Left Lateral Temporal Cortex Research Articles

Disrupted topological organization of the default mode network in mild cognitive impairment with subsyndromal depression: A graph theoretical analysis.

Subsyndromal depression (SSD) is common in mild cognitive impairment (MCI). However, the neural mechanisms underlying MCI with SSD (MCID) are unclear. The default mode network (DMN) is associated with cognitive processes and depressive symptoms. Therefore, we aimed to explore the topological organization of the DMN in patients with MCID. Forty-two MCID patients, 34 MCI patients without SSD (MCIND), and 36 matched healthy controls (HCs) were enrolled. The resting-state functional connectivity of the DMN of the participants was analyzed using a graph theoretical approach. Correlation analyses of network topological metrics, depressive symptoms, and cognitive function were conducted. Moreover, support vector machine (SVM) models were constructed based on topological metrics to distinguish MCID from MCIND. Finally, we used 10 repeats of 5-fold cross-validation for performance verification. We found that the global efficiency and nodal efficiency of the left anterior medial prefrontal cortex (aMPFC) of the MCID group were significantly lower than the MCIND group. Moreover, small-worldness and global efficiency were negatively correlated with depressive symptoms in MCID, and the nodal efficiency of the left lateral temporal cortex and left aMPFC was positively correlated with cognitive function in MCID. In cross-validation, the SVM model had an accuracy of 0.83 [95% CI 0.79-0.87], a sensitivity of 0.88 [95% CI 0.86-0.90], a specificity of 0.75 [95% CI 0.72-0.78] and an area under the curve of 0.88 [95% CI 0.85-0.91]. The coexistence of MCI and SSD was associated with the greatest disrupted topological organization of the DMN. The network topological metrics could identify MCID and serve as biomarkers of different clinical phenotypic presentations of MCI.

Longitudinal development of category representations in ventral temporal cortex predicts word and face recognition

Regions in ventral temporal cortex that are involved in visual recognition of categories like words and faces undergo differential development during childhood. However, categories are also represented in distributed responses across high-level visual cortex. How distributed category representations develop and if this development relates to behavioral changes in recognition remains largely unknown. Here, we used functional magnetic resonance imaging to longitudinally measure the development of distributed responses across ventral temporal cortex to 10 categories in school-age children over several years. Our results reveal both strengthening and weakening of category representations with age, which was mainly driven by changes across category-selective voxels. Representations became particularly more distinct for words in the left hemisphere and for faces bilaterally. Critically, distinctiveness for words and faces across category-selective voxels in left and right lateral ventral temporal cortex, respectively, predicted individual children’s word and face recognition performance. These results suggest that the development of distributed representations in ventral temporal cortex has behavioral ramifications and advance our understanding of prolonged cortical development during childhood.

Abstract 127: Delayed Thrombectomy In A Patient With Recurrent MCA Strokes

Introduction Prior research has demonstrated mechanical thrombectomy (MT) to be a safe and effective treatment for stroke patients with a large vessel occlusion (LVO).1 However, MT has generally only been studied in a time window of less than 24 hours.2 To the best of the authors' knowledge, this case report is the first publication of a MT done months after the initial stroke event, in a patient with recurrent strokes and an evolving occlusion visualized in the middle cerebral artery (MCA). Methods The patient is a 55‐year‐old man with a past medical history of a left‐sided MCA stroke 2 months prior to current admission with multiple transient ischemic attacks (TIAs) on dual antiplatelet therapy (DAPT), with no persistent residual deficits. His first stroke was preceded by about 1 week of intermittent confusion and right arm tingling. MRI at the time showed an acute embolic infarct in left MCA territory, and a CTA showed a sub‐occlusive thrombus vs. atherosclerotic plaque in the superior branch of the left MCA. He was discharged on DAPT, but his prior symptoms began to recur on a weekly basis, lasting for a few minutes each time. The patient eventually presented on this admission to the ED with persistent dysarthria and word finding difficulties. Within 4 hours, his exam improved to an NIHSS of 0. An MRI without contrast showed a new acute punctate infarct in the posterior left lateral temporal cortex. CT angiogram showed a persistent left M2 occlusion which was confirmed by the diagnostic cerebral angiogram. CT Perfusion also showed a large penumbra in the same region. The decision was made to perform MT, and complete recanalization was achieved. On 2‐month follow‐up, the patient continues to report no new symptoms since the time of MT. Results The patient’s positive outcome thus far at 60 day follow up indicates that MT can prove safe and efficacious even in significantly delayed time windows. This also shows that the decision to proceed with MT ought not to depend on time interval and degree of collaterals alone, but also on the pattern of symptoms the patient is exhibiting. The recurrent TIAs and strokes our patient was having indicates that, although collaterals had formed in response to his sub‐occlusive thrombus in the MCA, they were still unable to provide full compensation for this lost blood flow, leading to the patient’s intermittent symptoms. Conclusion This report demonstrates that MT can be safely and effectively utilized even in significantly delayed time windows in patients with recurrent TIAs or strokes.

