Chronic Recording of Extracellular Neuronal Activity in Behaving Animals

Ronald Szymusiak1, Douglas Nitz2

1 University of California, Los Angeles, California, 2 Neurosciences Institute, La Jolla, California
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 6.16
DOI:  10.1002/0471142301.ns0616s21
Online Posting Date:  February, 2003
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Abstract

Two methods for recording extracellular neuronal activity in unanesthetized, unrestrained rats are described in this unit. Both use chronically‐implanted bundles of fine microwires to record electrophysiological activity. One method provides recordings of single and/or multiple unit activity from individual wires in a bundle (monotrode). Discrimination of individual neuronal potentials is based on action potential amplitude, or on a combination of action potential amplitude and shape. The second method uses a 2‐ to 4‐microwire array (stereotrode‐tetrode) to yield multiple unit recordings. Discrimination of individual neuronal potentials is based on action potential shapes and the relative amplitude of action potentials recorded simultaneously on the different wires in the array. These methods can provide stable, long‐term recording of neuronal activity during a variety of behavioral paradigms.

     
 
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Table of Contents

  • Strategic Planning
  • Basic Protocol 1: Surgical Implantation of Microwire Bundles and Data Acquisition in Rats
  • Support Protocol 1: Preparation of Microwire/Microdrives
  • Support Protocol 2: Analyses for Single‐ and Multiple‐Unit Recording Data
  • Basic Protocol 2: Surgical Implantation of Stereotrodes/Tetrodes and Data Acquisition in Rats
  • Support Protocol 3: Fabrication of Stereotrodes/Tetrodes
  • Support Protocol 4: Single‐Unit Wave Form Discrimination or “Cluster Cutting” for Stereotrode/Tetrode Recordings
  • Commentary
  • Figures
     
 
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Materials

Basic Protocol 1: Surgical Implantation of Microwire Bundles and Data Acquisition in Rats

  Materials
  • Rats (Sprague‐Dauley, male or female, 250 to 350 g; Charles River)
  • Anesthetic (ketamine/xylazine; 80:10 mg/kg)
  • Alcohol swabs
  • Dental acrylic and solvent (methylmethacrylate; Co‐Oral‐Ite Dental)
  • Miniature electrical connector with 4 to 7 contacts
  • Solder (“44” Kester Solder)
  • Rat stereotaxic frame
  • Scalpel
  • Microdrives (see protocol 2)
  • Small machine screws for anchoring dental acrylic to skull (00 × ⅛‐in.; Morris Precision Screws & Parts)
  • Moto‐tool and grinding disk (Dremel)
  • Disposable 24‐G syringe needle
  • Stainless steel cannula (24‐G and 21‐G; ThinWall)
  • Microwires (see protocol 2)
  • Polyethylene tubing (0.023‐in. i.d. and 0.038‐in o.d.)
  • 3‐ml syringes
  • Low‐noise wire for recording cables (Filotex; Etude 22595, Alcatel)
  • Low‐noise electrical switching device, any type (e.g., rotary, sliding, patch panel)
  • Electrically shielded recording/observation chamber (grounded aluminum or copper screen) of sufficient size to permit expression of the behaviors under investigation. Animals should be able to be continuously observed during recording, either through a window in the chamber or via video camera.
  • Low‐noise electrical commutator or slip ring (optional)
  • AC‐coupled differential amplifiers (e.g., model 1700; A.M. Systems)
  • Oscilloscope (digital or analog; storage oscilloscope is optimal)
  • Computer‐based data acquisition/analysis system, including A/D board and software (e.g., CED 1401 Neurophysiological Interface and Spike 2 software; Cambridge Electronic Design)
  • Window discriminator (optional; e.g., model S8; S‐A Instruments)

Support Protocol 1: Preparation of Microwire/Microdrives

  Materials
  • Enamel glue (e.g., Epoxylite, Epoxylite Corp.)
  • Chemical wire stripper (e.g., Strip‐X; G.C. Electronics)
  • Alcohol swab
  • Normal saline
  • Nichrome microwire (19‐ to 32‐µm uninsulated diameter), double formvar‐insulated, stress relieved, and wound on a large spool to minimize curling (California Fine Wire)
  • Wooden jig (Fig. ), made in‐house
  • 32‐ to 64‐µm support nichrome wire
  • 100°C oven
  • Jeweler's forceps
  • Watch glass
  • Stainless steel soldering flux (e.g., EutecSol Flux; Eutectic Corp.) and rosin core solder
  • Cotton swab
  • Dissecting microscope
  • Fine surgical scissors
  • Impedance meter (e.g., Model BL‐2000; Winston Electronics)
  • 21‐G and 24‐G thin‐wall stainless steel tubing
  • 24‐G needles
  • Moto‐tool with a grinding disk
  • Machine screws, washers, and nuts (all sizes 0 to 80) and a compression spring (Small Parts)

