Corpus Callosum: Broad plate of dense myelinated fibers that reciprocally interconnect regions of the cortex in all lobes with corresponding regions of the opposite hemisphere. The corpus callosum is located deep in the longitudinal fissure.Agenesis of Corpus Callosum: Birth defect that results in a partial or complete absence of the CORPUS CALLOSUM. It may be isolated or a part of a syndrome (e.g., AICARDI'S SYNDROME; ACROCALLOSAL SYNDROME; ANDERMANN SYNDROME; and HOLOPROSENCEPHALY). Clinical manifestations include neuromotor skill impairment and INTELLECTUAL DISABILITY of variable severity.Acrocallosal Syndrome: Autosomal recessive syndrome characterized by hypogenesis or agenesis of CORPUS CALLOSUM. Clinical features include MENTAL RETARDATION; CRANIOFACIAL ABNORMALITIES; digital malformations, and growth retardation.Corpus Luteum: The yellow body derived from the ruptured OVARIAN FOLLICLE after OVULATION. The process of corpus luteum formation, LUTEINIZATION, is regulated by LUTEINIZING HORMONE.Anisotropy: A physical property showing different values in relation to the direction in or along which the measurement is made. The physical property may be with regard to thermal or electric conductivity or light refraction. In crystallography, it describes crystals whose index of refraction varies with the direction of the incident light. It is also called acolotropy and colotropy. The opposite of anisotropy is isotropy wherein the same values characterize the object when measured along axes in all directions.Nerve Fibers, Myelinated: A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.Diffusion Tensor Imaging: The use of diffusion ANISOTROPY data from diffusion magnetic resonance imaging results to construct images based on the direction of the faster diffusing molecules.Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Cuprizone: Copper chelator that inhibits monoamine oxidase and causes liver and brain damage.Diffusion Magnetic Resonance Imaging: A diagnostic technique that incorporates the measurement of molecular diffusion (such as water or metabolites) for tissue assessment by MRI. The degree of molecular movement can be measured by changes of apparent diffusion coefficient (ADC) with time, as reflected by tissue microstructure. Diffusion MRI has been used to study BRAIN ISCHEMIA and tumor response to treatment.Anodontia: Congenital absence of the teeth; it may involve all (total anodontia) or only some of the teeth (partial anodontia, hypodontia), and both the deciduous and the permanent dentition, or only teeth of the permanent dentition. (Dorland, 27th ed)Abnormalities, MultipleNervous System Malformations: Structural abnormalities of the central or peripheral nervous system resulting primarily from defects of embryogenesis.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Internal Capsule: WHITE MATTER pathway, flanked by nuclear masses, consisting of both afferent and efferent fibers projecting between the WHITE MATTER and the BRAINSTEM. It consists of three distinct parts: an anterior limb, posterior limb, and genu.Diffuse Axonal Injury: A relatively common sequela of blunt head injury, characterized by a global disruption of axons throughout the brain. Associated clinical features may include NEUROBEHAVIORAL MANIFESTATIONS; PERSISTENT VEGETATIVE STATE; DEMENTIA; and other disorders.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.Septum Pellucidum: A triangular double membrane separating the anterior horns of the LATERAL VENTRICLES of the brain. It is situated in the median plane and bounded by the CORPUS CALLOSUM and the body and columns of the FORNIX (BRAIN).Fornix, Brain: Heavily myelinated fiber bundle of the TELENCEPHALON projecting from the hippocampal formation to the HYPOTHALAMUS. Some authorities consider the fornix part of the LIMBIC SYSTEM. The fimbria starts as a flattened band of axons arising from the subiculum and HIPPOCAMPUS, which then thickens to form the fornix.PAX9 Transcription Factor: A paired box transcription factor that is involved in ODONTOGENESIS.Demyelinating Diseases: Diseases characterized by loss or dysfunction of myelin in the central or peripheral nervous system.Brain Diseases: Pathologic conditions affecting the BRAIN, which is composed of the intracranial components of the CENTRAL NERVOUS SYSTEM. This includes (but is not limited to) the CEREBRAL