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Shuttle-box avoidance learning is well-established in behavioral neuroscience. This protocol describes how shuttle-box learning in rodents can be combined with site-specific electrical intracortical microstimulation (ICMS) and simultaneous chronical in vivo recordings as a tool to study multiple aspects of learning and perception.
Shuttle-box avoidance learning is a well-established method in behavioral neuroscience and experimental setups were traditionally custom-made; the necessary equipment is now available by several commercial companies. This protocol provides a detailed description of a two-way shuttle-box avoidance learning paradigm in rodents (here Mongolian gerbils; Meriones unguiculatus) in combination with site-specific electrical intracortical microstimulation (ICMS) and simultaneous chronical electrophysiological in vivo recordings. The detailed protocol is applicable to study multiple aspects of learning behavior and perception in different rodent species.
Site-specific ICMS of auditory cortical circuits as conditioned stimuli here is used as a tool to test the perceptual relevance of specific afferent, efferent and intracortical connections. Distinct activation patterns can be evoked by using different stimulation electrode arrays for local, layer-dependent ICMS or distant ICMS sites. Utilizing behavioral signal detection analysis it can be determined which stimulation strategy is most effective for eliciting a behaviorally detectable and salient signal. Further, parallel multichannel-recordings using different electrode designs (surface electrodes, depth electrodes, etc.) allow for investigating neuronal observables over the time course of such learning processes. It will be discussed how changes of the behavioral design can increase the cognitive complexity (e.g. detection, discrimination, reversal learning).
A fundamental aim of behavioral neuroscience is to establish specific links between neuronal structural and functional properties, learning, and perception. Neural activity associated with perception and learning can be studied by electrophysiological recording of action potentials and local field potentials in various brain structures at multiple sites. Whereas electrophysiological recordings provide correlative associations between neural activity and behavior, direct electrical intracortical microstimulation (ICMS) for over a century has been the most direct method for testing causal relationships of excited populations of neurons and their behavioral and perceptual effects1–3. Many studies have demonstrated that animals are able to make use of various spatial and temporal properties of electrical stimuli in perceptual tasks depending on the stimulation site within for instance retinotopic4, tonotopic5, or somatotopic6 regions in the cortex. Propagation of electrically evoked activity in the cortex is mainly determined by the layout of axonal fibers and their distributed synaptic connectivity2 that, in cortex, is clearly layer-dependent7. The resultant polysynaptic activation evoked by ICMS is henceforth much more wide-spread than direct effects of the electrical field2,8,9. This explains why thresholds of perceptual effects elicited by intracortical microstimulation can be strongly layer-dependent8,10,11 and site-dependent9. A recent study demonstrated in detail that stimulation of upper layers yielded more wide-spread activation of corticocortical circuits in mainly supragranular layers, while stimulation of deeper layers of cortex result in a focal, recurrent corticoefferent intracolumnar activation. Parallel behavioral experiments revealed that the latter has much lower perceptual detection thresholds8. Therefore, the advantage of site-specific ICMS as conditioned stimuli was exploited in combination with electrophysiological recordings to causally relate specific cortical circuit activations8 to behavioral measures of learning and perception in the shuttle-box.
The two-way shuttle-box paradigm is a well-established laboratory apparatus to study avoidance learning12. A shuttle-box consists of 2 compartments separated by a hurdle or doorway. A conditioned stimulus (CS) that is represented by a suitable signal like a light or sound, is contingently followed by an aversive unconditioned stimulus (US), as for instance a foot shock over a metal grid floor. Subjects can learn to avoid the US by shuttling from one shuttle-box compartment to the other in response to the CS. Shuttle-box learning involves a sequence of distinguishable learning phases13,14: First, subjects learn to predict the US from the CS by classical conditioning and to escape from the US by instrumental conditioning, as the US is terminated upon shuttling. In a next phase, subjects learn to avoid the US altogether by shuttling in response to the CS before US onset (avoidance reaction). Generally, shuttle-box learning involves classical conditioning, instrumental conditioning, as well as goal-directed behavior depending on learning phase14.
