bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic components of functional connectivity in the brain: The heritability of synchronization likelihood
Authors: Posthuma Danielle , de Geus Eco J.C. , Mulder Elles J.C.M. , Smit Dirk J.A. , Boomsma Dorret I. , Stam Cornelis J. 
Published: May 2005

AbstractCognitive functions require the integrated activity of multiple specialized, distributed brain areas. Such functional coupling depends on the existence of anatomical connections between the various brain areas as well as physiological processes whereby the activity in one area influences the activity in another area. Recently, the Synchronization Likelihood (SL) method was developed as a general method to study both linear and nonlinear aspects of coupling. In the present study the genetic architecture of the SL in different frequency bands was investigated. Using a large genetically informative sample of 569 subjects from 282 extended twin families we found that the SL is moderately to highly heritable (41–67%) especially in the alpha frequency (8–13 Hz) range. This index of functional connectivity of the brain has been associated with a number of pathological states of the brain. The significant heritability found here suggests that SL can be used to examine the genetic susceptibility to these conditions. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Attentional modulation of perceptual grouping in human visual cortex: ERP studies
Authors: Han Shihui , Jiang Yi , Mao Lihua , Humphreys Glyn W. , Qin Jungang 
Published: May 2005

AbstractWe sought to identify the neural substrates underlying perceptual grouping, and examined whether the grouping‐related neural activities are modulated by task relevance and attention by recording high‐density event‐related potentials (ERPs). Participants were presented with stimulus arrays, in which local elements were either evenly distributed or grouped into rows or columns by proximity or similarity, and had to discriminate orientations of the perceptual groups, or to identify the colors of dots around stimulus displays or of the fixation cross. We found that proximity grouping was indexed by a positive activity over the medial occipital cortex with a peak latency of about 100 ms after stimulus onset (Pd100), whereas grouping by similarity of shape was reflected in a negative activity with longer latency over the occipito‐temporal areas. Dipole modeling based on a realistic boundary element head model localized the Pd100 to the right calcarine cortex. Moreover, we showed that the grouping‐related activities were weakened when stimulus arrays were of low task relevance and fell outside an attended area of field. The results suggest that human calcarine cortex is engaged in early grouping operations defined by proximity, reinforcing the previous fMRI findings. Moreover, our ERP results indicate that the neural bases underlying perceptual grouping in human visual cortex can be modulated by task relevance and attention as early as 100 ms after sensory stimulation. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Statistical parametric maps in functional imaging: A general linear approach
Authors: Friston K. J. , Holmes A. P. , Worsley K. J. , Poline J.‐P. , Frith C. D. , Frackowiak R. S. J. 
Published: May 2005

AbstractStatistical parametric maps are spatially extended statistical processes that are used to test hypotheses about regionally specific effects in neuroimaging data. The most established sorts of statistical parametric maps (e.g., Friston et al. [1991]: J Cereb Blood Flow Metab 11:690–699; Worsley et al. [1992]: J Cereb Blood Flow Metab 12:900–918) are based on linear models, for example ANCOVA, correlation coefficients and t tests. In the sense that these examples are all special cases of the general linear model it should be possible to implement them (and many others) within a unified framework. We present here a general approach that accomodates most forms of experimental layout and ensuing analysis (designed experiments with fixed effects for factors, covariates and interaction of factors). This approach brings together two well established bodies of theory (the general linear model and the theory of Gaussian fields) to provide a complete and simple framework for the analysis of imaging data.The importance of this framework is twofold: (i) Conceptual and mathematical simplicity, in that the same small number of operational equations is used irrespective of the complexity of the experiment or nature of the statistical model and (ii) the generality of the framework provides for great latitude in experimental design and analysis. © 1995 Wiley‐Liss, Inc.
Brain activation associated with visual motion studied by functional magnetic resonance imaging in humans
Authors: McCarthy Gregory , Spicer Mark , Adrignolo Anthony , Luby Marie , Gore John , Allison Truett 
Published: May 2005

