Context-dependent interactions of left posterior inferior frontal gyrus in a local visual search task unrelated to language

rTMS Induces Brain Functional and Structural Alternations in Schizophrenia Patient With Auditory Verbal Hallucination

BACKGROUND

Low-frequency transcranial magnetic stimulation (rTMS) over the left temporoparietal cortex reduces the auditory verbal hallucination (AVH) in schizophrenia. However, the underlying neural basis of the rTMS treatment effect for schizophrenia remains not well understood. This study investigates the rTMS induced brain functional and structural alternations and their associations with clinical as well as neurocognitive profiles in schizophrenia patients with AVH.

METHODS

Thirty schizophrenia patients with AVH and thirty-three matched healthy controls were enrolled. The patients were administered by 15 days of 1 Hz rTMS delivering to the left temporoparietal junction (TPJ) area. Clinical symptoms and neurocognitive measurements were assessed at pre- and post-rTMS treatment. The functional (amplitude of low-frequency fluctuation, ALFF) and structural (gray matter volume, GMV) alternations were compared, and they were then used to related to the clinical and neurocognitive measurements after rTMS treatment.

RESULTS

The results showed that the positive symptoms, including AVH, were relieved, and certain neurocognitive measurements, including visual learning (VisLearn) and verbal learning (VerbLearn), were improved after the rTMS treatment in the patient group. Furthermore, the rTMS treatment induced brain functional and structural alternations in patients, such as enhanced ALFF in the left superior frontal gyrus and larger GMV in the right inferior temporal cortex. The baseline ALFF and GMV values in certain brain areas (e.g., the inferior parietal lobule and superior temporal gyrus) could be associated with the clinical symptoms (e.g., positive symptoms) and neurocognitive performances (e.g., VerbLearn and VisLearn) after rTMS treatment in patients.

CONCLUSION

The low-frequency rTMS over the left TPJ area is an efficacious treatment for schizophrenia patients with AVH and could selectively modulate the neural basis underlying psychiatric symptoms and neurocognitive domains in schizophrenia.

Altered Spontaneous Brain Activity Patterns in Patients After Lasik Surgery Using Amplitude of Low-Frequency Fluctuation: A Resting-State Functional MRI Study

OBJECTIVE

Previous studies demonstrated that myopia could result in alterations of brain activity in specific areas. However, whether the visual function could improve by Lasik surgery, with the brain activity alterations also change, is still unknown. Here, we intended to use the amplitude of low-frequency fluctuation (ALFF) technique to investigate the intrinsic brain activity changes in pre-Lasik (PRL) and post-Lasik (POL) patients.

METHODS

A total of 15 patients with myopia (nine male and six female) were recruited in our study, who were matched according to age, weight, and height. These patients comprised both the PRL and POL groups, which is self-controlled. The patients all underwent resting-state functional magnetic resonance imaging (MRI), and the spontaneous brain activity changes were recorded by the ALFF technique. The data were recorded and arranged in the receiver operating characteristic (ROC) curve, which presented how intrinsic activities altered in different brain regions. Moreover, by Graphpad prism 8, we can analyze the linear correlation between HADS (Hospital Anxiety and Depression Scale) and ALFF values as well.

RESULTS

Differences in ALFF values existed in brain regions between the same patient before and after the Lasik operation. The regions with increased ALFF values after Lasik surgery were the left parahippocampal gyrus, cerebellar vermis, and left posterior cingulate cortex. The regions with decreased ALFF values after Lasik surgery were the left supramarginal gyrus and right trigonometric inferior frontal gyrus.

CONCLUSION

We demonstrated significant fluctuations of ALFF values in specific brain areas between the same patients before and after the Lasik surgery. The altered ALFF values reflected the hyperactivity or hypoactivity of the specific brain areas, which may help predict the recovery level of patients' vision after Lasik surgery. Furthermore, based on the experimental results that presented significant activity alterations in specific brian regions, patients could be speculated equipped with a better visual function.

