Abstract
A multi-electrode array (MEA) was implanted in the dorsolateral funiculus of the cervical spinal cord to record descending information during behavior in freely moving rats. Neural signals were characterized in terms of frequency and information content. Frequency analysis revealed components both at the range of local field potentials and multi-unit activity. Coherence between channels decreased steadily with inter-contact distance and frequency suggesting greater spatial selectivity for multi-unit activity compared to local field potentials. Principal component analysis (PCA) extracted multiple channels of neural activity with patterns that correlated to the behavior, indicating multiple dimensionality of the signals. Two different behaviors involving the forelimbs, face cleaning and food reaching, generated neural signals through distinctly different combination of neural channels, which suggested that these two behaviors could readily be differentiated from recordings. This preliminary data demonstrated that descending spinal cord signals recorded with MEAs can be used to extract multiple channels of command control information and potentially be utilized as a means of communication in high level spinal cord injury subjects.
Highlights
Spinal cord injury (SCI) at the cervical level results in quadriplegia with little or no function remaining in the upper limbs
The frequency range below 200 Hz, which is generally classified as Local field potentials (LFPs), demonstrates significant power
Brain-computer interfaces (BCI) based on implantable multielectrode recordings were first investigated in rodents (O’Keefe and Dostrovsky, 1971; Nicolelis et al, 1993, 1995, 1998; Wilson and McNaughton, 1993; Chapin et al, 1999) and later in non-human primates (Baker et al, 1999; Decharms et al, 1999; Wessberg et al, 2000; Serruya et al, 2002; Taylor et al, 2002; Carmena et al, 2003; Nicolelis et al, 2003; Hatsopoulos et al, 2004; Musallam et al, 2004; Lebedev et al, 2005; Santhanam et al, 2006; Jackson and Fetz, 2007)
Summary
Spinal cord injury (SCI) at the cervical level results in quadriplegia with little or no function remaining in the upper limbs. It has been shown that the cervical rubrospinal tract (RST) present in the dorsolateral column contains information required for controlling forelimb movements in rats and other species (Gibson et al, 1985a,b; Daniel et al, 1987; Robinson et al, 1987; Houk, 1991; Jarratt and Hyland, 1999; Jiang et al, 2002; Craven, 2008) In this project, we are recording motor signals from the RST, located in the dorsolateral column, at the cervical C5/C6 level of the rat spinal cord to test if these signals can be used as a means of generating volitional command signals (Prasad and Sahin, 2006a,b, 2009). The multi-unit activities and the LFPs were recorded during skilled
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