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Temporal Cortex (temporal + cortex)
Kinds of Temporal Cortex Selected AbstractsHeat Shock Protein-27 Is Upregulated in the Temporal Cortex of Patients with EpilepsyEPILEPSIA, Issue 12 2004Hans-J Bidmon Summary:,Purpose: Heat shock protein-27 (HSP-27) belongs to the group of small heat shock proteins that become induced in response to various pathologic conditions. HSP-27 has been shown to protect cells and subcellular structures, particularly mitochondria, and serves as a carrier for estradiol. It is a reliable marker for tissues affected by oxidative stress. Oxidative stress and related cellular defence mechanisms are currently thought to play a major role during experimentally induced epileptic neuropathology. We addressed the question whether HSP-27 becomes induced in the neocortex resected from patients with pharmacoresistant epilepsy. Methods: Human epileptic temporal neocortex was obtained during neurosurgery, and control tissue was obtained at autopsy from subjects without known neurologic diseases. The tissues were either frozen for Western blot analysis or fixed in Zamboni's fixative for the topographic detection of HSP-27 at the cellular level by means of immunohistochemistry. Results: HSP-27 was highly expressed in all epilepsy specimens and in the cortex of a patient who died in the final stage of multiple sclerosis (positive control), whereas only low amounts of HSP-27 were detectable in control brains. In epilepsy patients, HSP-27 was present in astrocytes and in the walls of blood vessels. The intracortical distribution patterns varied strongly among the epilepsy specimens. Conclusions: These results demonstrate that HSP-27 becomes induced in response to epileptic pathology. Although the functional aspects of HSP-27 induction during human epilepsy have yet to be elucidated, it can be concluded that HSP-27 is a marker for cortical regions in which a stress response has been caused by seizures. [source] Development of cortical and subcortical brain structures in childhood and adolescence: a structural MRI studyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 1 2002Elizabeth R Sowell PhD The purpose of the present study was to describe in greater anatomical detail the changes in brain structure that occur during maturation between childhood and adolescence. High-resolution MRI, tissue classification, and anatomical segmentation of cortical and subcortical regions were used in a sample of 35 normally developing children and adolescents between 7 and 16 years of age (mean age 11 years; 20 males, 15 females). Each cortical and subcortical measure was examined for age and sex effects on raw volumes and on the measures as proportions of total supratentorial cranial volume. Results indicate age-related increases in total supratentorial cranial volume and raw and proportional increases in total cerebral white matter. Gray-matter volume reductions were only observed once variance in total brain size was proportionally controlled. The change in total cerebral white-matter proportion was significantly greater than the change in total cerebral gray-matter proportion over this age range, suggesting that the relative gray-matter reduction is probably due to significant increases in white matter. Total raw cerebral CSF volume increases were also observed. Within the cerebrum, regional patterns varied depending on the tissue (or CSF) assessed. Only frontal and parietal cortices showed changes in gray matter, white matter, and CSF measures. Once the approximately 7% larger brain volume in males was controlled, only mesial temporal cortex, caudate, thalamus, and basomesial diencephalic structures showed sex effects with the females having greater relative volumes in these regions than the males. Overall, these results are consistent with earlier reports and describe in greater detail the regional pattern of age-related differences in gray and white matter in normally developing children and adolescents. [source] Distributed source modeling of language with magnetoencephalography: Application to patients with intractable epilepsyEPILEPSIA, Issue 10 2009Carrie R. McDonald Summary Purpose:, To examine distributed patterns of language processing in healthy controls and patients with epilepsy using magnetoencephalography (MEG), and to evaluate the concordance between laterality of distributed MEG sources and language laterality as determined by the intracarotid amobarbital procedure (IAP). Methods:, MEG was performed in 10 healthy controls using an anatomically constrained, noise-normalized distributed source solution (dynamic statistical parametric map, dSPM). Distributed source modeling of language was then applied to eight patients with intractable epilepsy. Average source strengths within temporoparietal and frontal lobe regions of interest (ROIs) were calculated, and the laterality of activity within ROIs during discrete time windows was compared to results from the IAP. Results:, In healthy controls, dSPM revealed activity in visual cortex bilaterally from ,80 to 120 ms in response to novel words and sensory control stimuli (i.e., false fonts). Activity then spread to fusiform cortex ,160,200 ms, and was dominated by left hemisphere activity in response to novel words. From ,240 to 450 ms, novel words produced activity that was left-lateralized in frontal and temporal lobe regions, including anterior and inferior temporal, temporal pole, and pars opercularis, as well as bilaterally in posterior superior temporal cortex. Analysis of patient data with dSPM demonstrated that from 350 to 450 ms, laterality of temporoparietal sources agreed with the IAP 75% of the time, whereas laterality of frontal MEG sources agreed with the IAP in all eight patients. Discussion:, Our results reveal that dSPM can unveil the timing and spatial extent of language processes in patients with epilepsy and may enhance knowledge of language lateralization and localization for use in preoperative planning. [source] Repetitive