Biology subjects

Landau, A. N.

Publications and source records attributed to Landau, A. N..

21 records · Page 2Linked to original sources

bioRxiv2019

Sequences of Intonation Units Form a 1 Hz Rhythm

Studies of speech processing investigate the relationship between temporal structure in speech stimuli and neural activity. Despite clear evidence that the brain tracks speech at low frequencies (~1 Hz), it is not well understood what linguistic information gives rise to this rhythm. Here, we harness linguistic theory to draw attention to Intonation Units (IUs), a fundamental prosodic unit of human language, and characterize their temporal structure as captured in the speech envelope, an acoustic representation relevant to the neural processing of speech. IUs are defined by a specific pattern of syllable delivery, together with resets in pitch and articulatory force. Linguistic studies of spontaneous speech indicate that this prosodic segmentation paces new information in language use across diverse languages. Therefore, IUs provide a universal structural cue for the cognitive dynamics of speech production and comprehension. We study the relation between IUs and periodicities in the speech envelope, applying methods from investigations of neural synchronization. Our sample includes recordings from every-day speech contexts of over 100 speakers and six languages. We find that sequences of IUs form a consistent low-frequency rhythm and constitute a significant periodic cue within the speech envelope. Our findings allow to predict that IUs are utilized by the neural system when tracking speech, and the methods we introduce facilitate testing this prediction given physiological data.

neuroscience↗

bioRxiv2018

Where does time go when you blink?

Retinal input is frequently lost due to eye blinks, yet humans rarely notice these gaps in visual input. While previous studies focused on the psychophysical and neural correlates of diminished awareness to blinks, the impact of blinks on the perceived time of concurrent events is unknown. Here, we investigated whether the subjective sense of time is altered by spontaneous eye blinks, and how this link may inform mechanisms of time perception. We found that participants significantly underestimated the duration of a visual stimulus when a blink occurred during the stimulus. Importantly, this effect was not present when durations of an auditory stimulus were judged. These results point to a link between spontaneous blinks, previously demonstrated to induce suppression of activity in early visual cortex, and a compression of subjective time. The findings suggest that ongoing encoding within modality-specific sensory cortices, independent of conscious awareness, inform the subjective sense of time.

neuroscience↗

bioRxiv2016

The interaction of orientation-specific surround suppression and visual-spatial attention

Orientation selective surround suppression (OSSS) is a reduction in the perceived contrast of a stimulus, which occurs when a collinear grating is placed adjacent to the stimulus. Attention affects performance on many visual tasks, and we asked whether the perceptual effects of OSSS are mitigated through the allocation of voluntary visual-spatial attention. Participants were tested in a contrast discrimination task: at the beginning of each trial, one location on the screen was cued and a subsequent contrast judgment was then more likely (70%) to be performed in that location. Replicating previous results, we found that the point of subjective equality (PSE) was elevated for a collinear, relative to an orthogonal, surround. While the PSE was similar for validly and invalidly cued trials, the just noticeable difference (JND) was larger for invalid cue trials, and for collinear, relative to orthogonal surround, suggesting that while OSSS affects both perceived contrast and sensitivity, voluntary attention affects only perceptual sensitivity. In another experiment no informative cue was provided, and attention was distributed over the entire display. In this case, JND and PSE were shifted depending on the contrast of the distractor, suggesting that OSSS is affected by the allocation of visual-spatial attention, but only under conditions of distributed attention.

neuroscience↗