Weaker top-down modulation from the left inferior frontal gyrus in children

Previous studies have shown that developmental changes in the structure and function of prefrontal regions can continue throughout childhood and adolescence. Our recent results suggested a role for the left inferior frontal cortex in modulating task-dependent shifts in effective connectivity when adults focus on orthographic versus phonological aspects of presented words. Specifically, the top-down influence of the inferior frontal cortex determined whether incoming word-form information from the fusiform gyrus would have a greater impact on the parietal areas involved in orthographic processing or temporal areas involved in phonological processing (Bitan, T., Booth, J.R., Choy, J., Burman, D.D., Gitelman, D.R. and Mesulam, M.-M., 2005. Shifts of Effective Connectivity within a Language Network during Rhyming and Spelling. J. Neurosci. 25, 5397-5403.). In the current study, we find that children displayed an identical pattern of task-dependent functional activations within this network. In comparison to adults, however, children had significantly weaker top-down modulatory influences emanating from the inferior frontal area. Adult language processing may thus involve greater top-down cognitive control compared to children, resulting in less interference from task-irrelevant information.     

Socioeconomic status predicts hemispheric specialisation of the left inferior frontal gyrus in young children

Reading is a complex skill that is not mastered by all children. At the age of 5, on the cusp of prereading development, many factors combine to influence a child's future reading success, including neural and behavioural factors such as phonological awareness and the auditory processing of phonetic input, and environmental factors, such as socioeconomic status (SES). We investigated the interactions between these factors in 5-year-old children by administering a battery of standardised cognitive and linguistic tests, measuring SES with a standardised scale, and using fMRI to record neural activity during a behavioral task, rhyming, that is predictive of reading skills. Correlation tests were performed, and then corrected for multiple comparisons using the false discovery rate (FDR) procedure. It emerged that only one relationship linking neural with behavioural or environmental factors survived as significant after FDR correction: a correlation between SES and the degree of hemispheric specialisation in the left inferior frontal gyrus (IFG), a region which includes Broca's area. This neural-environmental link remained significant even after controlling for the children's scores on the standardised language and cognition tests. In order to investigate possible environmental influences on the left IFG further, grey and white matter volumes were calculated. Marginally significant correlations with SES were found, indicating that environmental effects may manifest themselves in the brain anatomically as well as functionally. Collectively, these findings suggest that the weaker language skills of low-SES children are related to reduced underlying neural specialisation, and that these neural problems go beyond what is revealed by behavioural tests alone.     

The anterior left inferior frontal gyrus contributes to semantic unification

Semantic unification, the process by which small blocks of semantic information are combined into a coherent utterance, has been studied with various types of tasks. However, whether the brain activations reported in these studies are attributed to semantic unification per se or to other task-induced concomitant processes still remains unclear. The neural basis for semantic unification in sentence comprehension was examined using event-related potentials (ERP) and functional Magnetic Resonance Imaging (fMRI). The semantic unification load was manipulated by varying the goodness of fit between a critical word and its preceding context (in high cloze, low cloze and violation sentences). The sentences were presented in a serial visual presentation mode. The participants were asked to perform one of three tasks: semantic congruency judgment (SEM), silent reading for comprehension (READ), or font size judgment (FONT), in separate sessions. The ERP results showed a similar N400 amplitude modulation by the semantic unification load across all of the three tasks. The brain activations associated with the semantic unification load were found in the anterior left inferior frontal gyrus (aLIFG) in the FONT task and in a widespread set of regions in the other two tasks. These results suggest that the aLIFG activation reflects a semantic unification, which is different from other brain activations that may reflect task-specific strategic processing.     

