Dorsolateral Frontal Cortex Research Articles

Epileptic Discharges Affect the Default Mode Network – fMRI and Intracerebral EEG Evidence

Functional neuroimaging studies of epilepsy patients often show, at the time of epileptic activity, deactivation in default mode network (DMN) regions, which is hypothesized to reflect altered consciousness. We aimed to study the metabolic and electrophysiological correlates of these changes in the DMN regions. We studied six epilepsy patients that underwent scalp EEG-fMRI and later stereotaxic intracerebral EEG (SEEG) sampling regions of DMN (posterior cingulate cortex, Pre-cuneus, inferior parietal lobule, medial prefrontal cortex and dorsolateral frontal cortex) as well as non-DMN regions. SEEG recordings were subject to frequency analyses comparing sections with interictal epileptic discharges (IED) to IED-free baselines in the IED-generating region, DMN and non-DMN regions. EEG-fMRI and SEEG were obtained at rest. During IEDs, EEG-fMRI demonstrated deactivation in various DMN nodes in 5 of 6 patients, most frequently the pre-cuneus and inferior parietal lobule, and less frequently the other DMN nodes. SEEG analyses demonstrated decrease in gamma power (50–150 Hz), and increase in the power of lower frequencies (<30 Hz) at times of IEDs, in at least one DMN node in all patients. These changes were not apparent in the non-DMN regions. We demonstrate that, at the time of IEDs, DMN regions decrease their metabolic demand and undergo an EEG change consisting of decreased gamma and increased lower frequencies. These findings, specific to DMN regions, confirm in a pathological condition a direct relationship between DMN BOLD activity and EEG activity. They indicate that epileptic activity affects the DMN, and therefore may momentarily reduce the consciousness level and cognitive reserve.

Is a neutral expression also a neutral stimulus? A study with functional magnetic resonance

Although neutral faces do not initially convey an explicit emotional message, it has been found that individuals tend to assign them an affective content. Moreover, previous research has shown that affective judgments are mediated by the task they have to perform. Using functional magnetic resonance imaging in 21 healthy participants, we focus this study on the cerebral activity patterns triggered by neutral and emotional faces in two different tasks (social or gender judgments). Results obtained, using conjunction analyses, indicated that viewing both emotional and neutral faces evokes activity in several similar brain areas indicating a common neural substrate. Moreover, neutral faces specifically elicit activation of cerebellum, frontal and temporal areas, while emotional faces involve the cuneus, anterior cingulated gyrus, medial orbitofrontal cortex, posterior superior temporal gyrus, precentral/postcentral gyrus and insula. The task selected was also found to influence brain activity, in that the social task recruited frontal areas while the gender task involved the posterior cingulated, inferior parietal lobule and middle temporal gyrus to a greater extent. Specifically, in the social task viewing neutral faces was associated with longer reaction times and increased activity of left dorsolateral frontal cortex compared with viewing facial expressions of emotions. In contrast, in the same task emotional expressions distinctively activated the left amygdale. The results are discussed taking into consideration the fact that, like other facial expressions, neutral expressions are usually assigned some emotional significance. However, neutral faces evoke a greater activation of circuits probably involved in more elaborate cognitive processing.

Dorsolateral frontal cortex and peripheral muscarinic receptors participation in the discriminative stimulus properties of scopolamine in rats

Organisms are capable of making decisions based on their ability to discriminate between different stimuli. This principle is fundamental for the adaptation of organisms to their environment, by emitting appropriate behaviors based on a previously acquired discriminative process. The present study analyzed the participation of the peripheral nervous system, the M1 muscarinic receptor subtype, as well as the contribution of the dorsolateral frontal cortex to discrimination process using scopolamine as discriminative stimulus.Male Wistar rats were trained to discriminate between scopolamine (1.0mg/kg) and saline injections (i.p.) using a two-lever operant procedure. Once discrimination was acquired, generalization curves for scopolamine, methylscopolamine, pirenzepine, dorsolateral frontal cortex lesion and control conditions were obtained.Results showed that rats were able to discriminate and generalize its responses to different doses of scopolamine but not for methylscopolamine or pirenzepine, thus the data suggest that discriminative properties of scopolamine are processed in CNS and that the M1 receptor does not participate in this process. Dorsolateral frontal cortex lesion did not produce any statistically significant difference in the generalization curve, which suggests that a system different from the dorsolateral prefrontal cortex may be responsible for the control of stimulus produced by scopolamine.

