Brain Development and Plasticity Flashcards
Maturation of the Vertebrate Brain - Age of Formation
2 week old embryo
Maturation of the Vertebrate Brain - Process
Thickening of the dorsal surface
Formation of lips to create the neural tube surrounding a fluid filled cavity which will later form the ventricles
Forward end of the tube differentiates to form the hindbrain, midbran and forebrain
Stages of Neuron Development
Proliferation, Migration, Differentiation, Myelination, Synaptogenesis
Stages of Neuron Development - Proliferation
Production of new cells by the division of stem cells into neurons and glia
Stages of Neuron Development - Migration
Movements of cells to their target distination
May be radially or tangentically, guided by radial glia, immunoglobins and chemokines
Stages of Neuron Development - Differentiation
Cells differentiate to form neurons or glia
Neurons from axons and dendrites
Axon path-finding occurs
Stages of Neuron Development - Myelination
Glia (Oligodendrocytes / Schwann cells) produce myelin to speed up transmission of impulses along the axon
Continues throughout life
Stages of Neuron Development - Synaptogenesis
Formation of new synapes
Continues throughout life during learning and memory trace formation
Maturation - Grey Matter Volume
Decreases with age
First year of life +185%
Adulthood +20-30%
Fine-tuning
Brain has limited capacity to recognise itself
Gaining or losing synapses indicates change in connections and information processing
Axon-pathfinding
Process by which neurons send out axons to reach the correct targets
Axon-pathfinding - Weiss 1924
Found eveidence that axons find their own way to their target destinations
Axon-pathfinding - Sperry 1943
Removed, rotated and replaced the eyes of frogs
Severed axons found their way back to their origins and targets, not the location of where they are expected to be
Suggests the involvement of monitoring marker to track where their target is
Axon-pathfinding - Chemical
Axons regenerate in their original position by following cell-surface molecules
Trial synapses are formed and tested - if stimulated they are strenghtend, if no stimulated they are eliminated
Axon-pathfinding - Neural Competition
Growth and survival of neurons is dependent on nerve growth factor
Competition over nerve growth factor occurs - neurons which receive this are kept, those that do not are eliminated
Axon-pathfinding - Nerve Growth Factor
Neurotrophin released by muscles
Enables neural competition which improves efficiency of neurons by allowing the number of incoming axons to match the number of receiving cells
Vulnerable Brains - When
During embryonic development
Vulnerable Brains - Causes and Effects
Fever impairs proliferation
Low glucose consumption impairs development
Fetal alcohol syndrome impairs development
Vulnerable Brains - Causes and Effects, Fetal alcohol syndrome
Dendrites are short with fewer branches resulting in impairments in learning, memory, language and attention
Alcohol suppresses glutamate and enhances GABA so neurons are excited and stimulated less, receiving less Nerve Growth Factor resulting in synapse elimination and neuron apoptosis
Effects of Experience - Enriched Environments
Those in enriched environments have thicker cerebral cortex, increased dendritic branches and improved learning due to the strengthening of more synapses and creation of more traces
Effects of Experience - Reorganisation
Practice reorganises the brain the maximise performance
Effects of Experience - Reorganisation and Plasticity, Sadato et al 1998
The brains of individuals that have been blind since infancy show reorganisation
Visual cortex is active during tactile discrimination tasks, indicating brain plasticity
Language Learning - Chomsky
A critical period after which it becomes much harder to acquire language exists
Language Learning - Mechelli et al 2004
Bilingualism results in changes of grey matter, especially in languge-related areas indicating how learning and pratice alters brain organisation
Lateralisation of Function - Right body
Controlled by left side of the brain
Lateralisation of Function - Left body
Controlled by right side of the brain
Lateralisation of Function - Right brain
Controls left side of the body
Involved in facial recognition, emotion, music, tactuality, non-verbal memory and spatial processing
Lateralisation of Function - Left brain
Controls right side of the body
Involed in visual and auditory language, speech and verbal memory
Lateralisation of Function - Language
Evidence from Broca and Wernicke area damage suggest double dissociation of language abilities and localisation of brain function
Lateralisation of Function - Language, Broca’s Area
Located in the frontal lobe
Controls langauge production
Aphasia results in inability to produce fluent language
Lateralisation of Function - Language, Wernicke’s Area
Located in temporal lobe
Controls language comprehension
Aphasia results in incomprehensible yet fluent language producution
Plasticity
Ability for the brain to reorganise and structure functions to compromise for damaged areas or loss of function
Plasticity - Causes
Tumour, infection, exposure to toxins, degenerative disease, closed head injury, stroke
Plasticity - Diaschasis
Decreased activity of surviving neurons after damage to other brain regions
Disrupts usual stimulation patterns
Plasticity - Mechanisms
Regrowth and Remyelination
Collateral sprouting
Reorganisation of Sensory Representations
Change in Neuron Sensitivity
Plasticity - Mechanisms, Reorganisation of Sensory Representations
e.g. Sodato et al 2008
Limb amputations result in changes in somatosensory cortex mapping to accommodate for the area no longer assigned to the limb
Plasticity - Mechanisms, Change in Neuron Sensitivity
Denervation or Disuse changes
Plasticity - Mechanisms, Change in Neuron Sensitivity, Denervation
Heightened sensitivity after destruction of an incoming axon in order to attempt to receive suffient stimulation
Plasticity - Mechanisms, Change in Neuron Sensitivity, Disuse
Heightened sensitivity due to inactivy to make use of any slight activity / stimulation
