MR磁化传递对比成像观察新生儿轻度窒息

目的观察MR磁化传递对比(MTC)成像在轻度窒息新生儿中的应用价值。方法对15例轻度窒息新生儿(Apgar评分10分,病例组)及25名正常新生儿(对照组)采集脑常规T1WI、3D-T1WI和T1WI-MTC,计算脑磁化率(MTR),配准于标准新生儿脑模板后行统计分析。采用3dRegAna对病例组MTR与Apgar评分进行回归分析。结果相比对照组,病例组右颞极、左颞下回、左额上回、右缘上回、右眶额皮质、左额中叶、右额中回及左上额叶MTR显著降低;右梭状回、右顶叶下回、右枕中回、右颞中回、右颞下回、右颞上极、右楔叶、右角回、右舌回及右颞上回MTR显著增加。回归分析显示,病例组左中央后回、右颞下叶(前)、右额中回、右颞上极、左眶额皮质及右颞下叶(后)MTR与Apgar评分呈正相关,右壳核、右眶额皮质、左杏仁核、右颞下回、左舌回、右舌回、左颞中回、左枕中回、延髓及右梭状回呈负相关。组间MTR差异有统计学意义、且病例组MTR与Apgar评分呈正相关脑区为右额中叶、右颞极,呈负相关脑区则为右舌叶及右梭状回。结论 MR MTC成像能检出轻度窒息新生儿缺血缺氧脑区;缺血缺氧主要导致新生儿右侧脑损害。     

Visual Memory, Visual Imagery, and Visual Recognition of Large Field Patterns by the Human Brain: Functional Anatomy by Positron Emission Tomography

We measured the regional cerebral blood flow (rCBF) in 11 healthyvolunteers with PET (positron emission tomography). The mainpurpose was to map the areas of the human brain that changedrCBF during (1) the storage, (2) retrieval from long-term memory,and (3) recognition of complex visual geometrical patterns.A control measurement was done with subjects at rest. Perceptionand learning of the patterns increased rCBF in V1 and in 17cortical fields located in the cuneus, the lingual, fusiform,inferior temporal, occipital, and angular gyri, the precuneus,and the posterior part of superior parietal lobules. In addition,rCBF increased in the anterior hippocampus, anterior cingulategyrus, and in several fields in the prefrontal cortex. Recognitionof the patterns increased rCBF in 18 identically located fieldsoverlapping those activated in learning. In addition, recognitionprovoked differentially localized increases in the pulvinar,posterior hippocampus, and prefrontal cortex. Learning and recognitionof the patterns thus activated identical visual regions, butdifferent extravisual regions. A surprising finding was thatthe hippocampus was also active in recognition. Recall of thepatterns from long-term memory was associated with rCBF increasesin yet difierent fields in the prefrontal cortex, and the anteriorcingulate cortex. In addition, the posterior inferior temporallobe, the precuneus, the angular gyrus, and the posterior superiorparietal lobule were activated, but not any spot within theoccipital cortex. Activation of V1 or immediate visual associationareas is not a prerequisite for visual imagery for the patterns.The only four fields activated in storage recall and recognitionwere those in the posterior inferior temporal lobe, the precuneus,the angular gyrus, and the posterior superior parietal lobule.These might be the storage sites for such visual patterns. Ifthis is true, storage, retrieval, and recognition of complexvisual patterns are mediated by higher-level visual areas. Thus,visual learning and recognition of the same patterns make useof identical visual areas, whereas retrieval of this materialfrom the storage sites activates only a subset of the visualareas. The extravisual networks mediating storage, retrieval,and recognition differ, indicating that the ways by which thebrain accesses the storage sites are different.     

