Selective corticostriatal plasticity during acquisition of an auditory discrimination task
Qiaojie Xiong, Petr Znamenskiy & Anthony M. Zador
Nature (2015)
doi:10.1038/nature14225
The conceptual gap or the scientific question: could the corticostriatal plasticity encode the stimulus-action association during learning?
How the authors proposed the question: their previous findings (shared in 2021-08-25Good control means deliberate considerations about the alternative possibilities - 简书 (jianshu.com)) shown that the corticostriatal projections from the auditory cortex to the auditory striatum are cricital for making decisions in a auditory two alternative falced choice task. So they want to know whether the plasticity within this pathway could underlie the learning process?
Brief summary: by developing a novel method to measure the synaptic plasticity of corticostriatal connectivity, the authors found that the ChR2 facilitated measurement of the local field potential (LFP) could efficiently quantify the excitatory connectivity strength in the auditory striatum, and the ChR2-LFP based plasticity specifically encoded the learned tone-action associations, both in modality- and spatial-map- dependent manners.
The novel of this study resides in two aspects at least. First, they developed an efficient tool to measure the plasticity of the corticostriatal connection based on the LFP signals. Two facts make this measurement feasible: there are only excitatory connnections in this corticostriatal pathway; there are no recurrent excitation within the striatum. To solidify the feasibility of the tool, they performed a series of control measurement to shown that this metric was robust to the light intensity and was proportional to the intracellular excitatory postsynaptic current. Maybe this tool could be applied in my own study.
The finding that the LFP-based plasticity could encode the stimulus-action (S-A) associations was also impressive. However, at the single neuron level, I guess it will be much more challenging to observe such a dichotomous coding patterns for these two S-A associations, especially for the observed spatial gradients, because much more heterogenities exist at the single neuron level.
So one lesson is at some situations a relatively coarse approach could be more suited for drawing general claims and making a fantastic story than that of the elaborate tools.
By the way, they did not build a causal relationship between the obseved plasticity and learning. It's a pity. But from the opposite side, it also exemplifies a good strategy to weave a beautiful story for selling, even though without causal manipulations.
The ongoing question(s) inspired by the current study: could the S-A association specific plasticity be recapitulated at the single neuron level?
