1
|
Piekarski DJ, Colich NL, Ho TC. The effects of puberty and sex on adolescent white matter development: A systematic review. Dev Cogn Neurosci 2023; 60:101214. [PMID: 36913887 PMCID: PMC10010971 DOI: 10.1016/j.dcn.2023.101214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 12/20/2022] [Accepted: 02/08/2023] [Indexed: 02/12/2023] Open
Abstract
Adolescence, the transition between childhood and adulthood, is characterized by rapid brain development in white matter (WM) that is attributed in part to rising levels in adrenal and gonadal hormones. The extent to which pubertal hormones and related neuroendocrine processes explain sex differences in WM during this period is unclear. In this systematic review, we sought to examine whether there are consistent associations between hormonal changes and morphological and microstructural properties of WM across species and whether these effects are sex-specific. We identified 90 (75 human, 15 non-human) studies that met inclusion criteria for our analyses. While studies in human adolescents show notable heterogeneity, results broadly demonstrate that increases in gonadal hormones across pubertal development are associated with macro- and microstructural changes in WM tracts that are consistent with the sex differences found in non-human animals, particularly in the corpus callosum. We discuss limitations of the current state of the science and recommend important future directions for investigators in the field to consider in order to advance our understanding of the neuroscience of puberty and to promote forward and backward translation across model organisms.
Collapse
Affiliation(s)
| | | | - Tiffany C Ho
- Department of Psychology, University of California, Los Angeles, United States.
| |
Collapse
|
2
|
Ou-Yang B, Hu Y, Fei XY, Cheng ST, Hang Y, Yang C, Cheng L. A meta-analytic study of the effects of early maternal separation on cognitive flexibility in rodent offspring. Dev Cogn Neurosci 2022; 56:101126. [PMID: 35751993 PMCID: PMC9243050 DOI: 10.1016/j.dcn.2022.101126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/27/2022] [Accepted: 06/13/2022] [Indexed: 11/03/2022] Open
Abstract
Adverse early life experiences, such as maternal separation, are associated with an increased risk for several mental health problems. Symptoms induced by maternal separation that mirror clinically relevant aspects of mental problems, such as cognitive inflexibility, open the possibility of testing putative therapeutics prior to clinical development. Although several animal (e.g., rodent) studies have evaluated the effects of early maternal separation on cognitive flexibility, no consistent conclusions have been drawn. To clarify this issue, in this study, a meta-analysis method was used to systematically explore the relationship between early maternal separation and cognitive flexibility in rodent offspring. Results indicate that early maternal separation could significantly impair cognitive flexibility in rodent offspring. Moderator analyses further showed that the relationship between early maternal separation and cognitive flexibility was not consistent in any case, but was moderated by variations in the experimental procedures, such as the deprivation levels, task characteristics, and rodent strains. These clarify the inconsistent effects of maternal separation on cognitive flexibility in rodents and help us better understand the association between early life adversity and cognitive development. Meta-analysis method was used to discuss the inconsistent effects of maternal separation on cognitive flexibility in rodent. Maternal separation was found to necessarily impair the cognitive flexibility in rodent. Variations in the experimental procedures moderated the relationship between maternal separation and cognitive flexibility. Further studies on environment-cognition associations in rodents should take experimental procedural factors into account.
Collapse
Affiliation(s)
- Bo Ou-Yang
- School of Psychology, Central China Normal University, Wuhan 430079, China
| | - Yue Hu
- School of Psychology, Central China Normal University, Wuhan 430079, China
| | - Xin-Yuan Fei
- School of Psychology, Central China Normal University, Wuhan 430079, China
| | - Sha-Te Cheng
- School of Psychology, Central China Normal University, Wuhan 430079, China
| | - Ying Hang
- School of Psychology, Central China Normal University, Wuhan 430079, China
| | - Chen Yang
- School of Psychology, Central China Normal University, Wuhan 430079, China
| | - Liang Cheng
- School of Psychology, Central China Normal University, Wuhan 430079, China.
| |
Collapse
|
3
|
Islam R, Kaffman A. White-Matter Repair as a Novel Therapeutic Target for Early Adversity. Front Neurosci 2021; 15:657693. [PMID: 33897364 PMCID: PMC8062784 DOI: 10.3389/fnins.2021.657693] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 03/17/2021] [Indexed: 12/13/2022] Open
Abstract
Early adversity (EA) impairs myelin development in a manner that persists later in life across diverse mammalian species including humans, non-human primates, and rodents. These observations, coupled with the highly conserved nature of myelin development suggest that animal models can provide important insights into the molecular mechanisms by which EA impairs myelin development later in life and the impact of these changes on network connectivity, cognition, and behavior. However, this area of translational research has received relatively little attention and no comprehensive review is currently available to address these issues. This is particularly important given some recent mechanistic studies in rodents and the availability of new agents to increase myelination. The goals of this review are to highlight the need for additional pre-clinical work in this area and to provide specific examples that demonstrate the potential of this work to generate novel therapeutic interventions that are highly needed.
