Reorganization Of Regions Research Articles

The microstructural status of the corpus callosum is associated with the degree of motor function and neurological deficit in stroke patients.

Human neuroimaging studies and animal models have suggested that white matter damage from ischemic stroke leads to the functional and structural reorganization of perilesional and remote brain regions. However, the quantitative relationship between the transcallosal tract integrity and clinical motor performance score after stroke remains unexplored. The current study employed a tract-based spatial statistics (TBSS) analysis on diffusion tensor imaging (DTI) to investigate the relationship between white matter diffusivity changes and the clinical scores in stroke patients. Probabilistic fiber tracking was also used to identify structural connectivity patterns in the patients. Thirteen ischemic stroke patients and fifteen healthy control subjects participated in this study. TBSS analyses showed that the corpus callosum (CC) and bilateral corticospinal tracts (CST) in the stroke patients exhibited significantly decreased fractional anisotropy and increased axial and radial diffusivity compared with those of the controls. Correlation analyses revealed that the motor and neurological deficit scores in the stroke patients were associated with the value of diffusivity indices in the CC. Compared with the healthy control group, probabilistic fiber tracking analyses revealed that significant changes in the inter-hemispheric fiber connections between the left and right motor cortex in the stroke patients were primarily located in the genu and body of the CC, left anterior thalamic radiation and inferior fronto-occipital fasciculus, bilateral CST, anterior/superior corona radiate, cingulum and superior longitudinal fasciculus, strongly suggesting that ischemic induces inter-hemispheric network disturbances and disrupts the white matter fibers connecting motor regions. In conclusion, the results of the present study show that DTI-derived measures in the CC can be used to predict the severity of motor skill and neurological deficit in stroke patients. Changes in structural connectivity pattern tracking between the left and right motor areas, particularly in the body of the CC, might reflect functional reorganization and behavioral deficit.

Environmental Governance and Shifts in Canadian Biofuel Production and Innovation

Canada's adoption of international climate commitments, national emissions standards, and incentive programs drove expansion of biofuel production using available first-generation technologies in feedstock-rich regions. Market saturation and the emergence of second-generation technologies shifted government support away from first-generation technologies, placing pressure on regional production clusters. This article analyzes how Canadian biofuel firms restructured their value-chain activities in response to those technological and policy changes. The ability to access technologies and navigate multiscalar policy contexts shapes restructuring. Geographic patterns of cellulosic innovation are identified, and the role of firms and policy in regional industrial reorganization is discussed.

Assessment of cerebral dopamine D 2 / 3 -receptors in patients with bilateral vestibular failure

Absence of peripheral vestibular input in bilateral vestibular failure (BVF) has been suggested to induce plastic reorganization in various brain regions. Among several neurotransmitters, dopamine is known to play a key role in cortico-striatal-sensorimotor processing. However, the role of dopamine in vestibular plasticity is scantly documented. Assessment of D 2/3 formula-receptors in patients with BVF. D 2/3 formula-receptor-PET using [18F]fallypride and MRI examinations were performed in 12 BVF-patients and 13 healthy controls. BVF-patients showed reduced D 2/3 formula-receptor availability (approximately 40%) in the temporo-parieto-occipital cortex bilaterally, including the multisensory vestibular cortex and visual motion-sensitive areas (MT/MST), as well as in the striatum and the right thalamus. Longer illness duration was associated with bilaterally lower D 2/3 formula-receptor availability in the middle/superior temporal gyrus (GTm/s). D 2/3 formula-receptor availability in the right GTm/s and bilateral insula decreased with severity of symptoms. BVF-patients with oscillopsia showed reduced D 2/3 formula-receptor availability in the right MT/MST and midbrain tectum. Reduced D 2/3 formula-receptor availability in multisensory vestibular cortical network areas and basal ganglia may indicate a receptor down-regulation due to the lack of peripheral vestibular input. The more pronounced decline in D 2/3 formula-receptor availability in the multisensory vestibular cortex in patients with prolonged illness suggests the occurrence of progressive changes in dopamine transmission.