Neural Correlates of Social Perception in Children with Autism: Local versus Global Preferences

The Weak Central Coherence account of autism spectrum disorders posits that individuals with ASD utilize a detail-oriented information processing bias. While this local bias is helpful in visual search tasks, ASD individuals falter in social cognition tasks where coherence is advantageous. The present study examined the neural correlates of Weak Central Coherence in ASD during visual and social processing. Fifteen ASD and sixteen typically developing children/adolescents completed a social/visual information processing task in an fMRI scanner. The stimuli consisted of human characters, composed of geometrical shapes, displaying different emotions. In the locally oriented Shape condition, participants indicated whether a given shape was present in a figure. In the Emotion condition, participants identified the emotion conveyed by the character in the figure at the global level. Whole-brain within- and between-group activation and seed-to-voxel functional connectivity analyses were conducted in SPM12 and the CONN toolbox. The ASD group was significantly faster in shape identification, but less accurate in emotion identification. The TD group showed significantly increased areas of activity over the ASD group in the Shape task in regions associated with executive control, such as the medial prefrontal cortex and middle frontal gyrus, suggesting increased interference from the global/social information. During the Emotion condition, the ASD group showed decreased connectivity between frontal and posterior regions and between body perception and motor networks, suggesting a possible difference in mirroring. The findings suggest that social cognitive factors, not visual processing biases, underlie the observed behavioral differences.

Differences in cytoarchitecture of Broca's region between human, ape and macaque brains

Areas 44 and 45 have been identified in non-human primates as homologs of the human Broca region. Distribution of large and smaller pyramids and the ventro-lateral localization in the posterior frontal lobe enable their identification in non-human primates. Since only humans hold the ability of language, it has been hypothesized that differences in microstructure may, together with other anatomical factors, e.g., white matter tract connectivity, volumes of cortical areas and their molecular differentiation, be responsible for the lack (non-human primates) or ability (humans) of language. We sought to identify microstructural differences, by quantitatively studying the cytoarchitecture of areas 44 and 45 using layer-specific grey level indices (volume proportion of neuropil and cell bodies) in serially sectioned and cell body stained human, bonobo, chimpanzee, gorilla, orangutan and Macaca fascicularis brains. The main results are the interspecies differences in neuropil volume relative to cell bodies in all layers of both areas which allows a grouping of the different species into three major groups: Homo sapiens has the largest, great apes a markedly lower, and macaque the lowest neuropil volume. This indicates considerably more space for local and interregional connectivity in human brains, which matches recent studies of fiber tracts and spacing of cortical minicolumns because increasing connectivity also requires more space for axons and dendrites in the neuropil. The evolutionary enlargement of neuropil is, therefore, a major structural difference between humans and non-human primates which may correspond to the underlying functional differences.

Altered spontaneous brain activity pattern in patients with high myopia using amplitude of low-frequency fluctuation: a resting-state fMRI study

OBJECTIVE

Many previous reports have demonstrated significant neural anatomy changes in the brain of high myopic (HM) patients, whereas the spontaneous brain activity changes in the HM patients at rest are not well studied. Our objective was to use amplitude of low-frequency fluctuation (ALFF) method to investigate the changes in spontaneous brain activity in HM patients and their relationships with clinical features.

METHODS

A total of 38 patients with HM (17 males and 21 females) and 38 healthy controls (HCs) (17 males and 21 females) closely matched in age, sex, and education underwent resting-state functional magnetic resonance imaging scans. The ALFF method was used to assess local features of spontaneous brain activity. The relationship between the mean ALFF signal values in many brain regions and the clinical features in HM patients was calculated by correlation analysis.

RESULTS

Compared with HCs, the HM patients had significantly lower ALFF in the right inferior and middle temporal gyrus, left middle temporal gyrus, left inferior frontal gyrus/putamen, right inferior frontal gyrus/putamen/insula, right middle frontal gyrus, and right inferior parietal lobule and higher ALFF values in the bilateral midcingulate cortex, left postcentral gyrus, and left precuneus/inferior parietal lobule. However, no relationship was found between the mean ALFF signal values of the different areas and the clinical manifestations in HM.

