The effect of estradiol add-back: a longitudinal MRI study in prostate cancer patients.

We investigated the effect of estradiol add-back therapy (EAT) on brain activation related to cognitive function and affect in addition to putative changes in gray and white matter volume in testosterone depleted participants with prostate cancer. We conducted a randomized controlled, double-blinded trial in which 40 patients received 0.9 mg of transdermal estradiol per day for 6 months or matched placebo. Anatomical MRI and three functional MRI (fMRI) scans were obtained for the emotion recognition task, verbal memory task, and visuospatial memory task. Activation in corresponding cognitive and affective brain networks was demonstrated for all tasks. Longitudinally, there was no difference in brain activation, reaction time, or accuracy in response to the fMRI tasks between the EAT group and placebo group at 6 months. In addition, there was no detectable change in whole-brain gray or white matter volume or in hippocampal volume between the two groups after 6 months. This study supports earlier findings that EAT does not improve verbal memory or affect and has no immediate effect on hippocampal volume in testosterone depleted patients with prostate cancer.

Increased cortical surface area but not altered cortical thickness or gyrification in bipolar disorder following stabilisation from a first episode of mania.

BACKGROUND: Despite reports of altered brain morphology in established bipolar disorder (BD), there is limited understanding of when these morphological abnormalities emerge. Assessment of patients during the early course of illness can help to address this gap, but few studies have examined surface-based brain morphology in patients at this illness stage. METHODS: We completed a secondary analysis of baseline data from a randomised control trial of BD individuals stabilised after their first episode of mania (FEM). The magnetic resonance imaging scans of n = 35 FEM patients and n = 29 age-matched healthy controls were analysed. Group differences in cortical thickness, surface area and gyrification were assessed at each vertex of the cortical surface using general linear models. Significant results were identified at p < 0.05 using cluster-wise correction. RESULTS: The FEM group did not differ from healthy controls with regards to cortical thickness or gyrification. However, there were two clusters of increased surface area in the left hemisphere of FEM patients, with peak coordinates falling within the lateral occipital cortex and pars triangularis. CONCLUSIONS: Cortical thickness and gyrification appear to be intact in the aftermath of a first manic episode, whilst cortical surface area in the inferior/middle prefrontal and occipitoparietal cortex is increased compared to age-matched controls. It is possible that increased surface area in the FEM group is the outcome of abnormalities in a premorbidly occurring process. In contrast, the findings raise the hypothesis that cortical thickness reductions seen in past studies of individuals with more established BD may be more attributable to post-onset factors.

Effect of estradiol on cognition in men undergoing androgen deprivation therapy: A randomized placebo-controlled trial.

OBJECTIVE: Roles for estradiol in modulating cognition in men remain uncertain. We assessed the isolated effects of estradiol on cognition in men in the absence of testosterone. DESIGN: Randomized trial of transdermal estradiol 0.9 mg daily, or matched placebo, for 6 months, hypothesizing that estradiol would improve verbal learning, verbal memory, and spatial problem solving over time. PATIENTS: Men receiving androgen deprivation therapy (ADT) for prostate cancer. MEASUREMENTS: Cognition was assessed by a tablet-based cognitive battery (Cogstate) at baseline, Month 1, Month 3, and Month 6. Anxiety and depression symptoms were assessed using the Hospital Anxiety and Depression Scale. RESULTS: Seventy-eight participants were randomized. Baseline mean scores were 21.0 (standard deviation [SD] 4.1) for the International Shopping List test (ISL), assessing verbal learning and memory (higher scores better), and 60.4 (SD 19.5) for the Groton Maze Learning test (GML), assessing spatial problem solving (lower scores better). There was no significant difference in performance over time for the estradiol group versus the placebo group for the ISL, mean adjusted difference (MAD) 0.7 (95% confidence interval [CI] -1.2 to 2.5), p = .36, or the GML, MAD -3.2 (95% CI -12.0 to 5.6), p = 0.53. There was no significant difference between groups over time in performance in any other cognitive domain, or on depression or anxiety scores. CONCLUSIONS: We found no major effects of estradiol on cognition in men with castrate testosterone concentrations. Although the cognitive effects of ADT are debated, this study suggests that any such effects are unlikely to be prevented by the administration of estradiol.

