Evaluation of changes in motor and visual functional activation over time following moderate-to-severe brain injury

Primary objective: Relatively little research has documented functional recovery following traumatic brain injury using neuroimaging techniques. This study aimed to examine the effects of moderate-to-severe brain injury on brain functioning over time.

Research design: Eight brain-injured participants completed motor and visual tasks during fMRI at two time points within the first year following injury. Changes in functional activation within ROIs and in dispersion of activation were evaluated across time points.

Main outcomes and results: Participants demonstrated significantly reduced activation intensity within the ROI over time for the motor task, but not the RPS task. Participants demonstrated a (non-significant) trend toward reduced functional dispersion over time. Most participants demonstrated greater activation within (vs outside) the ROI for both tasks. Variability among participants, in terms of activation intensity and dispersion, was evident.

Conclusions: The findings provide support for the occurrence of functional recovery over the first year post-injury, with fewer resources utilized during task completion over time. Additionally, results suggest that variability in functional activation and activation in brain regions typically activated among controls could be anticipated in a moderate-severe TBI group. Lastly, simple motor and visual tasks may be useful in efforts to demonstrate functional recovery over time.     

Neuroanatomical correlates of extraversion and neuroticism

Introversion/extraversion and neuroticism are 2 important and frequently studied dimensions of human personality. These dimensions describe individual differences in emotional responding across a range of situations and may contribute to a predisposition for psychiatric disorders. Recent neuroimaging research has begun to provide evidence that neuroticism and introversion/extraversion have specific functional and structural neural correlates. Previous studies in healthy adults have reported an association between neuroticism, introversion/extraversion, and the activity of the prefrontal cortex and amygdala. Studies of individuals with psychopathological states have also indicated that anatomic variations in these brain areas may relate to extraversion and neuroticism. The purpose of the present study was to examine selected structural correlates of neuroticism and extraversion in healthy subjects (n = 28) using neuroanatomic measures of the cerebral cortex and amygdala. We observed that the thickness of specific prefrontal cortex regions correlates with measures of extraversion and neuroticism. In contrast, no such correlations were observed for the volume of the amygdala. The results suggest that specific aspects of regional prefrontal anatomy are associated with specific personality traits.     

Attention to simultaneous unrelated auditory and visual events: behavioral and neural correlates

The cognitive and neural bases of the ability to focus attention on information in one sensory modality while ignoring information in another remain poorly understood. We hypothesized that bimodal selective attention results from increased activity in corresponding sensory cortices with a suppression of activity in non-corresponding sensory cortices. In a functional magnetic resonance imaging (fMRI) study, we presented melodies and shapes alone (unimodal) or simultaneously (bimodal). Subjects monitored for changes in an attended modality while ignoring the other. Subsequently, memory for both attended and unattended stimuli was tested. Subjects remembered attended stimuli equally well in unimodal and bimodal conditions, and significantly better than ignored stimuli in bimodal conditions. When a subject focused on a stimulus, the blood-oxygen-level-dependent (BOLD) response increased in sensory cortices corresponding to that modality in both unimodal and bimodal conditions. Additionally, the BOLD response decreased in sensory cortices corresponding to the non-presented modality in unimodal conditions and the unattended modality in bimodal conditions. We conclude that top-down attentional effects modulate the interaction of sensory cortical areas by gating sensory input. This interaction between sensory cortices enhances processing of one modality at the expense of the other during selective attention, and subsequently affects memory encoding.     

Cognitive coping style modulates neural responses to emotional faces in healthy humans: a 3-T FMRI study

Repression designates coping strategies that aim to shield the organism from distressing stimuli by disregarding their aversive characteristics. In contrast, sensitization comprises coping strategies that are employed to reduce situational uncertainty such as analyzing the environment. Functional magnetic resonance imaging was used to study neural correlates of coping styles during the perception of threatening and nonthreatening socially relevant information. Pictures of human faces bearing fearful (ambiguously threatening), angry (unambiguously threatening), happy (nonthreatening), and neutral expressions were presented masked and unmasked. Two groups of subjects were examined who were defined as consistent repressors versus consistent sensitizers with the Mainz Coping Inventory. Sensitizers tended to exhibit stronger neural responses in the amygdala to unmasked fearful faces compared with repressors. Overall, repressors were cortically more responsive to fearful (ambiguously threatening) and happy (nonthreatening) facial expressions than sensitizers, whereas sensitizers presented an enhanced responsivity to angry faces in several prefrontal areas, that is, unambiguously threatening expressions. Results from time series analyses suggest that sensitizers could exhibit less top-down cortical regulation of the amygdala than repressors in the processing of fearful faces. An increased responsivity of the amygdala to ambiguously threatening stimuli may represent a biological determinant of sensitizers' feelings of uncertainty.     

