bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of auditory cortices in the retrieval of single‐trial auditory–visual object memories
Authors: Matusz Pawel J. , Thelen Antonia , Amrein Sarah , Geiser Eveline , Anken Jacques , Murray Micah M. 
Published: March 2015

AbstractSingle‐trial encounters with multisensory stimuli affect both memory performance and early‐latency brain responses to visual stimuli. Whether and how auditory cortices support memory processes based on single‐trial multisensory learning is unknown and may differ qualitatively and quantitatively from comparable processes within visual cortices due to purported differences in memory capacities across the senses. We recorded event‐related potentials (ERPs) as healthy adults (n = 18) performed a continuous recognition task in the auditory modality, discriminating initial (new) from repeated (old) sounds of environmental objects. Initial presentations were either unisensory or multisensory; the latter entailed synchronous presentation of a semantically congruent or a meaningless image. Repeated presentations were exclusively auditory, thus differing only according to the context in which the sound was initially encountered. Discrimination abilities (indexed by d’) were increased for repeated sounds that were initially encountered with a semantically congruent image versus sounds initially encountered with either a meaningless or no image. Analyses of ERPs within an electrical neuroimaging framework revealed that early stages of auditory processing of repeated sounds were affected by prior single‐trial multisensory contexts. These effects followed from significantly reduced activity within a distributed network, including the right superior temporal cortex, suggesting an inverse relationship between brain activity and behavioural outcome on this task. The present findings demonstrate how auditory cortices contribute to long‐term effects of multisensory experiences on auditory object discrimination. We propose a new framework for the efficacy of multisensory processes to impact both current multisensory stimulus processing and unisensory discrimination abilities later in time.
Meaning in the avian auditory cortex: neural representation of communication calls
Authors: Elie Julie E. , Theunissen Frédéric E. 
Published: March 2015

AbstractUnderstanding how the brain extracts the behavioral meaning carried by specific vocalization types that can be emitted by various vocalizers and in different conditions is a central question in auditory research. This semantic categorization is a fundamental process required for acoustic communication, and presupposes discriminative and invariance properties of the auditory system for conspecific vocalizations. Songbirds have been used extensively to study vocal learning, but the communicative function of all their vocalizations and their neural representation has yet to be examined. In this study, we first generated a library containing almost the entire zebra finch vocal repertoire, and organised communication calls along nine different categories according to their behavioral meaning. We then investigated the neural representations of thesesemanticcategories in the primary and secondary auditory areas of six anesthetised zebra finches. To analyse how single units encode these call categories, we described neural responses in terms of their discrimination, selectivity and invariance properties. Quantitative measures for these neural properties were obtained with an optimal decoder using both spike counts and spike patterns. Information theoretic metrics show that almost half of the single units encode semantic information. Neurons achieve higher discrimination of these semantic categories by being more selective and more invariant. These results demonstrate that computations necessary for semantic categorization of meaningful vocalizations are already present in the auditory cortex, and emphasise the value of a neuro‐ethological approach to understand vocal communication.
Computational modelling suggests that temporal integration results from synaptic adaptation in auditory cortex
Authors: May Patrick J. C. , Westö Johan , Tiitinen Hannu 
Published: March 2015

AbstractIncoming sounds are represented in the context of preceding events, and this requires a memory mechanism that integrates information over time. Here, it was demonstrated that response adaptation, the suppression of neural responses due to stimulus repetition, might reflect a computational solution that auditory cortex uses for temporal integration. Adaptation is observed in single‐unit measurements as two‐tone forward masking effects and as stimulus‐specific adaptation (SSA). In non‐invasive observations, the amplitude of the auditory N1m response adapts strongly with stimulus repetition, and it is followed by response recovery (the so‐called mismatch response) to rare deviant events. The current computational simulations described the serial core‐belt‐parabelt structure of auditory cortex, and included synaptic adaptation, the short‐term, activity‐dependent depression of excitatory corticocortical connections. It was found that synaptic adaptation is sufficient for columns to respond selectively to tone pairs and complex tone sequences. These responses were defined as combination sensitive, thus reflecting temporal integration, when a strong response to a stimulus sequence was coupled with weaker responses both to the time‐reversed sequence and to the isolated sequence elements. The temporal complexity of the stimulus seemed to be reflected in the proportion of combination‐sensitive columns across the different regions of the model. Our results suggest that while synaptic adaptation produces facilitation and suppression effects, including SSA and the modulation of the N1m response, its functional significance may actually be in its contribution to temporal integration. This integration seems to benefit from the serial structure of auditory cortex.
Perceptual learning in the developing auditory cortex
Authors: Bao Shaowen 
Published: March 2015