Neuroimaging-guided rTMS of the left inferior frontal gyrus interferes with repetition priming

Neuroimaging studies of right-handed normal volunteers under semantic word generation tasks have consistently reported left lateralized activation of the anterior inferior frontal gyrus (ifg) which decreased during task repetition. This repetition-related activation decrease has been interpreted as the neurophysiological correlate of repetition priming, a mechanism of implicit memory for initial semantic processing. We interfered with left lateralized ifg activation, as identified by O-15-water PET activation, using repetitive transcranial magnetic stimulation (rTMS) in five right-handed male normal subjects, once using new (unprimed) nouns and once using known (primed) nouns for the procedure. All five subjects exhibited clear left lateralized activations of the triangular part of the left ifg in the PET studies. In all subjects, reaction time latencies were significantly longer during rTMS over the activation sites in the left ifg as compared to latencies off stimulation. Latencies were not affected during stimulation of the right ifg or over the vertex. These effects were observed within the group and in each individual, only if lists of primed nouns were used in the verb-generation task. In conclusion, these results demonstrate that the anterior part of the left ifg is not only involved in semantic processing, but is also essential for repetition priming on semantic tasks since successful interference with rTMS was only observed if lists of primed words were used for the generation task.     

Gender differences in the activation of inferior frontal cortex during emotional speech perception

We investigated the brain regions that mediate the processing of emotional speech in men and women by presenting positive and negative words that were spoken with happy or angry prosody. Hence, emotional prosody and word valence were either congruous or incongruous. We assumed that an fRMI contrast between congruous and incongruous presentations would reveal the structures that mediate the interaction of emotional prosody and word valence. The left inferior frontal gyrus (IFG) was more strongly activated in incongruous as compared to congruous trials. This difference in IFG activity was significantly larger in women than in men. Moreover, the congruence effect was significant in women whereas it only appeared as a tendency in men. As the left IFG has been repeatedly implicated in semantic processing, these findings are taken as evidence that semantic processing in women is more susceptible to influences from emotional prosody than is semantic processing in men. Moreover, the present data suggest that the left IFG mediates increased semantic processing demands imposed by an incongruence between emotional prosody and word valence.     

Memory of music: roles of right hippocampus and left inferior frontal gyrus

We investigated neural correlates of retrieval success for music memory using event-related functional magnetic resonance imaging. To minimize the interference from MRI scan noise, we used sparse temporal sampling technique. Newly composed music materials were employed as stimuli, which enabled us to detect regions in absence of effects of experience with the music stimuli in this study. Whole brain analyses demonstrated significant retrieval success activities in the right hippocampus, bilateral lateral temporal regions, left inferior frontal gyrus and left precuneus. Anatomically defined region-of-interests analyses showed that the activity of the right hippocampus was stronger than that of the left, while the activities of the inferior frontal gyri showed the reverse pattern. Furthermore, performance-based analyses demonstrated that the retrieval success activity of the right hippocampus was positively correlated with the corrected recognition rate, suggesting that the right hippocampus contributes to the accuracy of music retrieval outcome.     

Selective attention modulates inferior frontal gyrus activity during action observation

Our ability to recognize the actions of others is subserved by a complex network of brain areas, including the inferior frontal gyrus (IFG), inferior parietal lobe (IPL) and superior temporal sulcus (STS). An unresolved issue is whether the activity within these regions requires top-down control or whether it arises relatively automatically during passive action observation. Here we used fMRI to determine whether cortical activity associated with action observation is modulated by the strategic allocation of selective attention. Participants observed moving and stationary images of reach-to-grasp hand actions, while they performed an attentionally demanding task at the fovea. We first defined regions-of-interest (ROIs) in the IFG, IPL and STS which responded to the perception of these actions. We then probed these ROIs while participants observed the identical, but now task-irrelevant, actions and instead performed an easy (low attentional load) or difficult (high attentional load) visual discrimination task. Our data indicate that the activity of the left IFG was consistently attenuated under conditions of high attentional load, while the remaining action observation areas remained relatively unaffected by attentional manipulations. The suppression of the left IFG was unique to the observation of hand actions, and did not occur during the observation of non-biological control stimuli, in the form of coherent dot motion. We propose that the left IFG is the site at which descending inhibitory processes affect the processing of observed actions, and that the attentional modulation of this region is responsible for filtering task-irrelevant actions during ongoing behavior.     