transcranial magnetic stimulation improve tinnitus in normal hearing patients: a double-blind controlled, clinical and neuroimaging outcome studyEUROPEAN JOURNAL OF NEUROLOGY, Issue 1 2010R. A. Marcondes Background and purpose:, Tinnitus is a frequent disorder which is very difficult to treat and there is compelling evidence that tinnitus is associated with functional alterations in the central nervous system. Targeted modulation of tinnitus-related cortical activity has been proposed as a promising new treatment approach. We aimed to investigate both immediate and long-term effects of low frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) in patients with tinnitus and normal hearing. Methods:, Using a parallel design, 20 patients were randomized to receive either active or placebo stimulation over the left temporoparietal cortex for five consecutive days. Treatment results were assessed by using the Tinnitus Handicap Inventory. Ethyl cysteinate dimmer-single photon emission computed tomography (SPECT) imaging was performed before and 14 days after rTMS. Results:, After active rTMS there was significant improvement of the tinnitus score as compared to sham rTMS for up to 6 months after stimulation. SPECT measurements demonstrated a reduction of metabolic activity in the inferior left temporal lobe after active rTMS. Conclusion:, These results support the potential of rTMS as a new therapeutic tool for the treatment of chronic tinnitus, by demonstrating a significant reduction of tinnitus complaints over a period of at least 6 months and significant reduction of neural activity in the inferior temporal cortex, despite the stimulation applied on the superior temporal cortex. [source] Doublecortin expression in the normal and epileptic adult human brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008Y. W. J. Liu Abstract Mesial temporal lobe epilepsy (MTLE) is a neurological disorder associated with spontaneous recurrent complex partial seizures and hippocampal sclerosis. Although increased hippocampal neurogenesis has been reported in animal models of MTLE, increased neurogenesis has not been reported in the hippocampus of adult human MTLE cases. Here we showed that cells expressing doublecortin (Dcx), a microtubule-associated protein expressed in migrating neuroblasts, were present in the hippocampus and temporal cortex of the normal and MTLE adult human brain. In particular, increased numbers of Dcx-positive cells were observed in the epileptic compared with the normal temporal cortex. Importantly, 56% of Dcx-expressing cells in the epileptic temporal cortex coexpressed both the proliferative cell marker, proliferating cell nuclear antigen and early neuronal marker, TuJ1, suggesting that they may be newly generated neurons. A subpopulation of Dcx-positive cells in the epileptic temporal cortex also coexpressed the mature neuronal marker, NeuN, suggesting that epilepsy may promote the generation of new neurons in the temporal cortex. This study has identified, for the first time, a novel population of Dcx-positive cells in the adult human temporal cortex that can be upregulated by epilepsy and thus, raises the possibility that these cells may have functional significance in the pathophysiology of epilepsy. [source] The representation of Kanizsa illusory contours in the monkey inferior temporal cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2008Gy. Sáry Abstract Stimulus reduction is an effective way to study visual performance. Cues such as surface characteristics, colour and inner lines can be removed from stimuli, revealing how the change affects recognition and neural processing. An extreme reduction is the removal of the very stimulus, defining it with illusory lines. Perceived boundaries without physical differences between shape and background are called illusory (or subjective) contours. Illusory and real contours activate early stages of the macaque visual pathway in similar ways. However, data relating to the processing of illusory contours in higher visual areas are scarce. We recently reported how illusory contours based on abutting-line gratings affect neurones in the monkey inferotemporal cortex, an area essential for object and shape vision. We now present data on how inferotemporal cortical neurones of monkeys react to another type of shapes, the Kanizsa figures. A set of line drawings, silhouettes, their illusory contour-based counterparts, and control shapes have been presented to awake, fixating rhesus monkeys while single-cell activity was recorded in the anterior part of the inferotemporal cortex. Most of the recorded neurones were responsive and selective to shapes presented as illusory contours. Shape selectivity was proved to be different for line drawings and illusory contours, and also for silhouettes and illusory contours. Neuronal response latencies for Kanizsa figures were significantly longer than those for line drawings and silhouettes. These results reveal differences in processing for Kanizsa figures and shapes having real contours in the monkey inferotemporal cortex. [source] Differential impact of brain damage on the access mode to memory representations: an information theoretic approachEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2007Rosapia Lauro-Grotto Abstract Different access modes to information stored in long-term memory can lead to different distributions of errors in classification tasks. We have designed a famous faces memory classification task that allows for the extraction of a measure of metric content, an index of the relevance of semantic cues for classification performance. High levels of metric content are indicative of a relatively preferred semantic access mode, while low levels, and similar correct performance, suggest a preferential episodic access mode. Compared with normal controls, the metric content index was increased in patients with Alzheimer's disease (AD), decreased in patients with herpes simplex encephalitis, and unvaried in patients with insult