Motor deficits in Parkinsonian reaching: dopa-sensitivity influenced by real-world task constraint

Parkinson's disease (PD) patients can perform many daily activities, but movement deficits are evident. Those deficits may be increased when the required movement is constrained in accuracy. Variable improvements in performance with PD medication have been demonstrated, and sensitivity to task constraint has been evident in some studies. The authors quantified both specific movement deficits and improvements for PD patients in a reaching task. PD patients (N=8) both on and off medication showed a need for greater ongoing control in movements with higher task-accuracy constraints. Increased task-accuracy constraints further compromised movement timing and structure among PD patients who were off medication, suggesting that unmedicated PD patients may typically compensate by using more conscious control of movement, resulting in increased slowing and segmentation of components when higher task accuracy is required.     

Effects of training intensity on observers' ratings of anxiety, social skills, and alcohol-specific coping skills

Few studies have addressed the amount of training needed to obtain reliable ratings in behavioral observation data. The current study examined the effects of differing intensities of frame-of-reference (FOR) rater training on observers' ratings of anxiety, social skills, and alcohol-specific coping skills in community volunteers with and without social anxiety and alcohol use disorders. Interrater reliability was assessed by comparing three training conditions (no-training, moderate FOR, and intensive FOR) on discrepancies between raters'scores and the strength of association between raters'scoring patterns. The discrepancies between raters' scores were significantly larger in the control condition than in the intensive and moderate training conditions. Generally, small and nonsignificant differences were found between intensive and moderate training's discrepancy scores. Strength of association results showed significantly lower correlations in the control group compared to the intensive group. However, these correlational results showed less consistent differences between the moderate and other training conditions; differences when found were in the expected directions. Study findings suggest that differing training intensities can affect rating scores and that interrater reliability may be meaningfully assessed through multiple methods.     

Movement characteristics support a role for dead reckoning in organizing exploratory behavior

Rat exploration is an organized series of trips. Each exploratory trip involves an outward tour from the refuge followed by a return to the refuge. A tour consists of a sequence of progressions with variable direction and speed concatenated by stops, whereas the return consists of a single direct progression. We have argued that processing self-movement information generated on the tour allows a rat to plot the return to the refuge. This claim has been supported by observing consistent differences between tour and return segments independent of ambient cue availability; however, this distinction was based on differences in movement characteristics derived from multiple progressions and stops on the tour and the single progression on the return. The present study examines movement characteristics of the tour and return progressions under novel-dark and light conditions. Three novel characteristics of progressions were identified: (1) linear speeds and path curvature of exploratory trips are negatively correlated, (2) tour progression maximum linear speed and temporal pacing varies as a function of travel distance, and (3) return progression movement characteristics are qualitatively different from tour progressions of comparable length. These observations support a role for dead reckoning in organizing exploratory behavior.     

Compensatory changes in striatal dopamine neurons following recovery from injury induced by 6-OHDA or methamphetamine: a review of evidence from microdialysis studies

This paper presents evidence from microdialysis experiments that three different behavioural outcomes of depletion of striatal dopamine (DA) by either 6-hydroxydopamine or methamphetamine (sparing of function, recovery of function, and loss of function) may be related to differences in the ability of residual DA neurons to maintain extracellular concentrations of DA. It is shown that when up to 80% of the mesostriatal DA system is destroyed, the remaining DA terminals maintain normal extracellular dopamine concentrations. Following a lesion in the 80-95% range, most animals maintain a relatively normal extracellular concentration of DA, but the ability to respond to increased demand is reduced in some animals. When over 95% of the normal DA input to the striatum is destroyed, there is a sharp drop in the extracellular concentration of DA and a nearly complete loss in the ability to increase DA release upon demand. Thus, this new method of sampling extracellular DA and its metabolites in freely moving animals provides insights into the behavioural capacities of animals and into the neural mechanisms that underlie recovery of function following brain damage.     

Goal Characteristics and Satisfaction: Personal Goals as Mediators of Situational Effects on Task Satisfaction1

This study modeled the process underlying the experience of satisfaction by examining the interrelationships among the task situation, intention characteristics, and satisfaction. The central proposition of the model was that the effect of the situation on satisfaction is fully mediated by the nature and status of one's own intentions that result from that context. The proposed model, in which the task situation indirectly determines satisfaction only through intention characteristics, was compared to a model in which the situation both directly and indirectly determines satisfaction and to a model which contained no intention characteristics. The intention characteristics assessed in this study included their number, valence, value, commitment, probability, and perceived attainment. Two aspects of the task situation were examined: task enrichment and assigned performance goals. A total of 192 subjects were randomly assigned to 1 of 4 conditions according to goal (no goal vs. assigned goal) and task type (enriched vs. unenriched). Intentions and their characteristics were assessed before the task period, and satisfaction with the task was measured afterward. The results provided support for a model in which the task situation and intention characteristics have independent effects on satisfaction.     

A neurobiological model for near-death experiences

The authors present a neurobiological model for near-death experiences (NDEs) in an attempt to correlate the biological and psychological domains. This model is based on temporal lobe dysfunction, hypoxia/ischemia, stress, and neuropeptide/neurotransmitter imbalance. They describe and discuss the fundamental contribution of the language system in the construction of verbal reports of NDEs. This model could be seen as a complement to other explanatory domains.