AbstractA hallmark of the developing auditory cortex is the heightened plasticity in the critical period, during which acoustic inputs can indelibly alter cortical function. However, not all sounds in the natural acoustic environment are ethologically relevant. How does the auditory system resolve relevant sounds from the acoustic environment in such an early developmental stage when most associative learning mechanisms are not yet fully functional? What can the auditory system learn from one of the most important classes of sounds, animal vocalizations? How does naturalistic acoustic experience shape cortical sound representation and perception? To answer these questions, we need to consider an unusual strategy, statistical learning, where what the system needs to learn is embedded in the sensory input. Here, I will review recent findings on how certain statistical structures of natural animal vocalizations shape auditory cortical acoustic representations, and how cortical plasticity may underlie learned categorical sound perception. These results will be discussed in the context of human speech perception.
Single‐unit analysis of somatosensory processing in the core auditory cortex of hearing ferrets
Authors: Meredith M. Alex , Allman Brian L. 
Published: March 2015

AbstractThe recent findings in several species that the primary auditory cortex processes non‐auditory information have largely overlooked the possibility of somatosensory effects. Therefore, the present investigation examined the core auditory cortices (anterior auditory field and primary auditory cortex) for tactile responsivity. Multiple single‐unit recordings from anesthetised ferret cortex yielded histologically verified neurons (n = 311) tested with electronically controlled auditory, visual and tactile stimuli, and their combinations. Of the auditory neurons tested, a small proportion (17%) was influenced by visual cues, but a somewhat larger number (23%) was affected by tactile stimulation. Tactile effects rarely occurred alone and spiking responses were observed in bimodal auditory–tactile neurons. However, the broadest tactile effect that was observed, which occurred in all neuron types, was that of suppression of the response to a concurrent auditory cue. The presence of tactile effects in the core auditory cortices was supported by a substantial anatomical projection from the rostral suprasylvian sulcal somatosensory area. Collectively, these results demonstrate that crossmodal effects in the auditory cortex are not exclusively visual and that somatosensation plays a significant role in modulation of acoustic processing, and indicate that crossmodal plasticity following deafness may unmask these existing non‐auditory functions.
Subthreshold membrane responses underlying sparse spiking to natural vocal signals in auditory cortex
Authors: Perks Krista E. , Gentner Timothy Q. 
Published: March 2015

AbstractNatural acoustic communication signals, such as speech, are typically high‐dimensional with a wide range of co‐varying spectro‐temporal features at multiple timescales. The synaptic and network mechanisms for encoding these complex signals are largely unknown. We are investigating these mechanisms in high‐level sensory regions of the songbird auditory forebrain, where single neurons show sparse, object‐selective spiking responses to conspecific songs. Using whole‐cell in vivo patch clamp techniques in the caudal mesopallium and the caudal nidopallium of starlings, we examine song‐driven subthreshold and spiking activity. We find that both the subthreshold and the spiking activity are reliable (i.e. the same song drives a similar response each time it is presented) and specific (i.e. responses to different songs are distinct). Surprisingly, however, the reliability and specificity of the subthreshold response was uniformly high regardless of when the cell spiked, even for song stimuli that drove no spikes. We conclude that despite a selective and sparse spiking response, high‐level auditory cortical neurons are under continuous, non‐selective, stimulus‐specific synaptic control. To investigate the role of local network inhibition in this synaptic control, we then recorded extracellularly while pharmacologically blocking local GABAergic transmission. This manipulation modulated the strength and the reliability of stimulus‐driven spiking, consistent with a role for local inhibition in regulating the reliability of network activity and the stimulus specificity of the subthreshold response in single cells. We discuss these results in the context of underlying computations that could generate sparse, stimulus‐selective spiking responses, and models for hierarchical pooling.
Mixed‐complexity artificial grammar learning in humans and macaque monkeys: evaluating learning strategies
Authors: Wilson Benjamin , Smith Kenny , Petkov Christopher I. 
Published: March 2015

