Epicranial sensory evoked potential recordings for repeated assessment of cortical functions in mice

In the present study, we describe a simple and minimally invasive method to record sensory evoked potentials (SEP) in the anesthetized mouse. The hardware includes a 16-channel acquisition system with a high signal/noise ratio and high temporal resolution. Under general anesthesia the skull is exposed and stainless steel electrodes are placed directly over the bone. A computer controlled electromechanical stimulation is applied to a single whisker or a group of whiskers unilaterally and cortical responses are recorded bilaterally. Primary SEP are detected over the contralateral barrel cortex, but delayed signals appear over the motor cortex, secondary somatosensory cortex and the ipsilateral hemisphere. The size of evoked SEP correlates with the number of stimulated whiskers and responses are reproducible and consistent over time when recorded repeatedly for up to 6 weeks. We conclude that epicranial multichannel recording of SEP represents an interesting, minimally invasive approach to monitor repeatedly cortical activity and study certain aspects of long-term plasticity of evoked responses in mice.