In vivo visualization of single-unit recording sites using MRI-detectable elgiloy deposit marking

Kenji W. Koyano, Akinori Machino, Masaki Takeda, Teppei Matsui, Ryoko Fujimichi, Yohei Ohashi, Yasushi Miyashita

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

Precise localization of single-neuron activity has elucidated functional architectures of the primate cerebral cortex, related to vertically stacked layers and horizontally aligned columns. The traditional "gold standard" method for localizing recorded neuron is histological examination of electrolytic lesion marks at recording sites. Although this method can localize recorded neurons with fine neuroanatomy, the necessity for postmortem analysis prohibits its use in long-term chronic experiments. To localize recorded single-neuron positions in vivo, we introduced MRI-detectable elgiloy deposit marks, which can be created by electrolysis of an elgiloy microelectrode tip and visualized on highly contrasted magnetic resonance (MR) images. Histological analysis validated that the deposit mark centers could be localized relative to neuroanatomy in vivo with single-voxel accuracy, at an in-plane resolution of 200 μm. To demonstrate practical applications of the technique, we recorded single-neuron activity from a monkey performing a cognitive task and localized it in vivo using deposit marks (deposition: 2 μA for 3 min; scanning: fast-spin-echo sequence with 0.15 × 0.15 × 0.8 mm3 resolution, 120/4,500 ms of echo-time/repetition-time and 8 echo-train-length), as is usually performed with conventional postmortem methods using electrolytic lesion marks. Two localization procedures were demonstrated: 1) deposit marks within a microelectrode track were used to reconstruct a dozen recorded neuron positions along the track directly on MR images; 2) combination with X-ray imaging allowed estimation of hundreds of neuron positions on MR images. This new in vivo method is feasible for chronic experiments with nonhuman primates, enabling analysis of the functional architecture of the cerebral cortex underlying cognitive processes.

Original languageEnglish
Pages (from-to)1380-1392
Number of pages13
JournalJournal of neurophysiology
Volume105
Issue number3
DOIs
Publication statusPublished - Mar 2011
Externally publishedYes

Keywords

  • Deposit marks
  • Monkey

ASJC Scopus subject areas

  • General Neuroscience
  • Physiology

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