Similar to humans, the beta band in the monkey entorhinal cortex showed clear increases across performance levels. Surprisingly, a similar learning signal was not seen in either LFP frequency band of the monkey hippocampus, a structure that exhibits strong associative-learning related signals at the single cell level in the same task (Wirth et al., 2003). This may be due to a number of different factors. For example, the presence of similar number of increasing and decreasing responses at the single

cell level with learning in the hippocampus might have masked the LFP signal. alternatively this absence of learning signal in the monkey hippocampal LFP may be due to the broad sensitivity of the LFP signal. For example, recent reports from population analyses in monkeys and rodents revealed that hippocampal neurons convey significant PLX 4720 information about incremental timing both within a trial (MacDonald et al., 2011 and Naya and Suzuki, 2011) as well as across the entire recording session (Manns et al., 2007). These findings may relate to our observation that striking changes over the time course of the trial were observed in both the beta and gamma bands of the monkey hippocampus

(Figure S2B) and may have overwhelmed the associative learning signals in this region. Our findings show that for associative learning signals, the pattern of beta band activity in the monkey entorhinal cortex corresponded best to the BOLD fMRI signal in humans. However it is tempting to ask the more general question of which LFP www.selleckchem.com/products/nlg919.html frequency band in monkeys corresponds best to BOLD fMRI signals seen in humans across all signals examined. Our findings show mixed results and that there may be neither a simple one-to-one equivalence nor even a consistently superior mapping (Table S1). When considering examples where

the polarity was identical across species or all examples in which significant differential signals were observed irrespective of polarity, there are Phosphatidylinositol diacylglycerol-lyase cases of beta band, gamma band, and in some cases both frequency bands corresponding to the BOLD fMRI signal. However, there is a slight numerical advantage for the beta band to correspond in more cases. These findings differ from the reports of Logothetis (2002) and Goense and Logothetis (2008) in area V1 where they saw the best correspondence between the gamma band and the BOLD fMRI signal. Together, these suggest that the relationship between LFP and BOLD, although clearly present, is not a simple one and that details of the underlying neural signals, representations, neurotransmitters, and other differences across brain regions may affect the relationships between LFP and BOLD fMRI signals. A major goal in neuroscience research is to understand how the detailed neurophysiological underpinnings of higher cognitive functions, often measured in nonhuman primates, correspond to human neurophysiology.