In vivo hippocampal subfield volumes in bipolar disorder-A mega-analysis from The Enhancing Neuro Imaging Genetics through Meta-Analysis Bipolar Disorder Working Group.

The hippocampus consists of anatomically and functionally distinct subfields that may be differentially involved in the pathophysiology of bipolar disorder (BD). Here we, the Enhancing NeuroImaging Genetics through Meta-Analysis Bipolar Disorder workinggroup, study hippocampal subfield volumetry in BD. T1-weighted magnetic resonance imaging scans from 4,698 individuals (BD = 1,472, healthy controls [HC] = 3,226) from 23 sites worldwide were processed with FreeSurfer. We used linear mixed-effects models and mega-analysis to investigate differences in hippocampal subfield volumes between BD and HC, followed by analyses of clinical characteristics and medication use. BD showed significantly smaller volumes of the whole hippocampus (Cohen's d = -0.20), cornu ammonis (CA)1 (d = -0.18), CA2/3 (d = -0.11), CA4 (d = -0.19), molecular layer (d = -0.21), granule cell layer of dentate gyrus (d = -0.21), hippocampal tail (d = -0.10), subiculum (d = -0.15), presubiculum (d = -0.18), and hippocampal amygdala transition area (d = -0.17) compared to HC. Lithium users did not show volume differences compared to HC, while non-users did. Antipsychotics or antiepileptic use was associated with smaller volumes. In this largest study of hippocampal subfields in BD to date, we show widespread reductions in nine of 12 subfields studied. The associations were modulated by medication use and specifically the lack of differences between lithium users and HC supports a possible protective role of lithium in BD.

Intracranial and subcortical volumes in adolescents with early-onset psychosis: A multisite mega-analysis from the ENIGMA consortium.

Early-onset psychosis disorders are serious mental disorders arising before the age of 18 years. Here, we investigate the largest neuroimaging dataset, to date, of patients with early-onset psychosis and healthy controls for differences in intracranial and subcortical brain volumes. The sample included 263 patients with early-onset psychosis (mean age: 16.4 ± 1.4 years, mean illness duration: 1.5 ± 1.4 years, 39.2% female) and 359 healthy controls (mean age: 15.9 ± 1.7 years, 45.4% female) with magnetic resonance imaging data, pooled from 11 clinical cohorts. Patients were diagnosed with early-onset schizophrenia (n = 183), affective psychosis (n = 39), or other psychotic disorders (n = 41). We used linear mixed-effects models to investigate differences in intracranial and subcortical volumes across the patient sample, diagnostic subgroup and antipsychotic medication, relative to controls. We observed significantly lower intracranial (Cohen's d = -0.39) and hippocampal (d = -0.25) volumes, and higher caudate (d = 0.25) and pallidum (d = 0.24) volumes in patients relative to controls. Intracranial volume was lower in both early-onset schizophrenia (d = -0.34) and affective psychosis (d = -0.42), and early-onset schizophrenia showed lower hippocampal (d = -0.24) and higher pallidum (d = 0.29) volumes. Patients who were currently treated with antipsychotic medication (n = 193) had significantly lower intracranial volume (d = -0.42). The findings demonstrate a similar pattern of brain alterations in early-onset psychosis as previously reported in adult psychosis, but with notably low intracranial volume. The low intracranial volume suggests disrupted neurodevelopment in adolescent early-onset psychosis.

What we learn about bipolar disorder from large-scale neuroimaging: Findings and future directions from the ENIGMA Bipolar Disorder Working Group.

MRI-derived brain measures offer a link between genes, the environment and behavior and have been widely studied in bipolar disorder (BD). However, many neuroimaging studies of BD have been underpowered, leading to varied results and uncertainty regarding effects. The Enhancing Neuro Imaging Genetics through Meta-Analysis (ENIGMA) Bipolar Disorder Working Group was formed in 2012 to empower discoveries, generate consensus findings and inform future hypothesis-driven studies of BD. Through this effort, over 150 researchers from 20 countries and 55 institutions pool data and resources to produce the largest neuroimaging studies of BD ever conducted. The ENIGMA Bipolar Disorder Working Group applies standardized processing and analysis techniques to empower large-scale meta- and mega-analyses of multimodal brain MRI and improve the replicability of studies relating brain variation to clinical and genetic data. Initial BD Working Group studies reveal widespread patterns of lower cortical thickness, subcortical volume and disrupted white matter integrity associated with BD. Findings also include mapping brain alterations of common medications like lithium, symptom patterns and clinical risk profiles and have provided further insights into the pathophysiological mechanisms of BD. Here we discuss key findings from the BD working group, its ongoing projects and future directions for large-scale, collaborative studies of mental illness.

