This finding supports the ability of ICMS to selectively target restricted ensembles of cortical 3-MA datasheet neurons. The ability to reproducibly evoke distinct complex movements from multiple cortical sites presents an opportunity to perform further investigations of motor circuitry in a widely used model organism. More importantly, it will allow the advantages of genetic engineering in mice to be applied to the problem of motor cortex function and organization, either for optical circuit analysis (Zhang et al., 2007,

Tian et al., 2009 and Chow et al., 2010) or in the search for future treatments for movement disorders, cortical injuries, and paralysis (Hodgson et al., 1999, Dancause, 2006, Murphy and Corbett, 2009, Dawson et al., 2010 and Vargas-Irwin et al., 2010). Animal protocols were approved by the University of British Columbia Animal Care Committee. Channelrhodopsin-2 transgenic mice (Arenkiel et al., 2007) from Jackson Labs (line 18, stock 007612, strain B6.Cg-Tg(Thy1-COP4/EYFP)18Gfng/J) established a breeding colony. Adult mice aged 2–6 months and weighing 20–30 g

were used for these experiments. Isoflurane anesthesia was used during surgery and intrinsic optical signal imaging of somatosensory representations, but was replaced by ketamine/xylazine (100/10 mg/kg, supplemented at 1/10th initial dose as necessary) prior to motor mapping. Craniectomies were performed on transgenic mice used in no acute experiments, but virally transduced mice (see section below for details on injections) were mapped through the intact skull due to concern that multiple cranial surgeries could damage the cortex. Chronic mapping was performed through DAPT research buy a cranial window (Harrison et al., 2009). Light-based mapping methodology has been described in detail (Ayling et al., 2009). Briefly, we used a scanning stage (ASI MS-2000) controlled by custom Igor Pro software (Wavemetrics) to direct a fixed 473 nm laser beam (Crystalaser, focused to 100 μm diameter, 10 ms pulses, 0.5–10 mW total or 63–1,270 mW/mm2) to an array of cortical sites (typically 13 × 13, with 300 μm

spacing between sites). This process was repeated three to five times to obtain a mean value for each pixel of the map. Stimulation was delivered in a semi-random order with identical stimulus intensity for all sites within a map. Movements were detected using laser range finders with mm sensitivity targeted to the forelimb and hindlimb (Keyence LK-081). In order to exclude artifacts (e.g., from breathing or electrical noise), responses were considered to be genuine only if their amplitude exceeded three times the standard deviation of the 500 ms prestimulus period within 100 ms after stimulus onset. Motor maps were generated by plotting the peak amplitude of the mean movement profile corresponding to each cortical site of stimulation. Amplitude was quantified within a 300 ms time window after laser stimulation.