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Selected AbstractsFlammability and mechanical properties of wood flour-filled polypropylene compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010M. B. Abu Bakar Abstract Polypropylene (PP) composites filled with wood flour (WF) were prepared with a twin-screw extruder and an injection-molding machine. Three types of ecologically friendly flame retardants (FRs) based on ammonium polyphosphate were used to improve the FR properties of the composites. The flame retardancy of the PP/WF composites was characterized with thermogravimetric analysis (TGA), vertical burn testing (UL94-V), and limiting oxygen index (LOI) measurements. The TGA data showed that all three types of FRs could enhance the thermal stability of the PP/WF/FR systems at high temperatures and effectively increase the char residue formation. The FRs could effectively reduce the flammability of the PP/WF/FR composites by achieving V-0 UL94-V classification. The increased LOI also showed that the flammability of the PP/WF/FR composites was reduced with the addition of FRs. The mechanical property study revealed that, with the incorporation of FRs, the tensile strength and flexural strength were decreased, but the tensile and flexural moduli were increased in all cases. The presence of maleic anhydride grafted polypropylene (MAPP) resulted in an improvement of the filler,matrix bonding between the WF/intumescent FR and PP, and this consequently enhanced the overall mechanical properties of the composites. Morphological studies carried out with scanning electron microscopy revealed clear evidence that the adhesion at the interfacial region was enhanced with the addition of MAPP to the PP/WF/FR composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Comparison of the effects of polyethylenimine and maleated polypropylene coupling agents on the properties of cellulose-reinforced polypropylene compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008C. González-Sánchez Abstract The desire to improve the properties of cellulose-reinforced composites while producing them by methods as similar as possible to those used on an industrial scale is one of the driving forces in this field of research. In this work, extensive research for determining the mechanical, thermal, rheological, and physical properties of novel cellulose-reinforced polypropylene composites containing a polyethylenimine (PEI) coupling agent was conducted. A comparison of their properties with those of reference composites without any coupling agent or containing a maleated polypropylene (MAPP) coupling agent was also carried out. The presence of the PEI coupling agent mainly gave rise to a substantial increase in the tensile and flexural strengths and elongations as well as the impact strength, heat deflection temperature (HDT), melt volume flow index, and water absorption of PEI-containing composites in comparison with composites without any coupling agent added. However, the increases achieved in the tensile and flexural composite strengths and HDT were lower than those achieved with the MAPP coupling agent mainly for composites containing 50 wt % cellulose fibers. On the other hand, PEI-containing composites exhibited, in most cases, larger elongations and energies required to break in tensile tests as well as larger impact strengths, melt volume flow indices, and water absorption percentages than MAPP-containing composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] The relationship among psychological distress, employment, and drug use over time in a sample of female welfare recipientsJOURNAL OF COMMUNITY PSYCHOLOGY, Issue 3 2003John S. Atkinson In this study we examined the relationship over time among work experience, psychological distress, and illegal substance use in a sample of 534 women receiving Temporary Assistance for Needy Families. Study participants were interviewed at intake and at 4-month intervals for a period of 2 years. Each interview recorded the number of hours worked in the previous 4 months and the use of powder cocaine, crack cocaine, heroin, or methamphetamines during the same period. To measure the extent of psychological distress, participants were also administered the personal adjustment problems subscales of the Multidimensional Addictions and Personality Profile (MAPP) at intake and at 1-year intervals. A path model was analyzed to assess the temporal effects of employment, drug use, and emotional and psychological distress. Results suggest a cycle in which employment at one time period can reduce the likelihood of drug use in the following period, which, in turn, can lead to improvement in distress. This improvement can lead to an increase in the number of hours worked and further improvement in distress levels. © 2003 Wiley Periodicals, Inc. J Comm Psychol 31: 223,234, 2003. [source] Effects of alkali and silane treatment on the mechanical properties of jute-fiber-reinforced recycled polypropylene compositesJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2010Xinxin Wang Jute-fibers-reinforced thermoplastic composites are widely used in the automobile, packaging, and electronic industries because of their various advantages such as low cost, ease of recycling, and biodegradability. However, the applications of these kinds of composites are limited because of their unsatisfactory mechanical properties, which are caused by the poor interfacial compatibility between jute fibers and the thermoplastic matrix. In this work, four methods, including (i) alkali treatment, (ii) alkali and silane treatment, (iii) alkali and (maleic anhydride)-polypropylene (MAPP) treatment, and (iv) alkali, silane, and MAPP treatment (ASMT) were used to treat jute fibers and improve the interfacial adhesion of jute-fiber-reinforced recycled polypropylene composites (JRPCS). The mechanical properties and impact fracture surfaces of the composites were observed, and their fracture mechanism was analyzed. The results showed that ASMT composites possessed the optimum comprehensive mechanical properties. When the weight fraction of jute fibers was 15%, the tensile strength and impact toughness were increased by 46 and 36%, respectively, compared to those of untreated composites. The strongest interfacial adhesion between jute fibers and recycled polypropylene was obtained for ASMT composites. The fracture styles of this kind of composite included fiber breakage, fiber pull-out, and interfacial debonding. