This information was also recorded on a data recorder (RT-145T; TEAC, Tokyo). buy LY2109761 The digitized neuronal activities were isolated into single units by their waveform components using the Offline Sorter program (Plexon). Superimposed waveforms of the isolated units were drawn to assess variability throughout the recording sessions and transferred to the NeuroExplorer program (Nex Technologies, MA, USA) for further analysis.

If the monkey exhibited signs of fatigue, such as closing the eyes for several seconds or moving the eyes or hands slowly, the experimental session was immediately terminated. In most cases, the unit recording experiment was terminated within 2–3 h. After responses to the 49 visual stimuli were recorded, the scrambled images were then presented to the monkeys if single unit activity was still observed. Spike sorting was performed with the offline sorter program

for cluster analysis (Off-line sorter, Plexon). Each cluster was checked manually to ensure that the cluster boundaries were well separated and the waveform shapes were consistent with the action potentials. For each isolated cluster, an autocorrelogram was constructed and only units with refractory periods > 1.2 ms were used for further analyses. Finally, superimposed waveforms of the isolated units were drawn to check the consistency of the waveforms. Figure 3A and B shows examples of superimposed waveforms of a pulvinar neuron oxyclozanide and its autocorrelogram, respectively. This autocorrelogram Trichostatin A chemical structure indicates that the refractory period of the neuron was 2–3 ms throughout the recording sessions, which suggests that these spikes were recorded from a single neuron. We analysed single neuronal activity during 500 ms after (‘post’) the onset of stimulus presentation in the sample phase, but did not analyse single neuronal activity in the target phase. Only stimuli that were presented more than five times in the sample phase were analysed. The baseline firing rate was defined as the mean firing rate during the 100-ms ‘pre’ period. Significant excitatory

or inhibitory responses to each stimulus were defined by a Wilcoxon signed rank (WSR) test (P < 0.05 for statistical significance) of neuronal activity between the 100-ms pre and the 500-ms post periods. Furthermore, to investigate temporal changes in neuronal responses, the 500-ms post period was divided into ten 50-ms epochs. The mean neuronal firing rate was calculated for each of these epochs. Response magnitude was defined as follows – mean firing rate in each epoch minus the mean firing rate during the 100-ms pre period. Figure 3C and D shows a peri-event summed histogram of responses from the same neuron shown in Fig. 3A and B to a facial photo (Fig. 3C) and response magnitudes in the 10 epochs converted from this histogram (Fig. 3D).