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Cerebral Cortex Advance Access originally published online on August 21, 2007
Cerebral Cortex 2008 18(5):1085-1093; doi:10.1093/cercor/bhm144
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© The Author 2007. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Enhanced Response of Neurons in Rat Somatosensory Cortex to Stimuli Containing Temporal Noise

Armin Lak1, Ehsan Arabzadeh2 and Mathew E. Diamond1

1 Cognitive Neuroscience Sector, International School for Advanced Studies (SISSA), Via Beirut 2/4, 34014 Trieste Italy and Italian Institute of Technology—SISSA Unit, 2 School of Psychology, The University of Sydney, New South Wales 2006, Australia

Address correspondence to email: diamond{at}sissa.it.

Sensory stimuli under natural conditions often consist of a temporally irregular sequence of events, contrasting with the periodic sequences commonly used as stimuli in the laboratory. These experiments compared the responses of neurons in rat barrel cortex with trains of whisker movements with different frequencies; each train possessed either a periodic or an irregular, "noisy" temporal structure. Periodic stimulus trains were composed of a sequence of 21 whisker deflections separated by 20 equal interdeflection intervals (IDIs). Noisy trains were matched for mean IDI but included intervals shorter and longer than the mean IDI. Cortical responses were equivalent for periodic and noisy stimuli for frequencies up to 10 Hz. Above 10 Hz, temporal noise led to a larger response magnitude, and this effect was amplified as deflection frequency increased. Noise also caused a sharpening of the temporal precision of response to the individual deflections of the stimulus train. Cortical neurons thus appear to be "tuned" to respond in a different way to stimuli characterized by temporal unpredictability. As a consequence, perceptual judgments that depend on somatosensory cortical firing rate may be affected by the presence of temporal noise.

Key Words: barrel cortex • coding • frequency • discrimination • information • vibrissae


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