Week 5: Neurodevelopment and Neuroplasticity Flashcards
Development
A change in a property of neurobiology over time (ex: myelination, brain growth, etc)
Prenatal development stages
1: Induction of the neural plate
2: Neuronal Proliferation
3: Migration
4: Axonal growth
5: Cell death
Stage 1
Layers develop 18 days after conception (ecto-, meso-, and endoderm). Stem cells accumulate en mass in the neural plate on the ectoderm. Neuronal tube and basic brain structures form after 24 days
Stem cells
Can generate sub-types of cells. Are highly able to differentiate, but after they differentiate they can only produce that type of cell
Stage 2
Rapid neuron creation; more than we need. Made in the ventricular zone before migrating to final destination
Stage 3
Cells move either radially (out from the center) or tangentially (any other pathway). Deep layers form first, then cells move outwards. Follows aggregation
Aggregation
Migrating cells organize themselves in a particular way; mishaps in alignment could correspond to disorders
Stage 4
When cells reach their final point, their axons grow toward biologically predetermined destinations. The growth cone at the end of the axon is guided by attractive and repulsive chemicals.
Fascigulation
Pioneer axons will blaze a trail that other axons will follow when growing. Leads to the formation of tracts.
Sperry frog experiment
Examining if spatial proximity determined axon growth. Cut axons in a frogs eye, then rotated it to see if the axons would reconnect differently. Found that they will still grow toward their original target, even when rotated
Chemoaffinity theory of axon growth
Growth patterns are guided by one growth factor per growth pattern.
DISPROVEN: lesion studies found that axons are sensitive to more than one chemical
Topographic gradient hypothesis
Concentration of chemicals guides axon growth. Arguing topographic gradient of chemicals
Synaptogenesis
Formation of synapses. Facilitated by glial cells. Weaker connection will be pruned or die. Occurs very rarely past a certain developmental point
Neurotrophin hypothesis of synaptogenesis
There is a competition for neurotrophin signals; the more you get the more likely you survive
Stage 5
Cell death. Apoptosis is programmed and clean; neurosis is spontaneous and messy
Strongest cells are selected for due to limited brain resources
Synapse elimination
Facilitated by glial cells. With repeated activation, synapses can get weaker or stronger over time
Causes of change in synaptic density
The brain grows x4 in size over life (synaptogenesis, dendritic growth, myelination); brain areas mature at different rates
Critical period
A period of development where stimulus is required for development. End due to limitations on growth and/or myelination
Sensitive period
A period where stimulus is more powerful in affecting development. Has environmental and psychological factors that motivate or inhibit learning
Adult neurogenesis
Very rare; only occurs in the hippocampus and the olfactory bulb. New cells take 4-6 weeks to develop and are more plastic and more excitable
Benefits of Hippocampal neurogenesis
Has been found to improve memory and reduce anxiety. Consistent with the link btw the hippocampus and mood
Traits of Neurodevelopmental disorders
High heritability; emerge early in life; high comorbidity rate
Schizophrenia
Symptoms: positive and negative (adding sensation or loss of sensation)
Causes: dopamine transmission defects; excessive pruning of cortical areas; abnormal cell organization
Physiological: reduced grey matter in hippocampus and orbitofrontal cortex
Heterogenous disorder
DA Hypothesis of Schizophrenia
Too much dopamine in specific pathways (high in mesolimbic, low in mesocortical) correlates with positive symptoms
Autism Spectrum Disorder (ASD)
Symptoms: poor social interaction, repetitive behaviors, slow language development
Causes: Unknown. Diagnoses are increasing due to awareness and advancements in technology
Physiological: high number of synapses/too much gray matter
Heterogenous disorder
Attention Deficit Hyperactivity Disorder (ADHD)
Symptoms: inattentive and hyperactivity (can be solo or combined)
Causes: maturational delay in the prefrontal cortex; affects 6-10% of the population; lower dopamine levels
Physiological: reduced cortical volume in the prefrontal cortex
Treatment: icrease dopamine and noradrenergic transmission
Psychopathy and Anti-social Personality Disorders (ASPD)
Traits: guiltless, manipulative, aware of actions and not changing or caring; typically charismatic and popular
Genetic and environmental risks; difficult to study due to ethics
Physiological: reduced function in frontal cortex and amygdala
Low arousal theory of ASPD
Reduced response to threats which decreases impulse control and causes a continual need for stimulation
