@Article{ NgLK2012,
title = {EEG phase patterns reflect the selectivity of neural firing},
journal = {Cerebral Cortex},
year = {2013},
month = {2},
volume = {23},
number = {2},
pages = {389-398},
abstract = {Oscillations are pervasive in encephalographic signals and supposedly reflect cognitive processes and sensory representations. While the relation between oscillation amplitude (power) and sensory–cognitive variables has been extensively studied, recent work reveals that the dynamic oscillation signature (phase pattern) can carry information about such processes to a greater degree than amplitude. To elucidate the neural correlates of oscillatory phase patterns, we compared the stimulus selectivity of neural firing rates and auditory-driven electroencephalogram (EEG) oscillations. We employed the same naturalistic sound stimuli in 2 experiments, one recording scalp EEGs in humans and one recording intracortical local field potentials (LFPs) and single neurons in macaque auditory cortex. Using stimulus decoding techniques, we show that stimulus selective firing patterns imprint on the phase rather than the amplitude of slow (theta band) oscillations in LFPs and EEG. In particular, we find that stimuli which can be discriminated by firing rates can also be discriminated by phase patterns but not by oscillation amplitude and that stimulus-specific phase patterns also persist in the absence of increases of oscillation power. These findings support a neural basis for stimulus selective and entrained EEG phase patterns and reveal a level of interrelation between encephalographic signals and neural firing beyond simple amplitude covariations in both signals.},
web_url = {http://cercor.oxfordjournals.org/content/23/2/389.full.pdf+html},
state = {published},
DOI = {10.1093/cercor/bhs031},
author = {Ng BSW{benedict}, Logothetis NK{nikos}{Department Physiology of Cognitive Processes} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Article{ NgSK2012,
title = {A precluding but not ensuring role of entrained low-frequency oscillations for auditory perception},
journal = {Journal of Neuroscience},
year = {2012},
month = {8},
volume = {32},
number = {35},
pages = {12268-12276},
abstract = {Oscillatory activity in sensory cortices reflects changes in local excitation–inhibition balance, and recent work suggests that phase signatures of ongoing oscillations predict the perceptual detection of subsequent stimuli. Low-frequency oscillations are also entrained by dynamic natural scenes, suggesting that the chance of detecting a brief target depends on the relative timing of this to the entrained rhythm. We tested this hypothesis in humans by implementing a cocktail-party-like scenario requiring subjects to detect a target embedded in a cacophony of background sounds. Using EEG to measure auditory cortical oscillations, we find that the chance of target detection systematically depends on both power and phase of theta-band (2–6 Hz) but not alpha-band (8–12 Hz) oscillations before target. Detection rates were higher and responses faster when oscillatory power was low and both detection rate and response speed were modulated by phase. Intriguingly, the phase dependency was stronger for miss than for hit trials, suggesting that phase has a inhibiting but not ensuring role for detection. Entrainment of theta range oscillations prominently occurs during the processing of attended complex stimuli, such as vocalizations and speech. Our results demonstrate that this entrainment to attended sensory environments may have negative effects on the detection of individual tokens within the environment, and they support the notion that specific phase ranges of cortical oscillations act as gatekeepers for perception.},
web_url = {http://www.jneurosci.org/content/32/35/12268.full.pdf+html},
state = {published},
DOI = {10.1523/​JNEUROSCI.1877-12.2012},
author = {Ng BS-W{benedict}, Schroeder T{tschroeder}{Research Group Physiology of Sensory Integration} and Kayser C{kayser}{Department Physiology of Cognitive Processes}{Research Group Physiology of Sensory Integration}}
}

@Poster{ NgK2011,
title = {Psychophysical assessment of auditory feature selection during acoustic tasks in the rat},
year = {2011},
month = {11},
volume = {41},
number = {173.21},
abstract = {Natural auditory objects are complex and often composed of more than one defining acoustic feature. However, not all features are usually essential for the spontaneous identification of a given object and a given object can often be detected or discriminated using several of its features. For example, a dynamically moving sound might be localized by its immediate intensity difference between the ears or by slower changes in amplitude over time. How different stimulus features for object discrimination are selected in the brain is not well understood. In addition, it remains unclear how the fidelity of cue selection may be dynamically altered in a given task context. The goal of this project is to explore a rodent model to study the neural basis of sound feature selection in acoustic discrimination.
We tested rats in an acoustic motion discrimination task, where the animals had to discriminate right- and left-ward moving sounds. The two stimuli consisted of white noise pulses that were simultaneously presented from each side of the operant conditioning box. The percept of horizontal motion was then imposed by modulating the amplitude of these two streams in opposite directions over time and by a difference in the initial amplitude of the left and right streams. This provided two potential cues to solve the task, the relative weighting of which could also be manipulated by changing the level of amplitude difference between both streams. Using reaction time and correct percept identification as behavioral metrics, we found that rats spontaneously developed a preference for one of the two stimulus features for discrimination, mainly for stimulus onset. Interestingly, however, individual animals sometimes relied on different features to identify each stimulus (leftward or rightward moving). These results provide the grounds to study the neural mechanism of this stimulus selection and encoding, and pave the way for a more detailed analysis of the spontaneous selection of features for auditory identification tasks. Specifically, our results highlight the heterogeneity in the strategies developed by animals to solve sensory tasks and parallel previous results found by studies in the visual system.},
web_url = {http://www.sfn.org/am2011/},
event_name = {41st Annual Meeting of the Society for Neuroscience (Neuroscience 2011)},
event_place = {Washington, DC, USA},
state = {published},
author = {Ng BS{benedict} and Kayser C{kayser}{Research Group Physiology of Sensory Integration}}
}