Individual differences in the functional neuroanatomy of verbal discrimination learning revealed by positron emission tomography

Why do some people have better memory abilities than others? This issue has been of long-standing interest to scientists and lay people. However, using purely behavioral methods, psychologists have made little progress in illuminating it. Now that functional brain imaging techniques have become available to study mind/brain relations, there is a new promise of understanding individual differences in learning and memory in terms of corresponding differences in brain activity. In this paper, we will present a positron emission tomography (PET) study designed to examine individual differences in learning and memory abilities. The basic assumption is that different patterns of brain activity serve as strong predictors of memory performance. Two specific questions were addressed in this study: (i) Can PET illuminate the relations between memory processes and their neuroanatomical correlates among individual learners and rememberers? and (ii) if so, how are these relations affected by the stage of practice on a given memory task? Our PET study examined individual differences in the neuroanatomical correlates of multi-trial verbal discrimination learning in 16 young healthy subjects. The results identified patterns of brain regions in which blood flow correlated with subjects' retrieval performance. However, these regions did not correlate with performance during all learning trials. Instead, a gradual shift was observed from one pattern of brain regions to another over the course of learning. These results suggest that individual differences in memory performance are related to differences in neural activity within specific brain circuits.     

Dyslexia: the articulatory hypothesis revisited

Articulatory disorders have been associated with developmental phonological dyslexia in the literature. However, very few information is available about the articulatory movements involved in speech production in dyslexic children. This study uses aerodynamic/acoustic data to explore how dyslexic children produce bilabial stops in French (/b, p/) within a sentence where they occurred in two positions and in three vowel environments. Average durations of articulatory closure and release were calculated in 10 phonological dyslexic children and two groups of age-matched and reading age-matched controls. Moreover, deviation from a standard pronunciation of the same material was evaluated separately by blind examiners. Our results reveal differences in the timing of the articulatory movements between dyslexics and normal controls, as well as more deviations from the target consonant for the dyslexics than for the controls. These observations are consistent with recent findings pointing to a general deficit in fine motor control in dyslexia.     

The "temporal processing deficit" hypothesis in dyslexia: new experimental evidence

The notion that developmental dyslexia may result from a general, nonspecific, defect in perceiving rapidly changing auditory signals is a current subject of debate (so-called "temporal processing deficit" hypothesis). Thirteen phonological dyslexics (age 10-13 years) and 10 controls matched for chronological and reading age were compared on a temporal order judgment (TOJ) task using the succession of two consonants (/p/-/s/) within a cluster. In order to test the relevance of the temporal deficit hypothesis, the task also included two additional conditions where either the two stimuli were artificially slowed or the interstimulus interval was expanded. As expected, the TOJ performance was significantly poorer in dyslexics than in controls. Moreover, in the "slowed speech" condition dyslexics' performance improved to reach the normal controls' level, whereas no significant improvement occurred when increasing the interstimulus interval. Finally dyslexics' performances, especially on the slowed condition, were found correlated with several tests of phonological processing (phoneme deletion, rhyme judgment, and nonword spelling tasks). These results lend support to the general temporal deficit theory of dyslexia.     

Health and Subjective Wellbeing in Algeria: A Developing Country in Transition

This paper explores the effects of health on wellbeing in a sample of 2,909 Algerians who participated in a survey using the Personal Wellbeing Index in 2005. The survey took place 3 years after the end of a violent civil war and the start of an economic recovery based on oil and gas. Survey participants were divided into two groups on the basis of their yes/no responses to a question about the existence of a chronic health condition. Their scores were then compared for the Personal Wellbeing Index, objective self-report health questions, and additional items relating to culture, environment and social networks. Correlational analyses and regressions were conducted to explore the relationship between health status, measures of health, and subjective wellbeing. Significant differences are found between the two groups in feelings of pain, anxiety and level of normal sleep, which further validate the comparison. The results show a marginal difference in Personal Wellbeing Index score in favour of the healthier group, due principally to the effect of the Health Domain. Moreover, the healthier group showed significantly higher satisfaction with marriage, friendship and family relationships, which raises the question of the direction of causation between the state of health and social relationships. Findings are discussed in relation to health provision in Algeria and previous SWB research.     