Semantic-specific and domain-general mechanisms for integration and update of contextual information.

Recent research has highlighted the importance of domain-general processes and brain regions for language and semantic cognition. Yet, this has been mainly observed in executively demanding tasks, leaving open the question of the contribution of domain-general processes to natural language and semantic cognition. Using fMRI, we investigated whether neural processes reflecting context integration and context update-two key aspects of naturalistic language and semantic processing-are domain-specific versus domain-general. Thus, we compared neural responses during the integration of contextual information across semantic and non-semantic tasks. Whole-brain results revealed both shared (left posterior-dorsal inferior frontal gyrus, left posterior inferior temporal gyrus, and left dorsal angular gyrus/intraparietal sulcus) and distinct (left anterior-ventral inferior frontal gyrus, left anterior ventral angular gyrus, left posterior middle temporal gyrus for semantic control only) regions involved in context integration and update. Furthermore, data-driven functional connectivity analysis clustered domain-specific versus domain-general brain regions into distinct but interacting functional neural networks. These results provide a first characterisation of the neural processes required for context-dependent integration during language processing along the domain-specificity dimension, and at the same time, they bring new insights into the role of left posterior lateral temporal cortex and left angular gyrus for semantic cognition.

Gravity matters for the neural representations of action semantics.

The dynamic relationship between the neural representation of action word semantics and specific sensorimotor experience remains controversial. Here, we temporarily altered human subjects' sensorimotor experience in a 15-day head-down tilt bed rest setting, a ground-based analog of microgravity that disproportionally affects sensorimotor experiences of the lower limbs, and examined whether such effector-dependent activity deprivation specifically affected the neural processes of comprehending verbs of lower-limb actions (e.g. to kick) relative to upper-limb ones (e.g. to pinch). Using functional magnetic resonance imaging, we compared the multivoxel neural patterns for such action words prior to and after bed rest. We found an effector-specific (lower vs. upper limb) experience modulation in subcortical sensorimotor-related and anterior temporal regions. The neural action semantic representations in other effector-specific verb semantic regions (e.g. left lateral posterior temporal cortex) and motor execution regions were robust against such experience alterations. These effector-specific, sensorimotor-experience-sensitive and experience-independent patterns of verb neural representation highlight the multidimensional and dynamic nature of semantic neural representation, and the broad influence of microgravity (hence gravity) environment on cognition.

Cortical Thickness Abnormalities at Different Stages of the Illness Course in Schizophrenia