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers. [source] Development of poly(vinyl chloride)/wood composites.JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2004A literature review Poly(vinyl chloride)/wood fiber (flour) composites are currently experiencing a dramatic increase in use. Most of them are used to produce window/door profiles, decking, railing, and siding by using conical counterrotating intermeshing twin-screw extruders. Heat stabilizers, processing aids, impact modifiers, lubricants, and pigments are still important for PVC/wood composite formulations. Poly[methylene(polyphenyl isocyanate)] (PMPPIC), ,-aminopropyltriethoxysilane, maleated polypropylene (MAPP), and copper metallic complex have proved to be effective coupling agents for this composite system. Mechanical properties of PVC/wood composites can be enhanced by combining wood with mica or glass fibers to form hybrid reinforcements. Ultraviolet light resistance and weathering dimensional stabilities of PVC/wood composites are superior to those of natural wood. Density reduction can be achieved through the microcellular foaming technique by using chemical blowing agents, such as azodicarbonamide and sodium bicarbonate, or physical blowing agents, such as carbon dioxide. J. Vinyl Addit. Technol. 10:59,69, 2004. © 2004 Society of Plastics Engineers. [source] Poly(propylene)/Clay Nanocomposites Prepared by Reactive Compounding with an Epoxy Based MasterbatchMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Ling Chen Abstract Summary: Poly(propylene) (PP)/clay nanocomposites have been prepared via a novel reactive compounding approach, in which an epoxy based masterbatch consisting of 20 wt.-% clay was introduced to poly(propylene) with the aid of a maleic anhydride grafted PP (MAPP). The masterbatch was prepared using a recently developed "slurry compounding" technique. After melt compounding, most clay particles have been exfoliated and dispersed into small stacks with several clay layers. WAXD data shows that the dispersion of clay is better at low clay content or high MAPP content. Due to the novelty of the preparation process and complication of the system, the tensile properties of nanocomposites exhibit some unique tendencies with varying the content of MAPP or masterbatch. It is believed that the yield strength and Young's modulus can be dramatically improved after minimizing the excess of unreacted epoxy and optimizing the dispersion of clay. TEM micrograph of PP/clay nanocomposites prepared with epoxy based masterbatch. [source] Influence of interfacial adhesion on the structural and mechanical behavior of PP-banana/glass hybrid compositesPOLYMER COMPOSITES, Issue 7 2010Sanjay K. Nayak Hybrid composites of polypropylene (PP), reinforced with short banana and glass fibers were fabricated using Haake torque rheocord followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both fibers into PP matrix resulted in increase of tensile strength, flexural strength, and impact strength upto 30 wt% with an optimum strength observed at 2 wt% MAPP treated 15 wt% banana and 15 wt% glass fiber. The rate of water absorption for the hybrid composites was decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has been analyzed to investigate the interfacial properties. An increase in storage modulus (E,) of the treated-composite indicates higher stiffness. The loss tangent (tan ,) spectra confirms a strong influence of fiber loading and coupling agent concentration on the , and , relaxation process of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out through differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA), indicated an increase in the crystallization temperature and thermal stability of PP with the incorporation of MAPP-treated banana and glass fiber. POLYM. COMPOS., 31:1247,1257, 2010. © 2009 Society of Plastics Engineers [source] Effect of maleated polypropylene and impact modifiers on the morphology and mechanical properties of PP/Mica compositesPOLYMER COMPOSITES, Issue 6 2006H. Yazdani Composites of polypropylene (PP) with mica powder and impact modifiers were produced by internal mixer. A major drawback in the use of mica-filled PP is its low impact resistance. In the present study, the effect of the maleated PP (MAPP) and impact modifiers was evaluated on the composite properties separately and together. Thus, two different styrene-ethylene/butylene-styrene triblock copolymers (SEBS) and one ethylene-propylene-diene terpolymer (EPDM) have been used as impact modifiers in the PP-mica composites. Addition of MAPP had a negative effect on the composite notched impact strength and elongation at break but had a positive effect on tensile strength when used together with impact modifiers. All three elastomers increased the impact strength of the PP-mica composites but the addition of maleated SEBS (SEBS-MA) granted the greatest improvement in impact strength. It was inferred from the scanning electron microscopy that SEBS-MA had a stronger interaction with mica surface than the other impact modifiers. POLYM. COMPOS., 27:614,620, 2006. © 2006 Society of Plastics Engineers [source] Individual differences