Self-reported nocturnal sleep duration is associated with next-day resting state functional connectivity

Sleep deprivation affects cerebral metabolism and reduces the functional connectivity among various regions of the brain, potentially explaining some of the associated mood and emotional changes often observed. Prior neuroimaging studies have only examined the effects of sleep deprivation or partial sleep restriction on functional connectivity, but none have studied how such connectivity is associated with normal variations in self-reported sleep duration the night before the scan. We examined the relationship between sleep duration and resting state functional connectivity among healthy volunteers who slept at home according to their own schedules. Thirty-nine healthy individuals aged 18-45 (21 females) completed a questionnaire asking about their recent sleep habits and entries in their sleep diary for the previous night, followed by resting state functional MRI at 3 T. Participants reported sleeping between 5.0 and 8.5 h the night before the scan (M=7.0, SD=0.9). Seed regions were placed in the medial prefrontal cortex and posterior cingulate cortex nodes of the default mode network, regions previously implicated in sleep deprivation. Longer self-reported sleep duration was associated with significantly enhanced functional connectivity between the medial prefrontal cortex and posterior cingulate, as well as greater anticorrelations with parietal, occipital, and lateral prefrontal regions. Findings suggest that even normal variations in sleep duration measured by self-report are related to the strength of functional connectivity within select nodes of the default mode network and its anticorrelated network.     

Linking generalized spike-and-wave discharges and resting state brain activity by using EEG/fMRI in a patient with absence seizures

PURPOSE: To illustrate a functional interpretation of blood oxygen level-dependent (BOLD) signal changes associated with generalized spike-and-wave discharges in patients with absence seizures and to demonstrate the reproducibility of these findings in one case. METHODS: In a 47 year-old patient with frequent absence seizures, BOLD signal changes during generalized spike-and-wave discharges (GSWD) were mapped by using simultaneous and continuous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) at 1.5 T and 6 months later at 3 T. GSWDs were modeled as individual events and as blocks. RESULTS: The patient studied exhibited frequent generalized spike-wave activity with temporal properties ideal for study with EEG/fMRI. Highly reproducible GSWD-associated fMRI signal decreases (deactivations) were seen in bilateral frontal and temporoparietal cortices and the precuneus, in addition to activations in occipital cortex and, at 3 T, the posterior thalamus. CONCLUSIONS: The GSWD-associated changes seen here involve cortical regions that have been shown to be more active at conscious rest compared with sleep and with various types of extroverted perception and action. These regions have been proposed to constitute the core of a functional "default mode" system. We propose that the findings of deactivation of this distributed brain system during GSWDs mirrors the clinical manifestation of GSWDs (i.e., absence seizures). Furthermore, we suggest that these deactivations may reflect the functional consequences of GSWDs on physiologic brain activity at rest rather than direct hemodynamic correlates of epileptic discharges.     

Impact of interictal epileptic activity on normal brain function in epileptic encephalopathy: an electroencephalography-functional magnetic resonance imaging study

Using electroencephalography (EEG) in combination with functional magnetic resonance imaging (fMRI), we studied a 9.5-year-old girl who developed cognitive and behavioral regression in association with intense interictal bilaterally synchronous epileptic discharges (IBSEDs) both during the awake state and during sleep. During runs of IBSEDs, EEG-fMRI demonstrated deactivations in the lateral and medial frontoparietal cortices, posterior cingulate gyrus, and cerebellum together with focal relative activations in the right frontal, parietal, and temporal cortices. The deactivations probably reflect the repercussion of the interictal epileptic activity on normal brain function which might cause the neuropsychological regression by inducing repetitive interruptions of neurophysiological function resulting in a chronic state of specific psychomotor impairment. The relative activations could possibly indicate the source of epileptic activity rapidly spreading to other brain regions.     