AbstractLocalized brain activation in response to moving visual stimuli was studied by functional magnetic resonance imaging (fMRI). Stimuli were 100 small white dots randomly arranged on a visual display. During the Motion condition, the dots moved along random, noncoherent linear trajectories at different velocities. During the Blink condition, the dots remained stationary but blinked on and off every 500 ms. The Motion and Blink conditions continuously alternated with 10 cycles per run and 6–8 runs per experiment. In half of the runs, the starting stimulus condition was Motion, while in the remaining runs it was Blink.A series of 128 gradient echo echoplanar images were acquired from 5–7 slices during each run using a 1.5 T GE Signa with an Advanced NMR echoplanar subsystem. The time series for each voxel were analyzed in the frequency domain. Voxels which demonstrated a significant spectral peak at the alternation frequency and whose phase changed in response to stimulus order were considered activated. These activated voxels were displayed upon high resolution anatomical images to determine the sites of activation and were also transformed into the coordinates of Talairach and Tournoux ([1988] Co‐planar Stereotaxic Atlas of the Human Brain, New York: Thieme) for comparison to prior neuroimaging studies.Seven of ten subjects showed clusters of activation bilaterally at the junction of the temporal and occipital lobes (area 37) in response to moving stimuli. Most activated voxels were located within or adjacent to a region designated the parietal‐temporal‐occipital fossa, or PTOF. Five subjects also showed activation to moving stimuli in midline occipital cortex. The activated voxels in midline cortex had a significantly shorter phase delay in their MR signal change relative to voxels in PTOF. © 1995 Wiley‐Liss, Inc.1This article is a US Government work and, as such, is in the public domain in the United States of America
The underestimated cerebellum
Authors: Leiner Henrietta C. , Leiner Alan L. , Dow Robert S. 
Published: May 2005

AbstractNew evidence on the structure and function of the cerebellum, which is summarized in this review, is beginning to clarify the role of the cerebellum in the human brain. The new evidence challenges the traditional concept that the cerebellum serves essentially as a motor mechanism. Instead, a more powerful role is suggested in which the cerebellum contributes to other functions as well, by sending its output to other locations in the cerebral cortex besides the well‐known motor areas. Structural evidence about the cerebellar output to such cerebral targets was obtained by using a new anatomical tracing technique on the monkey, which shows that the cerebellum sends a significant projection of nerve fibers to cognitive areas of the prefrontal cortex. Congruent with this anatomical evidence is the neuroimaging evidence obtained on normal human brains, which shows that the cerebellum is strongly activated when the brain performs some cognitive and language functions. Both structurally and functionally, therefore, the cerebellum is underestimated when it is regarded solely as a motor mechanism. Instead, it can be regarded as a more versatile information‐processing mechanism whose circuitry carries out two basic processes that are commonly performed by computers: (1) the cerebellar circuitry performs transformations on the streams of information flowing into it, and (2) it distributes the transformed streams to the right places in the brain at the right time. When such processing is performed repeatedly on motor, or cognitive, or language tasks, the cerebellum and its cerebral targets can learn through practice to perform these tasks automatically, thereby improving the speed of performance. This speed is needed, for example, in learning to speak a language fluently because such fluency requires a very rapid selection of words, which can be achieved if the search process for finding the words is performed automatically in the brain. We suggest to brain‐mappers that new discoveries about these language and cognitive functions can be found by imaging those parts of the cerebro‐cerebellar system that evolved uniquely in the human brain, and we indicate where to look. © 1995 Wiley‐Liss, Inc.
Topography of diprenorphine binding in human cingulate gyrus and adjacent cortex derived from coregistered PET and MR images
Authors: Vogt Brent A. , Watanabe Hiroshi , Grootoonk Sylke , Jones Anthony K. P. 
Published: May 2005

AbstractPositron emission tomography (PET) studies of ligand binding lack sufficient anatomical detail to evaluate topographical variations in binding within each of the lobes of the human cerebral cortex. This study employed PET to localize [11C]diprenorphine binding to opioid receptors and magnetic resonance (MR) imaging for defining medial surface structures. Continuous arterial sampling for metabolite corrected [11C]diprenorphine levels and CNS blood flow were used to model the volume of distribution (VDtot) of binding for three subjects. The PET images of VDtot were coregistered to the MR images for each case and 37 regions of interest were used to calculate VDtot. The VDtot was averaged for the three cases and coregistered with an MR reconstruction of the medial surface and plotted onto a flat map of this region.The average VDtot showed that binding was highest in anterior cingulate, rostral cingulofrontal transition, and prefrontal cortices, while binding in caudal parts of anterior cingulate and superior frontal cortices, and posterior cingulate cortex varied from high to low. Three statistical levels of binding were defined in relation to the high binding in perigenual area 24: high and equal to area 24, moderate and significantly lower than area 24 (p <0.01), or low (p <0.001). These levels of binding were plotted onto an unfolded map of the medial cortex. The VDtot was high in rostral cortex, and a strip of high binding continued caudally on the dorsal lip of the cingulate gyrus. There were patches of high binding in cinguloparietal transition, posterior parietal, and supplementary motor cortices. Four regions had low binding: (1) areas 29 and 30 in the callosal sulcus, (2) fundus of the cingulate sulcus likely involving the cingulate motor areas, (3) fundus of the superior cingulate sulcus involving two divisions of supplementary motor cortex, and (4) sensorimotor cortex on the paracentral lobule. Variations in binding may reflect functional specializations such as low binding in the cingulate motor and visuospatial areas and high levels in areas involved in processing information with affective content. The higher sensitivity of three‐dimensional scanning and coregistration of PET and MR images makes it feasible to analyze single individuals and, by performing pixel‐by‐pixel spectral analysis and generation of parametric maps, statistical analyses are possible. © 1995 Wiley‐Liss, Inc.
Simultaneous functional magnetic resonance imaging and electrophysiological recording
Authors: Huang‐Hellinger Frank R. , Breiter Hans C. , McCormack Glen , Cohen Mark S. , Kwong Ken K. , Sutton Jeffrey P. , Savoy Robert L. , Weisskoff Robert M. , Davis Timothly L. , Baker John R. , Belliveau John W. , Rosen Bruce R. 
Published: May 2005