Longitudinal Structural Brain Changes in Bipolar Disorder: A Multicenter Neuroimaging Study of 1232 Individuals by the ENIGMA Bipolar Disorder Working Group.

BACKGROUND: Bipolar disorder (BD) is associated with cortical and subcortical structural brain abnormalities. It is unclear whether such alterations progressively change over time, and how this is related to the number of mood episodes. To address this question, we analyzed a large and diverse international sample with longitudinal magnetic resonance imaging (MRI) and clinical data to examine structural brain changes over time in BD. METHODS: Longitudinal structural MRI and clinical data from the ENIGMA (Enhancing Neuro Imaging Genetics through Meta Analysis) BD Working Group, including 307 patients with BD and 925 healthy control subjects, were collected from 14 sites worldwide. Male and female participants, aged 40 ± 17 years, underwent MRI at 2 time points. Cortical thickness, surface area, and subcortical volumes were estimated using FreeSurfer. Annualized change rates for each imaging phenotype were compared between patients with BD and healthy control subjects. Within patients, we related brain change rates to the number of mood episodes between time points and tested for effects of demographic and clinical variables. RESULTS: Compared with healthy control subjects, patients with BD showed faster enlargement of ventricular volumes and slower thinning of the fusiform and parahippocampal cortex (0.18

The long-term associations between parental behaviors, cognitive function and brain activation in adolescence.

Parenting behavior has a vital role in the development of the brain and cognitive abilities of offspring throughout childhood and adolescence. While positive and aggressive parenting behavior have been suggested to impact neurobiology in the form of abnormal brain activation in adolescents, little work has investigated the links between parenting behavior and the neurobiological correlates of cognitive performance during this age period. In the current longitudinal fMRI study, associations between parenting behaviors and cognitive performance and brain activation across mid- and late-adolescence were assessed. Observed measures of maternal aggressive and positive behavior were recorded in early adolescence (12 years) and correlated with fMRI activation and in-scanner behavioral scores on the multi-source interference task (MSIT) during mid- (16 years; 95 participants) and late-adolescence (19 years; 75 participants). There was a significant reduction in inhibitory-control-related brain activation in posterior parietal and cingulate cortices as participants transitioned from mid- to late-adolescence. Positive maternal behavior in early-adolescence was associated with lower activation in the left parietal and DLPFC during the MSIT in mid-adolescence, whereas maternal aggressive behavior was associated with longer reaction time to incongruent trials in late-adolescence. The study supports the notion that maternal behavior may influence subsequent neurocognitive development during adolescence.

The Influence of Maternal Parenting Style on the Neural Correlates of Emotion Processing in Children.

OBJECTIVE: The importance of parenting in influencing mental health outcomes, particularly depression, during childhood and adolescence is well known. However, the mechanisms are unclear. Emotion processing impairments in children are believed to be influenced by negative parenting behaviors and fundamental to depression. As such, investigating the association between parenting behavior and the neural underpinnings of emotion processing in children could provide fundamental clues as to the link between parenting and depression. METHOD: Eighty-six children (49 girls, mean age 10.1 years), as part of a longitudinal study, participated. Observational measures of maternal behavior were collected during 2 mother-child interactions. Children underwent functional magnetic resonance imaging while performing an implicit emotion-processing task, and measures of child internalizing symptoms were collected. RESULTS: Maternal negative behavior exhibited during an event-planning interaction was associated with decreased activation in the lingual gyrus in girls, whereas maternal negative behavior during a problem-solving interaction was associated with increased amygdala activation in the entire sample during processing of angry and fearful faces. Maternal communicative behavior during the 2 mother-child interactions was associated with increased activity in the bilateral middle orbitofrontal cortex in the entire sample. Negative behavior during the problem-solving interaction was associated with connectivity between the amygdala and superior parietal lobe. Brain activity/connectivity was not related to internalizing symptoms. CONCLUSION: Results suggest that, in children, maternal behavior could be associated with activity in brain regions involved in emotion processing. However, more research is needed to elucidate the link among parenting, emotion processing, and depressive symptoms in young people.

