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Unhealthy alcohol use, which encompasses heavy episodic drinking to alcohol use disorder, has been identified as a modifiable barrier to optimal HIV care continuum outcomes. Despite the demonstrated efficacy of couples-based interventions for addressing unhealthy alcohol use, there are no existing couples-based alcohol interventions designed specifically for people living with HIV. This study presents the development and refinement of a three-session couples-based motivational intervention (ReACH2Gether) to address unhealthy alcohol use among a sample of 17 sexual minority men living with HIV and their partners living in the United States. To increase potential population reach, the intervention was delivered entirely remotely. Throughout an original and a modified version, results indicated that the ReACH2Gether intervention was acceptable and there were no reports of intimate partner violence or adverse events. Session engagement and retention were high. In pre-post-test analyses, the ReACH2Gether intervention showed trends in reducing Alcohol Use Disorder Identification Test scores and increasing relationship-promoting dynamics, such as positive support behaviors and goal congruence around alcohol use. Results support the need for continued work to evaluate the ReACH2Gether intervention.

Deep brain nuclei are integral components of large-scale circuits mediating important cognitive and sensorimotor functions. However, because they fall outside the domain of conventional non-invasive neuromodulatory techniques, their study has been primarily based on neuropsychological models, limiting the ability to fully characterize their role and to develop interventions in cases where they are damaged. To address this gap, we used the emerging technology of non-invasive low-intensity focused ultrasound (LIFU) to directly modulate left lateralized basal ganglia structures in healthy volunteers. During sonication, we observed local and distal decreases in blood oxygenation level dependent (BOLD) signal in the targeted left globus pallidus (GP) and in large-scale cortical networks. We also observed a generalized decrease in relative perfusion throughout the cerebrum following sonication. These results show, for the first time using functional MRI data, the ability to modulate deep-brain nuclei using LIFU while measuring its local and global consequences, opening the door for future applications of subcortical LIFU.

BackgroundTraumatic brain injury (TBI) causes early seizures and is the leading cause of post-traumatic epilepsy. We prospectively assessed structural imaging biomarkers differentiating patients who develop seizures secondary to TBI from patients who do not.DesignMulticentre prospective cohort study starting in 2018. Imaging data are acquired around day 14 post-injury, detection of seizure events occurred early (within 1 week) and late (up to 90 days post-TBI).ResultsFrom a sample of 96 patients surviving moderate-to-severe TBI, we performed shape analysis of local volume deficits in subcortical areas (analysable sample: 57 patients; 35 no seizure, 14 early, 8 late) and cortical ribbon thinning (analysable sample: 46 patients; 29 no seizure, 10 early, 7 late). Right hippocampal volume deficit and inferior temporal cortex thinning demonstrated a significant effect across groups. Additionally, the degree of left frontal and temporal pole thinning, and clinical score at the time of the MRI, could differentiate patients experiencing early seizures from patients not experiencing them with 89% accuracy.Conclusions and relevanceAlthough this is an initial report, these data show that specific areas of localised volume deficit, as visible on routine imaging data, are associated with the emergence of seizures after TBI.

ObjectiveTo understand how, biologically, the acute event of traumatic brain injury gives rise to a long-term disease, we address the relationship between evolving cortical and subcortical brain damage and measures of functional outcome and cognitive functioning at 6 months after injury.MethodsFor this longitudinal analysis, clinical and MRI data were collected in a tertiary neurointensive care setting in a continuous sample of 157 patients surviving moderate to severe traumatic brain injury between 2000 and 2018. For each patient, we collected T1- and T2-weighted MRI data acutely and at the 6-month follow-up, as well as acute measures of injury severity (Glasgow Coma Scale), follow-up measures of functional impairment (Glasgow Outcome Scale-extended), and, in a subset of patients, neuropsychological measures of attention, executive functions, and episodic memory.ResultsIn the final cohort of 113 subcortical and 92 cortical datasets that survived (blind) quality control, extensive atrophy was observed over the first 6 months after injury across the brain. However, only atrophy within subcortical regions, particularly in the left thalamus, was associated with functional outcome and neuropsychological measures of attention, executive functions, and episodic memory. Furthermore, when brought together in an analytical model, longitudinal brain measurements could distinguish good from bad outcome with 90% accuracy, whereas acute brain and clinical measurements alone could achieve only 20% accuracy.ConclusionDespite great injury heterogeneity, secondary thalamic pathology is a measurable minimum common denominator mechanism directly relating biology to clinical measures of outcome and cognitive functioning, potentially linking the acute event and the longer-term disease of traumatic brain injury.

