Respiratory modulation of neuronal discharge in the central nucleus of the amygdala during sleep and waking states

Zhang JX, Harper RM, and Frysinger RC (1986) Respiratory modulation of neuronal discharge in the central nucleus of the amygdala during sleep and waking states. Exp Neurol 91:1 193–207.

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Abstract: The relationship between neuronal discharge in the central nucleus of the amygdala (ACE) and timing of the respiratory cycle was assessed during quiet and active sleep and during the waking state. Of 169 neurons recorded from the ACE in intact, drug-free cats, 22% discharged phasically with the respiratory cycle during at least one sleep or waking state. The dependency between neuronal discharge and the respiratory cycle was typically strong in only one state. Forty-three percent of the respiratory-related neurons were most strongly correlated with the respiratory cycle during the waking state (AW). An additional 30% were most strongly related to the respiratory cycle during quiet sleep (QS), whereas only 11% showed the strongest dependency during rapid eye movement (REM) sleep. Half of the ACE neurons (49%) discharged at frequencies less than 10 spikes per second, and the most common trend in firing rate across states was one in which neurons fired more rapidly during AW and REM than during QS. No relationship between discharge rate of ACE neurons in the three states and propensity for phasic discharge with the respiratory cycle could be demonstrated.

Context

• Animal study of link between respiration and neural activity in amygdala. One-fifth of neurons in central nucleus fired in phase with respiration. Waking or phase of sleep influenced the dependence. The link of amygdala activity and respiration may underlie the link suggested between temporal lobe epilepsy and apnea. In a study in patients, Frysinger and Harper, 1989 found that about 2% of cells in hippocampus and amygdala showed changes in firing activity with a significant relation to the timing of respiration. If the fact that >20% of neurons in the central nucleus of the amygdala show respiration-related activity patterns is also true in humans, the much lower percentage in Frysinger and Harper, 1989 could be due to infrequent recordings from that site. Removal of all or part of amygdala on one side is often part of epilepsy surgery, so if amygdalar neuron activity influences respiration directly one would predict changes in an individual's respiration after excision. This could be readily tested.