1. Bernstein Center for Computational Neuroscience and Humboldt University Berlin, Philippstrasse 13, House 6, 10115 Berlin, Germany
2. Department of Neuroscience, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands

Correspondence to: Arthur R. Houweling^1,2Michael Brecht^1,2 Correspondence and requests for materials should be addressed to A.R.H. (Email: arthur.houweling@bccn-berlin.de) or M.B. (Email: michael.brecht@bccn-berlin.de).

Abstract

Understanding how neural activity in sensory cortices relates to perception is a central theme of neuroscience. Action potentials of sensory cortical neurons can be strongly correlated to properties of sensory stimuli¹ and reflect the subjective judgements of an individual about stimuli². Microstimulation experiments have established a direct link from sensory activity to behaviour^{3, 4}, suggesting that small neuronal populations can influence sensory decisions⁵. However, microstimulation does not allow identification and quantification of the stimulated cellular elements⁶. The sensory impact of individual cortical neurons therefore remains unknown. Here we show that stimulation of single neurons in somatosensory cortex affects behavioural responses in a detection task. We trained rats to respond to microstimulation of barrel cortex at low current intensities. We then initiated short trains of action potentials in single neurons by juxtacellular stimulation. Animals responded significantly more often in single-cell stimulation trials than in catch trials without stimulation. Stimulation effects varied greatly between cells, and on average in 5% of trials a response was induced. Whereas stimulation of putative excitatory neurons led to weak biases towards responding, stimulation of putative inhibitory neurons led to more variable and stronger sensory effects. Reaction times for single-cell stimulation were long and variable. Our results demonstrate that single neuron activity can cause a change in the animal's detection behaviour, suggesting a much sparser cortical code for sensations than previously anticipated.

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