Exploring the influence of stress on aggressive behavior and sexual function: Role of neuromodulator pathways and epigenetics

Stress is a complex and multifaceted phenomenon that can significantly influence both aggressive behavior and sexual function. This review explores the intricate relationship between stress, neuromodulator pathways, and epigenetics, shedding light on the various mechanisms that underlie these connections. While the role of stress in both aggression and sexual behavior is well-documented, the mechanisms through which it exerts its effects are multifarious and not yet fully understood. The review begins by delving into the potential influence of stress on the Hypothalamic-Pituitary-Adrenal (HPA) axis, glucocorticoids, and the neuromodulators involved in the stress response. The intricate interplay between these systems, which encompasses the regulation of stress hormones, is central to understanding how stress may contribute to aggressive behavior and sexual function. Several neuromodulator pathways are implicated in both stress and behavior regulation. We explore the roles of norepinephrine, serotonin, oxytocin, and androgens in mediating the effects of stress on aggression and sexual function. It is important to distinguish between general sexual behavior, sexual motivation, and the distinct category of "sexual aggression" as separate constructs, each necessitating specific examination. Additionally, epigenetic mechanisms emerge as crucial factors that link stress to changes in gene expression patterns and, subsequently, to behavior. We then discuss how epigenetic modifications can occur in response to stress exposure, altering the regulation of genes associated with stress, aggression, and sexual function. While numerous studies support the association between epigenetic changes and stress-induced behavior, more research is necessary to establish definitive links. Throughout this exploration, it becomes increasingly clear that the relationship between stress, neuromodulator pathways, and epigenetics is intricate and multifaceted. The review emphasizes the need for further research, particularly in the context of human studies, to provide clinical significance and to validate the existing findings from animal models. By better understanding how stress influences aggressive behavior and sexual function through neuromodulator pathways and epigenetic modifications, this research aims to contribute to the development of innovative protocols of precision medicine and more effective strategies for managing the consequences of stress on human behavior. This may also pave way for further research into risk factors and underlying mechanisms that may associate stress with sexual aggression which finds application not only in neuroscience, but also law, ethics, and the humanities in general.

Timing of peripubertal steroid exposure predicts visuospatial cognition in men: Evidence from three samples

Experiments in male rodents demonstrate that sensitivity to the organizational effects of steroid hormones decreases across the pubertal window, with earlier androgen exposure leading to greater masculinization of the brain and behavior. Similarly, some research suggests the timing of peripubertal exposure to sex steroids influences aspects of human psychology, including visuospatial cognition. However, prior studies have been limited by small samples and/or imprecise measures of pubertal timing. We conducted 4 studies to clarify whether the timing of peripubertal hormone exposure predicts performance on male-typed tests of spatial cognition in adulthood. In Studies 1 (n = 1095) and 2 (n = 173), we investigated associations between recalled pubertal age and spatial cognition in typically developing men, controlling for current testosterone levels in Study 2. In Study 3 (n = 51), we examined the relationship between spatial performance and the age at which peripubertal hormone replacement therapy was initiated in a sample of men with Isolated GnRH Deficiency. Across Studies 1-3, effect size estimates for the relationship between spatial performance and pubertal timing ranged from. -0.04 and -0.27, and spatial performance was unrelated to salivary testosterone in Study 2. In Study 4, we conducted two meta-analyses of Studies 1-3 and four previously published studies. The first meta-analysis was conducted on correlations between spatial performance and measures of the absolute age of pubertal timing, and the second replaced those correlations with correlations between spatial performance and measures of relative pubertal timing where available. Point estimates for correlations between pubertal timing and spatial cognition were -0.15 and -0.12 (both p < 0.001) in the first and second meta-analyses, respectively. These associations were robust to the exclusion of any individual study. Our results suggest that, for some aspects of neural development, sensitivity to gonadal hormones declines across puberty, with earlier pubertal hormone exposure predicting greater sex-typicality in psychological phenotypes in adulthood. These results shed light on the processes of behavioral and brain organization and have implications for the treatment of IGD and other conditions wherein pubertal timing is pharmacologically manipulated.