Functional organization of the left inferior precentral sulcus: dissociating the inferior frontal eye field and the inferior frontal junction

Two eye fields have been described in the human lateral frontal cortex: the frontal eye field (FEF) and the inferior frontal eye field (iFEF). The FEF has been extensively studied and has been found to lie at the ventral part of the superior precentral sulcus. Much less research, however, has focused on the iFEF. Recently, it was suggested that the iFEF is located at the dorsal part of the inferior precentral sulcus. A similar location was proposed for the inferior frontal junction area (IFJ), an area thought to be involved in cognitive control processes. The present study used fMRI to clarify the topographical and functional relationship of the iFEF and the IFJ in the left hemispheres of individual participants. The results show that both the iFEF and the IFJ are indeed located at the dorsal part of the inferior precentral sulcus. Nevertheless, the activations were spatially dissociable in every individual examined. The IFJ was located more towards the depth of the inferior precentral sulcus, close to the junction with the inferior frontal sulcus, whereas the iFEF assumed a more lateral, posterior and superior position. Furthermore, the results provided evidence for a functional double dissociation: the iFEF was activated only in a comparison of saccades vs. button presses, but not in a comparison of incongruent vs. congruent Stroop conditions, while the opposite pattern was found at the IFJ. These results provide evidence for a spatial and functional dissociation of two directly adjacent areas in the left posterior frontal lobe.     

Dissociable roles of human inferior frontal gyrus during action execution and observation

There has been recent controversy about whether activation in the human inferior frontal gyrus (IFG) and Brodmann Area (BA) 6 when observing actions indicates operation of mirror neurons. Recent functional magnetic resonance imaging (fMRI) data have demonstrated repetition suppression (RS) effects in posterior IFG which are consistent with the presence of mirror neurons in humans. Here we investigated whether there were similar RS effects elsewhere in the IFG and BA6, or whether, instead, activation in other locations may signal operation of alternative mechanisms. Replicating previous findings, we found RS effects in posterior IFG consistent with the operation of mirror neurons. However, these effects were not found in other locations in IFG and BA6. Additionally, activation patterns in anterior regions of IFG suggested dissociable operations when observing and executing actions. Therefore, caution should be exercised when claiming that activations in many locations during action observation indicate the operation of mirror neurons. Activation may instead reflect alternative mechanisms, such as encoding of the semantic features of actions.     

The left occipitotemporal system in reading: disruption of focal fMRI connectivity to left inferior frontal and inferior parietal language areas in children with dyslexia

Developmental dyslexia is a severe reading disorder, which is characterized by dysfluent reading and impaired automaticity of visual word processing. Adults with dyslexia show functional deficits in several brain regions including the so-called "Visual Word Form Area" (VWFA), which is implicated in visual word processing and located within the larger left occipitotemporal VWF-System. The present study examines functional connections of the left occipitotemporal VWF-System with other major language areas in children with dyslexia. Functional connectivity MRI was used to assess connectivity of the VWF-System in 18 children with dyslexia and 24 age-matched controls (age 9.7-12.5 years) using five neighboring left occipitotemporal regions of interest (ROIs) during a continuous reading task requiring phonological and orthographic processing. First, the results revealed a focal origin of connectivity from the VWF-System, in that mainly the VWFA was functionally connected with typical left frontal and parietal language areas in control children. Adjacent posterior and anterior VWF-System ROIs did not show such connectivity, confirming the special role that the VWFA plays in word processing. Second, we detected a significant disruption of functional connectivity between the VWFA and left inferior frontal and left inferior parietal language areas in the children with dyslexia. The current findings add to our understanding of dyslexia by showing that functional disconnection of the left occipitotemporal system is limited to the small VWFA region crucial for automatic visual word processing, and emerges early during reading acquisition in children with dyslexia, along with deficits in orthographic and phonological processing of visual word forms.     

