Figure 3. Active tactile discrimination task.

A, schematic diagram of the behavioural apparatus. Trials begin when the sliding door opens. Rats enter the centre discrimination chamber and sample the variable width aperture with their facial whiskers. Rats then poke their nose into either the left or right reward nose poke to receive a water reward: left nose poke if the aperture was narrow (60 mm), right nose poke if wide (68 mm). Immediately after, the sliding door closes and the aperture is randomly reset to wide or narrow. The next trial begins 30 s later. B, video frame captures showing a rat approaching and sampling the Narrow and Wide aperture. The 0.0 s frame (top-most frames) shows the rat breaking the infrared photobeam; the middle frame (0.1 s later) shows the whiskers initially contacting the aperture; bottom frame (0.2 s) shows the whiskers fully contacting the aperture. From Krupa et al. (2004). Reproduced with permission.