CORTEX; intracranial white matter; BASAL GANGLIA; THALAMUS; HYPOTHALAMUS; BRAIN STEM; and CEREBELLUM.Neural Pathways: Neural tracts connecting one part of the nervous system with another.Myelin Sheath: The lipid-rich sheath surrounding AXONS in both the CENTRAL NERVOUS SYSTEMS and PERIPHERAL NERVOUS SYSTEM. The myelin sheath is an electrical insulator and allows faster and more energetically efficient conduction of impulses. The sheath is formed by the cell membranes of glial cells (SCHWANN CELLS in the peripheral and OLIGODENDROGLIA in the central nervous system). Deterioration of the sheath in DEMYELINATING DISEASES is a serious clinical problem.Aicardi Syndrome: A rare genetic disorder characterized by partial or complete absence of the CORPUS CALLOSUM, resulting in infantile spasms, MENTAL RETARDATION, and lesions of the RETINA or OPTIC NERVE.Tooth Abnormalities: Congenital absence of or defects in structures of the teeth.Hydrocephalus: Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, INTRACRANIAL HYPERTENSION; HEADACHE; lethargy; URINARY INCONTINENCE; and ATAXIA.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Oligodendroglia: A class of large neuroglial (macroglial) cells in the central nervous system. Oligodendroglia may be called interfascicular, perivascular, or perineuronal (not the same as SATELLITE CELLS, PERINEURONAL of GANGLIA) according to their location. They form the insulating MYELIN SHEATH of axons in the central nervous system.Malformations of Cortical Development: Abnormalities in the development of the CEREBRAL CORTEX. These include malformations arising from abnormal neuronal and glial CELL PROLIFERATION or APOPTOSIS (Group I); abnormal neuronal migration (Group II); and abnormal establishment of cortical organization (Group III). Many INBORN METABOLIC BRAIN DISORDERS affecting CNS formation are often associated with cortical malformations. They are common causes of EPILEPSY and developmental delay.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Syndrome: A characteristic symptom complex.Atrophy: Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes.Congenital Abnormalities: Malformations of organs or body parts during development in utero.Intellectual Disability: Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual has an intellectual disability. IQ scores between 70 and 79 are in the borderline range. Scores below 67 are in the disabled range. (from Joynt, Clinical Neurology, 1992, Ch55, p28)Leukoencephalopathies: Any of various diseases affecting the white matter of the central nervous system.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Cerebral Ventricles: Four CSF-filled (see CEREBROSPINAL FLUID) cavities within the cerebral hemispheres (LATERAL VENTRICLES), in the midline (THIRD VENTRICLE) and within the PONS and MEDULLA OBLONGATA (FOURTH VENTRICLE).Hypertelorism: Abnormal increase in the interorbital distance due to overdevelopment of the lesser wings of the sphenoid.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Urogenital Abnormalities: Congenital structural abnormalities of the UROGENITAL SYSTEM in either the male or the female.Microcephaly: A congenital abnormality in which the CEREBRUM is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (Desk Reference for Neuroscience, 2nd ed.)Brain Injuries: Acute and chronic (see also BRAIN INJURIES, CHRONIC) injuries to the brain, including the cerebral hemispheres, CEREBELLUM, and BRAIN STEM. Clinical manifestations depend on the nature of injury. Diffuse trauma to the brain is frequently associated with DIFFUSE AXONAL INJURY or COMA, POST-TRAUMATIC. Localized injuries may be associated with NEUROBEHAVIORAL MANIFESTATIONS; HEMIPARESIS, or other focal neurologic deficits.Dominance, Cerebral: Dominance of one cerebral hemisphere over the other in cerebral functions.Corpora Allata: Paired or fused ganglion-like bodies in the head of insects. The bodies secrete hormones important in the regulation of metamorphosis and the development of some adult tissues.Dandy-Walker Syndrome: A congenital abnormality of the central nervous system marked by failure of the midline structures of the cerebellum to develop, dilation of the fourth ventricle, and upward displacement of the transverse sinuses, tentorium, and torcula. Clinical features include occipital bossing, progressive head enlargement, bulging of anterior