The use of cables for recording neural activity limits the scope of behavioral tests used in conscious free-moving animals. Particularly, cable attachments make it impossible to record in three-dimensional (3D) mazes where levels are vertically stacked or in enclosed spaces. Such environments are of particular interest in investigations of hippocampal place cells, in which neural activity is correlated with spatial position in the environment. We developed a flexible miniaturized Bluetooth-based wireless data acquisition system. The wireless module included an 8-channel analogue front end, digital controller, and Bluetooth transceiver mounted on a backpack. Our bidirectional wireless design allowed all data channels to be previewed at 1 kHz sample rate, and one channel, selected by remote control, to be sampled at 10 kHz. Extracellular recordings of neuronal activity are highly susceptible to ambient electrical noise due to the high electrode impedance. Through careful design of appropriate shielding and hardware configuration to avoid ground loops, mains power and Bluetooth hopping frequency noise were reduced sufficiently to yield signal quality comparable to those recorded by wired systems. With this system we were able to obtain single-unit recordings of hippocampal place cells in rats running an enclosed vertical maze, over a range of 5 m.
Single-unit recording Wireless telemetry Freely moving rats Place cell
This is a preview of subscription content, log in to check access.
This project was partially supported by grants from the National Science Council, Taiwan, R.O·C. (NSC93-2213-E-006-046) and from the National Health Research Institute of R.O·C. under contract no. NHRI-EX 95-9524E1.
Barrett CJ, Guild SJ, Ramchandra R et al (2005) Baroreceptor denervation prevents sympathoinhibition during angiotensin II-induced hypertension. Hypertension 46:168–172CrossRefGoogle Scholar
Brun VH, Otnass MK, Molden S et al (2002) Place cells and place recognition maintained by direct entorhinal-hippocampal circuitry. Science 296:2243–2246CrossRefGoogle Scholar
Chen HY, Wu JS, Li CP et al (2008) Wireless telemetry system for single-unit recording in rats navigation. J Chin Inst Eng 31:449–458Google Scholar
Fenton AA, Muller RU (1998) Place cell discharge is extremely variable during individual passes of the rat through the firing field. Proc Natl Acad Sci USA 95:3128CrossRefGoogle Scholar
Fox SE, Ranck JBJ (1981) Electrophysiological characteristics of hippocampal complex-spike cells and theta cells. Exp Brain Res 41:399–410CrossRefGoogle Scholar
Hawley ES, Hargreaves EL, Kubie JL et al (2002) Telemetry system for reliable recording of action potentials from freely moving rats. Hippocampus 12:505–513CrossRefGoogle Scholar
Jeffery KJ, Anand RL, Anderson MI (2006) A role for terrain slope in orienting hippocampal place fields. Exp Brain Res 169:218–225CrossRefGoogle Scholar
Jeffery KJ, Anderson MI, Hayman R, Chakraborty S (2004) A proposed architecture for the neural representation of spatial context. Neurosci Biobehav Rev 28:201–218CrossRefGoogle Scholar
Knierim JJ, McNaughton BL (2001) Hippocampal place-cell firing during movement in three-dimensional space. J Neurophysiol 85:105–116Google Scholar
Lenck-Santini PP, Save E, Poucet B (2001) Evidence for a relationship between place-cell spatial firing and spatial memory performance. Hippocampus 11:377–390CrossRefGoogle Scholar
O’keefe J, Dostrovsky J (1971) The hippocampus as a spatial map Preliminary evidence for unit activity in the freely-moving rat. Brain Res 34:171–175CrossRefGoogle Scholar
Obeid I, Nicolelis MA, Wolf PD (2004) A multichannel telemetry system for single unit neural recordings. J Neurosci Methods 133:33–38CrossRefGoogle Scholar
Shapiro ML, Tanila H, Eichenbaum H (1997) Cues that hippocampal place cells encode: dynamic and hierarchical representation of local and distal stimuli. Hippocampus 7:624–642CrossRefGoogle Scholar
Uemura K, Kawada T, Sugimachi M et al (2004) A self-calibrating telemetry system for measurement of ventricular pressure-volume relations in conscious, freely moving rats. Am J Physiol Heart Circ Physiol 287:H2906–H2913CrossRefGoogle Scholar