On STDP from Behavior

Figure 6 from ref. 1


I've written several times about Spike-Timing-Dependent-Plasticity (STDP), one method by which the individual neurons in the mammalian brain learn; changing their responses to the signals sent from other neurons.

It is believed that STDP is a major route of such learning, both during development and in the adult animal; for instance potentially underlying the associative conditioning famously demonstrated by Pavlov. Indeed, it is just this sort of patterned external sensory stimulus (bell then food) that represents a candidate for learning through STDP. However, connecting the presence of structured environmental variables and underlying brain changes has proven a difficult experimental challenge.

A recent piece of research has achieved just such a feat in the optic tectum of a non-mammal, the developing frog Xenopus laevis¹.

I found the figure above to be the most intriguing result from the paper sumarrizing these experiments, published in Nature Neuroscience. The image represents the finding that if the tadpoles are exposed to repetitive flashes of light with a specific time difference between them (top), the neurons in their optic tecta respond by adjusting the latency (time from stimulus to response) of their spike-reactions to single, isolated flashes (middle: neural activity, bottom: histograms of spike latencies).

I am encouraged by this work because it bridges what is currently a rather formidable gap. That between understanding the brain at the level of single neurons and the behavior of an animal as a whole.


References:

1. Pratt, KG, Dong, W & Aizenman, CD (2008) Development and spike timing–dependent plasticity of recurrent excitation in the Xenopus optic tectum Nature Neuroscience 11, 467-475 | doi:10.1038/nn2076