TB10 - Evolution and Development of the Brain Flashcards
What are phylogeny and ontogeny?
Phylogeny refers to how cognitive abilities have developed over the millennia whilst ontogeny refers to how cognitive abilities develop within an individual.
What are research approaches to studying the evolution of the brain?
Comparative studies with other animals, understanding changes in human infants and examining archaeological records.
What did Charles Darwin suggest?
An organisms morphological features represent traits shared with other animals because of a common ancestor.
Adaptation meant that different traits became more specialised to environments.
What did Piaget suggest?
Children construct an understanding of the world through assimilation and accommodation.
Assimilation - Children add experiences to pre-existing schemes of thought.
Accommodation - Children react to exerpiences by changing/modifying their schemes of thought.
What did Ernest Haeckel suggest?
Ontogeny reflects phylogeny - the development an organism passes through during their life is parallel to the same changes over the course of evolution.
This is the idea that more basic features appear before advanced ones.
How does early brain development progress?
The nervous system begins to develop at day 20.
Neural tube emerges and creates the brain and the spinal cord, which is made up of stem cells called neural precursor cells.
The anterior end of the tube develops features like the forebrain.
Cell division occurs in the inner surface of the tube.
Neural precursor cells migrate outwards where they differentiate into neurons.
What is neural differentiation?
Neural precursor cells change into needed neurons and glial cells via transcription factors turning on and off certain genes.
Which features distinguish neuronal types?
Signalling properties
Transmitter agents
Receptor molecules
What is myelination?
This is the forming of the myelin sheath around a nerve, which carries the active potentials across the nerve bodies.
It occurs at roughly 29 weeks of gestation but does not complete until adolescence.
It is thought to play an important role in the emergence of cognitive functions.
What are oligodendrocytes?
These are a type of glial cell that elaborate myelin that unsheathes many types of neuronal axons and dendrites. This increases action potential speed.
What is synaptogenesis?
This is when billions synapses are formed. Axons branch out to create them and allow information to be transmitted to other cells.
It occurs first in regions important in early development.
What is synaptic pruning?
This occurs to rearrange and adjust the number of synapses in the brain, removing ones that are no longer important to us to allow room for learning.
What did Bourgeois and Rakic (1993) find with regards to synaptic development?
In rhesus monkeys it was found that the overall number of synapses increase progressively until adolescence and then start to reduce.
Which areas of the brain develop first?
Primary functions such as motor and sensory systems in the frontal lobe. Language and spatial attention in the temporal and parietal loves develop slightly later.
Prefrontal and lateral temporal regions develop last for modulation of attention and decision making.
What is the growth pattern of white and gray matter in the brain?
White matter develops steadily into adulthood, whilst gray matter shows a U shape and starts declining in early adulthood, reflecting the elimination of neural connections.
What is most important with brain size and intelligence?
Residual brain size - how much brain you actually have vs how much you should have based on your body mass.
How is residual brain size and the neocortex linked?
As residual brain size increases, so does the size of the neocortex, which allows the species to advance in cognitive abilities.
What did Shaw’s (2006) longitudinal brain size study find?>
That the rate of change in cortical gray matter thickness was more predictive of IQ that the absolute difference in cortical thickness
What did Gilbert, Dobyns and Lahn (2005) find with regards to genes and brain size?
The microcephalin-1 (MCHPH1) gene is what underlies the neuronal growth and differentiation.
Changes in the gene could explain brain sizes across primates and thus different cognitive functions.
For example, adult humans with microcephaly have roughly the same size brain as a chimpanzee and suffer severe disabilities.
What is the late equals large model?
The suggestion that later neurogenesis leads to a larger brain
Some argue the model is too simplistic and that parts of the brain just evolve independently.
What did Finlay and Darlington (1995) find with regards to neurogenesis?
Changes in the timing of neurogenesis might account for regional diversity in the brain.
What order are neurons in the brain developed?
Locus coeruleus - Brain stem neurons are born first
Septum - Limbic neurons are developed next
Neocortical neurons - Developed last
What is the concerted brain hypothesis?
Regions of the brain are interconnected. Any evolutionary change cannot advance without involving all parts of the brain.
What is the mosaic brain hypothesis?
Adaptations in the brain act on specific regions, so adaptive responses do not involve other parts of the brain.
What has been found with regards to the hippocampus and food storing behaviour in animals?
The hippocampal volume of Clark’s nutcracker, a food-storing type of covid bird, is larger than expected compared to the Scrub-jay’s, another type of covid bird that is a generalist feeder. This suggests that hippocampal volume is related to food-storing behaviour and would support the idea of specialisation within regions of the brain.
What is the foraging hypothesis?
That the evolution of learning and memory is due to the demands of feeding on dispersed food sources.
What evidence is there from primates for the foraging hypothesis?
Primates with fruit based diets tend to have a larger residual brain size compared to those that eat insects and leaves, suggesting an adaptation for spatial distribution of ripe fruits.
What evidence is there from bats for the foraging hypothesis?
Bats that eat fruit, flowers or blood have larger residual brains compared to bats that eat insects.
What research was done on London Taxi Drivers?
Maguire (2000) found that posterior hippocampal regions showed more gray matter volume, so concluded that this area was important for spatial representation.
Maguire, Woollett and Spiers (2006) tested for variables such as driving experience and stress so compared taxi drivers with bus drivers in London and found that only the taxi drivers had increased GMV so it is the spatial knowledge (routes of London) and not the stress or experience of driving within London that causes it.
