Auditory cortical tuning to statistical regularities in phonology

Objective: Ample behavioral evidence suggests that distributional properties of the language environment influence the processing of speech. Yet, how these characteristics are reflected in neural processes remains largely unknown. The present ERP study investigates neurophysiological correlates of phonotactic probability: the distributional frequency of phoneme combinations. Methods: We employed an ERP measure indicative of experience-dependent auditory memory traces, the mismatch negativity (MMN). We presented pairs of non-words that differed by the degree of phonotactic probability in a codified passive oddball design that minimizes the contribution of acoustic processes. Results: In Experiment 1 the non-word with high phonotactic probability (notsel) elicited a significantly enhanced MMN as compared to the non-word with low phonotactic probability (notkel). In Experiment 2 this finding was replicated with a non-word pair with a smaller acoustic difference (notsel–notfel). An MMN enhancement was not observed in a third acoustic control experiment with stimuli having comparable phonotactic probability (so–fo). Conclusions: Our data suggest that auditory cortical responses to phoneme clusters are modulated by statistical regularities of phoneme combinations. Significance: This study indicates that the language environment is relevant in shaping the neural processing of speech. Furthermore, it provides a potentially useful design for investigating implicit phonological processing in children with anomalous language functions like dyslexia

Why knot Calidris canutus take medium-sized Macoma balthica when six prey species are available

We quantified the prey selection and intake rate of a wading bird, knot Calidris canutus, when 6 different, intertidal prey species, the mud snail Peringia ulvae and the bivalves Macoma balthica, Cerastoderma edule, Mya arenaria, Scrobicularia plana and Mytilus edulis, were abundant. Knot usually search for food by randomly probing into the mud. Prey selection may be described by 5 rules: (1) Prey are not ingestible by knot if the circumference is more than 30 mm. (2) Prey are not accessible to knot when they lie buried deeper than 2 to 3 cm. (3) The probability of a prey organism being detected depends on its surface area, measured in the horizontal plane. (4) Prey are ignored when they are unprofitable, i.e. when the rate of intake while handling the prey is below the current overall average intake rate during feeding. (5) Knot prefer thin-shelled to thick-shelled prey species, possibly because a high inorganic content has an inhibitory effect on the rate at which energy can be extracted from the food. The first rule of ingestion is set by the gape width, and is therefore invariable. The fraction of the prey which is accessible varies according to the probing depth of the bird. The lower size threshold of prey taken is determined by the profitability rule and so varies according to the current feeding rate of knot. Unfortunately for knot, the majority of the preferred thin-shelled prey live out of reach of the bill, whereas the thick-shelled species live at the surface. Medium-sized Macoma balthica is the best compromise available in the 6-species mix

Annual and seasonal-variation in the food-supply harvestable by knot Calidris-canutus staging in the Wadden Sea in late summer

The biomass of the macrobenthic animals living in intertidal flats of the Wadden Sea varies annually and seasonally. However, the variation in prey biomass harvestable by wading birds such as knot Calidris canutus, which feed mainly on the middle range of their prey size classes, is even larger. The majority of first-year Cerastoderma edule, Mya arenaria or Mytilus edulis are too small to be profitable as prey for knot. Yet, by the end of the subsequent growing season, these same prey are too large to be ingested and/or live at a depth that puts them out of reach of the birds' bills. Macoma balthica is a major prey for knot, because (1) its annual spatfall is less erratic than in the other bivalve species, and (2) it grows more slowly, and each cohort is therefore available as food for knot for at least 3 yr. Knot feed in flocks which roam over the feeding area, but they are more often observed in food-rich than in food-poor areas, A similar relationship between bird and food densities was found in one locality, when the annual numbers of knot were compared with the yearly variation in food supply. Since the numbers of knot in the whole area were the same over many years, the birds were apparently able to find other feeding areas when the local food supply was low, i.e. the food supply harvestable by knot (prey not too small, not too large and not too deep) was less than about 4 g ash-free dry weight m-2. Knot arrive in the study area at the end of July and leave after only a few weeks en route to Africa. They depart before d serious decline in the harvestable prey biomass takes place, which results from a decrease in the body condition of individual prey and an increase in the fraction of the prey which burrows out of the reach of the knot's bill

Visual word form processing deficits driven by severity of reading impairments in children with developmental dyslexia

The visual word form area (VWFA) in the left ventral occipito-temporal (vOT) cortex is key to fluent reading in children and adults. Diminished VWFA activation during print processing tasks is a common finding in subjects with severe reading problems. Here, we report fMRI data from a multicentre study with 140 children in primary school (7.9-12.2 years;55 children with dyslexia, 73 typical readers, 12 intermediate readers). All performed a semantic task on visually presented words and a matched control task on symbol strings. With this large group of children, including the entire spectrum from severely impaired to highly fluent readers, we aimed to clarify the association of reading fluency and left vOT activation during visual word processing. The results of this study confirm reduced word-sensitive activation within the left vOT in children with dyslexia. Interestingly, the association of reading skills and left vOT activation was especially strong and spatially extended in children with dyslexia. Thus, deficits in basic visual word form processing increase with the severity of reading disability but seem only weakly associated with fluency within the typical reading range suggesting a linear dependence of reading scores with VFWA activation only in the poorest readers