Cerebral acidosis is a consequence of secondary injury mechanisms following traumatic brain injury (TBI), including excitotoxicity and ischemia, with potentially significant clinical implications. However, there remains an unmet clinical need for technology for non-invasive, high resolution pH imaging of human TBI for studying metabolic changes following injury. The current study examined 17 patients with TBI and 20 healthy controls using amine chemical exchange saturation transfer echoplanar imaging (CEST EPI), a novel pH-weighted molecular MR imaging technique, on a clinical 3T MR scanner. Results showed significantly elevated pH-weighted image contrast (MTRasym at 3 ppm) in areas of T2 hyperintensity or edema (P

Cerebral acidosis is a consequence of secondary injury mechanisms following traumatic brain injury (TBI), including excitotoxicity and ischemia, with potentially significant clinical implications. However, there remains an unmet clinical need for technology for non-invasive, high resolution pH imaging of human TBI for studying metabolic changes following injury. The current study examined 17 patients with TBI and 20 healthy controls using amine chemical exchange saturation transfer echoplanar imaging (CEST EPI), a novel pH-weighted molecular MR imaging technique, on a clinical 3T MR scanner. Results showed significantly elevated pH-weighted image contrast (MTRasym at 3 ppm) in areas of T2 hyperintensity or edema (P

In recent years, neuroimaging methods have been used to investigate how the human mind carries out deductive reasoning. According to some, the neural substrate of language is integral to deductive reasoning. According to others, deductive reasoning is supported by a language-independent distributed network including left frontopolar and frontomedial cortices. However, it has been suggested that activity in these frontal regions might instead reflect non-deductive factors such as working memory load and general cognitive difficulty. To address this issue, 20 healthy volunteers participated in an fMRI experiment in which they evaluated matched simple and complex deductive and non-deductive arguments in a 2 × 2 design. The contrast of complex versus simple deductive trials resulted in a pattern of activation closely matching previous work, including frontopolar and frontomedial "core" areas of deduction as well as other "cognitive support" areas in frontoparietal cortices. Conversely, the contrast of complex and simple non-deductive trials resulted in a pattern of activation that does not include any of the aforementioned "core" areas. Direct comparison of the load effect across deductive and non-deductive trials further supports the view that activity in the regions previously interpreted as "core" to deductive reasoning cannot merely reflect non-deductive load, but instead might reflect processes specific to the deductive calculus. Finally, consistent with previous reports, the classical language areas in left inferior frontal gyrus and posterior temporal cortex do not appear to participate in deductive inference beyond their role in encoding stimuli presented in linguistic format.

Sleep suffers during adolescence and is related to academic, emotional and social behaviors. How this normative change relates to ongoing brain development remains unresolved. The default mode network (DMN), a large-scale brain network important for complex cognition and socioemotional processing, undergoes intra-network integration and inter-network segregation during adolescence. Using resting state functional connectivity and actigraphy over 14 days, we examined correlates of naturalistic individual differences in sleep duration and quality in the DMN at rest in 45 human adolescents (ages 14-18). Variation in sleep quality, but not duration, was related to weaker intrinsic DMN connectivity, such that those with worse quality sleep evinced weaker intra-network connectivity at rest. These novel findings suggest sleep quality, a relatively unexplored sleep index, is related to adolescent brain function in a network that contributes to behavioral maturation and undergoes development during adolescence.

