Despite mounting reports about the negative effects of chronic occupational stress on cognitive a... more Despite mounting reports about the negative effects of chronic occupational stress on cognitive and emotional functions, the underlying mechanisms are unknown. Recent findings from structural MRI raise the question whether this condition could be associated with a functional uncoupling of the limbic networks and an impaired modulation of emotional stress. To address this, 40 subjects suffering from burnout symptoms attributed to chronic occupational stress and 70 controls were investigated using resting state functional MRI. The participants' ability to up- regulate, down-regulate, and maintain emotion was evaluated by recording their acoustic startle response while viewing neutral and negatively loaded images. Functional connectivity was calculated from amygdala seed regions, using explorative linear correlation analysis. Stressed subjects were less capable of down-regulating negative emotion, but had normal acoustic startle responses when asked to up-regulate or maintain emoti...
The abilities to 'read' other peoples' intentions and emotions, and to learn from their experienc... more The abilities to 'read' other peoples' intentions and emotions, and to learn from their experiences, are critical to survival. Previous studies have highlighted the role of sex hormones, notably testosterone and estrogen, in these processes. Yet, it is unclear how these hormones affect social cognition and emotion using acute hormonal administration. In the present double-blind, placebo-controlled study, we administered an acute exogenous dose of testosterone or estrogen to healthy female and male volunteers, respectively, with the aim to investigate the effects of these steroids on social cognitive and emotional processes. Following hormonal and placebo treatment, participants made (1) facial dominance judgments, (2) mental state inferences (Reading the Mind in the Eyes Test, RMET), and (3) learned aversive associations through watching others' emotional responses (observational fear learning, OL). Our results showed that testosterone administration to females enhanced ratings of facial dominance, but diminished their accuracy in inferring mental states. In men, estrogen administration resulted in an increase in emotional (vicarious) reactivity when watching a distressed other during the OL task. Taken together, these results suggest that sex hormones affect social cognitive and emotional functions at several levels linking our results to neuropsychiatric disorders where these functions are impaired.
Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender i... more Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender identity and at-birth assigned sex, are steadily increasing. The underlying neurobiology, and the mechanisms of the often-beneficial cross-sex hormone treatment are unknown. Here, we test hypothesis that own body perception networks (incorporated in the default mode network—DMN, and partly in the salience network—SN), are different in trans-compared with cis-gender persons. We also investigate whether these networks change with cross-sex hormone treatment. Forty transmen (TrM) and 25 transwomen (TrW) were scanned before and after cross-sex hormone institution. We used our own developed Body Morph test (BM), to assess the perception of own body as self. Fifteen cisgender persons were controls. Within and between-group differences in functional connectivity were calculated using independent components analysis within the DMN, SN, and motor network (a control network). Pretreatment, TrM and ...
Gender identity is a core aspect of self-identity and is usually congruent with birth-assigned se... more Gender identity is a core aspect of self-identity and is usually congruent with birth-assigned sex and own body sex-perception. The neuronal circuits underlying gender identity are unknown, but greater awareness of transgenderism has sparked interest in studying these circuits. We did this by comparing brain activation and connectivity in transgender individuals (for whom gender identity and birth-assigned sex are incongruent) with that in cisgender controls (for whom they are congruent) when performing a body self-identification task during functional magnetic resonance imaging. Thirty transgender and 30 cisgender participants viewed images of their own bodies and bodies morphed in sex toward or opposite to birth-assigned sex, rating each image to the degree they identified with it. While controls identified with images of themselves, transgender individuals identified with images morphed “opposite” to their birth-assigned sex. After covarying out the effect of self-similarity rati...
Both transgenderism and homosexuality are facets of human biology, believed to derive from differ... more Both transgenderism and homosexuality are facets of human biology, believed to derive from different sexual differentiation of the brain. The two phenomena are, however, fundamentally unalike, despite an increased prevalence of homosexuality among transgender populations. Transgenderism is associated with strong feelings of incongruence between one's physical sex and experienced gender, not reported in homosexual persons. The present study searches to find neural correlates for the respective conditions, using fractional anisotropy (FA) as a measure of white matter connections that has consistently shown sex differences. We compared FA in 40 transgender men (female birth-assigned sex) and 27 transgender women (male birth-assigned sex), with both homosexual (29 male, 30 female) and heterosexual (40 male, 40 female) cisgender controls. Previously reported sex differences in FA were reproduced in cis-heterosexual groups, but were not found among the cis-homosexual groups. After con...