Age and Gender Differences in the Use of Various Poisoning Methods for Deliberate Parasuicide Cases Admitted to Loghman Hospital in Tehran (2000–2004)

Different methods of poisoning used by individuals with the diagnosis of parasuicide admitted to the Loghman Hospital, Tehran, from 2000 to 2004 were investigated, with particular focus on gender and age differences. Drugs, pesticides, and other agricultural chemicals (women: 12.7%, men: 9%) were the most commonly used methods. In males, the percentage of use of drugs increased with age, but the frequency of pesticides use decreased with age. In females, drugs were most often used in the youngest age group, whereas the use of pesticides was lowest in the youngest age category. Females outnumbered males, especially in the youngest age group of 10 to 19 years olds. Drugs and pesticides were the substances used most often for parasuicide in each age group regardless of gender.     

Functional connectivity changes in second language vocabulary learning

Functional connectivity changes in the language network (Price, 2010), and in a control network involved in second language (L2) processing (Abutalebi & Green, 2007) were examined in a group of Persian (L1) speakers learning French (L2) words. Measures of network integration that characterize the global integrative state of a network (Marrelec, Bellec et al., 2008) were gathered, in the shallow and consolidation phases of L2 vocabulary learning. Functional connectivity remained unchanged across learning phases for L1, whereas total, between- and within-network integration levels decreased as proficiency for L2 increased.The results of this study provide the first functional connectivity evidence regarding the dynamic role of the language processing and cognitive control networks in L2 learning (Abutalebi et al., 2005, Altarriba and Heredia, 2008, Leonard et al., 2011, Parker-Jones et al., 2011). Thus, increased proficiency results in a higher degree of automaticity and lower cognitive effort (Segalowitz & Hulstijn, 2005).     

Electrical properties of thin films of a-Ga x Te100− x composed of nanoparticles

Thin films of Ga _x Te_{100? x} (x?=?3, 6, 9 and 12) have been synthesized by thermal evaporation. From SEM images, it is observed that all the films contain nanoparticles of sizes varying from 100 to 200?nm. The dc electrical conductivity of the as-deposited films of Ga _x Te_100?x nanoparticles is measured as a function of temperature range from 298 to 383?K, and increases exponentially with temperature. The value of the activation energy, calculated from the slope of ln?σ _dc versus 1000/T plots, is found to decrease with increase in the Ga content. On the basis of the value of the pre-exponential factor σ _o, it is suggested that the conduction is due to thermally assisted tunneling of carriers in localized states near the band edges. The optical measurements suggest an indirect optical band gap in this system. The value of the optical band gap decreases on increasing the Ga concentration.     

Intensive training of phonological skills in progressive aphasia: a model of brain plasticity in neurodegenerative disease

Three patients with a typical syndrome of nonfluent primary progressive aphasia (Mesulam's syndrome) were trained daily with a remediation protocol including auditory exercises specifically designed to involve several aspects of phonological processing, a domain known to be specifically affected in the condition. The speech content of the exercises was based on the temporal theory of phonological processes according to which increasing the duration of formant transition should facilitate phoneme discrimination and phoneomic awareness. Significantly improved performance on the trained tasks was demonstrated in the three patients. Improvement further generalized to other tasks such as nonword repetition and reading. We conclude that such results (1) argue for using intensive focused therapy of language impairment in neurodegenerative disorders, (2) may constitute a good model of brain plasticity in neurodegenerative disorders in general, and (3) support theories of phonological processing emphasizing temporal features of the auditory signal.     

On the relation between conceptual priming, neural priming, and novelty assessment

A consistently reported finding in functional neuroimaging studies which compare processing of new information to processing of old information is a reduction in blood flow, and hence neural activity, associated with the old condition. This deactivation has been labeled neural priming. Some investigators have hypothesized that neural priming is the physiological mechanism underlying conceptual priming—a facilitation in the semantic processing of repeated information. Others, however, have hypothesized that neural priming reflects novelty assessment—a mechanism which minimizes the probability that redundant information will be stored in long‐term memory. In this paper, the conceptual priming and novelty assessment hypotheses are compared and contrasted in order to ask, and tentatively answer, the question: Are conceptual priming and novelty assessment cognitively and neurophysiologically distinct? Based on a review of the literature, it is suggested that whereas novelty assessment and conceptual priming are distinct cognitive entities, they cannot be presently separated neurophysiologically. That is, some novelty assessment deactivations may in fact reflect priming, and some priming deactivations may in fact reflect novelty assessment.