in the prefrontal cortex. Moreover, the metric content index was found to correlate with a measure of the severity of dementia in patients with AD, and to track the progression of the disease. These results underline the role of the medial-temporal lobes and of the temporal cortex, respectively, for the episodic and semantic routes to memory retrieval. Moreover, they confirm the reliability of information theoretic measures for characterizing the structure of the surviving memory representations in memory-impaired patient populations. [source] Primary and secondary neural networks of auditory prepulse inhibition: a functional magnetic resonance imaging study of sensorimotor gating of the human acoustic startle responseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2007Linda E. Campbell Abstract Feedforward inhibition deficits have been consistently demonstrated in a range of neuropsychiatric conditions using prepulse inhibition (PPI) of the acoustic startle eye-blink reflex when assessing sensorimotor gating. While PPI can be recorded in acutely decerebrated rats, behavioural, pharmacological and psychophysiological studies suggest the involvement of a complex neural network extending from brainstem nuclei to higher order cortical areas. The current functional magnetic resonance imaging study investigated the neural network underlying PPI and its association with electromyographically (EMG) recorded PPI of the acoustic startle eye-blink reflex in 16 healthy volunteers. A sparse imaging design was employed to model signal changes in blood oxygenation level-dependent (BOLD) responses to acoustic startle probes that were preceded by a prepulse at 120 ms or 480 ms stimulus onset asynchrony or without prepulse. Sensorimotor gating was EMG confirmed for the 120-ms prepulse condition, while startle responses in the 480-ms prepulse condition did not differ from startle alone. Multiple regression analysis of BOLD contrasts identified activation in pons, thalamus, caudate nuclei, left angular gyrus and bilaterally in anterior cingulate, associated with EMG-recorded sensorimotor gating. Planned contrasts confirmed increased pons activation for startle alone vs 120-ms prepulse condition, while increased anterior superior frontal gyrus activation was confirmed for the reverse contrast. Our findings are consistent with a primary pontine circuitry of sensorimotor gating that interconnects with inferior parietal, superior temporal, frontal and prefrontal cortices via thalamus and striatum. PPI processes in the prefrontal, frontal and superior temporal cortex were functionally distinct from sensorimotor gating. [source] Tuning for shape dimensions in macaque inferior temporal cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2005Greet Kayaert Abstract It is widely assumed that distributed bell-shaped tuning (e.g. Radial Basis functions) characterizes the shape selectivity of macaque inferior temporal (IT) neurons, analogous to the orientation or spatial frequency tuning found in early visual cortex. Demonstrating such tuning properties requires testing the responses of neurons for different values along dimensions of shape. We recorded the responses of single macaque IT neurons to variations of a rectangle and a triangle along simple shape dimensions, such as taper and axis curvature. The neurons showed systematic response modulation along these dimensions, with the greatest response, on average, to the highest values on the dimensions, e.g. to the most curved shapes. Within the range of values tested, the response functions were monotonic rather than bell-shaped. Multi-dimensional scaling of the neural responses showed that these simple shape dimensions were coded orthogonally by IT neurons: the degree and direction of responses modulation (i.e. the increase or decrease of responses along a dimension) was independent for the different dimensions. Furthermore, for combinations of curvature-related and other simple shape dimensions, the joint tuning was separable, that is well predicted by the product of the tuning for each of the dimensions. The independence of dimensional tuning may provide the neural basis for the independence of psychophysical judgements of multidimensional stimuli. [source] Functional neuroanatomy of the human near/far response to blur cues: eye-lens accommodation/vergence to point targets varying in depthEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004Hans O. Richter Abstract The purpose of this study was to identify the networks involved in the regulation of visual accommodation/vergence by contrasting the cortical functions subservient to eye-lens accommodation with those evoked by foveal fixation. Neural activity was assessed in normal volunteers by changes in rCBF measured with PET. Thirteen right-handed subjects participated in three monocular tasks: (i) resting with eyes closed; (ii) sustained foveal fixation upon a LED at 1.2 m (0.83 D); and (iii) accommodating alternately on a near (24 cm, 4.16 D) vs. a far (3.0 m, 0.33 D) LED alternately illuminated in sequential 2 s epochs. The contrast between the conditions of near/far accommodation and of constant foveal fixation revealed activation in cerebellar hemispheres and vermis; middle and inferior temporal cortex (BA 20, 21, 37); striate cortex and associative visual areas (BA 17/18). Comparison of the condition of constant fixation with the condition of resting with closed eyes indicated activation of cerebellar hemispheres and vermis; visual cortices (BA 17/18); a right hemisphere dominant network encompassing prefrontal (BA 6, 9, 47), superior parietal (BA 7), and superior temporal (BA 40) cortices; and bilateral thalamus. The contrast between the conditions of near/far accommodation with closed-eye rest reflected an incremental summation of the activations found in the previous comparisons (i.e. activations associated with constant fixation). Neural circuits activated selectively during the near/far response to blur cues over those during constant visual