Artifact suppression and analysis of brain activities with electroencephalography signals

Brain-computer interface is a communication system that connects the brain with computer (or other devices) but is not dependent on the normal output of the brain (i.e., peripheral nerve and muscle). Electro-oculogram is a dominant artifact which has a significant negative influence on further analysis of real electroencephalography data. This paper presented a data adaptive technique for artifact suppression and brain wave extraction from electroencephalography signals to detect regional brain activities. Empirical mode decomposition based adaptive thresholding approach was employed here to suppress the electro-oculogram artifact. Fractional Gaussian noise was used to determine the threshold level derived from the analysis data without any training. The purified electroencephalography signal was composed of the brain waves also called rhythmic components which represent the brain activities. The rhythmic components were extracted from each electroencephalography channel using adaptive wiener filter with the original scale. The regional brain activities were mapped on the basis of the spatial distribution of rhythmic components, and the results showed that different regions of the brain are activated in response to different stimuli. This research analyzed the activities of a single rhythmic component, alpha with respect to different motor imaginations. The experimental results showed that the proposed method is very efficient in artifact suppression and identifying individual motor imagery based on the activities of alpha component.     

Topographic representations of object size and relationships with numerosity reveal generalized quantity processing in human parietal cortex

Humans and many animals analyze sensory information to estimate quantities that guide behavior and decisions. These quantities include numerosity (object number) and object size. Having recently demonstrated topographic maps of numerosity, we ask whether the brain also contains maps of object size. Using ultra-high-field (7T) functional MRI and population receptive field modeling, we describe tuned responses to visual object size in bilateral human posterior parietal cortex. Tuning follows linear Gaussian functions and shows surround suppression, and tuning width narrows with increasing preferred object size. Object size-tuned responses are organized in bilateral topographic maps, with similar cortical extents responding to large and small objects. These properties of object size tuning and map organization all differ from the numerosity representation, suggesting that object size and numerosity tuning result from distinct mechanisms. However, their maps largely overlap and object size preferences correlate with numerosity preferences, suggesting associated representations of these two quantities. Object size preferences here show no discernable relation to visual position preferences found in visuospatial receptive fields. As such, object size maps (much like numerosity maps) do not reflect sensory organ structure but instead emerge within the brain. We speculate that, as in sensory processing, optimization of cognitive processing using topographic maps may be a common organizing principle in association cortex. Interactions between object size and numerosity maps may associate cognitive representations of these related features, potentially allowing consideration of both quantities together when making decisions.Humans and animals share a sense of numerosity (object number) that guides behavior and decisions (1, 2), for example choosing numerous objects when foraging or shopping. As such, numbers and numerical processing are fundamental to cognitive neuroscience and are linked to mathematics, value judgments, and economics (1, 3). Because aspects of numerosity perception mirror primary sensory perception, it has been referred to as a “number sense” (4). However, another theory (5) sees numerosity as one aspect of a more generalized quantity system. Here we investigate the representation of another quantity: object size.Behaviorally, object size and numerosity perception interfere with each other (6). At the neural level, single neurons in macaque parietal cortex can be tuned to numerosity (7), line length (a measure of object size), or both (8). However, it is unclear whether numerosity and object size preferences are related, either in the same neurons or in nearby neurons (8). Using human neuroimaging, we have shown that numerosity-tuned neural populations in human posterior parietal lobe are topographically organized (9): Similar numerosity preferences are grouped together, changing gradually across the cortical surface. Visual features of the presented stimuli affect numerosity preferences, which may reflect preferences for particular object sizes (9, 10).Here we ask whether object size-tuned responses are found in the same area, whether these are topographically organized, and how tuning and organization relate to representations of numerosity and visual space in the same area. We find topographically organized object size-tuned responses that largely overlap with numerosity maps and show correlated tuning preferences. However, many differences between object size and numerosity tuning and map organization suggest that responses arise from distinct mechanisms.These intermingled neuronal representations of object number and size may allow generalization and abstraction in quantity processing and consideration of related quantities when making decisions. Optimization of cognitive processing using topographic maps may be a common organizing principle in association cortex, particularly in quantity processing, as it is in sensory processing.     