EEG-fMRI study of the ictal and interictal epileptic activity in patients with eyelid myoclonia with absences

Purpose: To investigate the blood oxygenation level‐dependent (BOLD) signal changes correlated with ictal and interictal epileptic discharges using electroencephalography‐correlated functional magnetic resonance imaging (EEG‐fMRI) in patients with eyelid myoclonia with absences (EMA) and then to explore the pathophysiological mechanisms of epileptic discharges and their effect on brain function. Methods: Four patients with EMA were investigated through the method of EEG‐fMRI. The characteristics of BOLD signal changes linked to ictal and interictal epileptic discharges under different states of consciousness were explored. Results: Seven sessions of EEG‐fMRI scanning in the four patients were obtained. The main regions of activation included thalamus, mesial frontal cortex, middle parietal lobe, temporal lobe, insula, midline structures, and cerebellum. Deactivations were mainly in the anterior frontal lobe, posterior parietal lobe, and posterior cingulate gyrus. Thalamic BOLD change was predominantly activation in most of our cases. The distribution of activation associated with ictal epileptic discharges was wider, and the distribution of deactivation was closer to pericortex compared with the BOLD change linked with interictal epileptic discharges. Conclusions: The activation in the thalamus may be associated with generalized spike wave in EMA; the combination of different patterns of activation with consistent pattern of deactivations (“default” pattern) in patients with EMA may prognosticate different states of consciousness in response to ictal and interictal epileptic discharges.     

Increased cortical BOLD signal anticipates generalized spike and wave discharges in adolescents and adults with idiopathic generalized epilepsies

Purpose: Electroencephalography–functional magnetic resonance imaging (EEG‐fMRI) coregistration has recently revealed that several brain structures are involved in generalized spike and wave discharges (GSWDs) in idiopathic generalized epilepsies (IGEs). In particular, deactivations and activations have been observed within the so‐called brain default mode network (DMN) and thalamus, respectively. In the present study we analyzed the dynamic time course of blood oxygen level–dependent (BOLD) changes preceding and following 3 Hz GSWDs in a group of adolescent and adult patients with IGE who presented with absence seizures (AS). Our aim was to evaluate cortical BOLD changes before, during, and after GSWD onset. Methods: Twenty‐one patients with IGE underwent EEG‐fMRI coregistration. EEG‐related analyses were run both at the single‐subject and at group level (random effect). The time‐course analysis was conducted for 3 s time windows before, during, and after GSWDs, and they were included until no further BOLD signal changes were observed. Key Findings: Fifteen patients (nine female, mean age 28 years) had GSWDs during EEG‐fMRI coregistration (262 total events, mean duration 4 s). Time‐course group analysis showed BOLD increments starting approximately 10 s before GSWD onset located in frontal and parietal cortical areas, and especially in the precuneus‐posterior cingulate region. At GSWD onset, BOLD increments were located in thalamus, cerebellum, and anterior cingulate gyrus, whereas BOLD decrements were observed in the DMN regions persisting until 9 s after onset. Significance: Hemodynamic changes (BOLD increments) occurred in specific cortical areas, namely the precuneus/posterior cingulate, lateral parietal, and frontal cortices, several seconds before EEG onset of GSWD. A dysfunction of these brain regions, some of which belongs to the DMN, may be crucial in generating GSWDs in patients with IGE.     

Neural correlates of a single-session massage treatment

The current study investigated the immediate neurophysiological effects of different types of massage in healthy adults using functional magnetic resonance imaging (fMRI). Much attention has been given to the default mode network, a set of brain regions showing greater activity in the resting state. These regions (i.e. insula, posterior and anterior cingulate, inferior parietal and medial prefrontal cortices) have been postulated to be involved in the neural correlates of consciousness, specifically in arousal and awareness. We posit that massage would modulate these same regions given the benefits and pleasant affective properties of touch. To this end, healthy participants were randomly assigned to one of four conditions: 1. Swedish massage, 2. reflexology, 3. massage with an object or 4. a resting control condition. The right foot was massaged while each participant performed a cognitive association task in the scanner. We found that the Swedish massage treatment activated the subgenual anterior and retrosplenial/posterior cingulate cortices. This increased blood oxygen level dependent (BOLD) signal was maintained only in the former brain region during performance of the cognitive task. Interestingly, the reflexology massage condition selectively affected the retrosplenial/posterior cingulate in the resting state, whereas massage with the object augmented the BOLD response in this region during the cognitive task performance. These findings should have implications for better understanding how alternative treatments might affect resting state neural activity and could ultimately be important for devising new targets in the management of mood disorders.     