Questions of whether and how cortical thickness (CTh) alterations differ over the course of schizophrenia (SCZ) have yet to be resolved. To characterize CTh alterations across illness stages in SCZ. PubMed, Embase, Web of Science, and Science Direct were screened for CTh studies published before June 15, 2021. Original studies comparing whole-brain CTh alterations from healthy controls in individuals at clinical high-risk (CHR), first episode of psychosis (FEP), and long-term illness stages of SCZ were included. This preregistered systematic review and meta-analysis followed PRISMA reporting guidelines. Separate and pooled meta-analyses were performed using seed-based d mapping. Meta-regression analyses were conducted. Cortical thickness differences from healthy control individuals across illness stages. Ten studies comprising 859 individuals with CHR (mean [SD] age, 21.02 [2.66] years; male, 573 [66.7%]), 12 studies including 671 individuals with FEP (mean [SD] age, 22.87 [3.99] years; male, 439 [65.4%]), and 10 studies comprising 579 individuals with long-term SCZ (mean [SD] age, 41.58 [6.95] years; male, 396 [68.4%]) were included. Compared with healthy control individuals, individuals with CHR showed cortical thinning in bilateral medial prefrontal cortex (z = -1.01; P < .001). Individuals with FEP showed cortical thinning in right lateral superior temporal cortex (z = -1.34; P < .001), right anterior cingulate cortex (z = -1.44; P < .001), and right insula (z = -1.14; P = .002). Individuals with long-term SCZ demonstrated CTh reductions in right insula (z = -3.25; P < .001), right inferior frontal cortex (z = -2.19; P < .001), and left (z = -2.37; P < .001) and right (z = -1.94; P = .002) temporal pole. There were no significant CTh differences between CHR and FEP. Individuals with long-term SCZ showed greater cortical thinning in right insula (z = -2.58; P < .001), right inferior frontal cortex (z = -2.32; P < .001), left lateral temporal cortex (z = -1.91; P = .002), and right temporal pole (z = -1.82; P = .002) than individuals with FEP. Combining all studies on SCZ, accelerated age-related CTh reductions were found in bilateral lateral middle temporal cortex and right pars orbitalis in inferior frontal cortex. The absence of significant differences between FEP and CHR noted in this systematic review and meta-analysis suggests that the onset of psychosis was not associated with robust CTh reduction. The greater cortical thinning in long-term SCZ compared with FEP with accelerated age-related reduction in CTh suggests progressive neuroanatomic alterations following illness onset. Caution in interpretation is needed because heterogeneity in samples and antipsychotic treatment may confound these results.

Stereo-electroencephalography evidence of an eccentrically located seizure-onset zone around a polymorphous low-grade neuroepithelial tumor of the young: illustrative case.

BACKGROUNDPolymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a newly identified low-grade brain tumor with frequent epileptic presentation. Despite the facilitated use of invasive electroencephalography owing to the growing availability of stereo-electroencephalography (SEEG), intracranial features of tumor-related seizures are still scarcely described. This report provides the first description of SEEG-recorded seizures in PLNTY to provide an insight into its surgical strategy.OBSERVATIONSSpontaneous clinical seizures were recorded with SEEG in a young adult patient with drug-resistant epilepsy associated with a PLNTY in the left lateral temporal cortex. The seizure onset was characterized by low-voltage fast activity (LVFA) and showed eccentric localization with respect to the tumor: LVFA was localized in the anterior portion of the tumor and spread toward the adjacent polar cortex. The language risks associated with the resection of the posterior temporal cortex could thus be minimized.LESSONSPLNTY can show a focal and eccentric seizure-onset zone around the tumor. The present findings serve to improve the functional and seizure outcomes using the staged invasive approach in PLNTY.

Brain Surface Area Alterations Correlate With Gait Impairments in Parkinson's Disease.

Parkinson’s disease (PD) is a common neurodegenerative disease with progressive gait, cognition, and overall functional decline. Surface area changes are frequently seen with aging. In neurodegenerative diseases, the changes can be evident with disease progression. The current study aimed to study the regional microstructural alterations using surface-based morphometry to correlate with gait measures of the pace and rhythm domains in PD patients. We hypothesize that specific regional surface changes can be associated with PD gait impairments. Surface analysis might provide a useful tool for assessing PD for functional status and specific motor domains, such as gait in PD, and potentially could serve as an imaging marker in conjunction with other imaging markers. Twenty-seven PD patients and 37 healthy controls were included. The clinical assessment included Mini-Mental State Exanimation, PD motor assessment, clinical gait testing, and objective/quantitative gait assessment. For patients with PD, all motor and gait testing were performed during both OFF and ON medication states. Three Tesla MRI and high-resolution 3D structural images were acquired with an MP-RAGE pulse sequence. Structural image data preprocessing was performed using the DPABISurf toolbox. Clinical characteristics between PD and control group were compared, and correlation between the surface area and behavioral data were analyzed. At the left lateral temporal cortex (LTC) and right inferior parietal cortex (IPC), PD patients have significantly larger surface areas when compared to controls (P < 0.05) using surface-based morphometry. The surface area changes of the left LTC and right IPC were associated with the worse performance of gait assessed by Berg Balance Scale and Timed Up and Go during OFF (P < 0.01). The left LTC area changes significantly correlated with the number of steps, velocity, and the stride length of the pace domain in the ON state. Our findings suggest that PD is associated with a characteristic regional pattern of larger surface area in the left LTC and right IPC. These regional changes were associated with the pace domain of the gait in the ON state. Overall, surface-based analyses might provide a useful tool for assessing PD for functional status and specific motor domains, such as gait in PD, and potentially could serve as an imaging marker.