高定义角度纤维追踪技术重建人脑颞顶枕区短纤维束连接

目的观察人脑颞顶枕区短纤维束连接的空间走行、皮质连接及三维空间关系。方法对10名健康志愿者进行MR扫描。下载90名健康志愿者的弥散谱成像(DSI)综合数据模板(NTU-90)。应用高定义角度纤维束追踪技术(HDFT)对所收集数据进行人脑颞顶枕区3条短纤维束连接[上纵束的垂直部(SLF-V)、枕纵束(VOF)和颞顶束(TP)]重建,并分析其纤维走行、皮质连接、空间三维关系及左右侧别差异。结果 3条纤维束在10名志愿者和NTU-90中均重建成功。SLF-V纤维束起源于颞中回和颞下回后部,终止于角回和缘上回;VOF纤维束起源于下枕叶和梭状回,少量纤维来源于颞下回的后部和枕极前部,终止点位于角回和上枕叶外侧部;TP纤维束主要起源于颞中回、颞下回、梭状回和下颞-下枕结合部,连接于顶上小叶;左右侧SLF-V、VOF和TP的纤维束体积差异无统计学意义(P均0.05)。结论应用HDFT纤维束成像技术成功重建了SLF-V、VOF和TP,可为脑功能研究和神经外科手术提供解剖学依据。     

Cross-modal binding and activated attentional networks during audio-visual speech integration: a functional MRI study

We evaluated the neural substrates of cross-modal binding and divided attention during audio-visual speech integration using functional magnetic resonance imaging. The subjects (n = 17) were exposed to phonemically concordant or discordant auditory and visual speech stimuli. Three different matching tasks were performed: auditory-auditory (AA), visual-visual (VV) and auditory-visual (AV). Subjects were asked whether the prompted pair were congruent or not. We defined the neural substrates for the within-modal matching tasks by VV-AA and AA-VV. We defined the cross-modal area as the intersection of the loci defined by AV-AA and AV-VV. The auditory task activated the bilateral anterior superior temporal gyrus and superior temporal sulcus, the left planum temporale and left lingual gyrus. The visual task activated the bilateral middle and inferior frontal gyrus, right occipito-temporal junction, intraparietal sulcus and left cerebellum. The bilateral dorsal premotor cortex, posterior parietal cortex (including the bilateral superior parietal lobule and the left intraparietal sulcus) and right cerebellum showed more prominent activation during AV compared with AA and VV. Within these areas, the posterior parietal cortex showed more activation during concordant than discordant stimuli, and hence was related to cross-modal binding. Our results indicate a close relationship between cross-modal attentional control and cross-modal binding during speech reading.     

The functional anatomy of sleep-dependent visual skill learning

Learning of procedural skills develops gradually, with performance improving significantly with practice. But improvement on some tasks, including a visual texture discrimination task, continues in the absence of further practice, expressly during periods of sleep and not across equivalent waking episodes. Here we report that the brain activation revealed significantly different patterns of performance-related functional activity following a night of sleep relative to 1 h post-training without intervening sleep. When task activation patterns after a night of sleep were compared with activation patterns without intervening sleep (1 h post-training), significant regions of increased signal intensity were observed in the primary visual cortex, the occipital temporal junction, the medial temporal lobe and the inferior parietal lobe. In contrast, a region of decreased signal intensity was found in the right temporal pole. Corroborating these condition differences, correlations between behavioural performance and brain activation revealed significantly different patterns of performance-related functional activity following a night of sleep relative to those without intervening sleep. Together, these data provide evidence of overnight bi-directional changes in functional anatomy, differences that may form the neural basis of sleep-dependent learning expressed on this task.     

Convergence of neural systems processing stimulus associations and coordinating motor responses

A sensory-sensory learning paradigm was used to measure neural changes in humans during acquisition of an association between an auditory and visual stimulus. Three multivariate partial least-squares (PLS) analyses of positron emission tomography data identified distributed neural systems related to (i) processing the significance of the auditory stimulus, (ii) mediating the acquisition of the behavioral response, and (iii) the spatial overlap between these two systems. The system that processed the significance of the tone engaged primarily right hemisphere regions and included dorsolateral prefrontal cortex, putamen, and inferior parietal and temporal cortices. Activity changes in left occipital cortex were also identified, most likely reflecting the learned expectancy of the upcoming visual event. The system related to behavior was similar to that which coded the significance of the tone, including dorsal occipital cortex. The PLS analysis of the concordance between these two systems showed substantial regional overlap, and included occipital, dorsolateral prefrontal, and limbic cortices. However, activity in dorsomedial prefrontal cortex was strictly related to processing the auditory stimulus and not to behavior. Taken together, the PLS analyses identified a system that contained a sensory-motor component (comprised of occipital, temporal association and sensorimotor cortices) and a medial prefrontallimbic component, that as a group simultaneously embodied the learning-related response to the stimuli and the subsequent change in behavior.      

