Biology subjects

Jensen, O.

Publications and source records attributed to Jensen, O..

78 records · Page 5Linked to original sources

bioRxiv2017

Alpha/beta power compresses time in sub-second temporal judgments

While the perception of time plays a crucial role in our day-to-day functioning, the underlying neural mechanism of time processing on short time scales (~1s) remains to be elucidated. Recently, the power of beta oscillations (~20 Hz) has been suggested to play an important role in temporal processing. However, the paradigms supporting this view have often had confounds of working memory, as well as motor preparation. In the current EEG study, we set out to investigate if power of oscillatory activity would be involved in time perception without an explicit working memory component or confound of a motor response. Participants indicated through a button press whether the time between a tone and a visual stimulus was 1 or 1.5s.Critically, we focused on the differences in oscillatory activity in the alpha (~10 Hz) and beta (~20 Hz) ranges preceding correct versus incorrect temporal judgments. Behaviourally, we found participants made more errors on the long (1.5s) than on the short (1s) interval. In addition, we found that participants were fastest to correctly respond to a long interval. The onset of the tone induced a suppression of alpha and beta activity over occipital and parietal electrodes. In the long estimation intervals, this suppression was greater for correct than incorrect estimations. Interestingly, alpha and beta suppression allowed us to predict whether participants would judge the long interval correctly. For the short interval trials we did not find a significant difference in alpha or beta band activity for the correct and incorrect judgments. Taken together, our behavioural and EEG results suggest a multifaceted role of alpha and beta activity in the temporal estimation of sub- and supra-second intervals, where power increases seem to lead to temporal compression. Higher alpha and beta power resulted in shorter temporal judgments for sub-second intervals.\n\nHighlightsO_LITemporal judgments without motor confounds were studied with EEG.\nC_LIO_LIAlpha/beta activity differences for correct and incorrect temporal judgments.\nC_LIO_LISub-second intervals were judged as short when alpha/beta power was higher.\nC_LI

neuroscience↗

bioRxiv2017

Theta phase coordinated memory reactivation reoccurs in a slow-oscillatory rhythm during NREM sleep

It has been proposed that sleeps contribution to memory consolidation is to reactivate prior encoded information. To elucidate the neural mechanisms carrying reactivation-related mnemonic information, we investigated whether content-specific memory signatures associated with memory reactivation during wakefulness reoccur during subsequent sleep. We show that theta oscillations orchestrate the reactivation of memories, irrespective of the physiological state. Reactivation patterns during sleep autonomously re-emerged at a rate of 1 Hz, indicating a coordination by slow oscillatory activity.

neuroscience↗

bioRxiv2017

Alpha activity in the ventral and dorsal visual stream controls information flow during working memory

The electrophysiological mechanisms underlying working memory maintenance of information in the ventral and dorsal visual stream (VVS, DVS) remain elusive. Here we used electrocorticography recordings covering VVS, DVS and prefrontal cortex (PFC) in epilepsy patients while they were performing a delayed match-to-sample task. The experimental conditions (face identity, orientation) were designed to engage either the VVS or DVS. Alpha power was reduced in the VVS during maintenance of face identity and in the DVS during maintenance of spatial orientation of the very same stimuli. The phase of alpha oscillations modulated broadband high-frequency activity (BHA) in both regions. Interestingly, BHA occurred across broader alpha phase ranges when task-relevant information was maintained, putatively reflecting longer excitable \"duty cycles\". Our findings support a model in which the VVS and DVS are recruited by the PFC via selective reduction of alpha power. As a result, excitable duty cycles in the relevant area are extended.

neuroscience↗

bioRxiv2017

Neural entrainment determines the words we hear

Low-frequency neural entrainment to rhythmic input has been hypothesized as a canonical mechanism that shapes sensory perception in time. Neural entrainment is deemed particularly relevant for speech analysis, as it would contribute to the extraction of discrete linguistic elements from continuous acoustic signals. Yet, its causal influence in speech perception has been difficult to establish. Here, we provide evidence that oscillations build temporal predictions about the duration of speech tokens that directly influence perception. Using magnetoencephalography (MEG), we studied neural dynamics during listening to sentences that changed in speech rate. We observed neural entrainment to preceding speech rhythms persisting for several cycles after the change in rate. The sustained entrainment was associated with changes in the perceived duration of the last words vowel, resulting in the perception of words with radically different meanings. These findings support oscillatory models of speech processing, suggesting that neural oscillations actively shape speech perception.

neuroscience↗

bioRxiv2017

Serial representation of items during working memory maintenance at letter-selective cortical sites

We used intracranial recordings to study brain oscillations during a working memory task. To analyze sites involved in working memory, we focused on sites at which the elevation of the broadband gamma signal depended on which letter was presented. We tested a previously proposed model according to which different items are active at different phases of the theta cycle (in different gamma cycles within the theta cycle). Consistent with this model, the theta phase of letter-induced gamma elevation during maintenance reflected the order of letter presentation. These results suggest that working memory is organized by a theta-gamma code and provide strong support for the serial representation of items held in working memory.

neuroscience↗

bioRxiv2017

Saccades phase-locked to alpha oscillations in the occipital and medial temporal lobe enhance memory encoding

Efficient sampling of visual information requires a coordination of eye movements and ongoing brain oscillations. Using intracranial and MEG recordings, we show that saccades are locked to the phase of visual alpha oscillations, and that this coordination supports mnemonic encoding of visual scenes. Furthermore, parahippocampal and retrosplenial cortex involvement in this coordination reflects effective vision-to-memory mapping, highlighting the importance of neural oscillations for the interaction between visual and memory domains.

neuroscience↗