Is the unilateral lesion of the left substantia nigra pars compacta sufficient to induce working memory impairment in rats?

Adult male Wistar rats with a substantia nigra pars compacta (SNc) lesion induced by intranigral administration of 1 micromol 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were used as a model of early phase Parkinson's disease (PD). This lesion caused a partial depletion of striatal dopamine (DA). The animals were submitted to a spatial working memory version of the water maze task in which they had to find a hidden (submersed) platform using online-maintained information that the platform remains in the same place during four consecutive trials, but that it is moved to another place every training day. Left, but not right SNc-lesioned rats were impaired in finding the platform in the second trial. This result suggests that the left SNc plays a key role in spatial working memory. Control experiments ruled out the possibility that motor impairment, sensory neglect, and/or impairment in the mental representation of the contralateral spatial environment had affected performance of the SNc-lesioned rats.     

Priming of non-speech vocalizations in male adults: the influence of the speaker's gender

Previous research reported a priming effect for voices. However, the type of information primed is still largely unknown. In this study, we examined the influence of speaker's gender and emotional category of the stimulus on priming of non-speech vocalizations in 10 male participants, who performed a gender identification task. We found a significant priming effect, which was greater for female than male vocalizations. In contrast, the emotional category of the stimuli did not appear to modulate the magnitude of priming. These data suggest that different aspects of the information conveyed in non-speech vocalizations may contribute differently to behavioral priming, possibly influenced by task relevance.     

How are social identities linked to self-conception and intergroup orientation? The moderating effect of implicit theories

Social identity approaches assume that social identification affects both self-conception and intergroup orientation. The authors contend that such social identification effects are accentuated when people hold a fixed view of human character and attribute immutable dispositions to social groups. To these individuals, social identities are immutable, concrete entities capable of guiding self-conception and intergroup orientation. Social identification effects are attenuated when people hold a malleable view of human character and thus do not view social identities as fixed, concrete entities. The authors tested and found support for this contention in three studies that were conducted in the context of the Hong Kong 1997 political transition, and discussed the findings in terms of their implications for self-conceptions and the meaning of social identification.     

On-line syntactic processing in aphasia: studies with auditory moving window presentation

Twenty-eight aphasic patients with left hemisphere strokes and matched control subjects were tested on an auditory moving windows task in which successive phrases of a sentence were presented in response to subjects' self-paced button presses and subjects made timed judgments regarding the plausibility of each sentence. Pairs of sentences were presented that differed in syntactic complexity. Patients made more errors and/or took longer in making the plausibility judgments than controls, and were more affected than controls by the syntactic complexity of a sentence in these judgments. Normal subjects showed effects of syntactic structure in self-paced listening. On-line syntactic effects differed in patients as a function of their comprehension level. High-performing patients showed the same effects as normal control subjects; low performing patients did not show the same effects of syntactic structure. On-line syntactic effects also differed in patients as a function of their clinical diagnosis. Broca's aphasic patients' on-line performances suggested that they were not processing complex syntactic structures on-line, while fluent aphasics' performances suggested that their comprehension impairment occurred after on-line processing was accomplished. The results indicate that many aphasic patients retain their ability to process syntactic structure on-line, and that different groups of patients with syntactic comprehension disorders show different patterns of on-line syntactic processing.     

On-line syntactic processing under concurrent memory load

Thirty-six university students were tested in a plausibility judgment task using a self-paced listening paradigm under no-interference and two-digit load conditions. Listening times were longer at syntactically more complex portions of syntactically more complex sentences, and greater loads led to increased listening times. However, listening times at syntactically more complex positions in syntactically more complex sentences did not increase more than listening times at comparable positions in syntactically simple sentences under digit load conditions. The results indicate that a concurrent memory load does not reduce the availability of working memory resources used for on-line syntactic processing and, thus, provide evidence that the working memory system used for assigning syntactic structure is separate from that measured by standard working memory tasks.     

Barking up the wrong tree? Industry funding of academic research. A case study with commentaries

This case raises ethical issues involving conflicts of interest arising from industrial funding of academic research; ethical responsibilities of laboratories to funding agencies; ethical responsibilities in the management of a research lab; ethical considerations in appropriate research design; communication in a research group; communication between advisor and graduate student; responsibilities of researchers for the environment; misrepresentation or withholding of scientific results.     

