Figure 8.

Activity Patterns for Spontaneous Contra- and Ipsiversive Turns Are Co-activated in Layer 2/3 during Visual Offset Perturbation-Induced Turns

(A) Projections of the population vector during spontaneous contraversive (blue) and spontaneous ipsiversive (red) executed throughout training (days 1 to 8) onto the plane spanned by the population vector 1 s after turn onset during spontaneous contraversive and spontaneous ipsiversive turns. Origin of the coordinate system is the mean population vector preceding turns. Shading of the maker indicates time relative to turn onset. We then projected the population activity vector during induced contraversive (cyan) and induced ipsiversive turns (magenta) executed during training days 3 to 8 onto the same coordinate system. Black crosses mark the first bin with the first significant change in turning velocity following visual offset perturbation. Error bars indicate SEM over turns. Dashed black line marks line of unity.

(B) As in (A), but for layer 5 PT responses.

(C) Model for the response of motor cortex to unexpected feedback perturbations. In an initial phase of the response, multiple assemblies of neurons, the activity of which we speculate corresponds to different motor plans, are co-activated and primed in layer 2/3. These assemblies could be separately driven by sensory evidence, and potentially directly compete. At a later time, during the movement selection phase of the response, the dominant activation pattern of layer 2/3 can recruit the corresponding assembly in layer 5 that then drives a behavioral response by activating subcortical motor control centers.