Attentional load and sensory competition in human vision: modulation of fMRI responses by load at fixation during task-irrelevant stimulation in the peripheral visual field

Perceptual suppression of distractors may depend on both endogenous and exogenous factors, such as attentional load of the current task and sensory competition among simultaneous stimuli, respectively. We used functional magnetic resonance imaging (fMRI) to compare these two types of attentional effects and examine how they may interact in the human brain. We varied the attentional load of a visual monitoring task performed on a rapid stream at central fixation without altering the central stimuli themselves, while measuring the impact on fMRI responses to task-irrelevant peripheral checkerboards presented either unilaterally or bilaterally. Activations in visual cortex for irrelevant peripheral stimulation decreased with increasing attentional load at fixation. This relative decrease was present even in V1, but became larger for successive visual areas through to V4. Decreases in activation for contralateral peripheral checkerboards due to higher central load were more pronounced within retinotopic cortex corresponding to 'inner' peripheral locations relatively near the central targets than for more eccentric 'outer' locations, demonstrating a predominant suppression of nearby surround rather than strict 'tunnel vision' during higher task load at central fixation. Contralateral activations for peripheral stimulation in one hemifield were reduced by competition with concurrent stimulation in the other hemifield only in inferior parietal cortex, not in retinotopic areas of occipital visual cortex. In addition, central attentional load interacted with competition due to bilateral versus unilateral peripheral stimuli specifically in posterior parietal and fusiform regions. These results reveal that task-dependent attentional load, and interhemifield stimulus-competition, can produce distinct influences on the neural responses to peripheral visual stimuli within the human visual system. These distinct mechanisms in selective visual processing may be integrated within posterior parietal areas, rather than earlier occipital cortex.     

A distributed left hemisphere network active during planning of everyday tool use skills

Determining the relationship between mechanisms involved in action planning and/or execution is critical to understanding the neural bases of skilled behaviors, including tool use. Here we report findings from two fMRI studies of healthy, right-handed adults in which an event-related design was used to distinguish regions involved in planning (i.e. identifying, retrieving and preparing actions associated with a familiar tools' uses) versus executing tool use gestures with the dominant right (experiment 1) and non-dominant left (experiment 2) hands. For either limb, planning tool use actions activates a distributed network in the left cerebral hemisphere consisting of: (i) posterior superior temporal sulcus, along with proximal regions of the middle and superior temporal gyri; (ii) inferior frontal and ventral premotor cortices; (iii) two distinct parietal areas, one located in the anterior supramarginal gyrus (SMG) and another in posterior SMG and angular gyrus; and (iv) dorsolateral prefrontal cortex (DLFPC). With the exception of left DLFPC, adjacent and partially overlapping sub-regions of left parietal, frontal and temporal cortex are also engaged during action execution. We suggest that this left lateralized network constitutes a neural substrate for the interaction of semantic and motoric representations upon which meaningful skills depend.     

Hemispheric asymmetries in cortical thickness

Using magnetic resonance imaging and computational cortical pattern matching methods, we analyzed hemispheric differences in regional gray matter thickness across the lateral and medial cortices in young, healthy adults (n = 60). In addition, we investigated the influence of gender on the degree of thickness asymmetry. Results revealed global and regionally specific differences between the two hemispheres, with generally thicker cortex in the left hemisphere. Regions with significant leftward asymmetry were identified in the precentral gyrus, middle frontal, anterior temporal and superior parietal lobes, while rightward asymmetry was prominent in the inferior posterior temporal lobe and inferior frontal lobe. On the medial surface, significant rightward asymmetries were observed in posterior regions, while significant leftward asymmetries were evident from the vicinity of the paracentral gyrus extending anteriorly. Asymmetry profiles were similar in both sexes, but hemispheric differences appeared slightly pronounced in males compared with females, albeit a few regions also indicated greater asymmetry in females compared with males. Hemispheric differences in the thickness of the cortex might be related to hemisphere-specific functional specializations that are possibly related to behavioral asymmetries.     