Sleep suffers during adolescence and is related to academic, emotional and social behaviors. How this normative change relates to ongoing brain development remains unresolved. The default mode network (DMN), a large-scale brain network important for complex cognition and socioemotional processing, undergoes intra-network integration and inter-network segregation during adolescence. Using resting state functional connectivity and actigraphy over 14 days, we examined correlates of naturalistic individual differences in sleep duration and quality in the DMN at rest in 45 human adolescents (ages 14-18). Variation in sleep quality, but not duration, was related to weaker intrinsic DMN connectivity, such that those with worse quality sleep evinced weaker intra-network connectivity at rest. These novel findings suggest sleep quality, a relatively unexplored sleep index, is related to adolescent brain function in a network that contributes to behavioral maturation and undergoes development during adolescence.

Motivational interviewing (MI) is often incorporated into screening, brief intervention, and referral to treatment (SBIRT) interventions in critical care settings to address alcohol and other drug use. However, cognitive status has been linked to differential response to MI sessions in emergency department (ED) settings. The current study examined one possible explanation for this differential response: whether higher versus lower mental status impacts patient response to clinician statements during MI sessions conducted in an ED. Participants were 126 patients receiving an MI-based single-session alcohol brief intervention, and 13 therapists who provided treatment. Participants completed a mental status exam (MSE) as part of the screening process. Intervention sessions were audio-taped, and transcribed and coded using the Motivational Interviewing Skills Code (MISC 2.0; Miller, Moyers, Ernst, & Amrhein, 2003). The MISC 2.0 coded therapist behaviors that are related to the use of motivational interviewing, and patient language reflecting movement toward (change talk) or away from (sustain talk) changing personal alcohol use. Overall, patients responded in a similar manner to therapist MI behaviors regardless of high versus low level of mental functioning at the time of the intervention. Group differences emerged on patient response to only three specific therapist skills: giving information, open questions, and complex reflection. Thus, the differential effects of SBIRT in critical care settings do not appear to be a result of differences in the therapist and patient communication process.

Motivational interviewing (MI) is often incorporated into screening, brief intervention, and referral to treatment (SBIRT) interventions in critical care settings to address alcohol and other drug use. However, cognitive status has been linked to differential response to MI sessions in emergency department (ED) settings. The current study examined one possible explanation for this differential response: whether higher versus lower mental status impacts patient response to clinician statements during MI sessions conducted in an ED. Participants were 126 patients receiving an MI-based single-session alcohol brief intervention, and 13 therapists who provided treatment. Participants completed a mental status exam (MSE) as part of the screening process. Intervention sessions were audio-taped, and transcribed and coded using the Motivational Interviewing Skills Code (MISC 2.0; Miller, Moyers, Ernst, & Amrhein, 2003). The MISC 2.0 coded therapist behaviors that are related to the use of motivational interviewing, and patient language reflecting movement toward (change talk) or away from (sustain talk) changing personal alcohol use. Overall, patients responded in a similar manner to therapist MI behaviors regardless of high versus low level of mental functioning at the time of the intervention. Group differences emerged on patient response to only three specific therapist skills: giving information, open questions, and complex reflection. Thus, the differential effects of SBIRT in critical care settings do not appear to be a result of differences in the therapist and patient communication process.

Previous studies have suggested that disorders of consciousness (DOC) after severe brain injury may result from disconnections of the thalamo-cortical system. However, thalamo-cortical connectivity differences between vegetative state (VS), minimally conscious state minus (MCS-, i.e., low-level behavior such as visual pursuit), and minimally conscious state plus (MCS+, i.e., high-level behavior such as language processing) remain unclear. Probabilistic tractography in a sample of 25 DOC patients was employed to assess whether structural connectivity in various thalamo-cortical circuits could differentiate between VS, MCS-, and MCS+ patients. First, the thalamus was individually segmented into seven clusters based on patterns of cortical connectivity and tested for univariate differences across groups. Second, reconstructed whole-brain thalamic tracks were used as features in a multivariate searchlight analysis to identify regions along the tracks that were most informative in distinguishing among groups. At the univariate level, it was found that VS patients displayed reduced connectivity in most thalamo-cortical circuits of interest, including frontal, temporal, and sensorimotor connections, as compared with MCS+, but showed more pulvinar-occipital connections when compared with MCS-. Moreover, MCS- exhibited significantly less thalamo-premotor and thalamo-temporal connectivity than MCS+. At the multivariate level, it was found that thalamic tracks reaching frontal, parietal, and sensorimotor regions, could discriminate, up to 100% accuracy, across each pairwise group comparison. Together, these findings highlight the role of thalamo-cortical connections in patients' behavioral profile and level of consciousness. Diffusion tensor imaging combined with machine learning algorithms could thus potentially facilitate diagnostic distinctions in DOC and shed light on the neural correlates of consciousness. Hum Brain Mapp 38:431-443, 2017. © 2016 Wiley Periodicals, Inc.

