Developmental changes in the neural correlates of semantic processing

Functional magnetic resonance imaging (fMRI) was used to explore the neural correlates of semantic judgments in the auditory modality in a group of 9- to 15-year-old children. Subjects were required to indicate if word pairs were related in meaning. Consistent with previous findings in adults, children showed activation in bilateral superior temporal gyri (BA 22) for recognizing spoken words as well as activations in bilateral inferior frontal gyri (BAs 47, 45) and left middle temporal gyrus (BA 21) for semantic processing. The neural substrates of semantic association and age differences were also investigated. Words with strong semantic association elicited significantly greater activation in the left inferior parietal lobule (BA 40), whereas words with weak semantic association elicited activation in left inferior frontal gyrus (BAs 47/45). Correlations with age were observed in the left middle temporal gyrus (BA 21) and the right inferior frontal gyrus (BA 47). The pattern of results for semantic association implies that the left inferior parietal lobule effectively integrates highly related semantic features and the left inferior frontal gyrus becomes more active for words that require a greater search for semantic associations. The developmental results suggest that older children recruit the right inferior frontal gyrus as they conduct a broader semantic search and the left middle temporal gyrus to provide more efficient access to semantic representations.     

Brain correlates of risky decision-making

Understanding the neurocognitive basis of risk-taking behavior is an important issue, especially in economic decision-making. Classical behavioral studies have shown that risk-attitude changes across different contexts, but little is so far known about the brain correlates of processing of outcomes across such context shifts. In this study, EEG was recorded while subjects performed a gambling task. Participants could choose between a risky and a safer option, within two different contexts: one in which options yielded gains and losses of the same magnitude (Zero Expected Value context) and another in which gains were larger than losses (Positive Expected Value context). Based on their risk-attitude, two groups were compared: subjects who are risk-seekers in the zero Expected Value context (Zero-Oriented group) and subjects who are risk-seekers in the positive Expected Value condition (Positive-Oriented group). The Feedback Related Negativity (FRN) reflects this distinction, with each group being insensitive to magnitude of outcomes in the condition in which they were risk-prone. P300 amplitude mirrored the behavioral results, with larger amplitudes in the condition in which each group showed a higher risk-tendency. Source analyses highlighted the involvement of posterior cingulate cortex in risky decision-making. Taken together, the findings make a contribution to the clarification of the neurocognitive substrates of risky decision-making.     

Dissociative neural correlates of semantic processing of nouns and verbs in Chinese--a language with minimal inflectional morphology

Numerous studies using various techniques and methodologies have demonstrated distinctive responses to nouns and verbs both at the behavioral and neurological levels. However, since the great majority of these studies involved tasks employing pictorial stimuli and languages with rich inflectional morphology, it is not clear whether word class effects resulted from semantic differences between objects and actions or different inflectional operations associated with the two word classes. Such shortcomings were addressed in this study by using a language with impoverished inflectional morphology - Chinese. Both concrete and abstract words were included, while controlling for nuisance variables between the two word classes, including imageability, word frequency, age-of-acquisition, and number of stroke. Participants were asked to judge the semantic relatedness of noun or verb pairs by pressing different buttons. The results revealed specific neural correlates for verb class in left lateral temporal and inferior frontal regions. Furthermore, the patterns of neural distribution of nouns and verbs were consistent with observations from Indo-European languages. Plausible accounts for neural separation of word classes were considered.     

Auditory perceptual decision-making based on semantic categorization of environmental sounds

Discriminating complex sounds relies on multiple stages of differential brain activity. The specific roles of these stages and their links to perception were the focus of the present study. We presented 250 ms duration sounds of living and man-made objects while recording 160-channel electroencephalography (EEG). Subjects categorized each sound as that of a living, man-made or unknown item. We tested whether/when the brain discriminates between sound categories even when not transpiring behaviorally. We applied a single-trial classifier that identified voltage topographies and latencies at which brain responses are most discriminative. For sounds that the subjects could not categorize, we could successfully decode the semantic category based on differences in voltage topographies during the 116-174 ms post-stimulus period. Sounds that were correctly categorized as that of a living or man-made item by the same subjects exhibited two periods of differences in voltage topographies at the single-trial level. Subjects exhibited differential activity before the sound ended (starting at 112 ms) and on a separate period at ~270 ms post-stimulus onset. Because each of these periods could be used to reliably decode semantic categories, we interpreted the first as being related to an implicit tuning for sound representations and the second as being linked to perceptual decision-making processes. Collectively, our results show that the brain discriminates environmental sounds during early stages and independently of behavioral proficiency and that explicit sound categorization requires a subsequent processing stage.     

