Large-scale Recording of Neurons by Movable Silicon Probes in Behaving Rodents

Abstract

A major challenge in neuroscience is linking behavior to the collective activity of neural assemblies. Understanding of input-output relationships of neurons and circuits requires methods with the spatial selectivity and temporal resolution appropriate for mechanistic analysis of neural ensembles in the behaving animal, i.e. recording of representatively large samples of isolated single neurons. Ensemble monitoring of neuronal activity has progressed remarkably in the past decade in both small and large-brained animals, including human subjects 1-11 . Multiple-site recording with silicon-based devices are particularly effective because of their scalability, small volume and geometric design.

Large-scale, high-density (up to 512 channels) recording of local circuits in behaving animals

“…The experimental protocol was in agreement with the European Communities Council Directive of November 24, 1986 (86/609/EEC) and the National Institutes of Health Guide for the Care and Use of Laboratory Animals. Five male Long-Evans rats (400 -640 g; 3-10 mo old) were implanted with high-density, 256-site silicon probes under isoflurane anesthesia as described earlier (Vandecasteele et al 2012). The probes and the polyimide interconnect cable were manufactured by NeuroNexus (http://www.neuronexus.com).…”

“…In contrast to the blunt tetrode, which often tears intracortical blood vessels during penetration, the tapered profile of the silicon probe shanks allows it to be moved up and down in the brain with continued yield of units. The probe is connected to a microdrive so that the probe sites can be advanced to the vicinity of the desired neurons (Vandecasteele et al 2012;Fig. 2).…”

“…Whereas silicon probe technology is poised to offer everlarger site numbers and smaller volume probes (Du et al 2009(Du et al , 2011, significant improvements and miniaturization are needed at the level of headstage interconnects, signal multiplexing, ultraflexible connection between the animal and the recording equipment, and signal processing (Du et al 2011;Szuts et al 2011;Vandecasteele et al 2012). One critical aspect of miniaturization is the deployment of signal multiplexers.…”

Investigation of the hippocampal information processing in freely moving rats

“…Several additional screws were drilled into the skull and covered with dental cement to strengthen the implant. Finally, a copper mesh was attached to the skull with dental cement and connected to the ground screw to act as a Faraday cage preventing the contamination of the recordings by environmental electric noise (see more details in Vandecasteele et al, 2012). After recovery, the probe was moved gradually in 70 to 150 µm steps per day until the desired position is reached.…”

“…intersite distance) electrodes (silicon-probes, NeuroNexus, Ann Arbor) with 300 μm intershank space along the transverse axis of the dorsal hippocampus (Vandecasteele et al; (Figure 3.B). Animals were held under isoflurane anesthesia and, under stereotaxical guidance.…”