fixation, occupy posterior structures that include occipital visual regions, cerebellar hemispheres and vermis, and temporal cortex. [source] Direction of cross-modal information transfer affects human brain activation: a PET studyEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2002Ryuta Kawashima Abstract The purpose of this study was to determine the functional organization of the human brain involved in cross-modal discrimination between tactile and visual information. Regional cerebral blood flow was measured by positron emission tomography in nine right-handed volunteers during four discrimination tasks; tactile,tactile (TT), tactile,visual (TV), visual,tactile (VT), and visual,visual (VV). The subjects were asked either to look at digital cylinders of different diameters or to grasp the digital cylinders with the thumb and index finger of the right hand using haptic interfaces. Compared with the motor control task in which the subjects looked at and grasped cylinders of the same diameter, the right lateral prefrontal cortex and the right inferior parietal lobule were activated in all the four discrimination tasks. In addition, the dorsal premotor cortex, the ventral premotor cortex, and the inferior temporal cortex of the right hemisphere were activated during VT but not during TV. Our results suggest that the human brain mechanisms underlying cross-modal discrimination have two different pathways depending on the temporal order in which stimuli are presented. [source] Is right hemisphere specialization for face discrimination specific to humans?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2000Kevin D. Broad Abstract Patterns of neural activation during face recognition were investigated in sheep by quantifying altered c-fos mRNA expression in situations where faces (sheep vs. human) can (faces upright) and cannot (faces inverted) be discriminated. Exposure to upright faces selectively increased expression significantly more in the right inferior temporal cortex than in the left, and active choice between upright faces additionally increased expression bilaterally in basal amygdala and hippocampus (CA1,4). Exposure to inverted faces did not lead to enhanced activation in the right inferior temporal cortex, amygdala or hippocampus but instead increased expression levels in the diagonal band of Broca, parietal and cingulate cortices. These results show that discrimination of upright faces in sheep preferentially engages the right temporal cortex, as it does in humans, and that performance of active choices between such faces may additionally involve the basal amygdala and hippocampus. [source] Space and context in the temporal cortexHIPPOCAMPUS, Issue 9 2007David K. Bilkey Abstract The hippocampus has a critical role in certain kinds of spatial memory processes. Hippocampal "place" cells, fire selectively when an animal is in a particular location within the environment. It is thought that this activity underlies a representation of the environment that can be used for memory-based spatial navigation. But how is this representation constructed and how is it "read"? A simple mechanism, based on place field density across an environment, is described that could allow hippocampal representations to be "read" by other brain regions for the purpose of navigation. The possible influence of activity in neighboring brain regions such as the perirhinal cortex, and pre- and para-subiculum on the construction of the hippocampal spatial representation is then discussed. © 2007 Wiley-Liss, Inc. [source] The subiculum comes of ageHIPPOCAMPUS, Issue 11 2006Liset Menendez de la Prida Abstract The subiculum has long been considered as a simple bidirectional relay region interposed between the hippocampus and the temporal cortex. Recent evidence, however, suggests that this region has specific roles in the cognitive functions and pathological deficits of the hippocampal formation. A group of 20 researchers participated in an ESF-sponsored meeting in Oxford in September, 2005 focusing on the neurobiology of the subiculum. Each brought a distinct expertise and approach to the anatomy, physiology, psychology, and pathologies of the subiculum. Here, we review the recent findings that were presented at the meeting. © 2006 Wiley-Liss, Inc. [source] Lag-sensitive repetition suppression effects in the anterior parahippocampal gyrusHIPPOCAMPUS, Issue 5 2005Craig J. Brozinsky Abstract Single-unit recording studies of monkeys have shown that neurons in perirhinal and entorhinal cortex exhibit activity reductions following stimulus repetition, and some have suggested that these "repetition suppression" effects may represent neural signals that support recognition memory. Critically, repetition suppression effects are most pronounced at short intervals between stimulus repetitions. Here, we used event-related functional magnetic resonance imaging (fMRI) to identify repetition suppression effects in the human medial temporal lobe and determine whether these effects are sensitive to the length of the interval between repetitions. Twenty-one participants were scanned while performing a continuous recognition memory task in which the interval between item repetitions was parametrically varied from 2 to 32 intervening items. We found evidence of repetition suppression in the anterior parahippocampal gyrus, but only when the repetition interval was relatively short. Moreover, bilateral hippocampal regions showed lag-sensitive repetition effects. Our results demonstrate that activity in the human medial temporal cortex, like that of monkeys, exhibits repetition suppression effects that are sensitive to the length of the interval between repetitions. © 2005 Wiley-Liss, Inc. [source] Accessing newly learned names and meanings in the native languageHUMAN BRAIN MAPPING, Issue 3 2009Annika Hultén Abstract Ten healthy adults encountered pictures of unfamiliar archaic tools and successfully learned either their name, verbal definition of their usage, or both. Neural representation