Poorer Theory of Mind in Amnestic Mild Cognitive Impairment Is Associated with Decreased Functional Connectivity in the Default Mode Network.

Older adults living with amnestic mild cognitive impairment (aMCI) not only demonstrate impairments in Theory of Mind (ToM), relative to adults with non-amnestic MCI (naMCI), but are also at a higher risk of developing dementia. Our primary objective was to ascertain whether default mode network (DMN) functional connectivity was differentially associated with ToM abilities between MCI subgroups. Using functional magnetic resonance imaging, we investigated alterations in resting-state functional connectivity within the brain's DMN in a sample of 43 older adults with aMCI (n = 19) and naMCI (n = 24), previously reported to demonstrate poorer ToM abilities. Compared to naMCI, the aMCI subgroup revealed a significant association between poorer ToM performance and reduced functional connectivity between the bilateral temporal pole (TempP) and the left lateral temporal cortex (LTC) (LTC_L-TempP_L: b = -0.06, t(33) = -3.53, p = 0.02; LTC_L-TempP_R: b = -0.07,t(33) = -3.20, p = 0.03); between the right TempP and the dorsal medial prefrontal cortex (dMPFC) (b = -0.04, t(33) = -3.02, p = 0.03) and between the left and right TempP (b = -0.05, t(33) = -3.26, p = 0.03). In the naMCI subgroup, the opposite relationship was present between the bilateral TempP and the left LTC (Combined correlation: r = -0.47, p = 0.02), however, not between the right TempP and the dMPFC (r = -0.14, p = 0.51) or the left and right TempP (r = -0.31, p = 0.14). Our findings suggest that alterations in functional connectivity within the DMN involving temporal and frontal lobe regions are associated with ToM deficits in aMCI.

Theory of Mind in mild cognitive impairment: Relationship with the default mode network (DMN)

AbstractBackgroundIt has been well established that older adults presenting with amnestic Mild Cognitive Impairment (aMCI) are not only at a higher risk of developing dementia compared to individuals with non‐amnestic Mild Cognitive Impairment (naMCI) and older adult controls, but also demonstrate impairments in Theory of Mind (ToM) ability, which has been associated with smaller limbic structure volumes. In the present study, we sought to examine any alterations in resting‐state functional connectivity within the brain's default mode network (DMN) in a sample of adults with MCI previously reported to demonstrate poorer ToM abilities.Methods17 adults with aMCI, 26 adults with naMCI and 16 older adult controls completed the Reading the Mind in the Eyes Test, followed by resting‐state functional magnetic resonance imaging.ResultsAfter controlling for age and correcting for multiple comparisons, adults with aMCI demonstrating poorer ToM abilities revealed significantly decreased functional connectivity between the left lateral temporal cortex (LTC) and the right temporal pole (b = .07, t(23) = 3.73, p = .02), as well as between the left LTC and both the left (b = .06, t(23) = 3.32, p = .03) and right (b = .04, t(23) = 2.91, p = .049) temporoparietal junctions ,relative to adults with naMCI.ConclusionsOur findings suggest that deficits in connectivity across a more widely distributed network of brain regions such as the DMN may be contributing to ToM deficits in aMCI, beyond the previously identified changes in limbic structure volumes. Moreover, in a broader clinical sense, these results contribute to a growing body of evidence highlighting that it is important to include measures of social cognitive function in the routine clinical workup of individuals with suspected MCI.

