Neurobehavioural plasticity in development and ageing Flashcards
How does development occur?
More cells (neurones)
Bigger cells
More complex cells
More complex groupings - organisation into systems and structures will expand
Prerequisites or “building blocks”
- Biological substrate(s)
- Environmental context (external and internal)
- Capacity for plasticity of form and function
Putting the pieces together
- Stimuli and experience + brain systems = development
What is plasticity?
The adaptability of an organism to changes in its environment or differences between its various habitats
What can biological substrate(s) include?
Any aspect of the body Its anatomy (form/structure) Physiology (function/process) Genetic material and mechanisms
What do we focus on when we study the biological basis of behaviour/cognition?
Brain systems that provide the basis for all behaviour and cognition
Neurons, neurotransmitters, other cells and tissues
DNA/RNA, transcription, and regulation of neural processes
What are the external aspects of environmental context?
Aspects that impinge on our senses or our minds in a psychological way or our bodies in a physical way
What are the internal aspects of environmental context?
Aspects of physiology, such as the uterine environment on the foetus, or a person’s internal hormonal milieu (social environment) on brain and behaviour
What is stimuli and experience?
Sound, light, tactile signals: all the waveforms, particles, objects and chemicals that contact the sensory receptors
- Spontaneous neural activity
What is the central nervous system?
Spinal cord and brain
Function: integrates sensory information and responds accordingly
What is the peripheral nervous system?
Nerves connecting CNS and body
Function: allows for complex movements and behaviours (heat or cold stimuli)
What does the forebrain consist of?
Complex behavioural and cognitive functions
Cerebral hemispheres
Perception, coordinated action, integration of behaviour for purpose
What does the brainstem consist of?
Hindbrain and midbrain
Basic functions and behaviours
Sensing, moving, survival reflexes
What is glia/glial cells?
Constitute half of the brain volume
Physically and functionally support neural systems
What are neurons/nerve cells?
Cell body: contains DNA and life supporting organelles
Axon: transmits input signals to the terminal fibres and is where the output signal is conveyed
Dendrites: receive neurotransmitter input signals
100-200 billion in adult brain
Many shapes and sizes depending on function
5-100 microns (1 micron = 1/1000 mm)
What are the events as part of development?
Proliferation, Elimination, Organisation
What is proliferation?
Characteristics that emerge and qualitatively increase in complexity and/or quantitatively increase in size or number
What is elimination?
Characteristics that appear to decrease in size or number, or disappear altogether
What is organisation?
Synergy of proliferative and eliminative events Consists of: - Differentiation - Migration - Synaptic connection
When does development begin and end?
Events are ongoing across the lifespan:
- Prenatal
- Postnatal (infancy)
- Childhood
- Adolescence
- Adulthood
When change is more rapid at some points than others, what does it depend on?
The neurobiological system in question Individual differences (genetics, environment)
What occurs during the prenatal period?
Neural tube in the embryo (25 days) is the basis for all brain and spinal cord development
Neurons are cell bodies
When is axon and dendrite proliferation the greatest?
From 7 months prenatal to 2 years postnatal (axons lengthen, dendrites arborise)
What is the result of a genetically programmed development in conjunction with optimal environmental conditions?
Specialisation of cell anatomy and function
What size is the brain at birth?
30% of the adult weight
What is the state of the brain at birth?
Brain system development nearly complete, but higher order systems (e.g. cerebral cortex) take much longer to mature
What occurs in the first 3 years of life?
A period of extensive proliferation - the maximum number of neurons and synapses is reached
When is myelination (fatty layer accumulates around nerve cells) of axons most rapid?
4 months prenatal to 2 years postnatal
What is extensive proliferation accompanied by during the postnatal period?
Extensive elimination as synapses form:
- some preliminary dendrites lost
- many neurons are lost (programmed cell death)
- synapses that don’t receive stimulation also die (synaptic pruning)
What occurs in the childhood period?
Neuronal growth and synaptic connections continue, but at different rates in different brain systems
When is 90% of the adult brain size reached by?
6 years
When is the development of most aspects of brain anatomy and function completed?
Late adolescence
What is limited in adulthood?
In vertebrates, the brain’s ability to repair and regenerate after damage is limited
…But, neuroscience frontiers are being “pushed back”
What occurs in adulthood?
Synaptic connections continue to re-organise, largely in response to environmental conditions
Plasticity in a few areas is retained
What is lost in the ageing process?
Neuronal number and size
Decreased volume of cortical grey matter (the cortex of the brain, which contains nerve cell bodies)
Reduction in efficiency of cellular functions
Cumulative damage
The frontal lobe is late to develop and also very sensitive to change in adulthood, including ageing effects
When do the majority of neurons form?
Between 10-18 weeks
When can changes in the adult brain anatomy and function be detected from?
20 years onwards
Acceleration of neural ageing can occur any time in adulthood - lots of variability across individuals
What are the principles of environmental impact (continuum)?
Essential: nutrition, sensory input, social input
Negative: toxins, high stress, maternal malnutrition or illness
Positive: environmental enrichment, “optimal” stimulation
What occurs during the sensitive periods (programmed plasticity)?
Timing differs depending on brain-behaviour system and environmental factor in question
Windows of maximum impact at a particular developmental point or phase
What occurred in the experiments with rats that were either enriched or impoverished?
As adults, the EC group (compared to the IC) had greater arborisation of dendrites and more synapses per neuron
What occurred with the handled rats compared to the rats that were not handled?
They were less fearful in novel environments (behaviour, physiology)
Have different brain organisation (anatomy, neurotransmitter function, behaviour)
Show less marked decline in cognitive performance with advancing age
