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Brain Responses (brain + response)
Selected AbstractsBrain responses to surprising sounds are related to temperament and parent,child dyadic synchrony in young childrenDEVELOPMENTAL PSYCHOBIOLOGY, Issue 6 2010Anu-Katriina Pesonen Abstract This study investigated the relationship between temperament characteristics, parent,child dyadic synchrony and auditory event-related potentials (ERP) in 15 two-year-old children. Temperament was assessed with the Early Childhood Behavior Questionnaire, and parent,child dyadic synchrony was analyzed from video-taped play situations. Involuntary switching of attention toward surprising sounds was measured with auditory ERPs by quantifying the P3a response for repeated and nonrepeated novel, naturally varying sounds, presented in a continuous repetitive sound sequence. Lower negative emotionality, higher effortful control and higher dyadic synchrony were associated with larger P3a responses to repeated novel sounds. The results demonstrate that temperament is related to P3a responses in early childhood, and that parent,child synchrony associates with both temperament and P3a responses in a theoretically meaningful way. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52: 513,523, 2010. [source] Brain responses to subject-verb agreement violations in spoken language in developmental dyslexia: an ERP studyDYSLEXIA, Issue 2 2006Judith E. Rispens Abstract This study investigates the presence and latency of the P600 component in response to subject,verb agreement violations in spoken language in people with and without developmental dyslexia. The two groups performed at-ceiling level on judging the sentences on their grammaticality, but the ERP data revealed subtle differences between them. The P600 tended to peak later in the left posterior region in the dyslexic group compared with the control group. In addition, the group of dyslexic subjects did not show a P600 in response to sentences with a plural NP subject. These results suggest that brain activation involved in syntactic repair is more affected by linguistic complexity in developmental dyslexia compared with non-dyslexic individuals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Brain responses to auditory and visual stimulus offset: Shared representations of temporal edgesHUMAN BRAIN MAPPING, Issue 3 2009Marcus Herdener Abstract Edges are crucial for the formation of coherent objects from sequential sensory inputs within a single modality. Moreover, temporally coincident boundaries of perceptual objects across different sensory modalities facilitate crossmodal integration. Here, we used functional magnetic resonance imaging in order to examine the neural basis of temporal edge detection across modalities. Onsets of sensory inputs are not only related to the detection of an edge but also to the processing of novel sensory inputs. Thus, we used transitions from input to rest (offsets) as convenient stimuli for studying the neural underpinnings of visual and acoustic edge detection per se. We found, besides modality-specific patterns, shared visual and auditory offset-related activity in the superior temporal sulcus and insula of the right hemisphere. Our data suggest that right hemispheric regions known to be involved in multisensory processing are crucial for detection of edges in the temporal domain across both visual and auditory modalities. This operation is likely to facilitate cross-modal object feature binding based on temporal coincidence. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Immature cortical responses to auditory stimuli in specific language impairment: evidence from ERPs to rapid tone sequencesDEVELOPMENTAL SCIENCE, Issue 4 2004D.V.M. Bishop Event-related potentials (ERPs) to tone pairs and single tones were measured for 16 participants with specific language impairment (SLI) and 16 age-matched controls aged from 10 to 19 years. The tone pairs were separated by an inter-stimulus interval (ISI) of 20, 50 or 150 ms. The intraclass correlation (ICC) was computed for each participant between the ERP to a single tone and the ERP to the tone pair. A high ICC indicates that the brain response to a tone pair is similar to that for a single tone. ICCs were significantly higher at short than at long ISIs. At 50-ms ISI, ICCs were higher for younger than older participants. Age and ISI interacted with SLI status: ERPs of older participants with SLI differed from age-matched controls, and resembled ERPs of younger controls, consistent with a theory of immature auditory processing in SLI. [source] A neuroanatomically grounded Hebbian-learning model of attention,language interactions in the human brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2008Max Garagnani Abstract Meaningful familiar stimuli and senseless unknown materials lead to different patterns of brain activation. A late major neurophysiological response indexing ,sense' is the negative component of event-related potential peaking at around 400 ms (N400), an event-related potential that emerges in attention-demanding tasks and is larger for senseless materials (e.g. meaningless pseudowords) than for matched meaningful stimuli (words). However, the mismatch negativity (latency 100,250 ms), an early automatic brain response elicited under