Collapse
Affiliation(s)
- Rafiad Islam
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, United States
| | - Arie Kaffman
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, United States
| |
Collapse
|
4
|
Bozzatello P, Rocca P, Baldassarri L, Bosia M, Bellino S. The Role of Trauma in Early Onset Borderline Personality Disorder: A Biopsychosocial Perspective. Front Psychiatry 2021; 12:721361. [PMID: 34630181 PMCID: PMC8495240 DOI: 10.3389/fpsyt.2021.721361] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Accepted: 08/09/2021] [Indexed: 11/13/2022] Open
Abstract
The role of childhood trauma in the development of borderline personality disorder (BPD) in young age has long been studied. The most accurate theoretical models are multifactorial, taking into account a range of factors, including early trauma, to explain evolutionary pathways of BPD. We reviewed studies published on PubMed in the last 20 years to evaluate whether different types of childhood trauma, like sexual and physical abuse and neglect, increase the risk and shape the clinical picture of BPD. BPD as a sequela of childhood traumas often occurs with multiple comorbidities (e.g. mood, anxiety, obsessive-compulsive, eating, dissociative, addictive, psychotic, and somatoform disorders). In such cases it tends to have a prolonged course, to be severe, and treatment-refractory. In comparison with subjects who suffer from other personality disorders, patients with BPD experience childhood abuse more frequently. Adverse childhood experiences affect different biological systems (HPA axis, neurotransmission mechanisms, endogenous opioid systems, gray matter volume, white matter connectivity), with changes persisting into adulthood. A growing body of evidence is emerging about interaction between genes (e.g. FKBP5 polymorphisms and CRHR2 variants) and environment (physical and sexual abuse, emotional neglect).
Collapse
Affiliation(s)
- Paola Bozzatello
- Department of Neuroscience, School of Medicine, University of Turin, Turin, Italy
| | - Paola Rocca
- Department of Neuroscience, School of Medicine, University of Turin, Turin, Italy
| | - Lorenzo Baldassarri
- Department of Neuroscience, School of Medicine, University of Turin, Turin, Italy
| | - Marco Bosia
- Department of Neuroscience, School of Medicine, University of Turin, Turin, Italy
| | - Silvio Bellino
- Department of Neuroscience, School of Medicine, University of Turin, Turin, Italy
| |
Collapse
|
5
|
Barbaresi P, Mensà E, Sagrati A, Graciotti L. Postnatal development of the distribution of nitric oxide-producing neurons in the rat corpus callosum. Neurosci Res 2019; 151:15-30. [PMID: 30796928 DOI: 10.1016/j.neures.2019.02.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/15/2019] [Accepted: 02/14/2019] [Indexed: 11/18/2022]
Abstract
The postnatal development of nitric oxide (NO)-producing intracallosal neurons was studied in rats by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry from postnatal day 0 (P0) to P30. NADPH-d-positive neurons (NADPH-d+Ns) were detected already at P0, mainly in the rostral region of the corpus callosum (cc). Their location and the intensity of staining allowed them to be classified as type I NO-producing neurons. At P0, tufts of intensely labeled fibers, probably corresponding to the callosal septa described in the monkey and human cc, entered the ventral cc region and reached its dorsal portion. From P5, cell bodies and dendrites were often associated to blood vessels. The number of intracallosal NADPH-d+Ns rose in the first postnatal days to peak at P5, it declined until P10, and then remained almost constant until P30. Their size increased from P0 to P30, dramatically so (>65%) from P0 to P15. From P10 onward their distribution was adult-like, i.e. NADPH-d+Ns were more numerous in the lateral and intermediate portions of the cc and diminished close to the midline. In conjunction with previous data, these findings indicate that intracallosal NADPH-d+Ns could have a role in callosal axon guidance, myelination, refinement processes, and callosal blood flow regulation.
Collapse
Affiliation(s)
- Paolo Barbaresi
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, I-60020, Ancona, Italy.
| | - Emanuela Mensà
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, I-60020, Ancona, Italy; Department of Clinical and Molecular Sciences, Section of Experimental Pathology, Marche Polytechnic University, I-60020, Ancona, Italy
| | - Andrea Sagrati
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, I-60020, Ancona, Italy
| | - Laura Graciotti
- Department of Clinical and Molecular Sciences, Section of Experimental Pathology, Marche Polytechnic University, I-60020, Ancona, Italy
| |
Collapse
|
6
|
Teicher MH, Samson JA, Anderson CM, Ohashi K. The effects of childhood maltreatment on brain structure, function and connectivity. Nat Rev Neurosci 2016; 17:652-66. [DOI: 10.1038/nrn.2016.111] [Citation(s) in RCA: 785] [Impact Index Per Article: 98.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
|
7
|
Keeley RJ, Burger DK, Saucier DM, Iwaniuk AN. The size of non-hippocampal brain regions varies by season and sex in Richardson's ground squirrel. Neuroscience 2015; 289:194-206. [PMID: 25595988 DOI: 10.1016/j.neuroscience.2014.12.077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 11/29/2014] [Accepted: 12/18/2014] [Indexed: 11/19/2022]
Abstract
Sex- and season-specific modulation of hippocampal size and function is observed across multiple species, including rodents. Other non-hippocampal-dependent behaviors exhibit season and sex differences, and whether the associated brain regions exhibit similar variation with sex and season remains to be fully characterized. As such, we examined the brains of wild-caught Richardson's ground squirrels (RGS; Urocitellus richardsonii) for seasonal (breeding, non-breeding) and sex differences in the volumes of specific brain areas, including: total brain volume, corpus callosum (CC), anterior commissure (AC), medial prefrontal cortex (mPFC), total neocortex (NC), entorhinal cortex (EC), and superior colliculus (SC). Analyses of variance and covariance revealed significant interactions between season and sex for almost all areas studied, primarily resulting from females captured during the breeding season exhibiting larger volumes than females captured during the non-breeding season. This was observed for volumes of the AC, mPFC, NC, EC, and SC. Where simple main effects of season were observed for males (the NC and the SC), the volume advantage favoured males captured during the NBr season. Only two simple main effects of sex were observed: males captured in the non-breeding season had significantly larger total brain volume than females captured in the non-breeding season, and females captured during the breeding season had larger volumes of the mPFC and EC than males captured in the breeding season. These results indicate that females have more pronounced seasonal differences in brain and brain region sizes. The extent to which seasonal differences in brain region volumes vary with behaviour is unclear, but our data do suggest that seasonal plasticity is not limited to the hippocampus and that RGS is a useful mammalian species for understanding seasonal plasticity in an ecologically relevant context.