of the newly acquired information was probed with magnetoencephalography in an overt picture-naming task before and after learning, and in two categorization tasks after learning. Within 400 ms, activation proceeded from occipital through parietal to left temporal cortex, inferior frontal cortex (naming) and right temporal cortex (categorization). Comparison of naming of newly learned versus familiar pictures indicated that acquisition and maintenance of word forms are supported by the same neural network. Explicit access to newly learned phonology when such information was known strongly enhanced left temporal activation. By contrast, access to newly learned semantics had no comparable, direct neural effects. Both the behavioral learning pattern and neurophysiological results point to fundamentally different implementation of and access to phonological versus semantic features in processing pictured objects. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Changes in neural activity associated with learning to articulate novel auditory pseudowords by covert repetitionHUMAN BRAIN MAPPING, Issue 11 2008Andreas M. Rauschecker Abstract Learning to articulate novel combinations of phonemes that form new words through a small number of auditory exposures is crucial for development of language and our capacity for fluent speech, yet the underlying neural mechanisms are largely unknown. We used functional magnetic resonance imaging to reveal repetition,suppression effects accompanying such learning and reflecting discrete changes in brain activity due to stimulus-specific fine-tuning of neural representations. In an event-related design, subjects were repeatedly exposed to auditory pseudowords, which they covertly repeated. Covert responses during scanning and postscanning overt responses showed evidence of learning. An extensive set of regions activated bilaterally when listening to and covertly repeating novel pseudoword stimuli. Activity decreased, with repeated exposures, in a subset of these areas mostly in the left hemisphere, including premotor cortex, supplementary motor area, inferior frontal gyrus, superior temporal cortex, and cerebellum. The changes most likely reflect more efficient representation of the articulation patterns of these novel words in two connected systems, one involved in the perception of pseudoword stimuli (in the left superior temporal cortex) and one for processing the output of speech (in the left frontal cortex). Both of these systems contribute to vocal learning. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [source] Medial temporal lobe activity at recognition increases with the duration of mnemonic delay during an object working memory taskHUMAN BRAIN MAPPING, Issue 11 2007Marco Picchioni Abstract Object working memory (WM) engages a disseminated neural network, although the extent to which the length of time that data is held in WM influences regional activity within this network is unclear. We used functional magnetic resonance imaging to study a delayed matching to sample task in 14 healthy subjects, manipulating the duration of mnemonic delay. Across all lengths of delay, successful recognition was associated with the bilateral engagement of the inferior and middle frontal gyri and insula, the medial and inferior temporal, dorsal anterior cingulate and the posterior parietal cortices. As the length of time that data was held in WM increased, activation at recognition increased in the medial temporal, medial occipito-temporal, anterior cingulate and posterior parietal cortices. These results confirm the components of an object WM network required for successful recognition, and suggest that parts of this network, including the medial temporal cortex, are sensitive to the duration of mnemonic delay. Hum Brain Mapp 2007. © 2006 Wiley-Liss, Inc. [source] Imaging brain activity during natural vision using CASL perfusion fMRIHUMAN BRAIN MAPPING, Issue 7 2007Hengyi Rao Abstract Functional MRI (fMRI) has begun to be used to explore human brain activity during ecological and natural conditions. Arterial spin labeling (ASL) perfusion fMRI provides an appealing approach for imaging sustained brain activity during natural conditions because of its long-term temporal stability and ability to noninvasively quantify absolute cerebral blood flow (CBF). The present study used ASL perfusion fMRI to measure brain activation patterns associated with natural vision by concurrently recording CBF and blood oxygen level-dependent (BOLD) contrasts while subjects were freely viewing a cartoon movie. Reliable quantitative whole-brain CBF values (,60 mL/100g/min) as well as regional CBF values (45,80 mL/100g/min) were measured during movie viewing and resting states. The perfusion contrast revealed CBF increases in multiple visual pathway areas and frontal areas, and CBF decreases in ventromedial frontal cortex and superior temporal cortex during movie viewing compared to resting states. Concurrent BOLD contrast revealed similar but weaker activation and deactivation patterns. Regression analyses of both CBF data and BOLD data showed significant associations between activation in the middle temporal (MT) region and subjects' perception of motion. Region of interest analysis based on a priori literature-defined MT demonstrated significant monotonic stepwise associations between the intensity of motion perception and the CBF and BOLD signal changes. These results demonstrate the feasibility of using ASL perfusion fMRI for imaging both sustained and dynamic effects in neural activation during natural and ecologically valid situations, and support the notion of maintained functional segregation and specialization during natural vision. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Top-down influences on lexical selection during spoken word production: A 4T fMRI investigation of refractory effects in picture namingHUMAN BRAIN MAPPING, Issue 11 2006Greig de Zubicaray Abstract Spoken word production is assumed to involve stages of processing in which activation spreads through layers of units comprising lexical-conceptual knowledge and their corresponding phonological word forms. Using high-field (4T) functional magnetic resonance imaging (fMRI), we assessed whether the relationship between these stages is strictly serial or involves cascaded-interactive processing, and whether central (decision/control) processing mechanisms are involved in lexical selection. Participants performed the competitor priming paradigm in which distractor words, named from a definition and semantically related to a subsequently presented target picture, slow picture-naming latency compared to that with unrelated words. The paradigm intersperses two trials between the definition and the picture to be named, temporally separating activation in the word perception and production networks. Priming semantic competitors of target picture names significantly increased activation in the left posterior temporal cortex, and to a lesser extent the left middle temporal cortex, consistent with the predictions of cascaded-interactive models of lexical access. In addition, extensive activation was detected in the anterior cingulate and pars orbitalis of the inferior frontal gyrus. The findings indicate that lexical selection during competitor priming is biased by top-down mechanisms to reverse associations between primed distractor words and target pictures to select words that meet the current goal of speech. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Neural bases of categorization of simple speech and nonspeech soundsHUMAN BRAIN MAPPING, Issue 8 2006Fatima T. Husain Abstract Categorization is fundamental to our perception and understanding of the environment. However, little is known about the neural bases underlying the categorization of sounds. Using human functional magnetic resonance imaging (fMRI) we compared the brain responses to a category discrimination task with an auditory discrimination task using identical sets of sounds. Our stimuli differed along two dimensions: a speech,nonspeech dimension and a fast,slow temporal dynamics dimension. All stimuli activated regions in the primary and nonprimary auditory cortices in the temporal cortex and in the parietal and frontal cortices for the two tasks. When comparing the activation patterns for the category discrimination task to those for the auditory discrimination task, the results show that a core group of regions beyond the auditory cortices, including inferior and middle frontal gyri, dorsomedial frontal gyrus, and intraparietal sulcus, were preferentially activated for familiar speech categories and for novel nonspeech categories. These regions have been shown to play a role in working memory tasks by a number of studies. Additionally, the categorization of nonspeech sounds activated left middle frontal gyrus and right parietal cortex to a greater extent than did the categorization of speech sounds. Processing the temporal aspects of the stimuli had a greater impact on the left lateralization of the categorization network than did other factors, particularly in the inferior frontal gyrus, suggesting that there is no inherent left hemisphere advantage in the categorical processing of speech stimuli, or for the categorization task itself. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Vowel sound extraction in anterior superior temporal cortexHUMAN BRAIN MAPPING, Issue 7 2006Jonas Obleser Abstract We investigated the functional neuroanatomy of vowel processing. We compared attentive auditory perception of natural German vowels to perception of nonspeech band-passed noise stimuli using functional magnetic resonance imaging (fMRI). More specifically, the mapping in auditory cortex of first and second formants was considered, which spectrally characterize vowels and are linked closely to phonological features. Multiple exemplars of natural German vowels were presented in sequences alternating either mainly along the first formant (e.g., [u]-[o], [i]-[e]) or along the second formant (e.g., [u]-[i], [o]-[e]). In fixed-effects and random-effects analyses, vowel sequences elicited more activation than did nonspeech noise in the anterior superior temporal cortex (aST) bilaterally. Partial segregation of different vowel categories was observed within the activated regions, suggestive of a speech sound mapping across the cortical surface. Our results add to the growing evidence that speech sounds, as one of the behaviorally most relevant classes of auditory objects, are analyzed and categorized in aST. These findings also support the notion of an auditory "what" stream, with highly object-specialized areas anterior to primary auditory cortex. Hum. Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Voxel-based analysis of MRI detects abnormal visual cortex in children and adults with amblyopiaHUMAN BRAIN MAPPING, Issue 2 2005Janine D. Mendola Abstract Amblyopia, sometimes called "lazy eye," is a relatively common developmental visual disorder well characterized behaviorally; however, the neural substrates associated with amblyopia in humans remain unclear. We hypothesized that abnormalities in the cerebral cortex of subjects with amblyopia exist, possibly as a result of experience-dependent neuronal plasticity. Anatomic magnetic resonance imaging (MRI) and psychophysical vision testing was carried out on 74 subjects divided into two age ranges, 7,12 years and 18,35 years, and three diagnoses, strabismic amblyopia, anisometropic amblyopia, and normal vision. We report a behavioral impairment in contrast sensitivity for subjects with amblyopia, consistent with previous reports. When the high-resolution MRI brain images were analyzed quantitatively with optimized voxel-based morphometry, results indicated that adults and children with amblyopia have decreased gray matter volume in visual cortical regions, including the calcarine sulcus, known to contain primary visual cortex. This finding was confirmed with a separate region-of-interest