Empirically inspired simulated electro-mechanical model of the rat mystacial follicle-sinus complex

Abstract

In whiskered animals, activity is evoked in the primary sensory afferent cells (trigeminal nerve) by mechanical stimulation of the whiskers. In some cell populations this activity is correlated well with continuous stimulus parameters such as whisker deflection magnitude, but in others it is observed to represent events such as whisker-stimulator contact or detachment. The transduction process is mediated by the mechanics of the whisker shaft and follicle-sinus complex (FSC), and the mechanics and electro-chemistry of mechanoreceptors within the FSC. An understanding of this transduction process and the nature of the primary neural codes generated is crucial for understanding more central sensory processing in the thalamus and cortex. However, the details of the peripheral processing are currently poorly understood. To overcome this deficiency in our knowledge, we constructed a simulated electro-mechanical model of the whisker-FSC-mechanoreceptor system in the rat and tested it against a variety of data drawn from the literature. The agreement was good enough to suggest that the model captures many of the key features of the peripheral whisker system in the rat.

Contact type dependency of texture classification in a whiskered mobile robot

“…Responses to more complex stimuli are much less intuitive and comparable biological data are generally lacking. The results presented here use the model of [23] -the revised model of [27] would give similar values for the simple features used here.…”

“…The first pair of features is inspired by inspection of sampled whisker signals. The other two pairs are inspired by previous neurophysiological [2] and modeling [17], [23] investigations of the rat vibrissal system. In each case we present raw scatter plots of the data classes under the features, and confusion matrices obtained using a standard Gaussian classifier [7].…”

“…In previous work [23], [27] we constructed a biomimetic model of transduction in the whisker follicle. This electromechanical model transforms patterns of mechanical whisker stimulation into their initial encoding as patterns of neural firing in primary afferent neurons (PAs) associated with each whisker follicle.…”

“…The exploration of texture by the vibrissae is an active process which involves sweeping ('whisking') the whiskers across the target surface at a rate of 5-15Hz during typical exploratory behaviour [4]. The brushing of each vibrissa against the target surface induces vibrations in the whisker shaft that are transduced into neural signals by mechanoreceptors in the whisker follicle [23]. The neural encodings of these vibration patterns, formed across the vibrissal array, therefore provide the basis for the texture discrimination capabilities shown by the rat [1], [16].…”

“…One previous study [17] has taken a similar approach in which frequency-based features inspired by the analysis of activity in whisker ("barrel") sensory cortex were used to successfully classify signals obtained from an actuated 80mm metal whisker moved against textured surfaces from a known fixed starting position. The features identified by [17], along with others inspired by our own investigations of coding in the vibrissal primary afferent neurons [23], will be evaluated below for their usefulness in discriminating texture in a robotic whisker context. The performance of the above methods will also be compared with a neural network classifier.…”