single paired classical conditioning trial, with tone CS and 12 mA shock US. Both dogs then showed a conditioned blood pressure increase in response to the nonreinforced CS, which extinguished with additional nonreinforced presentations. The CR showed spontaneous recovery four days later, but reextinguished with additional nonreinforced presentations. The results were interpreted as not supporting Eysenck's theory of "incubation" following one-trial aversive conditioning.     

Marital satisfaction and family stress as predictors of classroom behaviors

The purpose of this research was to examine the relationship between parents' perceptions of marital satisfaction and family stress and their third grade children's classroom behavior. Twenty-one married couples completed questionnaires during home visits. Behavior observations were made from videotapes of children recorded in their classroom during lunch and group academic periods on each of three days. Frequencies of peer interactions, solitary behaviors, and teacher interactions were coded. Regression analyses showed that mothers' level of marital satisfaction (but not fathers') predicted their children's frequency of peer interactions during lunch. Fathers' level of perceived family stress (but not mothers') predicted their children's frequency of peer interactions during lunch. Neither measure for either parent was related to the frequency of peer interactions, solitary behaviors, or teacher interactions observed during the academic sessions. These findings highlight the importance of assessing the potential differential relation of parent variables to children's trans-situational behaviors, and the examination of these variables in relation to different social-environmental contexts in which children participate outside the home.     

Three intensive community-based programs for children and youth with serious emotional disturbance and their families

Systems of care for children with serious emotional disturbance and their families have generally lacked intensive community-based programs. We describe three types of newly established community-based programs in New York State and present a general evaluation plan for determining which programs work for various children and their families. The three community-based programs are Intensive Case Management, Family-Based Treatment, and Family-Centered Intensive Case Management. Process and outcome evaluations are being conducted for each of these programs. These evaluations make use of common intake and termination instruments, based on a minimum data set, standardized assessment instruments, and a common logic model, thus facilitating the comparison of findings across evaluations.     

A tether system for cardiovascular studies with the behaving micropig

A tether system has been developed for continuous monitoring of blood pressure in the micropig. The micropig is a suitable model for blood-pressure research because of the similarity of its cardiovascular system to that of humans and because of its sensitivity to high sodium intake. The system consists of a metal boom, attached via a universal joint to a wall 6 ft above floor level, that extends horizontally to the center of the enclosure. A fluid and electronic swivel affixed to the boom is connected to a flexible, hollow, metal tether that descends to a vest worn by the micropig. The vest contains a pressure transducer to which an indwelling arterial catheter is connected via a stopcock. The transducer cable and an infusion line ascend through the interior of the tether to the swivel. The system remains in equilibrium through a system of pulleys and counterweights. Continuous, 24-h recording shows a diurnal variation characterized by higher heart rate but lower blood pressure during the day than at night. The system has been found to be effective for continuous studies over intervals of a month or more.