@article{Representations:5713,
      recid = {5713},
      author = {Liang, Wei},
      title = {Space: The Final Frontier in Dynamic Representations in  Motor Cortex},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2023-03},
      pages = {197},
      abstract = {The primary motor cortex (M1) is known for its general  static correspondence between body parts and clustered  sites on the physical cortical sheet – the somatotopic map.  Under this view, it’s tempting to believe that the  orchestration of motor output in M1 is as rigid as  manipulating the movement of a marionette, where a fixed  set of strings would reliably dictate the movements of  corresponding body parts of the puppet. In this thesis  work, we argue that motor representation on the M1 cortical  sheet is in fact dynamic, from two perspectives: (1) the  relationship between neural activity and muscle output is  dynamic along movement execution; (2) the  information-bearing neural activity itself is dynamically  patterned across the cortical sheet during movement  execution.
The first part of the work shows that, rather  than being a static mapping, the relationship between  neural activity and muscle output is constantly evolving  during simple point-to-point reaches. Any given location on  the cortical sheet bears the most information about  different muscles at different times; any muscle is  represented by different cortical locations at different  times. Furthermore, this dynamic representation is  movement-specific and most stable around movement onset,  possibly serving functional needs. These dynamics happen at  significantly shorter time scales than training-induced  neural plasticity, presumably reflecting neural  multiplexing unfolding over time.
The second part of the  work shows that during movement execution M1 recruits  spatially organized patterns of activity across the  cortical sheet in a behaviorally specific manner. In  particular, recruitment times form planar propagating  patterns across the cortical sheet. The directions of those  propagating patterns differ systematically according to  reach directions, bearing important kinematic information.  This finding expands the repertoire of spatio-temporally  complex neural codes and points to their potential  facilitative roles in neural computation. 
Together, this  work speaks to the dynamic motor representation of the  physical M1 cortical sheet. The effects that cortical  activities have on the motor outputs are best understood by  considering the interplay between space and time in  characterizing population neural activity, and by  considering the dynamic mapping between the cortex and  effectors. 
},
      url = {http://knowledge.uchicago.edu/record/5713},
      doi = {https://doi.org/10.6082/uchicago.5713},
}