NI-42 * ALTERED STRUCTURAL CONNECTIVITY IN WIDELY DISTRIBUTED BILATERAL HEMISPHERIC NETWORKS OF PATIENTS WITH GLIOBLASTOMA

BACKGROUND: Glioblastomas (GBMs) typically involve the cerebral white matter and infiltrate well beyond the enhancing bulky tumor seen on MRI; thus, they can disrupt white matter fiber tracts. In this study, we evaluated how unilateral GBMs affect the structural organization of hemispheric networks. METHODS: Ten patients with newly-diagnosed unilateral GBM (age: 61 ± 11 years, 6 males, 4 left-sided, tumor size: 34.1 ± 22.7cm3) and 10 healthy controls (age: 67 ± 8 years, 5 males) underwent 3T diffusion-weighted MRI. Whole brain tractography was performed using a recently developed approach (independent component analysis with ball-and-stick model; Jeong et al., Magn Reson Med, 2013;70:441-53). In each subject, a total of 116 cortical regions of interest were generated by fitting a deformable template resulting in a 116x116 connectivity matrix where the elements quantify the pair-wise connectivity scores (i.e., fiber numbers connecting any two cortical regions which were normalized to the corresponding tract lengths). From this matrix we calculated three network properties in both hemispheres: global efficiency (characterizing structural integration), local efficiency (characterizing structural segregation), and clustering coefficient (characterizing structural complexity). RESULTS: GBM patients showed significantly reduced global efficiency, local efficiency, and clustering coefficients in both affected and contralateral hemispheres, as compared to the control group (p < 0.0001 in all comparisons). Larger tumor size was associated with more severely reduced global efficiency (p = 0.007 and p = 0.004 in affected and contralateral hemisphere, respectively), local efficiency (p = 0.02 and p = 0.003) and clustering coefficient (p = 0.04 and p = 0.006). Signs of intrahemispheric network reorganization were also observed in the affected hemisphere of individual patients. CONCLUSIONS: The structural organization is less efficient and less complex in both cerebral hemispheres of patients with unilateral GBM, although regional reorganization may occur on the affected side. Larger tumors are associated with more severe hemispheric network abnormalities. These alterations in widely-distributed neuronal networks may underlie some of the neurocognitive co-morbidities in these patients.

Functional reorganization of the visual dorsal stream as probed by 3-D visual coherence in Williams syndrome.

Object and depth perception from motion cues involves the recruitment of visual dorsal stream brain areas. In 3-D structure-from-motion (SFM) perception, motion and depth information are first extracted in this visual stream to allow object categorization, which is in turn mediated by the ventral visual stream. Such interplay justifies the use of SFM paradigms to understand dorsal-ventral integration of visual information. The nature of such processing is particularly interesting to be investigated in a neurological model of cognitive dissociation between dorsal (impaired) and ventral stream (relatively preserved) processing, Williams syndrome (WS). In the current fMRI study, we assessed dorsal versus ventral stream processing by using a performance-matched 3-D SFM object categorization task. We found evidence for substantial reorganization of the dorsal stream in WS as assessed by whole-brain ANOVA random effects analysis, with subtle differences in ventral activation. Dorsal reorganization was expressed by larger medial recruitment in WS (cuneus, precuneus, and retrosplenial cortex) in contrast with controls, which showed the expected dorsolateral pattern (caudal intraparietal sulcus and lateral occipital cortex). In summary, we found a substantial reorganization of dorsal stream regions in WS in response to simple visual categories and 3-D SFM perception, with less affected ventral stream. Our results corroborate the existence of a medial dorsal pathway that provides the substrate for information rerouting and reorganization in the presence of lateral dorsal stream vulnerability. This interpretation is consistent with recent findings suggesting parallel routing of information in medial and lateral parts of dorsal stream.

Functional cooperation of of IL-1β and RGS4 in the brachial plexus avulsion mediated brain reorganization.