analysis. For the children with amblyopia, additional gray matter reductions in parietal-occipital areas and ventral temporal cortex were detected, consistent with recent reports that amblyopia can result in spatial location and object processing deficits. These data are the first to provide possible neuroanatomic bases for the loss of binocularity and visual sensitivity in children and adults with amblyopia. Hum Brain Mapp 25:222,236, 2005. © 2005 Wiley-Liss, Inc. [source] Neural basis for sentence comprehension: Grammatical and short-term memory componentsHUMAN BRAIN MAPPING, Issue 2 2002Ayanna Cooke Abstract We monitored regional cerebral activity with BOLD fMRI while subjects were presented written sentences differing in their grammatical structure (subject-relative or object-relative center-embedded clauses) and their short-term memory demands (short or long antecedent-gap linkages). A core region of left posterior superior temporal cortex was recruited during all sentence conditions in comparison to a pseudofont baseline, suggesting that this area plays a central role in sustaining comprehension that is common to all sentences. Right posterior superior temporal cortex was recruited during sentences with long compared to short antecedent-gap linkages regardless of grammatical structure, suggesting that this brain region supports passive short-term memory during sentence comprehension. Recruitment of left inferior frontal cortex was most clearly associated with sentences that featured both an object-relative clause and a long antecedent-gap linkage, suggesting that this region supports the cognitive resources required to maintain long-distance syntactic dependencies during the comprehension of grammatically complex sentences. Hum. Brain Mapping 15:80,94, 2001. © 2001 Wiley-Liss, Inc. [source] Neuromagnetic signals associated with reading a kanji character formed by combining two kanji radicalsJAPANESE PSYCHOLOGICAL RESEARCH, Issue 1 2000Toshiaki Imada To find out which brain regions are responsible for the mental construction and recognition of a kanji character initiated by visually presented kanji radicals, rather than by information retained in the memory, a left hen radical and the corresponding right tsukuri radical were simultaneously presented randomly to either the left or right visual field of seven subjects. Thirty left hen radicals and the corresponding right tsukuri radicals were prepared as stimuli; this combination formed over 500 real or pseudo kanji characters. Instead of their usual left and right positions, the left hen radical was always presented above the right tsukuri radical. As quickly and correctly as possible, the subjects released a key when two kanji radicals constituted a single real kanji character and released another key otherwise. We recorded neuromagnetic responses as well as accuracy and reaction time. Left visual field superiority was observed as regards accuracy. This is in good agreement with previous neuropsychological results. Equivalent current dipoles were localized mainly in the left and/or right occipitotemporal regions (ventral visual pathways), the bilateral occipitoparietal regions (dorsal visual pathways) including the supramarginal region, and the areas surrounding the left superior temporal cortex. We suggest that these regions are related to reading and the mental construction of a kanji character from its radicals. [source] The anatomy of language: contributions from functional neuroimagingJOURNAL OF ANATOMY, Issue 3 2000CATHY J. PRICE This article illustrates how functional neuroimaging can be used to test the validity of neurological and cognitive models of language. Three models of language are described: the 19th Century neurological model which describes both the anatomy and cognitive components of auditory and visual word processing, and 2 20th Century cognitive models that are not constrained by anatomy but emphasise 2 different routes to reading that are not present in the neurological model. A series of functional imaging studies are then presented which show that, as predicted by the 19th Century neurologists, auditory and visual word repetition engage the left posterior superior temporal and posterior inferior frontal cortices. More specifically, the roles Wernicke and Broca assigned to these regions lie respectively in the posterior superior temporal sulcus and the anterior insula. In addition, a region in the left posterior inferior temporal cortex is activated for word retrieval, thereby providing a second route to reading, as predicted by the 20th Century cognitive models. This region and its function may have been missed by the 19th Century neurologists because selective damage is rare. The angular gyrus, previously linked to the visual word form system, is shown to be part of a distributed semantic system that can be accessed by objects and faces as well as speech. Other components of the semantic system include several regions in the inferior and middle temporal lobes. From these functional imaging results, a new anatomically constrained model of word processing is proposed which reconciles the anatomical ambitions of the 19th Century neurologists and the cognitive finesse of the 20th Century cognitive models. The review focuses on single word processing and does not attempt to discuss how words are combined to generate sentences or how several languages are learned and interchanged. Progress in unravelling these and other related issues will depend on the integration of behavioural, computational and neurophysiological approaches, including neuroimaging. [source] Reduced right hemisphere activation in severely abused violent offenders during a working memory task: An fMRI studyAGGRESSIVE BEHAVIOR, Issue 2 2001Adrian Raine Abstract This study uses functional magnetic resonance imaging (fMRI) to address two important gaps in our knowledge of brain functioning and violence: (1) What are the brain correlates of adults in the community who have suffered severe physical abuse early