Collapse
Affiliation(s)
- R J Keeley
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4, Canada.
| | - D K Burger
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4, Canada
| | - D M Saucier
- Faculty of Science, University of Ontario Institute of Technology, Oshawa, ON L1H 7K4, Canada
| | - A N Iwaniuk
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4, Canada
| |
Collapse
|
8
|
Wei L, Hao J, Kaffman A. Early life stress inhibits expression of ribosomal RNA in the developing hippocampus. PLoS One 2014; 9:e115283. [PMID: 25517398 PMCID: PMC4269428 DOI: 10.1371/journal.pone.0115283] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 11/20/2014] [Indexed: 11/29/2022] Open
Abstract
Children that are exposed to abuse or neglect show abnormal hippocampal function. However, the developmental mechanisms by which early life stress (ELS) impairs normal hippocampal development have not been elucidated. Here we propose that exposure to ELS blunts normal hippocampal growth by inhibiting the availability of ribosomal RNA (rRNA). In support of this hypothesis, we show that the normal mouse hippocampus undergoes a growth-spurt during the second week of life, followed by a gradual decrease in DNA and RNA content that persists into adulthood. This developmental pattern is associated with accelerated ribosomal RNA (rRNA) synthesis during the second week of life, followed by a gradual decline in rRNA levels that continue into adulthood. Levels of DNA methylation at the ribosomal DNA (rDNA) promoter are lower during the second week of life compared to earlier development or adulthood. Exposure to brief daily separation (BDS), a mouse model of early life stress, increased DNA methylation at the ribosomal DNA promoter, decreased rRNA levels, and blunted hippocampal growth during the second week of life. Exposure to acute (3 hrs) maternal separation decreased rRNA and increased DNA methylation at the rDNA proximal promoter, suggesting that exposure to stress early in life can rapidly regulate the availability of rRNA levels in the developing hippocampus. Given the critical role that rRNA plays in supporting normal growth and development, these findings suggest a novel molecular mechanism to explain how stress early in life impairs hippocampus development in the mouse.
Collapse
Affiliation(s)
- Lan Wei
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Jin Hao
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Arie Kaffman
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut, United States of America
| |
Collapse
|
9
|
Sadowski RN, Wise LM, Park PY, Schantz SL, Juraska JM. Early exposure to bisphenol A alters neuron and glia number in the rat prefrontal cortex of adult males, but not females. Neuroscience 2014; 279:122-31. [PMID: 25193849 DOI: 10.1016/j.neuroscience.2014.08.038] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 07/30/2014] [Accepted: 08/25/2014] [Indexed: 11/26/2022]
Abstract
Previous work has shown that exposure to bisphenol A (BPA) during early development can alter sexual differentiation of the brain in rodents, although few studies have examined effects on areas of the brain associated with cognition. The current study examined if developmental BPA exposure alters the total number of neurons and glia in the medial prefrontal cortex (mPFC) in adulthood. Pregnant Long-Evans rats were orally exposed to 0, 4, 40, or 400-μg/kg BPA in corn oil throughout pregnancy. From postnatal days 1 to 9, pups were given daily oral doses of oil or BPA, at doses corresponding to those given during gestation. Brains were examined in adulthood, and the volume of layers 2/3 and layers 5/6 of the mPFC was parcellated. The density of neurons and glia in these layers was quantified stereologically with the optical disector, and density was multiplied by volume for each animal. Males exposed to 400-μg/kg BPA were found to have increased numbers of neurons and glia in layers 5/6. Although there were no significant effects of BPA in layers 2/3, the pattern of increased neuron number in males exposed to 400-μg/kg BPA was similar to that seen in layers 5/6. No effects of BPA were seen in females or in males exposed to the other doses of BPA. This study indicates that males are more susceptible to the long-lasting effects of BPA on anatomy of the mPFC, an area implicated in neurological disorders.