MRI volume of the medial frontal cortex predicts financial capacity in patients with mild Alzheimer's disease.

Persons with mild Alzheimer's disease (AD) have significant deficits in financial abilities. This study examined the relationship between brain structure volumes, cognition, and financial capacity in patients with mild AD. Sixteen mild AD patients and 16 older adult comparisons completed the Financial Capacity Instrument (FCI), a psychometric measure of financial abilities, and also underwent magnetic resonance imaging (MRI) to obtain volumes of the bilateral hippocampi, angular gyri, precunei, and medial and dorsolateral frontal cortices. Mild AD patients performed significantly below comparisons on the FCI and had significantly smaller hippocampi. Among mild AD patients, FCI performance was moderately correlated with frontal (medial and dorsolateral frontal cortex) and posterior (angular gyri and precunei) cortical volumes. Stepwise regression demonstrated that medial frontal cortex volume predicted FCI score. The relationship between medial frontal cortex volume and overall FCI score was partially mediated by two measures of simple attention (DRS Attention, DRS Construction). The findings suggest that medial frontal cortex atrophy and associated declines in simple attention play an increasingly important role in declining financial skills in patients with mild AD.

Causality within the Epileptic Network: An EEG-fMRI Study Validated by Intracranial EEG

Accurate localization of the Seizure Onset Zone (SOZ) is crucial in patients with drug-resistance focal epilepsy. EEG with fMRI recording (EEG-fMRI) has been proposed as a complementary non-invasive tool, which can give useful additional information in the pre-surgical work-up. However, fMRI maps related to interictal epileptiform activities (IED) often show multiple regions of signal change, or “networks,” rather than highly focal ones. Effective connectivity approaches like Dynamic Causal Modeling (DCM) applied to fMRI data potentially offers a framework to address which brain regions drives the generation of seizures and IED within an epileptic network. Here, we present a first attempt to validate DCM on EEG-fMRI data in one patient affected by frontal lobe epilepsy. Pre-surgical EEG-fMRI demonstrated two distinct clusters of blood oxygenation level dependent (BOLD) signal increases linked to IED, one located in the left frontal pole and the other in the ipsilateral dorso-lateral frontal cortex. DCM of the IED-related BOLD signal favored a model corresponding to the left dorso-lateral frontal cortex as driver of changes in the fronto-polar region. The validity of DCM was supported by: (a) the results of two different non-invasive analysis obtained on the same dataset: EEG source imaging (ESI), and “psycho-physiological interaction” analysis; (b) the failure of a first surgical intervention limited to the fronto-polar region; (c) the results of the intracranial EEG monitoring performed after the first surgical intervention confirming a SOZ located over the dorso-lateral frontal cortex. These results add evidence that EEG-fMRI together with advanced methods of BOLD signal analysis is a promising tool that can give relevant information within the epilepsy surgery diagnostic work-up.

The deficit of decision-making in male subjects with antisocial personality disorder

Objective To investigate the capabilities of decision-making in male subjects with Antisocial personality disorder(ASPD). Methods A total of 76 male ASPD subjects were compared with matched 60 healthy controls on the Iowa Gambling Task.At the same time, All of them were evaluated with Self- Rating Anxiety Scale (SAS), Self-Rating Depression Scale (SDS), Mini-Mental State Examination (MMSE), the MMPI Personality Disorder Scales (MMPI-Pd) and The Barratt Impulsiveness Scale (BIS-11). Results The ASPD group selected less advantageous cards (the number of cards selected from the advantageous decks minus the number of cards selected from disadvantageous decks) than healthy controls ((-4.13±18.27)time, (6.03±19.43) time respectively, t(134)=-3.132, P=0.002). A 2(group)×5(block) ANOVA (analysis of variance) on the cards of net advantageous from the gambling task revealed a significant main effect of group (F(1, 134)=9.811, P=0.002). Meanwhile, the ANOVA revealed a significant main effect of block(F(4, 536)=15.456, P<0.001). The results showed that healthy controls and ASPD group gradually shifted their selections toward the good decks as the game progresses.The study indicated the total number of advantageous cards for subjects with antisocial personality disorder were negative correlation to the MMPI-Pd(r=-0.232, P=0.006). Conclusion The present study suggests that the decision-making impairment might be in the male subjects with antisocial personality disorder.The deficit of decision-making for ASPD might be attributed to the dysfunction of the orbitofrontal, dorsolateral frontal, and anterior cingulate cortex. Key words: Antisocial personality disorder; Decision making; Cognition

