Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Medical Sciences (75)
- Neurosciences (65)
- Psychology (65)
- Social and Behavioral Sciences (65)
- Medical Specialties (19)
-
- Physical Therapy (18)
- Rehabilitation and Therapy (18)
- Pediatrics (17)
- Biostatistics (12)
- Epidemiology (12)
- Physical Sciences and Mathematics (12)
- Public Health (12)
- Statistics and Probability (12)
- Medical Biophysics (9)
- Communication Sciences and Disorders (1)
- Dentistry (1)
- Medical Physiology (1)
- Obstetrics and Gynecology (1)
- Pharmacy and Pharmaceutical Sciences (1)
- Surgery (1)
- Publication Year
Articles 121 - 135 of 135
Full-Text Articles in Medicine and Health Sciences
Dissociating Speech Perception And Comprehension At Reduced Levels Of Awareness, Matthew H Davis, Martin R Coleman, Anthony R Absalom, Jennifer M Rodd, Ingrid Johnsrude, Basil F Matta, Adrian M Owen, David K Menon
Dissociating Speech Perception And Comprehension At Reduced Levels Of Awareness, Matthew H Davis, Martin R Coleman, Anthony R Absalom, Jennifer M Rodd, Ingrid Johnsrude, Basil F Matta, Adrian M Owen, David K Menon
Brain and Mind Institute Researchers' Publications
We used functional MRI and the anesthetic agent propofol to assess the relationship among neural responses to speech, successful comprehension, and conscious awareness. Volunteers were scanned while listening to sentences containing ambiguous words, matched sentences without ambiguous words, and signal-correlated noise (SCN). During three scanning sessions, participants were nonsedated (awake), lightly sedated (a slowed response to conversation), and deeply sedated (no conversational response, rousable by loud command). Bilateral temporal-lobe responses for sentences compared with signal-correlated noise were observed at all three levels of sedation, although prefrontal and premotor responses to speech were absent at the deepest level of sedation. Additional …
Human Parietal "Reach Region" Primarily Encodes Intrinsic Visual Direction, Not Extrinsic Movement Direction, In A Visual Motor Dissociation Task., Juan Fernandez-Ruiz, Herbert C Goltz, Joseph F X Desouza, Tutis Vilis, J Douglas Crawford
Human Parietal "Reach Region" Primarily Encodes Intrinsic Visual Direction, Not Extrinsic Movement Direction, In A Visual Motor Dissociation Task., Juan Fernandez-Ruiz, Herbert C Goltz, Joseph F X Desouza, Tutis Vilis, J Douglas Crawford
Brain and Mind Institute Researchers' Publications
Posterior parietal cortex (PPC) participates in the planning of visuospatial behaviors, including reach movements, in gaze-centered coordinates. It is not known if these representations encode the visual goal in retinal coordinates, or the movement direction relative to gaze. Here, by dissociating the intrinsic retinal stimulus from the extrinsic direction of movement, we show that PPC employs a visual code. Using delayed pointing and event-related functional magnetic resonance imaging, we identified a cluster of PPC regions whose activity was topographically (contralaterally) related to the direction of the planned movement. We then switched the normal visual-motor spatial relationship by adapting subjects to …
Do Vegetative Patients Retain Aspects Of Language Comprehension? Evidence From Fmri, Martin R Coleman, Jennifer M Rodd, Matthew H Davis, Ingrid Johnsrude, David K Menon, John D Pickard, Adrian M Owen
Do Vegetative Patients Retain Aspects Of Language Comprehension? Evidence From Fmri, Martin R Coleman, Jennifer M Rodd, Matthew H Davis, Ingrid Johnsrude, David K Menon, John D Pickard, Adrian M Owen
Brain and Mind Institute Researchers' Publications
A diagnosis of vegetative state is made if a patient demonstrates no evidence of awareness of self or environment, no evidence of sustained, reproducible, purposeful or voluntary behavioural response to sensory stimuli and critically no evidence of language comprehension. For those patients who retain peripheral motor function, rigorous behavioural assessment is usually able to determine retained function. However, some patients do not retain the ability to respond overtly to command and it is becoming increasingly accepted that assessment of these patients should include techniques, which do not rely on any 'motor action' on the part of the patient. Here, we …
Spontaneous Low-Frequency Fluctuations In The Bold Signal In Schizophrenic Patients: Anomalies In The Default Network, Robyn L Bluhm, Jodi Miller, Ruth A Lanius, Elizabeth A Osuch, Kristine Boksman, R W J Neufeld, Jean Theberge, Betsy Schaefer, Peter Williamson
Spontaneous Low-Frequency Fluctuations In The Bold Signal In Schizophrenic Patients: Anomalies In The Default Network, Robyn L Bluhm, Jodi Miller, Ruth A Lanius, Elizabeth A Osuch, Kristine Boksman, R W J Neufeld, Jean Theberge, Betsy Schaefer, Peter Williamson
Department of Medicine Publications