Collapse
Affiliation(s)
- R N Sadowski
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States
| | - L M Wise
- Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States
| | - P Y Park
- Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States
| | - S L Schantz
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States; Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States
| | - J M Juraska
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States; Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, IL 61820, United States.
| |
Collapse
|
10
|
Bernard K, Lind T, Dozier M. Neurobiological Consequences of Neglect and Abuse. HANDBOOK OF CHILD MALTREATMENT 2014. [DOI: 10.1007/978-94-007-7208-3_11] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
|
11
|
Bücker J, Muralidharan K, Torres IJ, Su W, Kozicky J, Silveira LE, Bond DJ, Honer WG, Kauer-Sant'anna M, Lam RW, Yatham LN. Childhood maltreatment and corpus callosum volume in recently diagnosed patients with bipolar I disorder: data from the Systematic Treatment Optimization Program for Early Mania (STOP-EM). J Psychiatr Res 2014; 48:65-72. [PMID: 24183241 DOI: 10.1016/j.jpsychires.2013.10.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/29/2013] [Accepted: 10/10/2013] [Indexed: 01/11/2023]
Abstract
Childhood trauma (CT) has been associated with abnormalities in the corpus callosum (CC). Decreased CC volumes have been reported in children and adolescents with trauma as well as adults with CT compared to healthy controls. CC morphology is potentially susceptible to the effects of Bipolar Disorder (BD) itself. Therefore, we evaluated the relationship between CT and CC morphology in BD. We using magnetic resonance imaging in 53 adults with BD recently recovered from their first manic episode, with (n = 23) and without (n = 30) CT, defined using the Childhood Trauma Questionnaire (CTQ) and 16 healthy controls without trauma. ANCOVA was performed with age, gender and intracranial volume as covariates in order to evaluate group differences in CC volume. The total CC volume was found to be smaller in BD patients with trauma compared to BD patients without trauma (p < .05). The differences were more pronounced in the anterior region of the CC. There was a significant negative correlation between CTQ scores and total CC volume in BD patients with trauma (p = .01). We did not find significant differences in the CC volume of patients with/without trauma compared to the healthy subjects. Our sample consists of patients recovered from a first episode of mania and are early in the course of illness and reductions in CC volume may occur late in the course of BD. It might mean there may be two sources of CC volume reduction in these patients: the reduction due to trauma, and the further reduction due to the illness.
Collapse
Affiliation(s)
- J Bücker
- Department of Psychiatry, University of British Columbia, Vancouver, Canada; Bipolar Disorder Program and Laboratory of Molecular Psychiatry, National Institute for Translational Medicine, INCT-TM, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Rao DB, Little PB, Sills R. Subsite awareness in neuropathology evaluation of National Toxicology Program (NTP) studies: a review of select neuroanatomical structures with their functional significance in rodents. Toxicol Pathol 2013; 42:487-509. [PMID: 24135464 PMCID: PMC3965620 DOI: 10.1177/0192623313501893] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This review article is designed to serve as an introductory guide in neuroanatomy for toxicologic pathologists evaluating general toxicity studies. The article provides an overview of approximately 50 neuroanatomical subsites and their functional significance across 7 transverse sections of the brain. Also reviewed are 3 sections of the spinal cord, cranial and peripheral nerves (trigeminal and sciatic, respectively), and intestinal autonomic ganglia. The review is limited to the evaluation of hematoxylin and eosin-stained tissue sections, as light microscopic evaluation of these sections is an integral part of the first-tier toxicity screening of environmental chemicals, drugs, and other agents. Prominent neuroanatomical sites associated with major neurological disorders are noted. This guide, when used in conjunction with detailed neuroanatomic atlases, may aid in an understanding of the significance of functional neuroanatomy, thereby improving the characterization of neurotoxicity in general toxicity and safety evaluation studies.
Collapse
Affiliation(s)
- Deepa B. Rao
- Integrated Laboratory Systems, Inc., Research Triangle Park, North Carolina
| | - Peter B. Little
- Consultant, Experimental Pathology Laboratories, Inc., Research Triangle Park, North Carolina
| | - Robert Sills
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| |
Collapse
|
13
|
Interhemispheric functional connectivity following prenatal or perinatal brain injury predicts receptive language outcome. J Neurosci 2013; 33:5612-25. [PMID: 23536076 DOI: 10.1523/jneurosci.2851-12.2013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Early brain injury alters both structural and functional connectivity between the cerebral hemispheres. Despite increasing knowledge on the individual hemispheric contributions to recovery from such injury, we know very little about how their interactions affect this process. In the present study, we related interhemispheric structural and functional connectivity to receptive language outcome following early left hemisphere stroke. We used functional magnetic resonance imaging to study 14 people with neonatal brain injury, and 25 age-matched controls during passive story comprehension. With respect to structural connectivity, we found that increased volume of the corpus callosum predicted good receptive language outcome, but that this is not specific to people with injury. In contrast, we found that increased posterior superior temporal gyrus interhemispheric functional connectivity during story comprehension predicted better receptive language performance in people with early brain injury, but worse performance in typical controls. This suggests that interhemispheric functional connectivity is one potential compensatory mechanism following early injury. Further, this pattern of results suggests refinement of the prevailing notion that better language outcome following early left hemisphere injury relies on the contribution of the contralesional hemisphere (i.e., the "right-hemisphere-take-over" theory). This pattern of results was also regionally specific; connectivity of the angular gyrus predicted poorer performance in both groups, independent of brain injury. These results present a complex picture of recovery, and in some cases, such recovery relies on increased cooperation between the injured hemisphere and homologous regions in the contralesional hemisphere, but in other cases, the opposite appears to hold.