distraction, is larger to words than to pseudowords, thus exhibiting the opposite pattern to that seen for the N400. So far, no theoretical account has been able to reconcile and explain these findings by means of a single, mechanistic neural model. We implemented a neuroanatomically grounded neural network model of the left perisylvian language cortex and simulated: (i) brain processes of early language acquisition and (ii) cortical responses to familiar word and senseless pseudoword stimuli. We found that variation of the area-specific inhibition (the model correlate of attention) modulated the simulated brain response to words and pseudowords, producing either an N400- or a mismatch negativity-like response depending on the amount of inhibition (i.e. available attentional resources). Our model: (i) provides a unifying explanatory account, at cortical level, of experimental observations that, so far, had not been given a coherent interpretation within a single framework; (ii) demonstrates the viability of purely Hebbian, associative learning in a multilayered neural network architecture; and (iii) makes clear predictions on the effects of attention on latency and magnitude of event-related potentials to lexical items. Such predictions have been confirmed by recent experimental evidence. [source] Enhanced mismatch negativity brain response after binaural word presentationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2004Tanja Endrass Abstract An oddball paradigm was used to investigate brain processes elicited by spoken words and pseudowords played monaurally, to the left or right ear, or simultaneously to both ears of human subjects instructed to ignore acoustic stimuli but watch a silent video film. The mismatch negativity (MMN), a neurophysiological index of the automatic activation of cortical memory traces, was calculated as the difference between the event-related potential elicited by an infrequent deviant stimulus and the event-related potential to the same item presented as a frequent standard stimulus. Consistent with earlier reports, the MMN to words was larger than that to pseudowords, possibly reflecting the existence of memory traces for spoken words. Bilateral redundant stimulus presentation led to a further increase of the MMN to words relative to both unilateral stimulation modes. This bilateral redundancy gain was absent for pseudowords. We interpret the neurophysiological manifestation of a word-specific bilateral redundancy gain as evidence for interhemispheric cooperation in the automatic access to memory traces for spoken words. Accordingly, word-related cortical networks distributed over both hemispheres allow summation of neural activity between and within hemispheres, thereby potentiating the word-related MMN. [source] The effect of stimulus intensity on brain responses evoked by transcranial magnetic stimulationHUMAN BRAIN MAPPING, Issue 3 2004Soile Komssi Abstract To better understand the neuronal effects of transcranial magnetic stimulation (TMS), we studied how the TMS-evoked brain responses depend on stimulation intensity. We measured electroencephalographic (EEG) responses to motor-cortex TMS, estimated the intensity dependence of the overall brain response, and compared it to a theoretical model for the intensity dependence of the TMS-evoked neuronal activity. Left and right motor cortices of seven volunteers were stimulated at intensities of 60, 80, 100, and 120% of the motor threshold (MT). A figure-of-eight coil (diameter of each loop 4 cm) was used for focal stimulation. EEG was recorded with 60 scalp electrodes. The intensity of 60% of MT was sufficient to produce a distinct global mean field amplitude (GMFA) waveform in all subjects. The GMFA, reflecting the overall brain response, was composed of four peaks, appearing at 15 ± 5 msec (Peak I), 44 ± 10 msec (II), 102 ± 18 msec (III), and 185 ± 13 msec (IV). The peak amplitudes depended nonlinearly on intensity. This nonlinearity was most pronounced for Peaks I and II, whose amplitudes appeared to sample the initial part of the sigmoid-shaped curve modeling the strength of TMS-evoked neuronal activity. Although the response amplitude increased with stimulus intensity, scalp distributions of the potential were relatively similar for the four intensities. The results imply that TMS is able to evoke measurable brain activity at low stimulus intensities, probably significantly below 60% of MT. The shape of the response-stimulus intensity curve may be an indicator of the activation state of the brain. Hum. Brain Mapp. 21:154,164, 2004. © 2004 Wiley-Liss, Inc. [source] Comparison of neuronal and hemodynamic measures of the brain response to visual stimulation: An optical imaging studyHUMAN BRAIN MAPPING, Issue 1 2001Gabriele Gratton Abstract The noninvasive mapping of hemodynamic brain activity has led to significant advances in neuroimaging. This approach is based in part on the assumption that hemodynamic changes are proportional to (and therefore constitute a linear measure of) neuronal activity. We report a study investigating the quantitative relationship between neuronal and hemodynamic measures. This study exploited the fact that optical imaging methods can simultaneously provide noninvasive measures of neuronal and hemodynamic activity from the same region of the