Activity of left inferior frontal gyrus related to word repetition effects: LORETA imaging with 128-channel EEG and individual MRI

We investigated the brain substrate of word repetition effects on the implicit memory task using low-resolution electromagnetic tomography (LORETA) with high-density 128-channel EEG and individual MRI as a realistic head model. Thirteen right-handed, healthy subjects performed a word/non-word discrimination task, in which the words and non-words were presented visually, and some of the words appeared twice with a lag of one or five items. All of the subjects exhibited word repetition effects with respect to the behavioral data, in which a faster reaction time was observed to the repeated word (old word) than to the first presentation of the word (new word). The old words elicited more positive-going potentials than the new words, beginning at 200 ms and lasting until 500 ms post-stimulus. We conducted source reconstruction using LORETA at a latency of 400 ms with the peak mean global field potentials and used statistical parametric mapping for the statistical analysis. We found that the source elicited by the old words exhibited a statistically significant current density reduction in the left inferior frontal gyrus. This is the first study to investigate the generators of word repetition effects using voxel-by-voxel statistical mapping of the current density with individual MRI and high-density EEG.     

Contribution of the left and right inferior frontal gyrus in recovery from aphasia. A functional MRI study in stroke patients with preserved hemodynamic responsiveness

The relative contribution of dominant and non-dominant language networks to recovery from aphasia is a matter of debate. We assessed with functional magnetic resonance imaging (fMRI) to what extent the left and right hemispheres are associated with recovery from aphasia after stroke. fMRI with three language tasks was performed in 13 aphasic stroke patients and in 13 healthy subjects. Severity of aphasia was examined within 2 months after stroke and after at least 1 year. Recovery of naming ability and scores on the Token Test were correlated with data from fMRI in the chronic phase. A breath-hold paradigm was used to investigate hemodynamic responsiveness.Overall language performance in the chronic phase correlated with higher relative activation of left compared to right perisylvian areas. Recovery of naming ability was positively correlated with activation in the left inferior frontal gyrus (IFG) for semantic decision and verb generation. Recovery on the Token Test was positively correlated with activation in both left and right IFG during semantic decision and verb generation. Hemodynamic response to the breath-hold task was similar in patients and controls.Our study suggests that in the chronic stage after stroke left IFG activity is associated with improvement of picture naming and sentence comprehension, whereas activity in the right IFG may reflect up-regulation of non-linguistic cognitive processing. Altered hemodynamic responsiveness seems an unlikely confounder in the interpretations of fMRI results.     

性别差异与儿童情绪发展

目的:探讨性别差异对儿童情绪发展和社会化的制约作用,为制定相关干预措施提供理论依据。方法:从社会参照、教育互动、性别认同、同伴交往等角度加以比较。结果:社会参照及其强化,使得儿童的情绪发展在婴儿期就显现出方向、内容上的性别差异;由于与性别相关的先天差异的存在,成人与儿童进行教育互动时,常常会因其性别差异给予不同的教育要求和指导;当儿童开始有了自己的性别认同时,儿童的情绪行为开始逐渐向自己的性别角色定型靠拢;随着儿童年龄的增长,同伴之间的交往对儿童情绪发展的性别角色定型的制约作用日益明显。结论:性别差异构成儿童社会实践和个体社会化的心理基础,使得男女两性在认知、情绪乃至个性的发展上呈现出不同的轨迹。父母能否以与特定性别相适应的方式对待和教育儿童,直接影响儿童能否正常地适应社会生活,能否安然地接受自己的性别特征。     

Retrieving autobiographical memories of painful events activates the anterior cingulate cortex and inferior frontal gyrus.

Patients will often reflect on the meaning of a painful episode, as, for example, when completing questionnaire measures of subjective pain experience or in clinical interviews. Neuroimaging studies of the human cortical and subcortical physical pain response have identified a neural network consistently referred to as the "pain matrix." We used functional magnetic resonance imaging to investigate whether the pain matrix could be activated through the retrieval of memories relating to previously painful events, in the absence of any direct peripheral noxious input. Fourteen pain-free participants were explicitly instructed to recall autobiographical memories of painful episodes in response to pain-related words and non-painful episodes in response to equally salient but non-pain words. Memories triggered by pain-related words produced significantly greater activation of left caudal anterior cingulate cortex (BA32'), and left inferior frontal gyrus (BA44, extending to BA47/45) more than memories triggered by equally salient but non-pain words. We suggest that these activations demonstrate a semantic retrieval process for pain-related memories, which may provide a means of cognitively reappraising the memory of the painful episode, thus allowing the person to elaborate on the circumstances surrounding the event, without physically re-experiencing it. PERSPECTIVE: The present study reveals a putative neural mechanism for the retrieval of autobiographical memories of previously painful events, which may provide a means of cognitively reappraising a painful episode, without physically re-experiencing it. This finding has implications for understanding disease mechanisms of chronic pain and their impact on subsequent treatment.     