Humans have developed multiple symbolic representations for numbers, including natural numbers (positive integers) as well as rational numbers (both fractions and decimals). Despite a considerable body of behavioral and neuroimaging research, it is currently unknown whether different notations map onto a single, fully abstract, magnitude code, or whether separate representations exist for specific number types (e.g., natural versus rational) or number representations (e.g., base-10 versus fractions). We address this question by comparing brain metabolic response during a magnitude comparison task involving (on different trials) integers, decimals, and fractions. Univariate and multivariate analyses revealed that the strength and pattern of activation for fractions differed systematically, within the intraparietal sulcus, from that of both decimals and integers, while the latter two number representations appeared virtually indistinguishable. These results demonstrate that the two major notations formats for rational numbers, fractions and decimals, evoke distinct neural representations of magnitude, with decimals representations being more closely linked to those of integers than to those of magnitude-equivalent fractions. Our findings thus suggest that number representation (base-10 versus fractions) is an important organizational principle for the neural substrate underlying mathematical cognition.

Humans have developed multiple symbolic representations for numbers, including natural numbers (positive integers) as well as rational numbers (both fractions and decimals). Despite a considerable body of behavioral and neuroimaging research, it is currently unknown whether different notations map onto a single, fully abstract, magnitude code, or whether separate representations exist for specific number types (e.g., natural versus rational) or number representations (e.g., base-10 versus fractions). We address this question by comparing brain metabolic response during a magnitude comparison task involving (on different trials) integers, decimals, and fractions. Univariate and multivariate analyses revealed that the strength and pattern of activation for fractions differed systematically, within the intraparietal sulcus, from that of both decimals and integers, while the latter two number representations appeared virtually indistinguishable. These results demonstrate that the two major notations formats for rational numbers, fractions and decimals, evoke distinct neural representations of magnitude, with decimals representations being more closely linked to those of integers than to those of magnitude-equivalent fractions. Our findings thus suggest that number representation (base-10 versus fractions) is an important organizational principle for the neural substrate underlying mathematical cognition.

ObjectiveStudents referred to school administration for alcohol policies violations currently receive a wide variety of interventions. This study examined predictors of response to 2 interventions delivered to mandated college students (N = 598) using a stepped care approach incorporating a peer-delivered 15-min brief advice (BA) session (Step 1) and a 60- to 90-min brief motivational intervention (BMI) delivered by trained interventionists (Step 2).MethodAnalyses were completed in 2 stages. First, 3 types of variables (screening variables, alcohol-related cognitions, mandated student profile) were examined in a logistic regression model as putative predictors of lower risk drinking (defined as 3 or fewer heavy episodic drinking [HED] episodes and/or 4 or fewer alcohol-related consequences in the past month) 6 weeks following the BA session. Second, we used generalized estimating equations to examine putative moderators of BMI effects on HED and peak blood alcohol content compared with assessment only (AO) control over the 3-, 6-, and 9-month follow-ups.ResultsParticipants reporting lower scores on the Alcohol Use Disorders Identification Test, more benefits to changing alcohol use, and those who fit the "Bad Incident" profile at baseline were more likely to report lower risk drinking 6 weeks after the BA session. Moderation analyses revealed that Bad Incident students who received the BMI reported more HED at 9-month follow-up than those who received AO.ConclusionCurrent alcohol use as well as personal reaction to the referral event may have clinical utility in identifying which mandated students benefit from treatments of varying content and intensity.

