Vibrotactile discrimination in the rat whisker system is based on neuronal coding of instantaneous kinematic cues.
Bottom Line: We find that discrimination performance based on instantaneous kinematic cues far exceeds the ones provided by frequency and intensity.Neuronal modeling based on barrel cortex single units shows that small populations of sensitive neurons provide a transient signal that optimally fits the characteristic of the subject's perception.The present study is the first to show that perceptual read-out is superior in situations allowing the subject to base perception on detailed trajectory cues, that is, instantaneous kinematic variables.
Affiliation: Werner Reichardt Center for Integrative Neuroscience, Systems Neuroscience, Hertie Institute for Clinical Brain Research, Department of Cognitive Neurology, Eberhard Karls University, Tübingen, Germany.Show MeSH
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Mentions: In Figure 5A the distribution of PSTHs obtained from the whole sample are shown for 4 different stimuli and catch trial used in Experiment 1b. Median firing rate changes (black) and 25% and 75% percentile levels (gray) are depicted for the 30 multiunits (top) and 24 single units (bottom) recorded in this experiment. The sustained firing rate to S− was subtracted, so that positive/negative firing rates would indicate a higher/lower sustained response to S+ as compared with S−. The median firing rate of multiunits was clearly modulated by the first pulses with amplitude changes down to +2.2°. Inspection of different percentile levels reveals that more than 75% of the multiunits showed an excitatory response to amplitude changes of 7.2° and 3.9°. Owing to very low firing rates, single-unit population activity appeared noisier but generally matched the observation from multiunits. Interestingly, in experiments which kept the pulse kinematics constant but varied the frequency (labeled “+24 Hz”), all recorded neurons showed flat PSTHs varying around zero change in firing rate. This result reveals the near complete absence of neuronal responses to an isolated switch in stimulus frequency.Figure 5.
Affiliation: Werner Reichardt Center for Integrative Neuroscience, Systems Neuroscience, Hertie Institute for Clinical Brain Research, Department of Cognitive Neurology, Eberhard Karls University, Tübingen, Germany.