Discontinuity of cortical gradients reflects sensory impairment

Topographic maps and their continuity constitute a fundamental principle of brain organization. In the somatosensory system, whole-body sensory impairment may be reflected either in cortical signal reduction or disorganization of the somatotopic map, such as disturbed continuity. Here we investigated the role of continuity in pathological states. We studied whole-body cortical representations in response to continuous sensory stimulation under functional MRI (fMRI) in two unique patient populations—patients with cervical sensory Brown-Séquard syndrome (injury to one side of the spinal cord) and patients before and after surgical repair of cervical disk protrusion—enabling us to compare whole-body representations in the same study subjects. We quantified the spatial gradient of cortical activation and evaluated the divergence from a continuous pattern. Gradient continuity was found to be disturbed at the primary somatosensory cortex (S1) and the supplementary motor area (SMA), in both patient populations: contralateral to the disturbed body side in the Brown-Séquard group and before repair in the surgical group, which was further improved after intervention. Results corresponding to the nondisturbed body side and after surgical repair were comparable with control subjects. No difference was found in the fMRI signal power between the different conditions in the two groups, as well as with respect to control subjects. These results suggest that decreased sensation in our patients is related to gradient discontinuity rather than signal reduction. Gradient continuity may be crucial for somatotopic and other topographical organization, and its disruption may characterize pathological processing.The somatotopic “homunculus” representation in the human cortex is one of the most important discoveries of modern neuroscience (1, 2). The early electrophysiological findings of Penfield and coworkers (1, 2) have been confirmed and extended in several neuroimaging studies in healthy individuals (3–7) and have been further explored in patients and nonhuman primates with different pathologies using both electrophysiology and neuroimaging (8–14). The latter elicited changes in the cortical pattern of activity after a damage to the somatosensory system, manifested as functional cortical reorganization. Kaas, Merzenich, and Killackey suggested that there may be “several types of cortical reorganization, including (i) the somatotopic expansion of previously existing representations of body parts, (ii) the development of ‘new’ representations, (iii) the activation of large regions of the cortex from a very limited region of a receptive field surface, and (iv) a ‘nonsomatotopic’ activation of the cortex from scattered receptive fields” (9). The first three reorganization options were established whereas non-somatotopic representation remains understudied and unclear. A potential explanation is that most previous studies focused on the reorganization of single organ representation or changes in limited cortical area without exploring large scale topographical changes. We hypothesized that large scale nonsomatotopic reorganization may be associated to the relationship between the representation of the disturbed body part and the whole-body representation. In fact, the whole-body representation may have particular importance because continuous somatotopic organization reflects not only adjacency of different body parts, but also the general principle that neural populations that are involved in similar computational tasks are located in close spatial proximity (15, 16). Nonsomatotopic discontinuous whole-body representation may thus reflect a general pathological principle.To examine the role of continuity and discontinuity in somatosensory processing, we searched for a model that would enable us to compare processing of physiological and pathological whole-body continuous signals in the same study subject. One such model is the cervical partial (sensory) Brown-Séquard syndrome. This syndrome is characterized by injury to one half of the spinal cord, which disturbs sensory signal conduction from half of the body below the lesion to the contralateral hemisphere (17, 18). Patients with Brown-Séquard syndrome experience a reduction in sensation of one side of their body (hemihypoesthesia). Cervical Brown-Séquard syndrome is unique, involving a unilateral representation of the body, but in patients without brain pathology, thus serving as an ideal model to compare physiological and pathological cortical patterns from the disturbed and nondisturbed body sides in each individual patient. Another model that may causally demonstrate the role of continuity and discontinuity in somatosensory processing is one involving patients before and after surgical repair of cervical disk protrusion. This model enables examination of continuity in the same study subjects before and after intervention. Notably, whereas studies in nonhuman primates compare response to lesion before and after induction, no such study, to our knowledge, has examined response to surgical repair. We therefore used functional MRI (fMRI) in these two patient populations to compare responses in the most prominent somatosensory homunculi—the primary somatosensory cortex (S1) and supplementary motor area (SMA) (1, 19)—with continuous sensory stimulation of the whole body.To describe a sequential change in cortical activation coinciding with continuous sensory stimulation, we use the term “gradient” (20, 21). We quantified the continuity of gradients by analyzing a one-dimensional series of functional cluster geometric centroids that represent responses to sensory input from different body parts. Signal power was measured as well because somatosensory deficit that results in hypoesthesia may be reflected in signal reduction. We hypothesize that somatotopic representation in the hemisphere contralateral to the sensory deficit exhibits functional reorganization manifested as gradient discontinuity.     

