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The Journal of Neuroscience, October 8, 2003, 23(27):9146-9154

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Behavioral/Systems/Cognitive
Encoding of Whisker Vibration by Rat Barrel Cortex Neurons: Implications for Texture Discrimination

Ehsan Arabzadeh, Rasmus S. Petersen, and Mathew E. Diamond

Cognitive Neuroscience Sector, International School for Advanced Studies, 34014 Trieste, Italy

Rats, using their whiskers, have excellent capabilities in texture discrimination. What is the representation of texture in rat somatosensory cortex? We hypothesize that as rats "whisk" over a surface, the spatial frequency of a grooved or pebbled texture is converted to a temporal frequency of whisker vibration. Surface features such as groove depth or grain size modulate the amplitude of this vibration. Validation of the hypothesis depends on showing that vibration parameters have distinct neuronal representations in cortex. To test this, we delivered sinusoidal vibrations to the whisker shaft and analyzed cortical neuronal activity. Seven amplitudes and seven frequencies were combined to construct 49 stimuli while recording activity through a 10 x 10 microelectrode array inserted into the middle layers of barrel cortex. We find that cortical neurons do not explicitly encode vibration frequency (f) or amplitude (A) by any coding measure (average spike counts over different time windows, spike timing patterns in the peristimulus time histograms or in autocorrelograms). Instead, neurons explicitly encode the product of frequency and amplitude, which is proportional to the mean speed of the vibration. The quantity Af is an invariant because neuronal response encodes this feature independently of the values of the individual terms A and f. This was true across a wide time scale of firing rate measurements, from 5 to 500 msec. We conclude that vibration kinetics are rapidly and reliably encoded in the firing rate of cortical ensembles. Therefore, the cortical representation of vibration speed could underlie texture discrimination.

Key words: barrel; cortex; tactile; vibrissae; texture; vibration

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Received May 23, 2003; revised August 14, 2003; accepted August 14, 2003.

This article has been cited by other articles:

				E. Lottem and R. Azouz Mechanisms of Tactile Information Transmission through Whisker Vibrations J. Neurosci., September 16, 2009; 29(37): 11686 - 11697. [Abstract] [Full Text] [PDF]

				F. Montani, R. A. A. Ince, R. Senatore, E. Arabzadeh, M. E. Diamond, and S. Panzeri The impact of high-order interactions on the rate of synchronous discharge and information transmission in somatosensory cortex Phil Trans R Soc A, August 28, 2009; 367(1901): 3297 - 3310. [Abstract] [Full Text] [PDF]

				E. Lottem and R. Azouz Dynamic Translation of Surface Coarseness Into Whisker Vibrations J Neurophysiol, November 1, 2008; 100(5): 2852 - 2865. [Abstract] [Full Text] [PDF]

				T. A. S. Ewert, C. Vahle-Hinz, and A. K. Engel High-Frequency Whisker Vibration Is Encoded by Phase-Locked Responses of Neurons in the Rat's Barrel Cortex J. Neurosci., May 14, 2008; 28(20): 5359 - 5368. [Abstract] [Full Text] [PDF]

				A. Lak, E. Arabzadeh, and M. E. Diamond Enhanced Response of Neurons in Rat Somatosensory Cortex to Stimuli Containing Temporal Noise Cereb Cortex, May 1, 2008; 18(5): 1085 - 1093. [Abstract] [Full Text] [PDF]

				M. Inan and M. C. Crair Development of Cortical Maps: Perspectives From the Barrel Cortex Neuroscientist, February 1, 2007; 13(1): 49 - 61. [Abstract] [PDF]

				Y. Katz, J. E. Heiss, and I. Lampl Cross-Whisker Adaptation of Neurons in the Rat Barrel Cortex J. Neurosci., December 20, 2006; 26(51): 13363 - 13372. [Abstract] [Full Text] [PDF]

				E. Arabzadeh, S. Panzeri, and M. E. Diamond Deciphering the Spike Train of a Sensory Neuron: Counts and Temporal Patterns in the Rat Whisker Pathway J. Neurosci., September 6, 2006; 26(36): 9216 - 9226. [Abstract] [Full Text] [PDF]

				J. Hipp, E. Arabzadeh, E. Zorzin, J. Conradt, C. Kayser, M. E. Diamond, and P. Konig Texture Signals in Whisker Vibrations J Neurophysiol, March 1, 2006; 95(3): 1792 - 1799. [Abstract] [Full Text] [PDF]

				E. Arabzadeh, S. Panzeri, and M. E. Diamond Whisker Vibration Information Carried by Rat Barrel Cortex Neurons J. Neurosci., June 30, 2004; 24(26): 6011 - 6020. [Abstract] [Full Text] [PDF]

				C. I. Moore Frequency-Dependent Processing in the Vibrissa Sensory System J Neurophysiol, June 1, 2004; 91(6): 2390 - 2399. [Abstract] [Full Text] [PDF]

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