Evaluating the roles of the inferior frontal gyrus and superior parietal lobule in deductive reasoning: an rTMS study

This study used off-line repetitive transcranial magnetic stimulation (rTMS) to examine the roles of the superior parietal lobule (SPL) and inferior frontal gyrus (IFG) in a deductive reasoning task. Subjects performed a categorical syllogistic reasoning task involving congruent, incongruent, and abstract trials. Twenty four subjects received magnetic stimulation to the SPL region prior to the task. In the other 24 subjects, TMS was administered to the IFG region before the task. Stimulation lasted for 10min, with an inter-pulse frequency of 1Hz. We found that bilateral SPL (Brodmann area (BA) 7) stimulation disrupted performance on abstract and incongruent reasoning. Left IFG (BA 45) stimulation impaired congruent reasoning performance while paradoxically facilitating incongruent reasoning performance. This resulted in the elimination of the belief-bias. In contrast, right IFG stimulation only impaired incongruent reasoning performance, thus enhancing the belief-bias effect. These findings are largely consistent with the dual-process theory of reasoning, which proposes the existence of two different human reasoning systems: a belief-based heuristic system; and a logic-based analytic system. The present findings suggest that the left language-related IFG (BA 45) may correspond to the heuristic system, while bilateral SPL may underlie the analytic system. The right IFG may play a role in blocking the belief-based heuristic system for solving incongruent reasoning trials. This study could offer an insight about functional roles of distributed brain systems in human deductive reasoning by utilizing the rTMS approach.     

On why the elderly have normal semantic retrieval but deficient episodic encoding: a study of left inferior frontal ERP activity

Age-related left inferior prefrontal cortex (LIPFC) blood flow reductions during semantic retrieval are associated with reduced subsequent episodic recognition memory performance but are inconsistent with age-invariant semantic retrieval performance. Therefore, we compared brain activity in young and elderly persons during low- and high-selection versions of a semantic task using ERPs recorded at 62 scalp locations. In an early interval (400-800 ms), both age groups showed more negativity over left inferior frontal scalp while performing the high- compared to the low-selection task. This early semantic selection-related negativity was associated with age-equivalent accuracy and reaction time on the semantic tasks. Further, in the early time interval, the ERPs of the young were more negative than those of the elderly. In addition, only the young showed a late selection-related negativity (1,200--1,400 ms). These age-related differences in left frontal ERP activity were associated with significant decrements in subsequent recognition for the elderly. Moreover, additional analyses revealed that larger amounts of negativity over left inferior frontal scalp locations during semantic retrieval were correlated with enhanced subsequent episodic recognition in both groups. In sum, the data suggest that (1) semantic retrieval and episodic encoding processes overlap temporally in similar brain regions, most likely including the LIPFC, and (2) the failure to recruit these regions in the service of episodic encoding underlies the age-related deficit in episodic memory.     

Gender differences of parental distress in children with cancer

AIMS: The aim of this paper is to provide an in-depth analysis of the concept of equity in the British health visiting service and thus facilitate understanding of the term. An attempt has been made to apply the analytical process to the context of health visiting. BACKGROUND: Equity has been discussed at some length in the health literature. Much of this including the health visiting literature discusses inequality and inequalities in health at the same time as discussing equity. Increasingly, poverty and inequalities have become accepted as determinants in poor health. It seemed appropriate therefore to analyse these topical and seemingly related concepts. METHODS: A well established method of concept analysis has been utilized to facilitate the process of analysis. RESULTS: Confusion between the meaning and application of the concepts of equity and equality was found. Much of the health visiting and health care literature related to addressing the needs of groups who experience inequality in terms of service provision, and access to services. Following an in-depth critical analysis of the literature three critical attributes of the concept were identified: equal opportunity of access to services; a high standard of service for everyone; and unequal distribution of services to meet unequal need. These relate to two distinct forms of equity: horizontal and vertical equity. A definition of equity has been proposed. Maxwell's (1992) framework is suggested as a means to evaluate equity in service provision and uptake. CONCLUSIONS: Most of the literature examines equity at a macro level, that is service level. Nurses and health visitors are urged to examine the services that they are involved in to determine the level of equity that is achieved or not attained. Suggestions have been offered as to how this task may be undertaken. A definition has been proposed to stimulate debate and discussion about the concept within nursing contexts.     

