Biology subjects

Andersen, L. M.

Publications and source records attributed to Andersen, L. M..

11 recordsLinked to original sources

bioRxiv2026

The Temporal Constraints of the Cerebellum's Timekeeping

The cerebellum plays a central role in generating temporal predictions from past sensory regularities, yet the temporal boundaries of this predictive capacity remain unclear. Using magnetoencephalography (MEG), we investigated somatosensory and cerebellar responses to omissions within rhythmic somatosensory stimulation trains across six inter-stimulus intervals (ISIs) ranging from 0.5 to 5.5 seconds. We hypothesised that cerebellar prediction signals would follow a logistic decay pattern, remaining robust at short ISIs before declining beyond a 2-4-second temporal threshold. As a first step, we validated the omission paradigm by confirming the expected SI and SII response pattern to stimulations and the preservation of the SII response to omissions. Cerebellar source reconstruction revealed consistent beta band (14-30 Hz) responses to omissions peaking at 40-50 ms post-omission in right lobule VI, replicating previous findings. Critically, cerebellar activation to omissions was compatible with a logistic decay pattern with increasing ISI, with the inflexion point estimated within the hypothesised 2-4-second window, though precise localisation of this threshold warrants further investigation. Together, these findings establish empirical boundaries for cerebellar temporal prediction, suggesting that the cerebellum operates as a precise but duration-limited internal clock with implications for understanding the brains timing mechanisms and their functional consequences for perception.

neuroscience↗

bioRxiv2025

Motor prediction reduces beta-band power and enhances cerebellar-somatosensory connectivity before self-touch to enable its attenuation

Motor control theories suggest that the brain uses forward models to predict self-generated tactile input during voluntary movements, thereby reducing the intensity of reafferent tactile sensations. When ones own body is the target, this phenomenon is called self-touch attenuation. Although self-touch attenuation is well-documented, it remains unclear how prediction-related neural mechanisms drive attenuation before the self-touch input. We used magnetoencephalography (MEG) to examine the neural correlates of self-touch prediction. 24 human participants (12 female, 12 male) performed a self-touch, and two control tasks. In one control, they received externally generated touch without movement. In the other, the touch was triggered by the participants movement, but the hands were spatially misaligned. This manipulation is known to weaken attenuation despite identical tactile input, movement, and task demands, because the sensorimotor context reduces prediction of touch at that body site. Self-touch evoked weaker somatosensory activity (M50 component) than both control conditions. A psychophysics task mirrored the pattern of neural attenuation, as the perception of self-touch was attenuated compared to the two control conditions. To isolate predictive neural mechanisms from general movement-related activity, we subtracted activity from corresponding stimulus-absent trials. Comparing self-touch with misaligned touch allowed us to refine the signal specific to predictive processing in self-touch and revealed greater pre-stimulus beta-band desynchronization and increased cerebellar-to-somatosensory connectivity before self-touch compared to misaligned touch. Our results provide the first evidence of predictive neural activity that shapes the sensory consequences of self-touch, offering insights into the mechanisms through which predictive models modulate somatosensory processing. Significance statementThe brain is thought to predict and attenuate the sensory consequences of self-generated actions, but neural evidence for prediction before sensation has been limited. Using magnetoencephalography, we show that self-touch attenuation is preceded by beta-band desynchronization and increased directed connectivity from the cerebellum to the primary somatosensory cortex. These effects cannot be attributed to movement, as they were reduced in a control condition with similar motor output but lower congruence between the action and tactile consequence, suggesting spatially specific predictive processing. Our study provides the first neural evidence of cerebellar influence on cortical sensory areas before self-touch. These pre-stimulus effects support forward models of sensorimotor control and shed new light on how the brain anticipates and modulates upcoming sensory input.

neuroscience↗

bioRxiv2023

Detection of threshold-level stimuli modulated by temporal predictions of the cerebellum

0 AbstractThe cerebellum has the reputation of being a primitive part of the brain that mostly is involved in motor coordination and motor control. Older lesion studies and more recent electrophysiological studies have, however, indicated that it is involved in temporal perception and temporal expectation-building. An outstanding question is whether this temporal expectation-building cerebellar activity has functional relevance. In this study, we collected magnetoencephalographic data from 30 healthy participants performing a detection task on at-threshold stimulation that was presented at the end of a sequence of temporally regular or irregular above-threshold stimulation. We found that behavioural detection rates depended on the degree of irregularity in the sequence preceding it. We also found cerebellar responses evoked by above-threshold and at-threshold stimulation. The evoked responses to at-threshold stimulation differed significantly, depending on whether it was preceded by a regular or an irregular sequence. Finally, we found that detection performance across participants correlated significantly with the differences in cerebellar evoked responses to the at-threshold stimulation, demonstrating the functional relevance of cerebellar activity in sensory expectation-building. We furthermore found evidence of thalamic involvement, as indicated by responses in the beta band (14-30 Hz) and by significant modulations of cerebello-thalamic connectivity by the regularity of the sequence and the kind of stimulation terminating the sequence. These results provide evidence that the temporal expectation-building mechanism of the cerebellum, what we and others have called an internal clock, shows functional relevance by regulating behaviour and performance in sensory action that requires acting and integrating evidence over precise time-scales.