Biological psychiatry. Cognitive neuroscience and neuroimaging, Jan 9, 2018
Psychopathic traits vary dimensionally in the population and are associated with multiple negativ... more Psychopathic traits vary dimensionally in the population and are associated with multiple negative outcomes. The impaired integration theory (IIT) proposes that psychopathic traits are associated with abnormal neural network topology, such that disturbed integration of neural networks results in a self-perpetuating impairment in rapid integration and learning from multiple components of information. The IIT is based on findings from male offenders presenting high scores on all psychopathic traits. The present study investigated whether IIT predictions of topology abnormalities were associated with psychopathic traits, measured dimensionally, in young adult women with subsyndromal scores. Seventy-three women, with an average age of 25 years, were assessed using the Psychopathy Checklist-Revised and completed resting-state magnetic resonance imaging. Preprocessed time series from 90 anatomical regions were extracted to form connectivity matrices and used to calculate network topology ...
Psychopathy comprises interpersonal, affective, lifestyle and antisocial facets that vary dimensi... more Psychopathy comprises interpersonal, affective, lifestyle and antisocial facets that vary dimensionally in the population and are associated with criminal offending and adverse psychosocial outcomes. Evidence associating these facets with white matter microstructure of the uncinate fasciculus and the cingulum tracts is inconsistent and derives principally from studies of male offenders. In a sample of 99 young women presenting a range of scores on the Psychopathy Checklist: Screening Version, we used Diffusion Tensor Imaging, tractography and Tract-Based Spatial Statistics to investigate microstructure across the brain and of the uncinate fasciculus and cingulum. Right uncinate fasciculus microstructure was negatively associated with the interpersonal facet, while cingulum integrity was not associated with any facet of psychopathy. Whole-brain analyses revealed that both affective and lifestyle facets were negatively correlated with white matter microstructure adjacent to the fusiform gyrus, and the interpersonal facet correlated negatively with the integrity of the fornix. Findings survived adjustment for the other facet scores, and age, verbal and performance IQ. A similar negative association between the interpersonal facet and uncinate fasciculus integrity was previously observed in male offenders. Thus, previous evidence showing that psychopathic traits are associated with functional and structural abnormalities within limbic networks may also apply to females.
Cognitive, affective & behavioral neuroscience, Jan 10, 2017
The phenotype and genotype of antisocial behavior among females are different from those among ma... more The phenotype and genotype of antisocial behavior among females are different from those among males. Previous studies have documented structural brain alterations in males with antisocial behavior, yet little is known about the neural correlates of female antisocial behavior. The present study examined young women who had presented conduct disorder (CDW) prior to age 15 to determine whether brain abnormalities are present in adulthood and whether the observed abnormalities are associated with comorbid disorders or maltreatment that typically characterize this population. Using magnetic resonance imaging and voxel-based morphometry, we compared gray matter volumes (GMV) of 31 women who presented CD by midadolescence and 25 healthy women (HW), age, on average, 23 years. Participants completed structured, validated interviews to diagnose mental disorders, and validated questionnaires to document physical and sexual abuse. Relative to HW, CDW presented increased GMV in the left superio...