AbstractThe purpose of this study was to develop a method for obtaining simultaneous electrophysiological and functional magnetic resonance imaging data. Using phantom experiments and tests on several of the investigators, a method for obtaining simultaneous electrophysiological and fMRI data was developed and then tested in three volunteers including two task activation experiments. It was then applied in a sleep experiment (n = 12). Current limiting resistance and low‐pass filtering were added to the electrophysiological circuit. Potential high frequency current loops were avoided in the electrical layout near the subject. MRI was performed at 1.5 T using conventional and echo planar imaging sequences. There was no evidence of subject injury. Expected correlations were observed between the electrophysiological and fMRI data in the task activation experiments. The fMRI data were not significantly degraded by the electrophysiological apparatus. Alpha waves were detected from within the magnet in seven of the 15 experimental sessions. There was degradation of the electrophysiological data due to ballistocardiographic artifacts (pulsatile whole body motion time‐locked to cardiac activity) which varied between subjects from being minimal to becoming large enough to make detection of alpha waves difficult. We concluded that simultaneous fMRI and electrophysiological recording is possible with minor modifications of standard electrophysiological equipment. Our initial results suggest this can be done safely and without compromise of the fMRI data. The usefulness of this technique for studies of such things as sleep and epilepsy is promising. Applications requiring higher precision electrophysiological data, such as evoked response measurements, may require modifications based on ballistocardiographic effects. © 1995 Wiley‐Liss, Inc.
In vivo imaging of neuromodulation using positron emission tomography: Optimal ligand characteristics and task length for detection of activation
Authors: Morris Evan D. , Fisher Ronald E. , Alpert Nathaniel M. , Rauch Scott L. , Fischman Alan J. 
Published: May 2005

AbstractConsiderable evidence suggests that cognitive state affects local levels of neurotransmitter in the brain. We introduce a compartment model of neuroreceptor ligand kinetics to describe the effect of change in cognitive state on positron emission tomography (PET) signal dynamics. The model is used to establish optimal experimental conditions, timing of activation, and ligand characteristics, for detecting cognitive activation. The model, which follows free and bound endogenous neurotransmitter, describes the PET curve predicted for a single injection of radioligand in the presence or absence of activation. Activation was conceptualized as the performance of a task that raises the level of neurotransmitter that competes for receptor sites with the radioligand. Simulating the dopamine system, for example, required making assumptions regarding the kinetic rate constants for binding/dissociation of endogenous dopamine to/from the receptor and dopamine concentrations in the synapse. Simulations suggest that activation of dopamine should be detectable with PET and the D2 receptor ligand [11C]raclopride, although this ligand might not be optimal. Aspects of experimental design can be modified to optimize the likelihood of detecting neurotransmitter changes. The ideal radioligand for these studies should bind irreversibly to its receptor. Furthermore, the task should commence at injection time and last for at least 7 minutes. Optimal task duration depends on the dynamics of free radioligand in the tissue and can be determined via model simulations for any well‐characterized receptor ligand. Flow effects were shown to be distinguishable from those of neurotransmitter activation. General principles regarding desirable ligand characteristics and activation timing held for both the D2 receptor and the dopamine transporter site. © 1995 Wiley‐Liss, Inc.
Hemispheric differences in neural systems for face working memory: A PET‐rCBF study
Authors: Haxby James V. , Ungerleider Leslie G. , Horwitz Barry , Rapoport Stanley I. , Grady Cheryl L. 
Published: May 2005