CONCLUSION

The HM patients were affected with brain dysfunction in many regions, which may indicate the presence of neurobiological changes involving deficits in language understanding and attentional control in HM patients.

Failure to deactivate the default mode network indicates a possible endophenotype of autism

Background

Reduced activity during cognitively demanding tasks has been reported in the default mode network in typically developing controls and individuals with autism. However, no study has investigated the default mode network (DMN) in first-degree relatives of those with autism (such as siblings) and it is not known whether atypical activation of the DMN is specific to autism or whether it is also present in unaffected relatives. Here we use functional magnetic resonance imaging to investigate the pattern of task-related deactivation during completion of a visual search task, the Embedded Figures Task, in teenagers with autism, their unaffected siblings and typically developing controls.

Findings

We identified striking reductions in deactivation during the Embedded Figures Task in unaffected siblings compared to controls in brain regions corresponding to the default mode network. Adolescents with autism and their unaffected siblings similarly failed to deactivate regions, including posterior cingulate and bilateral inferior parietal cortex.

Conclusions

This suggests that a failure to deactivate these regions is a functional endophenotype of autism, related to familial risk for the condition shared between individuals with autism and their siblings.

Atypical activation during the Embedded Figures Task as a functional magnetic resonance imaging endophenotype of autism

Atypical activation during the Embedded Figures Task has been demonstrated in autism, but has not been investigated in siblings or related to measures of clinical severity. We identified atypical activation during the Embedded Figures Task in participants with autism and unaffected siblings compared with control subjects in a number of temporal and frontal brain regions. Autism and sibling groups, however, did not differ in terms of activation during this task. This suggests that the pattern of atypical activation identified may represent a functional endophenotype of autism, related to familial risk for the condition shared between individuals with autism and their siblings. We also found that reduced activation in autism relative to control subjects in regions including associative visual and face processing areas was strongly correlated with the clinical severity of impairments in reciprocal social interaction. Behavioural performance was intact in autism and sibling groups. Results are discussed in terms of atypical information processing styles or of increased activation in temporal and frontal regions in autism and the broader phenotype. By separating the aspects of atypical activation as markers of familial risk for the condition from those that are autism-specific, our findings offer new insight into the factors that might cause the expression of autism in families, affecting some children but not others.

Functional evaluation of hidden figures object analysis in children with autistic disorder

Functional magnetic resonance imaging (fMRI) during performance of a hidden figures task (HFT) was used to compare differences in brain function in children diagnosed with autism disorder (AD) compared to children with attention-deficit/hyperactivity disorder (ADHD) and typical controls (TC). Overall greater functional MRI activity was observed in the two control groups compared to children with AD. Laterality differences were also evident, with AD subjects preferentially showing activity in the right medial temporal region while controls tended to activate the left medial temporal cortex. Reduced fMRI activity was observed in the parietal, ventral-temporal and hippocampal regions in the AD group, suggesting differences in the way that children with AD process the HFT.

Effective connectivity of the left BA 44, BA 45, and inferior temporal gyrus during lexical and phonological decisions identified with DCM

Distinct regions in the left inferior frontal gyrus (IFG) preferentially support the processing of different word-types (e.g., real words, pseudowords) and tasks (e.g., lexical decisions, phonological decisions) in visual word recognition. However, the functional connectivity underlying the task-related specialisation of regions in the left IFG is not yet well understood. In this study we investigated the neural mechanisms driving the interaction of WORD-TYPE (real word vs. pseudoword) and TASK (lexical vs. phonological decision) in Brodmann's area (BA) 45 in the left IFG using dynamic causal modelling (DCM). Four different models were compared, all of which included left BA44, left BA45, and left inferior temporal gyrus (ITG). In each model, the visual presentation of words and pseudowords is assumed to directly evoke activity in the ITG and is then thought to be subsequently propagated to BA45 and to BA44 via direct intrinsic connections. The models differed with regard to which connections were modulated by the different tasks. Both tasks were assumed to either modulate the ITG_BA45 connection (Model #1), or the BA44_BA45 connection (Model #2), or both connections in parallel (Model #3). In Model #4 lexical decisions modulated the ITG_BA45 connection, whereas phonological decisions modulated the BA44_BA45 connection. Bayesian model selection revealed a superiority of Model #1. In this model, the strength of the ITG_BA45 connection was enhanced during lexical decisions. This model is in line with the hypothesis that left BA 45 supports explicit lexical decisions during visual word recognition based on lexical access in the ITG.