Gender dysphoria (GD) is characterized by incongruence between one's identity and gender assigned... more Gender dysphoria (GD) is characterized by incongruence between one's identity and gender assigned at birth. The biological mechanisms of GD are unclear. We investigated brain network connectivity patterns involved in own body perception in the context of self in GD. Twenty-seven female-to-male (FtM) individuals with GD, 27 male controls, and 27 female controls underwent resting state fMRI. We compared functional connections within intrinsic connectivity networks involved in self-referential processes and own body perception-default mode network (DMN) and salience network-and visual networks, using independent components analyses. Behavioral correlates of network connectivity were also tested using self-perception ratings while viewing own body images morphed to their sex assigned at birth, and to the sex of their gender identity. FtM exhibited decreased connectivity of anterior and posterior cingulate and precuneus within the DMN compared with controls. In FtM, higher "self" ratings for bodies morphed towards the sex of their gender identity were associated with greater connectivity of the anterior cingulate within the DMN, during long viewing times. In controls, higher ratings for bodies morphed towards their gender assigned at birth were associated with right insula connectivity within the salience network, during short viewing times. Within visual networks FtM showed weaker connectivity in occipital and temporal regions. Results suggest disconnectivity within networks involved in own body perception in the context of self in GD. Moreover, perception of bodies in relation to self may be reflective rather than reflexive, as a function of mesial prefrontal processes. These may represent
Transsexualism is characterized by feelings of incongruity between one&am... more Transsexualism is characterized by feelings of incongruity between one's natal sex and one's gender identity. It is unclear whether transsexual individuals have a body image that is more congruent with their gender identity than their sex assigned at birth (natal sex) and, if so, whether there are contributions from perceptual dysfunctions. We compared 16 pre-hormone treatment female-to-male transsexual (FtM) individuals to 20 heterosexual female and 20 heterosexual male controls on a visual identification task. Participants viewed photographs of their own body that were morphed by different degrees to bodies of other females or males, and were instructed to rate "To what degree is this picture you?" We also tested global vs. local visual processing using the inverted faces task. FtM differed from both control groups in demonstrating higher self-identification ratings for bodies morphed to the sex congruent with their gender identity, and across a broad range of morph percentages. This difference was more pronounced for longer viewing durations. FtM showed reduced accuracy for upright faces compared with female controls for short duration stimuli, but no advantage for inverted faces. These results suggest different own body identification in FtM, consisting of a relatively diffuse identification with body images congruent with their gender identity. This is more likely accounted for by conscious, cognitive factors than perceptual differences.
Sex Differences in the Human Brain, their Underpinnings and Implications, 2010
During the intrauterine period the fetal brain develops in the male direction through a direct ac... more During the intrauterine period the fetal brain develops in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed into our brain structures when we are still in the womb. However, since sexual differentiation of the genitals takes place in the first two months of pregnancy and sexual differentiation of the brain starts in the second half of pregnancy, these two processes can be influenced independently, which may result in transsexuality. This also means that in the event of ambiguous sex at birth, the degree of masculinization of the genitals may not reflect the degree of masculinization of the brain. There is no proof that social environment after birth has an effect on gender identity or sexual orientation.
fibers connect to mitral and tufted cells of the olfactory bulb, which via the olfactory tract an... more fibers connect to mitral and tufted cells of the olfactory bulb, which via the olfactory tract and tubercle projects † Department of Neurology ‡ Department of Clinical Neuroscience (Neurotech) to the olfactory cortex (Powell et al., 1965). The olfactory cortex in higher mammals comprises the anterior olfac-Karolinska Institute Berzelisvä g 3 tory nucleus and the piriform, periamygdaloid, and transentorhinal cortices (Powell et al., 1965). The olfac-171 77 Stockholm Sweden tory tract also connects directly to the periamygdaloid cortex, and the olfactory tubercle to the mediodorsal
A straightforward method for the preparation of no-carrier-added (n.c.a.) [18F]flumazenil via sta... more A straightforward method for the preparation of no-carrier-added (n.c.a.) [18F]flumazenil via standard nucleophilic radiofluorination of the corresponding nitro-analog Ro 15-2344 has been developed. The labeling was performed by employing the K18F/kryptofix complex in DMF at 160 degrees C for 30 min and equimolar ratio [K/K2.2.2]+18F-/precursor. Under these conditions, an 18F incorporation rate into flumazenil was in the range of 55-60%. The final product was isolated by HPLC purification within a total synthesis time of 75 min and a radiochemical yield of about 30% (EOB). Human post-mortem whole-hemisphere autoradiography of brain sections demonstrated selective uptake of the radioligand in the areas of high density of the central benzodiazepine receptors (BZR). PET studies in a cynomolgus monkey and metabolite studies by HPLC demonstrated similar results by [18F]flumazenil as for [11C]flumazenil. In blocking experiments, almost all radioactivity was inhibited by the addition of unlabeled flumazenil. [18F]Flumazenil is a suitable radioligand for PET assessment of the BZR.
