Tian B, Rauschecker J P
Georgetown University Medical Center, Georgetown Institute for Cognitive and Computational Sciences, Washington, DC 20007, USA.
J Neurophysiol. 1998 May;79(5):2629-42. doi: 10.1152/jn.1998.79.5.2629.
Single-neuron activity was recorded from the posterior auditory field (PAF) in the cortex of gas-anesthetized cats. Tone bursts and broadband complex sounds were used for auditory stimulation. Responses to frequency-modulated (FM) sounds, in particular, were studied systematically. Linear FM sweeps were centered around the best frequency (BF) of a neuron and had an excursion large enough to cover its whole frequency tuning range. Rate and direction of change of the FM sweeps were varied. In the majority of PAF neurons (75%) the FM response seemed not to be linear, i.e., their best instantaneous frequency (BIF) varied by more than one octave at different FM rates (FMR). When the difference between BIF and BF at each FMR was used as a measure of linearity, it was within one-third octave only at five or fewer FMR in most PAF neurons (74%). The majority of PAF neurons (70%) preferred moderate FM rates (<200 Hz/ms). Fifty-four percent of all neurons in this area showed band-pass behavior with a clear preference in the middle range of FM rates in at least one direction. Overall, neurons with high-pass behavior in both directions made up only a minor portion (22%) of PAF neurons. When both directions of an FM sweep (low-to-high and high-to-low frequency) were tested, 50% of the neurons were clearly selective for one direction, i.e., the response to one FM direction was at least twice as large as that to the other direction. This selectivity was not necessarily present at the preferred FM rate. In general, FM direction selectivity was equally distributed over FM rates tested. The selectivity of PAF neurons for the rate and direction of FM sounds makes these neurons suitable for the detection and analysis of communication sounds, which often contain FM components with a moderate sweep rate in a particular direction.
在气体麻醉猫的皮层后听觉场（PAF）中记录单神经元活动。使用短纯音和宽带复合音进行听觉刺激。特别系统地研究了对调频（FM）声音的反应。线性FM扫描以神经元的最佳频率（BF）为中心，其偏移量足够大以覆盖其整个频率调谐范围。改变FM扫描的速率和变化方向。在大多数PAF神经元（75%）中，FM反应似乎不是线性的，即它们的最佳瞬时频率（BIF）在不同的FM速率（FMR）下变化超过一个八度。当将每个FMR下BIF与BF之间的差异用作线性度的度量时，在大多数PAF神经元（74%）中，该差异仅在五个或更少的FMR下在三分之一八度以内。大多数PAF神经元（70%）更喜欢中等FM速率（<200 Hz/ms）。该区域所有神经元中有54%表现出带通行为，在至少一个方向上对FM速率的中间范围有明显偏好。总体而言，在两个方向上具有高通行为的神经元仅占PAF神经元的一小部分（22%）。当测试FM扫描的两个方向（低频到高频和高频到低频）时，50%的神经元对一个方向有明显的选择性，即对一个FM方向的反应至少是对另一个方向反应的两倍。这种选择性不一定在首选FM速率时出现。一般来说，FM方向选择性在测试的FM速率上均匀分布。PAF神经元对FM声音的速率和方向的选择性使得这些神经元适合于检测和分析通信声音，通信声音通常包含在特定方向上具有中等扫描速率的FM成分。
