Lighter or Heavier Than Predicted: Neural Correlates of Corrective Mechanisms during Erroneously Programmed Lifts

Abstract

A central concept in neuroscience is that the CNS signals the sensory discrepancy between the predicted and actual sensory consequences of action. It has been proposed that the cerebellum and parietal cortex are involved in this process. A discrepancy will trigger preprogrammed corrective responses and update the engaged sensorimotor memories. Here we use functional magnetic resonance imaging with an event-related design to investigate the neuronal correlates of such discrepancies. Healthy adults repeatedly lifted an object between their right index fingers and thumbs, and on some lifting trials, the weight of the object was unpredictably changed between light (230 g) and heavy (830 g). Regardless of whether the weight was heavier or lighter than predicted, activity was found in the right inferior parietal cortex (supramarginal gyrus). This suggests that this region is involved in the comparison of the predicted and actual sensory input and the updating of the sensorimotor memories. When the object was lighter or heavier than predicted, two different types of preprogrammed force corrections occurred. There was a slow force increase when the weight of the object was heavier than predicted. This corrective response was associated with activity in the left primary motor and somatosensory cortices. The fast termination of the excessive force when the object was lighter than predicted activated the right cerebellum. These findings show how the parietal cortex, cerebellum, and motor cortex are involved in the signaling of the discrepancy between predicated and actual sensory feedback and the associated corrective mechanisms.

Observing how others lift light or heavy objects: Which visual cues mediate the encoding of muscular force in the primary motor cortex?

“…Even though our data are in good agreement with the current mirror neuron theory, an alternative, not mutually exclusive interpretation can be that the experimental context activated movement representations in terms of stored internal models (Bursztyn, Ganesh, Imamizu, Kawato, & Flanagan, 2006;Jenmalm, Schmitz, Forssberg, & Ehrsson, 2006). More specifically, experiment 2 showed that the presentation of tension/pressure cues on grip force was sufficient to mediate force-related activity within the observer's M1.…”

“…More specifically, similar to the way that the sight of an object can recruit internal models for scaling the forces needed to handle the object ) the sight of different levels of hand contraction may have induced the activation of stored internal motor representations for scaling the observed isometric forces. In this respect, the elicited M1 responses might have been driven by other pathways than those predicted by the mirror neuron theory, potentially involving the cerebellum (Bursztyn et al, 2006;Jenmalm et al, 2006).…”

Weight Lifting in the Human Brain

“…Weight changes led to increased activity in the right inferior parietal cortex [Jenmalm et al (2006) (Desmurget et al, 1999). Together, these data and the location and connectivity of this region, receiving input from sensory cortices and having output connections to the motor regions, make it a good candidate for "comparator region.…”

“…Jenmalm et al (2006) have made a significant contribution to this topic using functional magnetic resonance imaging in a study recently published in the Journal of Neuroscience.…”

“…The left primary sensorimotor cortex became more active when the weight was increased and less active when the weight was decreased [Jenmalm et al (2006), their Fig. 4 A (http://www.jneurosci.org/cgi/content/ full/26/35/9015/F4)].…”