Lateral asymmetry in phonological processing: relating behavioral measures to neuroimaged structures

Recent neuroimaging studies have revealed neuroanatomical centers of activation that appear to be linked specifically to phonological processes. Furthermore, there is evidence that these centers of activation are more likely to be bilaterally represented in women than in men. However, behavioral evidence of such hemispheric asymmetries or of related sex differences is somewhat inconsistent. Two experiments were carried out to determine whether behavioral correlates of the neuroimaging findings could be demonstrated. The first experiment employed a rhyme-matching task used in a recent neuroimaging study, in which two nonsense words were projected successively to the left or right sides of the visual field. The results indicated that the left hemisphere was superior for this task. An analysis of gender effects, however, revealed that the asymmetry was restricted to men. The second experiment employed a lateralized pseudohomophone detection task that was designed to determine whether the results of the first experiment could be confirmed in the context of a phonological task with a simpler structure. This experiment broadly supported the findings of the first experiment. The results support the specialization of the left hemisphere for phonological processing, and the existence of gender differences with respect to these processes.     

A multisource exploration of the friendship patterns of children with and without learning disabilities

Friendship patterns of 117 children with learning disabilities (LD) and 115 children without LD in Grades 4–8 were examined. In comparison with children without LD, boys with LD had fewer mutual friends, children with LD had more friends with learning problems and more younger friends, and children with LD in Grades 4–6 had less stable relationships. With regard to friendship quality, children with LD reported higher levels of conflict, lower levels of validation, and more problems with relationship repair than did children without LD. The findings were discussed in terms of factors that have been found to enhance friendship such as proximity and similarity, and the social skills difficulties that have been associated with learning disabilities.     

Derivation by prefixation in Slovenian: two aphasia case studies

The present study is concerned with two Slovenian-speaking patients who were asked to produce, in various tasks, verbs, nouns, and adjectives derived by prefixation with prepositions. Despite differences due to their specific linguistic difficulties, both patients' performance was characterized by the differential processing of prefixes and remaining components of complex words. Prepositions in prefixation were mostly preserved, and less frequently substituted, regardless of the numerous errors produced in the remaining portion of the words. These errors seem clearly determined by the morphological structure of the words and therefore appear to be authentic morphological errors. These findings contribute to the theoretical debate on mental lexical representation, speaking in favor of a morphological decomposition in processing of prefixed complex words at different processing levels.     

Is phonological information mapped onto semantic information in a one-to-one manner?

Spoken word recognition models have to explain the influence of mismatching information on lexical activation. The effect of mismatching information is usually addressed with cross-modal semantic priming experiments using priming effects as a measure of the degree of lexical activation. Pseudowords phonologically related to a semantic associate of the target, e.g., *domato-PAPRIKA, serve as primes. Mismatch effects at the word form level are supposed to percolate unaltered to the semantic level. We show that cross-modal semantic priming might underestimate activation at the word form level. Targets (e.g., PAPRIKA) were preceded by either phonologically related pseudoword primes (e.g., *baprika) or semantically related pseudoword primes (e.g., *domato). Different priming and RT patterns were obtained for the two priming relations.     

Do orthographic cues aid language recognition? A laterality study with French-English bilinguals

Sixteen French-English late bilinguals performed a speeded language recognition task on lateralized words that were either marked or unmarked for language on the basis of digram frequency. Response latencies were faster to orthographically marked than unmarked words, particularly in the second language (English). Furthermore, L2 marked words were responded to faster than L1 marked words. These effects were especially prominent for words presented in the left visual field. It is suggested that subjects made use of different strategies in performing the task of language recognition task, with a perceptual search strategy deployed to identify orthographically marked words, resulting in an L2 advantage for such words, and a lexical search strategy deployed for unmarked words, resulting in an L1 advantage for such words.     