BackgroundFew prospective studies have evaluated theory-driven approaches to the implementation of evidence-based opioid treatment. This study compared the effectiveness of an implementation model (Science to Service Laboratory; SSL) to training as usual (TAU) in promoting the adoption of contingency management across a multisite opioid addiction treatment program. We also examined whether the SSL affected putative mediators of contingency management adoption (perceived innovation characteristics and organizational readiness to change).MethodsSixty treatment providers (39 SSL, 21 TAU) from 15 geographically diverse satellite clinics (7 SSL, 8 TAU) participated in the 12-month study. Both conditions received didactic contingency management training and those in the predetermined experimental region received 9 months of SSL-enhanced training. Contingency management adoption was monitored biweekly, whereas putative mediators were measured at baseline, 3 months, and 12 months.ResultsRelative to providers in the TAU region, treatment providers in the SSL region had comparable likelihood of contingency management adoption in the first 20 weeks of the study, and then significantly higher likelihood of adoption (odds ratios = 2.4-13.5) for the remainder of the study. SSL providers also reported higher levels of one perceived innovation characteristic (Observability) and one aspect of organizational readiness to change (Adequacy of Training Resources), although there was no evidence that the SSL affected these putative mediators over time.ConclusionsResults of this study indicate that a fully powered randomized trial of the SSL is warranted. Considerations for a future evaluation are discussed.

Stepped care approaches for mandated college students provide individual brief motivational interventions (BMI) only for individuals who do not respond to an initial, low-intensity level of treatment such as Brief Advice (BA). However, how BMIs facilitate change in this higher-risk group of mandated students remains unclear. Perceived descriptive norms and alcohol-related expectancies are the most commonly examined mediators of BMI efficacy but have yet to be examined in the context of stepped care. Participants were mandated college students (N = 598) participating in a stepped care trial in which mandated students first received BA. Those who reported continued risky drinking 6 weeks following a BA session were randomized to either a single-session BMI (N = 163) or an assessment-only comparison condition (AO; N = 165). BMI participants reduced alcohol-related problems at the 9 month follow up significantly more than AO participants. Multiple mediation analyses using bootstrapping techniques examined whether perceived descriptive norms and alcohol-related expectancies mediated the observed outcomes. Reductions in perceptions of average student drinking (B = -.24; 95% CI [-.61, -.04]) and negative expectancies (B = -.13; 95% CI [-.38, -.01]) mediated the BMI effects. Furthermore, perceived average student norms were reduced after the BMI to levels approximating those of students who had exhibited lower risk drinking following the BA session. Findings highlight the utility of addressing perceived norms and expectancies in BMIs, especially for students who have not responded to less intensive prevention efforts.

Substance use among adolescents with one or more psychiatric disorders is a significant public health concern. In this study, 151 psychiatrically hospitalized adolescents, ages 13-17 with comorbid psychiatric and substance use disorders, were randomized to a two-session Motivational Interviewing intervention to reduce substance use plus treatment as usual (MI) vs. treatment as usual only (TAU). Results indicated that the MI group had a longer latency to first use of any substance following hospital discharge relative to TAU (36 days versus 11 days). Adolescents who received MI also reported less total use of substances and less use of marijuana during the first 6 months post-discharge, although this effect was not significant across 12 months. Finally, MI was associated with a significant reduction in rule-breaking behaviors at 6-month follow-up. Future directions are discussed, including means of extending effects beyond 6 months and dissemination of the intervention to community-based settings.

ObjectiveWe employed functional MRI (fMRI) to assess whether (1) patients with disorders of consciousness (DOC) retain the ability to willfully engage in top-down processing and (2) what neurophysiologic factors distinguish patients who can demonstrate this ability from patients who cannot.MethodsSixteen volunteers, 8 patients in vegetative state (VS), 16 minimally conscious patients (MCS), and 4 exit from MCS (eMCS) patients were enrolled in a prospective cross-sectional fMRI study. Participants performed a target detection task in which they counted the number of times a (changing) target word was presented amidst a set of distractors.ResultsThree of 8 patients diagnosed as being in a VS exhibited significant activations in response to the task, thereby demonstrating a state of consciousness. Differential activations across tasks were also observed in 6 MCS patients and 1 eMCS patient. A psycho-physiologic interaction analysis revealed that the main factor distinguishing patients who responded to the task from those who did not was a greater connectivity between the anterior section of thalamus and prefrontal cortex.ConclusionsIn our sample of patients, the dissociation between overt behavior observable in clinical assessments and residual cognitive faculties is prevalent among DOC patients (37%). A substantial number of patients, including some diagnosed with VS, can demonstrate willful engagement in top-down cognition. While neuroimaging data are not the same as observable behavior, this suggests that the mental status of some VS patients exceeds what can be appreciated clinically. Furthermore, thalamo-frontal circuits might be crucial to sustaining top-down functions.

