Behavior and neural circuits are shaped during developmental phases known as sensitive or critial periods. During sensitive periods, enhanced nueral plasticity enables environmental factors to shape developing circuits and behavior. Four cellular features characterize the primary visual cortex during the critical period for ocular dominance plasticity. These features are prolonged bursting, expression of the calcium-bindind protein parvalbumin (PV), extracellular matrix perineuronal nets(PNNs), and changes in excitatory-inhibitory balance. PV is characteristic of fast-spiking neurons, typically interneurons. All of these cellular features are related to inhibitory interneurons because GABA neurotransmission decreases the incidence of prolonged bursts.
Prolonged discharge is thought to reflect an immature state of neural circuitry. Increased inhibitory interneuron activity and the presence of PV mark the beginning of experience-dependent plasticity. The presence of PNNs signals the end of the critical period for plasticity in not only vision but other sensory systems as well. Humans and songbirds learn their vocalizations early in life during a two-part sensitive period. This two-part period consists of an early perceptual phase where species-typical sounds are memorized, followed by a later sensorimotor imitative phase where auditory feedback is used to shape emitted sounds.
The song nucleus HVC is the center of auditory and motor pathways of the song system. Recent information from the HVC suggest cellular parallels between the sensorimotor period of the song system and the visual critical period. HVC premotor activity is developmentally regulated and these changes in activity relate to behavior. Like the visual cortex during ocular dominance plasticity, the immature song nucleus HVC exhibits prolonged bursting. In addition, fast-spiking putative interneurons fire before, during, and after song behavior during sensorimotor learning but not later in development.
Posted by Tiffany Mallet
http://www.jneurosci.org/cgi/reprint/29/41/12878
It's really interesting that scientists are figuring out the complex system of song learning. Not much is known about the learning pathway in birds. How much more needs to be known before the whole mystery is unraveled?
ReplyDelete-Tricia Carlson
This is a very interesting article. It is unbelievable that scientist were able to figure out how birds learn there songs and all the critical stages of song learning development. Now after reading this article, now they know how the wiring and all the neurological work involved in song learning. It boggles my mind to how scientists figure these complex systems out.
ReplyDeleteCarlos Varela
It's so interesting how complex song learning is. What types of experiments provided scientists with clues as to how this works?
ReplyDelete-Sarah Benjamin
I agree that bird song learning is very complex and it is amazing what we have found out about it. What I found interesting about this article was that they found similarities in bird song learning to human speech learning. I wonder if this critical period in birds can be seen in humans at a young age. Perhaps this is why younger children are so much better at learning a foreign language. As to the experiments the scientists conducted to come up with their results this is a summary of what was done: "The percentage of both total and parvalbumin-positive neurons with perineuronal nets increased with development. In HVC (this acronym is the proper name), a song area important for sensorimotor integration, the percentage of parvalbumin neurons with perineuronal nets correlated with song maturity. Shifting the vocal critical period with tutor song deprivation decreased the percentage of neurons that were parvalbumin positive and the relative staining intensity of both parvalbumin and a component of perineuronal nets. Developmental song learning shares key characteristics with sensory critical periods, suggesting shared underlying mechanisms." I hoped that answered your question. Thanks for the comments!
ReplyDeleteRevised by Tiffany Mallet