Researchers have found that nearly twice as many of the neural connections made in an infant's brain will ever be used. the unused connections will be

Pruned

Explanation:

Whenever there are extra synapses present in the brain that are no longer in use then the brain tends to eliminate these connections and this is termed as synaptic pruning .During this process there is decay of the dendrites as well as the axons .The process typically occurs at the peak in the period between early childhood and the onset of puberty however it begins at the time of birth and continues upto the early 20s. Further pruning is affected by the learning mechanism and the influence of the environment.One thing to be noted is that in pruning the death of the neurons does not occur however there is simple retraction of the synaptic connections.

Mutations are changes in the dna