Theoretical advances in the science of consciousness have proposed that it is concomitant with balanced cortical integration and differentiation, enabled by efficient networks of information transfer across multiple scales. Here, we apply graph theory to compare key signatures of such networks in high-density electroencephalographic data from 32 patients with chronic disorders of consciousness, against normative data from healthy controls. Based on connectivity within canonical frequency bands, we found that patient networks had reduced local and global efficiency, and fewer hubs in the alpha band. We devised a novel topographical metric, termed modular span, which showed that the alpha network modules in patients were also spatially circumscribed, lacking the structured long-distance interactions commonly observed in the healthy controls. Importantly however, these differences between graph-theoretic metrics were partially reversed in delta and theta band networks, which were also significantly more similar to each other in patients than controls. Going further, we found that metrics of alpha network efficiency also correlated with the degree of behavioural awareness. Intriguingly, some patients in behaviourally unresponsive vegetative states who demonstrated evidence of covert awareness with functional neuroimaging stood out from this trend: they had alpha networks that were remarkably well preserved and similar to those observed in the controls. Taken together, our findings inform current understanding of disorders of consciousness by highlighting the distinctive brain networks that characterise them. In the significant minority of vegetative patients who follow commands in neuroimaging tests, they point to putative network mechanisms that could support cognitive function and consciousness despite profound behavioural impairment.

ObjectiveAcross the United States, tens of thousands of college students are mandated to receive an alcohol intervention following an alcohol policy violation. Telephone interventions may be an efficient method to provide mandated students with an intervention, especially when they are away from campus during summer vacation. However, little is known about the utility of telephone-delivered brief motivational interventions.MethodParticipants in the study (N=57) were college students mandated to attend an alcohol program following a campus-based alcohol citation. Participants were randomized to a brief motivational phone intervention (pBMI) (n=36) or assessment only (n=21). Ten participants (27.8%) randomized to the pBMI did not complete the intervention. Follow-up assessments were conducted 3, 6, and 9 months post-intervention.ResultsResults indicated the pBMI significantly reduced the number of alcohol-related problems compared to the assessment-only group. Participants who did not complete the pBMI appeared to be lighter drinkers at baseline and randomization, suggesting the presence of alternate influences on alcohol-related problems.ConclusionPhone BMIs may be an efficient and cost-effective method to reduce harms associated with alcohol use by heavy-drinking mandated students during the summer months.

Theoretical models of alcoholism emphasize the acute reinforcing properties of alcohol as chief determinants of drinking, and animal research suggests adolescents are uniquely sensitive to these effects. Human studies of these phenomena, however, are virtually nonexistent. We used ecological momentary assessment methods to capture adolescents' subjective responses to alcohol in real time in their natural environments. Adolescent participants were 22 problem drinkers, ages 15 to 19 years (M = 18.3, SD = 0.09; 55% female; 55% alcohol dependent). Participants consumed alcohol on 38% of days during a 1-week monitoring period, with an average of 5 drinks per occasion. Momentary data revealed that adolescents experience decreased stimulation and increased sedation and "high" across the ascending limb of the blood alcohol curve. Notably, greater craving predicted higher volumes of subsequent alcohol consumption during the episode, whereas greater "high" attenuated use. To test for developmental differences in these effects, we pooled these data with data from a similarly ascertained sample of 36 adult heavy drinkers, ages 24 to 64 years (M = 38.1, SD = 11.8; 50% female; 61% alcohol dependent). Adolescents were more sensitive to the stimulant effects of alcohol than adults. This study provides novel data on how adolescent problem drinkers experience alcohol in their natural contexts and illustrates how these effects, which appear to differ from adult problem drinkers, confer liability for future drinking.