The neuropsychology of sex offenders: a meta-analysis

Typically, neuropsychological studies of sex offenders have grouped together different types of individuals and different types of measures. This is why results have tended to be nonspecific and divergent across studies. Against this background, the authors undertook a review of the literature regarding the neuropsychology of sex offenders, taking into account subgroups based on criminological theories. They also conducted a meta-analysis of the data to demonstrate the cognitive heterogeneity of sex offenders statistically. Their main objective was to test the hypothesis to the effect that the neuropsychological deficits of sex offenders are not broad and generalized compared with specific subgroups of participants based on specific measures. In all, 23 neuropsychological studies reporting data on 1,756 participants were taken into consideration. As expected, a highly significant, broad, and heterogeneous overall effect size was found. Taking subgroups of participants and specific cognitive measures into account significantly improved homogeneity. Sex offenders against children tended to obtain lower scores than did sex offenders against adults on higher order executive functions, whereas sex offenders against adults tended to obtain results similar to those of non-sex offenders, with lower scores in verbal fluency and inhibition. However, it is concluded that neuropsychological data on sex offenders are still too scarce to confirm these trends or to test more precise hypotheses. For greater clinical relevance, future neuropsychological studies should consider specific subgroups of participants and measures to verify the presence of different cognitive profiles.

Neurobiological determinism: human freedom of choice and criminal responsibility

Several authors have argued that criminal behavior is generally caused by neurobiological deficits. This assumption not only questions the concept of free will and a person's responsibility for his or her own actions but also the principle of guilt in criminal law. When critically examining the current state of research, it becomes apparent that the results are not sufficient to support the existence of a universally valid neurobiological causality of criminal behavior. Moreover, the assumption of total neurobiological determination of human behavior and the impossibility of individual responsibility are characterized by both faulty empiricism and methodical misconceptions. The principle of relative determinism and the analysis of the offender's behavior at the time of the offense thus remain the central and cogent approach to the assessment of criminal responsibility.

Familial paraphilia: a pilot study with the construction of genograms

Biological factors are likely predisposing and modulating elements in sexually deviant behavior. The observation that paraphilic behavior tends to cluster in some families is intriguing and potentially raises questions as to whether shared genetic factors may play a role in the transmission of paraphilia. This pilot study introduces five families in which we found presence of paraphilia over generations. We constructed genograms on the basis of a standardized family history. Results document the aggregation of sexual deviations within the sample of families and support a clinical/phenomenological heterogeneity of sexual deviation. The concept of paraphilia in relation to phenotypic expressions and the likelihood of a spectrum of related disorders must be clarified before conclusions can be reached as to family aggregation of paraphilia based on biological factors.

Is homosexuality a paraphilia? The evidence for and against

Whether homosexuality should be described as one among many paraphilic sexual interests or an altogether different dimension of sexual interest has long been discussed in terms of its political and social implications. The present article examined the question instead by comparing the major correlates and other features of homosexuality and of the paraphilias, including prevalence, sex ratio, onset and course, fraternal birth order, physical height, handedness, IQ and cognitive neuropsychological profile, and neuroanatomy. Although those literatures remain underdeveloped, the existing findings thus far suggest that homosexuality has a pattern of correlates largely, but not entirely, distinct from that identified among the paraphilias. At least, if homosexuality were deemed a paraphilia, it would be relatively unique among them, taxonometrically speaking.

Executive function profiles of pedophilic and nonpedophilic child molesters

There is increasing evidence of neurocognitive dysfunction among child molesters, supporting the notion of brain anomalies among pedophiles. However, approximately half of child molesters are not pedophilic (i.e., are not primarily attracted to children), and neurocognitive differences between pedophilic (PED) and nonpedophilic (NPED) child molesters are not well understood. The purpose of this study was to assess neurocognition, specifically executive functioning (EF), among phallometrically defined PED and NPED child molesters, relative to nonsexual offenders (NSO). Participants (N = 89) were compared on seven EF domains. Results revealed that (a) child molesters exhibited an overall executive profile that was different from that of NSOs, with PEDs differing from NSOs but not from NPEDs; (b) child molesters on the whole performed better than NSOs on abstract reasoning and more poorly on inhibition; and (c) PEDs performed better than NPEDs on planning and exhibited better overall performance accuracy relative to NPEDs. These results suggest that PEDs exhibit a more deliberate, planful response style characterized by greater self-monitoring; whereas NPEDs appear to respond more impulsively. The current report further elucidates neurocognition among child molesters and highlights the need for future research examining subtypes of child molesters.