Bildgebung bei epileptischen Enzephalopathien

Epileptic encephalopathies (EE) belong to the group of epilepsies which are associated with expressed cognitive and behavioral disturbances subsequent to epileptic activity. Despite the great importance of EE in the development and psychosocial adaptation of affected children, the mechanisms of cognitive deficits in EE have so far been insufficiently investigated. This review article summarizes the various neuroimaging studies which have tried to describe specific neuronal networks in EE. The results show that although epileptic activity in EE can be generated in different brain regions, specific propagation pathways and networks exist which are very characteristic for each different form of encephalopathy. In some forms of EE the epileptic activity seems to impair the integrity of the default mode network and possibly to interfere with cognitive function through this mechanism. Furthermore, there are further mechanisms underlying EE, e.g. abnormal connectivity patterns between brain regions which participate in the control of cognitive functions and impairment of the connections and activities in the thalamocortical network.     

fMRI correlates of interictal epileptic activity in patients with idiopathic benign focal epilepsy of childhood. A simultaneous EEG-functional MRI study

EEG-correlated fMRI (EEG/fMRI) can identify alterations of brain function associated with interictal epileptiform discharges (IED). fMRI activation can localize the irritative zone and indicate functional disturbance distant from the spike focus. This might be of particular interest in paediatric epilepsy syndromes with frequent IED. Using simultaneous EEG/fMRI in a 3T MR scanner we studied blood oxygen level-dependent (BOLD) signal changes related to spontaneous IED in 10 children with typical and atypical benign focal epilepsy of childhood (BFE) or benign epileptic activity of childhood (BEAC). EEG artefacts were subtracted offline and IED were used as regressors for event-related fMRI analysis in SPM2. In four of the seven children with IED during EEG/fMRI we found IED related positive and negative signal changes (p<0.001, uncorrected). In three children we found only significant negative signal changes. At a more liberal threshold (p<0.05, uncorrected) these three children had positive signal changes congruent with the four children with significant positive signal changes. In summary, we found positive or negative signal changes in perisylvian, central, premotor and prefrontal regions. One child showed additional bilateral occipital fMRI activation. In addition to former reports our results indicated that frontal brain areas are functionally disturbed during IED corresponding to general neuropsychological findings in BFE and BEAC. We conclude that using EEG/fMRI it might be possible to localize generators of IED and functionally disturbed brain regions in children with BFE. Further studies are required to differentiate between BFE subtypes and to identify fMRI signatures of specific syndromes or corresponding neuropsychological deficits.     

Spontaneous low-frequency fluctuations in the BOLD signal in schizophrenic patients: anomalies in the default network

Spontaneous low-frequency fluctuations in the blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (MRI) signal have been shown to reflect neural synchrony between brain regions. A "default network" of spontaneous low-frequency fluctuations has been described in healthy volunteers during stimulus-independent thought. Negatively correlated with this network are regions activated during attention-demanding tasks. Both these networks involve brain regions and functions that have been linked with schizophrenia in previous research. The present study examined spontaneous slow fluctuations in the BOLD signal at rest, as measured by correlation with low-frequency oscillations in the posterior cingulate, in 17 schizophrenic patients, and 17 comparable healthy volunteers. Healthy volunteers demonstrated correlation between spontaneous low-frequency fluctuations of the BOLD signal in the posterior cingulate and fluctuations in the lateral parietal, medial prefrontal, and cerebellar regions, similar to previous reports. Schizophrenic patients had significantly less correlation between spontaneous slow activity in the posterior cingulate and that in the lateral parietal, medial prefrontal, and cerebellar regions. Connectivity of the posterior cingulate was found to vary with both positive and negative symptoms in schizophrenic patients. Because these data suggest significant abnormalities in resting-state neural networks in schizophrenia, further investigations of spontaneous slow fluctuations of the BOLD signal seem warranted in this population.     