Support Protocol 2: Analyses for Single‐ and Multiple‐Unit Recording Data

  Materials
  • Rat (adult, 250 to 350 g)
  • 0.9% saline, sterile
  • 0.9% solution of agarose gel (melting point 38°C), kept in a 42°C water bath
  • Dental cement
  • Microdrive (Kopf Instruments or Advanced Machining and Tooling)
  • Stereotrodes or tetrodes (see protocol 5)
  • Stereotaxic manipulator (Kopf Instruments)
  • Surgical instruments
  • 27‐ and 21‐G needles and syringe
  • Anchor screws (00 × ⅛‐in.; Morris Precision Screws and Parts)
  • Miniature electrical connector with sufficient contacts to accommodate the number of wires to be used (Omnetics)
  • Additional reagents and equipment for general surgical procedures (see protocol 1)

Basic Protocol 2: Surgical Implantation of Stereotrodes/Tetrodes and Data Acquisition in Rats

  Materials
  • Glue or tape
  • Epoxy
  • Gold‐plating solution (Gold NC, Sifco)
  • Round L‐shaped bar, ∼5 mm in diameter with 8‐in. (∼20‐cm) sides
  • Magnetic stir plate
  • Small iron‐containing bar, 3 mm × 8 cm (a size 30 drill bit works well)
  • Flat‐lipped bulldog clip
  • Nichrome or tungsten wire insulated with polyimide: 25‐µm (California Fine Wire) for stereotrodes or 12‐µm (Kanthal H.P. Reid) for tetrodes
  • Heat gun with back‐reflecting attachment (Steinel)
  • Tungsten‐carbide scissors (Fine Science Tools)
  • Solder
  • Microdrive
  • Hollow plastic cylinder, 1 cm diameter × 5 cm long
  • Stainless steel wire
  • Stereotaxic apparatus
  • Stimulus isolation unit (World Precision Instruments)
  • Impedance meter
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Figures

