CAJ | 학술논문

有关听中枢神经元纯音前掩蔽效应的神经表征已进行了大量研究,但是,噪声前掩蔽尤其是间断噪声前掩蔽效应的神经表征却鲜有报道.本研究观察了自由声场条件下,昆明小鼠下丘神经元在持续与间断噪声前掩蔽条件下对纯音探测声的反应.共记录到96个下丘神经元,测量了其中51个神经元在不同声刺激条件下的强度-放电率函数.结果显示,掩蔽声强度分布较广(探测声阈下21 dB至阈上19 dB之间).在将近一半的神经元中,间断噪声的前掩蔽效应比持续噪声强(Ⅰ型,45.10%,P＜0.001),但也有少数神经元其间断噪声的掩蔽效应较持续噪声的弱(Ⅲ型,17.65%,P＜0.001),部分神经元无显著性差异(Ⅱ型,37.25%,P＞0.05).无论Ⅰ型还是Ⅲ型神经元,持续噪声和间断噪声均在探测声强度较低时产生较强的抑制效应,随着探测声强度的升高,抑制效应逐渐降低(P＜0.001);同时,持续噪声和间断噪声之间前掩蔽效应差异亦不复存在(P＞0.05).此外,当掩蔽声由持续噪声换为间断噪声后,部分Ⅰ型神经元掩蔽时相的类型发生转变,其中最主要的转变为由前期抑制转变为均衡抑制(53.85%,7/13).对下丘神经元声反应的时间域以及强度域,持续与间断噪声具有分化性前掩蔽效应,提示噪声前掩蔽并非简单的神经元发放压抑源,某些主动性神经调制机制可能参与了噪声条件下时相声信息的编码过程.
유관은중추신경원순음전엄폐효응적신경표정이진행료대량연구,단시,조성전엄폐우기시간단조성전엄폐효응적신경표정각선유보도.본연구관찰료자유성장조건하,곤명소서하구신경원재지속여간단조성전엄폐조건하대순음탐측성적반응.공기록도96개하구신경원,측량료기중51개신경원재불동성자격조건하적강도-방전솔함수.결과현시,엄폐성강도분포교엄(탐측성역하21 dB지역상19 dB지간).재장근일반적신경원중,간단조성적전엄폐효응비지속조성강(Ⅰ형,45.10%,P＜0.001),단야유소수신경원기간단조성적엄폐효응교지속조성적약(Ⅲ형,17.65%,P＜0.001),부분신경원무현저성차이(Ⅱ형,37.25%,P＞0.05).무론Ⅰ형환시Ⅲ형신경원,지속조성화간단조성균재탐측성강도교저시산생교강적억제효응,수착탐측성강도적승고,억제효응축점강저(P＜0.001);동시,지속조성화간단조성지간전엄폐효응차이역불복존재(P＞0.05).차외,당엄폐성유지속조성환위간단조성후,부분Ⅰ형신경원엄폐시상적류형발생전변,기중최주요적전변위유전기억제전변위균형억제(53.85%,7/13).대하구신경원성반응적시간역이급강도역,지속여간단조성구유분화성전엄폐효응,제시조성전엄폐병비간단적신경원발방압억원,모사주동성신경조제궤제가능삼여료조성조건하시상성신식적편마과정.
Although there has been a growing body of literature showing the neural correlation of forward masking caused by a pure tone masker in the auditory neurons, relative few studies have addressed the description of how the forward masking caused by a noise burst,especially a sequence of noise burst, is transformed into neuronal representation in the central auditory system. Using a noise forward masking paradigm under free field stimuli conditions, this in vivo study was devoted to exploring it in the inferior collicular (IC) neurons of the mouse (Mus musculus KM). A total of 96 IC neurons were recorded. Rate-intensity functions (RIFs) with and without the presentation of masker, sustained noise burst (SNB) or segmental noise burst (SGNB), were measured in 51 neurons. We found that the relative masker intensities were distributed over a wide range between 21 dB below the minimum threshold (MT) and 19 dB above the MT of the corresponding probe tone. The masking effect of the SGNB on firing rate in nearly half of neurons (type Ⅰ, 45.10%) was stronger than that of the SNB (P＜0.001), whereas in a smaller fraction of neurons (type Ⅲ, 17.65%), it was weaker than that of the SNB (P＜0.001). There was no significant difference in masking effect between the SNB and SGNB in type Ⅱ neurons (37.25%, P＞0.05).Irrespective of type Ⅰ or type Ⅲ neurons, the inhibitory effects of both kinds of maskers were all greater at lower probe intensities but decreased significantly with the increase of probe intensity (P＜0.001). Interestingly, as the probe intensity increased, the difference of masking effect between the SNB and SGNB disappeared (P＞0.05). In addition, we observed that temporal masking pattern could be transformed when the masker was changed from the SNB to SGNB. The main type of this transformation was from early-inhibition to proportional-inhibition pattern (53.85%, 7/13). Our data provide the evidence that the inhibitory effects of these two maskers have differential weights over time and intensity domains of the IC neurons responding to a pure tone. This suggests that the forward masking of noise is by no means the source of simply suppression in neuronal firing rate. There might be a few of active neural modulating ways in which the coding of temporal acoustical information can be operated.