Distinct frontal regions subserve evaluation of linguistic and emotional aspects of speech intonation

In addition to the propositional content of verbal utterances, significant linguistic and emotional information is conveyed by the tone of speech. To differentiate brain regions subserving processing of linguistic and affective aspects of intonation, discrimination of sentences differing in linguistic accentuation and emotional expressiveness was evaluated by functional magnetic resonance imaging. Both tasks yielded rightward lateralization of hemodynamic responses at the level of the dorsolateral frontal cortex as well as bilateral thalamic and temporal activation. Processing of linguistic and affective intonation, thus, seems to be supported by overlapping neural networks comprising partially right-sided brain regions. Comparison of hemodynamic activation during the two different tasks, however, revealed bilateral orbito-frontal responses restricted to the affective condition as opposed to activation of the left lateral inferior frontal gyrus confined to evaluation of linguistic intonation. These findings indicate that distinct frontal regions contribute to higher level processing of intonational information depending on its communicational function. In line with other components of language processing, discrimination of linguistic accentuation seems to be lateralized to the left inferior-lateral frontal region whereas bilateral orbito-frontal areas subserve evaluation of emotional expressiveness.     

Neuroimaging correlates of cognitive changes after bariatric surgery

BackgroundObesity has been associated with cognitive deficits and increased risk for developing dementia. Bariatric surgery may result in improved cognitive function; however, the underlying structural and functional brain correlates are unclear.ObjectivesThis longitudinal study explores the hypothesis that specific brain regions and networks underlie cognitive changes after bariatric surgery.SettingUniversity Hospital, United States.MethodsSeventeen patients were recruited for this prospective cohort study, including 9 patients undergoing bariatric surgery, and 8 age-, sex-, and education level–matched healthy, nonobese control patients. Bariatric patients underwent longitudinal neuropsychologic tests and magnetic resonance imaging (MRI) scans both before and 6 months after surgery. One patient was lost to follow-up. The same neuropsychologic tests and MRI scans were performed for control patients. Differences in MRI and neuropsychologic testing between bariatric patients and control patients, and longitudinal changes within bariatric patients were assessed.ResultsAt baseline, bariatric patients demonstrated deficits in cognitive function relative to control patients, including pattern comparison (P = .009) and picture sequence memory (P = .004), which improved after significant weight loss. Baseline cognitive deficits in bariatric patients were accompanied by significantly lower left executive control network connectivity on resting-state functional MRI relative to control patients (P = .028), but differences resolved or diminished after bariatric surgery. Longitudinal improvements in pattern comparison performance correlated significantly with increases in left executive control network connectivity (r = .819; P = .013). No significant group or longitudinal differences were found in brain perfusion or brain white matter lesions.ConclusionsIndividuals with obesity undergoing bariatric surgery exhibit deficits in cognitive function and specific alterations of brain networks; however, cognitive performance can improve, and executive control network connectivity can increase after weight loss from bariatric surgery.     

The effect of visual experience on the development of functional architecture in hMT+

We investigated whether the visual hMT+ cortex plays a role in supramodal representation of sensory flow, not mediated by visual mental imagery. We used functional magnetic resonance imaging to measure neural activity in sighted and congenitally blind individuals during passive perception of optic and tactile flows. Visual motion-responsive cortex, including hMT+, was identified in the lateral occipital and inferior temporal cortices of the sighted subjects by response to optic flow. Tactile flow perception in sighted subjects activated the more anterior part of these cortical regions but deactivated the more posterior part. By contrast, perception of tactile flow in blind subjects activated the full extent, including the more posterior part. These results demonstrate that activation of hMT+ and surrounding cortex by tactile flow is not mediated by visual mental imagery and that the functional organization of hMT+ can develop to subserve tactile flow perception in the absence of any visual experience. Moreover, visual experience leads to a segregation of the motion-responsive occipitotemporal cortex into an anterior subregion involved in the representation of both optic and tactile flows and a posterior subregion that processes optic flow only.     

Imaging the brain activity changes underlying impaired visuospatial judgments: simultaneous FMRI, TMS, and behavioral studies

Damage to parietal cortex impairs visuospatial judgments. However, it is currently unknown how this damage may affect or indeed be caused by functional changes in remote but interconnected brain regions. Here, we applied transcranial magnetic stimulation (TMS) to the parietal cortices during functional magnetic resonance imaging (fMRI) while participants were solving visuospatial tasks. This allowed us to observe both the behavioral and the neural effects of transient parietal activity disruption in the active healthy human brain. Our results show that right, but not left, parietal TMS impairs visuospatial judgment, induces neural activity changes in a specific right-hemispheric network of frontoparietal regions, and shows significant correlations between the induced behavioral impairment and neural activity changes in both the directly stimulated parietal and remote ipsilateral frontal brain regions. The revealed right-hemispheric neural network effect of parietal TMS represents the same brain areas that are functionally connected during the execution of visuospatial judgments. This corroborates the notion that visuospatial deficits following parietal damage are brought about by a perturbation of activity across a specific frontoparietal network, rather than the lesioned parietal site alone. Our experiments furthermore show how concurrent fMRI and magnetic brain stimulation during active task execution hold the potential to identify and visualize networks of brain areas that are functionally related to specific cognitive processes.     