32例甲状腺尸解及对手术的意义

甲状腺毗邻关系复杂。为探索与甲状腺切除手术有关的甲状腺局部解剖的特点，我们对３２例成人尸体的甲状腺毗邻关系进行了解剖观察和测量。从甲状腺的形状、大小，甲状腺上动脉与喉上神经走行关系，甲状腺下动脉与喉返神经的走行关系，甲状旁腺的形态及分布，报告了观察的结果。总结了１０点对甲状腺次全切除有启迪意义的局部解剖特点，并提出了手术的危险区、安全区、变异区和易损伤区的概念     

Computerized EEG topography in childhood migraine between and during attacks

Topographic EEG mapping was performed in 58 migrainous children (mean age: 12.9 years; 39 without, 19 with aura) between attacks. Ten children were also recorded during an attack with visual aura. Between attacks there were no significant differences between migraineurs and age-matched controls. During visual aura a decrease in occipital alpha power contralateral to the affected hemifield was found in all patients. This was followed by a bilateral frontal increase in delta power, and, during the headache, by an increased delta activity in posterior-temporal and occipital electrode sites. The possible brain mechanisms underlying these EEG changes are discussed.     

Structure-Activity Relationship Studies of CNS Agents,Part 25: 4,6-Di(heteroaryl)-2-(N-methylpiperazino)pyrimidines as New,Potent 5-HT2A Receptor Ligands: A Verification of the Topographic Model

A series of new 4,6-di(heteroaryl)pyrimidines containing an N-methylpiperazino group ( 6 – 13 ) or an ethylenediamine chain ( 15 – 20 ) in position 2 were synthesized and their 5-HT_1A and 5-HT_2A receptor affinities were determined. It was shown that the substituent effects on the 5-HT_2A affinity are additive and could be described quantitatively. In a behavioral model it was also demonstrated that 6 – 11 are 5-HT_2A receptor antagonists. The molecular modelling results suggested that the distances between the basic nitrogen atom and the two aromatic centers (d₁ = 5.2?8.4 Å, d₂ = 5.7?8.5 Å, and d₃ = 4.6?7.3 Å) define the molecular topography of the 5-HT_2A receptor antagonists under study.     

Relationship of retinotopic ordering of axons in the optic pathway to the formation of visual maps in central targets.

We examined in rats the relationship between the ordering of retinal axons in the optic pathway and the formation of a retinotopically organized projection to their primary target, the contralateral superior colliculus (SC). We have previously found that axons labeled by focal injections of 1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) made in temporal or nasal retina of perinatal rats commonly mistarget along the medial-lateral and rostral-caudal axes of the SC. By postnatal day (P) 11-12, the retinocollicular projection attains an adult-like topography. Incorrectly targeted axons or axon segments are removed; axons that persist terminate in the topographically appropriate part of the SC (Simon and O'Leary: Dev Biol 137:125, 1990). In the present study, we made similar DiI injections, covering less than 2% of the retinal area, in peripheral temporal, nasal, superior, or inferior retina, in rats of two age groups, embryonic day (E) 21 to P (postnatal day) 2 and P11-P17. Whole mounts of retina, optic nerve and tract, and SC, and cross sections of the optic nerve, were examined. In E21-P2 rats, retinal axons labeled from each retinal site are diffusely distributed in the SC, and poorly ordered in the optic pathway. In retina, labeled axons travel in fascicles directly from the injection site to the optic disc, but neighbor relationships begin to degrade as fascicles split and mix. Retinotopic order is virtually lost in the optic nerve; axons labeled from each injection site disperse throughout its cross-sectional area, but the labeled axons tend to be concentrated toward a specific half of the nerve depending upon their retinal origin. This slight tendency toward retinotopic order increases in the optic tract, but axons are still poorly ordered as they leave the tract and enter the SC. Targeting errors along the medial-lateral axis of the SC, but apparently not along its rostral-caudal axis, are related to the positioning of axons across the width of the optic tract. In P11-P17 rats, axons labeled from each injection site arborize only in a small, topographically correct part of the SC. However, the distributions of labeled retinal axons observed in whole mounts of the retina and optic pathway have a degree of disorder similar to those in E21-P2 rats. Further, the scatter of labeled axons in optic nerve cross sections is comparable in both age groups. Therefore, the emergence of topographic order in the retinocollicular projection is not accompanied by an emergence of a retinotopic ordering of axons in the optic nerve.(ABSTRACT TRUNCATED AT 400 WORDS)     

Topography of α-internexin-positive neuronal aggregates in 10 patients with neuronal intermediate filament inclusion disease

