Abstract
There is growing evidence that ongoing brain oscillations may represent a key regulator of attentional processes and as such may contribute to behavioral performance in psychophysical tasks. OFC appears to be involved in the top-down modulation of sensory processing; however, the specific contribution of ongoing OFC oscillations to perception has not been characterized. Here we used the rat whiskers as a model system to further characterize the relationship between cortical state and tactile detection. Head-fixed rats were trained to report the presence of a vibrotactile stimulus (frequency = 60 Hz, duration = 2 sec, deflection amplitude = 0.01-0.5 mm) applied to a single vibrissa. We calculated power spectra of local field potentials preceding the onset of near-threshold stimuli from microelectrodes chronically implanted in OFC and somatosensory cortex. We found a dissociation between slow oscillation power in the two regions in relation to detection probability: Higher OFC but not somatosensory delta power was associated with increased detection probability. Furthermore, coherence between OFC and barrel cortex was reduced preceding successful detection. Consistent with the role of OFC in attention, our results identify a cortical network whose activity is differentially modulated before successful tactile detection.
Highlights
Considerable evidence supports the role of prefrontal cortex in higher-order sensory processing including stimulus categorization and the top-down control of sensory inputs (Fritz et al, 2010; Everling et al, 2006; McKee et al, 2014; Fritz et al, 2007; Ding, 2015)
We found a clear dissociation between orbitofrontal cortex (OFC) and somatosensory cortex: in overtrained animals stronger delta oscillations in OFC but not in somatosensory cortex were associated with higher detection probability
The correlation coefficient was non-significant both across animals and for each individual animal. These calculations suggest that the behavioural results presented here are unlikely to be driven by discrimination between lower and higher amplitude stimuli, but rather are consistent with the view that they depend on detection
Summary
Considerable evidence supports the role of prefrontal cortex in higher-order sensory processing including stimulus categorization and the top-down control of sensory inputs (Fritz et al, 2010; Everling et al, 2006; McKee et al, 2014; Fritz et al, 2007; Ding, 2015). OFC has a critical role in associative learning and decision-making through its representation of the rewardand punishment-value of sensory cues These observations suggest that sensory information in this structure is subject to top-down cognitive and/or attentional modulation (Bouret and Richmond, 2010; Kringelbach, 2005; Takahashi et al, 2009; Cooch et al, 2015; Neubert et al, 2015). Behavioral evidence that pre-stimulus cortical oscillatory activity modulates detection of near-threshold stimuli comes primarily from human EEG studies in regions other than OFC (Pleger and Villringer, 2013; Schubert et al, 2009; Linkenkaer-Hansen et al, 2004). There is evidence that ongoing behavioral state affects prefrontal and sensory cortical representations, yet even though OFC shows robust sensory responses and neurophysiological interactions with sensory cortices, the role of ongoing fluctuations in this structure in perceptual decisions has not been studied. Further supporting the dissociation between structures we found that higher detection probability was associated with lower pre-stimulus coherence between the two regions
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