Neurobiología de la hipnosis y su contribución a la comprensión de la cognición y la conciencia.

The growing interest for the scientific study of consciousness and the current development of neuroimaging tools have allowed to inves- tigate the neuronal correlates of hypnosis and to expand its scope to assess normal and pathological neurocognitive phenomena. At an empirical level, theories that postulate hypnosis as a neurophysiological distinctive state of consciousness ('state theories'), and theories that claim that hypnosis would just represent different neurophysiological changes associated to specific suggestions without no change in the state of consciousness ('non-state theories'); have both been assessed. In this work, these two theories are critically reviewed, their main features are discussed and their neurophysiological evidence is described. A growing body of evidence supports that a hypnotic state of consciousness involves mainly the ante- rior cingulated cortex and the dorsolateral frontal cortex; as well as a pat- tern of attenuated cortical functional connectivity. Also, we concluded that hypnotic suggestions have allowed a better comprehension of a diversity of normal and pathological neuropsychological processes. Finally, we stated that the neurophysiologic evidence until now is still insufficient to solve the debate between state and non-state theorists.

The neural correlates of affect reading: An fMRI study on faces and gestures

As complex social beings, people communicate, in addition to spoken language, also via nonverbal behavior. In social face-to-face situations, people readily read the affect and intentions of others in their face expressions and gestures recognizing their meaning. Importantly, the addressee further has to discriminate the meanings of the seen communicative motor acts in order to be able to react upon them appropriately. In this functional magnetic resonance imaging study 15 healthy non-alexithymic right-handers observed video-clips that showed the dynamic evolution of emotional face expressions and gestures evolving from a neutral to a fully developed expression. We aimed at disentangling the cerebral circuits related to the observation of the incomplete and the subsequent discrimination of the evolved bodily expressions of emotion which are typical for everyday social situations. We show that the inferior temporal gyrus and the inferior and dorsal medial frontal cortex in both cerebral hemispheres were activated early in recognizing faces and gestures, while their subsequent discrimination involved the right dorsolateral frontal cortex. Interregional correlations showed that the involved regions constituted a widespread circuit allowing for a formal analysis of the seen expressions, their empathic processing and the subjective interpretation of their contextual meanings. Right–left comparisons revealed a greater activation of the right dorsal medial frontal cortex and the inferior temporal gyrus which supports the notion of a right hemispheric dominance for processing affective body expressions. These novel data provide a neurobiological basis for the intuitive understanding of other people which is relevant for socially appropriate decisions and intact social functioning.

Neuroanatomical correlates of behavioural phenotypes in behavioural variant of frontotemporal dementia

BackgroundBehavioural variant of frontotemporal dementia (bvFTD) frequently presents complex behavioural changes, that rarely occur in isolation. Targeting behavioural phenotypes instead of single behavioural symptoms may potentially provide a disease model in which to investigate brain substrates of behavioural abnormalities. ObjectiveTo identify behavioural phenotypes and to assess the associated brain correlates in a cohort of patients with bvFTD. MethodsTwo hundred and seven consecutive individuals fulfilling clinical criteria for bvFTD were enrolled. Each participant's caregiver completed frontal behavioural inventory on 24 key behavioural disturbances. Confirmatory factor analysis (CFA) models were applied, and behavioural phenotypes identified. For each phenotype, a score was derived based on the “best” CFA model (Bifactor CFA). One hundred two participants underwent SPECT scan. A regression analysis between scores for each factor and regional cerebral blood flow was carried out (P<0.001). ResultsOne “general” behavioural phenotype and four factors were identified, that were termed “disinhibited”, “apathetic”, “aggressive”, and “language” phenotypes. The most robust brain correlate was identified for “disinhibited” phenotype, in the region of the anterior cingulated and anterior temporal cortex, bilaterally, and for apathetic phenotype in the left dorsolateral frontal cortex. As expected, language phenotype correlated with greater hypoperfusion in the left frontotemporal lobes. No significant correlation between aggressive phenotype and regional cerebral blood flow was found. Moreover, the “general” behavioural severity was associated with greater damage in the right frontal lobe. ConclusionsBehavioural phenotypes are associated with specific brain damage in bvFTD, involving distinct cerebral networks.

