Combined Shuttle-Box Training with Electrophysiological Cortex Recording and Stimulation as a Tool to Study Perception and Learning

Summary

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.

Abstract

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).

Introduction

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 behavio....

Protocol

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

1. Custom-made microstimulation array
   1. For delivering ICMS, prepare stimulation electrodes in the desired spatial design (here lateral array of 2 channels) using 3-cm long Teflon-insulated stainless steel wires (Ø with isolation = 50 µm). See Figure 2.
   2. Crimp one en....

Results

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

Discussion

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.......

Materials

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