in socioaffective skills influence the neural bases of fear processing: The case of alexithymiaHUMAN BRAIN MAPPING, Issue 10 2010Lydia Pouga Abstract Being exposed to fear signals makes us feel threatened and prompts us to prepare an adaptive response. In our previous studies, we suggested that amygdala (AMG) and premotor cortex (PM) play a role in the preparation of the observers' motor response required by the situation. The present experiment aimed at assessing how interindividual differences in alexithymia,a personality trait associated with deficits in emotional reactivity and regulation,influence the neural network associated with the perception of fear. Using fMRI, we scanned 34 healthy subjects while they were passively observing fearful body expressions. Applying a dimensional approach, we performed correlation analyses between fear-related brain areas and alexithymia scores among all participants. Using a categorical approach, we conducted a between-group comparison (13 high vs. 12 low-alexithymia subjects). Our results were threefold. First, the right AMG activity in response to fearful stimuli was negatively correlated with the level of difficulty to identify emotions. Second, PM activity was linked to reduced subjective emotional reactivity. Third, the between-group comparison revealed greater activity in anterior cingulate cortex (ACC) for high than low-alexithymia scorers. Moreover, the relationship between ACC and PM was in opposite direction in individuals with high (negative link) and low (positive link) alexithymia. Therefore, compared to our previous findings, we hereby further reveal how ACC interacts with PM to sustain self-regulation of one's own emotional state in response to threatening social signals. Moreover, this neural mechanism could account for the description of the "cold-blooded" personality of individuals with alexithymia. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Attachment style, affective loss and gray matter volume: A voxel-based morphometry studyHUMAN BRAIN MAPPING, Issue 10 2010Stefania Benetti Abstract Early patterns of infant attachment have been shown to be an important influence on adult social behavior. Animal studies suggest that patterns of early attachment influence brain development, contributing to permanent alterations in neural structure; however, there are no previous studies investigating whether differences in attachment style are associated with differences in brain structure in humans. In this study, we used Magnetic Resonance Imaging (MRI) and voxel-based morphometry (VBM) to examine for the first time the association between attachment style, affective loss (for example, death of a loved one) and gray matter volume in a healthy sample of adults (n = 32). Attachment style was assessed on two dimensions (anxious and avoidant) using the ECR-Revised questionnaire. High attachment-related anxiety was associated with decreased gray matter in the anterior temporal pole and increased gray matter in the left lateral orbital gyrus. A greater number of affective losses was associated with increased gray matter volume in the cerebellum; in this region, however, the impact of affective losses was significantly moderated by the level of attachment-related avoidance. These findings indicate that differences in attachment style are associated with differences in the neural structure of regions implicated in emotion regulation. It is hypothesized that early attachment experience may contribute to structural brain differences associated with attachment style in adulthood; furthermore, these findings point to a neuronal mechanism through which attachment style may mediate individual differences in responses to affective loss. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] The volatility of the amygdala response to masked fearful eyesHUMAN BRAIN MAPPING, Issue 10 2010Thomas Straube Abstract Recently, it has been suggested that backwardly masked, and thus subliminally presented, fearful eyes are processed by the amygdala. Here, we investigated in four functional magnetic resonance imaging experiments whether the amygdala responds to subliminally presented fearful eyes per se or whether an interaction of masked eyes with the masks or with parts of the masks used for backward masking might be responsible for the amygdala activation. In these experiments, we varied the mask as well as the position of the target eyes. The results show that the amygdala does not respond to masked fearful eyes per se but to an interaction between masked fearful eyes and the eyes of neutral faces used for masking. This finding questions the hypothesis that the amygdala processes context-free parts of the human face without awareness. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Intellectual abilities and white matter microstructure in development: A diffusion tensor imaging studyHUMAN BRAIN MAPPING, Issue 10 2010Christian K. Tamnes Abstract Higher-order cognitive functions are supported by distributed networks of multiple interconnected cortical and subcortical regions. Efficient cognitive processing depends on fast communication between these regions, so the integrity of the connections between them is of great importance. It is known that white matter (WM) development is a slow process, continuing into adulthood. While the significance of cortical maturation for intellectual development is described, less is known about the relationships between cognitive functions and maturation of WM connectivity. In this cross-sectional study, we investigated the associations between intellectual abilities and development of diffusion tensor imaging (DTI) derived measures of WM microstructure in 168 right-handed participants aged 8,30 years. Independently of age and sex, both verbal and performance abilities were positively related