Collapse
|
14
|
Moore S, Patel R, Hannsun G, Yang J, Tiwari-Woodruff SK. Sex chromosome complement influences functional callosal myelination. Neuroscience 2013; 245:166-78. [PMID: 23597832 DOI: 10.1016/j.neuroscience.2013.04.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 04/01/2013] [Accepted: 04/02/2013] [Indexed: 12/29/2022]
Abstract
In addition to androgen differences between males and females, there are genetic differences that are caused by unequal dosage of sex chromosome genes. Using the cuprizone-induced demyelination model, we recently showed that surgical gonadectomy of adult mice resulted in decreased normal myelination and remyelination compared to gonadally intact animals, suggesting a supporting role for sex hormones in the maintenance of myelination. However, inherent sex differences in normal myelination and remyelination persisted even after gonadectomy, with males consistently remyelinating to a lesser extent relative to normal myelination as assayed by axon conduction and immunohistochemistry. This suggests a potential role for the sex chromosome complement in mediating the differential rates of remyelination observed in males and females. The present study focuses on the impact that sex chromosomes might have on these myelination differences. Making use of the four core-genotype mice and cuprizone-diet induced demyelination/remyelination paradigm, our results demonstrate sex chromosome-mediated asymmetry between XX and XY mice. The rate of functional remyelination following cuprizone diet-induced callosal demyelination in four core-genotype mice is attenuated in XY compared to XX animals of both gonadal sexes. Importantly, this difference arises only in the absence of circulating sex hormones following gonadectomy and confirms the role of sex hormones in the remyelination process reported earlier by our group. Because a genotype-mediated difference only arises following gonadectomy, the chromosomal contribution to myelination and remyelination is subtle yet significant. To explain this difference, we propose a possible asymmetry in the expression of myelination-related genes in XX vs. XY mice that needs to be investigated in future studies.
Collapse
Affiliation(s)
- S Moore
- Multiple Sclerosis Program, Department of Neurology, School of Medicine, University of California, Los Angeles, CA 90095, USA
| | | | | | | | | |
Collapse
|
15
|
Cory-Slechta DA, Weston D, Liu S, Allen JL. Brain hemispheric differences in the neurochemical effects of lead, prenatal stress, and the combination and their amelioration by behavioral experience. Toxicol Sci 2013; 132:419-30. [PMID: 23358193 DOI: 10.1093/toxsci/kft015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Brain lateralization, critical to mediation of cognitive functions and to "multitasking," is disrupted in conditions such as attention deficit disorder and schizophrenia. Both low-level lead (Pb) exposure and prenatal stress (PS) have been associated with mesocorticolimbic system-mediated executive-function cognitive and attention deficits. Mesocorticolimbic systems demonstrate significant laterality. Thus, altered brain lateralization could play a role in this behavioral toxicity. This study examined laterality of mesocorticolimbic monoamines (frontal cortex, nucleus accumbens, striatum, midbrain) and amino acids (frontal cortex) in male and female rats subjected to lifetime Pb exposure (0 or 50 ppm in drinking water), PS (restraint stress on gestational days 16-17), or the combination with and without repeated learning behavioral experience. Control males exhibited prominent laterality, particularly in midbrain and also in frontal cortex and striatum; females exhibited less laterality, and this was primarily striatal. Lateralized Pb ± PS induced neurotransmitter changes were assessed only in males because of limited sample sizes of Pb + PS females. In males, Pb ± PS changes occurred in left hemisphere of frontal cortex and right hemisphere of midbrain. Behavioral experience modified the laterality of Pb ± PS-induced neurotransmitter changes in a region-dependent manner. Notably, behavioral experience eliminated Pb ± PS neurotransmitter changes in males. These findings underscore the critical need to evaluate both sexes and brain hemispheres for the mechanistic understanding of sex-dependent differences in neuro- and behavioral toxicity. Furthermore, assessment of central nervous system mechanisms in the absence of behavioral experience, shown here for males, may constitute less relevant models of human health effects.
Collapse
Affiliation(s)
- Deborah A Cory-Slechta
- Department of Environmental Medicine, University of Rochester School of Medicine, Rochester, New York 14642, USA.
| | | | | | | |
Collapse
|
16
|
Powell JL, Kemp GJ, Roberts N, García-Finaña M. Sulcal morphology and volume of Broca's area linked to handedness and sex. BRAIN AND LANGUAGE 2012; 121:206-218. [PMID: 22482924 DOI: 10.1016/j.bandl.2012.03.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 02/28/2012] [Accepted: 03/07/2012] [Indexed: 05/31/2023]
Abstract
We investigated the effect of handedness and sex on: (i) sulcal contours defining PO and PTR and (ii) volume estimates of PO and PTR subfields in 40 left- and 42 right-handers. Results show an effect of handedness on discontinuity of the inferior frontal sulcus (IFS: P<0.01). Discontinuity of IFS was observed in: 43% left- and 62% right hemispheres in right-handers and in 65% left- and 48% right-hemispheres in left-handers. PO volume asymmetry was rightward in left-handed males (P=0.007) and females (P=0.02), showed a leftward trend in right-handed males (P=0.06), and was non-asymmetrical in right-handed females (P=0.96, i.e. left- and right-hemisphere PO volumes did not differ significantly). PO volume asymmetry in males differed significantly between handedness groups (P=0.001). Findings indicate a high degree of variability in the sulcal contours of PO and PTR and volume asymmetry of PO: the factors sex and handedness can explain some of this variability.
