Semantic interference on a phonological task in illiterate subjects

Previous research suggests that learning an alphabetic written language influences aspects of the auditory-verbal language system. In this study, we examined whether literacy influences the notion of words as phonological units independent of lexical semantics in literate and illiterate subjects. Subjects had to decide which item in a word- or pseudoword pair was phonologically longest. By manipulating the relationship between referent size and phonological length in three word conditions (congruent, neutral, and incongruent) we could examine to what extent subjects focused on form rather than meaning of the stimulus material. Moreover, the pseudoword condition allowed us to examine global phonological awareness independent of lexical semantics. The results showed that literate performed significantly better than illiterate subjects in the neutral and incongruent word conditions as well as in the pseudoword condition. The illiterate group performed least well in the incongruent condition and significantly better in the pseudoword condition compared to the neutral and incongruent word conditions and suggest that performance on phonological word length comparisons is dependent on literacy. In addition, the results show that the illiterate participants are able to perceive and process phonological length, albeit less well than the literate subjects, when no semantic interference is present. In conclusion, the present results confirm and extend the finding that illiterate subjects are biased towards semantic-conceptual-pragmatic types of cognitive processing.     

Keeping it short: a comparison of methods for brief picture presentation

Abstract— Research has shown that backward masking is a powerful tool for studying unconscious mental processes. Whereas studies have traditionally presented stimuli using cathode-ray tube (CRT) monitors or mechanical shutters together with slide projectors, recent studies (mainly in functional magnetic resonance imaging, fMRI) have begun to use methods based on liquid crystal displays (LCDs) and thin-film transistor (TFT) technology. However, because of differences in technology, all methods may not be equally suited for masking. When methods were compared for their accuracy in presenting pictures at short durations, LCD and TFT presentations had poor accuracy, but shutter and CRT presentations had better accuracy. Because CRTs interfere with the imaging process in fMRI, we recommend the use of mechanical shutters. However, our results may not generally apply to all displays, so we advise researchers to validate the presentation parameters of their displays. The procedure described here may be useful for that purpose.     

Fear and the amygdala: manipulation of awareness generates differential cerebral responses to phobic and fear-relevant (but nonfeared) stimuli

Rapid response to danger holds an evolutionary advantage. In this positron emission tomography study, phobics were exposed to masked visual stimuli with timings that either allowed awareness or not of either phobic, fear-relevant (e.g., spiders to snake phobics), or neutral images. When the timing did not permit awareness, the amygdala responded to both phobic and fear-relevant stimuli. With time for more elaborate processing, phobic stimuli resulted in an addition of an affective processing network to the amygdala activity, whereas no activity was found in response to fear-relevant stimuli. Also, right prefrontal areas appeared deactivated, comparing aware phobic and fear-relevant conditions. Thus, a shift from top-down control to an affectively driven system optimized for speed was observed in phobic relative to fear-relevant aware processing.     

Learning related modulation of functional retrieval networks in man

The medial temporal lobe has been implicated in studies of episodic memory tasks involving spatio-temporal context and object-location conjunctions. We have previously demonstrated that an increased level of practice in a free-recall task parallels a decrease in the functional activity of several brain regions, including the medial temporal lobe, the prefrontal, the anterior cingulate, the anterior insular, and the posterior parietal cortices, that in concert demonstrate a move from elaborate controlled processing towards a higher degree of automaticity. Here we report data from two experiments that extend these initial observations. We used a similar experimental approach but probed for effects of retrieval paradigms and stimulus material. In the first experiment we investigated practice related changes during recognition of object-location conjunctions and in the second during free-recall of pseudo-words. Learning in a neural network is a dynamic consequence of information processing and network plasticity. The present and previous PET results indicate that practice can induce a learning related functional restructuring of information processing. Different adaptive processes likely subserve the functional re-organisation observed. These may in part be related to different demands for attentional and working memory processing. It appears that the role(s) of the prefrontal cortex and the medial temporal lobe in memory retrieval are complex, perhaps reflecting several different interacting processes or cognitive components. We suggest that an integrative interactive perspective on the role of the prefrontal and medial temporal lobe is necessary for an understanding of the processing significance of these regions in learning and memory. It appears necessary to develop elaborated and explicit computational models for prefrontal and medial temporal functions in order to derive detailed empirical predictions, and in combination with an efficient use and development of functional neuroimaging approaches, to further the understanding of the processing significance of these regions in memory.     

Neuropsychological test norms controlled for physical health: Does it matter?

The objective of the present study was to investigate the effects of physical health on neuropsychological test norms. Medical and neuropsychological data from 118 healthy volunteer controls, aged 26–91 years, were collected during five recruitment occasions. The examinations included a clinical investigation, brain neuroimaging, and a comprehensive neuropsychological test battery. Test‐specific statistical regression‐weights for age, education and gender were calculated to establish preliminary test norms. Hierarchical regression analyses demonstrated that control in addition for physical health moved best performance from age 60 to 65 for abstraction; replaced a plateau above age 70 for verbal fluency, with a continued rise in performance; eliminated significant negative influences of age on auditory learning, spatial reasoning and complex copying; reduced them on wordlist recall, psychomotor speed, visual scanning and mental shifting; and slightly reduced negative influences of low education on most verbal tests, several memory tests, and psychomotor speed, indicating rises in normative scores of up to 0.8 SD at age 80 and 0.4 SD at age 60. No differences were found at age 40. Although the sample size is not adequate to be used for normative data, the findings indicate that norms uncontrolled for health overestimate the negative influence of advanced age and low education, implying a risk of drawing false diagnostic conclusions.     

Artificial syntactic violations activate Broca’s region

In the present study, using event-related functional magnetic resonance imaging, we investigated a group of participants on a grammaticality classification task after they had been exposed to well-formed consonant strings generated from an artificial regular grammar. We used an implicit acquisition paradigm in which the participants were exposed to positive examples. The objective of this study was to investigate whether brain regions related to language processing overlap with the brain regions activated by the grammaticality classification task used in the present study. Recent meta-analyses of functional neuroimaging studies indicate that syntactic processing is related to the left inferior frontal gyrus (Brodmann’s areas 44 and 45) or Broca’s region. In the present study, we observed that artificial grammaticality violations activated Broca’s region in all participants. This observation lends some support to the suggestions that artificial grammar learning represents a model for investigating aspects of language learning in infants [TICS 4 (2000) 178] and adults [Proceedings of the National Academy of Sciences of United States of America 99 (2002) 529].