Human speech and birdsong have numerous parallels, with striking similarities in how sensory experience is internalized and used to shape vocal outputs, and how learning is enhanced during a critical period of development.
A previously unappreciated capacity of the AFP to direct real-time changes in song is demonstrated and frontal cortical and basal ganglia areas may contribute to motor learning by biasing motor output towards desired targets or by introducing stochastic variability required for reinforcement learning.
The results show that the STRF model is an incomplete description of response properties of nonlinear auditory neurons, but that linear receptive fields are still useful models for understanding higher level sensory processing, as long as the STRFs are estimated from the responses to relevant complex stimuli.
These findings provide evidence that cortical-basal ganglia circuits may participate in the evaluation of sensory feedback during calibration of motor performance, and demonstrate that damage to such circuits can have little effect on previously learned behaviour while conspicuously disrupting the capacity to adaptively modify that behaviour.
The auditory response properties of neurons in the anterior forebrain (AF) pathway of the songbird brain were investigated and provided one of the clearest examples of experience-dependent acquisition of complex stimulus selectivity.
With the discovery and investigation of discrete brain structures required for singing, songbirds are providing insights into neural mechanisms of learning and are addressing such basic issues in neuroscience as perceptual and sensorimotor learning, developmental regulation of plasticity, and the control and function of adult neurogenesis.
Extracellular single neuron recordings in 60-d-old zebra finches revealed that AF neurons had significant song and order selectivity for both tutor song and BOS (the bird’s plastic song), raising the possibility that both aspects of the birds’ sensory experience during learning are reflected in properties of AF neurons.
This study obtains neural responses from several regions of the songbird auditory forebrain to a large ensemble of bird songs and uses this data to calculate the spectral temporal receptive field (STRFs), which are the best linear model of the spectral-temporal features of sound to which auditory neurons respond.
The results suggest that there is a song-selective pathway directly from HVc to RA in addition to the circuit via L-MAN, suggesting that the songbird brain contains multiple auditory pathways specialized for song, which may vary in their functional importance at different stages of learning.
It is shown that, in the adult zebra finch, the pattern of singing-related neural activity in several high-level brain areas specialized for song learning is dependent on whether a bird sings by itself or to another bird; thus, this activity can indicate not only that a bird is singing but also the social context of the song.