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Questions and Answers
Development refers to a ______ change in a specific property over time.
Development refers to a ______ change in a specific property over time.
gradual
A developmental trajectory refers to the normal rate of change in a ______.
A developmental trajectory refers to the normal rate of change in a ______.
group
Abnormal trajectories are often associated with ______ impairments.
Abnormal trajectories are often associated with ______ impairments.
neurodevelopmental
Synaptic pruning occurs during ______ development.
Synaptic pruning occurs during ______ development.
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Neurogenesis is a key process in the ______ of the brain.
Neurogenesis is a key process in the ______ of the brain.
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Cell A releases Chemical ______
Cell A releases Chemical ______
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Axon B is exposed to more Chemical ______
Axon B is exposed to more Chemical ______
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Synaptogenesis is the making of new ______
Synaptogenesis is the making of new ______
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Many synapses created are later removed in a massive ______ phase
Many synapses created are later removed in a massive ______ phase
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The inputs of a mature neuron are fewer but more ______
The inputs of a mature neuron are fewer but more ______
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Cells that do not form synapses will often ______
Cells that do not form synapses will often ______
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The role of ______ cells, such as astrocytes, is important in synapse formation
The role of ______ cells, such as astrocytes, is important in synapse formation
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An axon may 'lose' at some synapses but 'win' at ______ others
An axon may 'lose' at some synapses but 'win' at ______ others
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Neurotrophins are transmitted via ______ signaling.
Neurotrophins are transmitted via ______ signaling.
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Apoptosis is a form of 'programmed cell ______'.
Apoptosis is a form of 'programmed cell ______'.
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In necrosis, cells 'break apart' and spill their ______.
In necrosis, cells 'break apart' and spill their ______.
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Microglia play an important role in mitigating ______.
Microglia play an important role in mitigating ______.
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You generate more ______ than needed during development.
You generate more ______ than needed during development.
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Many neurons are lost during early ______.
Many neurons are lost during early ______.
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In most of the CNS, new neurons are not generated in ______.
In most of the CNS, new neurons are not generated in ______.
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The process of axonal ______ + synapse formation is crucial for proper neural function.
The process of axonal ______ + synapse formation is crucial for proper neural function.
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The ______ development of the PFC was proposed relative to affective/reward systems.
The ______ development of the PFC was proposed relative to affective/reward systems.
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Glial cells play an important role in synapse ______, elimination, and maintenance.
Glial cells play an important role in synapse ______, elimination, and maintenance.
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Development continues past this ______; individual differences in rate exist.
Development continues past this ______; individual differences in rate exist.
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The ______ period is a time interval where an experience must occur for proper development.
The ______ period is a time interval where an experience must occur for proper development.
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The ______ period has a relatively greater effect on development.
The ______ period has a relatively greater effect on development.
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Synaptic properties are ______ with experiences such as learning.
Synaptic properties are ______ with experiences such as learning.
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We can identify potential developmental periods through deprivation and ______ studies in animals.
We can identify potential developmental periods through deprivation and ______ studies in animals.
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In animals, sensory ______ when young can disrupt normal development.
In animals, sensory ______ when young can disrupt normal development.
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Blindfolding in special environments profoundly impedes brain and behavior in ______.
Blindfolding in special environments profoundly impedes brain and behavior in ______.
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Early interventions are more helpful in ______.
Early interventions are more helpful in ______.
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Language acquisition is easiest at ______ years of age.
Language acquisition is easiest at ______ years of age.
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After around ______ years, language acquisition becomes much harder.
After around ______ years, language acquisition becomes much harder.
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Myelination creates a physical barrier to growth and sprouting of other ______.
Myelination creates a physical barrier to growth and sprouting of other ______.
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Nogo is a factor that inhibits ______ growth.
Nogo is a factor that inhibits ______ growth.
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The existence of sensitive periods is not entirely a biological ______.
The existence of sensitive periods is not entirely a biological ______.
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Language acquisition may involve different ______ in different ages.
Language acquisition may involve different ______ in different ages.
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Enhanced hippocampal neurogenesis is correlated with improved ______ and reduced anxiety.
Enhanced hippocampal neurogenesis is correlated with improved ______ and reduced anxiety.
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NDDs often emerge early in life, such as ______, ADHD, and intellectual disabilities.
NDDs often emerge early in life, such as ______, ADHD, and intellectual disabilities.
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High heritability indicates a strong role of ______ factors in NDDs.
High heritability indicates a strong role of ______ factors in NDDs.
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NDDs are distinct from ______ disorders, which emerge in adulthood.