Prognostic relevance of quantitative topographical EEG in patients with poststroke aphasia

In this prospective study we analyzed the prognostic value of topographical quantitative EEG (qEEG) in poststroke aphasia. Twenty-three right-handed patients (ages 56 +/- 12 years) with different types of aphasia were studied. Quantitative EEG under resting conditions and an aphasia test battery were applied twice, 2 and 8 weeks after a stroke. EEG power fast Fourier transform was performed for delta (2-3.5 Hz), theta (4-7.5 Hz), alpha (8-13 Hz), and beta (13.5-20 Hz) frequency bands. EEG abnormalities within and outside speech relevant areas are related to restitution of poststroke aphasia. In the ischemic regions they indicate local disturbances; outside they reflect failures in neuronal networks involved in the generation and propagation of the alpha rhythm.     

Diurnal time courses in psychomotor performance and waking EEG frequencies

The present study examined the similarities between the diurnal time courses in the waking EEG activity and the psychomotor performance. The aim was to verify if some ongoing changes in the excitability of the cortical nerve cells across the daytime could facilitate the sensorimotor processing. EEG recordings and performance results for the Four Choice Reaction Time Test (FCRTT) were obtained every two hours, from morning to late evening period, in 8 young normal subjects (21.3 +/- 0.5 years). ANOVAs were used to verify the presence of diurnal variations in the two measures. Nonparametric correlations were obtained to test the similarity between the changes across the day in the two measures. Three EEG frequency bands (delta, sigma, and beta1) and the reaction time measures varied across the daytime. The changes in the sigma (12.00-13.75 Hz) and the beta1 (14.00-19.75 Hz) bands were similar to the diurnal variations in the reaction time measures. It is suggested that the changes in the sigma and the beta1 bands may facilitate the processing of the sensorimotor treatment.     

A simulation study of the degrees of freedom of movement in reaching and grasping

The question of independently controlled components in the act of reaching and grasping has attracted interest experimentally and theoretically. Data from 35 studies were recently found consistent with simulated kinematic finger and thumb trajectories optimised for minimum jerk. The present study closely reproduces those trajectories using a discrete-time model based on minimum acceleration. That model was further used to generate two-dimensional trajectories for finger and thumb to reach and grasp an elliptical object with varying position and/or orientation. Orthogonalisation of these four trajectories revealed one degree of freedom when direction of reach was constant and two degrees of freedom when direction of reach varied, irrespective of object distance and orientation. These simulations indicate that reach and grasp movements contain redundancy that is removable by formation of task-dependent synergies. As skilled movement can be planned and executed in a low dimension workspace, control of these independent components lessens central workload.     

Legal and ethical issues in neuroimaging research: human subjects protection,medical privacy,and the public communication of research results

Humans subjects research entails significant legal and ethical obligations. Neuroimaging researchers must be familiar with the requirements of human subjects protection, including evolving standards for the protection of privacy and the disclosure of risk in "non-therapeutic" research. Techniques for creating veridical surface renderings from volumetric anatomical imaging data raise new privacy concerns, particularly under the federal medical privacy regulation. Additionally, neuroimaging researchers must consider their obligation to communicate research results responsibly. The emerging field of neuroethics should strive to raise awareness of these issues and to involve neuroimaging researchers in the legal, ethical, and policy debates that currently surround human subjects research.     

Ethical and practical considerations in managing incidental findings in functional magnetic resonance imaging

Functional magnetic resonance imaging has emerged as a powerful tool for mapping the neurologic underpinnings of sensory, motor and cognitive function. Much of this evolution carries assumptions about the subject population under study and, in particular, the neurologic status of subjects entered into studies either as healthy controls or as belonging to a specific disease group. Recent reports of incidental MRI abnormalities in normal volunteers for fMRI studies have brought to attention a variety of practical challenges and ethical dilemmas for researchers, many of whom are not physicians and most of whom have no formal radiological training. We propose a minimum standard for consenting subjects in fMRI protocols, and consider strategies over the longer term that call for expert physician participation, archiving of incidental findings including false positives, and the adoption of guidelines for handling variation in neural activations or performance that appear outside expected norms.