BackgroundsThere is considerable evidence that central nervous system is continuously modulated by activity, behavior and skill acquisition. This study is to examine the reorganization in cortical and subcortical regions in response to brachial plexus avulsion.MethodsAdult C57BL/6 mice were divided into four groups: control, 1, 3 and 6 month of brachial plexus avulsion. IL-1β, IL-6 and RGS4 expression in cortex, brainstem and spinal cord were detected by BiostarM-140 s microarray and real-time PCR. RGS4 subcellular distribution and modulation were further analyzed by primary neuron culture and Western Blot.ResultsAfter 1, 3 and 6 months of brachial plexus avulsion, 49 (0 up, 49 down), 29 (17 up, 12 down), 13 (9 up, 4 down) genes in cerebral cortex, 40 (8 up, 32 down), 11 (7 up, 4 down), 137 (63 up, 74 down) in brainstem, 27 (14 up, 13 down), 33 (18 up, 15 down), 60 (29 up, 31 down) in spinal cord were identified. Among the regulated gene, IL-1β and IL-6 were sustainable enhanced in brain stem, while PKACβ and RGS4 were up-regulated throughout cerebral cortex, brainstem and spinal cord in 3 and 6 month of nerve injury. Intriguingly, subcellular distribution of RGS4 in above three regions was dependent on the functional correlation of PKA and IL-1β.ConclusionData herein indicated that brachial plexus avulsion could efficiently initiate and perpetuate the brain reorganization. Network involved IL-1β and RGS4 signaling might implicate in the re-establish and strengthening of the local circuits at the cortical and subcortical levels.

Local awakening: Regional reorganizations of brain oscillations after sleep

Brain functions express rhythmic fluctuations accompanied by sleep and wakefulness each day, but how sleep regulates brain rhythms remains unclear. Following the dose-dependent local sleep concept, two succeeding questions emerge: (1) is the sleep regulation a network-specific process; and (2) is the awakening state dependent on the previous sleep stages? To answer the questions, we conducted simultaneous EEG and fMRI recordings over 22 healthy male participants, along pre-sleep, nocturnal sleep and awakening. Using paired comparisons between awakening and pre-sleep conditions, three scenarios of the regional specificity were demonstrated on awakening: (1) the default-mode and hippocampal networks maintained similar connectivity and spectral power; (2) the sensorimotor network presented reduced connectivity and spectral power; and (3) the thalamus demonstrated substantially enhanced connectivity to the neo-cortex with decreased spectral power. With regard to the stage effect, the deep sleep group had significant changes in both functional connectivity and spectral power on awakening, whereas the indices of light sleep group remained relatively quiescent after sleep. The phenomena implied that slow-wave sleep could be key to rebooting the BOLD fluctuations after sleep. In conclusion, the regional specificity and the stage effect were verified in support of the local awakening concept, indicating that sleep regulation leads to the reorganization of brain networks upon awakening.

Combining resources, combining forces: regionalizing hospital library services in a large statewide health system.

After a reduction in full-time equivalents, 2 libraries in large teaching hospitals and 2 libraries in small community hospitals in a western US statewide health system saw opportunity for expansion through a regional reorganization. Despite a loss of 2/3 of the professional staff and a budgetary decrease of 27% over the previous 3 years, the libraries were able to grow business, usage, awareness, and collections through organizational innovation and improved efficiency. This paper describes the experience--including process, challenges, and lessons learned--of an organizational shift to regionalized services, collections, and staffing. Insights from this process may help similar organizations going through restructuring.

Fools Rush In: The Case Against Radical Water and Wastewater Restructuring in Regional New South Wales

In its 2008 Final Report, the Independent Inquiry into Secure and Sustainable Urban Water Supply and Sewerage Services for Non-Metropolitan New South Wales (NSW) recommended that the (then) 106 local water utilities (LWUs) be restructured through regional aggregation into 32 regional entities. This recommendation has been echoed without any further analysis or substantiation in Infrastructure NSW's (2012) First Things First: State Infrastructure Strategy, 2012–2032, with its call for the present 105 entities to be radically reduced to “around 30 authorities.” This paper demonstrates that the case for drastic regional water reorganization along in these lines in country NSW has been fatally weakened by (a) the recent strong performance of NSW LWUs as made plain in the 2010–11 NSW Water Supply and Sewerage Performance Monitoring Report and (b) the failure of the Tasmanian water restructuring strategy on which much of the Independent Inquiry's restructuring model had been based.

Invasive neurostimulation in stroke rehabilitation.