to fractional anisotropy (FA) and negatively related to mean diffusivity (MD) and radial diffusivity (RD), predominantly in the left hemisphere. Further, verbal, but not performance abilities, were associated with developmental differences in DTI indices in widespread regions in both hemispheres. Regional analyses showed relations with both FA and RD bilaterally in the anterior thalamic radiation and the cortico-spinal tract and in the right superior longitudinal fasciculus. In these regions, our results suggest that participants with high verbal abilities may show accelerated WM development in late childhood and a subsequent earlier developmental plateau, in contrast to a steadier and prolonged development in participants with average verbal abilities. Longitudinal data are needed to validate these interpretations. The results provide insight into the neurobiological underpinnings of intellectual development. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Independent component analysis of erroneous and correct responses suggests online response controlHUMAN BRAIN MAPPING, Issue 9 2010Sven Hoffmann Abstract After errors in reaction tasks, a sharp negative wave emerges in the event-related potential (ERP), the error (related) negativity (Ne or ERN). However, also after correct trials, an Ne-like wave is seen, called CRN or Nc, which is much smaller than the Ne. This study tested the hypothesis whether Ne and Nc reflect the same functional process, and whether this process is linked to online response control. For this purpose, independent component analysis (ICA) was utilized with the EEG data of two types of reaction tasks: a flanker task and a mental rotation task. To control for speed-accuracy effects, speed and accuracy instructions were balanced in a between subjects design. For both tasks ICA and dipole analysis revealed one component (Ne-IC) explaining most of the variance for the difference between correct and erroneous trials. The Ne-IC showed virtually the same features as the raw postresponse ERP, being larger for erroneous compared to correct trials and for the flanker than for the rotation task. In addition, it peaked earlier for corrected than for uncorrected errors. The results favor the hypothesis that Ne and Nc reflect the same process, which is modulated by response correctness and type of task. On the basis of the literature and the present results, we assume that this process induces online response control, which is much stronger in error than correct trials and with direct rather than indirect stimulus response mapping. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] The role of the superior temporal sulcus and the mirror neuron system in imitationHUMAN BRAIN MAPPING, Issue 9 2010Pascal Molenberghs Abstract It has been suggested that in humans the mirror neuron system provides a neural substrate for imitation behaviour, but the relative contributions of different brain regions to the imitation of manual actions is still a matter of debate. To investigate the role of the mirror neuron system in imitation we used fMRI to examine patterns of neural activity under four different conditions: passive observation of a pantomimed action (e.g., hammering a nail); (2) imitation of an observed action; (3) execution of an action in response to a word cue; and (4) self-selected execution of an action. A network of cortical areas, including the left supramarginal gyrus, left superior parietal lobule, left dorsal premotor area and bilateral superior temporal sulcus (STS), was significantly active across all four conditions. Crucially, within this network the STS bilaterally was the only region in which activity was significantly greater for action imitation than for the passive observation and execution conditions. We suggest that the role of the STS in imitation is not merely to passively register observed biological motion, but rather to actively represent visuomotor correspondences between one's own actions and the actions of others. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Emotional imagery: Assessing pleasure and arousal in the brain's reward circuitryHUMAN BRAIN MAPPING, Issue 9 2010Vincent D. Costa Abstract Research on emotional perception and learning indicates appetitive cues engage nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), whereas amygdala activity is modulated by the emotional intensity of appetitive and aversive cues. This study sought to determine patterns of functional activation and connectivity among these regions during narrative emotional imagery. Using event-related fMRI, we investigate activation of these structures when participants vividly imagine pleasant, neutral, and unpleasant scenes. Results indicate that pleasant imagery selectively activates NAc and mPFC, whereas amygdala activation was enhanced during both pleasant and unpleasant imagery. NAc and mPFC activity were each correlated with the rated pleasure of the imagined scenes, while amygdala activity was correlated with rated emotional arousal. Functional connectivity of NAc and mPFC was evident throughout imagery, regardless of hedonic content, while correlated activation of the amygdala with NAc and mPFC was specific to imagining pleasant scenes. These findings provide strong evidence that pleasurable text-driven imagery engages a core appetitive circuit, including NAc, mPFC, and the amygdala. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Groupwise registration based on hierarchical image clustering and atlas synthesisHUMAN BRAIN MAPPING, Issue 8 2010Qian Wang Abstract Groupwise registration has recently been proposed for simultaneous and consistent registration of all images in a group. Since many deformation parameters need to be optimized for each image under registration, the number of images that can be effectively handled by conventional groupwise registration methods is limited. Moreover, the robustness of registration is at stake due to significant intersubject variability. To overcome these problems, we present a groupwise registration framework, which is based on a hierarchical image clustering and atlas synthesis strategy. The basic idea is to decompose a large-scale groupwise registration problem into a series of small-scale problems, each of which is relatively easy to solve using a general computer. In particular, we employ a method called affinity propagation, which is designed for fast and robust clustering, to hierarchically cluster images into a pyramid of classes. Intraclass registration is then performed to register all images within individual classes, resulting in a representative center image for each class. These center images of different classes are further registered, from the bottom to the top in the pyramid. Once the registration reaches the summit of the pyramid, a single center image, or an atlas, is synthesized. Utilizing this strategy, we can efficiently and effectively register a large image group, construct their atlas, and, at the same time, establish shape correspondences between each image and the atlas. We have evaluated our framework using real and simulated data, and the results indicate that our framework achieves better robustness and registration accuracy compared to conventional methods. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Biasing the organism for novelty: A pervasive property of the attention systemHUMAN BRAIN MAPPING, Issue 8 2010Qi Chen Abstract Although the functional and anatomical independences between the orienting and the executive attention networks have been well established, surprisingly little is known about the potential neural interaction between them. Recent studies point out that spatial inhibition of return (IOR), a mechanism associated with the orienting network, and nonspatial inhibition of return, a mechanism associated with the executive network, might bias the organism for novel locations and objects, respectively. By orthogonally combining the spatial and the nonspatial IOR paradigms in this fMRI study, we demonstrate that the orienting and the executive networks interact and compensate each other in biasing the attention system for novelty. Behaviorally, participants responded slower to the target at the old location only when the color of the target was novel, and participants responded slower to the old color representation only when the target appeared at a novel spatial location. Neurally, the orienting network was involved in slowing down responses to the old location only when the nonspatial IOR mechanism in the executive network was not operative (i.e., when the color of the target was novel); the prefrontal executive network was involved in slowing down responses to the old color representation only when the spatial IOR mechanism in the orienting network was not functioning (i.e., when the target appeared at a novel location). Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Group-level variations in motor representation areas of thenar and anterior tibial muscles: Navigated Transcranial Magnetic Stimulation StudyHUMAN BRAIN MAPPING, Issue 8 2010Eini Niskanen Abstract Navigated transcranial magnetic stimulation (TMS) can be used to stimulate functional cortical areas at precise anatomical location to induce measurable responses. The stimulation has commonly been focused on anatomically predefined motor areas: TMS of that area elicits a measurable muscle response, the motor evoked potential. In clinical pathologies, however, the well-known homunculus somatotopy theory may not be straightforward, and the representation area of the muscle is not fixed. Traditionally, the anatomical locations of TMS stimulations have not been reported at the group level in standard space. This study describes a methodology for group-level analysis by investigating the normal representation areas of thenar and anterior tibial muscle in the primary motor cortex. The optimal representation area for these muscles was mapped in 59 healthy right-handed subjects using navigated TMS. The coordinates of the optimal stimulation sites were then normalized into standard space to determine the representation areas of these muscles at the group-level in healthy subjects. Furthermore, 95% confidence interval ellipsoids were fitted into the optimal stimulation site clusters to define the variation between subjects in optimal stimulation sites. The variation was found to be highest in the anteroposterior direction along the superior margin of the precentral gyrus. These results provide important normative information for clinical studies assessing changes in the functional cortical areas because of plasticity of the brain. Furthermore, it is proposed that the presented methodology to study TMS locations at the group level on standard space will be a suitable tool for research purposes in population studies. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] The neural control of bimanual movements in the elderly: Brain regions exhibiting age-related increases in activity, frequency-induced neural modulation, and task-specific compensatory recruitmentHUMAN BRAIN MAPPING, Issue 8 2010Daniel J. Goble Abstract Coordinated hand use is an essential component of many activities of daily living. Although previous studies have demonstrated age-related behavioral deficits in bimanual tasks, studies that assessed the neural basis underlying such declines in function do not exist. In this fMRI study, 16 old and 16 young healthy adults performed bimanual movements varying in coordination complexity (i.e., in-phase, antiphase) and movement frequency (i.e., 45, 60, 75, 90% of critical antiphase speed) demands. Difficulty was normalized on an individual subject basis leading to group performances (measured by phase accuracy/stability) that were matched for young and old subjects. Despite lower overall movement frequency, the old group "overactivated" brain areas compared with the young adults. These regions included the supplementary motor area, higher order feedback processing areas, and regions typically ascribed to cognitive functions (e.g., inferior parietal cortex/dorsolateral prefrontal cortex). Further, age-related increases in activity in the supplementary motor area and left secondary somatosensory cortex showed positive correlations with coordinative ability in the more complex antiphase task, suggesting a compensation mechanism. Lastly, for both old and young subjects, similar modulation of neural activity was seen with increased movement frequency. Overall, these findings demonstrate for the first time that bimanual movements require greater neural resources for old adults in order to match the level of performance seen in younger subjects. Nevertheless, this increase in neural activity does not preclude frequency-induced neural modulations as a function of increased task demand in the elderly. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Altered representation of expected value in the orbitofrontal cortex in maniaHUMAN BRAIN MAPPING, Issue 7 2010Felix Bermpohl Abstract Objective: Increased responsiveness to appetitive and reduced responsiveness to aversive anticipatory cues may be associated with dysfunction of the brain reward system in mania. Here we studied neural correlates of gain and loss expectation in mania using functional magnetic resonance imaging (fMRI). Method: Fifteen manic patients and 26 matched healthy control individuals performed a monetary incentive delay task, during which subjects anticipated to win or lose a varying amount of money. Varying both magnitude and valence (win, loss) of anticipatory cues allowed us to isolate the effects of magnitude, valence and expected value (magnitude-by-valence interaction). Results: Response times and total gain amount did not differ significantly between groups. FMRI data indicated that the ventral striatum responded according to cued incentive magnitude in both groups, and this effect did not significantly differ between groups. However, a significant group difference was observed for expected value representation in the left lateral orbitofrontal cortex (OFC; BA 11 and 47). In this region, patients showed increasing BOLD responses during expectation of increasing gain and decreasing responses during expectation of increasing loss, while healthy subjects tended to show the inverse effect. In seven patients retested after remission OFC responses adapted to the response pattern of healthy controls. Conclusions: The observed alterations are consistent with a state-related affective processing bias during the expectation of gains and losses which may contribute to clinical features of mania, such as the enhanced motivation for seeking rewards and the underestimation of risks and potential punishments. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] 3D Mapping of brain differences in native signing congenitally and prelingually deaf subjectsHUMAN BRAIN MAPPING, Issue 7 2010Natasha Leporé Abstract In the prelingual and congenital deaf, functional reorganization is known to occur throughout brain regions normally associated with hearing. However, the anatomical correlates of these changes are not yet well understood. Here, we perform the first tensor-based morphometric analysis of voxel-wise volumetric differences in native signing prelingual and congenitally deaf subjects when compared with hearing controls. We obtained T1-weighted scans for 14 native signing prelingual and congenitally deaf subjects and 16 age- and gender-matched controls. We used linear and fluid registration to align each image to a common template. Using the voxel-wise determinant of the Jacobian of the fluid deformation, significant volume increases, of up to 20%, were found in frontal lobe white matter regions including Broca's area, and adjacent regions involved in motor control and language production. A similar analysis was performed on hand-traced corpora callosa. A strong trend for group differences was found in the area of the splenium considered to carry fibers connecting the temporal (and occipital) lobes. These anatomical differences may reflect experience-mediated developmental differences in myelination and cortical maturation associated with prolonged monomodal sensory deprivation. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Amygdala damage affects event-related potentials for fearful faces at specific time windowsHUMAN BRAIN MAPPING, Issue 7 2010Pia Rotshtein Abstract The amygdala is known to influence processing of threat-related stimuli in distant brain regions, including visual cortex. The time-course of these distant influences is unknown, although this information is important for resolving debates over likely pathways mediating an apparent rapidity in emotional processing. To address this, we recorded event-related potentials (ERPs) to seen fearful face expressions, in preoperative patients with medial temporal lobe epilepsy who had varying degrees of amygdala pathology, plus healthy volunteers. We found that amygdala damage diminished ERPs for fearful versus neutral faces within the P1 time-range, ,100,150 ms, and for a later component at ,500,600 ms. Individual severity of amygdala damage determined the magnitude of both these effects, consistent with a causal amygdala role. By contrast, amygdala damage did not affect explicit perception of fearful expressions nor a distinct emotional ERP effect at 150,250 ms. These results demonstrate two distinct time-points at which the amygdala influences fear processing. The data also demonstrate that while not all aspects of expression processing are disrupted by amygdala damage, there is a crucial impact on an early P1 component. These findings are consistent with the existence of multiple processing stages or routes for fearful faces that vary in their dependence on amygdala function. