Biology subjects

Whitmarsh, S.

Publications and source records attributed to Whitmarsh, S..

3 recordsLinked to original sources

bioRxiv2020

Mindfulness meditation experience is associated with increased ability to monitor covert somatosensory attention

The distinguishing practice of mindfulness meditation is the intentional regulation of attention towards the present moment. Mindfulness meditation therefore emphasizes metacognitive functions, in particular the ability to monitor the attentional focus on a moment-by-moment basis. In this study we set out to test whether mindfulness meditation experience is associated with an increased ability to monitor moment-by-moment fluctuation in the attentional state. In response to auditory cues, participants maintained somatosensory attention to either their left or right hand. At random moments, trials were terminated by a probe sound to which participants reported their level of attention at that moment. MEG was recorded during the attention interval preceding probe onset. Using a beamformer approach, alpha activity in contralateral primary somatosensory regions was quantified. Alpha activity for self-reported high versus low attention trials was compared both within and between groups of either highly experienced experienced mindfulness meditators, novice meditators or meditation-naive participants (controls). As predicted, generally contralateral alpha power was associated with self-reported attention. Novice meditators (< 1000 h of meditation) showed temporal profiles similar to controls, displaying a correspondence between self-report and alpha power preceding probe onset. Expert meditators (>> 1000 h) showed a strikingly different pattern, however. Their self-reported attentional state corresponded with alpha power during a more extended time interval preceding those of controls and novice meditators. In addition, self-reported low attention trials showed a distinctive alpha suppression preceding probe onset, suggesting that the ability for moment-by-moment monitoring of the attentional state permitted greater attentional control.

neuroscience↗

bioRxiv2020

Distinct neural variables underlie subjective reports of attention

Attention is subjectively experienced as a unified cognitive effort. This unitary experience of attention contrasts with the diversity of neural and peripheral correlates of attention. While the effects of attention on stimulus-evoked responses, alpha oscillations and pupil diameter, are well-known the relationship between these indices and the subjective experience of attention, has not yet been assessed. Participants performed a sustained (10 s to 30 s) attention task in which rare (10%) targets were detected within continuous tactile stimulation (16 Hz). Trials were followed by attention ratings on an 8-point Likert scale. Steady-state evoked fields (SSEFs) in response to tactile stimulation, as measured by magnetoencephalography, provided an objective measure of sensory processing. Beamformer source analysis of somatosensory alpha power was used as a measure of cortical excitability, while pupillometry provided a peripheral index of arousal. Attention ratings correlated negatively with contralateral somatosensory alpha power, and positively with pupil diameter. The effect of pupil diameter on attention ratings extended into the following trial, reflecting a sustained aspect of attention related to vigilance. The effect of alpha power did not carry over to the next trial, and furthermore mediated the effect of pupil diameter on attention ratings. Variation in SSEF power reflected stimulus processing under the influence of alpha oscillations, but were not readily expressed through subjective ratings of attention. Together, our results show that both alpha power and pupil diameter are reflected in the subjective experience of attention, albeit on different time spans, while continuous stimulus processing might not be metacognitively accessible. 1 Significance StatementAttention is subjectively experienced as a unified cognitive effort, in contrast with a diversity of neural and peripheral measures shown to correlate with attention. We present the first comprehensive study on the complex inter-relationship between the most common bio-physiological indices of attention, and their association with the subjective experience of attention. We show that the subjective experience of attention correlates negatively with cortical alpha oscillations, and positively with pupil diameter. The latter reflected a sustained aspect of attention, spanning several tens of seconds, related to vigilance. Alpha power, representing cortical control, fluctuated faster and mediated the effect of pupil diameter on attention. Tactile steady-state power reflected stimulus processing, also under the influence of alpha oscillations, but did not contribute much to subjective ratings of attention.

neuroscience↗

bioRxiv2019

Micro-electrode in vivo signatures of human periventricular heterotopia

Periventricular nodular heterotopia (PNH) is a malformation of cortical development that frequently causes drug-resistant epilepsy. The epileptogenicity of ectopic neurons in PNH as well as their role in generating interictal and ictal activity is still a matter of debate. We report the first in vivo microelectrode recording of heterotopic neurons in humans. Highly consistent interictal patterns (IPs) were identified within the nodules: 1) Periodic Discharges PLUS Fast activity (PD+F), Sporadic discharges PLUS Fast activity (SD+F), and 3) epileptic spikes (ES). Neuronal firing rates were significantly modulated during all IPs, suggesting that multiple IPs were generated by the same local neuronal populations. Furthermore, firing rates closely followed IP morphologies. Among the different IPs, SD+FA pattern was found only in the three nodules that were actively involved in seizure generation, but was never observed in the nodule that did not take part in ictal discharges. On the contrary, PD+F and ES were identified in all nodules. Units that were modulated during the IPs were also found to participate in seizures, increasing their firing rate at seizure onset and maintaining an elevated rate during the seizures. Together, nodules in PNH are highly epileptogenic, and show several IPs that provide promising pathognomonic signatures of PNH. Furthermore, our results show that PNH nodules may well initiate seizures. HighlightsO_LIFirst in vivo microelectrode description of local epileptic activities in human PNH C_LIO_LIRecordings revealed multiple microscopic epileptic interictal patterns C_LIO_LIFiring rates of all detected units were significantly modulated during all interictal patterns C_LIO_LISeizures recruited the same units that are involved in interictal activity C_LI

pathology↗