The shuttle-box procedure can be set up easily and generally produces robust behavior after a few daily training sessions15–17. In addition to simple avoidance conditioning (detection), the shuttle-box can be further used to study stimulus discrimination by employing go/nogo paradigms. Here, animals are trained to avoid the US by a conditioned response (CR) (go behavior; shuttle into opposite compartment) in response to a go-stimulus (CS+) and by nogo behavior (stay in the current compartment; no CR) in response to a nogo-stimulus (CS-). Parallel microstimulation and recording of neural activity with high-density multielectrode arrays allow to study the physiological mechanisms underlying successful learning. Several technical details that are fundamental for the successful combinations of shuttle-box training, ICMS and parallel electrophysiology, will be discussed.
All experiments presented in this work were conducted in agreement with the ethical standards defined by the German law for the protection of experimental animals. Experiments were approved by the ethics committee of the state of Saxony-Anhalt.
1. Custom-made Multichannel Electrode Arrays for Microstimulation and Recording
2. Surgical Implantation of Arrays into Auditory Cortex in Anaesthetized Mongolian Herbils for Chronic Usage
3. Two-way Shuttle-box Designs Using ICMS as Conditioned Stimulus
4. In Vivo Electrophysiological Techniques in Learning Animals
5. Histological Analysis of Electrode Positions
This section illustrates a representative example of shuttle-box learning in a Mongolian gerbil. The subject was trained to discriminate the ICMS site between two stimulation electrodes implanted 700 µm apart from each other in auditory cortex (Figures 1 and 2). Stimulation arrays can be customized in different spatial designs (Figure 1). Here, discrimination of the two ICMS sites was learned within 3 training sessions with presentation of 30 CS+ and CS- each (Figure 3A-C
This protocol describes a method of simultaneous site-specific ICMS and multi-channel electrophysiological recordings in a learning animal by using a two-way aversive foot-shock controlled shuttle-box system. The protocol emphasizes technical key concepts for such combination and points out the importance of grounding the animal only via its common ground electrode, leaving the gridfloor at a floating voltage. Here, auditory shuttle-box learning was applied to Mongolian gerbils as learning-related plastic reorganizations...
The authors have nothing to disclose.
The work was supported by grants from the Deustche Forschungsgemeinschaft DFG and the Leibniz-Institute for Neurobiology. We thank Maria-Marina Zempeltzi and Kathrin Ohl for technical assistance.
Name | Company | Catalog Number | Comments |
Teflon-insulated stainless steel wire | California Fine Wire | diam. 50µm w/ isolation | |
Pin connector system | Molex Holding GmbH | 510470200 | 1.25 mm pitch PicoBlade |
TEM grid Quantifoil | Science Services | EQ225-N27 | |
Dental acrylic Paladur | Heraeus Kulzer | 64707938 | |
Hand-held drill OmniDrill35 | WPI | 503599 | |
Ketamine 500mg/10ml | Ratiopharm GmbH | 7538837 | |
Rompun 2%, 25ml | Bayer Vital GmbH | 5066.0 | |
Sodium-Chloride 0.9%, 10ml | B.Braun AG | PRID00000772 | |
Lubricant KY-Jelly | Johnson & Johnson | ||
Shuttle-box E10-E15 | Coulbourn Instruments | H10-11M-SC | |
Stimulus generator MCS STG 2000 | Multichannel Systems | ||
Plexon Headstage cable 32V-G20 | Plexon Inc. | HSC/32v-G20 | |
Plexon Headstage 32V-G20 | Plexon Inc. | HST/32v-G20 | |
PBX preamplifier 32 channels | Plexon Inc. | 32PBX box | |
Multichannel Acquisition System | Plexon Inc. | MAP 32/HLK2 | |
Cryostate CM3050 S | Leica Microsystems GmbH | ||
Signal processing Card Ni-Daq | National Instruments | ||
Lab StandardTM Stereotaxic Instruments | Stoelting Co. | ||
Audio attenator g.pah | g.pah Guger technologies | ||
Cresyl violet acetate | Roth GmbH | 7651.2 | |
Roticlear | Roth GmbH | A538.1 | |
Sodium acetate trihydrate | Roth GmbH | 6779.1 | |
Potassium hexacyanoferrat(II) trihydrate | Roth GmbH | 7974.2 | |
Di-sodium hydrogen phospahte dihydrate | Merck | 1,065,801,000 | |
ICM Impedance Conditioning Module | FHC | 55-70-0 | |
Animal Temperarture Controler | World Precision Instruments | ATC2000 |
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