The Framingham Brain Donation Program: Neuropathology Along the Cognitive Continuum

The Framingham Heart Study has enrolled 3 generations of participants, the original cohort (gen 1) enrolled in 1948, the offspring cohort (gen 2) enrolled in 1971 and the third generation enrolled in 2002. Participants have been undergoing prospective surveillance for incident stroke and dementia and embedded within this cohort is the voluntary Framingham Brain Donation Program that was begun in 1997. Participants who register to become brain donors have had one or more brain MR and cognitive test batteries administered. In addition, they undergo neurological evaluation as indicated, record review and post-mortem next-of-kin interview to determine the presence, type and extent of antemortem, clinical neurological diagnoses and to assign a retrospective clinical dementia rating (CDR) Scale score. Between 1997 and 2009 there were 1806 deaths, 186 of which were among registered brain donors and of these 139 brains could be examined. 58% were deemed cognitively normal at death. We present results for 3 projects; the first was to examine the sensitivity and specificity of our clinical diagnosis against the gold standard of pathological AD in 59 persons who underwent detailed cognitive assessment in the two years prior to death; we observed a 77.3% sensitivity (2 persons with AD were diagnosed clinically as Lewy body dementia) and a 91.9% specificity. The second examined the correlation of regional Alzheimer-type pathology to cognitive status at death among 34 persons who were over the age of 75 and without any significant vascular or alternative neurodegenerative pathology and found that neurofibrillary tangle counts distinguished between persons who were controls, had mild cognitive impairment, mild or moderate dementia; tangles in dorsolateral frontal cortex best distinguished MCI and controls. The third project examined the extent and severity of vascular pathology, again in a larger sample of varying cognitive abilities and in a subsample of persons with either amnestic or nonamnestic MCI. We observed that an aggregate ischemic injury score was significantly higher in persons with a CDR score of 0.5 than in normal controls.

Regionally specific alterations in functional connectivity of the anterior cingulate cortex in major depressive disorder

Depression has been associated with functional alterations in several areas of the cingulate cortex. In this study we have taken a systematic approach to examining how alterations in functional connectivity vary across the functionally diverse subregions of the rostral cingulate cortex. Method Eighteen patients with major depressive disorder, aged 15 to 24 years, were matched with 20 healthy control participants. Using resting-state functional connectivity magnetic resonance imaging (fcMRI), we systematically investigated the functional connectivity of four subregions of the rostral cingulate cortex. Voxelwise statistical maps of each subregion's connectivity with other brain areas were compared between the patient and control groups. The depressed participants showed altered patterns of connectivity with ventral cingulate subregions. They showed increased connectivity between subgenual anterior cingulate cortex (ACC) and dorsomedial frontal cortex, with connectivity strength showing positive correlation with illness severity. Depressed participants also showed increased connectivity between pregenual ACC and left dorsolateral frontal cortex, and decreased connectivity between pregenual ACC and the caudate nucleus bilaterally. The results reinforce the importance of subgenual ACC for depression, and show a close link between brain regions that support self-related processes and affective visceromotor function. The pregenual ACC also has an important role, with its increased connectivity with dorsolateral frontal cortex suggesting heightened cognitive regulation of affect; and reduced connectivity with the caudate nucleus potentially underlying symptoms such as anhedonia, reduced motivation and psychomotor dysfunction.