Functional anatomy of biological motion perception in posterior temporal cortex: an FMRI study of eye, mouth and hand movements

Passive viewing of biological motion engages extensive regions of the posterior temporal-occipital cortex in humans, particularly within and nearby the superior temporal sulcus (STS). Relatively little is known about the functional specificity of this area. Some recent studies have emphasized the perceived intentionality of the motion as a potential organizing principle, while others have suggested the existence of a somatotopy based upon the limb perceived in motion. Here we conducted an event-related functional magnetic resonance imaging experiment to compare activity elicited by movement of the eyes, mouth or hand. Each motion evoked robust activation in the right posterior temporal-occipital cortex. While there was substantial overlap of the activation maps in this region, the spatial distribution of hemodynamic response amplitudes differentiated the movements. Mouth movements elicited activity along the mid-posterior STS while eye movements elicited activity in more superior and posterior portions of the right posterior STS region. Hand movements activated more inferior and posterior portions of the STS region within the posterior continuing branch of the STS. Hand-evoked activity also extended into the inferior temporal, middle occipital and lingual gyri. This topography may, in part, reflect the role of particular body motions in different functional activities.     

Connection patterns distinguish 3 regions of human parietal cortex

Three regions of the macaque inferior parietal lobule and adjacent lateral intraparietal sulcus (IPS) are distinguished by the relative strengths of their connections with the superior colliculus, parahippocampal gyrus, and ventral premotor cortex. It was hypothesized that connectivity information could therefore be used to identify similar areas in the human parietal cortex using diffusion-weighted imaging and probabilistic tractography. Unusually, the subcortical routes of the 3 projections have been reported in the macaque, so it was possible to compare not only the terminations of connections but also their course. The medial IPS had the highest probability of connection with the superior colliculus. The projection pathway resembled that connecting parietal cortex and superior colliculus in the macaque. The posterior angular gyrus and the adjacent superior occipital gyrus had a high probability of connection with the parahippocampal gyrus. The projection pathway resembled the macaque inferior longitudinal fascicle, which connects these areas. The ventral premotor cortex had a high probability of connection with the supramarginal gyrus and anterior IPS. The connection was mediated by the third branch of the superior longitudinal fascicle, which interconnects similar regions in the macaque. Human parietal areas have anatomical connections resembling those of functionally related macaque parietal areas.     

Repetition suppression and reactivation in auditory-verbal short-term recognition memory

The neural response to stimulus repetition is not uniform across brain regions, stimulus modalities, or task contexts. For instance, it has been observed in many functional magnetic resonance imaging (fMRI) studies that sometimes stimulus repetition leads to a relative reduction in neural activity (repetition suppression), whereas in other cases repetition results in a relative increase in activity (repetition enhancement). In the present study, we hypothesized that in the context of a verbal short-term recognition memory task, repetition-related "increases" should be observed in the same posterior temporal regions that have been previously associated with "persistent activity" in working memory rehearsal paradigms. We used fMRI and a continuous recognition memory paradigm with short lags to examine repetition effects in the posterior and anterior regions of the superior temporal cortex. Results showed that, consistent with our hypothesis, the 2 posterior temporal regions consistently associated with working memory maintenance, also show repetition increases during short-term recognition memory. In contrast, a region in the anterior superior temporal lobe showed repetition suppression effects, consistent with previous research work on perceptual adaptation in the auditory-verbal domain. We interpret these results in light of recent theories of the functional specialization along the anterior and posterior axes of the superior temporal lobe.     

Retinotopy and attention in human occipital, temporal, parietal, and frontal cortex

Novel mapping stimuli composed of biological motion figures were used to study the extent and layout of multiple retinotopic regions in the entire human brain and to examine the independent manipulation of retinotopic responses by visual stimuli and by attention. A number of areas exhibited retinotopic activations, including full or partial visual field representations in occipital cortex, the precuneus, motion-sensitive temporal cortex (extending into the superior temporal sulcus), the intraparietal sulcus, and the vicinity of the frontal eye fields in frontal cortex. Early visual areas showed mainly stimulus-driven retinotopy; parietal and frontal areas were driven primarily by attention; and lateral temporal regions could be driven by both. We found clear spatial specificity of attentional modulation not just in early visual areas but also in classical attentional control areas in parietal and frontal cortex. Indeed, strong spatiotopic activity in these areas could be evoked by directed attention alone. Conversely, motion-sensitive temporal regions, while exhibiting attentional modulation, also responded significantly when attention was directed away from the retinotopic stimuli.     