Effects of Transcranial Direct Current Stimulation on Brain Networks Related to Creative Thinking.

Human creative thinking is unique and capable of generating novel and valuable ideas. Recent research has clarified the contribution of different brain networks (default mode network, DN; executive control network; salience network) to creative thinking. However, the effects of brain stimulation on brain networks during creative thinking and on creative performance have not been clarified. The present study was designed to examine the changes in functional connectivity (FC) and effective connectivity (EC) of the large-scale brain network, and the ensuing changes in creative performance, induced by transcranial direct current stimulation (tDCS). Fourteen healthy male students underwent two tDCS sessions, one with actual stimulation and one with sham stimulation, on two separate days. Participants underwent tDCS (anode over the left dorsolateral prefrontal cortex, DLPFC; cathode over the right inferior parietal lobule, IPL) for 20 min. Before and after the tDCS session, electroencephalography signals were acquired from 32 electrodes over the whole head during the creative thinking task. On FC analysis, the delta band FC between the posterior cingulate cortex and IPL significantly increased only after real stimulation. We also found that the change of flexibility score was significantly correlated with the change in: (i) delta band FC between mPFC and left lateral temporal cortex (LTC) and (ii) alpha band FC between IPL and right LTC. On EC analysis, decreased flow within the DN (from left LTC to right IPL) was observed. Our results reveal that tDCS could affect brain networks, particularly the DN, during creative thinking and modulate key FC in the generation of flexible creative ideas.

Patterns of cortical interactivity supporting speech production and lexical retrieval: A graph signal processing approach at the individual level

Abstract Although seemingly easy, speech production is a complex action involving several processes and brain regions and is often studied through the use of picture naming paradigms. Several brain regions have been identified as being involved in speech production and lexical retrieval, including several areas of the left lateral, ventral, and medial temporal cortex, and of the left lateral and medial prefrontal cortex (PFC). However, little is known about how these regions interact to allow us to produce and retrieve words so efficiently as we speak. In this study, we used graph signal processing, and in particular graph learning, to analyze intracranial electroencephalography data recorded directly at the cortical surface (i.e., electrocorticography, ECoG) in the blocked cyclic picture naming task (recently reported in Ries et al., 2017). In this task, pictures are named several times in semantically homogeneous (HOM) versus heterogeneous (HET) blocks. Lexical retrieval, and in particular our ability to select words from competing alternatives, is hampered in HOM vs. HET blocks with increasing repetitions of the pictures, an effect referred to as the semantic interference effect. The method we used can infer the connectivity between different brain regions from the recorded ECoG signals through an optimization process that considers the entire connectivity map instead of pair-wise methods such as more commonly used correlation measures. Our results show that distant left frontal and temporal brain regions as well as PFC regions are functionally connected in picture naming, and that connection strength is variable between pairs of brain regions and between participants. Semantic interference on naming latencies was not present in all participants and varied in terms of when naming latencies became slower in HOM versus HET blocks. Connection weights were generally sensitive to semantic context in the participants showing a semantic interference effect on behavior but in highly variable ways across participants and in different region pairs. In sum, our results are consistent with the hypotheses that left frontal and temporal regions are functionally connected during picture naming and that intra-frontal connections seem particularly important in this paradigm manipulating lexical retrieval difficulty. Further research is needed to explore the cortical interactions supporting lexical retrieval.

Neural Correlates of Facial Expression Recognition in Earthquake Witnesses.

