Activity of the Motor Cortex During Scratching

Abstract

. In awake cats sitting with the head restrained, scratching was evoked using stimulation of the ear. Cats scratched the shoulder area, consistently failing to reach the ear. Kinematics of the hind limb movements and the activity of ankle muscles, however, were similar to those reported earlier in unrestrained cats. The activity of single neurons in the hind limb representation of the motor cortex, including pyramidal tract neurons (PTNs), was examined. During the protraction stage of the scratch response, the activity in 35% of the neurons increased and in 50% decreased compared with rest. During the rhythmic stage, the motor cortex population activity was approximately two times higher compared with rest, because the activity of 53% of neurons increased and that of 33% decreased in this stage. The activity of 61% of neurons was modulated in the scratching rhythm. The average depth of frequency modulation was 12.1 Ϯ 5.3%, similar to that reported earlier for locomotion. The phases of activity of different neurons were approximately evenly distributed over the scratch cycle. There was no simple correlation between resting receptive field properties and the activity of neurons during the scratch response. We conclude that the motor cortex participates in both the protraction and the rhythmic stages of the scratch response.

Cortical GluK1 kainate receptors modulate scratching in adult mice

“…Importantly, the ACC receives robust projections from the thalamus (Lee et al 2007), forms multiple reciprocal connections with other cortical areas (Vogt 2005), including the motor cortex, Leknes et al 2007), and contributes to descending facilitation of spinal cord transmission (Calejesan et al 2000). Accordingly, we observed that scratching behavior corresponded to ACC activity, and scratching has been shown to correspond with motor cortex activity (Sirota et al 2006). Similarly, neuroimaging studies have observed co-activation of the ACC, supplementary, and pre-motor areas in correspondence with the urge to scratch in humans (Hsieh et al 1994;Leknes et al 2007).…”

“…Accordingly, we observed that scratching behavior corresponded to ACC activity, and scratching has been shown to correspond with motor cortex activity (Sirota et al . ). Similarly, neuroimaging studies have observed co‐activation of the ACC, supplementary, and pre‐motor areas in correspondence with the urge to scratch in humans (Hsieh et al .…”