Functional Magnetic Resonance Imaging of Working Memory among Multiple Sclerosis Patients

BACKGROUND AND PURPOSE: Verbal working memory (VWM) deficits have been a well-replicated finding among patients with multiple sclerosis (MS). Functional magnetic resonance imaging (FMRI) studies have described a VWM system in healthy samples; however, functional neuroimaging of this system among MS patients is just beginning to appear. METHODS: Fifteen MS patients and 15 sex-, age-, education-, and IQ-matched healthy control (HC) participants completed a 2-Back VWM task as whole-brain FMRI was conducted. RESULTS: Each group exhibited increased brain activity compared to the O-Back control task in regions associated with the 2-Back in previous neuroimaging studies. These included Broca's area, supplementary motor area (SMA), premotor cortices (PMC), and dorsolateral prefrontal cortices (DLPFC). MS patients exhibited greater cortical activity than did HC participants in left primary motor and somatosensory cortices, PMC, DLPFC, anterior cingulate, and bilateral SMA. MS patients exhibited relatively less activation in Broca's area, bilateral cerebellum, and other regions not typically associated with the 2-Back (e.g., right fusiform gyrus, left lingual gyrus, right hippocampus). Performance accuracy and reaction time did not differ between groups. CONCLUSIONS: Normal performance of a challenging VWM task among high-functioning MS patients is associated with a shift toward greater activity in regions related to sensorimotor functions and anterior attentional/executive components of the VWM system. Posterior memory storage systems appeared unaffected, while portions of the visual processing and subvocal rehearsal systems were less active. Although a shift in neural activity was noted relative to HC participants, deviation from regions normally involved in VWM function was not observed in this patient sample.     

Future planning: default network activity couples with frontoparietal control network and reward-processing regions during process and outcome simulations

We spend much of our daily lives imagining how we can reach future goals and what will happen when we attain them. Despite the prevalence of such goal-directed simulations, neuroimaging studies on planning have mainly focused on executive processes in the frontal lobe. This experiment examined the neural basis of process simulations, during which participants imagined themselves going through steps toward attaining a goal, and outcome simulations, during which participants imagined events they associated with achieving a goal. In the scanner, participants engaged in these simulation tasks and an odd/even control task. We hypothesized that process simulations would recruit default and frontoparietal control network regions, and that outcome simulations, which allow us to anticipate the affective consequences of achieving goals, would recruit default and reward-processing regions. Our analysis of brain activity that covaried with process and outcome simulations confirmed these hypotheses. A functional connectivity analysis with posterior cingulate, dorsolateral prefrontal cortex and anterior inferior parietal lobule seeds showed that their activity was correlated during process simulations and associated with a distributed network of default and frontoparietal control network regions. During outcome simulations, medial prefrontal cortex and amygdala seeds covaried together and formed a functional network with default and reward-processing regions.     

Mechanistic Comparisons of Functional Domains across Pediatric and Adult Bipolar Disorder Highlight Similarities, As Well As Differences, Influenced by the Developing Brain

Recent neuroimaging studies have uncovered much about the specific neural deficits in adult bipolar disorder (ABD), but despite promising results, neuroimaging research for pediatric bipolar disorder (PBD) is still developing. The neuroimaging literature is highly heterogeneous, varying in the paradigms used and in participants' mood states and medication status. Despite this variability, several dominant patterns emerge. In response to emotional stimuli, both ABD and PBD show limbic hyperactivity coupled with hypoactivity in ventral prefrontal emotion regulation systems. This pattern occurred most robustly in response to negative incidental stimuli and was especially apparent in manic PBD. ABD showed more variability in ventral prefrontal activity, possibly due to maturational and medication factors. On numerous cognitive paradigms, PBD showed dorsal prefrontal hypoactivity linked to ventral dysfunction, whereas ABD showed compensatory frontal, parietal, and temporal activity with paradigm-specific variations. In emotion-cognition interaction paradigms, patients show dysregulation in regions interfacing between cognitive and emotional brain systems (e.g., ventral prefrontal and cingulate cortices), which expend extra effort to process emotional stimuli effectively and recruit additional posterior attention systems to cope with affective instability. In addition, novel functional connectivity techniques have uncovered connectivity deficits between frontal and limbic regions in ABD and PBD at rest and during active emotional and cognitive tasks. Finally, the neuroimaging literature currently lacks cross-sectional studies comparing PBD with ABD and longitudinal studies following children and adolescents with BD into adulthood. Such studies would provide important insights into patients' prognosis and would determine targets for early interventions in the evolving illness diathesis.     