Despite mounting reports about the negative effects of chronic occupational stress on cognitive a... more Despite mounting reports about the negative effects of chronic occupational stress on cognitive and emotional functions, the underlying mechanisms are unknown. Recent findings from structural MRI raise the question whether this condition could be associated with a functional uncoupling of the limbic networks and an impaired modulation of emotional stress. To address this, 40 subjects suffering from burnout symptoms attributed to chronic occupational stress and 70 controls were investigated using resting state functional MRI. The participants' ability to up- regulate, down-regulate, and maintain emotion was evaluated by recording their acoustic startle response while viewing neutral and negatively loaded images. Functional connectivity was calculated from amygdala seed regions, using explorative linear correlation analysis. Stressed subjects were less capable of down-regulating negative emotion, but had normal acoustic startle responses when asked to up-regulate or maintain emoti...
The abilities to 'read' other peoples' intentions and emotions, and to learn from their experienc... more The abilities to 'read' other peoples' intentions and emotions, and to learn from their experiences, are critical to survival. Previous studies have highlighted the role of sex hormones, notably testosterone and estrogen, in these processes. Yet, it is unclear how these hormones affect social cognition and emotion using acute hormonal administration. In the present double-blind, placebo-controlled study, we administered an acute exogenous dose of testosterone or estrogen to healthy female and male volunteers, respectively, with the aim to investigate the effects of these steroids on social cognitive and emotional processes. Following hormonal and placebo treatment, participants made (1) facial dominance judgments, (2) mental state inferences (Reading the Mind in the Eyes Test, RMET), and (3) learned aversive associations through watching others' emotional responses (observational fear learning, OL). Our results showed that testosterone administration to females enhanced ratings of facial dominance, but diminished their accuracy in inferring mental states. In men, estrogen administration resulted in an increase in emotional (vicarious) reactivity when watching a distressed other during the OL task. Taken together, these results suggest that sex hormones affect social cognitive and emotional functions at several levels linking our results to neuropsychiatric disorders where these functions are impaired.
Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender i... more Referrals for gender dysphoria (GD), characterized by a distressful incongruence between gender identity and at-birth assigned sex, are steadily increasing. The underlying neurobiology, and the mechanisms of the often-beneficial cross-sex hormone treatment are unknown. Here, we test hypothesis that own body perception networks (incorporated in the default mode network—DMN, and partly in the salience network—SN), are different in trans-compared with cis-gender persons. We also investigate whether these networks change with cross-sex hormone treatment. Forty transmen (TrM) and 25 transwomen (TrW) were scanned before and after cross-sex hormone institution. We used our own developed Body Morph test (BM), to assess the perception of own body as self. Fifteen cisgender persons were controls. Within and between-group differences in functional connectivity were calculated using independent components analysis within the DMN, SN, and motor network (a control network). Pretreatment, TrM and ...
Gender identity is a core aspect of self-identity and is usually congruent with birth-assigned se... more Gender identity is a core aspect of self-identity and is usually congruent with birth-assigned sex and own body sex-perception. The neuronal circuits underlying gender identity are unknown, but greater awareness of transgenderism has sparked interest in studying these circuits. We did this by comparing brain activation and connectivity in transgender individuals (for whom gender identity and birth-assigned sex are incongruent) with that in cisgender controls (for whom they are congruent) when performing a body self-identification task during functional magnetic resonance imaging. Thirty transgender and 30 cisgender participants viewed images of their own bodies and bodies morphed in sex toward or opposite to birth-assigned sex, rating each image to the degree they identified with it. While controls identified with images of themselves, transgender individuals identified with images morphed “opposite” to their birth-assigned sex. After covarying out the effect of self-similarity rati...
Both transgenderism and homosexuality are facets of human biology, believed to derive from differ... more Both transgenderism and homosexuality are facets of human biology, believed to derive from different sexual differentiation of the brain. The two phenomena are, however, fundamentally unalike, despite an increased prevalence of homosexuality among transgender populations. Transgenderism is associated with strong feelings of incongruence between one's physical sex and experienced gender, not reported in homosexual persons. The present study searches to find neural correlates for the respective conditions, using fractional anisotropy (FA) as a measure of white matter connections that has consistently shown sex differences. We compared FA in 40 transgender men (female birth-assigned sex) and 27 transgender women (male birth-assigned sex), with both homosexual (29 male, 30 female) and heterosexual (40 male, 40 female) cisgender controls. Previously reported sex differences in FA were reproduced in cis-heterosexual groups, but were not found among the cis-homosexual groups. After con...
