Task instructions determine the visuospatial and verbal–spatial nature of number–space associations

Evidence for number–space associations comes from the spatial–numerical association of response codes (SNARC) effect, consisting in faster reaction times to small/large digits with the left/right hand, respectively. Two different proposals are commonly discussed concerning the cognitive origin of the SNARC effect: the visuospatial account and the verbal–spatial account. Recent studies have provided evidence for the relative dominance of verbal–spatial over visuospatial coding mechanisms, when both mechanisms were directly contrasted in a magnitude comparison task. However, in these studies, participants were potentially biased towards verbal–spatial number processing by task instructions based on verbal–spatial labels. To overcome this confound and to investigate whether verbal–spatial coding mechanisms are predominantly activated irrespective of task instructions, we completed the previously used paradigm by adding a spatial instruction condition. In line with earlier findings, we could confirm the predominance of verbal–spatial number coding under verbal task instructions. However, in the spatial instruction condition, both verbal–spatial and visuospatial mechanisms were activated to an equal extent. Hence, these findings clearly indicate that the cognitive origin of number–space associations does not always predominantly rely on verbal–spatial processing mechanisms, but that the spatial code associated with numbers is context dependent.     

The Corsi Block-Tapping Task: Methodological and Theoretical Considerations

The Corsi block-tapping task has enjoyed extensive use in clinical and experimental studies for a quarter of a century and is arguably the single most important nonverbal task in neuropsychological research. Nevertheless, there has been considerable inconsistency not only in the administration and scoring of this measure, but also in the physical properties of the test apparatus. In this paper, we survey a wide range of studies that have made use of the block-tapping task during the past 25 years and provide a detailed appraisal of the manifold methodological variations. Additionally, we discuss the historical context in which the Corsi originated and offer a critical examination of the cognitive processing operations purported to underlie performance on this task.     

Effects of Posttraining Intrahippocampal Injections of Platelet-Activating Factor and PAF Antagonists on Memory

The present experiments examined the effects of posttraining intrahippocampal injections of the degradative enzyme-resistant methylcarbamyl analog of the bioactive phospholipid platelet-activating factor (mc-PAF) and the platelet-activating factor (PAF) receptor antagonists BN52021 and BN 50730 on memory in male Long-Evans rats trained in a hidden platform version of the Morris water maze. Following an eight-trial training session, rats received a unilateral intrahippocampal injection of mc-PAF (0.5, 1.0, or 2.0 μg/0.5 μl), lyso-PAF (1.0 μg/0.5 μl), the cell surface PAF receptor antagonist BN 52021 (0.25, 0.5, or 1.0 μg/0.5 μl), the intracellular PAF receptor antagonist BN 50730 (2.0, 5.0, or 10.0 μg/0.5 μl), or vehicle (50% DMSO in 0.9% saline; 0.5 μl). On a retention test conducted 24 h after training, the escape latencies of rats administered mc-PAF (1.0 or 2.0 μg) were significantly lower than those of the vehicle-injected controls, demonstrating a memory-enhancing effect of mc-PAF. Injections of lyso-PAF, a structurally similar metabolite of PAF, had no influence on memory, indicating that the memory-enhancing effect of mc-PAF is not caused by membrane perturbation by the phospholipid. The retention test escape latencies of rats administered BN 52021 (0.5 μg) and BN 50730 (5.0 or 10 μg) were significantly higher than those of the controls, indicating a memory impairing effect of both PAF antagonists. When mc-PAF, BN 52021, or BN 50730 was administered 2 h posttraining, no effect on retention was observed, indicating a time-dependent effect of the neuroactive substances on memory storage. The findings suggest a role for endogenous PAF in hippocampal-dependent memory processes.     

Spatial Reversal as a Measure of Executive Functioning in Children With Autism

The purpose of this experiment was to compare the executive functioning performance of children with autism with chronological- and verbal-matched controls in a spatial-reversal task. Three groups of children participated in this experiment. One group was identified as having autism (7 boys), the 2nd group contained 7 typically developing children (6 boys, 1 girl) who were matched to the 1st group based on their verbal performance, and the 3rd group contained 7 typically functioning children (6 boys, 1 girl) matched to the 1st group based on chronological age. Each group was given a spatial-reversal task containing 2 problems. In the 1st problem, children selected a toy on a particular side in a pair. In the 2nd problem, the contingencies were reversed such that children were to choose the toy on the opposite side. Children with autism generally performed worse than comparison groups as indicated by their overall higher rate of errors. However, these results must be qualified by considering the performance for each problem: Errors for the children with autism were infrequent during the 1st problem but increased in the 2nd, whereas errors for comparison children showed the opposite pattern. When these results from the spatial-reversal task were intérpreted from the perspective of hypothesis-testing theory, the executive functioning deficiency of children with autism was found to involve the selection and testing of stereotypic response sets that were not likely to be revised or changed flexibly according to feedback from the environment or the demands of the task.     

内源性和外源性视觉空间选择注意

以内源性和外源性注意选择为主题,空间选择性注意的控制性加工和自动加工过程成为近年来研究的一个活跃领域,特别是自动化加工过程,取得了一些新的实验证据：对其形成的机制提出了一些理论;提出了选择注意自动化和控制之间关系的理论框架。本文介绍了有关的实验研究和理论模型。     

Afferent dysgraphia after right cerebral stroke: an autonomous syndrome?

Afferent dysgraphia is an acquired writing deficit characterized by deletions and duplications of letters and strokes. The commonly accepted interpretation states that afferent dysgraphia is associated with three main clinical features: production of spatial writing errors; the presence of left unilateral neglect; and no deterioration in performance when writing blindfolded. In order to test whether these symptoms necessarily co-occur with afferent dysgraphia, we studied the writing performances of a series of eight right brain-damaged patients. In sentence copying, spontaneous handwriting, and writing to dictation they showed afferent dysgraphia. However, signs of left neglect and spatial dysgraphia were evident only in some cases. Furthermore, the frequency of afferent errors increased when patients were required to write without vision. The present study demonstrates that afferent dysgraphia is an autonomous clinical entity and that it results from a selective impairment of a mechanism whose function is that of comparing the information about the number of letters and strokes specified at the level of letter motor programs and the actual number of movements already realized.     

A Proof System for Contact Relation Algebras

Contact relations have been studied in the context of qualitative geometry and physics since the early 1920s, and have recently received attention in qualitative spatial reasoning. In this paper, we present a sound and complete proof system in the style of Rasiowa and Sikorski (1963) for relation algebras generated by a contact relation.