Conscious updating is a rhythmic process

Chakravarthi, Ramakrishna; VanRullen, Rufin

doi:10.1073/pnas.1121622109

Cited by 100 publications

(116 citation statements)

References 33 publications

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“…The current study has demonstrated that oscillatory phase shapes syllable perception and that this phase difference matches temporal statistics in the environment. To determine whether this type of phase sensitization is a common neural mechanism, it is necessary to investigate other types of temporal statistics, especially because it could provide a mechanism for separating different representations (26,29,30) and offer an efficient way of coding time differences (31). Future research needs to investigate whether also other properties are encoded in phase, revealing the full potential of this type of phase coding scheme.…”

Section: Resultsmentioning

confidence: 99%

Oscillatory phase shapes syllable perception

Oever

Sack

2015

Proc. Natl. Acad. Sci. U.S.A.

109

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The role of oscillatory phase for perceptual and cognitive processes is being increasingly acknowledged. To date, little is known about the direct role of phase in categorical perception. Here we show in two separate experiments that the identification of ambiguous syllables that can either be perceived as /da/ or /ga/ is biased by the underlying oscillatory phase as measured with EEG and sensory entrainment to rhythmic stimuli. The measured phase difference in which perception is biased toward /da/ or /ga/ exactly matched the different temporal onset delays in natural audiovisual speech between mouth movements and speech sounds, which last 80 ms longer for /ga/ than for /da/. These results indicate the functional relationship between prestimulus phase and syllable identification, and signify that the origin of this phase relationship could lie in exposure and subsequent learning of unique audiovisual temporal onset differences.oscillations | phase | audiovisual | speech | temporal processing I n spoken language, visual mouth movements naturally precede the production of any speech sound, and therefore serve as a temporal prediction and detection cue for identifying spoken language (1) (but also see ref.2). Different syllables are characterized by unique visual-to-auditory temporal asynchronies (3, 4). For example, /ga/ has an 80-ms longer delay than /da/, and this difference aids categorical perception of these syllables (4). We propose that neuronal oscillations might carry the information to dissociate these syllables based on temporal differences. Multiple authors have proposed (5-7)-and it has been demonstrated empirically (7-9)-that at the onset of visual mouth movements, ongoing oscillations in auditory cortex align (see refs. 10-12 for nonspeech phase reset), providing a temporal reference frame for the auditory processing of subsequent speech sounds. Consequently, auditory signals fall on different phases of the aligned oscillation depending on the unique visualto-auditory temporal asynchrony, resulting in a consistent relationship between syllable identity and oscillatory phase.We hypothesized that this consistent "phase-syllable" relationship results in ongoing oscillatory phase biasing syllable perception. More specifically, the phase at which syllable perception is mostly biased should be proportional to the visual-toauditory temporal asynchrony found in natural speech. A naturally occurring /ga/ has an 80-ms longer visual-to-auditory onset difference than a naturally occurring /da/ (4). Consequently, the phase difference between perception bias toward /da/ and /ga/ should match 80 ms, which can only be established with an oscillation with a period greater than 80 ms, that is, any oscillation under 12.5 Hz. The apparent relevant oscillation range is therefore theta, with periods ranging between 111 and 250 ms (4-9 Hz). This oscillation range has already been proposed as a candidate to encode information, and seems specifically important for speech perception (13,14).To test this hypothesis of oscill...

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Section: Resultsmentioning

confidence: 99%

Oscillatory phase shapes syllable perception

Oever

Sack

2015

Proc. Natl. Acad. Sci. U.S.A.

