Sinclair R J, Pruett J R, Burton H
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Somatosens Mot Res. 1996;13(3-4):287-306. doi: 10.3109/08990229609052584.
Responses of 66 neurons in primary somatosensory cortex (SI) of three anesthetized monkeys (Macaca mulatta) were characterized with grating patterns of 550- to 2900-mm groove width (Gw) and 250-mm ridge width, and/or pairs of 3-mm-wide ridges (bars) spaced 1-20 mm apart. Surfaces were stroked across single fingertips at parametrically varied levels of force (25-150 g) and velocity (25-100 mm/sec). The average firing rates (AFRs) of many cells varied with Gw, but force and velocity altered response functions (e.g., from linear to plateau or inverted). Slowly adapting (SA) cells were more sensitive to force, rapidly adapting (RA) cells to velocity. Force and velocity affected all cells sensitive to Gw, which suggests that response independence (e.g., AFR correlated with Gw but not force or velocity) may require active touch. Discharge intervals of many cells replicated stimulus temporal period. This temporal fidelity in SAs far exceeded examples reported for active touch. However, discharge burst duration and AFR increased with Gw, supporting a neural rate rather than temporal code for roughness. Force and velocity altered the Gw at which some cells fired once in phase to stimulus cycle ("tuning point"). Responses to bar edges suggest cortical replication of peripheral mechanoreceptor sensitivity to skin curvature, leading to this temporal fidelity in some cortical cells. Graded RA responses to Gw without obvious stimulus temporal replication may reflect early stages of integrative processing in supra- and infragranular layers that blur obvious temporal patterning and lead to a rate code correlated with spatial variation and proportional to perceived roughness.
在三只麻醉的猕猴（恒河猴）的初级体感皮层（SI）中，对66个神经元的反应进行了表征，使用的光栅图案的槽宽（Gw）为550至2900毫米，脊宽为250毫米，和/或间隔1至20毫米的成对3毫米宽的脊（条）。在参数变化的力（25至150克）和速度（25至100毫米/秒）水平下，用这些表面划过单个指尖。许多细胞的平均放电率（AFR）随Gw变化，但力和速度改变了反应函数（例如，从线性变为平台型或倒置型）。慢适应（SA）细胞对力更敏感，快适应（RA）细胞对速度更敏感。力和速度影响了所有对Gw敏感的细胞，这表明反应独立性（例如，AFR与Gw相关，但与力或速度无关）可能需要主动触摸。许多细胞的放电间隔复制了刺激的时间周期。SA中的这种时间保真度远远超过了主动触摸的报道示例。然而，放电爆发持续时间和AFR随Gw增加，支持了粗糙度的神经速率编码而非时间编码。力和速度改变了一些细胞在刺激周期中同相放电一次的Gw（“调谐点”）。对条边缘的反应表明皮层复制了外周机械感受器对皮肤曲率的敏感性，导致一些皮层细胞具有这种时间保真度。对Gw的分级RA反应没有明显的刺激时间复制，可能反映了颗粒上层和颗粒下层整合处理的早期阶段，这些阶段模糊了明显的时间模式，并导致与空间变化相关且与感知粗糙度成比例的速率编码。