Laser acupuncture induced specific cerebral cortical and subcortical activations in humans

As recent studies demonstrated, acupuncture can elicit activity in specific brain areas. This study aims to explore further the central effect using laser acupuncture. We investigated the cerebral effects of laser acupuncture at both acupoints GB43 with functional magnetic resonance imaging (fMRI). As a control condition the laser was mounted at the same acupoints but without application of laser stimulation. The group results showed significant brain activations within the thalamus, nucleus subthalamicus, nucleus ruber, the brainstem, and the Brodmann areas 40 and 22 for the acupuncture condition. No significant brain activations were observed within the placebo condition. The activations we observed were laser acupuncture-specific and predominantly ipsilateral. This supports the assumption that acupuncture is mediated by meridians, since meridians do not cross to the other side. Furthermore, we could show that laser acupuncture allows one to design a pure placebo condition.     

MRI技术评价肝脏纤维化的应用进展

目的 综合评述当前各种磁共振成像(magnetic resonance imaging,MRI)技术在诊断肝脏纤维化中的应用现状.方法 收集国内、外最新相关文献,总结各种MRI技术在肝脏纤维化中的应用及研究进展.结果 用于评价肝脏纤维化的MRI技术包括常规增强扫描、双对比增强扫描和各种功能性MR技术.常规增强扫描可以观察纤维化引起的肝脏形态学改变,对分级价值不大;双对比增强扫描能显著提高肝脏纤维化的对比-噪声比(contrast to noise ratio,CNR);各种功能性MR技术除了能诊断肝脏纤维化外,还能对其严重程度进行分级.结论 MRI尤其是功能性MRI技术发展迅速,在肝脏纤维化诊断和严重程度评价中具有广阔应用前景.     

Cortical mechanisms for shifting and holding visuospatial attention

Access to visual awareness is often determined by covert, voluntary deployments of visual attention. Voluntary orienting without eye movements requires decoupling attention from the locus of fixation, a shift to the desired location, and maintenance of attention at that location. We used event-related functional magnetic resonance imaging to dissociate these components while observers shifted attention among 3 streams of letters and digits, one located at fixation and 2 in the periphery. Compared with holding attention at the current location, shifting attention between the peripheral locations was associated with transient increases in neural activity in the superior parietal lobule (SPL) and frontal eye fields (FEF), as in previous studies. The supplementary eye fields and separate portions of SPL and FEF were more active for decoupling attention from fixation than for shifting attention to a new location. Large segments of precentral sulcus (PreCS) and posterior parietal cortex (PPC) were more active when attention was maintained in the periphery than when it was maintained at fixation. We conclude that distinct subcomponents of the dorsal frontoparietal network initiate redeployments of covert attention to new locations and disengage attention from fixation, while sustained activity in lateral regions of PPC and PreCS represents sustained states of peripheral attention.     

Better memory and neural efficiency in young apolipoprotein E epsilon4 carriers

The apolipoprotein E (APOE) epsilon4 allele is the major genetic risk factor for Alzheimer's disease, but an APOE effect on memory performance and memory-related neurophysiology in young, healthy subjects is unknown. We found an association of APOE epsilon4 with better episodic memory compared with APOE epsilon2 and epsilon3 in 340 young, healthy persons. Neuroimaging was performed in a subset of 34 memory-matched individuals to study genetic effects on memory-related brain activity independently of differential performance. E4 carriers decreased brain activity over 3 learning runs, whereas epsilon2 and epsilon3 carriers increased activity. This smaller neural investment of epsilon4 carriers into learning reappeared during retrieval: epsilon4 carriers exhibited reduced retrieval-related activity with equal retrieval performance. APOE isoforms had no differential effects on cognitive measures other than memory, brain volumes, and brain activity related to working memory. We suggest that APOE epsilon4 is associated with good episodic memory and an economic use of memory-related neural resources in young, healthy humans.     