Neural correlates of blink suppression and the buildup of a natural bodily urge

Neuroimaging studies have elucidated some of the underlying physiology of spontaneous and voluntary eye blinking; however, the neural networks involved in eye blink suppression remain poorly understood. Here we investigated blink suppression by analyzing fMRI data in a block design and event-related manner, and employed a novel hypothetical time-varying neural response model to detect brain activations associated with the buildup of urge. Blinks were found to activate visual cortices while our block design analysis revealed activations limited to the middle occipital gyri and deactivations in medial occipital, posterior cingulate and precuneus areas. Our model for urge, however, revealed a widespread network of activations including right greater than left insular cortex, right ventrolateral prefrontal cortex, middle cingulate cortex, and bilateral temporo-parietal cortices, primary and secondary face motor regions, and visual cortices. Subsequent inspection of BOLD time-series in an extensive ROI analysis showed that activity in the bilateral insular cortex, right ventrolateral prefrontal cortex, and bilateral STG and MTG showed strong correlations with our hypothetical model for urge suggesting these areas play a prominent role in the buildup of urge. The involvement of the insular cortex in particular, along with its function in interoceptive processing, helps support a key role for this structure in the buildup of urge during blink suppression. The right ventrolateral prefrontal cortex findings in conjunction with its known involvement in inhibitory control suggest a role for this structure in maintaining volitional suppression of an increasing sense of urge. The consistency of our urge model findings with prior studies investigating the suppression of blinking and other bodily urges, thoughts, and behaviors suggests that a similar investigative approach may have utility in fMRI studies of disorders associated with abnormal urge suppression such as Tourette syndrome and obsessive-compulsive disorder.     

The neural correlates of cross-modal interaction in speech perception during a semantic decision task on sentences: a PET study

Speech perception in face-to-face conversation involves processing of speech sounds (auditory) and speech-associated mouth/lip movements (visual) from a speaker. Using PET where no scanner noise was present, brain regions involved in speech cue processing were investigated with the normal hearing subjects with no previous lip-reading training (N = 17) carrying out a semantic plausibility decision on spoken sentences delivered in a movie file. Multimodality was ensured at the sensory level in all four conditions. Sensory-specific speech cue of one sensory modality, i.e., auditory speech (A condition) or mouth movement (V condition), was delivered with a control stimulus of the other modality whereas speech cues of both sensory modalities (AV condition) were delivered during bimodal condition. In comparison to the control condition, extensive activations in the superior temporal regions were observed bilaterally during the A condition but these activations were reduced in extent and left lateralized during the AV condition. Polymodal region such as left posterior superior temporal sulcus (pSTS) involved in cross-modal interaction/integration of audiovisual speech was found to be activated during the A and more so during the AV conditions but not during the V condition. Activations were observed in Broca's (BA 44), medial frontal (BA 8), and anterior ventrolateral prefrontal (BA 47) regions in the left during the V condition, where lip-reading performance was less successful. Results indicated that the speech-associated lip movements (visual speech cue) rendered suppression on the activity in the right auditory temporal regions. Overadditivity (AV > A + V) observed in the right postcentral region during the bimodal condition relative to the sum of unimodal speech conditions was also associated with reduced activity during the V condition. These findings suggested that visual speech cue could exert an inhibitory modulatory effect on the brain activities in the right hemisphere during the cross-modal interaction of audiovisual speech perception.     

Neural correlates of semantic and behavioural deficits in frontotemporal dementia

Patients with frontotemporal dementia (FTD) can present with the clinical syndrome of semantic dementia due to a progressive loss of semantic knowledge or a neuropsychiatric syndrome characterised by aberrant social behaviours although frequently both co-exist. It has been assumed that the former is underpinned by damage to the temporal lobes and the latter, predominantly, by damage to the frontal lobes. Using the technique of voxel-based morphometry, we studied a group of FTD cases (n = 18) with a range of cognitive and neuropsychiatric features to correlate loss of semantic knowledge (as measured by the sum of two semantic tests) and aberrant behaviour (as measured by the neuropsychiatric inventory, NPI) with regional loss of grey matter volume. Semantic breakdown correlated with extensive loss of grey matter volume throughout the left anterior temporal lobe and less significantly with right temporal pole and subcallosal gyrus. Aberrant behaviour correlated with loss of grey matter volume in the dorso-mesial frontal lobe--paracingulate region, Brodmann areas 6/8/9--more so on the right. The frontal paracingulate correlation suggests that damage to this region may significantly contribute to the genesis of the behavioural syndrome seen in FTD.     