Gray matter network associated with risk for Alzheimer's disease in young to middle-aged adults

The apolipoprotein E (APOE) ε4 allele increases the risk for late-onset Alzheimer's disease (AD) and age-related cognitive decline. We investigated whether ε4 carriers show reductions in gray matter volume compared with ε4 non-carriers decades before the potential onset of AD dementia or healthy cognitive aging. Fourteen cognitively normal ε4 carriers, aged 26 to 45 years, were compared with 10 age-matched, ε4 non-carriers using T1-weighted volumetric magnetic resonance imaging (MRI) scans. All had reported first- or second-degree family histories of dementia. Group differences in gray matter were tested using voxel-based morphometry (VBM) and a multivariate model of regional covariance, the Scaled Subprofile Model (SSM). A combination of the first two SSM MRI gray matter patterns distinguished the APOE ε4 carriers from non-carriers. This combined pattern showed gray matter reductions in bilateral dorsolateral and medial frontal, anterior cingulate, parietal, and lateral temporal cortices with covarying relative increases in cerebellum, occipital, fusiform, and hippocampal regions. With these gray matter differences occurring decades before the potential onset of dementia or cognitive aging, the results suggest longstanding, gene-associated differences in brain morphology that may lead to preferential vulnerability for the later effects of late-onset AD or healthy brain aging.

The neural correlates of discriminating bodily displays of emotion

Aims: As complex social beings, people intentionally or unintentionally engage in bodily actions including facial expressions or gestures to convey information about their emotional state to others. The addressee has to evaluate the intention of the addresser and to categorize the bodily displays of emotion in order to react appropriately. In this functional magnetic resonance imaging (fMRI) study we wished to explore the brain areas underlying the discrimination of bodily expressions of emotions. Method: Sixteen non-alexithymic healthy subjects were presented with video-clips showing emotional face expressions or gestures evolving from a neutral to a meaningful expression. In a forced-alternative choice paradigm, subjects were instructed to discriminate by a button-press an angry expression from other emotional expressions and a negative from a positive gesture, respectively. Results: There was a main effect related to perception of face expressions and gestures in the right inferior temporal gyrus (ITG). The ITG was also active at the time point of discrimination. During perception of face expressions, the right inferior frontal gyrus (IFG) and the dorsal medial frontal cortex (DMFC) became also activated. IFG activation increased during discrimination whereas DMFC activation decreased. Activation of the DMFC was correlated with the activations in the ITG and right IFG. Moreover, there was an activation of the right dorsolateral frontal cortex (DLFC) which occurred only in relation to discrimination and correlated with the ITG, IFG and DMFC activations. Conclusion: The activation of the ITG is likely to reflect the formal visual analysis of the emotional face expressions and gestures. Discrimination involved frontal brain areas related to valuation of emotions. Thus, we believe that this study sheds light on the brain system underlying non-verbal communication in everyday face to face situations.

The Claustrum and Insula in Microcebus murinus: A High Resolution Diffusion Imaging Study

The claustrum and the insula are closely juxtaposed in the brain of the prosimian primate, the gray mouse lemur (Microcebus murinus). Whether the claustrum has closer affinities with the cortex or the striatum has been debated for many decades. Our observation of histological sections from primate brains and genomic data in the mouse suggest former. Given this, the present study compares the connections of the two structures in Microcebus using high angular resolution diffusion imaging (HARDI, with 72 directions), with a very small voxel size (90 micra), and probabilistic fiber tractography. High angular and spatial resolution diffusion imaging is non-destructive, requires no surgical interventions, and the connection of each and every voxel can be mapped, whereas in conventional tract tracer studies only a few specific injection sites can be assayed. Our data indicate that despite the high genetic and spatial affinities between the two structures, their connectivity patterns are very different. The claustrum connects with many cortical areas and the olfactory bulb; its strongest probabilistic connections are with the entorhinal cortex, suggesting that the claustrum may have a role in spatial memory and navigation. By contrast, the insula connects with many subcortical areas, including the brainstem and thalamic structures involved in taste and visceral feelings. Overall, the connections of the Microcebus claustrum and insula are similar to those of the rodents, cat, macaque, and human, validating our results. The insula in the Microcebus connects with the dorsolateral frontal cortex in contrast to the mouse insula, which has stronger connections with the ventromedial frontal lobe, yet this is consistent with the dorsolateral expansion of the frontal cortex in primates. In addition to revealing the connectivity patterns of the Microcebus brain, our study demonstrates that HARDI, at high resolutions, can be a valuable tool for mapping fiber pathways for multiple sites in fixed brains in rare and difficult-to-obtain species.

