Neurons A, B and C before damage **** **** **** ooo * * oooo oooo * * o o * A * -- Soma -- o o * * o o * * o B o * * o o **** **** o o ******** oooo oooo ***** oooooo **** oo ** -- Axons -- oo *** o ** o * ooooo ** oo oooo ** oo oo ** oo oo **** ***** oo * ************ oo ** oo ** oo Telodendrons ---- * o ** o * oo ** oo ** o ** o ** oo * o * @@@@@@ * o ** @@@@ @@@@* oo @@ @@ o @ @ ooo @ C @oooooo @ @ @@ @@ @@@@ @@@@ @@@@@@ @@@@ @@ @@ @ @ @ @ @@ @@ @@ @ @@ @@@@ @@ @@ @@ @@@ @@ @@ @ @@ @@ @@ @@ @ @@ @ Collateral sprouting after damage to neuron A **** ***** ***** *** *** ooo * ** oooo oooo ** A * o o ** * o o * ** o B o * ** o o ***** ****** o o ******** o o **** * oooo oooo ** * oooooo ** oo ** oo ** o * o ooooo oo oooo oo oo oo oo ooo ooo oooooo oo oo oooo oo oo oo oo o oo o New telodendrons -- oo oo oo oo oo o oo o oo oo oo o oo @@@@@@ o o oo @@@@ @@@@o oo @@ @@ o @ @ ooo @ C @oooooo @ @ @@ @@ @@@@ @@@@ @@@@@@ @@@@ @@ @@ @ @ @ @ @@ @@ @@ @ @@ @@@@ @@ @@ @@ @@@ @@ @@ @ @@ @@ @@ @@ @ @@ @Following damage to neuron A, neuron B generates new telodendrons from its axon to form a synapse at the receptor sites on neuron C formerly occupied by neuron A.
Types of collateral sprouting:
Heterotypic collateral sprouting (aka reactive synaptogenesis): This type of collateral sprouting occurs within day and does not lead to recovery of function.
Homotypic collateral sprouting: Begins to occur after about four weeks and leads to recovery of function.
Although collateral sprouting does occur in the Central Nervous System, the damaged is often too extensive for it to have much effect. It is believed that collateral sprouting may also be one of the mechanisms behind associative learning/classical conditioning.
Sources:
Klein, Stephen B. Biological Psychology. Prentice Hall, New Jersey: 2000.
http://www.medinfo.ufl.edu/other/profmed/slides/pm011399/slide19.html
http://www.nyu.edu/classes/azmitia/lectures/lecture13/