Biological psychiatry. Cognitive neuroscience and neuroimaging, Jan 9, 2018
Psychopathic traits vary dimensionally in the population and are associated with multiple negativ... more Psychopathic traits vary dimensionally in the population and are associated with multiple negative outcomes. The impaired integration theory (IIT) proposes that psychopathic traits are associated with abnormal neural network topology, such that disturbed integration of neural networks results in a self-perpetuating impairment in rapid integration and learning from multiple components of information. The IIT is based on findings from male offenders presenting high scores on all psychopathic traits. The present study investigated whether IIT predictions of topology abnormalities were associated with psychopathic traits, measured dimensionally, in young adult women with subsyndromal scores. Seventy-three women, with an average age of 25 years, were assessed using the Psychopathy Checklist-Revised and completed resting-state magnetic resonance imaging. Preprocessed time series from 90 anatomical regions were extracted to form connectivity matrices and used to calculate network topology ...
Psychopathy comprises interpersonal, affective, lifestyle and antisocial facets that vary dimensi... more Psychopathy comprises interpersonal, affective, lifestyle and antisocial facets that vary dimensionally in the population and are associated with criminal offending and adverse psychosocial outcomes. Evidence associating these facets with white matter microstructure of the uncinate fasciculus and the cingulum tracts is inconsistent and derives principally from studies of male offenders. In a sample of 99 young women presenting a range of scores on the Psychopathy Checklist: Screening Version, we used Diffusion Tensor Imaging, tractography and Tract-Based Spatial Statistics to investigate microstructure across the brain and of the uncinate fasciculus and cingulum. Right uncinate fasciculus microstructure was negatively associated with the interpersonal facet, while cingulum integrity was not associated with any facet of psychopathy. Whole-brain analyses revealed that both affective and lifestyle facets were negatively correlated with white matter microstructure adjacent to the fusiform gyrus, and the interpersonal facet correlated negatively with the integrity of the fornix. Findings survived adjustment for the other facet scores, and age, verbal and performance IQ. A similar negative association between the interpersonal facet and uncinate fasciculus integrity was previously observed in male offenders. Thus, previous evidence showing that psychopathic traits are associated with functional and structural abnormalities within limbic networks may also apply to females.
Cognitive, affective & behavioral neuroscience, Jan 10, 2017
The phenotype and genotype of antisocial behavior among females are different from those among ma... more The phenotype and genotype of antisocial behavior among females are different from those among males. Previous studies have documented structural brain alterations in males with antisocial behavior, yet little is known about the neural correlates of female antisocial behavior. The present study examined young women who had presented conduct disorder (CDW) prior to age 15 to determine whether brain abnormalities are present in adulthood and whether the observed abnormalities are associated with comorbid disorders or maltreatment that typically characterize this population. Using magnetic resonance imaging and voxel-based morphometry, we compared gray matter volumes (GMV) of 31 women who presented CD by midadolescence and 25 healthy women (HW), age, on average, 23 years. Participants completed structured, validated interviews to diagnose mental disorders, and validated questionnaires to document physical and sexual abuse. Relative to HW, CDW presented increased GMV in the left superio...