Convergent Evidence from Multimodal Imaging Reveals Amygdala Abnormalities in Schizophrenic Patients and Their First-Degree Relatives

BackgroundShared neuropathological features between schizophrenic patients and their first-degree relatives have potential as indicators of genetic vulnerability to schizophrenia. We sought to explore genetic influences on brain morphology and function in schizophrenic patients and their relatives.MethodsUsing a multimodal imaging strategy, we studied 33 schizophrenic patients, 55 of their unaffected parents, 30 healthy controls for patients, and 29 healthy controls for parents with voxel-based morphometry of structural MRI scans and functional connectivity analysis of resting-state functional MRI data.ResultsSchizophrenic patients showed widespread gray matter reductions in the bilateral frontal cortices, bilateral insulae, bilateral occipital cortices, left amygdala and right thalamus, whereas their parents showed more localized reductions in the left amygdala, left thalamus and right orbitofrontal cortex. Patients and their parents shared gray matter loss in the left amygdala. Further investigation of the resting-state functional connectivity of the amygdala in the patients showed abnormal functional connectivity with the bilateral orbitofrontal cortices, bilateral precunei, bilateral dorsolateral frontal cortices and right insula. Their parents showed slightly less, but similar changes in the pattern in the amygdala connectivity. Co-occurrences of abnormal connectivity of the left amygdala with the left orbitofrontal cortex, right dorsolateral frontal cortex and right precuneus were observed in schizophrenic patients and their parents.ConclusionsOur findings suggest a potential genetic influence on structural and functional abnormalities of the amygdala in schizophrenia. Such information could help future efforts to identify the endophenotypes that characterize the complex disorder of schizophrenia.

Perseverations and non-verbal confabulations on the Rey–Osterrieth Complex Figure Test in a fronto-temporal dementia single case study

We describe the case of a patient with late onset fronto-temporal dementia (FTD), who presented with typical personality changes, but also perseverative and confabulatory behaviors while performing the Rey–Osterrieth Complex Figure Test. We hypothesize that the progressive atrophy of orbitobasal, medial, and dorsolateral frontal cortices may give rise to both confabulations and perseverations in the non-verbal domain. In agreement with previous studies, reporting atypical profiles, this case report underlines the clinical heterogeneity of FTD. Authors declare that they have no conflicts of interest.

Meta-Analysis of Functional Neuroimaging Studies of Emotion Perception and Experience in Schizophrenia

Neuroimaging studies of emotion in schizophrenia have reported abnormalities in amygdala and other regions, although divergent results and heterogeneous paradigms complicate conclusions from single experiments. To identify more consistent patterns of dysfunction, a meta-analysis of functional imaging studies of emotion was undertaken. Searching Medline and PsycINFO databases through January 2011, 88 potential articles were identified, of which 26 met inclusion criteria, comprising 450 patients with schizophrenia and 422 healthy comparison subjects. Contrasts were selected to include emotion perception and emotion experience. Foci from individual studies were subjected to a voxelwise meta-analysis using multilevel kernel density analysis. For emotional experience, comparison subjects showed greater activation in the left occipital pole. For emotional perception, schizophrenia subjects showed reduced activation in bilateral amygdala, visual processing areas, anterior cingulate cortex, dorsolateral frontal cortex, medial frontal cortex, and subcortical structures. Schizophrenia subjects showed greater activation in the cuneus, parietal lobule, precentral gyrus, and superior temporal gyrus. Combining across studies and eliminating studies that did not balance on effort and stimulus complexity eliminated most differences in visual processing regions as well as most areas where schizophrenia subjects showed a greater signal. Reduced reactivity of the amygdala appeared primarily in implicit studies of emotion, whereas deficits in anterior cingulate cortex activity appeared throughout all contrasts. Processing emotional stimuli, schizophrenia patients show reduced activation in areas engaged by emotional stimuli, although in some conditions, schizophrenia patients exhibit increased activation in areas outside those traditionally associated with emotion, possibly representing compensatory processing.

