Lockmann André Luiz Vieira, Mourão Flávio Afonso Gonçalves, Moraes Marcio Flávio Dutra
Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
Núcleo de Neurociências, Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
J Neurophysiol. 2017 Aug 1;118(2):1012-1020. doi: 10.1152/jn.00293.2017. Epub 2017 Apr 26.
The rat inferior colliculus (IC) is a major midbrain relay for ascending inputs from the auditory brain stem and has been suggested to play a key role in the processing of aversive sounds. Previous studies have demonstrated that auditory fear conditioning (AFC) potentiates transient responses to brief tones in the IC, but it remains unexplored whether AFC modifies responses to sustained periodic acoustic stimulation-a type of response called the steady-state evoked potential (SSEP). Here we used an amplitude-modulated tone-a 10-kHz tone with a sinusoidal amplitude modulation of 53.7 Hz-as the conditioning stimulus (CS) in an AFC protocol (5 CSs per day in 3 consecutive days) while recording local field potentials (LFPs) from the IC. In the preconditioning session (), the CS elicited prominent 53.7-Hz SSEPs. In the training session (), foot shocks occurred at the end of each CS (paired group) or randomized in the inter-CS interval (unpaired group). In the test session (), SSEPs markedly differed from preconditioning in the paired group: in the first two trials the phase to which the SSEP coupled to the CS amplitude envelope shifted ~90°; in the last two trials the SSEP power and the coherence of SSEP with the CS amplitude envelope increased. LFP power decreased in frequency bands other than 53.7 Hz. In the unpaired group, SSEPs did not change in the test compared with preconditioning. Our results show that AFC causes dissociated changes in the phase and power of SSEP in the IC. Local field potential oscillations in the inferior colliculus follow the amplitude envelope of an amplitude-modulated tone, originating a neural response called the steady-state evoked potential. We show that auditory fear conditioning of an amplitude-modulated tone modifies two parameters of the steady-state evoked potentials in the inferior colliculus: first the phase to which the evoked oscillation couples to the amplitude-modulated tone shifts; subsequently, the evoked oscillation power increases along with its coherence with the amplitude-modulated tone.
大鼠下丘（IC）是来自听觉脑干的上行输入的主要中脑中继站，并且已被认为在厌恶声音的处理中起关键作用。先前的研究表明，听觉恐惧条件反射（AFC）增强了下丘对短暂音调的瞬态反应，但AFC是否会改变对持续周期性声刺激（一种称为稳态诱发电位（SSEP）的反应类型）的反应仍未得到探索。在这里，我们使用调幅音（一个10kHz的音调，正弦调幅为53.7Hz）作为AFC方案（连续3天每天5次条件刺激）中的条件刺激（CS），同时记录下丘的局部场电位（LFP）。在预处理阶段（），条件刺激引发了明显的53.7Hz稳态诱发电位。在训练阶段（），足部电击在每个条件刺激结束时发生（配对组）或在条件刺激间隔期随机发生（非配对组）。在测试阶段（），配对组的稳态诱发电位与预处理阶段明显不同：在前两次试验中，稳态诱发电位与条件刺激幅度包络耦合的相位偏移了约90°；在最后两次试验中，稳态诱发电位的功率以及稳态诱发电位与条件刺激幅度包络的相干性增加。在53.7Hz以外的频段局部场电位功率下降。在非配对组中，测试时的稳态诱发电位与预处理相比没有变化。我们的结果表明，听觉恐惧条件反射导致下丘稳态诱发电位的相位和功率发生分离变化。下丘的局部场电位振荡跟随调幅音的幅度包络，产生一种称为稳态诱发电位的神经反应。我们表明，调幅音的听觉恐惧条件反射改变了下丘稳态诱发电位的两个参数：首先，诱发振荡与调幅音耦合的相位发生偏移；随后，诱发振荡功率随着其与调幅音的相干性增加而增加。
