Bidirectional plasticity in striatonigral synapses: a switch to balance direct and indirect basal ganglia pathways

There is no hypothesis to explain how direct and indirect basal ganglia (BG) pathways interact to reach a balance during the learning of motor procedures. Both pathways converge in the substantia nigra pars reticulata (SNr) carrying the result of striatal processing. Unfortunately, the mechanisms that regulate synaptic plasticity in striatonigral (direct pathway) synapses are not known. Here, we used electrophysiological techniques to describe dopamine D(1)-receptor-mediated facilitation in striatonigral synapses in the context of its interaction with glutamatergic inputs, probably coming from the subthalamic nucleus (STN) (indirect pathway) and describe a striatonigral cannabinoid-dependent long-term synaptic depression (LTD). It is shown that striatonigral afferents exhibit D(1)-receptor-mediated facilitation of synaptic transmission when NMDA receptors are inactive, a phenomenon that changes to cannabinoid-dependent LTD when NMDA receptors are active. This interaction makes SNr neurons become coincidence-detector switching ports: When inactive, NMDA receptors lead to a dopamine-dependent enhancement of direct pathway output, theoretically facilitating movement. When active, NMDA receptors result in LTD of the same synapses, thus decreasing movement. We propose that SNr neurons, working as logical gates, tune the motor system to establish a balance between both BG pathways, enabling the system to choose appropriate synergies for movement learning and postural support.     

Empirical underidentification in estimating random utility models: The role of choice sets and standardizations

A standard approach to distinguishing people’s risk preferences is to estimate a random utility model using a power utility function to characterize the preferences and a logit function to capture choice consistency. We demonstrate that with often-used choice situations, this model suffers from empirical underidentification, meaning that parameters cannot be estimated precisely. With simulations of estimation accuracy and Kullback–Leibler divergence measures we examined factors that potentially mitigate this problem. First, using a choice set that guarantees a switch in the utility order between two risky gambles in the range of plausible values leads to higher estimation accuracy than randomly created choice sets or the purpose-built choice sets common in the literature. Second, parameter estimates are regularly correlated, which contributes to empirical underidentification. Examining standardizations of the utility scale, we show that they mitigate this correlation and additionally improve the estimation accuracy for choice consistency. Yet, they can have detrimental effects on the estimation accuracy of risk preference. Finally, we also show how repeated versus distinct choice sets and an increase in observations affect estimation accuracy. Together, these results should help researchers make informed design choices to estimate parameters in the random utility model more precisely.     

ARIS: A computer-assisted instruction system

The automated real-time instructional system (ARIS) is a small computer-assisted instructional system written to run under the UNIX operating system on a PDP-11/34A machine. ARIS is a tool used to provide highly individualized instruction and, at the same time, to study the process of learning by keeping detailed records of students’ actions. Currently, the system is used to teach logic and set theory. This paper describes the general philosophy, operation, and implementation of ARIS.     

CAI: Goals and perspectives: Computer users’ group panel discussion

This report of the users’ group meeting contains a condensed version of a panel discussion of general issues involving computer-assisted instruction (CAI) systems. The discussants were asked to comment on the goals of the CAI efforts and the past accomplishments and future of computer systems in education.     

Arnošt Kolman: Portrait of a Marxist-Leninist philosopher

Kolman's philosophy has been, throughout the major part of his life, distinctly Stalinist. After he had been released from prison and after the 20th Congress of the Communist Party of the U.S.S.R. (1956), he became critical of Stalinist dogmatism in philosophy and politics. Although his philosophic thought underwent some — if only minor — changes, Kolman remained entirely within the framework of Marxist philosophy, retaining its foundations, as contained in the writings of the classics of Marxism — Marx, Engels and Lenin.     

Need-informational interaction of brain structures

The data presented deal with the role of four main brain structures in the development of emotional states and the organization of purposeful behavior. According to these data, the frontal neocortex orients behavior towards signals of highly probable events (reinforcement), whereas the hypothalamus is the basis for satisfaction of the dominant need. Unlike the neocortex, the hippocampus reacts to events of low probability, which is typical of emotionally stressed brain activity. Unlike the hypothalamus, the amygdala creates the balance, the dynamic coexistence, of competing needs (motivations) and emotions generated by such needs, which makes behavior more adequate. Individual characteristics of the interaction among the four brain structures is the basis for the individual types of higher nervous activity.     

Daniel Berlyne's contributions to empirical aesthetics

This article reviews the four types of evidence relevant to arousal as a determinant of aesthetic preference: (a) preference as related to arousal-producing attributes of objects, (b) preference changes through time as a function of such attributes, (c) preference as a function of the arousal level of the observer, and (d) perception of art objects as revealed by multidimensional scaling. Some evidence, but not all, underscores the importance of arousal, but the arousal framework rightly continues to inspire empirical work.This paper was presented at a symposium in honor of Daniel Berlyne, at the annual meeting of the American Psychological Association, August 27, 1977, in San Francisco.