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7 platinum/tungsten cores, quarz insulated for TREC microdrives

The Thomas multicore microelectrodes (heptodes and tetrodes) were designed by Heribert Reitboeck and Uwe Thomas in 1987 in the Reitboeck lab at the University of Marburg, Germany. The Thomas heptode is a fiber microelectrode with an outer diameter of 100µm and 7 individual metal cores insulated from each other by quartz glass. Thomas heptodes are very well suited for single unit isolation from a multi-unit-recording. A major problem in extracellular microelectrode recording from cell-dense regions of the brain is the separation of spikes originated from different neurons. The stereotrode method, first described by McNaughton and others [1] is most effective for this purpose. It was reported by Doerr & Schanze [2] that there is a significant improvement of spike sorting performance when using heptodes rather than tetrodes. 

The Thomas heptodes are available with two different electrode contact arrangements at the tip. The standard heptode and the 3D-heptode (see pictures on the right side)

Key features:

  • Material: quartz glass insulated platinum or platinum/tungsten
  • Unique manufacturing technique offers high reproducibility of tip geometry
  • Tip geometry: highly centered metal core
  • Signal quality: very good signal to noise ratio
  • Quartz glass offers better electrical characteristics as borosolicate glass

3D-Heptode design supported by grant numbers EP140101 and DLEP14365 by:

based on the decision of the German Bundestag

Core conductor material: platinum (95%), tungsten (5%)
Insulation material: quartz glass
Tip shape: (D) only ground, Impedance 1 - 2 MΩ
Connectors: Samtec socket (1136EFL)


[7] Doerr, C. & Schnaze, T. (2015). Are Heptodes better than Tetrodes for spike sorting? ScienceDirect; IFAC-PapersOnLine; Volume 48, Issue 20, 2015, Pages 94-99

[6] Kaneko, H.; Suzuki, S. S.; Okada, J.; Akamatsu, M. Classifying neuronal spikes from multiunit recording by using amultisite electrode. 18th Annual International Conference of the IEEE. Engineering in Medicine and Biology Society, 1996.Bridging Disciplines for Biomedicine.Proceedings of the 18th Annual International Conference of the IEEE 4, 1500-1501. 1996.

[5] Tamura, H.; Kaneko, H.; Kawasaki K.; Fujita, I. Presumed Inhibitory Neurons in the Macaque Inferior Temporal Cortex: Visual Response Properties and Functional Interactions With Adjacent NeuronsJ Neurophysiol 2004, 91, 2782-2796.

[4] Tamura, H.; Kaneko, H.; Fujita, I. Quantitative Analysis of Functional Clustering of Neurons in the Macaque Inferior Temporal Cortex. Neuroscience Research 2005, 52, 311-322.

[3] Kaneko, H.; Tamura, H.; Kawashima, T.; Suzuki, S. S.; Fujita, I. Efficient Signal Processing of Multineuronal Activities for Neural Interface and ProsthesisMethods Inf Med 2007, 46, 147-150.

[2] Doerr, Ch.; Schanze, T. Are Heptodes better than Tetrodes for Spike Sorting?  9th IFAC Symposium on Biological and Medical Systems BMS 2015 – Berlin, Germany, 31 August-2 September 2015. IFAC-PapersOnLine 48[issue 20], 94-99. 2016.

[1] McNaughton B.L., O´Keefe J., Barnes C.A. The stereotrode: a new technique for simultaneous isolation of several single units in the central nerveous system from multiple unit records Journal of Neuroscience Methods, Vol. 8, pp. 391-397, 1983

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