Learning and production of movement sequences: behavioral, neurophysiological, and modeling perspectives

A wave of recent behavioral studies has generated a new wealth of parametric observations about serial order behavior. What was a trickle of neurophysiological studies has grown to a steady stream of probes of neural sites and mechanisms underlying sequential behavior. Moreover, simulation models of serial behavior generation have begun to open a channel to link cellular dynamics with cognitive and behavioral dynamics. Here we review major results from prominent sequence learning and performance tasks, namely immediate serial recall, typing, 2 x N, discrete sequence production, and serial reaction time. These tasks populate a continuum from higher to lower degrees of internal control of sequential organization and probe important contemporary issues such as the nature of working-memory representations for sequential behavior, and the development and role of chunks in hierarchical control. The main movement classes reviewed are speech and keypressing, both involving small amplitude movements amenable to parametric study. A synopsis of serial order models, vis-a-vis major empirical findings leads to a focus on competitive queuing (CQ) models. Recently, the many behavioral predictive successes of CQ models have been complemented by successful prediction of distinctively patterned electrophysiological recordings. In lateral prefrontal cortex, parallel activation dynamics of multiple neural ensembles strikingly matches the parallel dynamics predicted by CQ theory. An extended CQ simulation model--the N-STREAMS neural network model--exemplifies ongoing attempts to accommodate a broad range of both behavioral and neurobiological data within a CQ-consistent theory.     

An emerging postural response: is control of the hip possible in the newly walking child?

Previous researchers have proposed that because of their slow muscle-response latencies, 1- to 2-year-old children are unable to control hip-dominant postural responses when responding to balance threats (G. McCollum & T. Leen, 1989). To test that proposition, the authors exposed 41 children to backward support-surface translations and recorded muscle activations and movement kinematics. Children between 10 months and 10 years of age stood on a platform that was unexpectedly moved. Passive hip-dominant responses were observed among the least experienced walkers. In contrast, older children produced an active response, signified by higher levels of abdominal and quadriceps muscle activity and accompanied by larger hip flexor torques. Greater success in withstanding large magnitudes of perturbations were associated with actively generated hip responses.     

Psychological sequelae of remote exposure to the September 11th terrorist attacks in Canadians with and without panic

The purpose of the present investigation was to examine the psychological impact of remote exposure to the events and aftermath of the terrorist attacks in the USA on September 11th, 2001, and to assess what differences, if any, exist between individuals classified with probable panic disorder and those without. Telephone interviews were conducted with 122 residents of the capital city of the Canadian prairie province of Saskatchewan in spring 2002 in order to gather information regarding current mood, fears and avoidance behaviours as well as current post-traumatic stress disorder symptoms specific to September 11th. Consistent with previous findings and despite the remote nature of exposure, results indicated that the psychological well-being and behaviour of participants with probable panic disorder was more adversely affected by the events and aftermath of September 11th than those without panic disorder. These results suggest that remote viewing of traumatic events can have a significant and lingering impact on psychological well-being and behaviour and that these effects are more pronounced in those with panic disorder. Implications of the findings and future research directions are discussed.     

Analysis of precurrent skills in solving mathematics story problems

We conducted an analysis of precurrent skills (responses that increase the effectiveness of a subsequent or "current" behavior in obtaining a reinforcer) to facilitate the solution of arithmetic word (story) problems. Two students with developmental disabilities were taught four precurrent responses (identifying the initial value, change value, operation, and resulting value) in a sequential manner. Results of a multiple baseline design across behaviors showed that the teaching procedures were effective in increasing correct performance of each of the precurrent behaviors with untaught problems during probes and that once the precurrent behaviors were established, the number of correct problem solutions increased.     

The social risk hypothesis of depressed mood: evolutionary, psychosocial, and neurobiological perspectives

The authors hypothesize that depressed states evolved to minimize risk in social interactions in which individuals perceive that the ratio of their social value to others, and their social burden on others, is at a critically low level. When this ratio reaches a point where social value and social burden are approaching equivalence, the individual is in danger of exclusion from social contexts that, over the course of evolution, have been critical to fitness. Many features of depressed states can be understood in relation to mechanisms that reduce social risk in such circumstances, including (a) hyper-sensitivity to signals of social threat from others, (b) sending signals to others that reduce social risks, and (c) inhibiting risk-seeking (e.g., confident, acquisitive) behaviors. These features are discussed in terms of psychosocial and neurobiological research on depressive phenomena.     

Dodge-ing the issue: Dodge,Javal, Hering,and the measurement of saccades in eye-movement research

Dodge, in 1916, suggested that the French term 'saccade' should be used for describing the rapid movements of the eyes that occur while reading. Previously he had referred to these as type I movements. Javal had used the term 'saccade' in 1879, when describing experiments conducted in his laboratory by Lamare. Accordingly, Javal has been rightly credited with assigning the term to rapid eye movements. In English these rapid rotations had been called jerks, and they had been observed and measured before Lamare's studies of reading. Rapid sweeps of the eyes occur as one phase of nystagmus; they were observed by Wells in 1792 who used an afterimage technique, and they were illustrated by Crum Brown in 1878. Afterimages were used in nineteenth-century research on eye movements and eye position; they were also employed by Hering in 1879, to ascertain how the eyes moved during reading. In the previous year, Javal had employed afterimages in his investigations of reading, but this was to demonstrate that the eyes moved horizontally rather than vertically. Hering's and Lamare's auditory method established the discontinuous nature of eye movements during reading, and the photographic methods introduced by Dodge and others in the early twentieth century enabled their characteristics to be determined with greater accuracy.     

Molecular geneticists and moral responsibility: “maybe if we were working on the atom bomb I would have a different argument”

Senior molecular geneticists were interviewed about their perceptions of the ethical and social implications of genetic knowledge. Inductive analysis of these interviews identified a number of strategies through which the scientists negotiated their moral responsibilities as they participated in generating knowledge that presents difficult ethical questions. These strategies included: further analysis and application of scientific method; clarification of multiple roles; negotiation with the public through public debate, institutional processes of funding, ethics committees and legislation; and personal responsibility.     

What is bioethics without Christianity?

The author uses the essays in this issue as a springboard for making three points. First, he argues that most, if not all, current institutional versions of Christianity have failed to provide a meaningful framework for the spiritual life. Second, he argues that there is no ethics other than Judeo-Christian ethics and that there can be no bioethics other than Judeo-Christian bioethics. Finally, he argues that the overriding issue we face is not whether to address bioethical issues from a Christian perspective or from a non-Christian perspective, but rather whether we shall address biological and medical issues from an ethical or a scientific-technological perspective.