Left inferior prefrontal cortex activation during a semantic decision-making task predicts the degree of semantic organization

Semantic organization, an aspect of semantic processing, requires a pre-existing network of semantic knowledge that relies on a widely distributed neural network. The inferior prefrontal cortex (IPFC) has been identified as a vital structure for processing competing semantic information when making a decision about the meaning of a stimulus. However, the precise role of the IPFC in maintaining or creating a consistent semantic organizational structure is unclear. In this study, a semantic triadic decision-making task (Tallent, K.A., Weinberger, D.R., and Goldberg, T.E. 2001. Associating semantic space abnormalities with formal thought disorder in schizophrenia: use of triadic comparisons. J. Clin. Exp. Neuropsychol. 285-296) was used during functional magnetic resonance imaging to test the hypothesis that the degree of activation in the IPFC correlates with the consistency of semantic organization in healthy subjects. In this sample, subjects who had greater activation in the IPFC also demonstrated smaller stress coefficients in a two-dimensional "semantic space", indicating a greater organization of words along semantic dimensions. This finding is consistent with the role of the IPFC in establishing self-generated semantic relationships between stimuli.     

Dissociating neural correlates for nouns and verbs

Dissociations in the ability to produce words of different grammatical categories are well established in neuropsychology but have not been corroborated fully with evidence from brain imaging. Here we report on a PET study designed to reveal the anatomical correlates of grammatical processes involving nouns and verbs. German-speaking subjects were asked to produce either plural and singular nouns, or first-person plural and singular verbs. Verbs, relative to nouns, activated a left frontal cortical network, while the opposite contrast (nouns-verbs) showed greater activation in temporal regions bilaterally. Similar patterns emerged when subjects performed the task with pseudowords used as nouns or as verbs. These results converge with findings from lesion studies and suggest that grammatical category is an important dimension of organization for knowledge of language in the brain.     

The neural correlates of subjective pleasantness

Processing of subjective pleasantness is essential in daily life decision making, particularly in the context of cognitive and environmental factors. Pleasure is mediated by a neural network and this network has been suggested to be the biological basis of pleasure including a whole range of different modalities and domains of pleasantness. This quantitative meta-analysis of brain imaging data focuses on studies 1) based on correlations between self-reported judgements of pleasantness and brain regions and investigates whether 2) immediate (during scanning) versus subsequent judgements (after scanning) differ in brain activity. We investigated concurrence across 40 studies reporting brain regions correlated with self-reported judgements of subjective pleasantness (attractiveness, liking or beauty) by means of activation likelihood estimation (ALE). Positive correlates of subjective pleasantness were found in mOFC, ventromedial prefrontal cortex, left ventral striatum, pregenual cortex, right cerebellum, left thalamus and the mid cingulate cortex. Negative correlates were found in left precentral gyrus, right cerebellum and right inferior frontal gyrus. A comparison of studies with subjective pleasantness judgement during or after scanning revealed no significant differences in brain activation. We conclude that subjective pleasantness judgements are directly related to brain regions that have been described as part of the reward circuitry (mOFC, ventral striatum). The results suggest that the evaluation of likability or pleasure is an automatic process and that it is neither elicited nor enhanced by instructions to report the outcome of these judgements.     