Abnormal neuronal intermediate filament (IF) inclusions immunopositive for the type IV IF alpha-internexin have been identified as the pathological hallmark of neuronal intermediate filament inclusion disease (NIFID). We studied the topography of these inclusions in the frontal and temporal lobe in 68 areas from 10 cases of NIFID. In the cerebral cortex, CA sectors of the hippocampus, and dentate gyrus granule cell layer, the inclusions were distributed mainly in regularly distributed clusters, 50-800 microm in diameter. In seven cortical areas, there was a more complex pattern in which the clusters of inclusions were aggregated into larger super clusters. In 11 cortical areas, the size of the clusters approximated to those of the cells of origin of the cortico-cortical pathways but in the majority of the remaining areas, cluster size was smaller than 400 microm. The topography of the lesions suggests that there is degeneration of the cortico-cortical projections in NIFID with the formation of alpha-internexin-positive aggregates within vertical columns of cells. Initially, only a subset of cells within a vertical column develops inclusions but as the disease progresses, the whole of the column becomes affected. The corticostriate projection appears to have little effect on the cortical topography of the inclusions.     

Topographic tear film trend and new parameters for non-invasive break up time test

AIM: To evaluate the quantitative and qualitative results of the noninvasive tear film break-up time (NI-BUT) test and investigate the predictive ability of the new NI-BUT parameter in discriminating between normal Ocular Surface Disease Index (OSDI; scores ≤12) and abnormal OSDI (scores ≥13). METHODS: A total of 341 eyes of 341 volunteers who applied for routine eye outpatient control were included in the prospective study. All participants’ noninvasive first tear film break-up time (NIF-BUT), noninvasive average tear film break-up time (NIAvg-BUT) and average value of the first three break-up time (A3F-BUT) were analyzed. A3F-BUT, the new NI-BUT parameter, is calculated by adding the NIF-BUT value to the 2nd break-up time value that has a difference of at most 1 second from the NIF-BUT value and to the 3rd break-up time and then dividing the respective sum by 3. Receiver operating characteristic (ROC) curve and forward logistic regression analyses were performed to determine the parameter that had the best predictive ability between the OSDI groups. RESULTS: The NI-BUT values of 255 eyes of 255 volunteers included in the study were analyzed statistically. The mean NIF-BUT, NIAvg-BUT, and A3F-BUT values were calculated as 5.3±3.0, 8±3.1, and 5.8±3.0 seconds, respectively. All three parameters were found to be significantly lower in the abnormal OSDI group (P=0.014, 0.034, and 0.011, respectively). The area under the curve (AUC) of the A3F-BUT to predict abnormal OSDI was AUC=0.625 (0.529-0.720), P=0.011 and NIF-BUT was AUC=0.599 (0.502-0.696), P=0.043. The A3F-BUT parameter and NIF-BUT parameters were found to be significantly efficient in discriminating abnormal OSDI. CONCLUSION: The new parameter for the NI-BUT test has more predictive ability in the discrimination of OSDI groups.     

Ipsilateral connections of the ventral premotor cortex in a new world primate

The present study describes the pattern of connections of the ventral premotor cortex (PMv) with various cortical regions of the ipsilateral hemisphere in adult squirrel monkeys. Particularly, we 1) quantified the proportion of inputs and outputs that the PMv distal forelimb representation shares with other areas in the ipsilateral cortex and 2) defined the pattern of PMv connections with respect to the location of the distal forelimb representation in primary motor cortex (M1), primary somatosensory cortex (S1), and supplementary motor area (SMA). Intracortical microstimulation techniques (ICMS) were used in four experimentally naïve monkeys to identify M1, PMv, and SMA forelimb movement representations. Multiunit recording techniques and myelin staining were used to identify the S1 hand representation. Then, biotinylated dextran amine (BDA; 10,000 MW) was injected in the center of the PMv distal forelimb representation. After tangential sectioning, the distribution of BDA‐labeled cell bodies and terminal boutons was documented. In M1, labeling followed a rostrolateral pattern, largely leaving the caudomedial M1 unlabeled. Quantification of somata and terminals showed that two areas share major connections with PMv: M1 and frontal areas immediately rostral to PMv, designated as frontal rostral area (FR). Connections with this latter region have not been described previously. Moderate connections were found with PMd, SMA, anterior operculum, and posterior operculum/inferior parietal area. Minor connections were found with diverse areas of the precentral and parietal cortex, including S1. No statistical difference between the proportions of inputs and outputs for any location was observed, supporting the reciprocity of PMv intracortical connections. J. Comp. Neurol. 495:374–390, 2006. © 2006 Wiley‐Liss, Inc.