Neuroplasticity: neural networks & neural pruning

Neuron

A type of cell that receives, processes, and transmits information through electrical and chemical signals.

Neural network

A series of connected neurons that allows the processing and transmitting of information. Specific networks are responsible for specific tasks.

Neural pruning

Neural pruning (aka Synaptic pruning) happens when we lose synaptic connections in a neural network because we do not use them

How do neurons work?

Neurons connect to each other and information is passed between them by neurotransmitters being fired across the synapse. The neurotransmitter binds to the receptors on the next neuron and this is how they send messages. The more we use our brains for particular tasks, the more dendrites our neurons grow and connect to other neurons. This is how neural networks are established.
If we have lots of neural networks connecting neurons in specific areas of the brain, those areas increase in size. Our environment can affect the development of neurons. With lots of stimulation we learn a lot and our neurons make lots of connections and our brains grow. If we're deprived of stimulation or neglected, we have fewer connections between neurons.

Cortical thickness

amount of grey matter in the outer layer of the brain

Grey matter

Grey matter serves to process information in the brain. The structures within the grey matter process signals from the sensory organs or from other areas of the grey matter. This tissue directs sensory stimuli to the neurons in the central nervous system where synapses induce a response to the stimuli.

Squeglia et al., (2013): aim

to see how synaptic pruning correlates with cognition and behaviour.

Squeglia et al., (2013): method

used brain scans to observe the grey matter in the brains of participants. Cortical thickness was measured using MRI. Data was gathered on a range of cognitive abilities, such as problem solving, working memory, and learning.

Squeglia et al., (2013): participants

185 kids aged 12-14 from San Diego. Excluded those who used drugs/alcohol/cigarettes, had psychological disorders/learning disabilities, or were not fluent in English.

Squeglia et al., (2013): results

negative correlation was found between age and cortical thickness; the older the kids were, the less grey matter they had. Boys showed more synpatic pruning than girls. The less grey matter and the more synaptic pruning that occurs, the better the kids were at tests of learning, memory and problem solving.

Squeglia et al., (2013): conclusion

neural pruning occuring between the ages of 12-14 has an effect on kids abilities to complete cognitive tasks. results suggest that synaptic pruning improves cognitive function through the elimination of unnecessary synaptic connections.

Passamonti et al., (2012): aim

to investigate what effect reduced serotonin has on the prefrontal cortex (PFC) when exposed to threat.

Passamonti et al., (2012): method

Participants consumed a placebo drink or one lacking tryptophan (a key amino acid in the building
of serotonin in the brain) which reduced serotonin levels. They were placed in an fMRI machine and
were shown a variety of different faces (e.g. angry, happy, sad).

Passamonti et al., (2012): results

Participants who drank the serotonin depleting drink had reduced function in their PFC when they were perceiving images of angry faces while in the fMRI. The results also showed that reduced serotonin disrupted the neural network communication between the amygdala and the PFC when viewing angry faces.

Passamonti et al., (2012): conclusion

The reduced function in the PFC when exposed to angry faces (a threat) could explain serotonin's link with aggression; people can't inhibit their impulsive reaction to the threat because serotonin is affecting the part of the brain that helps us to stop acting impulsively. This study shows how serotonin is important in neural networks between the amygdala and PFC.