fontanelle, papilledema, ataxia, gait disturbances, nystagmus, and intellectual compromise. (From Menkes, Textbook of Child Neurology, 5th ed, pp294-5)Marchiafava-Bignami Disease: A neurodegenerative condition that is characterized by demyelination or necrosis of the CORPUS CALLOSUM. Symptoms include DEPRESSION; PARANOIA; DEMENTIA; SEIZURES; and ATAXIA which can progress to COMA and death in a few months. Marchiafava-Bignami syndrome is seen often in alcoholics but has been found in non-alcoholics as well.Ultrasonography, Prenatal: The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.Prenatal Diagnosis: Determination of the nature of a pathological condition or disease in the postimplantation EMBRYO; FETUS; or pregnant female before birth.Meningomyelocele: Congenital, or rarely acquired, herniation of meningeal and spinal cord tissue through a bony defect in the vertebral column. The majority of these defects occur in the lumbosacral region. Clinical features include PARAPLEGIA, loss of sensation in the lower body, and incontinence. This condition may be associated with the ARNOLD-CHIARI MALFORMATION and HYDROCEPHALUS. (From Joynt, Clinical Neurology, 1992, Ch55, pp35-6)Lissencephaly: A "smooth brain" malformation of the CEREBRAL CORTEX resulting from abnormal location of developing neurons during corticogenesis. It is characterized by an absence of normal convoluted indentations on the surface of the brain (agyria), or fewer and shallower indentations (pachygryia). There is a reduced number of cortical layers, typically 4 instead of 6, resulting in a thickened cortex, and reduced cerebral white matter that is a reversal of the normal ratio of cerebral white matter to cortex.Organ Size: The measurement of an organ in volume, mass, or heaviness.Neuroimaging: Non-invasive methods of visualizing the CENTRAL NERVOUS SYSTEM, especially the brain, by various imaging modalities.Infant, Newborn: An infant during the first month after birth.Fetal Diseases: Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.Cerebrum: Derived from TELENCEPHALON, cerebrum is composed of a right and a left hemisphere. Each contains an outer cerebral cortex and a subcortical basal ganglia. The cerebrum includes all parts within the skull except the MEDULLA OBLONGATA, the PONS, and the CEREBELLUM. Cerebral functions include sensorimotor, emotional, and intellectual activities.Spastic Paraplegia, Hereditary: A group of inherited diseases that share similar phenotypes but are genetically diverse. Different genetic loci for autosomal recessive, autosomal dominant, and x-linked forms of hereditary spastic paraplegia have been identified. Clinically, patients present with slowly progressive distal limb weakness and lower extremity spasticity. Peripheral sensory neurons may be affected in the later stages of the disease. (J Neurol Neurosurg Psychiatry 1998 Jan;64(1):61-6; Curr Opin Neurol 1997 Aug;10(4):313-8)Craniofacial Abnormalities: Congenital structural deformities, malformations, or other abnormalities of the cranium and facial bones.Tooth Exfoliation: Physiologic loss of the primary dentition. (Zwemer, Boucher's Clinical Dental Terminology, 4th ed)MSX1 Transcription Factor: A homeodomain protein that interacts with TATA-BOX BINDING PROTEIN. It represses GENETIC TRANSCRIPTION of target GENES and plays a critical role in ODONTOGENESIS.Cebus: A genus of the family CEBIDAE, subfamily CEBINAE, consisting of four species which are divided into two groups, the tufted and untufted. C. apella has tufts of hair over the eyes and sides of the head. The remaining species are without tufts - C. capucinus, C. nigrivultatus, and C. albifrons. Cebus inhabits the forests of Central and South America.Lipoma: A benign tumor composed of fat cells (ADIPOCYTES). It can be surrounded by a thin layer of connective tissue (encapsulated), or diffuse without the capsule.Image Interpretation, Computer-Assisted: Methods developed to aid in the interpretation of ultrasound, radiographic images, etc., for diagnosis of disease.Gestational Age: The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.Neuronal Migration Disorders: Disorders resulting from defects in migration of neuronal cells during neurogenesis. Developing nerve cells either fail to migrate or they migrate to incorrect positions resulting in formation of heterotopias, lissencephaly, or other