neuroscience↗

bioRxiv2022

Identifying Content-Invariant Neural Signatures of Phenomenal Magnitude

Some conscious experiences are more vivid than others. Although perceptual vividness is a key component of human consciousness, how variation in this magnitude property is registered by the human brain is unknown. A striking feature of magnitudes in other psychological domains, such as number or reward, is the existence of neural magnitude codes that are independent from sensory contents. To test whether perceptual vividness similarly covaries with neural codes that are invariant to sensory content, we reanalysed existing MEG and fMRI data from two distinct studies, quantifying perceptual vividness via subjective ratings of awareness and visibility. Using representational similarity and decoding analyses, we find evidence for the existence of content-invariant neural codes for perceptual vividness distributed across visual, parietal, and frontal cortices. Our findings are consistent with a hypothesis that the subjective vividness of conscious experience is supported by neural signatures similar to magnitude codes in other cognitive domains. Significance StatementThe vividness of conscious experience varies across different stimuli and contexts. Despite being a fundamental feature of conscious awareness, exactly how perceptual vividness is encoded in the human brain remains unclear. Neural codes underpinning magnitude in reward and numerosity domains have been shown to be unchanging as stimulus identity varies. Here, we test whether components of neural activity covarying with the magnitude of perceptual vividness are similarly independent of perceptual content in analyses of MEG and fMRI data. We find dynamic, content-invariant neural signatures of vividness in visual, parietal, and frontal cortices. Our findings introduce the surprising notion that neural signatures of conscious experience might follow similar coding principles to those found for magnitude properties of entirely different cognitive domains.

neuroscience↗

bioRxiv2020

The cerebellar clock: predicting and timing somatosensory touch

0The prediction of sensory feedback is known to involve the cerebellum, but its precise nature and timing have remained unclear due to the scarcity of time-sensitive cerebellar neuroimaging studies. We here, using magnetoencephalography in human participants, investigated the working hypothesis that one function of the cerebellum is to predict exactly when rhythmic stimuli are expected to impinge on sensory receptors. We compared the cerebellums response between somatosensory omissions embedded in perfectly rhythmic versus jittered trains of stimulation. At the precise moment that an omitted stimulus would have appeared, the cerebellum exhibited a beta band (14-30 Hz) response that was stronger when preceded by a perfectly rhythmic sequence. Meanwhile, the rhythm of new stimulation sequences induced theta band (4-7 Hz) activity in the cerebellum. Our results provide evidence that the cerebellum acts as a clock that entrains to rhythmic stimuli, likely for the purpose of detecting any deviations from that rhythm.

neuroscience↗

bioRxiv2019

Attentional Modulation of the Auditory Steady-State Response across the Cortex

Selective auditory attention allows us to focus on relevant sounds within noisy or complex auditory environments, and is essential for the processing of speech and music. The auditory steady-state response (ASSR) has been proposed as a neural measure for tracking selective auditory attention, even within continuous and complex soundscapes. However, the current literature is inconsistent on how the ASSR is influenced by selective attention, with findings based primarily on attention being directed to either ear rather than to sound content. In this experiment, a mixture of melody streams was presented to both ears identically (diotically) as we examined if selective auditory attention to sound content influences the ASSR. Using magnetoencephalography (MEG), we assessed the stream-specific ASSRs from three frequency-tagged melody streams when attention was directed between each melody stream, based on their respective pitch and timing. Our main results showed that selective attention enhances the ASSR power of an attended melody stream by 15 % at a general sensor level. This ability to readily capture attentional changes in a stimuli-precise manner makes the ASSR a useful tool for studying selective auditory attention, especially in complex auditory environments. Furthermore, as a secondary aim, we explored the distribution of cortical ASSR sources and their respective attentional modulation. A novel finding using distributed source modelling revealed that the ASSR is modulated by attention in many areas across the cortex, with frontal regions experiencing the strongest enhancement of up to ~ 80 %. ASSRs in the temporal and parietal cortices were enhanced by approximately 20 - 25 %. For future studies, this work can serve as a template to narrow-down possible sites of ASSR attentional modulation for further investigation.