brain. We manipulated visual stimulation frequency and measured responses from the medial occipital area of 8 young adults. The results were consistent with a model postulating a linear relationship between the neuronal activity integrated over time and the amplitude of the hemodynamic response. The hemodynamic response colocalized with the neuronal response. These data support the use of quantitative neuroimaging methods to infer the intensity and localization of neuronal activity in occipital areas. Hum. Brain Mapping 13:13,25, 2001. © 2001 Wiley-Liss, Inc. [source] Dexamethasone up-regulates type II IL-1 receptor in mouse primary activated astrocytesJOURNAL OF NEUROCHEMISTRY, Issue 3 2001F. Pousset Brain astrocytes play a pivotal role in the brain response to inflammation. They express IL-1 receptors including the type I IL-1 receptor (IL-1RI) that transduces IL-1 signals in cooperation with the IL-1 receptor accessory protein (IL-1RAcP) and the type II IL-1 receptor (IL-1RII) that functions as a decoy receptor. As glucocorticoid receptors are expressed on astrocytes, we hypothesized that glucocorticoids regulate IL-1 receptors expression. IL-1,-activated mouse primary astrocytes were treated with 10,6 M dexamethasone, and IL-1 receptors were studied at the mRNA and protein levels. Using RT-PCR, IL-1RI and IL-1RII but not IL-1RAcP mRNAs were found to be up-regulated by dexamethasone in a time-dependent manner. Dexamethasone (Dex), but not progesterone, had no effect on IL-1RI but strongly increased IL-1RII mRNA expression. Binding studies revealed an increase in the number of IL-1RII binding sites under the effect of Dex, but no change in affinity. These findings support the concept that glucocorticoids have important regulatory effect on the response of astrocytes to IL-1. [source] Blood Oxygen Level Dependent Response and Spatial Working Memory in Adolescents With Alcohol Use DisordersALCOHOLISM, Issue 10 2004Susan F. Tapert Background: Previous studies have suggested neural disruption and reorganization in young and older adults with alcohol use disorders (AUD). However, it remains unclear at what age and when in the progression of AUD changes in brain functioning might occur. Methods: Alcohol use disordered (n= 15) and nonabusing (n= 19) boys and girls aged 15 to 17 were recruited from local high schools. Functional magnetic resonance imaging data were collected after a minimum of 5 days' abstinence as participants performed spatial working memory and simple motor tasks. Results: Adolescents with AUD showed greater brain response to the spatial working memory task in bilateral parietal cortices and diminished response in other regions, including the left precentral gyrus and bilateral cerebellar areas (clusters ,943 ,l; p < 0.05), although groups did not differ on behavioral measures of task performance. No brain response differences were observed during a simple finger-tapping task. The degree of abnormality was greater for teens who reported experiencing more withdrawal or hangover symptoms and who consumed more alcohol. Conclusions: Adolescents with AUD show abnormalities in brain response to a spatial working memory task, despite adequate performance, suggesting that subtle neuronal reorganization may occur early in the course of AUD. [source] Evolution of Brain Impedance in Dystonic Patients Treated by GPi Electrical StimulationNEUROMODULATION, Issue 2 2004Simone Hemm BME. Abstract Deep Brain Stimulation is an effective treatment of generalized dystonia. Optimal stimulation parameters vary between patients. This article investigates the influence of electrical brain impedance and delivered current on the brain response to stimulation. Twenty-four patients were bilaterally stimulated in the globus pallidus internus through two implanted four-contact electrodes. The variation of brain impedance and current measurements was correlated with stimulation parameters, time course, and clinical outcome. When a contact was activated, a statistically significant and reversible decrease of brain impedance was found. Impedance and current values and their variations with time significantly differed between patients. The absolute impedance did not significantly correlate with the final outcome. We conclude that the reversible decrease of impedance reflects an adaptive long-term mechanism, which could be due to a plasticity phenomenon, but has no prognostic value. Impedance and current measurements give new complementary information for parameter adjustment and trouble shooting and should therefore be included in all patients' follow-up. [source] Is there pre-attentive memory-based comparison of pitch?PSYCHOPHYSIOLOGY, Issue 4 2001Thomas Jacobsen The brain's responsiveness to changes in sound frequency has been demonstrated by an overwhelming number of studies. Change detection occurs unintentionally and automatically. It is generally assumed that this brain response, the so-called mismatch negativity (MMN) of the event-related brain potential or evoked magnetic field, is based on the outcome of a memory-comparison mechanism rather than being due to a differential state of refractoriness of tonotopically organized cortical neurons. To the authors' knowledge, however, there is no entirely compelling evidence for this belief. An experimental protocol controlling for