malformations and dysfunctions of the nervous system.Hyperglycinemia, Nonketotic: An autosomal recessive metabolic disorder caused by deficiencies in the mitochondrial GLYCINE cleavage system.Neuroglia: The non-neuronal cells of the nervous system. They not only provide physical support, but also respond to injury, regulate the ionic and chemical composition of the extracellular milieu, participate in the BLOOD-BRAIN BARRIER and BLOOD-RETINAL BARRIER, form the myelin insulation of nervous pathways, guide neuronal migration during development, and exchange metabolites with neurons. Neuroglia have high-affinity transmitter uptake systems, voltage-dependent and transmitter-gated ion channels, and can release transmitters, but their role in signaling (as in many other functions) is unclear.Neuropsychological Tests: Tests designed to assess neurological function associated with certain behaviors. They are used in diagnosing brain dysfunction or damage and central nervous system disorders or injury.Penis: The external reproductive organ of males. It is composed of a mass of erectile tissue enclosed in three cylindrical fibrous compartments. Two of the three compartments, the corpus cavernosa, are placed side-by-side along the upper part of the organ. The third compartment below, the corpus spongiosum, houses the urethra.Whale, Killer: The species Orcinus orca, in the family Delphinidae, characterized by its black and white coloration, and huge triangular dorsal fin. It is the largest member of the DOLPHINS and derives its name from the fact that it is a fearsome predator.Imaging, Three-Dimensional: The process of generating three-dimensional images by electronic, photographic, or other methods. For example, three-dimensional images can be generated by assembling multiple tomographic images with the aid of a computer, while photographic 3-D images (HOLOGRAPHY) can be made by exposing film to the interference pattern created when two laser light sources shine on an object.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Lateral Ventricles: Cavity in each of the CEREBRAL HEMISPHERES derived from the cavity of the embryonic NEURAL TUBE. They are separated from each other by the SEPTUM PELLUCIDUM, and each communicates with the THIRD VENTRICLE by the foramen of Monro, through which also the choroid plexuses (CHOROID PLEXUS) of the lateral ventricles become continuous with that of the third ventricle.Dichotic Listening Tests: Tests for central hearing disorders based on the competing message technique (binaural separation).Corpus Luteum Maintenance: Process of maintaining the functions of CORPORA LUTEA, specifically PROGESTERONE production which is regulated primarily by pituitary LUTEINIZING HORMONE in cycling females, and by PLACENTAL HORMONES in pregnant females. The ability to maintain luteal functions is important in PREGNANCY MAINTENANCE.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Echoencephalography: Use of reflected ultrasound in the diagnosis of intracranial pathologic processes.Sex Characteristics: Those characteristics that distinguish one SEX from the other. The primary sex characteristics are the OVARIES and TESTES and their related hormones. Secondary sex characteristics are those which are masculine or feminine but not directly related to reproduction.Surgically-Created Structures: Organs or parts of organs surgically formed from nearby tissue to function as substitutes for diseased or surgically removed tissue.Apraxias: A group of cognitive disorders characterized by the inability to perform previously learned skills that cannot be attributed to deficits of motor or sensory function. The two major subtypes of this condition are ideomotor (see APRAXIA, IDEOMOTOR) and ideational apraxia, which refers to loss of the ability to mentally formulate the processes involved with performing an action. For example, dressing apraxia may result from an inability to mentally formulate the act of placing clothes on the body. Apraxias are generally associated with lesions of the dominant PARIETAL LOBE and supramarginal gyrus. (From Adams et al., Principles of Neurology, 6th ed, pp56-7)Luteolysis: Degradation of CORPUS LUTEUM. In the absence of pregnancy and diminishing trophic hormones, the corpus luteum undergoes luteolysis which is characterized by the involution and cessation of its endocrine function.