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Updated: Aug 10, 2025
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Measuring and Manipulating Functionally Specific Neural Pathways in the Human Motor System with Transcranial Magnetic Stimulation
Published on: February 23, 2020
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A Short Route for Reach Planning between Human V6A and the Motor Cortex.
Rossella Breveglieri1, Sara Borgomaneri2,3, Stefano Diomedi4
1Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, Italy rossella.breveglieri@unibo.it.
Summary
The medial posterior parietal cortex (hV6A) sends inhibitory signals to the frontal cortex in just 4 ms during reach planning. This rapid parieto-frontal pathway is crucial for movement and functions regardless of visual target information.
Area of Science:
- Neuroscience
- Motor Control
- Cognitive Neuroscience
Background:
- The medial posterior parietal cortex, specifically area V6A (hV6A), is known to encode spatial target information for reaching movements.
- A parieto-frontal pathway, connecting hV6A to premotor cortex and primary motor cortex (M1), is hypothesized to transmit this spatial information for reach planning.
Purpose of the Study:
- To investigate the timing and functional connectivity of the human parieto-frontal pathway during reaching movement planning.
- To determine the temporal dynamics of inhibitory signals flowing from hV6A to M1 during different types of reaching tasks.
Main Methods:
- Utilized dual-site, paired-pulse transcranial magnetic stimulation (TMS) to probe functional connectivity between human area V6A (hV6A) and primary motor cortex (M1).
- Administered TMS with short (4 ms) and long (10 ms) interstimulus intervals while participants planned visually-guided or memory-guided reaching movements.
- Measured modulations in motor-evoked potentials (MEPs) over M1 to assess inhibitory influences from hV6A.
Main Results:
- Stimulation of hV6A 4 ms prior to M1 stimulation resulted in inhibition of M1 motor-evoked potentials during reach planning.
- No significant modulations were observed when the interstimulus interval was 10 ms, indicating a rapid functional connection.
- This short-latency inhibition from hV6A to M1 occurred irrespective of whether the reaching target was visually guided or memory-guided.
Conclusions:
- Established the existence of a fast (4 ms) inhibitory signaling pathway between human V6A and M1 during reach planning.
- Demonstrated that this rapid parieto-frontal communication is essential for movement planning and is not dependent on visual target availability.
- Provides crucial insights into the temporal dynamics of motor control networks, opening avenues for studying neurological disorders affecting motor planning.
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