Triggering Different Brain States Using Asynchronous Serial Communication to the Rat Amygdala

Abstract

Inputting information to the brain through direct electrical microstimulation must consider how underlying neural networks encode information. One unexplored possibility is that a single electrode delivering temporally coded stimuli, mimicking an asynchronous serial communication port to the brain, can trigger the emergence of different brain states. This work used a discriminative fear-conditioning paradigm in rodents in which 2 temporally coded microstimulation patterns were targeted at the amygdaloid complex. Each stimulus was a binary-coded "word" made up of 10 ms bins, with 1's representing a single pulse stimulus: A-1001111001 and B-1110000111. During 3 consecutive retention tests (i.e., day-word: 1-B; 2-A, and 3-B), only binary-coded words previously paired with a foot-electroshock elicited proper aversive behavior. To determine the neural substrates recruited by the different stimulation patterns, c-Fos expression was evaluated 90 min after the last retention test. Animals conditioned to word-B, after stimulation with word-B, demonstrated increased hypothalamic c-Fos staining. Animals conditioned to word-A, however, showed increased prefrontal c-Fos labeling. In addition, prefrontal-cortex and hypothalamic c-Fos staining for, respectively, word-B- and word-A-conditioned animals, was not different than that of an unpaired control group. Our results suggest that, depending on the valence acquired from previous learning, temporally coded microstimulation activates distinct neural networks and associated behavior.

Differential Effects of Open- and Closed-Loop Intracortical Microstimulation on Firing Patterns of Neurons in Distant Cortical Areas

“…No differences were found in the LvR analysis ( 7), suggesting that the pairing of neural activity and stimulation may lead to stronger associations over prolonged stimulation sessions. This may result from a number of factors including the temporal distribution of the stimuli and coordination between stimulation and neuronal activity which concern has already been raised by several studies previously (Mourão et al 2015;Nelson et al 2011;Popovych et al 2017;Quinkert et al 2010;Wyckhuys et al 2010a;Wyckhuys et al 2010b). It is likely that the mechanism that increases the effectiveness of ADS is through Hebbianbased spike-timing, which is a method that more closely mimics the nervous system's natural mechanism to promote learning and memory which is typically effective in inducing long-term plasticity (Guggenmos et al 2013;Jackson et al 2006).…”

A Custom Microcontrolled and Wireless-Operated Chamber for Auditory Fear Conditioning

“…The rats were randomly assigned to paired ( n = 5) or unpaired ( n = 5) groups and similarly to the day 1, five CS stimuli were presented, however five US were applied. The US consisted of a 400 μA current applied through metal bars on the floor over 2 s (Mourão et al, 2016). In the paired group, each presentation of CS was temporally paired with US in the last 2 s of the CS presentations.…”

Seizure Susceptibility Corrupts Inferior Colliculus Acoustic Integration

“…Twenty-four hours later, rats returned to the same box for 120 s, but no foot-shock (test phase). Both periods were recorded to offline quantification of the freezing behavior (absence of movements, except the respiratory; Mourão et al, 2016).…”

“…The US was applied at the last 2 s of CS for the paired groups or during the silent periods (20 s minimum separation from the sound stimulus) for the unpaired groups. The preconditioning and test phases were video-recorded for offline quantification of freezing, defined as no movements, except breathing, for a minimum of 3 s within each 5 s time epoch (six epochs for the 30 s; Mourão et al, 2016).…”