Paraphilias across cultures: contexts and controversies

Cultures define and describe what is normal and what is deviant. These definitions of normality vary across cultures and are influenced by a number of factors, such as religion. Cultures have been described in various ways, including sex-positive where the sexual act itself is seen as important for pleasure, or sex-negative where the sexual act is seen only as for procreative purposes. The role and development of paraphilias across cultures is also variable, with cultures defining what is legal or illegal. Such differences make collection of epidemiological data and comparison across paraphilias problematic. This discussion suggests that characteristics of cultures may influence the rate of reporting paraphilias, as well as the rate of paraphilias themselves. Furthermore, with increased industrialization and urbanization, families will become more nuclear, with attitudes toward sex and paraphilias changing as well. This review also explores whether paraphilias can be seen as culture-bound syndromes, and recommends consideration of a number of conceptual issues regarding the diagnosis and prevalence of paraphilias as future cross-cultural studies on this topic are developed.

Etiology of pedophilia from a neurodevelopmental perspective: markers and brain alterations

DEVELOPMENT

Distinct signs have been associated with a wide range of neurodevelopmental disorders and warning signs of neural developmental problems have also been observed in pedophiles. Continuing this line of research, several neuroimaging studies have found neural alterations in this disorder.

CONCLUSIONS

Pedophilia has been related to distinct indicators of neurodevelopmental alterations such as low intelligence quotient, left-handedness and smaller stature, among others. In addition, pedophiles show several neural alterations and a predominantly subcortical pattern of cerebral activation to sexual stimuli. The results of these studies suggest that the origin of pedophilia may partly lie in brain alterations due to problems during neural development, although these alterations do not absolve these persons of responsibility for their actions.

Neurocognitive differences between pedophilic and nonpedophilic child molesters

Although some evidence exists that child molesters may be characterized by structural and functional brain abnormalities, findings across studies are inconsistent. Past cognitive research in this area has been extensively criticized for relying on conceptually weak batteries, measures of questionable reliability, and poorly defined samples (i.e., failing to distinguish between pedophilic and nonpedophilic child molesters). The present study aimed to address the weaknesses of past research by comparing 40 child molesters (20 pedophilic and 20 nonpedophilic) and 20 demographically matched nonoffender controls on six well-defined neurocognitive composite scores of comparable reliability (i.e., semantic knowledge, executive functioning, processing speed, motor speed, auditory memory, and visual memory). Results indicated that pedophilic child molesters exhibit slower processing speed, nonpedophilic child molesters exhibit poorer semantic knowledge, and both molester groups exhibit executive weaknesses as compared to nonoffender controls. This study is the first to compare the two molester types on neurocognitive functions. The observed differences between the molester groups help explain inconsistencies in past research and demonstrate the need to distinguish between the two types of child molesters when studying neurobiologic underpinnings of sexual offending.

Facial and prosodic affect recognition among pedophilic and nonpedophilic criminal child molesters

The present study compared facial and prosodic affect recognition abilities among pedophilic and nonpedophilic child molesters and community-dwelling controls. Pedophilic child molesters are characterized by primary sexual interest in prepubescent children, whereas nonpedophilic child molesters are characterized by offending against children despite being primarily sexually attracted to adults. The results showed that nonpedophilic child molesters made more errors in recognizing both facial and prosodic affect, performing more poorly than both controls and pedophilic child molesters. These findings are consistent with greater psychopathic tendencies among nonpedophilic molesters as well as with prior findings of smaller amygdala volume among child molesters.

Sadism, sadomasochism, sex, and violence

The true prevalence of sexual sadism (and its variants) is unknown. However, all clinicians will knowingly or unknowingly encounter patients with this disorder. Regretfully, few programs offer adequate education in normal sexuality and even less provide training in the assessment and treatment of pathologic sexual interests. This review synthesizes current theories about possible etiologies of criminal sexual sadism and the resulting implications for diagnosis and treatment of this sexual disorder. Included is a review of theories of criminally sadistic sexual motivations, response patterns, and physiology, including possible neurophysiologic factors and more complex interactions. This review focuses primarily on published English-language scientific studies of sexual sadism. It should be noted that my use of the term sadism refers to nonconsensual sexual aggression.