AbstractArtificial grammars (AG) can be used to generate rule‐based sequences of stimuli. Some of these can be used to investigate sequence‐processing computations in non‐human animals that might be related to, but not unique to, human language. Previous AG learning studies in non‐human animals have used different AGs to separately test for specific sequence‐processing abilities. However, given that natural language and certain animal communication systems (in particular, song) have multiple levels of complexity, mixed‐complexity AGs are needed to simultaneously evaluate sensitivity to the different features of the AG. Here, we tested humans and Rhesus macaques using a mixed‐complexity auditory AG, containing both adjacent (local) and non‐adjacent (longer‐distance) relationships. Following exposure to exemplary sequences generated by the AG, humans and macaques were individually tested with sequences that were either consistent with the AG or violated specific adjacent or non‐adjacent relationships. We observed a considerable level of cross‐species correspondence in the sensitivity of both humans and macaques to the adjacent AG relationships and to the statistical properties of the sequences. We found no significant sensitivity to the non‐adjacent AG relationships in the macaques. A subset of humans was sensitive to this non‐adjacent relationship, revealing interesting between‐ and within‐species differences in AG learning strategies. The results suggest that humans and macaques are largely comparably sensitive to the adjacent AG relationships and their statistical properties. However, in the presence of multiple cues to grammaticality, the non‐adjacent relationships are less salient to the macaques and many of the humans.
Aural localization of silent objects by active human biosonar: neural representations of virtual echo‐acoustic space
Authors: Wallmeier Ludwig , Kish Daniel , Wiegrebe Lutz , Flanagin Virginia L. 
Published: March 2015

AbstractSome blind humans have developed the remarkable ability to detect and localize objects through the auditory analysis of self‐generated tongue clicks. These echolocation experts show a corresponding increase in ‘visual’ cortex activity when listening to echo‐acoustic sounds. Echolocation in real‐life settings involves multiple reflections as well as active sound production, neither of which has been systematically addressed. We developed a virtualization technique that allows participants to actively perform such biosonar tasks in virtual echo‐acoustic space during magnetic resonance imaging (MRI). Tongue clicks, emitted in the MRI scanner, are picked up by a microphone, convolved in real time with the binaural impulse responses of a virtual space, and presented via headphones as virtual echoes. In this manner, we investigated the brain activity during active echo‐acoustic localization tasks. Our data show that, in blind echolocation experts, activations in the calcarine cortex are dramatically enhanced when a single reflector is introduced into otherwise anechoic virtual space. A pattern‐classification analysis revealed that, in the blind, calcarine cortex activation patterns could discriminate left‐side from right‐side reflectors. This was found in both blind experts, but the effect was significant for only one of them. In sighted controls, ‘visual’ cortex activations were insignificant, but activation patterns in the planum temporale were sufficient to discriminate left‐side from right‐side reflectors. Our data suggest that blind and echolocation‐trained, sighted subjects may recruit different neural substrates for the same active‐echolocation task.
Auditory and visual cortex of primates: a comparison of two sensory systems
Authors: Rauschecker Josef P. 
Published: March 2015

AbstractA comparative view of the brain, comparing related functions across species and sensory systems, offers a number of advantages. In particular, it allows separation of the formal purpose of a model structure from its implementation in specific brains. Models of auditory cortical processing can be conceived by analogy to the visual cortex, incorporating neural mechanisms that are found in both the visual and auditory systems. Examples of such canonical features at the columnar level are direction selectivity, size/bandwidth selectivity, and receptive fields with segregated vs. overlapping ON and OFF subregions. On a larger scale, parallel processing pathways have been envisioned that represent the two main facets of sensory perception: (i) identification of objects; and (ii) processing of space. Expanding this model in terms of sensorimotor integration and control offers an overarching view of cortical function independently of sensory modality.
The community ecology of pathogens: coinfection, coexistence and community composition
Authors: Seabloom Eric W. , Borer Elizabeth T. , Gross Kevin , Kendig Amy E. , Lacroix Christelle , Mitchell Charles E. , Mordecai Erin A. , Power Alison G. 
Published: March 2015

AbstractDisease and community ecology share conceptual and theoretical lineages, and there has been a resurgence of interest in strengthening links between these fields. Building on recent syntheses focused on the effects of host community composition on single pathogen systems, we examine pathogen (microparasite) communities using a stochastic metacommunity model as a starting point to bridge community and disease ecology perspectives. Such models incorporate the effects of core community processes, such as ecological drift, selection and dispersal, but have not been extended to incorporate host–pathogen interactions, such as immunosuppression or synergistic mortality, that are central to disease ecology. We use a two‐pathogen susceptible‐infected (SI) model to fill these gaps in the metacommunity approach; however,SImodels can be intractable for examining species‐diverse, spatially structured systems. By placing disease into a framework developed for community ecology, our synthesis highlights areas ripe for progress, including a theoretical framework that incorporates host dynamics, spatial structuring and evolutionary processes, as well as the data needed to test the predictions of such a model. Our synthesis points the way for this framework and demonstrates that a deeper understanding of pathogen community dynamics will emerge from approaches working at the interface of disease and community ecology.
Epilepsy and deprivation, a data linkage study
Authors: Pickrell William O. , Lacey Arron S. , Bodger Owen G. , Demmler Joanne C. , Thomas Rhys H. , Lyons Ronan A. , Smith Phil E. M. , Rees Mark I. , Kerr Mike P. 
Published: March 2015