Major adverse events, like an earthquake, trigger different kinds of emotional dysfunctions or psychiatric disorders in the exposed subjects. Recent literature has also shown that exposure to natural disasters can increase threat detection. In particular, we previously found a selective enhancement in the ability to read emotional facial expressions in L’Aquila earthquake witnesses, suggesting hypervigilance to stimuli signaling a threat. In light of previous neuroimaging data showing that trauma exposure is related to derangement of resting-state brain activity, in the present study we investigated the neurofunctional changes related to the recognition of emotional faces in L’Aquila earthquake witnesses. Specifically, we tested the relationships between accuracy in recognizing facial expressions and activity of the visual network (VN) and of the default-mode network (DMN). Resting-state functional connectivity (FC) with the main hub of the VN (primary, ventral, right-dorsal, and left-dorsal visual cortices) and DMN (posterior cingulate/precuneus, medial prefrontal, and right and left inferior parietal cortices) was investigated through a seed-based functional magnetic resonance imaging (fMRI) analysis in both earthquake-exposed subjects and non-exposed persons who did not live in an earthquake-affected area. The results showed that, in earthquake-exposed subjects, there is a significant reduction in the correlation between accuracy in recognizing facial expressions and the FC of the dorsal seed of the VN with the right inferior occipito-temporal cortex and the left lateral temporal cortex, and of two parietal seeds of DMN, i.e., lower parietal and medial prefrontal cortex, with the precuneus bilaterally. These findings suggest that a functional modification of brain systems involved in detecting and interpreting emotional faces may represent the neurophysiological basis of the specific “emotional expertise” observed in the earthquake witnesses.

Functional Network-Based Statistics Reveal Abnormal Resting-State Functional Connectivity in Minimal Hepatic Encephalopathy.

Purpose: Whole-brain functional network analysis is an emerging methodology for exploring the mechanisms underlying hepatic encephalopathy (HE). This study aimed to identify the brain subnetwork that is significantly altered within the functional connectome in minimal HE (MHE), the earliest stage of HE.Materials and Methods: The study enrolled 19 cirrhotic patients with MHE and 19 controls who underwent the resting-state functional magnetic resonance imaging and cognitive assessment based on the Psychometric Hepatic Encephalopathy Score (PHES). A whole-brain functional connectivity (FC) matrix was calculated for each subject. Then, network-based statistical analyses of the functional connectome were used to perform group comparisons, and correlation analyses were conducted to identify the relationships between FC alterations and cognitive performance.Results: MHE patients showed significant reduction of positive FC within a subnetwork that predominantly involved the regions of the default-mode network, such as the bilateral posterior cingulate gyrus, bilateral medial prefrontal cortex, bilateral hippocampus and parahippocampal gyrus, bilateral angular gyrus, and left lateral temporal cortex. Meanwhile, MHE patients showed significant reduction of negative FC between default-mode network regions (such as the bilateral posterior cingulate gyrus, medial prefrontal cortex, and angular gyrus) and the regions involved in the somatosensory network (i.e., bilateral precentral and postcentral gyri) and the language network (i.e., the bilateral Rolandic operculum). The correlations of FC within the default-mode subnetwork and PHES results were noted.Conclusion: Default-mode network dysfunction may be one of the core issues in the pathophysiology of MHE. Our findings support the notion that HE is a neurological disease related to intrinsic brain network disruption.

Distinct roles of temporal and frontoparietal cortex in representing actions across vision and language

Both temporal and frontoparietal brain areas are associated with the representation of knowledge about the world, in particular about actions. However, what these brain regions represent and precisely how they differ remains unknown. Here, we reveal distinct functional profiles of lateral temporal and frontoparietal cortex using fMRI-based MVPA. Frontoparietal areas encode representations of observed actions and corresponding written sentences in an overlapping way, but these representations do not generalize across stimulus type. By contrast, only left lateral posterior temporal cortex (LPTC) encodes action representations that generalize across observed action scenes and written descriptions. The representational organization of stimulus-general action information in LPTC can be predicted from models that describe basic agent-patient relations (object- and person-directedness) and the general semantic similarity between actions. Our results suggest that LPTC encodes general, conceptual aspects of actions whereas frontoparietal representations appear to be tied to specific stimulus types.

