Normal human brain processing of cold stimulation observed by magneto-encephalography

We investigated the time course of cortical activity in the brain related to cold epidermal touch stimulation at 4 degree Celsius and touch stimulation at a normal temperature of 14 degree Celsius to the palm of the hand in 20 normal human subjects (average age of 29.1plusmn6.0 years), using magneto-encephalography (MEG). The time course of cortical activities with cold touch stimulation to the right palm showed cortical activities in the posterior portion of the posterior cingulate cortex at an average of 214plusmn 101.2 ms before cold touch stimulation, in the ipsilateral somatosensory area at an average of 39.6plusmn37.5 ms, in the contralateral primary somatosensory area at an average of 64.8plusmn28.4 ms, and then in the anterior cingulate cortex, including a portion of the corpus callosum, at an average of 302plusmn126 ms, following cold touch stimulation. It was noted that the time course of cortical activities to cold touch stimulation to the palm showed a difference, compared with normal temperature touch stimulation: cortical activities were observed in the ipsilateral sensory region at an average of 39.6plusmn37.5 ms following cold touch stimulation, but such activities were not observed following normal temperature touch stimulation. On the other hand, there were no significant differences in the time courses of cortical activities in the contralateral primary sensory area and in cingulate regions between the two types of stimulation. The time course of brain activities in response to epidermal stimulation showed no laterality or gender difference.