title: Stimulus intensity determines experience-dependent modifications in neocortical neuron firing rates.
abstract: Although subthreshold inputs of neocortical sensory neurons are broadly tuned, the spiking output is more restricted. These subthreshold inputs provide a substrate for stimulus intensity-dependent changes their spiking output, as well as for experience-dependent plasticity to alter firing properties. Here we investigated how different stimulus intensities modified the firing output of individual neurons in layer 2/3 of the mouse barrel cortex. Decreasing stimulus intensity over a 30-fold range lowered the firing rates evoked by principal whisker stimulation and reduced the overall size of the responding ensemble in whisker-undeprived animals. We then examined how these responses were changed after single-whisker experience (SWE). After 7 days of SWE, the mean magnitude of response to spared whisker stimulation at the highest stimulus intensity was not altered. However, lower-intensity whisker stimulation revealed a more than 10-fold increase in mean firing output compared with control animals. Also, under control conditions, only ~15% of neurons showed any firing at low stimulus intensity, compared with more than 70% of neurons after SWE. However, response changes measured in the immediately surrounding representations were detected only for the highest stimulus intensity. Overall, these data showed that the measurement of experience-dependent changes in the spike output of neocortical neurons was highly dependent upon stimulus intensity.
authors.affiliation: Department of Biological Sciences and Center for the Neural Basis of Cognition, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213, USA; School of Life Sciences and Institute for Science and Technology in Medicine, Keele University, Keele, Staffordshire, UK.
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Glazewski
authors.forename: Alison L
authors.initials: AL
authors.lastname: Barth
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005073:Evoked Potentials, Somatosensory; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019579:Neocortex / Q000166:cytology / Q000502:physiology*; D009473:Neuronal Plasticity; D009474:Neurons / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation
keywords: cortical circuitry; glutamatergic neurotransmission; learning and memory; mouse; neocortex; plasticity