Differential effect of quetiapine and lithium on functional connectivity of the striatum in first episode mania.

Mood disturbances seen in first-episode mania (FEM) are linked to disturbed functional connectivity of the striatum. Lithium and quetiapine are effective treatments for mania but their neurobiological effects remain largely unknown. We conducted a single-blinded randomized controlled maintenance trial in 61 FEM patients and 30 healthy controls. Patients were stabilized for a minimum of 2 weeks on lithium plus quetiapine then randomly assigned to either lithium (serum level 0.6 mmol/L) or quetiapine (dosed up to 800 mg/day) treatment for 12 months. Resting-state fMRI was acquired at baseline, 3 months (patient only) and 12 months. The effects of treatment group, time and their interaction, on striatal functional connectivity were assessed using voxel-wise general linear modelling. At baseline, FEM patients showed reduced connectivity in the dorsal (p = 0.05) and caudal (p = 0.008) cortico-striatal systems when compared to healthy controls at baseline. FEM patients also showed increased connectivity in a circuit linking the ventral striatum with the medial orbitofrontal cortex, cerebellum and thalamus (p = 0.02). Longitudinally, we found a significant interaction between time and treatment group, such that lithium was more rapid, compared to quetiapine, in normalizing abnormally increased functional connectivity, as assessed at 3-month and 12-month follow-ups. The results suggest that FEM is associated with reduced connectivity in dorsal and caudal corticostriatal systems, as well as increased functional connectivity of ventral striatal systems. Lithium appears to act more rapidly than quetiapine in normalizing hyperconnectivity of the ventral striatum with the cerebellum. The study was registered on the Australian and New Zealand Clinical Trials Registry (ACTRN12607000639426). http://www.anzctr.org.au.

Amygdala Resting Connectivity Mediates Association Between Maternal Aggression and Adolescent Major Depression: A 7-Year Longitudinal Study.

OBJECTIVE: The parent-adolescent relationship is an important predictor of adolescent mental health, especially depressive disorders. This relationship is constructed in the context of maturing emotion neurobiology and could help shape such neurobiology in ways that are important for current and future mental health. Amygdala resting-state functional networks have been linked to depression, but whether such resting connectivity is associated with parent affective behaviors or acts as a salient mediator between parenting and risk for depressive disorder is unknown. METHOD: In the present study of 128 individuals, a 7-year longitudinal design was used to examine how observed maternal aggressive behavior during mother-adolescent interactions in early adolescence (12 years) predicted amygdala (whole and subregion)-based resting connectivity in mid adolescence (16 years). In 101 of those participants, whether altered amygdala resting-state connectivity mediated the association between maternal aggressive behavior and the first onset of major depressive disorder (MDD) in late adolescence (19 years) was analyzed. RESULTS: Maternal aggression was related to resting-state functional connectivity between the amygdala and right superior temporal-posterior insula-Heschl gyri, bilateral visual cortex, and left temporal and insula cortices (the latter being driven by the centromedial amygdala subregion; p < .001). Further, amygdala and centromedial amygdala connectivity with the temporal and insula cortices mediated the association between maternal aggression and late adolescent-onset MDD (CI 0.20 to 2.87; CI 0.13 to 2.40, respectively). CONCLUSION: These findings are consistent with previous literature documenting the importance of amygdala resting networks for adolescent depression but further suggest the importance of parental affective (particularly aggressive) behavior in the development of such functional connectivity patterns during this period of peak onset for mental health disorders.

Quetiapine v. lithium in the maintenance phase following a first episode of mania: randomised controlled trial.

BackgroundLithium and quetiapine are considered standard maintenance agents for bipolar disorder yet it is unclear how their efficacy compares with each other.AimsTo investigate the differential effect of lithium and quetiapine on symptoms of depression, mania, general functioning, global illness severity and quality of life in patients with recently stabilised first-episode mania.MethodMaintenance trial of patients with first-episode mania stabilised on a combination of lithium and quetiapine, subsequently randomised to lithium or quetiapine monotherapy (up to 800 mg/day) and followed up for 1 year. (Trial registration: Australian and New Zealand Clinical Trials Registry - ACTRN12607000639426.)ResultsIn total, 61 individuals were randomised. Within mixed-model repeated measures analyses, significant omnibus treatment × visit interactions were observed for measures of overall psychopathology, psychotic symptoms and functioning. Planned and post hoc comparisons further demonstrated the superiority of lithium treatment over quetiapine.ConclusionsIn people with first-episode mania treated with a combination of lithium and quetiapine, continuation treatment with lithium rather than quetiapine is superior in terms of mean levels of symptoms during a 1-year evolution.

