Callaghan, E. | Search bioRxiv

bioRxiv2018

Flexible allocation of attention in time or space across the life span: Theta and alpha oscillatory signatures of age-related decline and compensation as revealed by MEG

In our recent behavioural research (Callaghan et al., 2017), we reported age-related changes in the costs of switching between from a temporal (rapid serial visual presentation) to a spatial (visual search) attention task. Using magnetoencephalography, we have now compared the neural signatures of attention refocusing between three age groups (19-30, 40-49 and 60+ years) and found differences in task-related modulation and cortical localisation of alpha and theta oscillations. Efficient, faster switching between the temporal and spatial attention tasks in the youngest group compared to both older groups was reflected in parietal theta effects that were significantly reduced in the older groups. Residual parietal theta activity in older individuals was, however, beneficial to attentional switching, and could reflect the preservation of attention mechanisms. Difficulties in refocusing attention in the older and middle-aged adults (slowed response times) were accompanied by reduced theta power modulation in occipital and cerebellar regions. In addition to this posterior theta deficit, older and middle-aged adults presented with increased recruitment of frontal (both groups) and temporal (older group) areas. Theta oscillations therefore demonstrated a posterior to anterior processing shift, which may reflect the engagement of alternative strategies in older- and middle-age, such as top-down attentional control in an attempt to compensate for posterior processing deficits. Additional frontal theta recruitment indeed appeared to be beneficial for faster performance, as reflected by correlational analysis. Temporal theta (in older-age), however, did not correlate with performance, but could reflect strategies unrelated to speeded performance (e.g. silent vocalisation to maintain task goals). Alpha oscillations did not significantly correlate with task performance, possibly reflecting decreased neural precision or de-differentiation, but require further investigation.

neuroscience↗

bioRxiv2018

Taxonomic revision of Leopold and Rudolf Blaschka Glass Models of Invertebrates 1888 Catalogue, with correction of authorities

The glass models of invertebrates crafted by Leopold and Rudolf Blaschka were made between 1863 and 1889. Production ceased when the glassmakers turned their attention to what is now known as the Ware Collection of Blaschka Glass Models of Plants, created for the Harvard Museum of Natural History. Nearly 130 years have passed since their last published catalogue of species in 1888 and the nomenclature they applied is now a confusing mix that includes many junior synonyms and unavailable names. This is an issue for many museums and universities which owns Blaschka models as uncertain identifications may compromised interpretation of this rediscovered legacy. Nowadays, many museums and universities hold collections of those glass invertebrates but misspelled, mislabelled or simply apply the century old taxonomy of 1888. Here, we provide a valuable resource for curators and enthusiasts alike. We studied and updated the final catalogue 1888 from the Blaschkas Dresden-based workshop. We first focused on major taxonomical changes from taxa to species, as well as on an analysis of the acknowledged authorities. We found that only 35.3% of the models retain their original names, while 3.7% lack any known synonym and their identity remains open to interpretation. Finally, two of the authorities listed in the catalogue, Ernst Haeckel and Philip Henry Gosse, were incorrectly acknowledged for an extensive range of models. This study is the first of its kind on the Blaschka collection, and it will help in the identification and naming of Blaschka models worldwide.

scientific communication and education↗