Characteristics of thalamic multi-unit activity and EEG during recovery from asphyxia

Rhythmic cortical activity has been shown to have thalamic origin during high voltage spindles in some awake immobile rats. It was also found that EEG showed burst suppression patterns during recovery from a hypoxic/asphyxic insult to the brain. These have been shown to be prognostic of the neurological outcome after the injury. Some of these EEG burst patterns were rhythmic. Therefore, it was hypothesized that these rhythmic patterns also had a thalamic origin. Adult male Wistar rats (n=5) under Sodium Pentobarbital anesthesia were made to undergo a three minute period of asphyxia and then resuscitated. Extra-cellular activity from the ventral posterior medial nucleus was monitored. Cortical EEG was monitored bilaterally over the parietal region. Early recovery period in 4 of the 5 animals was characterized by episodes of sustained periodic discharges in the thalamus which correlated with periodic activity in the EEG. Thus, preliminary evidence indicates thalamic origins for the rhythmic EEG burst patterns observed during recovery from an asphyxic injury.