Collapse
Affiliation(s)
- Joanne L Powell
- Magnetic Resonance and Image Analysis Research Centre (MARIARC), University of Liverpool, UK.
| | | | | | | |
Collapse
|
17
|
Krizman J, Skoe E, Kraus N. Sex differences in auditory subcortical function. Clin Neurophysiol 2012; 123:590-7. [PMID: 21855407 PMCID: PMC3226913 DOI: 10.1016/j.clinph.2011.07.037] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 06/15/2011] [Accepted: 07/07/2011] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Sex differences have been demonstrated in the peripheral auditory system as well as in higher-level cognitive processing. Here, we aimed to determine if the subcortical response to a complex auditory stimulus is encoded differently between the sexes. METHODS Using electrophysiological techniques, we assessed the auditory brainstem response to a synthesized stop-consonant speech syllable [da] in 76 native-English speaking, young adults (38 female). Timing and frequency components of the response were compared between males and females to determine which aspects of the response are affected by sex. RESULTS A dissimilarity between males and females was seen in the neural response to the components of the speech stimulus that change rapidly over time; but not in the slower changing, lower frequency information in the stimulus. We demonstrate that, in agreement with the click-evoked brainstem response, females have earlier peaks relative to males in the subcomponents of the response representing the onset of the speech sound. In contrast, the response peaks comprising the frequency-following response, which encode the fundamental frequency (F(0)) of the stimulus, as well as the spectral amplitude of the response to the F(0), is not affected by sex. Notably, the higher-frequency elements of the speech syllable are encoded differently between males and females, with females having greater representation of spectrotemporal information for frequencies above the F(0). CONCLUSIONS Our results provide a baseline for interpreting the higher incidence of language impairment (e.g. dyslexia, autism, specific language impairment) in males, and the subcortical deficits associated with these disorders. SIGNIFICANCE These results parallel the subcortical encoding patterns that are documented for good and poor readers in that poor readers differ from good readers on encoding fast but not slow components of speech. This parallel may thus help to explain the higher incidence of reading impairment in males compared to females.
Collapse
Affiliation(s)
- Jennifer Krizman
- Auditory Neuroscience Laboratory, Department of Communication Sciences, Northwestern University, Evanston, IL 60208, USA
| | | | | |
Collapse
|
18
|
Early life stress inhibits expression of a novel innate immune pathway in the developing hippocampus. Neuropsychopharmacology 2012; 37:567-80. [PMID: 21993208 PMCID: PMC3242319 DOI: 10.1038/npp.2011.239] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Childhood maltreatment represents a major risk factor for the development of numerous childhood psychopathologies that in many cases linger as chronic mental illnesses in adulthood. Exposing rodents or non-human primates to early life stress increases anxiety-like behaviors and impairs cognitive function in adulthood, suggesting that animal models may provide important insights into parallel developmental processes in humans. Using an unbiased genomic screen, we found that expression of lipopolysaccharide binding protein (LBP), a member of the innate immune system, is dramatically decreased in the hippocampus of pups exposed to early life stress. LBP levels peak in the normally developing hippocampus at a period of intense synaptic pruning, during which LBP is colocalized with the synaptic marker PSD95 and is found in close proximity to processes of microglia cells. Expression of LBP declines to low levels seen in adulthood at around postnatal day 30. Importantly, 30-day-old LBP knockout (k.o.) mice show increased spine density and abnormal spine morphology, suggesting that peak levels of LBP during the second and third weeks of life are necessary for normal synaptic pruning in the hippocampus. Finally, LBP k.o. mice show impaired hippocampal-dependent memory and increased anxiety-like behaviors in a manner that resembles that seen in animals exposed to early life stress. These findings describe a novel role for LBP in normal hippocampal development and raise the possibility that at least some of the behavioral sequelae of early life stress are mediated by reduced expression of LBP during a critical period of neurodevelopment.
Collapse
|
19
|
Vigil P, Orellana RF, Cortés ME, Molina CT, Switzer BE, Klaus H. Endocrine modulation of the adolescent brain: a review. J Pediatr Adolesc Gynecol 2011; 24:330-7. [PMID: 21514192 DOI: 10.1016/j.jpag.2011.01.061] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Accepted: 01/28/2011] [Indexed: 12/31/2022]
Abstract
Neurophysiological and behavioral development is particularly complex in adolescence. Youngsters experience strong emotions and impulsivity, reduced self-control, and preference for actions which offer immediate rewards, among other behavioral patterns. Given the growing interest in endocrine effects on adolescent central nervous system development and their implications on later stages of life, this article reviews the effects of gonadal steroid hormones on the adolescent brain. These effects are classified as organizational, the capacity of steroids to determine nervous system structure during development, and activational, the ability of steroids to modify nervous activity to promote certain behaviors. During transition from puberty to adolescence, steroid hormones trigger various organizational phenomena related to structural brain circuit remodelling, determining adult behavioral response to steroids or sensory stimuli. These changes account for most male-female sexual dimorphism. In this stage sex steroids are involved in the main functional mechanisms responsible for organizational changes, namely myelination, neural pruning, apoptosis, and dendritic spine remodelling, activated only during embryonic development and during the transition from puberty to adolescence. This stage becomes a critical organizational window when the appropriately and timely exerted functions of steroid hormones and their interaction with some neurotransmitters on adolescent brain development are fundamental. Thus, understanding the phenomena linking steroid hormones and adolescent brain organization is crucial in the study of teenage behavior and in later assessment and treatment of anxiety, mood disorders, and depression. Adolescent behavior clearly evidences a stage of brain development influenced for the most part by steroid hormones.