neuroscience↗

bioRxiv2019

Detection of interictal epileptiform discharges:A comparison of on-scalp MEG and conventional MEGmeasurements

Magnetoencephalography (MEG) is an important part of epilepsy evaluations because of its unsurpassed ability to detect interictal epileptiform discharges (IEDs). This ability may be improved by next-generation MEG sensors, where sensors are placed directly on the scalp instead of in a fixed-size helmet, as in todays conventional MEG systems. In order to investigate the usefulness of on-scalp MEG measurements we performed the first-ever measurements of on-scalp MEG on an epilepsy patient. The measurement was conducted as a benchmarking study, with special focus on IED detection. An on-scalp high-temperature SQUID system was utilized alongside a conventional low-temperature "in-helmet" SQUID system. EEG was co-registered during both recordings. Visual inspection of IEDs in the raw on-scalp MEG data was unfeasible why a novel machine learning-based IED-detection algorithm was developed to guide IED detection in the on-scalp MEG data. A total of 24 IEDs were identified visually from the conventional in-helmet MEG session (of these, 16 were also seen in the EEG data; eight were detected only by MEG). The on-scalp MEG data contained a total of 47 probable IEDs of which 16 IEDs were co-registered by the EEG, and 31 IEDs were on-scalp MEG-unique IEDs found by the IED detection algorithm. We present a successful benchmarking study where on-scalp MEG are compared to conventional in-helmet MEG in a temporal lobe epilepsy patient. Our results demonstrate that on-scalp MEG measurements are feasible on epilepsy patients, and indicate that on-scalp MEG might capture IEDs not seen by other non-invasive modalities.

neuroscience↗

bioRxiv2019

On-scalp MEG SQUIDs are sensitive to early somatosensory activity unseen by conventional MEG

Magnetoencephalography (MEG) has a unique capacity to resolve the spatio-temporal development of brain activity from non-invasive measurements. Conventional MEG, however, relies on sensors that sample from a distance (20-40 mm) to the head due to thermal insulation requirements (the MEG sensors function at 4 K in a helmet). A gain in signal strength and spatial resolution may be achieved if sensors are moved closer to the head. Here, we report a study comparing measurements from a seven-channel on-scalp SQUID MEG system to those from a conventional (in-helmet) SQUID MEG system.\n\nWe compared spatio-temporal resolution between on-scalp and conventional MEG by comparing the discrimination accuracy for neural activity patterns resulting from stimulating five different phalanges of the right hand. Because of proximity and sensor density differences between on-scalp and conventional MEG, we hypothesized that on-scalp MEG would allow for a more high-resolved assessment of these activity patterns, and therefore also a better classification performance in discriminating between neural activations from the different phalanges.\n\nWe observed that on-scalp MEG provided better classification performance during an early post-stimulus period (15-30 ms). This corresponded to electroencephalographic (EEG) response components N16 and P23, and was an unexpected observation as these components are usually not observed in conventional MEG. They indicate that on-scalp MEG opens up for a richer registration of the cortical signal, allowing for sensitivity to what are potentially sources in the thalamo-cortical radiation and to quasi-radial sources.\n\nWe had originally expected that on-scalp MEG would provide better classification accuracy based on activity in proximity to the P60m component compared to conventional MEG. This component indeed allowed for the best classification performance for both MEG systems (60-75%, chance 50%). However, we did not find that on-scalp MEG allowed for better classification than conventional MEG at this latency. We believe this may be due to the limited sensor coverage in the recording, in combination with our strategy for positioning the on-scalp MEG sensors. We discuss how sensor density and coverage as well as between-phalange source field dissimilarities may influence our hypothesis testing, which we believe to be useful for future benchmarking measurements.

neuroscience↗

bioRxiv2019

Sensor localization using magnetic dipole-like coils: A method for highly accurate co-registration in on-scalp MEG

Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor array and the anatomical structure of the measured individuals head. In conventional MEG, positions and orientations of the sensors relative to each other are fixed and known beforehand, requiring only localization of the head relative to the sensor array. Since the sensors in on-scalp MEG are positioned on the scalp, locations of the individual sensors depend on the subjects head shape and size. The positions and orientations of on-scalp sensors must therefore be measured at every recording. This can be achieved by inverting conventional head localization, localizing the sensors relative to the head - rather than the other way around.\n\nIn this study we present a practical method for localizing sensors using magnetic dipole-like coils attached to the subjects head. We implement and evaluate the method in a set of on-scalp MEG recordings using a 7-channel on-scalp MEG system based on high critical temperature superconducting quantum interference devices (high-Tc SQUIDs). The method provides accurate estimates of individual sensor positions and orientations with short averaging time ([≤] 2 mm and < 3 degrees, respectively, with 1-second averaging), enabling continuous sensor localization. Calibrating and jointly localizing the sensor array can further improve the localization accuracy (< 1 mm and < 2.5 degrees, respectively, with 1-second coil recordings).\n\nWe demonstrate source localization of on-scalp recorded somatosensory evoked activity based on co-registration with our method. Equivalent current dipole fits of the evoked responses corresponded well (within 5.3 mm) with those based on a commercial, whole-head MEG system.

