Our brains become active while we prepare to move and they continue to generate electrical signals as those movements are carried out. Signals associated with movements are generated in the motor cortex. A standard assumption has been that signals associated with preparations for a movement are subthreshold forms of the same neural signals associated with the execution of the movement. A new paper titled “Cortical Preparatory Activity: Representation of Movement or First Cog in a Dynamical Machine?” (published November 4, 2010 in Neuron) challenges this assumption.
A key test of the assumption that preparatory activity constitutes a subthreshold precursor of movement activity is that the two should share similar tuning to the preferred direction of movement. The data show that the majority of the time this isn’t the case. Most of the time preparatory activity is tuned to a significantly different preferred direction than the movement activity.
What is the nature of signal processing during the preparatory and movement phases of motor activity? How are they related? The authors argue that “preparatory activity exists not to represent specific movement features but to initialize a dynamical system whose evolution will produce perimovement activity.”
Note: Perimovement activity is the neural activity occurring at the same time that the movement is being carried out.
We took a peak at how the dynamical systems approach may help us understand signal processing in a single neuron in my earlier blog post “Dynamical Systems and Silicon Based Hybrid Spiking Neurons.” In today’s paper, the conclusion is intriguing but left me wondering exactly how dynamical systems may illuminate signal processing in the motor cortex.