Spontaneous low-frequency fluctuations in the blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (MRI) signal have been shown to reflect neural synchrony between brain regions. A "default network" of spontaneous low-frequency fluctuations has been described in healthy volunteers during stimulus-independent thought. Negatively correlated with this network are regions activated during attention-demanding tasks. Both these networks involve brain regions and functions that have been linked with schizophrenia in previous research. The present study examined spontaneous slow fluctuations in the BOLD signal at rest, as measured by correlation with low-frequency oscillations in the posterior cingulate, in 17 schizophrenic patients, and 17 comparable …
Alcohol Slows Interhemispheric Transmission, Increases The Flash-Lag Effect, And Prolongs Masking: Evidence For A Slowing Of Neural Processing And Transmission., Sarah A Khan, Brian Timney
Alcohol Slows Interhemispheric Transmission, Increases The Flash-Lag Effect, And Prolongs Masking: Evidence For A Slowing Of Neural Processing And Transmission., Sarah A Khan, Brian Timney
Brain and Mind Institute Researchers' Publications
While the alcohol literature is extensive, relatively little addresses the relationship between physiological effects and behavioural changes. Using the visual system as a model, we examined alcohol's influence on neural temporal processing as a potential means for alcohol's effects. We did this by using tasks that provided a measure of processing speed: Poffenberger paradigm, flash-lag, and backward masking. After moderate alcohol, participants showed longer interhemispheric transmission times, larger flash-lags, and prolonged masking. Our data are consistent with the view that alcohol slows neural processing, and provide support for a reduction in processing efficiency underlying alcohol-induced changes in temporal visual processing.
Representation Of Head-Centric Flow In The Human Motion Complex., Jeroen Goossens, Sean P Dukelow, Ravi S Menon, Tutis Vilis, Albert V Van Den Berg
Representation Of Head-Centric Flow In The Human Motion Complex., Jeroen Goossens, Sean P Dukelow, Ravi S Menon, Tutis Vilis, Albert V Van Den Berg
Brain and Mind Institute Researchers' Publications
Recent neuroimaging studies have identified putative homologs of macaque middle temporal area (area MT) and medial superior temporal area (area MST) in humans. Little is known about the integration of visual and nonvisual signals in human motion areas compared with monkeys. Through extra-retinal signals, the brain can factor out the components of visual flow on the retina that are induced by eye-in-head and head-in-space rotations and achieve a representation of flow relative to the head (head-centric flow) or body (body-centric flow). Here, we used functional magnetic resonance imaging to test whether extra-retinal eye-movement signals modulate responses to visual flow in …
The Neural Mechanisms Of Speech Comprehension: Fmri Studies Of Semantic Ambiguity, Jennifer M Rodd, Matthew H Davis, Ingrid Johnsrude
The Neural Mechanisms Of Speech Comprehension: Fmri Studies Of Semantic Ambiguity, Jennifer M Rodd, Matthew H Davis, Ingrid Johnsrude
Brain and Mind Institute Researchers' Publications
A number of regions of the temporal and frontal lobes are known to be important for spoken language comprehension, yet we do not have a clear understanding of their functional role(s). In particular, there is considerable disagreement about which brain regions are involved in the semantic aspects of comprehension. Two functional magnetic resonance studies use the phenomenon of semantic ambiguity to identify regions within the fronto-temporal language network that subserve the semantic aspects of spoken language comprehension. Volunteers heard sentences containing ambiguous words (e.g. 'the shell was fired towards the tank') and well-matched low-ambiguity sentences (e.g. 'her secrets were written …
Learning To Like: A Role For Human Orbitofrontal Cortex In Conditioned Reward, Sylvia M L Cox, Alexandre Andrade, Ingrid Johnsrude
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 …
Somatotopic Representation Of Action Words In Human Motor And Premotor Cortex, Olaf Hauk, Ingrid Johnsrude, Friedemann Pulvermüller
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 …
Gaze-Centered Updating Of Visual Space In Human Parietal Cortex., W Pieter Medendorp, Herbert C Goltz, Tutis Vilis, J Douglas Crawford
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.
Effects Of Ethanol On Anti-Saccade Task Performance., Sarah A Khan, Kristen Ford, Brian Timney, Stefan Everling
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 …
Can Meaningful Effective Connectivities Be Obtained Between Auditory Cortical Regions?, M S Gonçalves, D A Hall, Ingrid Johnsrude, M P Haggard
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 …
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
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 …
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
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 …
Identifying Global Anatomical Differences: Deformation-Based Morphometry, J Ashburner, C Hutton, R Frackowiak, Ingrid Johnsrude, C Price, K Friston
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.