全脑功能连接模式分析研究及临床应用进展

基于功能MRI(fMRI)的功能连接(FC)分析可用于研究大脑功能异常。全脑FC模式具有高度特异性,可如指纹般视为个体识别标记,进而诊断疾病并指导临床治疗。本文对全脑FC模式及其临床应用进展进行综述。     

Propofol attenuates responses of the auditory cortex to acoustic stimulation in a dose-dependent manner: a FMRI study

BACKGROUND: Functional magnetic resonance imaging (fMRI) using blood-oxygen-level-dependent (BOLD) contrasts is a common method for studying sensory or cognitive brain functions. The aim of the present study was to assess the effect of the intravenous anaesthetic propofol on auditory-induced brain activation using BOLD contrast fMRI. METHODS: In eight neurosurgical patients, musical stimuli were presented binaurally in a block design. Imaging was performed under five conditions: no propofol (or wakefulness) and propofol plasma target concentrations of 0.5, 1.0, 1.5, and 2.0 microg ml(-1). RESULTS: During wakefulness we found activations in the superior temporal gyrus (STG) corresponding to the primary and secondary auditory cortex as well as in regions of higher functions of auditory information processing. The BOLD response decreased with increasing concentrations of propofol but remained partially preserved in areas of basic auditory processing in the STG during propofol 2.0 microg ml(-1). CONCLUSIONS: Our results suggest a dose-dependent impairment of central processing of auditory information after propofol administration. These results are consistent with electrophysiological findings measuring neuronal activity directly, thus suggesting a dose-dependent impairment of central processing of auditory information after propofol administration. However, propofol did not totally blunt primary cortical responses to acoustic stimulation, indicating that patients may process auditory information under general anaesthesia.     

Presentation with Recurrent Intractable Headache: A Patient with Moyamoya Syndrome—Case Report

This clinical case report represents an interesting manifestation of a neurovascular condition that can be easily overlooked by the practicing healthcare provider. In the United States, a Hispanic patient of non-Asian descent presented with atypical symptoms of intractable headache and nausea with no evidence of neurologic deficits. Further diagnostic work-up was performed as the patient was not responding to traditional analgesic medication administration. Ultimately, cerebral angiogram revealed vascular occlusion with collateral circulation consistent with moyamoya syndrome. Discussion of the challenges and available clinical guidance for healthcare professionals dealing with patients presenting with intractable headache are presented in this report.     

MR三维颅脑容积成像增强扫描诊断内听道区病变

目的探讨MR三维颅脑容积成像(3D-BRAVO)增强扫描诊断内听道区病变的价值。方法对81例内听道区病变患者(116个病灶)行3D-BRAVO增强扫描及常规增强MR检查,对比两种方法诊断内听道区病变的敏感度。结果常规增强扫描发现阳性病灶86个,诊断敏感度71.55%(83/116),漏诊率28.45%(33/116);3D-BRAVO增强扫描检出全部116个阳性病灶,诊断敏感度100%(116/116);3D-BRAVO增强扫描诊断敏感度高于常规增强扫描(Z=-3.74,P<0.001)。结论3D-BRAVO增强扫描可敏感检出内听道区病变,为临床诊疗提供影像学证据。     

Recognition of emotion from facial expression following traumatic brain injury

Primary Objective: To assess three domains of emotion recognition in people with traumatic brain injury (TBI).

Research design: A between group comparison.

Procedures: Twenty-four participants with severe TBI and 15 matched participants without brain damage were asked to label and match facial expressions with and without context. The participants with TBI were also interviewed regarding changes in subjective experience of emotion.

Main outcomes and results: Participants with TBI were found to be significantly impaired on expression labelling and matching, but experienced some improvement when provided with context. Negative emotions were particularly affected. Affective semantic knowledge and face perception appeared to be relatively intact in this group. The majority of participants with TBI reported some change in the post-injury experience of everyday emotion, although the pattern of changes differed greatly between individuals. Reduced subjective experience, especially of sadness and fear, was associated with poor emotion matching but not emotion labelling.     

Optical coherence tomography grading correlates with MRI T2 mapping and extracellular matrix content

Optical coherence tomography (OCT) and T2 mapping are emerging clinical imaging technologies with potential to detect subsurface changes in cartilage retaining a macroscopically intact articular surface. This study tests the hypothesis that OCT correlates with magnetic resonance imaging (MRI) T2 values, and that OCT signal is sensitive to cartilage matrix degeneration. Forty‐five osteochondral cores were harvested from five human tibial plateau explants after MRI T2 mapping. Cores underwent OCT imaging and were graded as follows: A, obvious birefringence; B, no birefringence; C, subsurface voids and/or irregular surface. Extracellular matrix content was determined and cores underwent histologic and polarized light microscopy (PLM) evaluation. Grade B and C cores had 25% higher superficial T2 values (p = 0.047) and 50% higher deep T2 values (p = 0.012) than grade A cores. Grade B and C cores had 36% higher glycosaminoglycan (GAG) content compared to grade A cores (p = 0.009). Histology and PLM demonstrated increased surface irregularity and structural disorganization with increasing OCT grade. OCT grade and T2 value increased with increasing collagen disorganization, suggesting that MRI T2 mapping and OCT are sensitive to changes in collagen structure. Our results demonstrate the ability of OCT and T2 mapping to detect early cartilage degeneration in clinically normal appearing cartilage. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:546–552, 2010