Brain size increases as existing
neurons grow and the connections between them proliferate in number.
Structure of the brain
1. Central core
2. limbic system
3. cerebral hemispheres (known together as cerebrum)
- Outer layer: cerebral cortex
· Inside of cerebrum beneath the cortex
Ø Composed mostly of myelinated axons and appears
- Structure of the cerebrum
- contains following attributes:
Ø sensory perception
Ø motor abilities
· Brain Hemispheres
Hemispheres divided by the corpus callosum
- Band of nerve fibers that connects the two hemispheres
Differences between the hemispheres
- Hemispheres are anatomically different and control different functions
- Each side of the brain tends to specialize in certain perceptual and cognitive tasks.
- E.g.: studies of people who have suffered brain damage to one part of brain give us important information about
the function in which each hemisphere normally specializes
Exceptions to specialization
- Great deal of cross-wiring between hemispheres
- Hemispheres may differ in their specialization but they integrate their activities all the time.
- When one half suffers damage the other half may take over
Neurons and synapses
Function of neurons
Neurons send and receive messages
(neural impulses) throughout brain and nervous system.
- Guided my neurochemical process neurons move to a variety of places in the brain
- Ensures that all parts of the brain are served by a sufficient number of neurons
Importance of synapses
Crucial to survival and learning
Help brain to receive input from
the environment before and after birth
- Neuronal death
- Synaptic pruning
Ø Timing of synaptic pruning
Ø As baby moves from reflexive behaviour to voluntary control over movements the motor area
of the brain develops most rapidly
Ø Number of synapses per neuron multiplied 6 times in first two years of life.
Ø First 4 to 12 months number of connections rises to 150% those of adult brain
Ø Proliferation enhances baby’s visual capacity – skilled at focusing on objects
at different distances
Ø Doesn’t peak until first year
- Responsiveness of the brain’s neural structures and functions to input from the environment.
- Brain size and function can be modified by experience
Plasticity and ageing
The finding backs up theories which suggest that the "plasticity"
or flexibility of the cells in the adult brain is far less than in the brain of a child.
certain areas of the brain at least, this "plasticity" appeared
to persist even into adulthood.
Ageing of the brain leads to impairments in:
- working memory,
- learning and memory retrieval, and
- visuospatial function,
- Cerebral atrophy
- Cerebellar Degeneration
- Traumatic brain injury
- Closed Head Injury