Functional neural correlates of fluid and crystallized analogizing

The main aim of this study was to characterize neural correlates of analogizing as a cognitive contributor to fluid and crystallized intelligence. In a previous fMRI study which employed fluid analogy letter strings as criteria in a multiple plausibility design (Geake and Hansen, 2005), two frontal ROIs associated with working memory (WM) load (within BA 9 and BA 45/46) were identified as regions in which BOLD increase correlated positively with a crystallized measure of (verbal) IQ. In this fMRI study we used fluid letter, number and polygon strings to further investigate the role of analogizing in fluid (transformation string completion) and non fluid or crystallized (unique symbol counting) cognitive tasks. The multi stimulus type (letter, number, polygon) design of the analogy strings enabled investigation of a secondary research question concerning the generalizability of fluid analogizing at a neural level. A selective psychometric battery, including the Raven's Progressive Matrices (RPM), measured individual cognitive abilities. Neural activations for the effect of task–fluid analogizing (string transformation plausibility) vs. crystallized analogizing (unique symbol counting)–included bilateral frontal and parietal areas associated with WM load and fronto parietal models of general intelligence. Neural activations for stimulus type differences were mainly confined to visually specific posterior regions. ROI covariate analyses of the psychometric measures failed to find consistent co-relationships between fluid analogizing and the RPM and other subtests, except for the WAIS Digit Symbol subtest in a group of bilateral frontal cortical regions associated with the maintenance of WM load. Together, these results support claims for separate developmental trajectories for fluid cognition and general intelligence as assessed by these psychometric subtests.     

The neural correlates of direct and reflected self-knowledge

Socrates said that in order to lead a balanced life one must, "know thyself." In two fMRI experiments, the present study examined the mechanisms mediating two ways in which the self can be known: through direct appraisals (i.e., an individual's own self-beliefs) and reflected appraisals (i.e., an individual's perception of how others view him or her). Experiment 1 examined the common and distinct neural bases of direct appraisals of the self, close others, and normative judgments of trait desirability. All three judgment types activated medial prefrontal cortex (MPFC) to a similar degree. Experiment 2 examined the common and distinct neural bases of (1) direct appraisals of self, a close other or a non-close other, and (2) reflected appraisals made from the perspective of a close or a non-close other. Consistent with Experiment 1, all judgment types activated MPFC. Direct appraisals of the self as compared to others more strongly recruited MPFC and right rostrolateral PFC. Direct appraisals as compared to reflected appraisals recruited regions associated with a first-person perspective (posterior cingulate), whereas reflected as compared to direct appraisals recruited regions associated with emotion and memory (insula, orbitofrontal, and temporal cortex). These results support models suggesting that MPFC mediates meta-cognitive processes that may be recruited for direct and reflected self appraisals depending upon the demands of a specific task.     

The neural correlates of maternal and romantic love

Romantic and maternal love are highly rewarding experiences. Both are linked to the perpetuation of the species and therefore have a closely linked biological function of crucial evolutionary importance. Yet almost nothing is known about their neural correlates in the human. We therefore used fMRI to measure brain activity in mothers while they viewed pictures of their own and of acquainted children, and of their best friend and of acquainted adults as additional controls. The activity specific to maternal attachment was compared to that associated to romantic love described in our earlier study and to the distribution of attachment-mediating neurohormones established by other studies. Both types of attachment activated regions specific to each, as well as overlapping regions in the brain's reward system that coincide with areas rich in oxytocin and vasopressin receptors. Both deactivated a common set of regions associated with negative emotions, social judgment and 'mentalizing', that is, the assessment of other people's intentions and emotions. We conclude that human attachment employs a push-pull mechanism that overcomes social distance by deactivating networks used for critical social assessment and negative emotions, while it bonds individuals through the involvement of the reward circuitry, explaining the power of love to motivate and exhilarate.     

语义记忆损伤的检测及神经机制

脑损害患者存在的语义范畴特异性损伤现象激发了人们对语义知识神经表征规则的研究。传统的神经心理学检查法及功能成像技术是研究语义记忆神经基础的主要方法。神经心理学是通过研究患者脑损伤部位与其损伤的语义知识范畴间的关系来推断语义知识的神经基础;而功能成像技术是通过直接检测正常人在提取各范畴语义知识时的脑活动模式来揭示语义知识的神经基础。因此,作为语义记忆探测材料的认知任务的设置直接影响到研究的效度与结果。因各研究所用的认知任务不同,研究结果与结论也呈现出较大的分歧,部分学者认为语义记忆是一单一的统一体,但部分学者认为语义记忆是一由类别子系统或是通道子系统组成的集合体。     

Neural correlates of regulating negative emotions related to moral violations

Previous neuroimaging studies have identified several brain regions associated with regulating emotional responses. Different kinds of emotional stimuli, however, may recruit different regulatory processes and, in turn, recruit different regions. We compared emotion regulation for two types of negative emotional stimuli: those involving moral violations (moral stimuli), and those not involving moral violations (non-moral stimuli). In addition, we investigated whether activation in medial prefrontal cortex (MPFC), a region implicated previously in specifically moral processing, may instead reflect greater social and emotional content. Ten female subjects were scanned using fMRI while they passively viewed or were instructed to decrease emotional reactions to moral and non-moral pictures closely matched on social and emotional content. Passive viewing of both picture types elicited similar activations in areas related to the processing of social and emotional content, including MPFC and amygdala. During regulation, different patterns of activation in these regions were observed for moral vs. non-moral pictures. These results suggest that the neural correlates of regulating emotional reactions are modulated by the emotional content of stimuli, such as moral violations. In addition, the current findings suggest that some brain regions previously implicated in moral processing reflect the processing of greater social and emotional content in moral stimuli.     