Reciprocal connectivity of identified color-processing modules in the monkey inferior temporal cortex

The inferior temporal (IT) cortex is the last unimodal visual area in the ventral visual pathway and is essential for color discrimination. Recent imaging and electrophysiological studies have revealed the presence of several distinct patches of color-selective cells in the anterior IT cortex (AIT) and posterior IT cortex (PIT). To understand the neural machinery for color processing in the IT cortex, in the present study, we combined anatomical tracing methods with electrophysiological unit recordings to investigate the anatomical connections of identified clusters of color-selective cells in monkey IT cortex. We found that a color cluster in AIT received projections from a color cluster in PIT as well as from discrete clusters of cells in other occipitotemporal areas, in the superior temporal sulcus, and in prefrontal and parietal cortices. The distribution of the labeled cells in PIT closely corresponded with that of the physiologically identified color-selective cells in this region. Furthermore, retrograde tracer injections in the posterior color cluster resulted in labeled cells in the anterior cluster. Thus, temporal lobe color-processing modules form a reciprocally interconnected loop within a distributed network.     

Activity in face-responsive brain regions is modulated by invisible, attended faces: evidence from masked priming

It is often assumed that neural activity in face-responsive regions of primate cortex correlates with conscious perception of faces. However, whether such activity occurs without awareness is still debated. Using functional magnetic resonance imaging (fMRI) in conjunction with a novel masked face priming paradigm, we observed neural modulations that could not be attributed to perceptual awareness. More specifically, we found reduced activity in several classic face-processing regions, including the "fusiform face area," "occipital face area," and superior temporal sulcus, when a face was preceded by a briefly flashed image of the same face, relative to a different face, even when 2 images of the same face differed. Importantly, unlike most previous studies, which have minimized awareness by using conditions of inattention, the present results occurred when the stimuli (the primes) were attended. By contrast, when primes were perceived consciously, in a long-lag priming paradigm, we found repetition-related activity increases in additional frontal and parietal regions. These data not only demonstrate that fMRI activity in face-responsive regions can be modulated independently of perceptual awareness, but also document where such subliminal face-processing occurs (i.e., restricted to face-responsive regions of occipital and temporal cortex) and to what extent (i.e., independent of the specific image).     

Microsurgical anatomy of the superficial veins of the cerebrum

The microsurgical anatomy of the superficial cortical veins was examined in 20 cerebral hemispheres. The superficial cortical veins are divided into three groups based on whether they drain the lateral, medial, or inferior surface of the hemisphere. The veins on the three surfaces are further subdivided on the basis of the lobe and cortical area that they drain. The superficial cerebral veins collect into four groups of bridging veins: a superior sagittal group, which drains into the superior sagittal sinus; a sphenoidal group, which drains into the sphenoparietal and cavernous sinuses on the inner surface of the sphenoid bone; a tentorial group, which converges on the sinuses in the tentorium; and a falcine group, which empties into the inferior sagittal or straight sinus or their tributaries. The superior sagittal group drains the superior part of the medial and lateral surfaces of the frontal, parietal, and occipital lobes and the anterior part of the basal surface of the frontal lobe. The sphenoidal group drains the parts of the frontal, temporal, and parietal lobes adjoining the sylvian fissure. The tentorial group drains the lateral surface of the temporal lobe and the basal surface of the temporal and occipital lobes. The falcine group drains an area that includes the cingulate and parahippocampal gyri and approximates the cortical parts of the limbic lobe of the brain. The relationship of these veins to the venous lacunae was also examined.     

