Motor Learning of Compatible and Incompatible Visuomotor Maps

Abstract

Brain imaging studies demonstrate increasing activity in limb motor areas during early motor skill learning, consistent with functional reorganization occurring at the motor output level. Nevertheless, behavioral studies reveal that visually guided skills can also be learned with respect to target location or possibly eye movements. The current experiments examined motor learning under compatible and incompatible perceptual/motor conditions to identify brain areas involved in different perceptual-motor transformations. Subjects tracked a continuously moving target with a joystick-controlled cursor. The target moved in a repeating sequence embedded within random movements to block sequence awareness. Psychophysical studies of behavioral transfer from incompatible (joystick and cursor moving in opposite directions) to compatible tracking established that incompatible learning was occurring with respect to target location. Positron emission tomography (PET) functional imaging of compatible learning identified increasing activity throughout the precentral gyrus, maximal in the arm area. Incompatible learning also led to increasing activity in the precentral gyrus, maximal in the putative frontal eye fields. When the incompatible task was switched to a compatible response and the previously learned sequence was reintroduced, there was an increase in arm motor cortex. The results show that learning-related increases of brain activity are dynamic, with recruitment of multiple motor output areas, contingent on task demands. Visually guided motor sequences can be linked to either oculomotor or arm motor areas. Rather than identifying changes of motor output maps, the data from imaging experiments may better reflect modulation of inputs to multiple motor areas.

Cerebral Changes during Performance of Overlearned Arbitrary Visuomotor Associations

“…through an appropriate spatial transformation (Grafton et al, 2001;Eliassen et al, 2003); however, here the location of the stimuli was not related to the motor response, and PPC activity showed a learning-related decrease during initial learning (Fig. 4 A), confirming previous reports (Deiber et al, 1997;Toni et al, 2001a).…”

Repetitive Transcranial Magnetic Stimulation to the Primary Motor Cortex Interferes with Motor Learning by Observing

“…Electrophysiological recordings in monkey have shown that M1 neurons change their firing patterns in response to practice in externally applied force fields (Li, Padoa-Schioppa, & Bizzi, 2001;Gandolfo, Li, Benda, Padoa-Schioppa, & Bizzi, 2000), joint-specific viscous loads (Gribble & Scott, 2002), constant bias forces (Kalaska, Cohen, Hyde, & Prud'homme, 1989), and visuomotor rotations (Paz, Natan, Boraud, Bergman, & Vaadia, 2005). Functional brain imaging studies have established that M1, in addition to other motor system brain areas, plays a key role in human motor learning about new movement sequences (Karni et al, 1998), visuomotor rotations (Paz, Boraud, Natan, Bergman, & Vaadia, 2003;Grafton, Salidis, & Willingham, 2001), and externally applied force fields (Shadmehr & Holcomb, 1997). Moreover, low-frequency rTMS applied to the motor cortex can interfere with learning of tasks that involve the acquisition of new relationships between kinematics and dynamics (Cothros et al, 2006;Chouinard et al, 2005;Muellbacher et al, 2002).…”

Neural Substrates of Response-based Sequence Learning using fMRI

“…In previous work, we identified different patterns of activation for sequences learned under single-and dual-task conditions. This work demonstrated that both attentional distraction and the awareness of sequence structure interact with the neural substrates of sequence acquisition (Grafton et al, 1995;Grafton, Salidis, & Willingham, 2001;Hazeltine et al, 1997). To minimize the impact of these complex interactions for interpreting functional imaging data, the task in the present study was performed without secondary distraction of attention.…”