Functional brain mapping of ictal activity in gelastic epilepsy associated with hypothalamic hamartoma: A case report

Hypothalamic hamartomas (HHs) have been demonstrated as the cause of gelastic epilepsy, both by intracranial electrodes and functional imaging. The neocortex becomes secondarily involved, through poorly characterized propagation pathways. The detailed dynamics of seizure spread have not yet been demonstrated, owing to the limited spatial–temporal resolution of available functional mapping. We studied a patient with epilepsy associated with HH and gelastic epilepsy. Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) of several seizure events were obtained, with blood oxygen level dependent (BOLD) activation of the hamartoma, and left hemisphere hypothalamus, hippocampus, parietal–occipital area, cingulate gyrus, and dorsal–lateral frontal area. Integration of regional BOLD kinetics and EEG power dynamics strongly suggests propagation of the epileptic activity from the HH through the left fornix to the temporal lobe, and later through the cingulate fasciculus to the left frontal lobe. The EEG/fMRI method has the spatial–temporal resolution to study the dynamics of seizure activity, with detailed demonstration of origin and propagation pathways.     

EEG-correlated fMRI of human alpha (de-)synchronization

ObjectivesWe investigated blood oxygenation level-dependent (BOLD) brain activity changes in wakefulness and light sleep and in relation to those associated with the posterior alpha rhythm, the most prominent feature of the clinical EEG. Studies have reported different sets of brain regions changing their oxygen consumption with waxing and waning alpha oscillations. Here, we hypothesize that these dissimilar activity patterns reflect different wakefulness-dependent brain states.MethodsWe recorded BOLD signal changes and electroencephalography (EEG) simultaneously in 149 subjects at rest. Based on American Academy of Sleep Medicine criteria, we selected subjects exhibiting wakefulness or light sleep (N1). We identified brain regions in which BOLD signal changes correlated with (i) clinical sleep stages, (ii) alpha band power and (iii) a multispectral EEG index, respectively.ResultsDuring light sleep, we found increased BOLD activity in parieto-occipital regions. In wakefulness compared to light sleep, we revealed BOLD signal increases in the thalamus. The multispectral EEG-index revealed hippocampal activity changes in light sleep not reported before.ConclusionChanges in alpha oscillations reflect different brain states associated with different levels of wakefulness and thalamic activity. We can link the previously described parieto-occipital pattern to drowsiness. Additionally, in that stage, we identify hippocampal activity fluctuations.SignificanceThalamic activity varies with early changes of wakefulness, which is important to consider in resting state experiments. The EEG-indexed activation of the hippocampus during light sleep suggests that memory encoding might already take place during this early stage of sleep.     

Greater preference consistency during the Willingness-to-Pay task is related to higher resting state connectivity between the ventromedial prefrontal cortex and the ventral striatum

The significance of why a similar set of brain regions are associated with the default mode network and value-related neural processes remains to be clarified. Here, we examined i) whether brain regions exhibiting willingness-to-pay (WTP) task-related activity are intrinsically connected when the brain is at rest, ii) whether these regions overlap spatially with the default mode network, and iii) whether individual differences in choice behavior during the WTP task are reflected in functional brain connectivity at rest. Blood-oxygen-level dependent (BOLD) signal was measured by functional magnetic resonance imaging while subjects performed the WTP task and at rest with eyes open. Brain regions that tracked the value of bids during the WTP task were used as seed regions in an analysis of functional connectivity in the resting state data. The seed in the ventromedial prefrontal cortex was functionally connected to core regions of the WTP task-related network. Brain regions within the WTP task-related network, namely the ventral precuneus, ventromedial prefrontal and posterior cingulate cortex overlapped spatially with publically available maps of the default mode network. Also, those individuals with higher functional connectivity during rest between the ventromedial prefrontal cortex and the ventral striatum showed greater preference consistency during the WTP task. Thus, WTP task-related regions are an intrinsic network of the brain that corresponds spatially with the default mode network, and individual differences in functional connectivity within the WTP network at rest may reveal a priori biases in choice behavior.     

