Roberts Roberta D, Loomes Aldrin R, Kwok Hoi Fei, Wing Alan M, Allen Harriet A
Sensory Motor Neuroscience Laboratory, School of Psychology, University of Birmingham, Birmingham, United Kingdom.
School of Psychology, University of Nottingham, University Park, Nottingham, United Kingdom.
Front Neurosci. 2023 Nov 23;17:1282566. doi: 10.3389/fnins.2023.1282566. eCollection 2023.
Psychophysical studies suggest texture perception is mediated by spatial and vibration codes (duplex theory). Vibration coding, driven by relative motion between digit and stimulus, is involved in the perception of very fine gratings whereas coarse texture perception depends more on spatial coding, which does not require relative motion.
We examined cortical activation, using functional Magnetic Resonance Imaging associated with fine and coarse tactile spatial gratings applied by sliding or touching (sliding vs. static contact) on the index finger pad.
We found regions, contralateral to the stimulated digit, in BA1 in S1, OP1, OP3, and OP4 in S2, and in auditory cortex, which were significantly more activated by sliding gratings but did not find this pattern in visual cortex. Regions in brain areas activated by vibrotactile stimuli (including auditory cortex) were also modulated by whether or not the gratings moved. In a control study we showed that this contrast persisted when the salience of the static condition was increased by using a double touch.
These findings suggest that vibration from sliding touch invokes multisensory cortical mechanisms in tactile processing of roughness. However, we did not find evidence of a separate visual region activated by static touch nor was there a dissociation between cortical response to fine vs. coarse gratings as might have been expected from duplex theory.
心理物理学研究表明，纹理感知由空间编码和振动编码介导（双重理论）。由手指与刺激物之间的相对运动驱动的振动编码参与了极细光栅的感知，而粗糙纹理感知更多地依赖于空间编码，空间编码不需要相对运动。
我们使用功能磁共振成像技术，研究与在食指垫上通过滑动或触摸（滑动与静态接触）施加的精细和粗糙触觉空间光栅相关的皮层激活情况。
我们发现，在初级体感皮层（S1）的BA1区、次级体感皮层（S2）的OP1、OP3和OP4区以及听觉皮层中，受刺激手指对侧的区域，对滑动光栅的激活明显更强，但在视觉皮层中未发现这种模式。由振动触觉刺激激活的脑区（包括听觉皮层）也受到光栅是否移动的调节。在一项对照研究中，我们发现，当通过双次触摸增加静态条件的显著性时，这种对比仍然存在。
这些发现表明，滑动触摸产生的振动在粗糙度的触觉处理中引发了多感觉皮层机制。然而，我们没有发现由静态触摸激活的单独视觉区域的证据，也没有发现如双重理论所预期的那样，皮层对精细与粗糙光栅的反应存在分离。