refractoriness effects was developed and a true memory-comparison-based brain response to pitch change was demonstrated. [source] C3H/HeJ Mouse Model for Spontaneous Chronic Otitis Media,THE LARYNGOSCOPE, Issue 7 2006Carol J. MacArthur MD Abstract Objectives/Hypothesis: Chronic otitis media is a significant clinical problem. Understanding the mechanisms of chronic otitis media is critical for its control. However, little is known of these processes as a result of lack of animal models of spontaneous otitis media. The C3H/HeJ mouse has a single amino acid substitution in its toll-like receptor 4 (TLR4), making it insensitive to endotoxin. As a result, these mice cannot clear Gram-negative bacteria. The chronically inflamed middle ear in this animal provides us the opportunity to study spontaneous chronic otitis media. Study Design and Methods: Otoscopy and auditory brain response (ABR) evaluation of C3H/HeJ mice at 3, 5, 7, 9, and 11 months were carried out under sedation. At 12 months of age, mice were killed and histologic analysis of the middle ear, inner ear, and eustachian tube was carried out. Results: Tympanic membrane visualization and ABR thresholds in 7- to 8-month-old C3H/HeJ mice showed that approximately half developed middle and inner ear disease spontaneously. The significant elevation of thresholds suggested a sensorineural component in addition to the conductive loss. Middle and inner ear histology showed some degree of middle and inner ear inflammation in half the mice, paralleling the ABR data. Conclusions: The histopathologic changes reported here in the C3H/HeJ mouse model of chronic otitis media have been reported in human chronic otitis media. This spontaneous model of chronic otitis media will be valuable for the characterization of middle and inner ear inflammatory disease processes that are induced by middle ear infections. [source] Injections of Blood, Thrombin, and Plasminogen More Severely Damage Neonatal Mouse Brain Than Mature Mouse BrainBRAIN PATHOLOGY, Issue 4 2005Mengzhou Xue MD The mechanism of brain cell injury associated with intracerebral hemorrhage may be in part related to proteolytic enzymes in blood, some of which are also functional in the developing brain. We hypothesized that there would be an age-dependent brain response following intracerebral injection of blood, thrombin, and plasminogen. Mice at 3 ages (neonatal, 10-day-old, and young adult) received autologous blood (15, 25, and 50 ,l respectively), thrombin (3, 5, and 10 units respectively), plasminogen (0.03, 0.05, and 0.1 units respectively) (the doses expected in same volume blood), or saline injection into lateral striatum. Forty-eight hours later they were perfusion fixed. Hematoxylin and eosin, lectin histochemistry, Fluoro-Jade, and TUNEL staining were used to quantify changes related to the hemorrhagic lesion. Damage volume, dying neurons, neutrophils, and microglial reaction were significantly greater following injections of blood, plasminogen, and thrombin compared to saline in all three ages of mice. Plasminogen and thrombin associated brain damage was greatest in neonatal mice and, in that group unlike the other 2, greater than the damage caused by whole blood. These results suggest that the neonatal brain is relatively more sensitive to proteolytic plasma enzymes than the mature brain. [source] Age-related changes in transient and oscillatory brain responses to auditory stimulation during early adolescenceDEVELOPMENTAL SCIENCE, Issue 2 2009Catherine Poulsen Maturational changes in the capacity to process quickly the temporal envelope of sound have been linked to language abilities in typically developing individuals. As part of a longitudinal study of brain maturation and cognitive development during adolescence, we employed dense-array EEG and spatiotemporal source analysis to characterize maturational changes in the timing of brain responses to temporal variations in sound. We found significant changes in the brain responses compared longitudinally at two time points in early adolescence, namely 10 years (65 subjects) and 11.5 years (60 of the 65 subjects), as well as large differences between adults, studied with the same protocol (Poulsen, Picton & Paus, 2007), and the children at 10 and 11.5 years of age. The transient auditory evoked potential to tone onset showed decreases in the latency of vertex and T-complex components, and a highly significant increase in the amplitude of the N1 wave with increasing age. The auditory steady state response to a 40-Hz frequency-modulated tone increased in amplitude with increasing age. The peak frequency of the envelope-following response to sweeps of amplitude-modulated white noise also increased significantly with increasing age. These results indicate persistent maturation of the cortical mechanisms for auditory processing from childhood into middle adulthood. [source] The application of transcranial magnetic stimulation in psychiatry and neurosciences researchACTA PSYCHIATRICA SCANDINAVICA, Issue 5 2002P. B. Fitzgerald Objective:,Over recent years transcranial magnetic stimulation (TMS) has become widely applied in the study of neuropsychiatric disorders. The aim of this article is to review the application of TMS as an investigative tool and as a potential therapeutic modality in psychiatric disorders. Method:,A