Theoretical advances in the science of consciousness have proposed that it is concomitant with balanced cortical integration and differentiation, enabled by efficient networks of information transfer across multiple scales. Here, we apply graph theory to compare key signatures of such networks in high-density electroencephalographic data from 32 patients with chronic disorders of consciousness, against normative data from healthy controls. Based on connectivity within canonical frequency bands, we found that patient networks had reduced local and global efficiency, and fewer hubs in the alpha band. We devised a novel topographical metric, termed modular span, which showed that the alpha network modules in patients were also spatially circumscribed, lacking the structured long-distance interactions commonly observed in the healthy controls. Importantly however, these differences between graph-theoretic metrics were partially reversed in delta and theta band networks, which were also significantly more similar to each other in patients than controls. Going further, we found that metrics of alpha network efficiency also correlated with the degree of behavioural awareness. Intriguingly, some patients in behaviourally unresponsive vegetative states who demonstrated evidence of covert awareness with functional neuroimaging stood out from this trend: they had alpha networks that were remarkably well preserved and similar to those observed in the controls. Taken together, our findings inform current understanding of disorders of consciousness by highlighting the distinctive brain networks that characterise them. In the significant minority of vegetative patients who follow commands in neuroimaging tests, they point to putative network mechanisms that could support cognitive function and consciousness despite profound behavioural impairment.

Whether unique to humans or not, consciousness is a central aspect of our experience of the world. The neural fingerprint of this experience, however, remains one of the least understood aspects of the human brain. In this paper we employ graph-theoretic measures and support vector machine classification to assess, in 12 healthy volunteers, the dynamic reconfiguration of functional connectivity during wakefulness, propofol-induced sedation and loss of consciousness, and the recovery of wakefulness. Our main findings, based on resting-state fMRI, are three-fold. First, we find that propofol-induced anesthesia does not bear differently on long-range versus short-range connections. Second, our multi-stage design dissociated an initial phase of thalamo-cortical and cortico-cortical hyperconnectivity, present during sedation, from a phase of cortico-cortical hypoconnectivity, apparent during loss of consciousness. Finally, we show that while clustering is increased during loss of consciousness, as recently suggested, it also remains significantly elevated during wakefulness recovery. Conversely, the characteristic path length of brain networks (i.e., the average functional distance between any two regions of the brain) appears significantly increased only during loss of consciousness, marking a decrease of global information-processing efficiency uniquely associated with unconsciousness. These findings suggest that propofol-induced loss of consciousness is mainly tied to cortico-cortical and not thalamo-cortical mechanisms, and that decreased efficiency of information flow is the main feature differentiating the conscious from the unconscious brain.

Whether unique to humans or not, consciousness is a central aspect of our experience of the world. The neural fingerprint of this experience, however, remains one of the least understood aspects of the human brain. In this paper we employ graph-theoretic measures and support vector machine classification to assess, in 12 healthy volunteers, the dynamic reconfiguration of functional connectivity during wakefulness, propofol-induced sedation and loss of consciousness, and the recovery of wakefulness. Our main findings, based on resting-state fMRI, are three-fold. First, we find that propofol-induced anesthesia does not bear differently on long-range versus short-range connections. Second, our multi-stage design dissociated an initial phase of thalamo-cortical and cortico-cortical hyperconnectivity, present during sedation, from a phase of cortico-cortical hypoconnectivity, apparent during loss of consciousness. Finally, we show that while clustering is increased during loss of consciousness, as recently suggested, it also remains significantly elevated during wakefulness recovery. Conversely, the characteristic path length of brain networks (i.e., the average functional distance between any two regions of the brain) appears significantly increased only during loss of consciousness, marking a decrease of global information-processing efficiency uniquely associated with unconsciousness. These findings suggest that propofol-induced loss of consciousness is mainly tied to cortico-cortical and not thalamo-cortical mechanisms, and that decreased efficiency of information flow is the main feature differentiating the conscious from the unconscious brain.