Neurodevelopment Flashcards
General structure
Basic structure of brain (forebrain, midbrain, hindbrain) correspond to structure of neural tube. Developmental neurogensis occurs in ventricular zone (a region lining the cerebral ventricles), providing neurons early in development and glial cells throughout life. Cells produced in tube then migrate to the appropriate region. Glial cells help cells move along to particular locations. Once they get to their spot, they differentiate into the types of cells they’re supposed to become. Molecules from contiguous cells cause the cells to differentiate. Essential component of brain development is cell death (apoptosis). Add more than 250,000 neurons per minute during height of prenatal growth.
Neurotrophic factors
Synaptogenesis: establishment of synaptic connections as axons and dendrites grow. Neurotrophic factors: target-derived chemicals that facilitate cell migration and synaptogenesis (they tell the synapses to come over here because it’s important to make this connection). More neurotrophic factors released means stronger connection. Less means weaker or even cell death. Ex: brain-derived neurotrophic factor (BDNF). Growth cones are attracted toward neurotrophic factors and pull the neurons toward the cells.
Adult neurogenesis
In both animals and humans. Grows in hippocampus and olfactory tubical. Neurogenesis in the dentate gyrus of the hippocampus plays an important role in declarative memory, spatial memory, and conditioning. Learning and stimulating environments enhance neurogenesis in the dentate gyrus of the hippocampus. Exercise also enhances hippocampal neurogenesis (long to moderate aerobic exercise drive neurogenesis the best) - corresponds to BDNF. Stress reduces neurogenesis. Reduced neurogenesis in the hippocampus implicated in depression. May be through stress. Anti-depressants might help with neurogenesis.
Three ingredients of brain development
1) Cell death (apoptosis). 2) Synapse rearrangement, synaptic modeling, synpatic pruning. The loss of some synapses and the development of others. Neurotrophic factors play important role in synaptogenesis. Microglial cells are central to synaptic pruning - recall that microglial cells are glial cells that function as the immune system of the CNS. 3) Myelination. Oligodendrocytes CNS and Schwann Cells PNS.
The adolescent brain
Tension between impulsiveness (limbic system) and reasonableness (PFC). A high-risk period for psychiatric illness - high spike because PFC is starting to develop more (more self-awareness).
The negative emotional brain during teenage years
Teenage years characterized by elevated negative emotion and hypersensitivity to social evaluation/rejection. Characterized by elevated activation in amygdala and medial prefrontal cortex (self-referential thought).
The positive emotional brain during teenage years
Teenage years characterized by elevated positive emotion and a hypersensitivity to reward-related stimuli. Hyperactivity in ventral striatum, associated with greater delay discounting and impulsivity. Mesolimbocortical pathway and impulsivity: elevated dopamine released in striatum important for understanding trait impulsivity. Human PET study assessing dopamine receptor availability and dopamine neurotransmission during amphetamine use. Elevated dopamine release in striatum important for understanding trait impulsivity. Dopamine centrally involved in psychopathology (depression, bipolar, schizophrenia) and the chemical most implicated in addiction.
The prefrontal executive control system in the teenage years
Last region of the brain to go through maturation. Current research says undergoing maturation up until age 28. Teenage years characterized by still developing prefrontal executive control system. Main ingredient driving development is myelination. Synapse rearrangement and pruning is also important. Gray matter density decreases.
Teenage brain asynchrony
Adolescence characterized by asynchrony between elevated negative and positive emotions and an immature prefrontal executive control system. Adolescence: a lot of acceleration combined with weak brake system. Children have an immature PFC and normal striatum. Adolescence - higher striatal responsivity and less brake of PFC. Adult - maturation of PFC, inhibiting accelerator.
What is adulthood in the brain?
Becoming an adult involves the maturation of pathways between the prefrontal cortex and emotion generation regions such as the amygdala and striatum (white matter tracts between PFC and amygdala). The maturation of these pathways allows one to use their rational mind to regulate their emotional mind. Negative relationships between amygdala and PFC (attenuating amygdala), as people age, amygdala to PFC functional connectivity is negative, can attenuate amygdala. Young ages - positive correlation (ramping it up).
Not becoming an adult too soon
Healthy controls display a positive amygdala-PFC relationship during childhood that becomes negative as they age (age appropriate regulation of amygdala). Institutionalized children display a negative amygdala-PFC relationship during childhood (age inappropriate regulation of amygdala). Romanian orphanages - no input, left to own devices, negative implications for being emotive. Institutionalized kids use cortex to suppress subcortex, accelerated rate of development. But they have elevated emotional reactivity. People with anxiety and depression also went through normative course much faster.