in life and who go on to perpetrate serious violence in adulthood? (2) What characterizes those who experience severe physical abuse but who refrain from serious violence? Four groups of participants recruited from the community (controls, severe physical child abuse only, serious violence only, and severely abused, seriously violent offenders) underwent fMRI while performing a visual/verbal working memory task. Violent offenders who had suffered severe child abuse show reduced right hemisphere functioning, particularly in the right temporal cortex. Abused individuals who refrain from serious violence showed relatively lower left, but higher right, activation of the superior temporal gyrus. Abused individuals, irrespective of violence status, showed reduced cortical activation during the working memory task, especially in the left hemisphere. Brain deficits were independent of IQ, history of head injury, task performance, cognitive strategy, and mental activity during the control task. Findings constitute the first fMRI study of brain dysfunction in violent offenders, and indicate that initial right hemisphere dysfunction, when combined with the effects of severe early physical abuse, predisposes to serious violence but that relatively good right hemisphere functioning protects against violence in physically abused children. Aggr. Behav. 27:111,129, 2001. © 2001 Wiley-Liss, Inc. [source] Structural Correlates of Functional Language Dominance: A Voxel-Based Morphometry StudyJOURNAL OF NEUROIMAGING, Issue 2 2010Andreas Jansen PhD ABSTRACT BACKGROUND AND PURPOSE The goal of this study was to explore the structural correlates of functional language dominance by directly comparing the brain morphology of healthy subjects with left- and right-hemisphere language dominance. METHODS Twenty participants were selected based on their language dominance from a cohort of subjects with known language lateralization. Structural differences between both groups were assessed by voxel-based morphometry, a technique that automatically identifies differences in the local gray matter volume between groups using high-resolution T1-weighted magnetic resonance images. RESULTS The main findings can be summarized as follows: (1) Subjects with right-hemisphere language dominance had significantly larger gray matter volume in the right hippocampus than subjects with left-hemisphere language dominance. (2) Leftward structural asymmetries in the posterior superior temporal cortex, including the planum temporale (PT), were observed in both groups. CONCLUSIONS Our study does not support the still prevalent view that asymmetries of the PT are related in a direct way to functional language lateralization. The structural differences found in the hippocampus underline the importance of the medial temporal lobe in the neural language network. They are discussed in the context of recent findings attributing a critical role of the hippocampus in the development of language lateralization. [source] Expression of plasminogen activator inhibitor-1 and protease nexin-1 in human astrocytes: Response to injury-related factorsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 11 2010Karin Hultman Abstract Astrocytes play a diverse role in central nervous system (CNS) injury. Production of the serine protease inhibitors (serpins) plasminogen activator inhibitor-1 (PAI-1) and protease nexin-1 (PN-1) by astrocytes may counterbalance excessive serine protease activity associated with CNS pathologies such as ischemic stroke. Knowledge regarding the regulation of these genes in the brain is limited, so the objective of the present study was to characterize the effects of injury-related factors on serpin expression in human astrocytes. Native human astrocytes were exposed to hypoxia or cytokines, including interleukin-6 (IL-6), IL-1,, tumor necrosis factor-, (TNF-,), IL-10, transforming growth factor-, (TGF-,), and TGF-, for 0,20 hr. Serpin mRNA expression and protein secretion were determined by real-time RT-PCR and ELISA, respectively. Localization of PAI-1 and PN-1 in human brain tissue was examined by immunohistochemistry. Hypoxia and all assayed cytokines induced a significant increase in PAI-1 expression, whereas prolonged treatment with IL-1, or TNF-, resulted in a significant down-regulation. The most pronounced induction of both PAI-1 and PN-1 was observed following early treatment with TGF-,. In contrast to PAI-1, the PN-1 gene did not respond to hypoxia. Positive immunoreactivity for PAI-1 in human brain tissue was demonstrated in reactive astrocytes within gliotic areas of temporal cortex. We show here that human astrocytes express PAI-1 and PN-1 and demonstrate that this astrocytic expression is regulated in a dynamic manner by injury-related factors. © 2010 Wiley-Liss, Inc. [source] Allele C-specific methylation of the 5-HT2A receptor gene: Evidence for correlation with its expression and expression of DNA methylase DNMT1JOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2006Oxana O. Polesskaya Abstract Differential DNA methylation has been suggested to contribute to differential activity of alleles C and T and thereby to genetic associations between the C/T(102) polymorphism in the 5-HT2A receptor gene (5HT2AR) and psychiatric disorders. We surveyed methylation in two CpG sites, which are specific to allele C. The majority of allele C-specific CpG sites were methylated in human temporal cortex and peripheral leukocytes and levels of methylation varied between individuals. Levels of methylation in the promoter correlated significantly with the expression of 5HT2AR. Methylation of allele C-specific CpG sites in the first exon correlated significantly with the expression of DNA methylase 1 (DNMT1) but not S-adenosylhomocysteine hydrolase (AHCY). These findings support the hypothesis that allele-specific DNA methylation is involved in regulation of 5HT2AR expression, influencing expression differences between alleles C and T. © 2005 Wiley-Liss, Inc. [source] | |||||||||||||||||||