Dopamine, fronto-striato-thalamic circuits and risk for psychosis.

A series of parallel, integrated circuits link distinct regions of prefrontal cortex with specific nuclei of the striatum and thalamus. Dysfunction of these fronto-striato-thalamic systems is thought to play a major role in the pathogenesis of psychosis. In this review, we examine evidence from human and animal investigations that dysfunction of a specific dorsal fronto-striato-thalamic circuit, linking the dorsolateral prefrontal cortex, dorsal (associative) striatum, and mediodorsal nucleus of the thalamus, is apparent across different stages of psychosis, including prior to the onset of a first episode, suggesting that it represents a candidate risk biomarker. We consider how abnormalities at distinct points in the circuit may give rise to the pattern of findings seen in patient populations, and how these changes relate to disruptions in dopamine, glutamate and GABA signaling.

A selective involvement of putamen functional connectivity in youth with internet gaming disorder.

Brain cortico-striatal circuits have consistently been implicated in the pathology of addiction related disorders. We applied a reliable seed-based analysis of the resting-state brain activity to comprehensively delineate the subdivisions of striatal functional connectivity implicated in internet gaming disorder. Among twelve right-handed male adolescents with internet gaming disorder and 11 right-handed and gender-matched healthy controls, we examined group differences in the functional connectivity of dorsal and ventral subdivisions of the caudate nucleus and putamen, as well as the association of these connectivity indices with behavioral measures of internet use. Adolescents with internet gaming disorder showed significantly reduced dorsal putamen functional connectivity with the posterior insula-parietal operculum. More time spent playing online games predicted significantly greater functional connectivity between the dorsal putamen and bilateral primary somatosensory cortices in adolescents with internet gaming disorder, and significantly lower functional connectivity between the dorsal putamen and bilateral sensorimotor cortices in healthy controls. The dorsal putamen functional connectivity was significantly and specifically different in adolescents with internet gaming disorder. The findings suggest a possible biomarker of internet gaming disorder.

Specific functional connectivity alterations of the dorsal striatum in young people with depression.

BACKGROUND: Altered basal ganglia function has been implicated in the pathophysiology of youth Major Depressive Disorder (MDD). Studies have generally focused on characterizing abnormalities in ventral "affective" corticostriatal loops supporting emotional processes. Recent evidence however, has implicated alterations in functional connectivity of dorsal "cognitive" corticostriatal loops in youth MDD. The contribution of dorsal versus ventral corticostriatal alterations to the pathophysiology of youth MDD remains unclear. METHODS: Twenty-one medication-free patients with moderate-to-severe MDD between the ages of 15 and 24 years old were matched with 21 healthy control participants. Using resting-state functional connectivity magnetic resonance imaging we systematically investigated connectivity of eight dorsal and ventral subdivisions of the striatum. Voxelwise statistical maps of each subregion's connectivity with other brain areas were compared between the depressed and control groups. RESULTS: Depressed youths showed alterations in functional connectivity that were confined to the dorsal corticostriatal circuit. Compared to controls, depressed patients showed increased connectivity between the dorsal caudate nucleus and ventrolateral prefrontal cortex bilaterally. Increased depression severity correlated with the magnitude of dorsal caudate connectivity with the right dorsolateral prefrontal cortex. There were no significant between-group differences in connectivity of ventral striatal regions. CONCLUSIONS: The results provide evidence that alterations in corticostriatal connectivity are evident at the early stages of the illness and are not a result of antidepressant treatment. Increased connectivity between the dorsal caudate, which is usually associated with cognitive processes, and the more affectively related ventrolateral prefrontal cortex may reflect a compensatory mechanism for dysfunctional cognitive-emotional processing in youth depression.

Selective augmentation of striatal functional connectivity following NMDA receptor antagonism: implications for psychosis.