Enhancing language performance with non-invasive brain stimulation--a transcranial direct current stimulation study in healthy humans

In humans, transcranial direct current stimulation (tDCS) can be used to induce, depending on polarity, increases or decreases of cortical excitability by polarization of the underlying brain tissue. Cognitive enhancement as a result of tDCS has been reported. The purpose of this study was to test whether weak tDCS (current density, 57 microA/cm(2)) can be used to modify language processing. Fifteen healthy subjects performed a visual picture naming task before, during and after tDCS applied over the posterior perisylvian region (PPR), i.e. an area which includes Wernicke's area [BA 22]. Four different sessions were carried out: (1) anodal and (2) cathodal stimulation of left PPR and, for control, (3) anodal stimulation of the homologous region of the right hemisphere and (4) sham stimulation. We found that subjects responded significantly faster following anodal tDCS to the left PPR (p<0.01). No decreases in performance were detected. Our finding of a transient improvement in a language task following the application of tDCS together with previous studies which investigated the modulation of picture naming latency by transcranial magnetic stimulation (TMS) and repetitive TMS (rTMS) suggest that tDCS applied to the left PPR (including Wernicke's area [BA 22]) can be used to enhance language processing in healthy subjects. Whether this safe, low cost, and easy to use brain stimulation technique can be used to ameliorate deficits of picture naming in aphasic patients needs further investigations.

Neurophysiological correlates of relatively enhanced local visual search in autistic adolescents

Previous studies found normal or even superior performance of autistic patients on visuospatial tasks requiring local search, like the Embedded Figures Task (EFT). A well-known interpretation of this is "weak central coherence", i.e. autistic patients may show a reduced general ability to process information in its context and may therefore have a tendency to favour local over global aspects of information processing. An alternative view is that the local processing advantage in the EFT may result from a relative amplification of early perceptual processes which boosts processing of local stimulus properties but does not affect processing of global context. This study used functional magnetic resonance imaging (fMRI) in 12 autistic adolescents (9 Asperger and 3 high-functioning autistic patients) and 12 matched controls to help distinguish, on neurophysiological grounds, between these two accounts of EFT performance in autistic patients. Behaviourally, we found autistic individuals to be unimpaired during the EFT while they were significantly worse at performing a closely matched control task with minimal local search requirements. The fMRI results showed that activations specific for the local search aspects of the EFT were left-lateralised in parietal and premotor areas for the control group (as previously demonstrated for adults), whereas for the patients these activations were found in right primary visual cortex and bilateral extrastriate areas. These results suggest that enhanced local processing in early visual areas, as opposed to impaired processing of global context, is characteristic for performance of the EFT by autistic patients.

On the role of general system theory for functional neuroimaging

One of the most important goals of neuroscience is to establish precise structure-function relationships in the brain. Since the 19th century, a major scientific endeavour has been to associate structurally distinct cortical regions with specific cognitive functions. This was traditionally accomplished by correlating microstructurally defined areas with lesion sites found in patients with specific neuropsychological symptoms. Modern neuroimaging techniques with high spatial resolution have promised an alternative approach, enabling non-invasive measurements of regionally specific changes of brain activity that are correlated with certain components of a cognitive process. Reviewing classic approaches towards brain structure-function relationships that are based on correlational approaches, this article argues that these approaches are not sufficient to provide an understanding of the operational principles of a dynamic system such as the brain but must be complemented by models based on general system theory. These models reflect the connectional structure of the system under investigation and emphasize context-dependent couplings between the system elements in terms of effective connectivity. The usefulness of system models whose parameters are fitted to measured functional imaging data for testing hypotheses about structure-function relationships in the brain and their potential for clinical applications is demonstrated by several empirical examples.