Second-order conditioning using light, tone and foot-shock was carried out. On day 1, blood flow was monitored during the tone-shock conditioning; as a result, the conditioned response was observed in the third to fifth trial. On day 2, pairing of light and tone was repeated five times. Blood flow change to the light stimulus was monitored in the pre-test (day-2) and test (day-3); as a result, the conditioned response to light was observed after the light-tone conditioning, proving second-order conditioning to be successful. Next, neural activities in the auditory, visual, and somatosensory cortices were recorded by optical imaging. In order to identify the location of these three cortical areas, cortical activities in the recording sites to light, foot-shock, and tone stimuli were investigated. Figure 2a shows a schematic diagram of cortical areas including visual, somatosensory and auditory cortices as reported by Woolsey and Van der Loos [4]. Figure 2b shows cortical activity to a light stimulus, suggesting that the activated area is primary visual cortex.