Left parietal tACS at alpha frequency induces a shift of visuospatial attention

Background Voluntary shifts of visuospatial attention are associated with a lateralization of parieto-occipital alpha power (7-13Hz), i.e. higher power in the hemisphere ipsilateral and lower power contralateral to the locus of attention. Recent noninvasive neuromodulation studies demonstrated that alpha power can be experimentally increased using transcranial alternating current stimulation (tACS). Objective/Hypothesis We hypothesized that tACS at alpha frequency over the left parietal cortex induces shifts of attention to the left hemifield. However, spatial attention shifts not only occur voluntarily (endogenous/ top-down), but also stimulus-driven (exogenous/ bottom-up). To study the task-specificity of the potential effects of tACS on attentional processes, we administered three conceptually different spatial attention tasks. Methods 36 healthy volunteers were recruited from an academic environment. In two separate sessions, we applied either high-density tACS at 10Hz, or sham tACS, for 35–40 minutes to their left parietal cortex. We systematically compared performance on endogenous attention, exogenous attention, and stimulus detection tasks. Results In the endogenous attention task, a greater leftward bias in reaction times was induced during left parietal 10Hz tACS as compared to sham. There were no stimulation effects in either the exogenous attention or the stimulus detection task. Conclusion The study demonstrates that high-density tACS at 10Hz can be used to modulate visuospatial attention performance. The tACS effect is task-specific, indicating that not all forms of attention are equally susceptible to the stimulation

Using a runway paradigm to assess the relative strength of rats' motivations for enrichment objects

Laboratory animals should be provided with enrichment objects in their cages; however, it is first necessary to test whether the proposed enrichment objects provide benefits that increase the animals’ welfare. The two main paradigms currently used to assess proposed enrichment objects are the choice test, which is limited to determining relative frequency of choice, and consumer demand studies, which can indicate the strength of a preference but are complex to design. Here, we propose a third methodology: a runway paradigm, which can be used to assess the strength of an animal’s motivation for enrichment objects, is simpler to use than consumer demand studies, and is faster to complete than typical choice tests. Time spent with objects in a standard choice test was used to rank several enrichment objects in order to compare with the ranking found in our runway paradigm. The rats ran significantly more times, ran faster, and interacted longer with objects with which they had previously spent the most time. It was concluded that this simple methodology is suitable for measuring rats’ motivation to reach enrichment objects. This can be used to assess the preference for different types of enrichment objects or to measure reward system processes

Effects of Synaptic and Myelin Plasticity on Learning in a Network of Kuramoto Phase Oscillators

Models of learning typically focus on synaptic plasticity. However, learning is the result of both synaptic and myelin plasticity. Specifically, synaptic changes often co-occur and interact with myelin changes, leading to complex dynamic interactions between these processes. Here, we investigate the implications of these interactions for the coupling behavior of a system of Kuramoto oscillators. To that end, we construct a fully connected, one-dimensional ring network of phase oscillators whose coupling strength (reflecting synaptic strength) as well as conduction velocity (reflecting myelination) are each regulated by a Hebbian learning rule. We evaluate the behavior of the system in terms of structural (pairwise connection strength and conduction velocity) and functional connectivity (local and global synchronization behavior). We find that for conditions in which a system limited to synaptic plasticity develops two distinct clusters both structurally and functionally, additional adaptive myelination allows for functional communication across these structural clusters. Hence, dynamic conduction velocity permits the functional integration of structurally segregated clusters. Our results confirm that network states following learning may be different when myelin plasticity is considered in addition to synaptic plasticity, pointing towards the relevance of integrating both factors in computational models of learning.Comment: 39 pages, 15 figures This work is submitted in Chaos: An Interdisciplinary Journal of Nonlinear Scienc

Parietal but not temporoparietal alpha-tACS modulates endogenous visuospatial attention

Visuospatial attention can either be voluntarily directed (endogenous/top-down attention) or automatically triggered (exogenous/bottom-up attention). Recent research showed that dorsal parietal transcranial alternating current stimulation (tACS) at alpha frequency modulates the spatial attentional bias in an endogenous but not in an exogenous visuospatial attention task. Yet, the reason for this task-specificity remains unexplored. Here, we tested whether this dissociation relates to the proposed differential role of the dorsal attention network (DAN) and ventral attention network (VAN) in endogenous and exogenous attention processes respectively. To that aim, we targeted the left and right dorsal parietal node of the DAN, as well as the left and right ventral temporoparietal node of the VAN using tACS at the individual alpha frequency. Every participant completed all four stimulation conditions and a sham condition in five separate sessions. During tACS, we assessed the behavioral visuospatial attention bias via an endogenous and exogenous visuospatial attention task. Additionally, we measured offline alpha power immediately before and after tACS using electroencephalography (EEG). The behavioral data revealed an effect of tACS on the endogenous but not exogenous attention bias, with a greater leftward bias during (sham-corrected) left than right hemispheric stimulation. In line with our hypothesis, this effect was brain area-specific, i.e., present for dorsal parietal but not ventral temporoparietal tACS. However, contrary to our expectations, there was no effect of ventral temporoparietal tACS on the exogenous visuospatial attention bias. Hence, no double dissociation between the two targeted attention networks. There was no effect of either tACS condition on offline alpha power. Our behavioral data reveal that dorsal parietal but not ventral temporoparietal alpha oscillations steer endogenous visuospatial attention. This brain-area specific tACS effect matches the previously proposed dissociation between the DAN and VAN and, by showing that the spatial attention bias effect does not generalize to any lateral posterior tACS montage, renders lateral cutaneous and retinal effects for the spatial attention bias in the dorsal parietal condition unlikely. Yet the absence of tACS effects on the exogenous attention task suggests that ventral temporoparietal alpha oscillations are not functionally relevant for exogenous visuospatial attention. We discuss the potential implications of this finding in the context of an emerging theory on the role of the ventral temporoparietal node