Cerebral white matter deficiencies in pedophilic men

The present investigation sought to identify which brain regions distinguish pedophilic from nonpedophilic men, using unbiased, automated analyses of the whole brain. T1-weighted magnetic resonance images (MRIs) were acquired from men who demonstrated illegal or clinically significant sexual behaviors or interests (n = 65) and from men who had histories of nonsexual offenses but no sexual offenses (n = 62). Sexual interest in children was assessed by participants' admissions of pedophilic interest, histories of committing sexual offenses against children, and psychophysiological responses in the laboratory to erotic stimuli depicting children or adults. Automated parcellation of the MRIs revealed significant negative associations between pedophilia and white matter volumes of the temporal and parietal lobes bilaterally. Voxel-based morphometry corroborated the associations and indicated that the regions of lower white matter volumes followed, and were limited to, two major fiber bundles: the superior fronto-occipital fasciculus and the right arcuate fasciculus. No significant differences were found in grey matter or in cerebrospinal fluid (CSF). Because the superior fronto-occipital and arcuate fasciculi connect the cortical regions that respond to sexual cues, these results suggest (1) that those cortical regions operate as a network for recognizing sexually relevant stimuli and (2) that pedophilia results from a partial disconnection within that network.

The neuropsychology and neurology of sexual deviance: a review and pilot study

Current neurological hypotheses of paraphilia posit that sexual deviance is associated with frontal and/or temporal lobe damage. This broad conception is based on few investigations, however, and the first goal of this study was to review the existing data derived from neuropsychiatry, neuroimaging and neuropsychology. It is concluded that although fronto-temporal dysfunctions are sporadically reported among sexual offenders, the evidence is scarce and it might not be specific to this type of offending. The second objective of this investigation was to gather preliminary neuropsychological data with more homogeneous subgroups of sexual offenders. A profile of lower-order executive dysfunctions (e.g. sustained attention and inhibition) and verbal deficits with intact or good capacities for higher-order executive functioning (e.g. reasoning and cognitive flexibility) and visuo-spatial processing was preferentially found among sexual offenders, suggesting basal fronto-temporal anomalies. Importantly, pedophiles were more consistently and severely impaired than rapists of adults. However, this basal fronto-temporal profile is not characteristic of sexual deviance, as it is also found in association with delinquency and criminality in general. Future neuropsychological and brain imaging studies should consider subgroups of sexual offenders and recruit non-sexual violent persons and non-violent individuals in order to disentangle the complex relations between brain anomalies and sexual deviance.

Quantitative reanalysis of aggregate data on IQ in sexual offenders

General intelligence has been the most commonly studied neuropsychological characteristic of sexual offenders for over 70 years. Results, however, have been highly inconsistent. To assess whether sexual offenders score lower in IQ than nonsexual offenders and to explore which sexual offense characteristics relate to IQ, the authors reanalyzed all reports providing sufficient information. Data spanned 236 samples, comprising 25,146 sexual offenders and controls. The literature contained sufficient information to permit comparison of adult versus juvenile sexual offenders, offenders targeting children versus adults, offenders targeting their own versus unrelated children, and offenders targeting boys versus girls. Results confirm the association between IQ and sexual offending and suggest that previous discrepancies are attributable to how many pedophilic individuals were in each sample.

Intelligence, Memory, and Handedness in Pedophilia

A sample of 473 male patients with pedophilia (assessed by the patients' sexual history and penile response in the laboratory to standardized, erotic stimuli) or other problematic sexual interests or behaviors received brief neuropsychological assessments. Neuropsychological measures included a short form of the Wechsler Adult Intelligence Scale--Revised (D. Wechsler, 1981), the Hopkins Verbal Learning Test--Revised (R. H. B. Benedict, D. Schretlen. L. Groninger. & J. Brandt, 1998), the Brief Visuospatial Memory Test--Revised (R. H. B. Benedict, 1997), and the Edinburgh Handedness Inventory (S. M. Williams, 1986). Pedophilia showed significant negative correlations with IQ and immediate and delayed recall memory. Pedophilia was also related to non-right-handedness even after covarying age and IQ. These results suggest that pedophilia is linked to early neurodevelopmental perturbations.