The last decade has seen a growing interest in adjuvant treatments that synergistically influence mechanisms underlying rehabilitation of paretic upper limb in stroke. One such approach is invasive neurostimulation of spared cortices at the periphery of a lesion. Studies in animals have shown that during training of paretic limb, adjuvant stimulation targeting the peri-infarct circuitry enhances mechanisms of its reorganization, generating functional advantage. Success of early animal studies and clinical reports, however, failed to translate to a phase III clinical trial. As lesions in humans are diffuse, unlike many animal models, peri-infarct circuitry may not be a feasible, or consistent target across most. Instead, alternate mechanisms, such as changing transcallosal inhibition between hemispheres, or reorganization of other viable regions in motor control, may hold greater potential. Here, we review comprehensive mechanisms of clinical recovery and factors that govern which mechanism(s) become operative when. We suggest novel approaches that take into account a patient's initial clinical-functional state, and findings from neuroimaging and neurophysiology to guide to their most suitable mechanism for ideal targeting. Further, we suggest new localization schemes, and bypass strategies that indirectly target peri-lesional circuitry, and methods that serve to counter technical and theoretical challenge in identifying and stimulating such targets at the periphery of infarcts in humans. Last, we describe how stimulation may modulate mechanisms differentially across varying phases of recovery- a temporal effect that may explain missed advantage in clinical trials and help plan for the next stage. With information presented here, future trials would effectively be able to target patient's specific mechanism(s) with invasive (or noninvasive) neurostimulation for the greatest, most consistent benefit.

Functional Reorganization of Motor and Limbic Circuits after Exercise Training in a Rat Model of Bilateral Parkinsonism

Exercise training is widely used for neurorehabilitation of Parkinson’s disease (PD). However, little is known about the functional reorganization of the injured brain after long-term aerobic exercise. We examined the effects of 4 weeks of forced running wheel exercise in a rat model of dopaminergic deafferentation (bilateral, dorsal striatal 6-hydroxydopamine lesions). One week after training, cerebral perfusion was mapped during treadmill walking or at rest using [14C]-iodoantipyrine autoradiography. Regional cerebral blood flow-related tissue radioactivity (rCBF) was analyzed in three-dimensionally reconstructed brains by statistical parametric mapping. In non-exercised rats, lesions resulted in persistent motor deficits. Compared to sham-lesioned rats, lesioned rats showed altered functional brain activation during walking, including: 1. hypoactivation of the striatum and motor cortex; 2. hyperactivation of non-lesioned areas in the basal ganglia-thalamocortical circuit; 3. functional recruitment of the red nucleus, superior colliculus and somatosensory cortex; 4. hyperactivation of the ventrolateral thalamus, cerebellar vermis and deep nuclei, suggesting recruitment of the cerebellar-thalamocortical circuit; 5. hyperactivation of limbic areas (amygdala, hippocampus, ventral striatum, septum, raphe, insula). These findings show remarkable similarities to imaging findings reported in PD patients. Exercise progressively improved motor deficits in lesioned rats, while increasing activation in dorsal striatum and rostral secondary motor cortex, attenuating a hyperemia of the zona incerta and eliciting a functional reorganization of regions participating in the cerebellar-thalamocortical circuit. Both lesions and exercise increased activation in mesolimbic areas (amygdala, hippocampus, ventral striatum, laterodorsal tegmental n., ventral pallidum), as well as in related paralimbic regions (septum, raphe, insula). Exercise, but not lesioning, resulted in decreases in rCBF in the medial prefrontal cortex (cingulate, prelimbic, infralimbic). Our results in this PD rat model uniquely highlight the breadth of functional reorganizations in motor and limbic circuits following lesion and long-term, aerobic exercise, and provide a framework for understanding the neural substrates underlying exercise-based neurorehabilitation.

Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

Abstract. The Indian Ocean Dipole (IOD) and the El Niño/Southern Oscillation (ENSO) are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. A negative influence of IOD on chlorophyll concentrations is shown in a region around the southern tip of India in fall. IOD also depresses depth-integrated chlorophyll in the 5–10° S thermocline ridge region, yet the signal is negligible in surface chlorophyll. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Yet unlike most other regions examined, the combined explanatory power of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is relatively low in this region, suggestive that other drivers are important there. We show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. Our results suggest that ENSO and IOD cause significant and predictable regional re-organisation of chlorophyll via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon budgets.