Collapse
Affiliation(s)
- Pilar Vigil
- Unidad de Reproducción y Desarrollo, Departamento de Fisiología, Facultad de Ciencias Biológicas, Santiago, Pontificia Universidad Católica de Chile, Chile.
| | | | | | | | | | | |
Collapse
|
20
|
Belsky J, de Haan M. Annual Research Review: Parenting and children's brain development: the end of the beginning. J Child Psychol Psychiatry 2011; 52:409-28. [PMID: 20626527 DOI: 10.1111/j.1469-7610.2010.02281.x] [Citation(s) in RCA: 228] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
After questioning the practical significance of evidence that parenting influences brain development - while highlighting the scientific importance of such work for understanding how family experience shapes human development - this paper reviews evidence suggesting that brain structure and function are 'chiselled' by parenting. Although the generalisability of most findings is limited due to a disproportionate, but understandable focus on clinical samples (e.g., maltreated children with post-traumatic stress disorder (PTSD)) and causal inferences are difficult to draw because of the observational nature of most of the evidence, it is noteworthy that some work with community samples and very new experimental work (e.g., parent training) suggests that tentative conclusions regarding effects of parenting on the developing brain may well be substantiated in future research. Such efforts should focus on parenting in the normal range, experimental manipulations of parenting, differential susceptibility to parenting effects and pathway models linking parenting to brain development and, thereby, to behavioural development. Research on parenting and children's brain development may be regarded as at 'the end of the beginning'.
Collapse
Affiliation(s)
- Jay Belsky
- Institute for Study of Children, Families and Social Issues, Birkbeck University of London, UK.
| | | |
Collapse
|
21
|
Adolescent females exposed to child maltreatment exhibit atypical EEG coherence and psychiatric impairment: Linking early adversity, the brain, and psychopathology. Dev Psychopathol 2010; 22:419-32. [DOI: 10.1017/s0954579410000155] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractAlthough the relation between child maltreatment and psychiatric impairment is well documented and preliminary evidence has linked child maltreatment with aberrant cortical connectivity of the left hemisphere, no investigations have attempted to examine these relations in the same study. Here, we examined the links among early adversity, brain connectivity, and functional outcomes. We collected resting regional EEG intra- and interhemispheric α-band (7.5–12.5 Hz) coherence and measures of general psychiatric impairment from a cohort of 38 adolescent females exposed to child maltreatment (Mage = 14.47) and 24 adolescent females not exposed to child maltreatment (Mage = 14.00). Maltreated youths exhibited more left hemisphere EEG coherence than the control youths, suggesting a suboptimal organization of cortical networks. Maltreated participants also showed reduced frontal (anterior) interhemispheric coherence. These differences in brain circuitry remained statistically significant even after controlling for group differences in pubertal status and socioeconomic status. Measures of functional brain connectivity were associated with several subtypes of abuse and neglect. It was important that atypical left hemisphere EEG coherencemediatedthe effects of child maltreatment on levels of psychiatric impairment. The findings are discussed in the context of models linking early adversity to brain function and psychopathology.
Collapse
|
22
|
Wei L, David A, Duman RS, Anisman H, Kaffman A. Early life stress increases anxiety-like behavior in Balb c mice despite a compensatory increase in levels of postnatal maternal care. Horm Behav 2010; 57:396-404. [PMID: 20096699 PMCID: PMC2849915 DOI: 10.1016/j.yhbeh.2010.01.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Revised: 01/09/2010] [Accepted: 01/12/2010] [Indexed: 11/27/2022]
Abstract
A better understanding of the molecular and cellular mechanisms by which early life stress (ELS) modifies brain development and adult behavior is necessary for diagnosing and treating psychopathology associated with exposure to ELS. For historical reasons, most of the work in rodents has been done in rats and attempts to establish robust and reproducible paradigms in the mouse have proven to be challenging. Here we show that under normal rearing conditions, increased levels of postnatal maternal care are associated with a decrease in anxiety-like behavior in BALB/cByj offspring. Brief daily pup-dam separation (BDS) during the postnatal period was associated with increased postnatal maternal care but was surprisingly associated with increased anxiety-like behavior in adult offspring, providing the first example in which offspring receiving higher levels of postnatal maternal care are more anxious in adulthood. Plasma corticosterone levels were elevated in BDS pups even 3 h after the pups were reunited with the dam, suggesting that this paradigm represents a form of early life stress. We also show that levels of total RNA and DNA in the hippocampus reach a peak at postnatal day 14 and that exposure to BDS seems to inhibit this developmental growth spurt. We propose that exposure to stress during the postnatal period overrides the ability of high levels of postnatal maternal care to program anxiety-like behavior by inhibiting the normal growth spurt that characterizes this period.