Videos

Literature Cited

Literature Cited
   Alam, M.N., McGinty, D., and Szymusiak, R. 1995. Neuronal discharge of preoptic/anterior hypothalamic thermosensitive neurons: Relation to non‐REM sleep. Am. J. Physiol. 38:1240‐1249.
   Alam, M.N., Szymusiak, R., Gong, H., King, J., and McGinty, D. 1999. Adenosine modulation of rat basal forebrain neurons during sleep and waking: Neuronal recording with microdialysis. J. Physiol. 521:679‐690.
   Aston‐Jones, G. and Bloom, F.E. 1981. Activity of norepinepherine‐containing locus coeruleus neurons in behaving rats anticipates fluctuations in the sleep‐waking cycle. J. Neurosci 1:876‐886.
   Eichenbaum, H. and Davis, J.L. 1998. Neuronal Ensembles: Strategies for Recording and Decoding. John Wiley & Sons, New York.
   Guzman‐Marin, R., Alam, M.N., Szymusiak, R., Drucker‐Colin, R., Gong, H., and McGinty, D. 2000. Discharge modulation of rat dorsal raphe neurons during sleep and waking: Effects of preoptic/basal forebrain warming. Brain Res. 875:23‐34.
   Jacobs, B.L. 1985. Overview of the activity of brain monoaminergic neurons across the sleep‐wake cycle. In Sleep: Neurotransmitters and Neuromodulators (A. Wauquier, ed.) pp. 1‐14. Raven Press, New York.
   Knierim, J., Kudrimoti, H., and McNaughton, B.L. 1998. Interactions between idiothetic cues and external landmarks in the control of place cells and head direction cells. J. Neurophysiol. 80:425‐446.
   Lemon, R. 1984. Methods for neuronal recording in conscious animals. In IBRO Handbook Series: Methods in the Neurosciences. John Wiley & Sons, Chichester, U.K.
   McCarley, R.W. and Hobson, J.A. 1971. Single neuron activity in cat gigantocellular tegmental field: Selectivity of discharge in desynchronized sleep. Science 174:1250‐1252.
   McGinty, D. and Siegel, J.M. 1992. Brain neuronal unit discharge in freely moving animals: Methods and application in the study of sleep mechanisms. In Progress in Psychobiology and Physiological Psychology (A.N. Epstein and A.R. Morrison, eds.) pp. 85‐139. Academic Press, San Diego.
   McGinty, D. and Szymusiak, R. 1988. Neuronal unit activity patterns in behaving animals: Brainstem and limbic system. Ann.Rev. Psychol. 39:135‐168.
   McGinty, D.J. and Harper, R.M. 1976. Dorsal raphe neurons: Depression of firing during sleep in cats. Brain Res 101:569‐575.
   McHugh, T., Blum, K., Tsien, J., Tonegawa, S., and Wilson, M. 1996. Impaired hippocampal representation of space in CA1‐specific NMDAR‐1 knockout mice. Cell 87:1339‐1349.
   McNaughton, B.L., O'Keefe, J., and Barnes, C.A. 1983. The stereotrode: A new technique for simultaneous isolation of several single units in the central nervous system from multiple unit records. J. Neurosci. Methods 8:391‐397.
   Mehta, M., Barnes, C.A., and McNaughton, B.L. 1997. Experience‐dependent asymmetric expansion of hippocampal place fields . Proc. Natl. Acad. Sci. U.S.A. 94:8918‐8921.
   Nitz, D.A. and McNaughton, B.L. 1999. Hippocampal EEG and unit activity responses to modulation of serotonergic median raphe neurons in freely behaving rat. Learning and Memory 6:153‐167.
   Poe, G., Nitz, D.A., McNaughton, B.L., and Barnes, C.A. 2000. Experience‐dependent phase reversal of hippocampal neuron firing during REM sleep. Brain Res. 855:176‐180.
   Quirk, M.C. and Wilson, M.A. 1999. Interaction between spike waveform classification and temporal sequence detection. J. Neurosci. Methods 94:41‐52.
   Rieke, F., Warland, D., and Bialek, W. 1999. Spikes: Exploring the Neural Code. MIT Press, Cambridge, Mass.
   Sakai, K. 1980. Some anatomical and physiological properties of ponto‐mesencephalic tegmental neurons with special reference to the PGO waves and postural atonia during paradoxical sleep in the cat. In The Reticular Formation Revisited (J.A. Hobson and M.A. Brazier, eds.) pp. 427‐447. Raven Press, New York.
   Siegel, J.M. and McGinty, D.J. 1977. Pontine reticular formation neurons: Relationship of discharge to motor activity. Science 196:678‐680.
   Steininger, T.L., Alam, M.N., Gong, H., Szymusiak, R., and McGinty, D. 1999. Sleep‐waking discharge of neurons in the posterior lateral hypothalamus of the albino rat. Brain Res. 840:138‐147.
   Szymusiak, R. and McGinty, D. 1986. Sleep‐related neuronal discharge in the basal forebrain of cats. Brain Res. 370:82‐92.
   Szymusiak, R. and McGinty, D. 1989. Sleep‐waking discharge of basal forebrain projection neurons in cats. Brain Res. Bull. 22:423‐430.
   Szymusiak, R., Iriye, T., and McGinty, D. 1989. Sleep‐waking discharge of neurons in the posterior lateral hypothalamic area of cats . Brain Res. Bull 23:111‐120.
   Szymusiak, R., Alam, M.N., Steininger, T.L., and McGinty, D. 1998. Sleep‐waking discharge patterns of ventrolateral preoptic/anterior hypothalamic neurons in rats. Brain. Res. 803:178‐188.
   Thakkar, M., Strecker, R.E., and McCarley, R.W. 1998. Behavioral state control through differential serotonergic inhibition in the mesopontine cholinergic nuclei: A simultaneous unit recording and microdialysis study. J. Neurosci. 18:5490‐5497.
   Vanni‐Mercier, G., Sakai, K., and Jouvet, M. 1984. Neurones specifiques de l'eveil dans l'hypothalamus posterieur du chat. C.R. Acad. Sci. Paris 298:195‐200.
   Wilson, M. and McNaughton, B.L. 1994. Reactivation of hippocampal ensemble memories during sleep. Science 265:676‐679.
Key References
   Eichenbaum and Davis, 1998. See above.
  A good review of different spike data analysis methods. Also, provides good descriptions of unit recording methods as applied in different laboratories.
   McNaughton, 1983. See above.
  The first stereotrode paper.
   Rieke, et al. 1999. See above.
  A good review of different spike data analysis methods.
   Wilson, M. and McNaughton, B.L. 2000. Dynamics of hippocampal ensemble code for space. Science 261:993‐994.
  The first tetrode recording paper.
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