Gender dysphoria (GD) is characterized by incongruence between one's identity and gender assigned... more Gender dysphoria (GD) is characterized by incongruence between one's identity and gender assigned at birth. The biological mechanisms of GD are unclear. We investigated brain network connectivity patterns involved in own body perception in the context of self in GD. Twenty-seven female-to-male (FtM) individuals with GD, 27 male controls, and 27 female controls underwent resting state fMRI. We compared functional connections within intrinsic connectivity networks involved in self-referential processes and own body perception-default mode network (DMN) and salience network-and visual networks, using independent components analyses. Behavioral correlates of network connectivity were also tested using self-perception ratings while viewing own body images morphed to their sex assigned at birth, and to the sex of their gender identity. FtM exhibited decreased connectivity of anterior and posterior cingulate and precuneus within the DMN compared with controls. In FtM, higher "self" ratings for bodies morphed towards the sex of their gender identity were associated with greater connectivity of the anterior cingulate within the DMN, during long viewing times. In controls, higher ratings for bodies morphed towards their gender assigned at birth were associated with right insula connectivity within the salience network, during short viewing times. Within visual networks FtM showed weaker connectivity in occipital and temporal regions. Results suggest disconnectivity within networks involved in own body perception in the context of self in GD. Moreover, perception of bodies in relation to self may be reflective rather than reflexive, as a function of mesial prefrontal processes. These may represent
Transsexualism is characterized by feelings of incongruity between one&am... more Transsexualism is characterized by feelings of incongruity between one's natal sex and one's gender identity. It is unclear whether transsexual individuals have a body image that is more congruent with their gender identity than their sex assigned at birth (natal sex) and, if so, whether there are contributions from perceptual dysfunctions. We compared 16 pre-hormone treatment female-to-male transsexual (FtM) individuals to 20 heterosexual female and 20 heterosexual male controls on a visual identification task. Participants viewed photographs of their own body that were morphed by different degrees to bodies of other females or males, and were instructed to rate "To what degree is this picture you?" We also tested global vs. local visual processing using the inverted faces task. FtM differed from both control groups in demonstrating higher self-identification ratings for bodies morphed to the sex congruent with their gender identity, and across a broad range of morph percentages. This difference was more pronounced for longer viewing durations. FtM showed reduced accuracy for upright faces compared with female controls for short duration stimuli, but no advantage for inverted faces. These results suggest different own body identification in FtM, consisting of a relatively diffuse identification with body images congruent with their gender identity. This is more likely accounted for by conscious, cognitive factors than perceptual differences.
Sex Differences in the Human Brain, their Underpinnings and Implications, 2010
During the intrauterine period the fetal brain develops in the male direction through a direct ac... more During the intrauterine period the fetal brain develops in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed into our brain structures when we are still in the womb. However, since sexual differentiation of the genitals takes place in the first two months of pregnancy and sexual differentiation of the brain starts in the second half of pregnancy, these two processes can be influenced independently, which may result in transsexuality. This also means that in the event of ambiguous sex at birth, the degree of masculinization of the genitals may not reflect the degree of masculinization of the brain. There is no proof that social environment after birth has an effect on gender identity or sexual orientation.
fibers connect to mitral and tufted cells of the olfactory bulb, which via the olfactory tract an... more fibers connect to mitral and tufted cells of the olfactory bulb, which via the olfactory tract and tubercle projects † Department of Neurology ‡ Department of Clinical Neuroscience (Neurotech) to the olfactory cortex (Powell et al., 1965). The olfactory cortex in higher mammals comprises the anterior olfac-Karolinska Institute Berzelisvä g 3 tory nucleus and the piriform, periamygdaloid, and transentorhinal cortices (Powell et al., 1965). The olfac-171 77 Stockholm Sweden tory tract also connects directly to the periamygdaloid cortex, and the olfactory tubercle to the mediodorsal
A straightforward method for the preparation of no-carrier-added (n.c.a.) [18F]flumazenil via sta... more A straightforward method for the preparation of no-carrier-added (n.c.a.) [18F]flumazenil via standard nucleophilic radiofluorination of the corresponding nitro-analog Ro 15-2344 has been developed. The labeling was performed by employing the K18F/kryptofix complex in DMF at 160 degrees C for 30 min and equimolar ratio [K/K2.2.2]+18F-/precursor. Under these conditions, an 18F incorporation rate into flumazenil was in the range of 55-60%. The final product was isolated by HPLC purification within a total synthesis time of 75 min and a radiochemical yield of about 30% (EOB). Human post-mortem whole-hemisphere autoradiography of brain sections demonstrated selective uptake of the radioligand in the areas of high density of the central benzodiazepine receptors (BZR). PET studies in a cynomolgus monkey and metabolite studies by HPLC demonstrated similar results by [18F]flumazenil as for [11C]flumazenil. In blocking experiments, almost all radioactivity was inhibited by the addition of unlabeled flumazenil. [18F]Flumazenil is a suitable radioligand for PET assessment of the BZR.
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