Sound to language: different cortical processing for first and second languages in elementary school children as revealed by a large-scale study using fNIRS

A large-scale study of 484 elementary school children (6-10 years) performing word repetition tasks in their native language (L1-Japanese) and a second language (L2-English) was conducted using functional near-infrared spectroscopy. Three factors presumably associated with cortical activation, language (L1/L2), word frequency (high/low), and hemisphere (left/right), were investigated. L1 words elicited significantly greater brain activation than L2 words, regardless of semantic knowledge, particularly in the superior/middle temporal and inferior parietal regions (angular/supramarginal gyri). The greater L1-elicited activation in these regions suggests that they are phonological loci, reflecting processes tuned to the phonology of the native language, while phonologically unfamiliar L2 words were processed like nonword auditory stimuli. The activation was bilateral in the auditory and superior/middle temporal regions. Hemispheric asymmetry was observed in the inferior frontal region (right dominant), and in the inferior parietal region with interactions: low-frequency words elicited more right-hemispheric activation (particularly in the supramarginal gyrus), while high-frequency words elicited more left-hemispheric activation (particularly in the angular gyrus). The present results reveal the strong involvement of a bilateral language network in children's brains depending more on right-hemispheric processing while acquiring unfamiliar/low-frequency words. A right-to-left shift in laterality should occur in the inferior parietal region, as lexical knowledge increases irrespective of language.     

Zooming in and zooming out of the attentional focus: an FMRI study

Visuospatial attention can either be "narrowly" focused on (zooming in) or "widely" distributed to (zooming out) different locations in space. In the current functional magnetic resonance imaging study, we investigated the shared and differential neural mechanisms underlying the dynamic "zooming in" and "zooming out" processes while potential distance confounds from visual inputs between zooming in and zooming out were controlled for. When compared with zooming out, zooming in differentially implicated left anterior intraparietal sulcus (IPS), which may reflect the functional specificity of left anterior IPS in focusing attention on local object features. By contrast, zooming out differentially activated right inferior frontal gyrus, which may reflect higher demands on cognitive control processes associated with enlarging the attentional focus. A conjunction analysis between zooming in and zooming out revealed significant shared activations in right middle temporal gyrus, right superior occipital gyrus, and right superior parietal cortex. The latter result suggests that the right posterior temporal-occipital-parietal system, which is known to be crucial for the control of spatial attention, is involved in updating the internal representation of the spatial locations that attentional processing is associated with.     

The functional anatomy of the normal human auditory system: responses to 0.5 and 4.0 kHz tones at varied intensities

Most functional imaging studies of the auditory system have employed complex stimuli. We used positron emission tomography to map neural responses to 0.5 and 4.0 kHz sine-wave tones presented to the right ear at 30, 50, 70 and 90 dB HL and found activation in a complex neural network of elements traditionally associated with the auditory system as well as non-traditional sites such as the posterior cingulate cortex. Cingulate activity was maximal at low stimulus intensities, suggesting that it may function as a gain control center. In the right temporal lobe, the location of the maximal response varied with the intensity, but not with the frequency of the stimuli. In the left temporal lobe, there was evidence for tonotopic organization: a site lateral to the left primary auditory cortex was activated equally by both tones while a second site in primary auditory cortex was more responsive to the higher frequency. Infratentorial activations were contralateral to the stimulated ear and included the lateral cerebellum, the lateral pontine tegmentum, the midbrain and the medial geniculate. Contrary to predictions based on cochlear membrane mechanics, at each intensity, 4.0 kHz stimuli were more potent activators of the brain than the 0.5 kHz stimuli.     

Neurodevelopmental correlates of true and false recognition

The Deese/Roediger-McDermott (DRM) false-memory effect has been extensively documented in psychological research. People falsely recognize critical lures or nonstudied items that are semantically associated with studied items. Behavioral research has provided evidence for age-related increases in the DRM false-recognition effect. The present event-related functional magnetic resonance imaging study was aimed at investigating neurodevelopmental changes in brain regions associated with true- and false-memory recognition in 8-year olds, 12-year olds, and adults. Relative to 8-year olds, adults correctly endorsed more studied items as "old" but also mistakenly endorsed more critical lures. Age-related increases in recollection were associated with changes in the medial temporal lobe (MTL) activation profile. Additionally, age-related increases in false alarms (FAs) to semantically related lures were associated with changes in the activation profile of left ventrolateral prefrontal cortex, a region associated with semantic processing. Additional regions exhibiting age-related changes include posterior parietal and anterior prefrontal cortices. In summary, concomitant changes in the MTL, prefrontal cortex, and parietal cortex underlie developmental increases in true and false recognition during childhood and adolescence.