Dis-regulation of response inhibition in adult Attention Deficit Hyperactivity Disorder (ADHD): An ERP study

Objective To define the brain activity involved in impaired response inhibition of Attention Deficit Hyperactivity Disorder (ADHD) in adults. Methods Performance measures and brain activity of 14 adult ADHD subjects and 14 controls, matched for age, gender, and overall intelligence were compared in an auditory Go–NoGo paradigm to tones. The task required a button press (Go) to 80% and inhibition of response (NoGo) to 20% of the tones, according to the tone’s pitch. Results In NoGo trials ADHD subjects made significantly more commission errors compared to controls. ERPs of ADHD subjects showed smaller amplitudes of P3 (but not N2), and longer latencies of both N2 and P3. Source current density estimation revealed reduced activity in the right frontal dorsolateral cortex and in the posterior cingulate of the ADHD group. In addition, ADHD subjects showed an unexpected significantly enhanced response inhibition in Go trials, with excessive omission errors associated with significantly larger N2 amplitudes. Conclusion In ADHD the neural networks sub-serving response inhibition are impaired. Significance ADHD is a general dis-regulation of behavioral inhibition, not limited to response inhibition.

Age-Related Metabolic Profiles in Cognitively Healthy Elders: Results from a Voxel-Based [18F]Fluorodeoxyglucose–Positron-Emission Tomography Study with Partial Volume Effects Correction: Fig 1.

Functional brain variability has been scarcely investigated in cognitively healthy elderly subjects, and it is currently debated whether previous findings of regional metabolic variability are artifacts associated with brain atrophy. The primary purpose of this study was to test whether there is regional cerebral age-related hypometabolism specifically in later stages of life. MR imaging and FDG-PET data were acquired from 55 cognitively healthy elderly subjects, and voxel-based linear correlations between age and GM volume or regional cerebral metabolism were conducted by using SPM5 in images with and without correction for PVE. To investigate sex-specific differences in the pattern of brain aging, we repeated the above voxelwise calculations after dividing our sample by sex. Our analysis revealed 2 large clusters of age-related metabolic decrease in the overall sample, 1 in the left orbitofrontal cortex and the other in the right temporolimbic region, encompassing the hippocampus, the parahippocampal gyrus, and the amygdala. The division of our sample by sex revealed significant sex-specific age-related metabolic decrease in the left temporolimbic region of men and in the left dorsolateral frontal cortex of women. When we applied atrophy correction to our PET data, none of the above-mentioned correlations remained significant. Our findings suggest that age-related functional brain variability in cognitively healthy elderly individuals is largely secondary to the degree of regional brain atrophy, and the findings provide support to the notion that appropriate PVE correction is a key tool in neuroimaging investigations.

Cortical Input to the Frontal Pole of the Marmoset Monkey

We used fluorescent tracers to map the pattern of cortical afferents to frontal area 10 in marmosets. Dense projections originated in several subdivisions of orbitofrontal cortex, in the medial frontal cortex (particularly areas 14 and 32), and in the dorsolateral frontal cortex (particularly areas 8Ad and 9). Major projections also stemmed, in variable proportions depending on location of the injection site, from both the inferior and superior temporal sensory association areas, suggesting a degree of audiovisual convergence. Other temporal projections included the superior temporal polysensory cortex, temporal pole, and parabelt auditory cortex. Medial area 10 received additional projections from retrosplenial, rostral calcarine, and parahippocampal areas, while lateral area 10 received small projections from the ventral somatosensory and premotor areas. There were no afferents from posterior parietal or occipital areas. Most frontal connections were balanced in terms of laminar origin, giving few indications of an anatomical hierarchy. The pattern of frontopolar afferents suggests an interface between high-order representations of the sensory world and internally generated states, including working memory, which may subserve ongoing evaluation of the consequences of decisions as well as other cognitive functions. The results also suggest the existence of functional differences between subregions of area 10.