The Head-fixed Behaving Rat—Procedures and Pitfalls

This paper describes experimental techniques with head-fixed, operantly conditioned rodents that allow the control of stimulus presentation and tracking of motor output at hitherto unprecedented levels of spatio-temporal precision. Experimental procedures for the surgery and behavioral training are presented. We place particular emphasis on potential pitfalls using these procedures in order to assist investigators who intend to engage in this type of experiment. We argue that head-fixed rodent models, by allowing the combination of methodologies from molecular manipulations, intracellular electrophysiology, and imaging to behavioral measurements, will be instrumental in combining insights into the functional neuronal organization at different levels of observation. Provided viable behavioral methods are implemented, model systems based on rodents will be complementary to current primate models—the latter providing highest comparability with the human brain, while the former offer hugely advanced methodologies on the lower levels of organization, for example, genetic alterations, intracellular electrophysiology, and imaging

The role of kinematic events in whisker-related tactile perception

Rodents use active whisker movements to explore their environment. The physical parameters of vibrissa deflections, which carry the texture information and are used by the tactile system for discrimination, are unknown. Particularly, it remains unclear whether perception relies on parameters such as frequency (e.g., spectral information) and intensity (e.g., mean speed) which need to be integrated over time or whether it has access to instantaneous kinematic parameters (i.e., the details of the trajectory). The search for instantaneous kinematic parameters is motivated by findings from studies on rodent vibrissae biomechanics showing that short-lived kinematic events, abrupt movements called ‘slips’, carry texture information and could therefore be used for tactile perception. Here, I use a novel detection of change paradigm in head-fixed rats, which presents passive vibrissa stimuli in seamless sequence for discrimination. Unlike previous paradigms, this procedure ensures that processes of decision making do not need to rely on memory functions and can, instead, directly tap into sensory signals. In a first attempt, repetitive pulsatile stimuli were employed in a noise free environment to optimally control the parameter space. I 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-unit activity shows that small populations of sensitive neurons provide a transient signal that optimally fits the characteristic of the subject’s perception. However, a realistic scenario involves background noise (e.g. evoked by rubbing across the texture) and kinematic ‘slip’ events, carrying texture information. Therefore, if these events are used for tactile perception, the neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, I presented passive whisker-deflections, consisting of ‘slip-like’ events (waveforms mimicking ‘slips’ occurring with real textures) embedded into background noise. Varying the event shape (ramp or pulse), kinematics (amplitude, velocity, etc.), and the probability of occurrence, I observed that rats could readily detect ‘slip-like’ events of different shapes against a noisy background. Psychophysical curves revealed that larger events improved performance while increased probability of occurrence had barely any effect. These results strongly support the notion that encoding of instantaneous ‘slip’ kinematics dominantly determines whisker-related tactile perception while the computation of time integrated parameters plays a minor role

Open Innovation: Legal Hurdles in the Creation of Contractual Arrangements Governing Idea Competitions?

The phenomenon of Open Innovation has been gaining prominence over the last decade. Idea competitions have been used in a variety of industrial sectors. Nevertheless, the legal issues raised by this topic have not been broadly addressed, yet. These arise from the adverse interests of the actors. The company which organizes an idea competition would usually like to have the opportunity to comprehensively use the solutions, ideas or products submitted by the competition entrants. For the company it is important to obtain all intellectual property rights in the idea, in the product created as a result and, thus, in the rights to be exploited in the future, in particular, patents, utility models, trademarks, copyrights and registered designs as well as other industrial property rights. The participant would like to participate to the greatest extent possible in the success of the submitted solution. This affects, firstly, the question of fair remuneration or further participation in any profits earned as well as, secondly, any personal rights such as being named as inventor or author. The article aims to show the contractual difficulties which have to be addressed tailoring theterms of an idea competition under German law

Vibrotactile Discrimination in the Rat Whisker System is Based on Neuronal Coding of Instantaneous Kinematic Cues

Which physical parameter of vibrissa deflections is extracted by the rodent tactile system for discrimination? Particularly, it remains unclear whether perception has access to instantaneous kinematic parameters (i.e., the details of the trajectory) or relies on temporally integration of the movement trajectory such as frequency (e.g., spec-tral information) and intensity (e.g., mean speed). Here, we use a novel detection of change paradigm in head-fixed rats, which presents pulsatile vibrissa stimuli in seamless sequence for discrimination. This procedure ensures that processes of decision making can directly tap into sensory signals (no memory functions involved). We find that dis-crimination performance based on instantaneous kinematic cues far exceeds the ones provided by frequency and intensity. Neuronal mod-eling 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. A possible impact of this finding on tactile systems of other species is suggested by evidence for instantaneous coding also in primates

Information Coding through Adaptive Gating of Synchronized Thalamic Bursting

It has been posited that the regulation of burst/tonic firing in the thalamus could function as a mechanism for controlling not only how much but what kind of information is conveyed to downstream cortical targets. Yet how this gating mechanism is adaptively modulated on fast timescales by ongoing sensory inputs in rich sensory environments remains unknown. Using single-unit recordings in the rat vibrissa thalamus (VPm), we found that the degree of bottom-up adaptation modulated thalamic burst/tonic firing as well as the synchronization of bursting across the thalamic population along a continuum for which the extremes facilitate detection or discrimination of sensory inputs. Optogenetic control of baseline membrane potential in thalamus further suggests that this regulation may result from an interplay between adaptive changes in thalamic membrane potential and synaptic drive from inputs to thalamus, setting the stage for an intricate control strategy upon which cortical computation is built