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Articles 811 - 827 of 827

Full-Text Articles in Neurosciences

A Critical Role For Kalirin In Ngf Signaling Through Trka, Kausik Chakrabarti, Rong Lin, Noraisha I. Schiller, Yanping Wang, David Koubi, Ying-Xin Fan, Brian B. Rudkin, Gibbes R. Johnson, Martin R. Schiller Jun 2005

A Critical Role For Kalirin In Ngf Signaling Through Trka, Kausik Chakrabarti, Rong Lin, Noraisha I. Schiller, Yanping Wang, David Koubi, Ying-Xin Fan, Brian B. Rudkin, Gibbes R. Johnson, Martin R. Schiller

Life Sciences Faculty Research

Kalirin is a multidomain guanine nucleotide exchange factor (GEF) that activates Rho proteins, inducing cytoskeletal rearrangement in neurons. Although much is known about the effects of Kalirin on Rho GTPases and neuronal morphology, little is known about the association of Kalirin with the receptor/signaling systems that affect neuronal morphology. Our experiments demonstrate that Kalirin binds to and colocalizes with the TrkA neurotrophin receptor in neurons. In PC12 cells, inhibition of Kalirin expression using antisense RNA decreased nerve growth factor (NGF)-induced TrkA autophosphorylation and process extension. Kalirin overexpression potentiated neurotrophin-stimulated TrkA autophosphorylation and neurite outgrowth in PC12 cells at a low …

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Learning To Like: A Role For Human Orbitofrontal Cortex In Conditioned Reward, Sylvia M L Cox, Alexandre Andrade, Ingrid Johnsrude Mar 2005

Learning To Like: A Role For Human Orbitofrontal Cortex In Conditioned Reward, Sylvia M L Cox, Alexandre Andrade, Ingrid Johnsrude

Brain and Mind Institute Researchers' Publications

A great deal of human behavior and motivation is based on the intrinsic emotional significance of rewarding or aversive events, as well as on the associations formed between such emotional events and concurrent environmental stimuli. Recent functional neuroimaging studies have implicated the ventral striatum, orbitofrontal cortex (OFC), and amygdala in the representation of reward values and/or in the anticipation of rewarding events. Here, we use functional magnetic resonance imaging to compare brain activation during the presentation of reward with that during presentation of (conditioned) stimuli that have been paired previously with reward. Specifically, we aimed to investigate conditioned reward in …

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A Contralateral Preference In The Lateral Occipital Area: Sensory And Attentional Mechanisms., Matthias Niemeier, Herbert C Goltz, Anil Kuchinad, Douglas B Tweed, Tutis Vilis Mar 2005

A Contralateral Preference In The Lateral Occipital Area: Sensory And Attentional Mechanisms., Matthias Niemeier, Herbert C Goltz, Anil Kuchinad, Douglas B Tweed, Tutis Vilis

Brain and Mind Institute Researchers' Publications

Here we examined the level of the lateral occipital (LO) area within the processing stream of the ventral visual cortex. An important determinant of an area's level of processing is whether it codes visual elements on both sides of the visual field, as do higher visual areas, or prefers those in the contralateral visual field, as do early visual areas. The former would suggest that LO, on one side, combines bilateral visual elements into a whole, while the latter suggests that it codes only the parts of forms. We showed that LO has a relative preference for visual objects in …

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Somatotopic Representation Of Action Words In Human Motor And Premotor Cortex, Olaf Hauk, Ingrid Johnsrude, Friedemann Pulvermüller Jan 2004

Somatotopic Representation Of Action Words In Human Motor And Premotor Cortex, Olaf Hauk, Ingrid Johnsrude, Friedemann Pulvermüller

Brain and Mind Institute Researchers' Publications

Since the early days of research into language and the brain, word meaning was assumed to be processed in specific brain regions, which most modern neuroscientists localize to the left temporal lobe. Here we use event-related fMRI to show that action words referring to face, arm, or leg actions (e.g., to lick, pick, or kick), when presented in a passive reading task, differentially activated areas along the motor strip that either were directly adjacent to or overlapped with areas activated by actual movement of the tongue, fingers, or feet. These results demonstrate that the referential meaning of action words has …

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Gaze-Centered Updating Of Visual Space In Human Parietal Cortex., W Pieter Medendorp, Herbert C Goltz, Tutis Vilis, J Douglas Crawford Jul 2003

Gaze-Centered Updating Of Visual Space In Human Parietal Cortex., W Pieter Medendorp, Herbert C Goltz, Tutis Vilis, J Douglas Crawford

Brain and Mind Institute Researchers' Publications

Single-unit recordings have identified a region in the posterior parietal cortex (PPC) of the monkey that represents and updates visual space in a gaze-centered frame. Here, using event-related functional magnetic resonance imaging, we identified an analogous bilateral region in the human PPC that shows contralateral topography for memory-guided eye movements and arm movements. Furthermore, when eye movements reversed the remembered horizontal target location relative to the gaze fixation point, this PPC region exchanged activity across the two cortical lobules. This shows that the human PPC dynamically updates the spatial goals for action in a gaze-centered frame.