comprehensive literature review. Results:,When applied as an investigative tool, TMS provides innovative ways to directly study the excitability of the cortex, cortical regional connectivity, the plasticity of brain responses and cognitive functioning in illness and disease states. A number of studies suggest the potential of treatment with TMS in disease states, especially in patients with depression, although difficulties exist with the interpretation of the published literature. Conclusion:,TMS has a considerable role in neuropsychiatric research. It appears to have considerable potential as a therapeutic tool in depression, and perhaps a role in several other disorders, although widespread application requires larger trials and establishment of sustained response. [source] Effect of acute hyperglycaemia on sensory processing in diabetic autonomic neuropathyEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 10 2010Jens B. Frøkjær Eur J Clin Invest 2010; 40 (10): 883,886 Abstract Background, Acute hyperglycaemia is known to increase gastrointestinal (GI) sensitivity in healthy subjects and may contribute to the increased prevalence of GI symptoms in diabetes patients. The aim of this study was to evaluate the effect of acute hyperglycaemia on perception and brain responses to painful visceral and somatic stimuli in diabetic patients. Materials and methods, The sensitivity and evoked brain potentials (EPs) to electrical oesophageal and median nerve stimulations were assessed in 14 type-1 diabetes patients with autonomic neuropathy and GI symptoms using a hyperinsulinaemic clamp at 6 and 15 mM. Results, No differences between the normo- and hyperglycaemic conditions were found in sensitivity to both oesophageal (P = 0·72) and median nerve (P = 0·66) stimulations. The latencies and amplitudes of EPs did not differ between the normo- and hyperglycaemic conditions following oesophageal (P = 0·53 and 0·57) and median nerve (P = 0·78 and 0·52) stimulations. Conclusions, Acute hyperglycaemia itself does not contribute to the sensations in patients with longstanding diabetes and autonomic neuropathy. Any potential sensory effects of acute hyperglycaemia can likely be blurred by the neuropathic-like changes in the sensory nervous system. [source] Repetition suppression of induced gamma band responses is eliminated by task switchingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2006Thomas Gruber Abstract The formation of cortical object representations requires the activation of cell assemblies, correlated by induced oscillatory bursts of activity >,20 Hz (induced gamma band responses; iGBRs). One marker of the functional dynamics within such cell assemblies is the suppression of iGBRs elicited by repeated stimuli. This effect is commonly interpreted as a signature of ,sharpening' processes within cell-assemblies, which are behaviourally mirrored in repetition priming effects. The present study investigates whether the sharpening of primed objects is an automatic consequence of repeated stimulus processing, or whether it depends on task demands. Participants performed either a ,living/non-living' or a ,bigger/smaller than a shoebox' classification on repeated pictures of everyday objects. We contrasted repetition-related iGBR effects after the same task was used for initial and repeated presentations (no-switch condition) with repetitions after a task-switch occurred (switch condition). Furthermore, we complemented iGBR analysis by examining other brain responses known to be modulated by repetition-related memory processes (evoked gamma oscillations and event-related potentials; ERPs). The results obtained for the ,no-switch' condition replicated previous findings of repetition suppression of iGBRs at 200,300 ms after stimulus onset. Source modelling showed that this effect was distributed over widespread cortical areas. By contrast, after a task-switch no iGBR suppression was found. We concluded that iGBRs reflect the sharpening of a cell assembly only within the same task. After a task switch the complete object representation is reactivated. The ERP (220,380 ms) revealed suppression effects independent of task demands in bilateral posterior areas and might indicate correlates of repetition priming in perceptual structures. [source] Effects of attention and arousal on early responses in striate cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2005Vahe Poghosyan Abstract Humans employ attention to facilitate perception of relevant stimuli. Visual attention can bias the selection of a location in the visual field, a whole visual object or any visual feature of an object. Attention draws on both current behavioral goals and/or the saliency of physical attributes of a stimulus, and it influences activity of different brain regions at different latencies. Attentional effect in the striate and extrastriate cortices has been the subject of intense research interest in many recent studies. The consensus emerging from them places the first attentional effects in extrastriate areas, which in turn modulate activity of V1 at later latencies. In this view attention influences activity in striate cortex some 150 ms after stimulus onset. Here we use magnetoencephalography to compare brain responses to foveally presented identical stimuli under the conditions of