18F-flortaucipir uptake patterns in clinical subtypes of primary progressive aphasia

We analyzed 18F-flortaucipir uptake patterns and structural changes in patients with subtypes of primary progressive aphasia (PPA) using 18F-flortaucipir positron emission tomography and volumetric magnetic resonance imaging. We enrolled 34 consecutive patients with PPA (10 nonfluent/agrammatic PPA [nfvPPA], 18 semantic variant PPA [svPPA], and 6 logopenic variant PPA [lvPPA], as well as 20 healthy controls, and 20 patients with Alzheimer's disease. 18F-flortaucipir uptake was increased in the frontal cortex and underlying white matter, and subcortical nuclei in the 10 nfvPPA and 8 nfvPPA-amyloid-β (Aβ)− subgroup patients. In the svPPA patients (both the 13 svPPA-Aβ− and 5 svPPA-Aβ+), uptake generally increased in the widespread neocortex with left anterior temporal predominance. 18F-flortaucipir uptake patterns in the 6 lvPPA and the 5 lvPPA-Aβ+ subgroup patients were similar to those seen in the patients with Alzheimer's disease with mild predominance in the left lateral temporal cortex. Cortical thinning in each PPA subtype corresponded with increased 18F-flortaucipir uptake. 18F-flortaucipir uptake patterns and cortical atrophy were distinct and corresponded to areas related to the specific language functions that are impaired in each subtype of PPA.

Development of the P300 from childhood to adulthood: a multimodal EEG and MRI study.

Maturation of attentional processes is central to cognitive development. The electrophysiological P300 is associated with rapid allocation of attention, and bridges stimulus and response processing. P300 is among the most studied and robust electrophysiological components, but how different subcomponents of the P300 develop from childhood to adulthood and relate to structural properties of the cerebral cortex is not well understood. We investigated age-related differences in both early visual and P300 components, and how individual differences in these components are related to cortical structure in a cross-sectional sample of participants 8-19years (n = 86). Participants completed a three-stimulus visual oddball task while high-density EEG was recorded. Cortical surface area and thickness were estimated from T1-weighted MRI. Group-level blind source separation of the EEG data identified two P300-like components, a fronto-central P300 and a parietal P300, as well as a component reflecting N1 and P2. Differences in activity across age were found for the parietal P300, N1 and P2, with the parietal P300 showing stronger activity for older participants, while N1 and P2 were stronger for younger participants. Stronger P300 components were positively associated with task performance, independently of age, while negative associations were found for P2 strength. Parietal P300 strength was age-independently associated with larger surface area in a region in left lateral inferior temporal cortex. We suggest that the age differences in component strength reflect development of attentional mechanisms, with increased brain responses to task-relevant stimuli representing an increasing ability to focus on relevant information and to respond accurately and efficiently.

Lack of improvement in multiplication is associated with reverting from verbal retrieval to numerical operations

Models of the neural basis of arithmetic argue that left inferior frontal cortex is involved in cognitive control of verbal representations of math facts in left lateral temporal cortex, whereas bilateral intra-parietal cortex is involved in numerical calculation. Lower levels of math competence for multiplications is associated with greater effortful retrieval because of less robust verbal representations and the engagement of numerical operations as a back-up strategy. Previous studies on multiplication have focused on brain activation in isolated nodes of the network, so we do not know how functional connectivity between these nodes is related to competence. Moreover, previous studies have not employed longitudinal designs, so we do not know how changes in multiplication performance over time is related to changes in its neural basis. The objective of this study was to investigate how changes in multiplication task performance is associated with changes in functional connectivity of temporal cortex with frontal and parietal cortices. Longitudinal data was collected from 45 children, with an average 2.2-year interval between the two sessions, when they were about 11 years old at time 1 (T1) and 13 years old at time 2 (T2). A Psychophysiological Interaction (PPI) analysis was carried out by defining the seed in the temporal cortex (i.e. posterior superior and middle temporal gyri) and examining changes in connectivity with frontal cortex (i.e. left inferior frontal gyrus) as well as parietal cortex (i.e. left and right inferior and superior parietal lobules). We found that children who did not improve in a multiplication task showed greater levels of functional connectivity of left temporal cortex with left inferior frontal gyrus (IFG) and left intraparietal sulcus (IPS) at T2, as compared to their peers who improved. The cluster showing greater levels of connectivity in the left IFG at T2 for the Non-improvers overlapped a cluster independently identified by a verbal localizer task and the cluster showing greater levels of connectivity in the left IPS Non-improvers overlapped a cluster independently identified by a numerosity localizer task. These results suggest that lack of improvement in multiplications are associated with greater cognitive control of verbal representations and greater engagement of numerical operations.

