We were stoked and ready before the traffic light turned green before making a turn. In both situations, the brain has planned our exact movements but suppresses their execution until a specific cue (e.g., the shout of GO! or the green light). Now, scientists have discovered the brain network that uses intentions to execute in response to this cue.
The findings, published in the scientific journal Cell, have come from a collaboration of scientists at the Max Planck Florida Institute for Neuroscience, the HHMIs Janelia Research Campus, and the Allen Institute for Brain Science. Dr. Hidehiko Inagaki, Dr. Susu Chen, and senior author Dr. Karel Svoboda have established a team of researchers to develop their understanding of the potential triggers of planned movement.
According to Dr. Inagaki, instruments play varied melodies with different tempos and timbres. Similarly, neurons in the brain are active with diverse timing and patterns. The ensemble of neuronal activities also agpears.
The motor cortex is a brain area that regulates movement. Various patterns in the motor cortex are very different between the planning and execution stages of movement. However, the brain areas that regulate this transition were unknown. Such areas are responsible for environmental cues and orchestrate neuronal activities from one pattern to the next. The conductor ensures that intentions are implemented at the correct time.
Using a cue-triggered movement technique, a mouse assessed the activity of hundreds of neurons simultaneously. This technique was repeated and followed by a mouse. However, the animals had to postpone their movement until a tone was given. Only correct movements would be rewarded. Therefore, mice maintain a plan of the direction they will lick until the go cue and execute the planned lick after.
Complex neural activity patterns were then correlated to relevant stages of the behavioral task, according to the researchers. This brain activity arose immediately following the go cue and during the switch between motor planning and execution. This brain activity arose from a circuit of neurons in the midbrain, thalamus, and cortex.
The scientists optedogenetics to test whether this circuit was capable of handling the conductor. This technique enabled the mouse''s brain activity to move from motor planning to execution, but caused the mouse to stick. On the other hand, turning off the circuit while playing the go cue suppressed the cue''s movement. The mice remained in a motor planning stage as if they had not received the go cue.
This work by Dr. Inagaki and his colleagues uncovered a neural circuit that is essential for triggering movement in response to environmental concerns. Dr. Inagaki explains how their findings demonstrate generalizable features of behavioral control. We have found a circuit that can, therefore, affect the brain''s activities from motor planning to execution at the appropriate time. This research will focus on how this circuit and others reorganize neuronal activity across many brain regions.
This study, based on major advancements in understanding how the brain functions, has profound clinical implications. Patients with Parkinson''s disease have difficulty in self-initiated movement, including difficulty walking. However, adding environmental cues to trigger movements, such as lines on the floor, may significantly improve their mobility. This phenomenon, referred to as paradoxical kinesia, suggests that different mechanisms in the brain are recruited for self-initiated movement and cue-triggered movement. This research may help to understand how the