There were some really good papers last month. The three I picked to summarize all involve error-based learning on fast time-scales. One involves the cerebellum in monkeys, the other involves the songbird system in…songbirds. One reason I like these examples is because they illustrate how deeply error-sensitivity is knitted into basic sensorimotor loops in non-human species. This is not really news in neuroscience, but superficially contradicts some philosophers who seem to be providing transcendental arguments that discursive linguistic practices are a necessary condition for the possibility of error.  Anyway, let’s check out the science.
Singin’ in the dopamine! Birdsong plasticity

Hisey, E, Kearney, MG, and Mooney, R (2018) A common neural circuit mechanism for internally guided and externally reinforced forms of motor learning. Nat Neurosci 21: 589-597. [Pubmed]
Xiao, L, Chattree, G, Oscos, FG, Cao, M, Wanat, MJ, and Roberts, TF (2018) A Basal Ganglia Circuit Sufficient to Guide Birdsong Learning. Neuron 98: 208-221. [Pubmed]
Here we have two elegant papers showing that birds can learn to adjust individual notes in their songs in response to brief pulses of dopamine. While many of us tend to think of the dopaminergic system as an extremely course, slow reinforcement signal, these papers suggest that it can act very quickly to reinforce specific actions embedded in complex behavioral contexts.
Note if you don’t like words, there is a nice video explaining the basic results posted at the bottom of this summary.
For decades, the birdsong system has been a workhorse for the study of socially acquired vocal behavior. This vocal learning occurs in two main stages: first, during the sensory learning phase, a fledgling male memorizes a tutor song from a conspecific adult male. Then, in the sensorimotor learning phase, he will slowly come to reproduce that tutor song himself. He will start by generating discordant, uncoordinated songs, and slowly shaping his vocalizations until the song closely resembles the tutor song. A typical song will have a rich internal structure like that in the figure.
Sensorimotor learning requires auditory feedback, as the animal shapes its behavior by comparing its its current song to the memorized tutor song (Mooney, 2009). Consider what it is like when you are singing a tune and need to hit B-flat. You can hear how close you are to the target. For instance, if you are coming in a bit sharp, you will try to push your pitch down a bit for that particular note.
Similarly, birds are extremely sensitive to errors in individual notes in their songs. If you add annoying white noise (WN) when one of their notes is below a certain pitch, songbirds adjust their pitch upward on that note in order to escape the noise. In the figure below, ‘Pitch-dependent auditory feedback’, you can see this in action. When note ‘d’ is above a certain pitch, that is an escape trial, and the bird is left alone. But when it is below that threshold, we have a ‘hit’ trial and WN is played. Over the course of two days (WN1 and WN2, compared to baseline day B1), the animal slowly increases the pitch of that individual note, to avoid the annoying WN pips.

Dopamine as an internal reinforcer for song plasticity
What is the underlying neural mechanism for such spectral plasticity? One nice thing about the birdsong system is that it has been relatively well mapped anatomically. For instance, there is a dopaminergic region, the ventral tegmental area (VTA), and neurons in this region are modulated by how close notes are to their target notes (Gada...