NDDs are distinct from ______ disorders, which emerge in adulthood.
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Schizophrenia affects approximately ______ % of the population.
Schizophrenia affects approximately ______ % of the population.
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Cortical atrophy often seen in schizophrenia particularly affects the ______ cortex.
Cortical atrophy often seen in schizophrenia particularly affects the ______ cortex.
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Hypofrontality refers to ______ frontal activity in individuals with schizophrenia.
Hypofrontality refers to ______ frontal activity in individuals with schizophrenia.
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Major risk factors for schizophrenia include both ______ and environmental influences.
Major risk factors for schizophrenia include both ______ and environmental influences.
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Study Notes
Lecture 5: Neurodevelopment
- Neurodevelopment refers to changes in specific brain properties over time.
- A developmental trajectory describes the typical rate of change in a group.
- Abnormal trajectories are frequently linked to impairments.
- Prenatal neurodevelopment has five stages.
- The first stage is the induction of the neural plate in the embryo.
- The second stage is the process of developmental neurogenesis.
- The third stage involves neuronal migration and aggregation.
- The fourth stage includes axon growth and synapse formation.
- The fifth stage is neuronal death and synapse elimination.
- Fertilization begins when a sperm fertilizes an egg, creating a zygote.
- A blastocyst implants around 7-10 days post conception.
- At 18 days after conception, the embryo has three layers: ectoderm, mesoderm, and endoderm.
- Stem cells in the neural plate have self-renewal and pluripotency characteristics.
- These stem cells differentiate, lose their pluripotency and become unipotent.
- The neural plate folds to eventually form a neural tube.
- The tube's center becomes the ventricular system and spinal canal.
- The anterior portions form the midbrain, hindbrain, and forebrain, in that order.
Developmental Neurogenesis
- Progenitor cells multiply, increasing the neural tube's thickness
- Neurogenesis happens in several zones, including the ventricular zone (VZ).
- Most neurogenesis concludes before birth.
- Some cells retain the ability for neurogenesis after birth.
Neural Migration
- Neurons migrate to their target locations.
- Migration occurs in an inside-out pattern.
- Types of migration include tangential and radial migration.
- The ventricular zone produces excitatory neurons (80% of cells).
- Ganglionic eminences make inhibitory neurons (~20% of cells).
Aggregation
- Neurons in the same area physically align with one another.
- Cell adhesion molecules (CAMs) are crucial.
- Gap junctions, especially in glial cells, are prevalent initially.
Axonal Growth
- Axons grow towards their target cells.
- The axon's growth process involves a growth cone.
- Growth cones use filopodia for exploring their environment
- Filopodia search for appropriate chemical cues.
- Chemoattractive and chemorepulsive cues guide the growth cone.
Growth Cone Mechanisms
- Motor proteins aid in moving materials within the growth cone.
- Vesicle fusion adds membrane to the leading edge of the filopodium
- Actin polymerization pushes the filopodium toward its target
Axon Guidance
- Axonal growth is guided by chemoaffinity hypotheses.
- Target cells release specific chemicals that attract corresponding axons.
- Axons are responsive to different chemical concentrations depending on position.
- Other mechanisms involve topographical projection and chemical gradients.
Synapse Formation
- Synaptogenesis, or the formation of new synapses, follows axon growth.
- Glial cells, such as astrocytes, are crucial during synapse development.
- Initially, the synapse number is greater than necessary.
- Synaptic elimination, where weaker synapses are removed, occurs.
- The remaining stronger synapses determine neuronal connections.
Neuro-muscular Junction
- Axons can lose some synapses while strengthening others.
- Maturing neurons have fewer but more elaborated connections.
Synapse Failure
- Synapse failure leads to cell death via lack of chemical signaling.
- Neurotrophic factors are communicated through retrograde signaling (Cell B-> Cell A).
- Neurotrophins support neuron survival through intercellular communication.
- Competition between terminals for limited neurotrophins may occur.
- Apoptosis is a more organized form of cell death, where cell contents are packaged for removal.
- Necrosis is an uncontrolled cell death form that may cause inflammation and tissue issues.
- Micro-glial cells are important during synapse elimination for cleanup and tissue organization.
Cell Death and Adult Neurogenesis
- Cell death (e.g. through apoptosis) is a normal phenomenon during development.
- Many neurons are lost in early development.
- Most of the CNS doesn't regenerate many new neurons after birth.
- Some exceptions exist.
- Increased rates of neurogenesis are mainly related to early development rather than adult phases.
Developmental Periods
- Critical period: Time for an experience necessary for proper development of neural structures.