passive viewing, when the stimuli are irrelevant to the subject and under an active GO/NOGO task, when the stimuli are cues instructing the subject to make or inhibit movement of his/her left or right index finger. The earliest striate activity was identified 40,45 ms after stimulus onset, and it was identical in passive and active conditions. Later striate response starting at about 70 ms and reaching a peak at about 100 ms showed a strong attentional modulation. Even before the striate cortex, activity of the right inferior parietal lobule was modulated by attention, suggesting this region as a candidate for mediating attentional signals to the striate cortex. [source] Posterior cingulate activation during moral dilemma in adolescentsHUMAN BRAIN MAPPING, Issue 8 2008Jesus Pujol Abstract Neuroimaging research examining correlates of adolescent behavioral maturation has focused largely on issues related to higher cognitive development. Currently few studies have explored neural correlates of emotional reactivity in adolescent groups. In this study, we sought to examine the nature of posterior cingulate activation during situations of moral dilemma in normal adolescents. We focused on this region because of emerging evidence that suggests its role in emotionally self-relevant mental processing. Ten healthy teenagers, aged from 14 to 16 years, underwent three fMRI sequences designed to examine (i) brain responses during moral dilemma; (ii) brain responses during passive viewing of the moral dilemma outcome; and (iii); "deactivation" during a simple cognitive task compared with resting-state activity. Our main finding was that during moral dilemma, all subjects showed significant activation of the posterior cingulate cortex, and more variable activation of the medial frontal cortex and angular gyrus. Interestingly, these findings were replicated in each subject using the passive viewing task, suggesting that the previous pattern was not specific to moral reasoning or decision making. Finally, six of the ten subjects showed deactivation of the same posterior cingulate region during the cognitive task, indicating some commonality of function between posterior cingulate activity during moral dilemmas and rest. We propose that these posterior cingulate changes may relate to basic neuronal activities associated with processing self-relevant emotional stimuli. Given the high single-subject reproducibility of posterior cingulate activations, our findings may contribute to further characterize adolescent emotional reactivity in developmental neuroimaging studies. Hum Brain Mapp, 2008. © 2007 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] The effect of stimulus intensity on brain responses evoked by transcranial magnetic stimulationHUMAN BRAIN MAPPING, Issue 3 2004Soile Komssi Abstract To better understand the neuronal effects of transcranial magnetic stimulation (TMS), we studied how the TMS-evoked brain responses depend on stimulation intensity. We measured electroencephalographic (EEG) responses to motor-cortex TMS, estimated the intensity dependence of the overall brain response, and compared it to a theoretical model for the intensity dependence of the TMS-evoked neuronal activity. Left and right motor cortices of seven volunteers were stimulated at intensities of 60, 80, 100, and 120% of the motor threshold (MT). A figure-of-eight coil (diameter of each loop 4 cm) was used for focal stimulation. EEG was recorded with 60 scalp electrodes. The intensity of 60% of MT was sufficient to produce a distinct global mean field amplitude (GMFA) waveform in all subjects. The GMFA, reflecting the overall brain response, was composed of four peaks, appearing at 15 ± 5 msec (Peak I), 44 ± 10 msec (II), 102 ± 18 msec (III), and 185 ± 13 msec (IV). The peak amplitudes depended nonlinearly on intensity. This nonlinearity was most pronounced for Peaks I and II, whose amplitudes appeared to sample the initial part of the sigmoid-shaped curve modeling the strength of TMS-evoked neuronal activity. Although the response amplitude increased with stimulus intensity, scalp distributions of the potential were relatively similar for the four intensities. The results imply that TMS is able to evoke measurable brain activity at low stimulus intensities, probably significantly below 60% of MT. The shape of the response-stimulus intensity curve may be an indicator of the activation state of the brain. Hum. Brain Mapp. 21:154,164, 2004. © 2004 Wiley-Liss, Inc. [source] Citicoline affects appetite and cortico-limbic responses to images of high-calorie foodsINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 1 2010William D.S. Killgore PhD Abstract Objective: Cytidine-5,-diphosphocholine (citicoline) has a variety of cognitive enhancing, neuroprotective, and neuroregenerative properties. In cocaine-addicted individuals, citicoline has been shown to increase brain dopamine levels and reduce cravings. The effects of this compound on appetite, food cravings, and brain responses to food are unknown. Method: We compared the effects of treatment with Cognizin® citicoline (500 mg/day versus 2,000 mg/day) for 6 weeks on changes in appetite ratings, weight, and cortico-limbic responses to images of high-calorie foods using functional magnetic resonance imaging (fMRI). Results: After 6 weeks, there