NOXIOUS STIMULATION EXCITES NEURONS IN THE BASOLATERAL AMYGDALA WITH A SHORT LATENCY
Dániel Magyar1, Gergő A. Nagy1, Judit M. Veres1, Zsófia Reéb and Norbert Hájos1
1 ‘Lendület’ Laboratory of Network Neurophysiology, Institute of Experimental Medicine, Budapest, Hungary
The basolateral amygdala complex (BLA) plays an essential role in Pavlovian fear conditioning, when mice learn to associate a neutral cue (CS) with an aversive, unconditioned stimulus (US), like a mild electrical shock. The BLA consists of distinct nuclei, including the lateral (LA), and basal nuclei (BA), however our knowledge is limited how the information gets processed within these structures during fear conditioning. The current ‘serial’ model states that the pairing of the CS and US occurs in the LA followed by the information transfer into the BA. Here, we examined how electrical shocks excite neurons in both the LA and BA to get insights into the information flow within the BLA upon US delivery. In our experiments, we used silicon probes in awake, head-fixed mice to simultaneously record single-units from both the LA and BA during US delivery. We observed that a portion of neurons discharged action potentials upon shock delivery with a short (<30 ms) latency. Surprisingly, these neurons could be found both in the LA and BA. To validate our results, we repeated the US presentation in anesthetised mice, while spiking activity was detected by juxtacellular recordings followed by intracellular labelling. The results of these experiments confirmed that some neurons located both in the LA and BA were indeed excited by the US with a short latency. These findings indicate that the noxious signal is processed by BLA circuits not in a serial, but in a parallel manner.