Ann Polcari

THE NEUROBIOLOGICAL CONSEQUENCES OF EARLY STRESS AND CHILDHOOD MALTREATMENT

Early severe stress and maltreatment produces a cascade of neurobiological events that have the potential to cause enduring changes in brain development. These changes occur on multiple levels, from neurohumoral (especially the hypothalamic-pituitary-adrenal [HPA] axis) to structural and functional. The major structural consequences of early stress include reduced size of the mid-portions of the corpus callosum and attenuated development of the left neocortex, hippocampus, and amygdala. Major functional consequences include increased electrical irritability in limbic structures and reduced functional activity of the cerebellar vermis. There are also gender differences in vulnerability and functional consequences. The neurobiological sequelae of early stress and maltreatment may play a significant role in the emergence of psychiatric disorders during development.

Developmental neurobiology of childhood stress and trauma.

Severe early stress and maltreatment produces a cascade of events that have the potential to alter brain development. The first stage of the cascade involves the stress-induced programming of the glucocorticoid, noradrenergic, and vasopressin-oxytocin stress response systems to augment stress responses. These neurohumors then produce effects on neurogenesis, synaptic overproduction and pruning, and myelination during specific sensitive periods. Major consequences include reduced size of the mid-portions of the corpus callosum; attenuated development of the left neocortex, hippocampus, and amygdala along with abnormal frontotemporal electrical activity; and reduced functional activity of the cerebellar vermis. These alterations, in turn, provide the neurobiological framework through which early abuse increases the risk of developing post-traumatic stress disorder (PTSD), depression, symptoms of attention-deficit/hyperactivity, borderline personality disorder, dissociative identity disorder, and substance abuse.

Preliminary Evidence for Sensitive Periods in the Effect of Childhood Sexual Abuse on Regional Brain Development

Volumetric MRI scans from 26 women with repeated episodes of childhood sexual abuse and 17 healthy female comparison subjects (ages 18-22 years) were analyzed for sensitive period effects on hippocampal and amygdala volume, frontal cortex gray matter volume and corpus callosum area. Hippocampal volume was reduced in association with childhood sexual abuse at ages 3-5 years and ages 11-13 years. Corpus callosum was reduced with childhood sexual abuse at ages 9-10 years, and frontal cortex was attenuated in subjects with childhood sexual abuse at ages 14-16 years. Brain regions have unique windows of vulnerability to the effects of traumatic stress.

Childhood maltreatment is associated with reduced volume in the hippocampal subfields CA3, dentate gyrus, and subiculum

Childhood maltreatment or abuse is a major risk factor for mood, anxiety, substance abuse, psychotic, and personality disorders, and it is associated with reduced adult hippocampal volume, particularly on the left side. Translational studies show that the key consequences of stress exposure on the hippocampus are suppression of neurogenesis in the dentate gyrus (DG) and dendritic remodeling in the cornu ammonis (CA), particularly the CA3 subfield. The hypothesis that maltreatment is associated with volume reductions in 3-T MRI subfields containing the DG and CA3 was assessed and made practical by newly released automatic segmentation routines for FreeSurfer. The sample consisted of 193 unmedicated right-handed subjects (38% male, 21.9 ± 2.1 y of age) selected from the community. Maltreatment was quantified using the Adverse Childhood Experience study and Childhood Trauma Questionnaire scores. The strongest associations between maltreatment and volume were observed in the left CA2-CA3 and CA4-DG subfields, and were not mediated by histories of major depression or posttraumatic stress disorder. Comparing subjects with high vs. low scores on the Childhood Trauma Questionnaire and Adverse Childhood Experience study showed an average volume reduction of 6.3% and 6.1% in the left CA2-CA3 and CA4-DG, respectively. Volume reductions in the CA1 and fimbria were 44% and 60% smaller than in the CA2-CA3. Interestingly, maltreatment was associated with 4.2% and 4.3% reductions in the left presubiculum and subiculum, respectively. These findings support the hypothesis that exposure to early stress in humans, as in other animals, affects hippocampal subfield development.