Blows to the head during development can predispose to violent criminal behaviour: rehabilitation of consequences of head injury is a measure for crime prevention

Criminal behaviour and violence may be the consequence of head injuries acquired during childhood and youth (gang fights, domestic violence, small blows to the head while driving, falls and so forth). In this study, a comparison was made of the school and head injury histories of violent and non-violent prisoners. It was found that the delinquent subjects in both groups had a history of academic difficulties. However, what differentiated the violent from the non-violent group was a history of having suffered head injuries that were never treated. Problems at school are not enough themselves to predict violent behaviour. A history of discrete neurological damage as a consequence to blows received to the head must also be present. The results suggest to the authors that the treatment of the cognitive, behavioural and emotional consequences of brain injury could be a measure for crime prevention. Measures both for prevention and rehabilitation are discussed.

Prediction of recidivism in exhibitionists: psychological, phallometric, and offense factors

Exhibitionists have traditionally been regarded as nuisance offenders. However, empirical studies show that some offenders can be highly recidivistic and can escalate to incidents of Hands-on sexual assault. The objective of this study was to investigate predictors of recidivism in exhibitionists and clarify the differences between Hands-on and Hands-off sexual recidivists. The hundred and twenty-one exhibitionists were assessed at a university teaching hospital between 1983 and 1996. Archival data came from medical files and police files. The Psychopathy Checklist-Revised (PCL-R) was assessed retrospectively. Results indicated that over a mean follow-up period of 6.84 years, 11.7, 16.8, and 32.7% of exhibitionists were charged with or convicted of sexual, violent, or criminal offenses, respectively. Sexual reoffending recidivists were less educated, and had more prior sexual and criminal offenses. Violent, recidivists were also less educated, had lower Derogatis Sexual Functioning Inventory (DSFI) scores, higher PCL-R Totals, and more prior sexual, violent, and criminal offenses. Criminal recidivists were younger, less educated, had lower DSFI scores, higher PCL-R scores, higher Pedophile Indices, and more prior sexual, violent, and criminal offenses. Hands-on sexual recidivists demonstrated higher PCL-R ratings, higher Pedophile and Rape indices, and more prior sexual, violent, and criminal offenses than did Hands-off counterparts.

Clinical features of pedophilia and implications for treatment

The authors discuss the diagnostic criteria for pedophilia and review the literature on its clinical features, including data on prevalence, gender, age of onset, number of victims, frequency and type of acts, violence, impulsivity, and insight. Findings concerning the characteristics of victims (e.g., sex, age, relationship to the pedophile) and research on pedophilic subtypes-exclusive versus nonexclusive; incestuous versus nonincestuous; heterosexual, homosexual, or bisexual-are reviewed. Studies have shown that pedophiles may share many psychiatric features beyond deviant sexual desire, including high rates of comorbid axis I disorders (affective disorders, substance use disorders, impulse control disorders, other paraphilias) as well as severe axis II psychopathology (especially antisocial and Cluster C personality disorders). The authors present several possible etiological models for pedophilia and conclude that further research is needed concerning the etiological role of a childhood history of sexual abuse as well as the underlying neurobiology of deviant sexual arousal and decreased erotic differentiation. Finally, findings concerning pharmacological and cognitive-behavioral treatments for pedophilia are briefly reviewed. Recidivism, drop-out, and noncompliance are significant problems in the treatment of pedophilia. The authors review predictors of treatment outcome and conclude that pedophilia is extremely difficult to treat and that effective treatment needs to be intensive, long-term, and comprehensive, possibly with lifetime follow-up.

Hippocampal pathology in two mentally ill paraphiliacs

Paraphilias or disorders of sexual behavior have markedly increased in prevalence during the last decade. Until now no published neuropathological studies on paraphilia have appeared in the medical literature. A computerized search was done on all available medical and autopsy records of a large urban hospital (St. Elizabeths Hospital, Washington, DC) for any mention of deviant sexual behavior. Cases were then reviewed for presence of a history consistent with DSM-IV diagnoses of paraphilia. Two such cases were identified. Neuropathological examination in both cases revealed simple cell atrophy of pyramidal cells confined to different hippocampal subfields. Reactive astrocytosis was present in the outer strata of the affected regions. The pathological changes in the hippocampus resemble those reported after persistent stress or long-term chronic glucocorticoid administration. The accompanying astrocytosis indicates a reactive, ongoing process. The findings suggest new therapeutic interventions in the treatment of paraphilia.