Shared and distinct neural correlates of singing and speaking

Using a modified sparse temporal sampling fMRI technique, we examined both shared and distinct neural correlates of singing and speaking. In the experimental conditions, 10 right-handed subjects were asked to repeat intoned ("sung") and non-intoned ("spoken") bisyllabic words/phrases that were contrasted with conditions controlling for pitch ("humming") and the basic motor processes associated with vocalization ("vowel production"). Areas of activation common to all tasks included the inferior pre- and post-central gyrus, superior temporal gyrus (STG), and superior temporal sulcus (STS) bilaterally, indicating a large shared network for motor preparation and execution as well as sensory feedback/control for vocal production. The speaking more than vowel-production contrast revealed activation in the inferior frontal gyrus most likely related to motor planning and preparation, in the primary sensorimotor cortex related to motor execution, and the middle and posterior STG/STS related to sensory feedback. The singing more than speaking contrast revealed additional activation in the mid-portions of the STG (more strongly on the right than left) and the most inferior and middle portions of the primary sensorimotor cortex. Our results suggest a bihemispheric network for vocal production regardless of whether the words/phrases were intoned or spoken. Furthermore, singing more than humming ("intoned speaking") showed additional right-lateralized activation of the superior temporal gyrus, inferior central operculum, and inferior frontal gyrus which may offer an explanation for the clinical observation that patients with non-fluent aphasia due to left hemisphere lesions are able to sing the text of a song while they are unable to speak the same words.     

工作场所暴力对护士护理伦理决策能力的影响

目的了解护士工作场所暴力和护理伦理决策现状,探讨工作场所暴力对护士护理伦理决策能力的影响。方法采用工作场所暴力问卷和护士护理伦理决策问卷对693名临床护士进行问卷调查。结果 1年内护士工作场所暴力发生率为66.09%,其中心理暴力占74.89%;身体暴力占18.12%;性暴力占6.99%。暴力组伦理选择、伦理行动和伦理决策能力总分均显著低于非暴力组,差异均具有统计学意义(P0.01);不同工作场所暴力形式及暴力频次护士护理伦理决策能力比较,差异具有统计学意义(P0.01)。是否遭受工作场所暴力和学历是护士伦理决策能力的影响因素。结论护士工作场所暴力发生率较高,遭受工作场所暴力的护士护理伦理决策能力下降,遭受暴力程度越严重、频次越多,护士护理伦理决策能力越差。     

Tracking neural coding of perceptual and semantic features of concrete nouns

We present a methodological approach employing magnetoencephalography (MEG) and machine learning techniques to investigate the flow of perceptual and semantic information decodable from neural activity in the half second during which the brain comprehends the meaning of a concrete noun. Important information about the cortical location of neural activity related to the representation of nouns in the human brain has been revealed by past studies using fMRI. However, the temporal sequence of processing from sensory input to concept comprehension remains unclear, in part because of the poor time resolution provided by fMRI. In this study, subjects answered 20 questions (e.g. is it alive?) about the properties of 60 different nouns prompted by simultaneous presentation of a pictured item and its written name. Our results show that the neural activity observed with MEG encodes a variety of perceptual and semantic features of stimuli at different times relative to stimulus onset, and in different cortical locations. By decoding these features, our MEG-based classifier was able to reliably distinguish between two different concrete nouns that it had never seen before. The results demonstrate that there are clear differences between the time course of the magnitude of MEG activity and that of decodable semantic information. Perceptual features were decoded from MEG activity earlier in time than semantic features, and features related to animacy, size, and manipulability were decoded consistently across subjects. We also observed that regions commonly associated with semantic processing in the fMRI literature may not show high decoding results in MEG. We believe that this type of approach and the accompanying machine learning methods can form the basis for further modeling of the flow of neural information during language processing and a variety of other cognitive processes.