neuroscience↗

bioRxiv2019

Postdoc X-ray in Europe 2017: work conditions, productivity, institutional support and career outlooks

1.Executive SummaryThis survey and data analysis were conducted by the European Network of Postdoctoral Associations (ENPA) with the aim of assessing the current research and work conditions, aspirations and support received by postdoctoral researchers working in Europe. The Results section is structured into three main parts. The first one describes the study sample of European postdoctoral researchers, including participants demographics, funding sources and income, research outputs, and teaching opportunities. The second section focuses on their professional aspirations and institutional support provided. The third part describes the level of engagement of postdoctoral researchers and their institutions in working towards better research conditions and career development, and what initiatives are emerging within this community. Our Conclusions section pulls together this comprehensive analysis, highlighting some of the most concerning issues currently affecting postdoctoral researchers in Europe. We also make a number of recommendations that would significantly improve the career expectations and aspirations of postdoctoral researchers. These are listed below. Conclusions and recommendationsO_LILonger postdoctoral periods in Southern Europe despite higher publication metrics Recommendation Institutions in Southern Europe should develop clear criteria to support postdoctoral researchers career progression. C_LIO_LISouthern and Eastern Europe pay the lowest salaries and have the lowest number of foreign postdoctoral researchers Recommendation The salary differences across European countries should be addressed as this could be a barrier to mobility and knowledge exchange from higher to lower pay regions. C_LIO_LILack of access to funding is a significant concern of postdoctoral researchers Recommendation Discrepancies in access to funding should be minimized across the different European areas. C_LIO_LIPostdoctoral researchers in Europe work longer hours than required by contract Recommendation The culture of overwork in the research environment should be addressed in order to protect researchers against the risks associated with long hours at work. C_LIO_LIThe majority of full-time postdoctoral work contracts includes an exclusivity clause Recommendation Inclusion of exclusivity clauses in contracts for postdoctoral researchers should be optional in order to allow them to enhance their employability outside academia. C_LIO_LIPostdoctoral researchers career development is poorly supported by their institutions Recommendation Postdoctoral researchers career prospects and career management should be much more supported by institutions in coordination with postdoctoral associations. C_LIO_LILack of postdoctoral representation in governance is linked to unclear institutional duties and rights Recommendation Institutional governance bodies should include postdoctoral researcher representatives. This would ensure that the views of this vital staff group are heard, as well as making postdoctoral researchers feel more engaged with their own institutions. A flexible and proactive communication strategy at the institution and research group level should be developed, taking into account the sometimes transient nature of postdoctoral researchers posts. C_LIO_LIResearchers show higher engagement with their local postdoctoral associations than with workers unions Recommendation Postdoctoral associations are an essential way to advocate for postdoctoral researchers at the governance level. Institutions should engage with, promote and support the work of postdoctoral associations. C_LI

scientific communication and education↗

bioRxiv2018

Somatosensory responses to nothing: an MEG study of expectations during omission of tactile stimulations

The brain builds up expectations to future events based on the patterns of past events. This function has been studied extensively in the auditory and visual domains using various oddball paradigms, but only little exploration of this phenomenon has been done in the somatosensory domain. In this study, we explore how expectations of somatosensory stimulations are established and expressed in neural activity as measured with magnetoencephalography. Using tactile stimulations to the index finger, we compared conditions with actual stimulation to conditions with omitted stimulations, both of which were either expected or unexpected.\n\nOur results show that when a stimulation is expected but omitted, a time-locked response occurs [~]135 ms subsequent to the expected stimulation. This somatosensory response to \"nothing\" was source localized to the secondary somatosensory cortex and to the insula. This provides novel evidence of the capability of the brain of millisecond time-keeping of somatosensory patterns across intervals of 3000 ms.\n\nOur results also show that when stimuli are repeated and expectations are established, there is associated activity in the theta and beta bands. These theta and beta band expressions of expectation were localized to the primary somatosensory area, inferior parietal cortex and cerebellum. Furthermore, there was gamma band activity in the right insula for the first stimulation after an omission, which indicates the detection of a new stimulation event after an expected pattern has been broken.\n\nFinally, our results show that cerebellum play a crucial role in predicting upcoming stimulation and in predicting when stimulation may begin again.

neuroscience↗