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The Lateral Occipital Complex Subserves The Perceptual Persistence Of Motion-Defined Groupings., Susanne Ferber, G Keith Humphrey, Tutis Vilis Jul 2003

The Lateral Occipital Complex Subserves The Perceptual Persistence Of Motion-Defined Groupings., Susanne Ferber, G Keith Humphrey, Tutis Vilis

Brain and Mind Institute Researchers' Publications

How are the bits and pieces of retinal information assembled and integrated to form the coherent objects that we see? One long-established principle is that elements that move as a group are linked together. For instance a fragmented line-drawing of an object, placed on a background of randomly distributed short lines, can be impossible to see. But if the object moves relative to the background, its shape is instantly recognized. Even after the motion stops, the percept of the object persists briefly before it fades into the background of random lines. Where in the brain does the percept of the …

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Residency Program At Michael E Debakey Department Of Surgery, Baylor College Of Medicine, F Charles Brunicardi Jun 2003

Residency Program At Michael E Debakey Department Of Surgery, Baylor College Of Medicine, F Charles Brunicardi

Faculty, Staff and Students Publications

No abstract provided.

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Effects Of Ethanol On Anti-Saccade Task Performance., Sarah A Khan, Kristen Ford, Brian Timney, Stefan Everling May 2003

Effects Of Ethanol On Anti-Saccade Task Performance., Sarah A Khan, Kristen Ford, Brian Timney, Stefan Everling

Brain and Mind Institute Researchers' Publications

It has been shown that saccade-related neurons in the superior colliculus (SC) display an increased level of prestimulus activity and a higher stimulus-related burst in action potentials preceding direction errors in the anti-saccade task compared with correct anti-saccades. From this, it has been hypothesized that errors occur when the incoming visual signal in the SC passes a threshold and triggers a reflexive saccade. This hypothesis predicts that an attenuated visual signal will reduce the number of direction errors. Since ethanol has been shown to have a suppressive effect on cortical visual event-related potentials (ERPs), the purpose of the present study …

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Hierarchical Processing In Spoken Language Comprehension., Matthew H Davis, Ingrid Johnsrude Apr 2003

Hierarchical Processing In Spoken Language Comprehension., Matthew H Davis, Ingrid Johnsrude

Brain and Mind Institute Researchers' Publications

Understanding spoken language requires a complex series of processing stages to translate speech sounds into meaning. In this study, we use functional magnetic resonance imaging to explore the brain regions that are involved in spoken language comprehension, fractionating this system into sound-based and more abstract higher-level processes. We distorted English sentences in three acoustically different ways, applying each distortion to varying degrees to produce a range of intelligibility (quantified as the number of words that could be reported) and collected whole-brain echo-planar imaging data from 12 listeners using sparse imaging. The blood oxygenation level-dependent signal correlated with intelligibility along the …

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Relationships Between Human Auditory Cortical Structure And Function, Deborah A Hall, Heledd C Hart, Ingrid Johnsrude Jan 2003

Relationships Between Human Auditory Cortical Structure And Function, Deborah A Hall, Heledd C Hart, Ingrid Johnsrude

Brain and Mind Institute Researchers' Publications

The human auditory cortex comprises multiple areas, largely distributed across the supratemporal plane, but the precise number and configuration of auditory areas and their functional significance have not yet been clearly established. In this paper, we discuss recent research concerning architectonic and functional organisation within the human auditory cortex, as well as architectonic and neurophysiological studies in non-human species, which can provide a broad conceptual framework for interpreting functional specialisation in humans. We review the pattern in human auditory cortex of the functional responses to various acoustic cues, such as frequency, pitch, sound level, temporal variation, motion and spatial location, …

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Spectral And Temporal Processing In Human Auditory Cortex, Deborah A Hall, Ingrid Johnsrude, Mark P Haggard, Alan R Palmer, Michael A Akeroyd, A Quentin Summerfield Feb 2002

Spectral And Temporal Processing In Human Auditory Cortex, Deborah A Hall, Ingrid Johnsrude, Mark P Haggard, Alan R Palmer, Michael A Akeroyd, A Quentin Summerfield

Brain and Mind Institute Researchers' Publications

Hierarchical processing suggests that spectrally and temporally complex stimuli will evoke more activation than do simple stimuli, particularly in non-primary auditory fields. This hypothesis was tested using two tones, a single frequency tone and a harmonic tone, that were either static or frequency modulated to create four stimuli. We interpret the location of differences in activation by drawing comparisons between fMRI and human cytoarchitectonic data, reported in the same brain space. Harmonic tones produced more activation than single tones in right Heschl's gyrus (HG) and bilaterally in the lateral supratemporal plane (STP). Activation was also greater to frequency-modulated tones than …

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Can Meaningful Effective Connectivities Be Obtained Between Auditory Cortical Regions?, M S Gonçalves, D A Hall, Ingrid Johnsrude, M P Haggard Dec 2001