SummaryObjectiveTo investigate whether the link between epilepsy and deprivation is due to factors associated with deprivation (social causation) or factors associated with a diagnosis of epilepsy (social drift).MethodsWe reviewed electronic primary health care records from 2004 to 2010, identifying prevalent and incident cases of epilepsy and recording linked deprivation scores. Logistic and Poisson regression models were used to calculate odds ratios and incidence rate ratios. The change in deprivation was measured 10 years after the initial diagnosis of epilepsy for a cohort of people.ResultsBetween 2004 and 2010, 8.1 million patient‐years of records were reviewed. Epilepsy prevalence and incidence were significantly associated with deprivation. Epilepsy prevalence ranged from 1.13% (1.07–1.19%) in the most deprived decile to 0.49% (0.45–0.53%) in the least deprived decile (adjusted odds ratio 0.92, p < 0.001). Epilepsy incidence ranged from 40/100,000 per year in the most deprived decile to 19/100,000 per year in the least deprived decile (adjusted incidence rate ratio 0.94, p < 0.001). There was no statistically significant change in deprivation index decile 10 years after a new diagnosis of epilepsy (mean difference −0.04, p = 0.85).SignificanceEpilepsy prevalence and incidence are strongly associated with deprivation; the deprivation score remains unchanged 10 years after a diagnosis of epilepsy. These findings suggest that increasing rates of epilepsy in deprived areas are more likely explained by social causation than by social drift. The nature of the association between incident epilepsy and social deprivation needs further exploration.
The Red‐Fluorescing Marine Fish Tripterygion delaisi can Perceive its Own Red Fluorescent Colour
Authors: Kalb Nadine , Schneider Ralf F. , Sprenger Dennis , Michiels Nico K. 
Published: March 2015

AbstractMany marine fishes show conspicuous red fluorescent body patterns. Recent work suggests that red fluorescence may be used as a visual colour cue in these species. Very few studies, however, have as yet been able to demonstrate that red fluorescent fish can actually perceive their own fluorescence. This is the first study to our knowledge in which a red fluorescent fish is trained to assess whether it can recognize red fluorescence. We used the triplefin Tripterygion delaisi, a species with conspicuous red fluorescent eye rings. Training and testing involved repeated binary choices between grey and red fluorescence cues. The training and testing were carried out under broad spectral illumination. The final testing phase involved cyan light illumination, mimicking natural ambient light at depth. When testing all nine combinations of three grey brightness levels against three red fluorescence brightness levels, individuals made significantly more correct choices than the random expectation under broad as well as cyan illumination. Under cyan illumination, fish trained on red chose the correct cue more often compared to fish trained on grey. An analysis of the effect of the brightness levels suggests that fish did indeed make their choices based on chromatic more than achromatic cues: The three grey levels did not affect the proportion of correct choices. We conclude that T. delaisi can perceive and respond to levels of fluorescence that are similar to its own. We also discuss the difficulties that can arise from using a binary choice design on a fish with a cryptobenthic lifestyle. We argue in favour of using sequential choice designs in future studies of T. delaisi.
Predicting a change in the order of spring phenology in temperate forests
Authors: Roberts Adrian M.I. , Tansey Christine , Smithers Richard J. , Phillimore Albert B. 
Published: March 2015

AbstractThe rise in spring temperatures over the past half‐century has led to advances in the phenology of many nontropical plants and animals. As species and populations differ in their phenological responses to temperature, an increase in temperatures has the potential to alter timing‐dependent species interactions. One species‐interaction that may be affected is the competition for light in deciduous forests, where early vernal species have a narrow window of opportunity for growth before late spring species cast shade. Here we consider the Marsham phenology time series of first leafing dates of thirteen tree species and flowering dates of one ground flora species, which spans two centuries. The exceptional length of this time series permits a rare comparison of the statistical support for parameter‐rich regression and mechanistic thermal sensitivity phenology models. While mechanistic models perform best in the majority of cases, both they and the regression models provide remarkably consistent insights into the relative sensitivity of each species to forcing and chilling effects. All species are sensitive to spring forcing, but we also find that vernal and northern European species are responsive to cold temperatures in the previous autumn. Whether this sensitivity reflects a chilling requirement or a delaying of dormancy remains to be tested. We then apply the models to projected future temperature data under a fossil fuel intensive emissions scenario and predict that while some species will advance substantially others will advance by less and may even be delayed due to a rise in autumn and winter temperatures. Considering the projected responses of all fourteen species, we anticipate a change in the order of spring events, which may lead to changes in competitive advantage for light with potential implications for the composition of temperate forests.