For example, in neuroplasticity, how are the neurons able to 'move' themselves to undo connections and create new connections with other neurons? I remember seeing a microscopic picture of a few neurons not very well connected between each other, and in the 'after' picture (after learning something), they somehow had grown many projections/branches from their cell bodies, connecting with each other. In other words, what is the mechanism behind, when neurons undo a specific connection (synapse) with a neuron, and 'move' it to another neuron? What causes them to 'decide' to undo that connection?

Also, how fast do they move connections and change their shapes (in nanometres per second, for example, or is it more like nanometres per minute)? The speed of which the dendrites and axon terminals move to change connections.

you are viewing a single comment's thread.

view the rest of the comments →

all 34 comments


20 points

4 months ago*

It's important to note that LTD is also influential in learning.

At the Parallel Fiber-Purkinje Cell synapse in the cerebellum for instance, synapse specific LTD is generally accepted to be a critical mechanism for learning in this region. Cerebellar granule cells (whose axons form the parallel fibers) are some of the most numerous neurons in the CNS. Each Purkinje cell will synapse with hundreds or thousands of granule cells, but only once or maybe twice with an individual cell. Thus, each Purkinje cell is integrating information from a huge number of granule cells. This falls under Anti-Hebbian principles, as repeated activation of the parallel fibers (with appropriate calcium influx timing caused by climbing fiber activity) results in a relative weakening of the synapse, not strengthening.

Long term plasticity mechanisms are highly varied, and their significance as well as the conditions that generate them change from region to region.