Laminar Characterization of Spiking Activity in the Rat Motor Cortex

Abstract

The neocortex is a six-layered tissue consisting of different cell types. How does unit activity in the different layers of the motor cortex relate to movement? Does implantation in a particular layer improve direction decoding ability for a neuroprosthetic device? We simultaneously recorded unit activity in different layers of the rat motor cortex using chronic multi-site silicon electrodes. We used a combination of histology and electrophysiological signatures of Local Field Potentials (LFPs) to accurately localize the electrode sites in the different layers of the cortex. We analyzed 142 units from two animals and found that 40 units (28%) in Layers II to V showed significant modulation with respect to movement. Of these units that showed significant modulation, 9/20 (45%) of units in Layers II/III encoded directional information as compared to 15/19 (79%) of the units in Layers IV/V. These preliminary results suggest that units in Layers IV/V relatively contain more directional information than other layers of the cortex.

Tuning shifts of the auditory system by corticocortical and corticofugal projections and conditioning

“…Electric stimulation of the nucleus basalis augments the development of the cortical and collicular BF shifts evoked by the focal electric stimulation of AI or by tone burst stimulation (Ma and Suga 2003). It also evokes the large long-lasting cortical BF shift when it is delivered together with tone burst stimulation (in guinea pigs, Bakin and Weinberger 1996; Bjordahl et al 1998; Kilgard and Merzenich 1998; in big brown bats, Ma and Suga 2003; in the house mouse, Yan and Zhang 2005; Zhang et al 2005; Sarter et al 2006: Parikh et al 2007). ACh released in AI by the nucleus basalis apparently augments the cortical BF shift and consequently the collicular BF shift evoked by both the corticofugal feedback and ACh released in the ICc.…”

Chronic stability of local field potentials from standard and modified Blackrock microelectrode arrays implanted in the rat motor cortex

“…Future studies will focus on using probes of varying material composition and geometry to investigate their effects on recording and decoding stability. While conventional UEAs are the gold standard in non-human primate studies, evidence suggests there may be laminar differences in movement-encoding spike and LFP activity [26,50,[52][53][54], necessitating the exploration of alternative devices and strategies because standard UEAs are restricted to a single recording depth per shank on multi-shank arrays. Further investigating the cortical depth of recorded activity and how we optimize LFP and SUA neuronal inputs for neuroprosthetic control will provide invaluable insight towards achieving stable, chronic, and accurate motor decoding.…”