Evidence of structural order recovery in LDPE based copolymers prepared by gamma irradiation

PE-g-HEMA films prepared by the mutual gamma irradiation method were prepared to be used as catalyst support in catalytic membrane reactors (CMR). These copolymeric films showed good structural stability, even the high grafted ones, with a consistent correlation between their grafting degree and crystallinity. However, it was observed that above a certain radiation dose threshold, the structural changes induced in polyethylene (PE) backbone do not depend only on the extend of poly(HEMA) graft but also in what seems to be the reorganization of the amorphous regions in the PE matrix. The recovery of some crystallinity (up to 8%) in the copolymeric films was attested by DSC data. FTIR analysis confirmed this observation, revealing a slight increase in intensity and definition of the characteristic peak indicator of high crystalline regions in PE. This process seems to result from a radiation protective effect on copolymers matrix carried out by grafted poly(HEMA) which give to PE the ability to recover some of the lost structural order.

Diffusion tensor imaging detects microstructural reorganization in the brain associated with chronic irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by recurring abdominal pain associated with alterations in bowel habits. We hypothesized that patients with chronic visceral pain associated with IBS may have microstructural differences in the brain compared with healthy control subjects (HCs), indicative of long-term neural reorganization of chronic pain pathways and regions associated with sensory integration. In the current study we performed population-based voxel-wise diffusion tensor imaging (DTI) comparisons and probabilistic tractography in a large sample of phenotyped patients with IBS (n=33) and in HCs (n=93). Patients had lower fractional anisotropy (FA) in thalamic regions, the basal ganglia (BG) and sensory/motor association/integration regions as well as higher FA in frontal lobe regions and the corpus callosum. In addition, patients had reduced mean diffusivity (MD) within the globus pallidus (GP) and higher MD in the thalamus, internal capsule, and coronal radiata projecting to sensory/motor regions, suggestive of differential changes in axon/dendritic density in these regions. Sex differences in FA and MD were also observed in the patients but not in HCs. Probabilistic tractography in patients confirmed a higher degree of connectivity between the thalamus and prefrontal cortex, as well as between the medial dorsal thalamic nuclei and anterior cingulate cortex, and a lower degree of connectivity between the GP and thalamus. Together, these results support the hypothesis that patients with chronically recurring visceral pain from IBS have long-term microstructural changes within the brain, particularly in regions associated with integration of sensory information and corticothalamic modulation.

Involvement of human topoisomerase II isoforms in HIV-1 reverse transcription

HIV-1 reverse transcription (RTn) involves synthesis of double strand DNA (dsDNA) from viral genomic RNA. Topoisomerase II (Topo II) alpha and beta maintains topological reorganization of dsDNA regions and catalytic inhibition of these isoforms repressed viral replicative cycle. Present study is aimed to understand the role of Topo II isoforms in HIV-1 early replication. Topo IIα and β showed differential expression in SupT1 cells and PBMCs during early hours of HIV-1 infection where Topo IIα expression increased after 4h, while Topo IIβ showed relatively higher expression at 1 and 4h. In Topo IIα and/or β down regulated cells, transcription of viral genes gag, pol and env as well as proviral DNA synthesis was abolished. In Topo IIα and/or β down regulated cells, strong stop DNA synthesis was unaffected while other downstream events of reverse transcription such as first strand transfer, full length minus strand synthesis, and second strand transfer were completely inhibited, which affects HIV-1 replication. Further, co-localization of Topo II isoforms with HIV-1 reverse transcriptase was observed in SupT1 cells and PBMCs by immunofluorescence. These results collectively suggest a role of Topo II isoforms during HIV-1 RTn probably by promoting the alignment of viral RNA–DNA hybrids.

