FARFAN Fernando Daniel
congresos y reuniones científicas
Electrophysiology of Rat Vibrissal System: Analysis of Multifiber Signals, Texture Discrimination, Digital Processing Techniques and Neural Code
Huerta Grande, Cordoba
Congreso; I Reunión Conjunta de Neurociencias; 2009
Institución organizadora:
Sociedad Argentina de Investigacion en Neurociencias
When rats acquire sensory information by actively moving their vibrissae, a neural code is manifested at different levels of the sensory system. Behavioral studies in tactile discrimination agree in that the rats can distinguish surfaces of different roughness by whisking their vibrissae. It has been demonstrated, recently, that a texture code in peripheral afferent nerve activity of the vibrissal system would exist [1] and that the firing rate would be the encoding mechanism that underlies the texture discrimination in primary somatosensory cortex [2]. In these investigations we characterized some aspects of texture sensing in anesthetized rats during active touch. The multifiber discharge from a deep vibrissal nerve during the sweeps different materials (wood, metal, acrylic, sandpaper) with similar degrees of roughness and different grain size were analyzed. Vibrissal movement was induced with two-branch facial nerve stimulation. We consider the change pressure against the vibrissa as a way to improve the tactile information acquisition. The signals were compared with a reference signal (control), vibrissa sweeping the air. We have also explored the existence of new temporal patterns based on ‘events’ related to texture neural code. Two new methods for afferent activity analysis were proposed: a Time-Frequency analysis and Inter-event Time analysis. RMS values and power pectrum density (PSD) have also been used in the analyses. We also proposed a method based on information theory to quantifying the neural code. As roughness increased, the RMS values also increased in almost all cases, thus suggesting a direct relation. In addition, a better discrimination performance in the retraction phase was observed. PSD analysis showed differences in the frequency components of maximum energy (Fmax) among sweeping situations. The Time-frequency analysis allowed to compare Fmax throughout the time. Differences in protraction and retraction phase were found. Likewise, varying the pressure could represent a behavioral strategy that improves the information acquisition for texture discrimination. Finally, we have demonstrated and quantified for the first time the existence of temporal patterns related to the roughness information by analyzing the multifiber activity (average activity) in one vibrissa innervation. References: [1] BMC Neurosci 7:42, 2006; [2] PLoS Biol 5:e305, 2007