- Sensitive period: Time where experience has a greater impact on development, typically earlier, than later in life.
- Both periods indicate high levels of neural plasticity at certain phases.
Critical Period: Example
- Animals show sensory impairments when early development is affected by experience deprivation.
- Early interventions generally show better outcomes than later interventions, especially in children with learning or developmental issues.
Sensitive Periods for Language
- The crucial period for language learning occurs early in life (ages 3-7).
- Language acquisition becomes much harder after ~18 years of age.
- Factors like motivation and immersion vary sensitivity to the language during learning phases.
Why do these periods end
- Myelination physically limits new growth
- Myelination releases factors like Nogo to hinder axonal expansion
Sensitive Periods—Conclusion
- The existence of sensitive periods stems from both biological and non-biological factors.
3 – Adult Neurogenesis
- Neurogenesis, the generation of new neurons, is limited in the CNS.
- Neurons, once lost are permanent losses, typically not replaceable.
- Major production of new neurons happens primarily during development.
Neurodevelopmental Disorders (NDDs)
- NDDs are developmental disorders.
- Symptoms appear early, often affecting cognition and behavior.
- Genetic factors and environmental factors play important roles, as well as possible diagnostic considerations. acquired disorders emerge later in life, as a result of brain injuries or diseases.
- NDDs such as schizophrenia, autism spectrum disorder, and ADHD are commonly seen.
- Psychiatric disorders such as anxiety disorders, depression and others, are also possible comorbidities with NDDs.
Schizophrenia
- Schizophrenia (SZ) impacts about 1% of the population globally.
- Characteristics of schizophrenia include: negative symptoms, both positive and negative symptoms and cognitive symptoms.
- Neural features of SZ include cortical atrophy, abnormal cell organization, hypofrontality, and DA transmission alterations.
Major Risk Factors for Schizophrenia
- Environmental factors can increase SZ risk (e.g., prenatal/postnatal health, social, environmental circumstances, economic circumstances.)
- Genetic and early-life environmental risk factors have an elevated impact on SZ incidence.
- Substances like cannabis are associated with increased risk and earlier onset of schizophrenia among users
Dopamine (DA) Hypothesis of Schizophrenia
- Higher DA metabolite levels (HVA) and an increased number of D2 receptors are hypothesized to cause some SZ symptoms.
- Positive symptoms, like those seen with stimulant drug use, may be linked to increased DA levels.
- Drugs that block DA signaling (e.g., haloperidol) often reduce positive symptoms.
Dopamine Pathway Differences in Schizophrenia
- The mesolimbic pathway is associated with increased DA activity and positive symptoms.
- The mesocortical pathway is associated with decreased DA activity and negative/cognitive symptoms.
Antipsychotic Drugs
- Antipsychotic medications primarily work by blocking D2 receptors.
- Newer antipsychotics are designed to be less indiscriminately selective and have fewer undesirable side effects by targeting other neurotransmitter pathways.
Autism Spectrum Disorder (ASD)
- The spectrum of ASDs show varied symptoms in severity.
- Autism involves difficulties with social interaction, communication, and repetitive behaviors.
- A high proportion of cases involve above average IQ in some areas
- Diagnosed rates are rising due to improved diagnostic methods and increased public awareness.
- Children with ASD show synaptic density that are significantly greater than those without ASD, and these are maintained across development timelines.
Attention-deficit/hyperactivity disorder (ADHD).
- ADHD is a common neurodevelopmental disorder.
- Characterized by inattention, hyperactivity, and impulsivity.
- Symptoms vary in prominence, and often emerge in childhood at the same time as these other NDDs.
- Symptoms of ADHD can affect both children and adults, impacting social, emotional, and developmental health.
- Neurological features of ADHD include reduced total cerebral volume, and delayed cortical maturation, particularly in the prefrontal cortex (PFC). Low DA is also a possible factor.
- Medications like stimulants and non-stimulants address ADHD symptoms, by increasing noradrenergic or dopaminergic neurotransmitter transmission.
More on NDDs
- Co-morbidity, the co-existence of multiple NDDs, is common.
- Several factors affect NDDs, including the overlap in genetic factors between disorders, environmental factors as well as possible issues with diagnostic considerations.
- Psychopathy and anti-social personality disorder are discussed.
- Mechanisms for NDDs include differing genetic factors, developmental trauma and environmental influences.
- A low arousal theory that explains some aspects may be applicable to ASPD as well.
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Description
Test your knowledge on key concepts in developmental biology, including synaptic pruning, neurogenesis, and the role of different cell types in the brain. This quiz covers various terms and processes essential for understanding how the brain develops over time.