The psychotomimetic effect of the N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine is thought to arise from a functional modulation of the brain's fronto-striato-thalamic (FST) circuits. Animal models suggest a pronounced effect on ventral 'limbic' FST systems, although recent work in patients with psychosis and high-risk individuals suggests specific alterations of dorsal 'associative' FST circuits. Here, we used functional magnetic resonance imaging to investigate the effects of a subanesthetic dose of ketamine on measures of functional connectivity as indexed by the temporal coherence of spontaneous neural activity in both dorsal and ventral FST circuits, as well as their symptom correlates. We adopted a placebo-controlled, double-blind, randomized, repeated-measures design in which 19 healthy participants received either an intravenous saline infusion or a racemic mixture of ketamine (100 ng/ml) separated by at least 1 week. Compared with placebo, ketamine increased functional connectivity between the dorsal caudate and both the thalamus and midbrain bilaterally. Ketamine additionally increased functional connectivity of the ventral striatum/nucleus accumbens and ventromedial prefrontal cortex. Both connectivity increases significantly correlated with the psychosis-like and dissociative symptoms under ketamine. Importantly, dorsal caudate connectivity with the ventrolateral thalamus and subthalamic nucleus showed inverse correlation with ketamine-induced symptomatology, pointing to a possible resilience role to disturbances in FST circuits. Although consistent with the role of FST in mediating psychosis, these findings contrast with previous research in clinical samples by suggesting that acute NMDAR antagonism may lead to psychosis-like experiences via a mechanism that is distinct from that implicated in frank psychotic illness.

Altered striatal functional connectivity in subjects with an at-risk mental state for psychosis.

Recent functional imaging work in individuals experiencing an at-risk mental state (ARMS) for psychosis has implicated dorsal striatal abnormalities in the emergence of psychotic symptoms, contrasting with earlier findings implicating the ventral striatum. Our aims here were to characterize putative dorsal and ventral striatal circuit-level abnormalities in ARMS individuals using resting-state functional magnetic resonance imaging (fMRI) and to investigate their relationship to positive psychotic symptoms. Resting-state fMRI was acquired in 74 ARMS subjects and 35 matched healthy controls. An established method for mapping ventral and dorsal striatal functional connectivity was used to examine corticostriatal functional integrity. Positive psychotic symptoms were assessed using the Comprehensive Assessment of At-Risk Mental State and the Positive and Negative Syndrome Scale. Compared with healthy controls, ARMS subjects showed reductions in functional connectivity between the dorsal caudate and right dorsolateral prefrontal cortex, left rostral medial prefrontal cortex, and thalamus, and between the dorsal putamen and left thalamic and lenticular nuclei. ARMS subjects also showed increased functional connectivity between the ventral putamen and the insula, frontal operculum, and superior temporal gyrus bilaterally. No differences in ventral striatal (ie, nucleus accumbens) functional connectivity were found. Altered functional connectivity in corticostriatal circuits were significantly correlated with positive psychotic symptoms. Together, these results suggest that risk for psychosis is mediated by a complex interplay of alterations in both dorsal and ventral corticostriatal systems.

Calcineurin is required for Leishmania major stress response pathways and for virulence in the mammalian host.

Leishmania parasites must adapt to elevated temperatures and other environmental stresses during infection of their mammalian hosts. How these environmental cues are sensed is poorly understood. In this study we show that calcium uptake is required for parasite thermotolerance at 34-37°C. To identify potential downstream targets of calcium influx, a Leishmania major mutant lacking the essential regulatory subunit (CnB) of the Ca(2+) /calmodulin-dependent serine/threonine-specific phosphatase, calcineurin, was generated. The Δcnb mutant grew as well as wild-type parasites at 27°C and differentiated normally to infective metacyclic promastigotes. However, Δcnb parasites lost viability when exposed to increased temperature (34°C) and were hypersensitive to endoplasmic reticulum and membrane stress, induced by tunicamycin and inhibitors of sterol and sphingolipid biosynthesis respectively. Δcnb promastigotes were internalized by macrophages, but their differentiation to the heat adapted amastigote stage was delayed and the resulting parasites failed to proliferate. Strikingly, the Δcnb parasites were completely cleared by susceptible BALB/c mice. Complementation of Δcnb parasites with CnB restored thermotolerance and infectivity in both macrophages and animal models. Our results suggest that Ca(2+) influx and calcineurin signalling are required for both early and long-term adaptive parasite responses to environmental stresses encountered in the mammalian host.