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Common and distinct neural substrates for the perception of speech rhythm and intonationHUMAN BRAIN MAPPING, Issue 7 2010Linjun Zhang Abstract The present study examines the neural substrates for the perception of speech rhythm and intonation. Subjects listened passively to synthesized speech stimuli that contained no semantic and phonological information, in three conditions: (1) continuous speech stimuli with fixed syllable duration and fundamental frequency in the standard condition, (2) stimuli with varying vocalic durations of syllables in the speech rhythm condition, and (3) stimuli with varying fundamental frequency in the intonation condition. Compared to the standard condition, speech rhythm activated the right middle superior temporal gyrus (mSTG), whereas intonation activated the bilateral superior temporal gyrus and sulcus (STG/STS) and the right posterior STS. Conjunction analysis further revealed that rhythm and intonation activated a common area in the right mSTG but compared to speech rhythm, intonation elicited additional activations in the right anterior STS. Findings from the current study reveal that the right mSTG plays an important role in prosodic processing. Implications of our findings are discussed with respect to neurocognitive theories of auditory processing. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Imaging genetics and development: Challenges and promisesHUMAN BRAIN MAPPING, Issue 6 2010B.J. Casey Abstract Excitement with the publication of the human genome has served as catalyst for scientists to uncover the functions of specific genes. The main avenues for understanding gene function have been in behavioral genetics on one end and on the other end, molecular mouse models. Attempts to bridge these approaches have used brain imaging to conveniently link anatomical abnormalities seen in knockout/transgenic mouse models and abnormal patterns of brain activity seen in humans. Although a convenient approach, this article provides examples of challenges for imaging genetics, its application to developmental questions, and promises for future directions. Attempts to link genes, brain, and behavior using behavioral genetics, imaging genetics, and mouse models of behavior are described. Each of these approaches alone, provide limited information on gene function in complex human behavior, but together, they are forming bridges between animal models and human psychiatric disorders. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] The role of puberty in the developing adolescent brainHUMAN BRAIN MAPPING, Issue 6 2010Sarah-Jayne Blakemore Abstract Adolescence refers to the period of physical and psychological development between childhood and adulthood. The beginning of adolescence is loosely anchored to the onset of puberty, which brings dramatic alterations in hormone levels and a number of consequent physical changes. Puberty onset is also associated with profound changes in drives, motivations, psychology, and social life; these changes continue throughout adolescence. There is an increasing number of neuroimaging studies looking at the development of the brain, both structurally and functionally, during adolescence. Almost all of these studies have defined development by chronological age, which shows a strong,but not unitary,correlation with pubertal stage. Very few neuroimaging studies have associated brain development with pubertal stage, and yet there is tentative evidence to suggest that puberty might play an important role in some aspects of brain and cognitive development. In this paper we describe this research, and we suggest that, in the future, developmental neuroimaging studies of adolescence should consider the role of puberty. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Neuroimaging of the developing brain: Taking "developing" seriouslyHUMAN BRAIN MAPPING, Issue 6 2010Annette Karmiloff-Smith Abstract With a few notable exceptions, many studies, be they behavioral, neuroimaging, or genetic, are snapshots that compare one child group to one adult group, which capture only two points in time and tell the scientist nothing about the mechanisms underlying neural trajectories over developmental time. Thus, a distinction needs to be drawn between child neuroimaging and developmental neuroimaging, the latter approach being relevant not just to children, but to adults and the ageing brain. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc. [source] Enhanced effectiveness in visuo-haptic object-selective brain regions with increasing stimulus salienceHUMAN BRAIN MAPPING, Issue 5 2010Sunah Kim Abstract The occipital and parietal lobes contain regions that are recruited for both visual and haptic object processing. The purpose of the present study was to characterize the underlying neural mechanisms for bimodal integration of vision and haptics in these visuo-haptic object-selective brain regions to find out whether these brain regions are sites of neuronal or areal convergence. Our sensory conditions consisted of visual-only (V), haptic-only (H), and visuo-haptic (VH), which allowed us to evaluate integration using the superadditivity metric. We also presented each stimulus condition at two different levels of signal-to-noise ratio or salience. The salience manipulation allowed us to assess integration using the rule of inverse effectiveness. We were able to localize previously described visuo-haptic object-selective regions in the lateral occipital cortex (lateral occipital tactile-visual area) and the intraparietal sulcus, and also localized a new region in the left anterior fusiform gyrus. There was no evidence of superadditivity with the VH stimulus at either level of salience in any of the regions. There was, however, a strong effect of salience on multisensory enhancement: the response to the VH stimulus was more enhanced at higher salience across all regions. In other words, the regions showed enhanced integration of the VH stimulus with increasing effectiveness of the unisensory stimuli. We called the effect "enhanced effectiveness." The presence of enhanced effectiveness in visuo-haptic object-selective brain regions demonstrates neuronal convergence of visual and haptic sensory inputs for the purpose of processing object shape. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Step-by-step: The effects of physical practice on the neural correlates of locomotion imagery revealed by fMRIHUMAN BRAIN MAPPING, Issue 5 2010Silvio Ionta Abstract Previous studies have shown that mental imagery is a suitable tool to study the progression of the effect of practice on brain activation. Nevertheless, there is still poor knowledge of changes in brain activation patterns during the very early stages of physical practice. In this study, early and late practice stages of different kinds of locomotion (i.e., balanced and unbalanced) have been investigated using functional magnetic resonance imaging during mental imagery of locomotion and stance. During the task, cardiac activity was also recorded. The cerebral network comprising supplementary motor area, basal ganglia, bilateral thalamus, and right cerebellum showed a stronger activation during the imagery of locomotion with respect to imagery of stance. The heart beat showed a significant increase in frequency during the imagery of locomotion with respect to the imagery of stance. Moreover, early stages of practice determined an increased activation in basal ganglia and thalamus with respect to late stages. In this way, it is proposed the modulation of the brain network involved in the imagery of locomotion as a function of physical practice time. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Sensorimotor network rewiring in mild cognitive impairment and Alzheimer's diseaseHUMAN BRAIN MAPPING, Issue 4 2010Federica Agosta Abstract This study aimed at elucidating whether (a) brain areas associated with motor function show a change in functional magnetic resonance imaging (fMRI) signal in amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD), (b) such change is linear over the course of the disease, and (c) fMRI changes in aMCI and AD are driven by hippocampal atrophy, or, conversely, reflect a nonspecific neuronal network rewiring generically associated to brain tissue damage. FMRI during the performance of a simple motor task with the dominant right-hand, and structural MRI (i.e., dual-echo, 3D T1-weighted, and diffusion tensor [DT] MRI sequences) were acquired from 10 AD patients, 15 aMCI patients, and 11 healthy controls. During the simple-motor task, aMCI patients had decreased recruitment of the left (L) inferior frontal gyrus compared to controls, while they showed increased recruitment of L postcentral gyrus and head of L caudate nucleus, and decreased activation of the cingulum compared with AD patients. Effective connectivity was altered between primary sensorimotor cortices (SMC) in aMCI patients vs. controls, and between L SMC, head of L caudate nucleus, and cingulum in AD vs. aMCI patients. Altered fMRI activations and connections were correlated with the hippocampal atrophy in aMCI and with the overall GM microstructural damage in AD. Motor-associated functional cortical changes in aMCI and AD mirror fMRI changes of the cognitive network, suggesting the occurrence of a widespread brain rewiring with increasing structural damage rather than a specific response of cognitive network. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Primary and multisensory cortical activity is correlated with audiovisual perceptsHUMAN BRAIN MAPPING, Issue 4 2010Margo McKenna Benoit Abstract Incongruent auditory and visual stimuli can elicit audiovisual illusions such as the McGurk effect where visual /ka/ and auditory /pa/ fuse into another percept such as/ta/. In the present study, human brain activity was measured with adaptation functional magnetic resonance imaging to investigate which brain areas support such audiovisual illusions. Subjects viewed trains of four movies beginning with three congruent /pa/ stimuli to induce adaptation. The fourth stimulus could be (i) another congruent /pa/, (ii) a congruent /ka/, (iii) an incongruent stimulus that evokes the McGurk effect in susceptible individuals (lips /ka/ voice /pa/), or (iv) the converse combination that does not cause the McGurk effect (lips /pa/ voice/ ka/). This paradigm was predicted to show increased release from adaptation (i.e. stronger brain activation) when the fourth movie and the related percept was increasingly different from the three previous movies. A stimulus change in either the auditory or the visual stimulus from /pa/ to /ka/ (iii, iv) produced within-modality and cross-modal responses in primary auditory and visual areas. A greater release from adaptation was observed for incongruent non-McGurk (iv) compared to incongruent McGurk (iii) trials. A network including the primary auditory and visual cortices, nonprimary auditory cortex, and several multisensory areas (superior temporal sulcus, intraparietal sulcus, insula, and pre-central cortex) showed a correlation between perceiving the McGurk effect and the fMRI signal, suggesting that these areas support the audiovisual illusion. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] | ||||||||||