Low-frequency neuronal oscillations as instruments of sensory selection

Abstract

Neuroelectric oscillations reflect rhythmic shifting of neuronal ensembles between high and low excitability states. In natural settings, important stimuli often occur in rhythmic streams, and when oscillations entrain to an input rhythm their high excitability phases coincide with events in the stream, effectively amplifying neuronal input responses. When operating in a 'rhythmic mode', attention can use these differential excitability states as a mechanism of selection by simply enforcing oscillatory entrainment to a task-relevant input stream. When there is no low-frequency rhythm that oscillations can entrain to, attention operates in a 'continuous mode', characterized by extended increase in gamma synchrony. We review the evidence for early sensory selection by oscillatory phase-amplitude modulations, its mechanisms and its perceptual and behavioral consequences.

Encoding of event timing in the phase of neural oscillations

“…alpha oscillations, Gho and Varela, 1988;Jensen et al, 2012;VanRullen and Koch, 2003;Varela et al, 1981) and overt sampling (e.g. (micro)saccades, Schroeder and Lakatos, 2009), the auditory system may necessitate temporal-locking to incoming acoustic inputs to accurately represent information over time (Giraud and Poeppel, 2012;Henry and Obleser, 2012;Stefanics et al, 2010;Thorne et al, 2011). Hence, while visual timing may rely on an internally generated temporal reference frame, audition may require the establishment of a temporal reference frame on the go and locked to the temporal statistics of the auditory environment.…”

“…In cortex, low-frequency neural oscillations are known to regulate the excitability of neural ensembles such that specific phases of lowfrequency neural oscillations are associated with periods of high and low neuronal excitability (Buzsáki, 2010;Lakatos et al, 2008;Schroeder and Lakatos, 2009): the phase of low-frequency neural oscillations modulates the power of high-frequency neural oscillatory responses, a mechanism known as phase-power or cross-frequency coupling (Canolty et al, 2006). Neural synchronizations in higher frequency ranges (e.g.…”

“…They have also been proposed to serve parsing and informational chunking of sensory information over time (VanRullen and Koch, 2003) notably for complex temporal structures such as speech (Giraud and Poeppel, 2012). Indeed, neural oscillations are known to be entrained to external rhythms (Rees et al, 1986;Regan, 1966) and this entrainment may allow the alignment of cortical processing to the timing of sensory events (Giraud and Poeppel, 2012;Schroeder and Lakatos, 2009). As such, this mechanism naturally provides a means for the brain to internalize external temporal regularities (Schroeder and Lakatos, 2009).…”

“…Indeed, neural oscillations are known to be entrained to external rhythms (Rees et al, 1986;Regan, 1966) and this entrainment may allow the alignment of cortical processing to the timing of sensory events (Giraud and Poeppel, 2012;Schroeder and Lakatos, 2009). As such, this mechanism naturally provides a means for the brain to internalize external temporal regularities (Schroeder and Lakatos, 2009). In line with this proposal, the phase of low-frequency neural oscillations has been shown to reflect temporal expectancy or predictability of event timing (Stefanics et al, 2010).…”

Effects of Spectral Degradation on Attentional Modulation of Cortical Auditory Responses to Continuous Speech

“…We argue that high spectral resolution can support sound segregation and, as a result, selective attention can operate on the individually perceived auditory objects, enhancing the neural representation of the attended speech and suppressing the neural representation of unattended speech (Horton et al 2013;Kong et al 2014). The brain can do so by using temporal coherence to bind together acoustic features belonging to the same speech stream (Shamma et al 2011) or by predicting which moments contain more information about the attended speech than the competing speech (Schroeder et al 2008;Schroeder and Lakatos 2009;Zion-Golumbic et al 2013).…”