System Consolidation of Spatial Memories in Mice: Effects of Enriched Environment

Environmental enrichment (EE) is known to enhance learning and memory. Declarative memories are thought to undergo a first rapid and local consolidation process, followed by a prolonged process of system consolidation, which consist in a time-dependent gradual reorganization of brain regions supporting remote memory storage and crucial for the formation of enduring memories. At present, it is not known whether EE can affect the process of declarative memory system consolidation. We characterized the time course of hippocampal and cortical activation following recall of progressively more remote spatial memories. Wild-type mice either exposed to EE for 40 days or left in standard environment were subjected to spatial learning in the Morris water maze and to the probe test 1, 10, 20, 30, and 50 days after learning. Following the probe test, regional expression of the inducible immediate early gene c-Fos was mapped by immunohistochemistry, as an indicator of neuronal activity. We found that activation of the medial prefrontal cortex (mPFC), suggested to have a privileged role in processing remote spatial memories, was evident at shorter time intervals after learning in EE mice; in addition, EE induced the progressive activation of a distributed cortical network not activated in non-EE mice. This suggests that EE not only accelerates the process of mPFC recruitment but also recruits additional cortical areas into the network supporting remote spatial memories.

Perfumers' expertise induces structural reorganization in olfactory brain regions

The human brain's ability to adapt to environmental changes is obvious in specific sensory domains of experts, and olfaction is one of the least investigated senses. As we have previously demonstrated that olfactory expertise is related to functional brain modifications, we investigated here whether olfactory expertise is also coupled with structural changes. We used voxel-based morphometry to compare the gray-matter volume in student and professional perfumers, as well as untrained control subjects, and accounted for all methodological improvements that have been recently developed to limit possible errors associated with image processing. In all perfumers, we detected an increase in gray-matter volume in the bilateral gyrus rectus/medial orbital gyrus (GR/MOG), an orbitofrontal area that surrounds the olfactory sulcus. In addition, gray-matter volume in the anterior PC and left GR/MOG was positively correlated with experience in professional perfumers. We concluded that the acute olfactory knowledge acquired through extensive olfactory training leads to the structural reorganization of olfactory brain areas.

Role of cortical reorganization on the effect of 5-HT pharmacotherapy for spinal cord injury

Cortical reorganization or expansion of the intact cortical regions into the deafferented cortex after complete spinal transection in neonatally spinalized rats was shown to be essential for increases in weight-supported stepping at adulthood. The novel somatotopic organization identified in these animals can be induced by exercise or spinal transplants that bridge the site of injury. However, the role of cortical reorganization in increased weight-supported (WS) stepping after pharmacotherapy is unknown. For the neonatally spinalized rat model, the 5-HT2C receptor agonist 1-(m-chlorophenyl)-piperazine hydrochloride (mCPP) increases the number of WS steps taken when administered to adult rats spinalized as neonates (mCPP+) though not all animals showed this effect (mCPP−). Since no differences in the behavior of the animals off-drug has been demonstrated, it is unclear why acute administration of 5-HT affects only a subset of animals. One possibility is that differences in cortical organization between mCPP+ and mCPP− may contribute to the differences in the functional effect of mCPP. To test this, we recorded from single neurons in the deafferented hindlimb sensorimotor cortex during passive sensory stimulation of the cutaneous surface of the forepaws and during active sensorimotor stimulation of the forepaws while the animals locomoted on a motorized treadmill. Our results show that neurons recorded from mCPP+ animals increased their responsiveness to both passive and active stimulation off-drug in comparison to neurons from mCPP− animals. These data suggest that differences in the cortical organization of mCPP+ compared to mCPP− animals may be at least partially responsible for the effect of a 5-HT2C receptor agonist on functional outcome.

Pain and persistent occlusal awareness: What should dentists do?

Pain and persistent occlusal awareness: What should dentists do?

Age of onset of marijuana use impacts inhibitory processing

Difficulties in the ability to successfully inhibit impulsive behaviors have been reported in marijuana (MJ) smokers, yet few studies have made direct comparisons between early (prior to age 16) and late (age 16 or later) onset MJ smokers, specifically during behavioral inhibition tasks. The current study utilized the Multi-Source Interference Task (MSIT) during functional magnetic resonance imaging (fMRI) in chronic, heavy MJ smokers and healthy non-MJ smoking controls which revealed a more focal pattern of anterior cingulate activity in controls relative to smokers. Early onset smokers had more focal activation but tended to make more errors of commission relative to late onset smokers, suggesting a possible neural adaptation despite difficulty with behavioral inhibition. Further investigation is warranted, as early exposure to MJ may result in reorganization of critical brain regions.