For such thalamic inputs to comodulate neurons with the same frequency preference across the three areas, the same, or correlated, thalamic neuron(s) would need to terminate within each cortical areas at points with the same frequency preference. To our knowledge, such a frequency specific pattern of thalamic inputs has not been reported. As for corticocortical connection, there are long-range anatomical connections Navitoclax purchase between cortical columns with similar stimulus frequency in the cat auditory cortex (Read et al., 2001 and Lee et al., 2004). In the macaque auditory cortex, long range connections also exist between preferred high-frequency

sites in A1 and R (Morel et al., 1993). While details of the anatomical connections to and from more rostral auditory areas have not yet been investigated systematically in the macaque, such connections between sites with similar frequency preference could account for the spontaneous covariation of the sites resembling the tonotopic GSK1120212 cost maps found in this study. It has been theoretically demonstrated

that networks of neurons with proper connections can produce spontaneous oscillatory population activity (Wilson and Cowan, 1972, Wilson and Cowan, 1973, Amari, 1977 and Wallace et al., 2011) and that spontaneous pattern formation in the visual cortex can result from the symmetry in the cortical connections (Bressloff et al., 2001) between cortical columns with similar stimulus preferences (Bosking et al., 1997). In addition, there could be another contribution to the structured spontaneous activity from the corticothalamocortical circuit, which could have a role in signal propagation from primary to higher auditory areas even in absence of corticocortical connections (Theyel et al., 2010). A rather different, though not mutually exclusive, possibility is that the structured spontaneous activity reflects the playback of information about experienced or learned stimuli. A recent study in the rodent visual cortex holds that, following the repeated presentation of a visual

stimulus, spontaneous spatiotemporal activity resembled the evoked activity and persisted in this form for several minutes after the stimulation (Han et al., 2008), raising the possibility of a link to short-term memory. This effect is similar in some respects MTMR9 to our results, but the origin of structured spontaneous activity in our data would be different from such putative short-term memory effects since our recordings of the spontaneous activity were carried out during different sessions and on different days from those in which the sensory evoked responses were mapped. Alternatively, the structured spontaneous activity in our data may reflect auditory information stored in long-term memory (if auditory long-term memory is present in the monkey; (see Fritz et al., 2005). During sleep, the “replay” of learning-related activity has been observed in the rodent hippocampus (Wilson and McNaughton, 1994) and prefrontal cortex (Euston et al.