Environmental cue saliency influences the vividness of a remote spatial memory in rats

The Morris water maze is frequently used to evaluate the acquisition and retrieval of spatial memories. Few experiments, however, have investigated the effects of environmental cue saliency on the strength or persistence of such memories after a short vs. long post-acquisition interval. Using a Morris water maze, we therefore tested in rats the effect of the saliency of distal cues on the vividness of a recent (5 days) vs. remote (25 days) memory. Rats trained in a cue-enriched vs. a cue-impoverished context showed a better overall level of performance during acquisition. Furthermore, the probe trials revealed that the rats trained and tested in the cue-impoverished context (1) spent less time in the target quadrant at the 25-day delay, and (2) swam shorter distances in the target area, with fewer crossings at both 5- and 25-day delays, as compared to their counterparts trained and tested in the cue-enriched context. Thus, the memory trace formed in the cue-enriched context shows better resistance to time, suggesting an implication of cue saliency in the vividness of a spatial memory.     

Response times seen as decompression times in Boolean concept use

This paper reports a study of a multi-agent model of working memory (WM) in the context of Boolean concept learning. The model aims to assess the compressibility of information processed in WM. Concept complexity is described as a function of communication resources (i.e., the number of agents and the structure of communication between agents) required in WM to learn a target concept. This model has been successfully applied in measuring learning times for three-dimensional (3D) concepts (Mathy and Bradmetz in Curr Psychol Cognit 22(1):41-82, 2004). In this previous study, learning time was found to be a function of compression time. To assess the effect of decompression time, this paper presents an extended intra-conceptual study of response times for two- and 3D concepts. Response times are measured in recognition phases. The model explains why the time required to compress a sample of examples into a rule is directly linked to the time to decompress this rule when categorizing examples. Three experiments were conducted with 65, 49, and 84 undergraduate students who were given Boolean concept learning tasks in two and three dimensions (also called rule-based classification tasks). The results corroborate the metric of decompression given by the multi-agent model, especially when the model is parameterized following static serial processing of information. Also, this static serial model better fits the patterns of response times than an exemplar-based model.     

An information-based approach to action understanding

It has been proposed that the ability to make sense of other agents' behavior relies on the activation of internal mechanisms that map action perception onto action execution. In this study we explored the constraints on this ability introduced by eyeheight-scaled information in the optic array. Short and tall participants provided maximum overhead reaching judgments for themselves and another participant. Perceptual information was manipulated by changing the participants' optically specified eyeheight. Observers were modestly accurate in perceiving maximum overhead reach for themselves and for another actor whose action capabilities differed. Perceived maximum overhead reach increased for both self- and other-judgments when the perceiver's eyeheight was increased. The results suggest an important role of perceptual information that has gone unrecognized in existing accounts of action understanding and prediction.     

Motor asymmetry and substantia nigra volume are related to spatial delayed response performance in Parkinson disease

Studies suggest motor deficit asymmetry may help predict the pattern of cognitive impairment in individuals with Parkinson disease (PD). We tested this hypothesis using a highly validated and sensitive spatial memory task, spatial delayed response (SDR), and clinical and neuroimaging measures of PD asymmetry. We predicted SDR performance would be more impaired by PD-related changes in the right side of the brain than in the left. PD (n = 35) and control (n = 28) participants performed the SDR task. PD participants either had worse motor deficits on the right (RPD) or left (LPD) side of the body. Some participants also had magnetic resonance imaging for measurement of their substantia nigra (SN) volumes. The LPD group performed worse on the SDR task than the RPD and control groups. Right SN volume accounted for a unique and significant portion of the variance in SDR error, with smaller volume predicting poorer performance. In conclusion, left motor dysfunction and smaller right SN volume are associated with poorer spatial memory.     

Is there really a dissociative taxon on the dissociative experiences scale?

The Dissociative Experiences Scale (DES; Bernstein & Putnam, 1986) and MMPI (Hathaway & McKinley, 1940) were administered to 1,237 college students to evaluate MMPI differences for nonpathological (n = 90) or pathological dissociators (n = 111) and nondissociative controls (n = 476). MMPIs of both dissociation groups had multiple clinical elevations with a mean 8-9 code. People classified in the pathological dissociation group had MMPI scores remarkably similar to those in the normal dissociation group. The DES and DES-Taxon (DES-T; Waller, Putnam, & Carlson, 1996) were also highly correlated. Our findings strongly suggest the DES-T does not uniquely identify categorical dissociation.