(1994), Carmichael & Price (1995), Freedman et al. (2000) and Paxinos et al. (2000). Digital image files were imported into Adobe Photoshop 7 or CS3 and this website were processed routinely for grey/colour levels, brightness and contrast before being composed into figure illustrations for publication. The data were obtained in two behaving unanaesthetized young adult macaque monkeys (BM, BQ). A total of 249 neurons were screened in both animals [172 (69%) in BM and 77 (31%) in BQ] using a selection of visual, auditory, gustatory, somatosensory and olfactory stimuli (Rolls, 2008). In addition, the firing rates of each cell were assessed

to see if they were influenced by eye-closure during periods when the animals were not being actively tested. Figure 1A illustrates the wide areal distribution of the 249 electrophysiologically sampled cells in the PFC. The single neuron recordings were made from mPFC areas – BAs 9, 10, 13 m, 14c, 24b (dorsal anterior cingulate cortex) and 32 (pregenual area; Fig. 1B). The anterior–posterior extent of the recordings ranged from + 10 mm to + 14 mm anterior to the posterior lip of the sphenoid bone (Fig. 1C–E). After a period without behavioural testing and interaction with the experimenter, the subjects would adopt a relaxed position in their chairs in which the arms and legs

became motionless, and the eyelids would gradually droop and eventually close. When closed, the eyes showed a slow drift buy Y-27632 typical of drowsiness

prior to entry into SWS. These behavioural criteria for the animals being ‘awake’ (BS3 – eyes-open), ‘drowsy’ (BS2 – partial eye-closure) or ‘asleep’ (BS1 – eyes-closed) were made from live images of the monkeys displayed on a video monitor placed outside the hexagonal recording chamber (Balzamo et al., 1998). ECG evidence obtained during the initial recording sessions in both animals confirmed that when the animals were in BS1 they were most probably in a state of SWS (Fig. 2). Several distinct types of neuronal responses were observed as the animals passed between BS1, 2 and 3 (see Table 1 and Figs 5 and 6). As a result, a preliminary cell classification Megestrol Acetate based on significant changes in firing rates associated with BS1, 2 and 3 was defined (see Figs 3-7 and Tables 1 and 2): Type 1 cells (28.1% of the screened population) significantly increased (+ 329 ± 26%; mean ± SEM, n = 70; P ≪ 0.01) their firing rate from the spontaneous rate when the subjects closed their eyes and went to sleep (mean ± SEM, n = 70; Awake = 3.1 ± 0.4 spikes/s; Asleep = 10.2 ± 0.8 spikes/s; P ≪ 0.01; P = 3.4 × 10−15). Type 2 cells (6.0% of the screened population) significantly decreased (−68 ± 7.2%; mean ± SEM, n = 15; P < 0.01) their firing rate on eye-closure, returning to their former level of activity with eye-reopening (mean ± SEM, n = 15: Awake = 7.7 ± 1.7 spikes/s; Asleep 2.5 ± 0.9 spikes/s; P < 0.05; P = 1.1 × 10−2). Type 3 cells (65.