Personality and neuropsychological function in violent, sexual and arson offenders

We aimed to test the hypothesis that incarcerated offender populations will not differ in neuropsychological test performance if patients are matched on age, intelligence and personality profile, particularly if impulsive aggressive traits and confounds such as substance misuse and performance anxiety are controlled for. 27 violent offenders, 20 sex offenders and 13 arson offenders detained in maximum security hospitals completed dimensional assessments of personality function and were assessed on a battery of frontal and temporal neuropsychological tests. All patients completed a variety of self-report measures of cognitive, affective and behavioural dispositions relevant to offender populations. Trait impulsivity was further assessed and composite impulsivity scores were derived. Assessments of emotional state were administered prior to neuropsychological testing. All patients met the criteria for a DSM-III-R personality disorder diagnosis. There were no significant group differences in age, IQ, or educational attainment. There were no differences in the personality profile of the offender group although sex offenders scored higher on trait anxiety, depression and tension measures. Groups did not significantly differ in their performance on neuropsychological tests apart from poorer perseverative error scores on the Wisconsin Card Sort Test in arsonists, which could not be accounted for by state anxiety or depression scores.

The paraphilic and hypersexual disorders: an overview

In this article, the first of a two-part series, the authors present reasons for considering the paraphilic and hypersexual disorders together and provide an overview of these disorders. The DSM-IV diagnostic criteria for paraphilias are reviewed, and proposed criteria for hypersexual disorders are presented. The question of whether the paraphilic and hypersexual disorders should be considered within the spectrum of obsessive-compulsive disorders is considered. The authors then review the epidemiology of these disorders, and discuss some implications of recent sexual predator legislation. The authors discuss the etiology of the paraphilias and hypersexual disorders, and consider the role of endocrinological function, findings from brain imaging and neuropsychological testing, findings from primate research, the monoamine hypothesis, the imprinting hypothesis, social learning theory, the concept of courtship disorder, the role of obsessive-compulsive elements, psychodynamic theories, and genetic factors. The phenomenology of the paraphilias and hypersexual disorders is discussed, including the tendency for multiple paraphilias to co-occur, the lack of a specific offender profile, the predominance of males among those with paraphilias, the incidence of a history of victimization in individuals with paraphilias and compulsive sexual disorders, the onset and course of both types of disorders, and the lack of internal motivation for change in individuals with paraphilias and hypersexual disorders. The authors then discuss disorders that commonly co-occur with paraphilias and compulsive sexual disorders, including mood disorders, substance abuse and dependence disorders, attention-deficit/hyperactivity disorder, anxiety and impulse control disorders, and personality disorders. The second article in the series will discuss the clinical assessment and the behavioral and psychopharmacological treatment of these disorders. A guide for clinicians and patients on where and how to find specialized clinicians and treatment resources in the United States will also be provided.

Neuroimaging studies of antisocial behaviour

OBJECTIVE

To review recent neuroimaging studies of antisocial behaviour, including criminality, psychopathy, sexual offending, aggression, and violence.

METHOD

Using OVID software, Psycinfo and Medline were searched for studies undertaken in the last 15 years. A brief outline of each technology is followed by a survey of published reports from refereed journals. Where indicated, critical appraisal is offered.

RESULTS

Converging evidence from multiple studies of structure and function indicates that abnormal prefrontal (and probably subcortical) circuitry are very likely involved in antisocial behaviour.

CONCLUSIONS

Clinicians should be aware of emerging findings from biological studies of antisociality. Future neuroimaging and other biologically based work, especially when combined with psychosocial initiatives, should yield fruit in attempts to better understand, treat, and prevent such socially devastating and destructive behaviour.

Quantitative EEG studies of pedophilia

Ninety six pedophiles, whose sexual orientation was confirmed by phallometric response to sexual stimuli, were investigated with quantitative EEG and compared to age- and sex-matched healthy controls. The EEG analysis showed a pattern of increased frontal delta, theta and alpha power (especially during verbal processing) and a pattern of reduced interhemispheric and increased intrahemispheric-interhemispheric coherence, right and left (only during verbal processing), an effect that was restricted to those who showed maximal erotic arousal for sexual partners aged 6-12 years. These findings will be discussed in the context of recent studies which suggest that sexual deviations in the male relate to altered dominant hemispheric functions with disruption of frontal interhemispheric relationships.