Changes in regional cerebral blood flow associated with a 45 day course of the ketogenic agent, caprylidene, in patients with mild to moderate Alzheimer's disease: Results of a randomized, double-blinded, pilot study.

Caprylidene is a ketogen that, when metabolized, produces the ketones beta-hydroxybutyrate and acetoacetate, which can cross the blood brain barrier. It has been hypothesized that ketone bodies can be used as an alternate energy source by neurons with impaired glucose utilization. Caprylidene has been shown to improve cognition in patients with mild-to-moderate Alzheimer's disease (AD) who lacked an AD-predisposing allele (ɛ4) of the gene for apolipoprotein E. In this pilot study, we examined the effects of caprylidene on regional cerebral blood flow (rCBF) in patients with mild to moderate AD. Sixteen subjects with mild-to-moderate AD, based on NINCDS-ADRDA criteria, were enrolled in a double-blinded, placebo-controlled, randomized clinical trial. Fourteen subjects received treatment with caprylidene, and 2 subjects were given placebo. Subjects received 4 15O-water PET scans over the course of the study to assess rCBF: once before receiving a standard caprylidene or placebo dose and 90 min after the dose, on the first day and after 45 days of daily caprylidene or placebo consumption. The scans were examined by standardized volumes of interest (sVOI) and voxel-based statistical parametric mapping (spm) methods of analysis. Subjects lacking an ɛ4 allele had significantly elevated rCBF in the left superior lateral temporal cortex by sVOI analysis after adopting a caprylidene diet for 45 days (p = 0.04), which was further corroborated by spm. The anterior cerebellum, left inferior temporal cortex, and hypothalamus were also found by spm to be regions of long-term increase in rCBF in these subjects. In contrast, patients who possessed the ɛ4 allele did not display these changes in rCBF. Daily ingestion of caprylidene over 45 days was associated with increased blood flow in specific brain regions in patients lacking an apolipoprotein ɛ4 allele.

The structure of the mental lexicon: What primary progressive aphasias reveal

Like recursive syntax, a structured mental lexicon is specific to the human species but its internal organization remains unclear. It is thought to contain information about the semantic, syntactic (e.g., gender) and formal (orthographic/phonological) features of a word. Previous studies suggested that these three components might be separated at the behavioral level and that they might be implemented by temporal cortices. However, the available investigations are based on case reports or small-cohort studies with patients demonstrating post-stroke aphasia, and they did not contrast the three lexical components in a directly comparable way. Similarly, functional imaging studies with healthy adults did not compare the lexical components but explored them separately using various tasks. Here we assessed the three components with comparable tasks in a relatively large cohort of 20 patients with primary progressive aphasia (PPA), namely logopenic and semantic PPA, which have been shown to affect the temporal cortex. The same tasks were also applied to 23 healthy adults. We thereby primarily aimed at showing multiple intra-lexical dissociations at the behavioral level to demonstrate the existence of a threefold segregation within the mental lexicon. We also sought to confirm the temporal-cortical involvement in the implementation of the lexical components and to characterize differential lexical breakdown in PPA. Lexical components were explored with three implicit processing tasks (semantic, syntactic-gender, word-form priming) and with three explicit matching tasks (semantic, syntactic-gender, word-form). Our results indicate that the three components are functionally segregated as evidenced by multiple dissociations at the group level, and the individual level, thus substantiating the existence of a threefold structure of the mental lexicon. Cortical thickness analyses showed damage to the left lateral temporal cortex in the entire PPA cohort suggesting that lexical components are anatomically segregated within this cortical region. Our results also refine previous proposals about lexical deficits in PPA by demonstrating differential damage to all three components of the lexicon in semantic and logopenic PPA, which might have an impact on PPA diagnosis and language rehabilitation strategies.