The higher correlations among neurons that are not tuned for the attended location

Bcl-2 apoptosis pathway or feature may be a hallmark of neuronal populations that are not well-driven or engaged in a task. A recent study found that trial-to-trial variability in individual neurons in seven cortical areas is higher when the cells are not well-driven, even after correcting for the expected effects of a lower rate of firing (Churchland et al., 2010). This effect may be a signature of a network in which stimulus drive suppresses correlated ongoing activity (Rajan et al., 2010). At low frequencies, both spike-field coherence and cortical oscillations in the local field potential are higher for populations encoding unattended stimuli (Fries et al., 2001, Gregoriou et al., 2009 and Womelsdorf et al., 2007). In humans, withdrawing attention increases www.selleckchem.com/products/LBH-589.html low frequency oscillations in MEG signals (Siegel et al., 2008), and functional connectivity (and therefore

variability) is often higher during the spontaneous “resting state” than when neural populations are well-driven (for review see van den Heuvel and Hulshoff Pol, 2010). In contrast, attention increases spike-field coherence and oscillations at high frequencies (Fries et al., 2001, Gregoriou et al., 2009 and Womelsdorf and Fries, 2007). These increases have been hypothesized to improve communication between sensory neurons and downstream cells by improving the probability that synchronous spikes

Ampicillin will drive a post-synaptic cell above threshold (for review see Womelsdorf and Fries, 2007); but see also (Ray and Maunsell, 2010). Attentional increases in high frequency correlations are not inconsistent with the reductions in low frequency correlations we and others have reported. In principle, the two could work in concert to remove correlations on long timescales while improving neural communication on short timescales. The observation that even in a controlled experimental setting, both spatial and feature attention vary substantially (Figure 5) suggests that all aspects of a subject’s internal state vary from moment to moment and that it is impossible to measure any particular cognitive factor in isolation. The spatial and feature attention axes we defined, which measure differences in the amount of attention allocated to two particular locations and two seemingly nonopposed features, are by no means the only aspects of attention that could vary. The animal may allocate attention to locations other than these two stimuli (e.g., the fixation point or the door to the room) and to features other than orientation or spatial frequency, or other sensory modalities.