Functional deficits in basal ganglia of children with attention-deficit/hyperactivity disorder shown with functional magnetic resonance imaging relaxometry

Attention-deficit/hyperactivity disorder is a highly heritable and prevalent neuropsychiatric disorder estimated to affect 6% of school-age children. Its clinical hallmarks are inattention, hyperactivity and impulsivity, which often respond substantially to treatment with methylphenidate or dextroamphetamine. Etiological theories suggest a deficit in corticostriatal circuits, particularly those components modulated by dopamine. We developed a new functional magnetic resonance imaging procedure (T2 relaxometry) to indirectly assess blood volume in the striatum (caudate and putamen) of boys 6–12 years of age in steady-state conditions. Boys with attention-deficit/hyperactivity disorder had higher T2 relaxation time measures in the putamen bilaterally than healthy control subjects. Relaxation times strongly correlated with the childs capacity to sit still and his accuracy in accomplishing a computerized attention task. Daily treatment with methylphenidate significantly changed the T2 relaxation times in the putamen of children with attention-deficit/hyperactivity disorder, although the magnitude and direction of the effect was strongly dependent on the childs unmedicated activity state. There was a similar but nonsignificant trend in the right caudate. T2 relaxation time measures in thalamus did not differ significantly between groups, and were not affected by methylphenidate. Attention-deficit/hyperactivity disorder symptoms may be closely tied to functional abnormalities in the putamen, which is mainly involved in the regulation of motor behavior.

Preliminary Evidence for White Matter Tract Abnormalities in Young Adults Exposed to Parental Verbal Abuse

BACKGROUND Psychiatric sequelae of exposure to parental verbal abuse (PVA) appear to be comparable with that of nonfamilial sexual abuse and witnessing domestic violence. Diffusion tensor imaging (DTI) was used to ascertain whether PVA was associated with abnormalities in white matter (WM) tract integrity. METHODS 1271 healthy young adults were screened for exposure to childhood adversity. Diffusion tensor imaging was collected on 16 unmedicated subjects with history of high-level exposure to PVA but no other form of maltreatment (4 male/12 female subjects, mean age 21.9 +/- 2.4 years) and 16 healthy control subjects (5 male/11 female subjects, 21.0 +/- 1.6 years). Group differences in fractional anisotropy (FA), covaried by parental education and income, were assessed using tract-based spatial statistics (TBSS). RESULTS Three WM tract regions had significantly reduced FA: 1) arcuate fasciculus in left superior temporal gyrus, 2) cingulum bundle by the posterior tail of the left hippocampus, and 3) the left body of the fornix. Fractional anisotropy in these areas was strongly associated with average PVA scores (r(s) = -.701, -.801, -.524, respectively) and levels of maternal verbal abuse. Across groups, FA in region 1 correlated with verbal IQ and verbal comprehension index. Fractional anisotropy in region 2 was inversely associated with ratings of depression, dissociation, and limbic irritability. Fractional anisotropy in region 3 was inversely correlated with ratings of somatization and anxiety. CONCLUSIONS Exposure to PVA may be associated with alteration in the integrity of neural pathways with implications for language development and psychopathology.

Effects of Childhood Sexual Abuse on Neuropsychological and Cognitive Function in College Women

Twenty-six college women with a history of repeated childhood sexual abuse were recruited from the community and compared with 19 healthy female collegiate subjects on neurocognitive measures. Abused subjects showed increased response latency variability and diminished inhibitory capacity during a GO/NO-GO/STOP vigilance task. A strong association was found between duration of abuse and memory impairments. Math Scholastic Aptitude Test (SAT) scores were significantly lower in abused subjects when matched against comparison subjects and when compared to their own Verbal SAT scores. Childhood sexual abuse appears to be associated with a constellation of neuropsychological deficiencies even in a group of relatively healthy women.

Reduced prefrontal cortical gray matter volume in young adults exposed to harsh corporal punishment.

