Highlights d Central lateral thalamic stimulation arouses macaques from stable anesthesia d Thalamic and deep-layer cortical spiking correlate with consciousness level d Consciousness depends on feedforward, feedback, and intracolumnar signaling d Pathway-specific signaling operates at alpha and gamma during consciousness

The primary motor cortex of mammals has an orderly representation of different body parts. Within the representation of each body part the organization is more complex, with groups of neurons representing movements of a muscle or a group of muscles. In rats, uncertainties continue to exist regarding organization of the primary motor cortex in the whisker and the neck region. Using intracortical microstimulation (ICMS) we show that movements evoked in the whisker and the neck region of the rat motor cortex are highly sensitive to the depth of anaesthesia. At light anaesthetic depth, whisker movements are readily evoked from a large medial region of the motor cortex. Lateral to this is a small region where movements of the neck are evoked. However, in animals under deep anaesthesia whisker movements cannot be evoked. Instead, neck movements are evoked from this region. The neck movement region thus becomes greatly expanded. An analysis of the threshold currents required to evoke movements at different anaesthetic depths reveals that the caudal portion of the whisker region has dual representation, of both the whisker and the neck movements. The results also underline the importance of carefully controlling the depth of anaesthesia during ICMS experiments.

Adult mammalian brains undergo reorganization following deafferentations due to peripheral nerve, cortical or spinal cord injuries. The largest extent of cortical reorganization is seen in area 3b of the somatosensory cortex of monkeys with chronic transection of the dorsal roots or dorsal columns of the spinal cord. These injuries cause expansion of intact face inputs into the deafferented hand cortex, resulting in a change of representational boundaries by more than 7 mm. Here we show that large-scale reorganization in area 3b following spinal cord injuries is due to changes at the level of the brainstem nuclei and not due to cortical mechanisms. Selective inactivation of the reorganized cuneate nucleus of the brainstem eliminates observed face expansion in area 3b. Thus, the substrate for the observed expanded face representation in area 3b lies in the cuneate nucleus.

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