Neural correlates of 'functional' symptoms in neurology

Functional symptoms are neurological deficits that are not explained by organic lesions in the nervous system, but usually associated with emotional "psychogenic" disturbances. These symptoms are common and can affect any aspect of elementary neurological function, presenting clinicians with difficulties in definition, diagnosis, and treatment. Although current concepts explain functional symptoms in the context of "psychogenic" stress, the exact nature of these symptoms remains largely unknown. Recent functional neuroimaging studies have shifted understanding of these deficits from a psychological and psychodynamic model to a neurobiological model. This review highlights the advances made using functional neuroimaging techniques in patients suffering from two conditions: unilateral loss of motor function and psychogenic parkinsonism. The evidence suggests that areas including the prefrontal and parietal cortices, anterior cingulate cortex, thalamus, and basal ganglia may be implicated. Future studies, assessing patients at different phases of their illness and using newer techniques such as functional MRI, are needed to extend current findings on functional symptoms.     

sLORETA and fMRI Detection of Medial Prefrontal Default Network Anomalies in Adult ADHD

Attention deficit hyperactivity disorder (ADHD) is a developmental psychiatric disorder thought to affect approximately 5 to 10% of school-age children, of whom 30 to 65% continue to exhibit symptoms into adulthood. The prevalence of ADHD in adults is also an estimated 4%, second only to depression. Across studies there appear to be significant network dysfunctions involved in ADHD. Typically the foci of interest in ADHD included the insular cortices, frontal lobes, basal ganglia, and cerebellum. More recently, attention has been directed to the default network of the brain and its functional integrity in ADHD with focus on the precuneus and parietal lobes and interactions with medial prefrontal cortices. Functional magnetic resonance imaging (fMRI) measures neurovascular coupling as measured by the blood oxygenated level dependent signal (BOLD). Electroencephalogram (EEG) measures brain electrical information. Because fMRI is an indirect measure of neuronal activity and EEG is a direct measure, combining the results from these two imaging modalities under the same task conditions may provide a more complete story as to the what (EEG) and where (fMRI) activity exists. This article discusses the benefits of using standardized low resolution electromagnetic tomography (sLORETA) analysis of the EEG as compared to fMRI. The goal of the study, the data from which we use for our justification, was to discover the functional differences in ADHD and non-ADHD brains with different brain imaging modalities. We hoped to elucidate functional connectivity patterns by interpreting the data acquired with the EEG using sLORETA and the data acquired with the fMRI scans. We further hoped to find correlation with the sLORETA and fMRI interpretations so as to confirm that EEG is an adequate stand-alone methodology to evaluate ADHD. Participants included 6 ADHD and 7 non-ADHD subjects. They were initially interviewed by phone and administered the Connors Rating Scale and the Mini International Neuropsychiatric Interview to determine accuracy of symptom reporting and to rule out psychological comorbidities. Exclusion criteria consisted of previous head trauma, recent drug or alcohol abuse (14 days), or neurological syndromes. We recorded sequential 19-channel EEG and fMRI during the eyes-open and eyes-closed states and while performing the Stroop test. The QEEG results were evaluated with comparison to a normative database and with sLORETA analysis. Functional connectivity was assessed using the seed-based approach in sLORETA. The fMRI results were evaluated using Brain Voyager? and other neuroimaging software packages. sLORETA and fMRI data identify a region in medial Brodmann Area (BA) 10 of the default network. Furthermore, regional frontal differences extend to medial BA 32 with more emphasis to left prefrontal. sLORETA determines there is less current source density at BA 10 in the ADHD participants than controls. sLORETA is adequate in localizing the sources of the EEG in the default network as contrasted with fMRI. It is important to note that sLORETA can provide important information about the direction of difference relative to the BOLD signal increase, which cannot be done with the fMRI alone.     