OBJECTIVE Harsh corporal punishment (HCP) during childhood is a chronic, developmental stressor associated with depression, aggression and addictive behaviors. Exposure to traumatic stressors, such as sexual abuse, is associated with alteration in brain structure, but nothing is known about the potential neurobiological consequences of HCP. The aim of this study was to investigate whether HCP was associated with discernible alterations in gray matter volume (GMV) using voxel-based morphometry (VBM). METHODS 1455 young adults (18-25 years) were screened to identify 23 with exposure to HCP (minimum 3 years duration, 12 episodes per year, frequently involving objects) and 22 healthy controls. High-resolution T1-weighted MRI datasets were obtained using Siemens 3 T trio scanner. RESULTS GMV was reduced by 19.1% in the right medial frontal gyrus (medial prefrontal cortex; MPFC, BA10) (P=0.037, corrected cluster level), by 14.5% in the left medial frontal gyrus (dorsolateral prefrontal cortex; DLPFC, BA9) (P=0.015, uncorrected cluster level) and by 16.9% in the right anterior cingulate gyrus (BA24) (P<0.001, uncorrected cluster level) of HCP subjects. There were significant correlations between GMV in these identified regions and performance IQ on the WAIS-III. CONCLUSIONS Exposing children to harsh HCP may have detrimental effects on trajectories of brain development. However, it is also conceivable that differences in prefrontal cortical development may increase risk of exposure to HCP.

Abnormal T2 relaxation time in the cerebellar vermis of adults sexually abused in childhood: potential role of the vermis in stress-enhanced risk for drug abuse

Recent studies suggest that childhood sexual abuse (CSA) elicits a cascade of neurohumoral events that affect brain development and is also a risk factor for the later development of substance abuse. We hypothesize that the cerebellar vermis may be a key region linking these observations. The vermis has a protracted ontogeny and a high density of glucocorticoid receptors, rendering it highly susceptible to early stress. The vermis modulates dopamine turnover in the accumbens and receives direct dopamine input through fibers with dopamine transporters. To test this hypothesis, steady-state functional magnetic resonance imaging (fMRI) (T2 relaxometry) was performed to assess resting blood flow in the vermis of 24 young adults (18-22 years) selected by screening from a large community sample. Eight subjects had a history of repeated CSA but were unmedicated and not under psychiatric care. Sixteen subjects were age-matched controls who had no personal or family history of Axis I psychiatric disorders. All subjects were screened to exclude known abnormalities affecting brain development, and any history of drug or alcohol abuse. CSA subjects had higher T2 relaxation time (T2-RT) than controls in the vermis but not in cerebral or cerebellar hemispheres. Vermal T2-RT correlated strongly with Limbic System Checklist (LSCL-33) ratings of temporal lobe epilepsy (TLE)-like symptomatology. From 537 prescreened young adults we found that their frequency of substance use was associated with a monotonic increase in LSCL-33 ratings and depression scores. Together these findings suggest that early trauma may interfere with the development of the vermis, and produce neuropsychiatric symptoms associated with drug use.

Childhood Sexual Abuse Is Associated with Reduced Gray Matter Volume in Visual Cortex of Young Women

BACKGROUND Childhood sexual abuse (CSA) has been associated with alterations in brain morphology using region of interest analyses that have focused on stress-sensitive target regions. This study was designed to ascertain the effects on gray matter volume (GMV) of exposure to CSA in healthy young adult college students selected based on exposure history regardless of psychiatric outcome. Voxel-based morphometry (VBM) provided unbiased delineation of the most significantly affected brain regions. METHODS High-resolution T1-weighted magnetic resonance imaging (MRI) datasets were obtained for 23 unmedicated female subjects with CSA and 14 healthy female control subjects of equivalent age and socioeconomic status with no history of trauma. Cortical surface-based analysis (FreeSurfer) was performed to verify VBM results. RESULTS Gray matter volume was reduced by 12.6% and 18.1% in right and left primary visual (V1) and visual association cortices of abused subjects. This reduction was directly related to duration of CSA before age 12. Gray matter volume of left and right V1 correlated with measure of visual memory (r = .353, p = .032 and r = .448, p = .005). Cortical surface-based analysis indicated that GMV of abused subjects was reduced in the left fusiform (p = .004), left middle occipital (p = .04), and right lingual (p = .002) gyri. CONCLUSIONS Early visual experience exerts a strong influence on the developing mammalian visual cortex. Present findings indicate that exposure to CSA may also affect the development of this region and are apparent even in a population of subjects who are sufficiently healthy to matriculate.