The reliability and stability of verbal working memory measures

The psychometric properties of several commonly used verbal working memory measures were assessed. One hundred thirty-nine individuals in five age groups (18–30, 50–59, 60–69, 70–79, and 80+ years) were tested twice (Time I and Time II) on seven working memory span measures (alphabet span, backward digit span, missing digit span, subtract 2 span, running item span, and sentence span for syntactically simple and complex sentences), with an interval of approximately 6 weeks between testing. There were significant effects of age on all but two of the tasks. All the measures had adequate internal consistency. Correlations between performances at Time I and Time II were significant for all the tasks, other than the missing digit span task. The magnitude of the correlations was similar across the age groups and ranged from .52 to .81. Classification of subjects into discrete memory span groups on the basis of a single measure was highly inconsistent across testing sessions and tasks. Classification into upper and lower quartiles was more stable than using a cutoff score for group membership or than classification into high-, medium-, and low-span groups. Correlational analyses showed that there was a moderate relationship between performances on many of the span tasks. Confirmatory factor analysis suggested that six of the seven tasks reflected a common factor. Both test—retest reliability and stability of classification improved when a composite measure reflecting performance on several tasks was used.     

Understanding the functional properties of tools: chimpanzees (Pan troglodytes) and capuchin monkeys (Cebus apella) attend to tool features differently

We examined whether eight capuchins and eight chimpanzees were able to retrieve a reward placed inside a tube, of varying length, by selecting the correct stick from different sets of three sticks differing in length (functional feature) and handle (non-functional feature). Moreover, to investigate whether seeing the stick inside the tube (visual feedback) improves performance, half of the subjects were tested with a transparent apparatus and the other half with an opaque apparatus. Phase 1 included (a) Training 1 in which each stick had a different handle and (b) Transfer 1 in which the handles were switched among sticks, so that the functional tool had the same length but a different handle than before. The seven chimpanzees and one capuchin that passed Transfer 1 received Transfer 2. The other subjects received (a) Training 2, which used the same sticks from Phase 1 with handles switched in every trial, and (b) Transfer 2 in which the tube was longer, all sticks had the same new handle, and the formerly longest tool became intermediate in length. Eight chimpanzees and three capuchins passed Transfer 2. Results showed that (1) chimpanzees applied relational structures in tool using tasks more quickly than capuchins and (2) capuchins required more varied experience to attend to the functional feature of the tool. Interestingly, visual feedback did not improve performance in either species.     

A right visual field advantage for visual processing of manipulable objects

Information about object-associated manipulations is lateralized to left parietal regions, while information about the visual form of tools is represented bilaterally in ventral occipito-temporal cortex. It is unknown how lateralization of motor-relevant information in left-hemisphere dorsal stream regions may affect the visual processing of manipulable objects. We used a lateralized masked priming paradigm to test for a right visual field (RVF) advantage in tool processing. Target stimuli were tools and animals, and briefly presented primes were identical to or scrambled versions of the targets. In Experiment 1, primes were presented either to the left or to the right of the centrally presented target, while in Experiment 2, primes were presented in one of eight locations arranged radially around the target. In both experiments, there was a RVF advantage in priming effects for tool but not for animal targets. Control experiments showed that participants were at chance for matching the identity of the lateralized primes in a picture?Cword matching experiment and also ruled out a general RVF speed-of-processing advantage for tool images. These results indicate that the overrepresentation of tool knowledge in the left hemisphere affects visual object recognition and suggests that interactions between the dorsal and ventral streams occurs during object categorization.     

Morphological patterns and their colour

This study analyzed qualitative aspects in perception, particularly the relationship between morphological aspects of biological shapes and colour. The experiment reported by the study assessed the functional relation between shape and colour and, in particular, the relations among the patterns of shapes appearing in perceptual configurations, as well as certain characteristics of colour. Participants were shown 32 natural images and were asked to match them with a colour. The results indicated that some figures were more frequently associated (positively or negatively) with some colours instead of others. Type of shape, texture, and three-dimensionality were important elements in the participants' choices. Rounded figures and non-holed figures had positive matches with red; elongated figures were associated with colours between blue and green; and holed figures showed positive matches with colours between green and yellow. Type of shape and texture also exhibited a relationship with the warmth of the colour.