Can Meaningful Effective Connectivities Be Obtained Between Auditory Cortical Regions?, M S Gonçalves, D A Hall, Ingrid Johnsrude, M P Haggard

Brain and Mind Institute Researchers' Publications

Structural equation modeling (SEM) of neuroimaging data can be evaluated both for the goodness of fit of the model and for the strength of path coefficients (as an index of effective connectivity). SEM of auditory fMRI data is made difficult by the necessary sparse temporal sampling of the time series (to avoid contamination of auditory activation by the response to scanner noise) and by the paucity of well-defined anatomical information to constrain the functional model. We used SEM (i.e., a model incorporating latent variables) to investigate how well fMRI data in four adjacent cortical fields can be described as an …

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Eye Position Sense Contributes To The Judgement Of Slant., F M James, S Whitehead, G K Humphrey, M S Banks, T Vilis Jan 2001

Eye Position Sense Contributes To The Judgement Of Slant., F M James, S Whitehead, G K Humphrey, M S Banks, T Vilis

Brain and Mind Institute Researchers' Publications

We measured monocular judgements of the slant of a cube face while varying eye position in the absence of stereoscopic and external lighting cues. Errors were found to be small, only 10% on average of the cube's eccentricity. Two factors appear to have contributed approximately equally to this error: an underestimate of cube slant as seen by the eye and an underestimate of eye position. When prism adaptation altered the sensed eye position, the pattern of slant judgements changed to reflect the altered sense of eye position.

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Eye Position Signal Modulates A Human Parietal Pointing Region During Memory-Guided Movements., J F Desouza, S P Dukelow, J S Gati, R S Menon, R A Andersen, T Vilis Aug 2000

Eye Position Signal Modulates A Human Parietal Pointing Region During Memory-Guided Movements., J F Desouza, S P Dukelow, J S Gati, R S Menon, R A Andersen, T Vilis

Brain and Mind Institute Researchers' Publications

Using functional magnetic resonance imaging, we examined the signal in parietal regions that were selectively activated during delayed pointing to flashed visual targets and determined whether this signal was dependent on the fixation position of the eyes. Delayed pointing activated a bilateral parietal area in the intraparietal sulcus (rIPS), rostral/anterior to areas activated by saccades. During right-hand pointing to centrally located targets, the left rIPS region showed a significant increase in activation when the eye position was rightward compared with leftward. As expected, activation in motor cortex showed no modulation when only eye position changed. During pointing to retinotopically identical …

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Navigation-Related Structural Change In The Hippocampi Of Taxi Drivers, E A Maguire, D G Gadian, Ingrid Johnsrude, C D Good, J Ashburner, R S Frackowiak, C D Frith Apr 2000

Navigation-Related Structural Change In The Hippocampi Of Taxi Drivers, E A Maguire, D G Gadian, Ingrid Johnsrude, C D Good, J Ashburner, R S Frackowiak, C D Frith

Brain and Mind Institute Researchers' Publications

Structural MRIs of the brains of humans with extensive navigation experience, licensed London taxi drivers, were analyzed and compared with those of control subjects who did not drive taxis. The posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects. A more anterior hippocampal region was larger in control subjects than in taxi drivers. Hippocampal volume correlated with the amount of time spent as a taxi driver (positively in the posterior and negatively in the anterior hippocampus). These data are in accordance with the idea that the posterior hippocampus stores a spatial representation of the environment …

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Identifying Global Anatomical Differences: Deformation-Based Morphometry, J Ashburner, C Hutton, R Frackowiak, Ingrid Johnsrude, C Price, K Friston Jan 1998

Identifying Global Anatomical Differences: Deformation-Based Morphometry, J Ashburner, C Hutton, R Frackowiak, Ingrid Johnsrude, C Price, K Friston

Brain and Mind Institute Researchers' Publications

The aim of this paper is to illustrate a method for identifying macroscopic anatomical differences among the brains of different populations of subjects. The method involves spatially normalizing the structural MR images of a number of subjects so that they all conform to the same stereotactic space. Multivariate statistics are then applied to the parameters describing the estimated nonlinear deformations that ensue. To illustrate the method, we compared the gross morphometry of male and female subjects. We also assessed brain asymmetry, the effect of handedness, and interactions among these effects.

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Right Medial Temporal-Lobe Contribution To Object-Location Memory, B Milner, Ingrid Johnsrude, J Crane Oct 1997

Right Medial Temporal-Lobe Contribution To Object-Location Memory, B Milner, Ingrid Johnsrude, J Crane

Brain and Mind Institute Researchers' Publications

An important aspect of normal human memory, and one humans share with many other species, is the ability to remember the location of objects in their environment. There is by now strong evidence from the study of epileptic patients undergoing brain surgery that right temporal-lobe lesions that encroach extensively upon the hippocampal and parahippocampal gyrus impair the delayed, but not the immediate, recall of the location of objects within a random array. These findings have now been extended to a multiple-trial, spatial-array learning task; by including not only patients tested after unilateral anterior temporal lobectomy but also those with a …

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