was no significant change in weight status, although significant declines in appetite ratings were observed for the 2,000 mg/day group. The higher dose group also showed significant increases in functional brain responses to food stimuli within the amygdala, insula, and lateral orbitofrontal cortex. Increased activation in these regions correlated with declines in appetite ratings. Discussion: These preliminary findings suggest a potential usefulness of citicoline in modulating appetite, but further research is warranted. © 2009 by Wiley Periodicals, Inc. Int J Eat Disord 2010 [source] IL-10 and IL-4 regulate type-I and type-II IL-1 receptors expression on IL-1,-activated mouse primary astrocytesJOURNAL OF NEUROCHEMISTRY, Issue 4 2001F. Pousset When activated by its ligand, the interleukin receptor type I (IL-1RI) transduces signals in cooperation with the IL-1 receptor accessory protein (IL-1RacP). In contrast, IL-1RII functions as a decoy receptor without participating in IL-1 signalling. Brain astrocytes are cellular targets of IL-1 and play a pivotal role in brain responses to inflammation. The regulation of IL-1 receptors on astrocytes by anti-inflammatory cytokines such as IL-4 and IL-10 has not been studied, despite its importance for understanding the way these cells respond to IL-1. Using RT-PCR, we first showed that the expression of IL-1RI and IL-1RII, but not IL-1RacP, mRNAs are up-regulated by IL-1, in a time-dependent manner. Using a radioligand binding technique, we then showed that astrocytes display an equivalent number of IL-1RI and IL-1RII. IL-1, decreases the number of IL-1RI binding sites, whereas it increases those of IL-1RII. IL-4 and IL-10 both up-regulate IL-1RII IL-1,-induced, but only IL-4 does so for IL-1RI. At the protein level, IL-4 and IL-10 dramatically reverse the ability of IL-1, to inhibit expression of IL-1RI but neither affects the ability of IL-1, to enhance the number of IL-1RII. Collectively, these results establish the existence of receptor cross-talk between pro- and anti-inflammatory cytokines on a critical type of cell that regulates inflammatory events in the brain. [source] Event-Related fMRI of Inhibitory Control in the Predominantly Inattentive and Combined Subtypes of ADHDJOURNAL OF NEUROIMAGING, Issue 3 2009Mary V. Solanto PhD ABSTRACT BACKGROUND AND PURPOSE To examine the neurophysiological basis for the pronounced differences in hyperactivity and impulsiveness that distinguish the predominantly inattentive type of attention-deficit/hyperactivity disorder (ADHD-PI) from the combined type of the disorder (ADHD-C). METHODS Event-related brain responses to a go/no-go test of inhibitory control were measured with functional magnetic resonance imaging (fMRI) in 11 children with ADHD-C and 9 children with ADHD-PI, aged 7 to 13 years, who were matched for age, sex, and intelligence. RESULTS There were no significant group differences in task performance. Children with ADHD-C and ADHD-PI activated overlapping regions of right inferior frontal gyrus, right superior temporal lobe, and left inferior parietal lobe during inhibitory control. However, the magnitude of the activation in the temporal and parietal regions, as well as in the bilateral middle frontal gyrus, was greater in children with ADHD-PI than those with ADHD-C. Conversely, children with ADHD-C activated bilateral medial occipital lobe to a greater extent than children with ADHD-PI. CONCLUSIONS The results provide preliminary evidence that phenotypic differences between the ADHD-C and ADHD-PI subtypes are associated with differential activation of regions that have previously been implicated in the pathophysiology of ADHD and are thought to mediate executive and attentional processes. [source] Bladder control, urgency, and urge incontinence: Evidence from functional brain imaging,NEUROUROLOGY AND URODYNAMICS, Issue 6 2008Derek Griffiths Abstract Aim To review brain imaging studies of bladder control in subjects with normal control and urge incontinence; to define a simple model of supraspinal bladder control; and to propose a neural correlate of urgency and possible origins of urge incontinence. Methods Review of published reports of brain imaging relevant to urine storage, and secondary analyses of our own recent observations. Results In a simple model of normal urine storage, bladder and urethral afferents received in the periaqueductal gray (PAG) are mapped in the insula, forming the basis of sensation; the anterior cingulate gyrus (ACG) provides monitoring and control; the prefrontal cortex makes voiding decisions. The net result, as the bladder fills, is inhibition of the pontine micturition center (PMC) and of voiding, together with gradual increase in insular response, corresponding to increasing desire to void. In urge-incontinent subjects, brain responses differ. At large bladder volumes and strong sensation, but without detrusor overactivity (DO), most cortical responses become exaggerated, especially in ACG. This may be both a learned reaction to previous incontinence episodes and the neural correlate of urgency. The neural signature of DO itself seems to be prefrontal deactivation. Possible causes of urge incontinence include dysfunction of prefrontal cortex or limbic system, suggested by weak responses and/or deactivation, as well as abnormal afferent signals or re-emergence of infantile reflexes. Conclusions Bladder control depends on an extensive network of brain regions. Dysfunction in various parts may contribute to urge incontinence, suggesting that there are different phenotypes requiring different treatments. Neurourol. Urodynam. 