The rhythm of life: the perfect rhythm of morse code

Morse code is a unique exemplar of the inherent complexities of rhythm. Learning Morse code in wartime presented challenges to expedite skill acquisition. This thesis explored the strategies used to teach and learn Morse code in the second World War and investigated the resourceful techniques used by the WRANS in an empirical study. The first study investigated the teaching and learning strategies of wartime telegraphists to learn Morse code. Five WRANS described a series of techniques to learn Morse code, including rote learning and repetition, visualisation and pattern recognition, intoning and mnemonics, and music. Music provided effective training for the fundamental teaching and learning of Morse code by matching the rhythmical properties of Morse code to music. Music equipped Morse code operators with a unique approach to Morse code instruction. Learning Morse code with music was described as a way of making sense of the ‘rhythm’ and ‘shape’ of the Morse code letters and proved an invaluable aid to learning and teaching Morse code. The second study examined the effectiveness of learning Morse code with the aid of music. Novices formed two groups, Control Group (no music aid) and Music Group (with music aid). Results confirmed the effectiveness of music training in three Morse code letters, Q V, and A in two experiments, the first with known Morse code letters (Q V A) and the second with unknown letters. The Music Group accurately identified 90% of known and unknown Morse code letters compared to the Control Group who identified less then 50% of known and unknown Morse code letters. This thesis explored the transferable attributes of rhythm perception in music as a teaching and learning mechanism for Morse code. There is extensive research on the complex learning and retention of Morse code but the studies in this thesis have indicated that the ground-breaking wartime strategy of music and Morse code is a powerful duo. The investigation of learning and teaching strategies of the WRANS showed that musical rhythm influenced the skill acquisition of Morse code and the perceptual test suggests that current work in rhythm perception extends beyond music pedagogy and has further implications for all cognitive function

Pathways for Energy Transfer in the Core Light-Harvesting Complexes CP43 and CP47 of Photosystem II

AbstractThe pigment-protein complexes CP43 and CP47 transfer excitation energy from the peripheral antenna of photosystem II toward the photochemical reaction center. We measured the excitation dynamics of the chlorophylls in isolated CP43 and CP47 complexes at 77K by time-resolved absorbance-difference and fluorescence spectroscopy. The spectral relaxation appeared to occur with rates of 0.2–0.4ps and 2–3ps in both complexes, whereas an additional relaxation of 17ps was observed only in CP47. Using the 3.8-Å crystal structure of the photosystem II core complex from Synechococcus elongatus (A. Zouni, H.-T. Witt, J. Kern, P. Fromme, N. Krauss, W. Saenger, and P. Orth, 2001, Nature, 409:739–743), excitation energy transfer kinetics were calculated and a Monte Carlo simulation of the absorption spectra was performed. In both complexes, the rate of 0.2–0.4ps can be ascribed to excitation energy transfer within a layer of chlorophylls near the stromal side of the membrane, and the slower 2–3-ps process to excitation energy transfer to the calculated lowest excitonic state. We conclude that excitation energy transfer within CP43 and CP47 is fast and does not contribute significantly to the well-known slow trapping of excitation energy in photosystem II

A nationwide study on cancer recurrences, second primary tumours, distant metastases and survival after treatment for primary head and neck cancer in the Netherlands

Introduction: There is no consensus on the optimal duration of post-treatment follow-up after head and neck cancer (HNC). To generate site-specific input for follow-up guidelines, this study describes the incidence and timing of manifestations of disease during five years of follow-up. Methods: All patients diagnosed with HNC in the Netherlands in 2015 were selected from the Netherlands Cancer Registry. The follow-up events local recurrence (LR), regional recurrence (RR), second primary tumour (SPT), distant metastasis (DM) and death were studied per follow-up-year. The cumulative incidence of these events was calculated using competing risk analyses, with LR, RR and SPT of the head and neck (SPHNC) as events and SPT outside the head-neck (SPOHN), DM and death as competing events. Analyses were performed for oral cavity-, oropharynx-, larynx- and hypopharynx squamous cell carcinoma (SCC), and all HNC patients. Results: The 1-, 1.5-, and 2-year cumulative incidence of an event (LR, RR, SPHNC) were 10% (95%CI 8–13), 12% (95%CI 10–15), and 13% (95%CI 10–16) for oral cavity SCC; 6% (95%CI 4–9), 10% (95%CI 7–14), and 11% (95%CI 8–15) for oropharynx SCC; 7% (95%CI 5–10), 11% (95%CI 9–15), and 13% (95%CI 10–16) for larynx SCC and 11% (95%CI 6–19), 19% (95%CI 12–27), and 19% (95%CI 12–27) for hypopharynx SCC. Conclusions: One year of follow-up for oral cavity SCC, and 1.5 years for oropharynx-, larynx-, and hypopharynx SCC suffices for the goal of detecting disease manifestations after treatment. More research into other aspects of follow-up care should be performed to determine the optimal follow-up regimen.</p