109

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“…EEG studies have previously tested the idea that the order of visual events was coded in the phase of the alpha oscillatory component (Gho and Varela, 1988) and recent studies have pointed out to the role of theta/alpha in temporal visual illusions (Chakravarthi and Vanrullen, 2012;VanRullen et al, 2006). These studies suggest that intrinsic oscillations are recruited for the encoding of events in the absence of external temporal regularities.…”

Section: A Canonical Role For the Phase Of Intrinsic And Entrained Nementioning

confidence: 99%

“…Under this latency code hypothesis, timing mechanisms are based on the changes of neural routing delays in sensory areas coding for a specific sensory attribute (Moutoussis and Zeki, 1997;Zeki and Bartels, 1998). To date however, electroencephalographic (EEG) studies have reported little-to-no correspondence between neural latencies and participants' perceived timing (McDonald et al, 2005;Vibell et al, 2007), and rather suggest that it is the phase of neural oscillations that plays a crucial role in the encoding of visual event timing (Chakravarthi and Vanrullen, 2012;Gho and Varela, 1988).…”

Section: Introductionmentioning

confidence: 99%

Encoding of event timing in the phase of neural oscillations

2014

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a b s t r a c t a r t i c l e i n f oTime perception is a critical component of conscious experience. To be in synchrony with the environment, the brain must deal not only with differences in the speed of light and sound but also with its computational and neural transmission delays. Here, we asked whether the brain could actively compensate for temporal delays by changing its processing time. Specifically, can changes in neural timing or in the phase of neural oscillation index perceived timing? For this, a lag-adaptation paradigm was used to manipulate participants' perceived audiovisual (AV) simultaneity of events while they were recorded with magnetoencephalography (MEG). Desynchronized AV stimuli were presented rhythmically to elicit a robust 1 Hz frequency-tagging of auditory and visual cortical responses. As participants' perception of AV simultaneity shifted, systematic changes in the phase of entrained neural oscillations were observed. This suggests that neural entrainment is not a passive response and that the entrained neural oscillation shifts in time. Crucially, our results indicate that shifts in neural timing in auditory cortices linearly map participants' perceived AV simultaneity. To our knowledge, these results provide the first mechanistic evidence for active neural compensation in the encoding of sensory event timing in support of the emergence of time awareness.

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“…Here, we demonstrate compelling evidence for discrete perceptual sampling in the somatosensory domain. Using magnetoencephalography (MEG) and a tactile temporal discrimination task in humans, we find that oscillatory alphaand low beta-band (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) Hz) cycles in primary somatosensory cortex represent neurophysiological correlates of discrete perceptual cycles. Our results agree with several theoretical concepts of discrete perceptual sampling and empirical evidence of perceptual cycles in the visual domain.…”

mentioning

confidence: 99%

Beta oscillations define discrete perceptual cycles in the somatosensory domain

Baumgarten

Schnitzler

Lange

2015

Proc. Natl. Acad. Sci. U.S.A.

105

116

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Whether seeing a movie, listening to a song, or feeling a breeze on the skin, we coherently experience these stimuli as continuous, seamless percepts. However, there are rare perceptual phenomena that argue against continuous perception but, instead, suggest discrete processing of sensory input. Empirical evidence supporting such a discrete mechanism, however, remains scarce and comes entirely from the visual domain. Here, we demonstrate compelling evidence for discrete perceptual sampling in the somatosensory domain. Using magnetoencephalography (MEG) and a tactile temporal discrimination task in humans, we find that oscillatory alphaand low beta-band (8-20 Hz) cycles in primary somatosensory cortex represent neurophysiological correlates of discrete perceptual cycles. Our results agree with several theoretical concepts of discrete perceptual sampling and empirical evidence of perceptual cycles in the visual domain. Critically, these results show that discrete perceptual cycles are not domain-specific, and thus restricted to the visual domain, but extend to the somatosensory domain.somatosensory perception | beta oscillations | MEG | oscillatory phase

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Conscious updating is a rhythmic process

Cited by 100 publications

References 33 publications

Oscillatory phase shapes syllable perception

Oscillatory phase shapes syllable perception

Encoding of event timing in the phase of neural oscillations

Beta oscillations define discrete perceptual cycles in the somatosensory domain

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