The role of precuneus and left inferior frontal cortex during source memory episodic retrieval

The posterior medial parietal cortex and left prefrontal cortex (PFC) have both been implicated in the recollection of past episodes. In a previous study, we found the posterior precuneus and left lateral inferior frontal cortex to be activated during episodic source memory retrieval. This study further examines the role of posterior precuneal and left prefrontal activation during episodic source memory retrieval using a similar source memory paradigm but with longer latency between encoding and retrieval. Our results suggest that both the precuneus and the left inferior PFC are important for regeneration of rich episodic contextual associations and that the precuneus activates in tandem with the left inferior PFC during correct source retrieval. Further, results suggest that the left ventro-lateral frontal region/frontal operculum is involved in searching for task-relevant information (BA 47) and subsequent monitoring or scrutiny (BA 44/45) while regions in the dorsal inferior frontal cortex are important for information selection (BA 45/46).     

Roles for the pre-supplementary motor area and the right inferior frontal gyrus in stopping action: electrophysiological responses and functional and structural connectivity

Both the pre-supplementary motor area (preSMA) and the right inferior frontal gyrus (rIFG) are important for stopping action outright. These regions are also engaged when preparing to stop. We aimed to elucidate the roles of these regions by harnessing the high spatio-temporal resolution of electrocorticography (ECoG), and by using a task that engages both preparing to stop and stopping outright. First, we validated the task using fMRI in 16 healthy control participants to confirm that both the preSMA and the rIFG were active. Next, we studied a rare patient with intracranial grid coverage of both these regions, using macrostimulation, diffusion tractography, cortico-cortical evoked potentials (CCEPs) and task-based ECoG. Macrostimulation of the preSMA induced behavioral motor arrest. Diffusion tractography revealed a structural connection between the preSMA and rIFG. CCEP analysis showed that stimulation of the preSMA evoked strong local field potentials within 30 ms in rIFG. During the task, when preparing to stop, there was increased high gamma amplitude (~ 70-250 Hz) in both regions, with preSMA preceding rIFG by ~ 750 ms. For outright stopping there was also a high gamma amplitude increase in both regions, again with preSMA preceding rIFG. Further, at the time of stopping, there was an increase in beta band activity (~ 16 Hz) in both regions, with significantly stronger inter-regional coherence for successful vs. unsuccessful stop trials. The results complement earlier reports of a structural/functional action control network between the preSMA and rIFG. They go further by revealing between-region timing differences in the high gamma band when preparing to stop and stopping outright. They also reveal strong between-region coherence in the beta band when stopping is successful. Implications for theories of action control are discussed.     

Contingency awareness in human aversive conditioning involves the middle frontal gyrus

In contrast to the wealth of data describing the neural mechanisms underlying classical conditioning, we know remarkably little about the mechanisms involved in acquisition of explicit contingency awareness. Subjects variably acquire contingency awareness in classical conditioning paradigms, in which they are able to describe the temporal relationship between a conditioned cue and its outcome. Previous studies have implicated the hippocampus and prefrontal cortex in the acquisition of explicit knowledge, although their specific roles remain unclear. We used functional magnetic resonance imaging to track the trial-by-trial acquisition of explicit knowledge in a concurrent trace and delay conditioning paradigm. We show that activity in bilateral middle frontal gyrus and parahippocampal gyrus correlates with the accuracy of explicit contingency awareness on each trial. In contrast, amygdala activation correlates with conditioned responses indexed by skin conductance responses (SCRs). These results demonstrate that brain regions known to be involved in other aspects of learning and memory also play a specific role, reflecting on each trial the acquisition and representation of contingency awareness.