Collapse
Affiliation(s)
- Lan Wei
- Abraham Ribicoff Labs, Department of Psychiatry, Yale University School of Medicine, 34 Park Street, CMHC, rm S310, New Haven CT 06517, USA
| | | | | | | | | |
Collapse
|
23
|
Sex-related differences in precocious mathematical reasoning ability: Not illusory, not easily explained. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00049670] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
|
24
|
|
25
|
|
26
|
|
27
|
|
28
|
|
29
|
|
30
|
|
31
|
|
32
|
|
33
|
|
34
|
Sex differences in mathematical reasoning ability in intellectually talented preadolescents: Their nature, effects, and possible causes. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00049244] [Citation(s) in RCA: 359] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
AbstractSeveral hundred thousand intellectually talented 12-to 13-year-olds have been tested nationwide over the past 16 years with the mathematics and verbal sections of the Scholastic Aptitude Test (SAT). Although no sex differences in verbal ability have been found, there have been consistent sex differences favoring males in mathematical reasoning ability, as measured by the mathematics section of the SAT (SAT-M). These differences are most pronounced at the highest levels of mathematical reasoning, they are stable over time, and they are observed in other countries as well. The sex difference in mathematical reasoning ability can predict subsequent sex differences in achievement in mathematics and science and is therefore of practical importance. To date a primarily environmental explanation for the difference in ability has not received support from the numerous studies conducted over many years by the staff of Study of Mathematically Precocious Youth (SMPY) and others. We have studied some of the classical environmental hypotheses: attitudes toward mathematics, perceived usefulness of mathematics, confidence, expectations/ encouragement from parents and others, sex-typing, and differential course-taking. In addition, several physiological correlates of extremely high mathematical reasoning ability have been identified (left-handedness, allergies, myopia, and perhaps bilateral representation of cognitive functions and prenatal hormonal exposure). It is therefore proposed that the sex difference in SAT-M scores among intellectually talented students, which may be related to greater male variability, results from both environmental and biological factors.
Collapse
|
35
|
|
36
|
|
37
|
|
38
|
|
39
|
|
40
|
|
41
|
|
42
|
|
43
|
|
44
|
|
45
|
|
46
|
|
47
|
|
48
|
|
49
|
Chura LR, Lombardo MV, Ashwin E, Auyeung B, Chakrabarti B, Bullmore ET, Baron-Cohen S. Organizational effects of fetal testosterone on human corpus callosum size and asymmetry. Psychoneuroendocrinology 2010; 35:122-32. [PMID: 19833443 DOI: 10.1016/j.psyneuen.2009.09.009] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 09/09/2009] [Accepted: 09/10/2009] [Indexed: 10/20/2022]
Abstract
Previous theory and research in animals has identified the critical role that fetal testosterone (FT) plays in organizing sexually dimorphic brain development. However, to date there are no studies in humans directly testing the organizational effects of FT on structural brain development. In the current study we investigated the effects of FT on corpus callosum size and asymmetry. High-resolution structural magnetic resonance images (MRI) of the brain were obtained on 28 8-11-year-old boys whose exposure to FT had been previously measured in utero via amniocentesis conducted during the second trimester. Although there was no relationship between FT and midsaggital corpus callosum size, increasing FT was significantly related to increasing rightward asymmetry (e.g., Right>Left) of a posterior subsection of the callosum, the isthmus, that projects mainly to parietal and superior temporal areas. This potential organizational effect of FT on rightward callosal asymmetry may be working through enhancing the neuroprotective effects of FT and result in an asymmetric distribution of callosal axons. We suggest that this possible organizational effect of FT on callosal asymmetry may also play a role in shaping sexual dimorphism in functional and structural brain development, cognition, and behavior.
Collapse
Affiliation(s)
- Lindsay R Chura
- Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK.
| | | | | | | | | | | | | |
Collapse
|
50
|
Markham JA, Herting MM, Luszpak AE, Juraska JM, Greenough WT. Myelination of the corpus callosum in male and female rats following complex environment housing during adulthood. Brain Res 2009; 1288:9-17. [PMID: 19596280 DOI: 10.1016/j.brainres.2009.06.087] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Revised: 06/24/2009] [Accepted: 06/26/2009] [Indexed: 02/08/2023]
Abstract
Myelination is an important process in brain development, and delays or abnormalities in this process have been associated with a number of conditions including autism, developmental delay, attention deficit disorder, and schizophrenia. Myelination can be sensitive to developmental experience; however, although the adult brain remains highly plastic, it is unknown whether myelination continues to be sensitive to experience during adulthood. Male and female rats were socially housed until four months of age, at which time they were moved into either a complex or "enriched" environment (EC) or an isolated condition (IC). Although the area of the splenium (posterior 20% of the callosum, which contains axons from visual cortical neurons) increased by about 10% following two months of EC housing, the area occupied by myelinated axons was not influenced by adult housing condition. Instead, it was the area occupied by glial cell processes and unmyelinated axons which significantly increased following EC housing. Neither the size nor the myelin content of the genu (anterior 15% of the callosum) was sensitive to manipulations of adult housing condition, but males had more area occupied by myelinated axons in both callosal regions. Finally, the inability of two months of complex environment housing during adulthood to impact the number of myelinated axons in the splenium was confirmed in a subset of animals using quantitative electron microscopy. We conclude that the sensitivity of myelination to experience is reduced in adulthood relative to development in both sexes.
Collapse
Affiliation(s)
- Julie A Markham
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
| | | | | | | | | |
Collapse
|