27:466,474, 2008. © 2007 Wiley-Liss, Inc. [source] Dopamine gene predicts the brain's response to dopaminergic drugEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Michael X Cohen Abstract Dopamine is critical for reward-based decision making, yet dopaminergic drugs can have opposite effects in different individuals. This apparent discrepancy can be accounted for by hypothesizing an ,inverted-U' relationship, whereby the effect of dopamine agents depends on baseline dopamine system functioning. Here, we used functional MRI to test the hypothesis that genetic variation in the expression of dopamine D2 receptors in the human brain predicts opposing dopaminergic drug effects during reversal learning. We scanned 22 subjects while they engaged in a feedback-based reversal learning task. Ten subjects had an allele on the Taq1A DRD2 gene, which is associated with reduced dopamine receptor concentration and decreased neural responses to rewards (A1+ subjects). Subjects were scanned twice, once on placebo and once on cabergoline, a D2 receptor agonist. Consistent with an inverted-U relationship between the DRD2 polymorphism and drug effects, cabergoline increased neural reward responses in the medial orbitofrontal cortex, cingulate cortex and striatum for A1+ subjects but decreased reward responses in these regions for A1, subjects. In contrast, cabergoline decreased task performance and fronto-striatal connectivity in A1+ subjects but had the opposite effect in A1, subjects. Further, the drug effect on functional connectivity predicted the drug effect on feedback-guided learning. Thus, individual variability in how dopaminergic drugs affect the brain reflects genetic disposition. These findings may help to explain the link between genetic disposition and risk for addictive disorders. [source] Co-induction of activity-dependent genes in songbirdsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2005Tarciso A. F. Velho Abstract Song behavior in songbirds induces the expression of activity-dependent genes in brain areas involved in perceptual processing, production and learning of song. This genomic response is thought to represent a link between neuronal activation and long-term changes in song-processing circuits of the songbird brain. Here we demonstrate that Arc, an activity-regulated gene whose product has dendritic localization and is associated with synaptic plasticity, is rapidly induced by song in the brain of zebra finches. We show that, in the context of song auditory stimulation, Arc expression is induced in several telencephalic auditory areas, most prominently the caudomedial nidopallium and mesopallium, whereas in the context of singing, Arc is also induced in song control areas, namely nucleus HVC, used as a proper name, the robust nucleus of the arcopallium and the interface nucleus of the nidopallium. We also show that song-induced Arc expression co-localizes at the cellular level with those of the transcriptional regulators zenk and c-fos, and that the song induction of these three genes is dependent on activation of the mitogen-activated protein kinase signaling pathway. These findings provide evidence for an involvement of Arc in the brain's response to birdsong. They also demonstrate that genes representing distinct genomic and cellular regulatory programs, namely early effectors and transcription factors, are co-activated in the same neuronal cells by a naturally learned stimulus. [source] Inflammation: A new candidate in modulating adult neurogenesisJOURNAL OF NEUROSCIENCE RESEARCH, Issue 6 2008Sulagna Das Abstract Any pathological perturbation to the brain provokes a cascade of molecular and cellular events, which manifests in the form of microglial activation and release of various proinflammatory molecules. This eventually culminates in a profound neuroinflammatory reaction that characterizes the brain's response to stress, injury, or infection. The inflammatory cascade is an attempt by the system to eliminate the challenge imposed on the brain, clear the system of the dead and damaged neurons, and rescue the normal functioning of this vital organ. However, during the process of microglial activation, the proinflammatory mediators released exert certain detrimental effects, and neural stem cells and progenitor cells are likely to be affected. Here we review how the proliferation, maturation, and migration of the neural stem cells are modulated under such an inflammatory condition. The fate of the noncommitted neural stem cells and its differentiation potency are often under strict regulation, and these proinflammatory mediators seem to disrupt this critical balance and finely tune the neurogenesis pattern in the two niches of neurogenesis, the subventricular zone and the subgranular zone of the hippocampus. Moreover, the migration ability of these stem cells, which is important for localization to the proper site, is also affected in a major way by the chemokines released following inflammation. © 2007 Wiley-Liss, Inc. [source] | ||||||||||||||||