AbstractNeural systems that participate in working memory for faces were investigated in an experiment designed to distinguish face perception areas from working memory areas. Regional cerebral blood flow (rCBF) was measured using positron emission tomography (PET) while subjects performed a sensorimotor control task, a face perception control task, and five working memory tasks with parametrically varied retention intervals, ranging from 1 to 21 sec. Striate and ventral occipitotemporal extrastriate areas demonstrated a simple negative correlation between rCBF and retention delay, indicating that these areas participate principally in perceptual operations performed during visual stimulation. By contrast, right and left frontal areas demonstrated rCBF increases that were significantly more sustained across delays than were increases in ventral extrastriate areas, but the relation between rCBF and retention interval differed significantly by hemisphere. Whereas right frontal rCBF showed a nonsignificant tendency to diminish at longer delays, left inferior frontal, middle frontal, and anterior cingulate cortex, as well as left parietal and inferior temporal cortex, demonstrated their largest rCBF increases at the longest delays. These results indicate that right frontal and left frontal, parietal, and temporal areas all participate in face working memory, but that left hemisphere areas are associated with a more durable working memory representation or strategy that subjects rely on increasingly with longer retention intervals. One possible explanation for this hemispheric difference is that left hemisphere activity is associated with a face representation that embodies the result of more analysis and elaboration, whereas right frontal activity is associated with a simpler, icon‐like image of a face that is harder to maintain in working memory. © 1995 Wiley‐Liss, Inc.
A functional magnetic resonance imaging study of cortical regions associated with motor task execution and motor ideation in humans
Authors: Leonardo Marc , Fieldman Jordan , Sadato Norihiro , Campbell Gregory , Ibañez Vicente , Cohen Leonardo , Deiber Marie‐Pierre , Jezzard Peter , Pons Tim , Turner Robert , Le Bihan Denis , Hallett Mark 
Published: May 2005

AbstractAlthough motor performance may be enhanced through mental practice, the neurophysiological substrate of mental stimulation (ideation) of a motor task is not well established. We used blood oxygen level‐dependent contrast echo planar imaging at 1.5 T to identify regions of increased neural activity during the performance and ideation of a motor task. Five subjects performed a sequential finger‐to‐thumb opposition task and also imagined themselves performing the task in the absence of actual muscle movement. In all subjects, the left primary sensorimotor cortex showed more activation with actual movement than with motor ideation, but two subjects had significant activation with motor ideation. The left premotor area showed comparable activation with both actual and imagined performance in three subjects. These findings support the involvement of the primary motor area as well as the premotor area in motor ideation. © 1995 Wiley‐Liss, Inc.
Regional cerebral blood flow during object naming and word reading
Authors: Bookheimer Susan Y. , Zeffiro Thomas A. , Blaxton Teresa , Gaillard William , Theodore William 
Published: May 2005

AbstractBy several accounts, reading single words may be accomplished either by sequentially transcribing orthographic units into their corresponding sounds (an indirect route), or by directly associating a visual word form to the semantic or articulatory representation (a direct route). By contrast, the similar task of naming objects must rely only on a direct route, since objects cannot be “sounded out.” To study the localization of cognitive processes specific to reading, we used positron emission tomography (PET) to measure regional cerebral blood flow while subjects named words and pictures of objects silently or aloud. Group averages of blood flow changes were obtained for experimental vs. control tasks. Object and word presentations elicited similar blood flow increases in extra‐striate visual cortices compared with a visual noise control. Silent reading invoked a neural network very similar to that seen when subjects named objects silently, consistent with a “direct” route. Naming objects aloud produced the addition of motor output regions to this network. By contrast, oral reading produced a markedly different pattern of activated regions, suggesting reliance on a separate phonological pathway. These results provide support for the dual coding hypothesis in reading and challenge the use of strict hierarchical models of cognitive operations in PET activation studies. © 1995 Wiley‐Liss, Inc.
Identifying objects at different levels of hierarchy: A positron emission tomography study
Authors: Kosslyn Stephen M. , Alpert Nathaniel M. , Thompson William L. 
Published: May 2005

AbstractSubjects decided whether names were appropriate for accompanying pictures while their local cerebral blood flow was monitored using positron emission tomography (PET); in one condition, the names were at the “entry” level (i.e., the level spontaneously named, as in “bird” for a robin), in another condition they were at a superordinate level (e.g., “animal”), and in another they were at a subordinate level (e.g., “robin”). The results indicated that different processes are used to evaluate terms at the different levels of analysis. Specifically, there was evidence that memory search is used to evaluate superordinates, but one must collect additional perceptual information to evaluate subordinates. In addition, in another condition the subjects saw written words that named the entry‐level term and decided whether the object could be named by superordinate terms. Similar, but not identical, activation was observed as was found when subjects evaluated superordinate terms for pictures. © 1995 Wiley‐Liss, Inc.