Second spatial derivative analysis of cortical surface potentials recorded in cat primary auditory cortex using thin film surface arrays: Comparisons with multi-unit data

James B. Fallon, Sam Irving, Satinderpall S. Pannu, Angela C. Tooker, Andrew K. Wise, Robert K. Shepherd, Dexter R.F. Irvine

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Abstract

Background: Current source density analysis of recordings from penetrating electrode arrays has traditionally been used to examine the layer- specific cortical activation and plastic changes associated with changed afferent input. We report on a related analysis, the second spatial derivative (SSD) of surface local field potentials (LFPs) recorded using custom designed thin-film polyimide substrate arrays. Results: SSD analysis of tone- evoked LFPs generated from the auditory cortex under the recording array demonstrated a stereotypical single local minimum, often flanked by maxima on both the caudal and rostral sides. In contrast, tone-pips at frequencies not represented in the region under the array, but known (on the basis of normal tonotopic organization) to be represented caudal to the recording array, had a more complex pattern of many sources and sinks. Comparison with existing methods: Compared to traditional analysis of LFPs, SSD analysis produced a tonotopic map that was more similar to that obtained with multi-unit recordings in a normal-hearing animal. Additionally, the statistically significant decrease in the number of acoustically responsive cortical locations in partially deafened cats following 6 months of cochlear implant use compared to unstimulated cases observed with multi-unit data (p = 0.04) was also observed with SSD analysis (p = 0.02), but was not apparent using traditional analysis of LFPs (p = 0.6). Conclusions: SSD analysis of surface LFPs from the thin-film array provides a rapid and robust method for examining the spatial distribution of cortical activity with improved spatial resolution compared to more traditional LFP recordings.

Original languageEnglish
Pages (from-to)14-20
Number of pages7
JournalJournal of Neuroscience Methods
Volume267
DOIs
Publication statusPublished - 15 Jul 2016
Externally publishedYes

Keywords

  • Cochlear implant
  • Cortical plasticity
  • Local field potential
  • Neural prosthesis
  • Sensorineural hearing loss

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