Losing the struggle to stay awake: Divergent thalamic and cortical activity during microsleeps

Maintaining alertness is critical for safe and successful performance of most human activities. Consequently, microsleeps during continuous visuomotor tasks, such as driving, can be very serious, not only disrupting performance but sometimes leading to injury or death due to accidents. We have investigated the neural activity underlying behavioral microsleeps – brief (0.5–15 s) episodes of complete failure to respond accompanied by slow eye‐closures – and EEG theta activity during drowsiness in a continuous task. Twenty healthy normally‐rested participants performed a 50‐min continuous tracking task while fMRI, EEG, eye‐video, and responses were simultaneously recorded. Visual rating of performance and eye‐video revealed that 70% of the participants had frequent microsleeps. fMRI analysis revealed a transient decrease in thalamic, posterior cingulate, and occipital cortex activity and an increase in frontal, posterior parietal, and parahippocampal activity during microsleeps. The transient activity was modulated by the duration of the microsleep. In subjects with frequent microsleeps, power in the post‐central EEG theta was positively correlated with the BOLD signal in the thalamus, basal forebrain, and visual, posterior parietal, and prefrontal cortices. These results provide evidence for distinct neural changes associated with microsleeps and with EEG theta activity during drowsiness in a continuous task. They also suggest that the occurrence of microsleeps during an active task is not a global deactivation process but involves localized activation of fronto‐parietal cortex, which, despite a transient loss of arousal, may constitute a mechanism by which these regions try to restore responsiveness. Hum Brain Mapp 35:257–269, 2014. © 2012 Wiley Periodicals, Inc.     

Neocortical modulation of the amygdala response to fearful stimuli.

BACKGROUND: The cortical circuitry involved in conscious cognitive processes and the subcortical circuitry involved in fear responses have been extensively studied with neuroimaging, but their interactions remain largely unexplored. A recent functional magnetic resonance imaging (fMRI) study demonstrated that the engagement of the right prefrontal cortex during the cognitive evaluation of angry and fearful facial expressions is associated with an attenuation of the response of the amygdala to these same stimuli, providing evidence for a functional neural network for emotional regulation. METHODS: In the current study, we have explored the generalizability of this functional network by using threatening and fearful non-face stimuli derived from the International Affective Picture System (IAPS), as well as the influence of this network on peripheral autonomic responses. RESULTS: Similar to the earlier findings with facial expressions, blood oxygen level dependent fMRI revealed that whereas perceptual processing of IAPS stimuli was associated with a bilateral amygdala response, cognitive evaluation of these same stimuli was associated with attenuation of this amygdala response and a correlated increase in response of the right prefrontal cortex and the anterior cingulate cortex. Moreover, this pattern was reflected in changes in skin conductance. CONCLUSIONS: The current results further implicate the importance of neocortical regions, including the prefrontal and anterior cingulate cortices, in regulating emotional responses mediated by the amygdala through conscious evaluation and appraisal.     

Widespread epileptic networks in focal epilepsies: EEG-fMRI study

Purpose: To assess the extent of brain involvement during focal epileptic activity, we studied patterns of cortical and subcortical metabolic changes coinciding with interictal epileptic discharges (IEDs) using group analysis of simultaneous electroencephalography and functional magnetic resonance imaging (EEG‐fMRI) scans in patients with focal epilepsy. Methods: We selected patients with temporal lobe epilepsy (TLE, n = 32), frontal lobe epilepsy (FLE, n = 14), and posterior quadrant epilepsy (PQE, n = 20) from our 3 Tesla EEG‐fMRI database. We applied group analysis upon the blood oxygen–level dependent (BOLD) response associated with focal IEDs. Key Findings: Patients with TLE and FLE showed activations and deactivations, whereas in PQE only deactivations occurred. In TLE and FLE, the largest activation was in the mid–cingulate gyri bilaterally. In FLE, activations were also found in the ipsilateral frontal operculum, thalamus, and internal capsule, and in the contralateral cerebellum, whereas in TLE, we found additional activations in the ipsilateral mesial and neocortical temporal regions, insula, and cerebellar cortex. All three groups showed deactivations in default mode network regions, the most widespread being in the TLE group, and less in PQE and FLE. Significance: These results indicate that different epileptic syndromes result in unique and widespread networks related to focal IEDs. Default mode regions are deactivated in response to focal discharges in all three groups with syndrome specific pattern. We conclude that focal IEDs are associated with specific networks of widespread metabolic changes that may cause more substantial disturbance to brain function than might be appreciated from the focal nature of the scalp EEG discharges.