Spatiotemporal Response Patterns Research Articles

Functiogenesis of the embryonic central nervous system revealed by optical recording with a voltage-sensitive dye.

Clarification of the functiogenesis of the embryonic central nervous system (CNS) has long been problematic, because conventional electrophysiological techniques have several limitations. First, early embryonic neurons are small and fragile, and the application of microelectrodes is challenging. Second, the simultaneous monitoring of electrical activity from multiple sites is limited, and as a consequence, spatiotemporal response patterns of neural networks cannot be assessed. We have applied multiple-site optical recording with a voltage-sensitive dye to the embryonic CNS and paved a new way to analyze the functiogenesis of the CNS. In this review, we discuss key points of optical recording in the embryonic CNS and introduce recent progress in optical investigations on the embryonic CNS with special emphasis on the development of the chick olfactory system. The studies clearly demonstrate the usefulness of voltage-sensitive dye recording as a powerful tool for elucidating the functional organization of the vertebrate embryonic CNS.

Responses of net primary productivity to phenological dynamics in the Tibetan Plateau, China

Quantifying the response of vegetation Net Primary Productivity (NPP) to phenological dynamics is critical to study climate change effects on ecosystem dynamics in the high-latitude, so investigating responses of NPP to phenological dynamics is becoming an increasing important way to identify and predict global ecosystem dynamics. In this study, we intend to quantifying the temporal trends and spatial variations of vegetation phenology and NPP across the Tibetan Plateau by calibrating and analyzing time series of the MODIS-derived normalized difference vegetation index (NDVI) during 2002–2012, and examining the mechanisms of vegetation NPP response to phenological dynamics over the plateau. Our results indicated that most of the plateau experienced a coninuous advancing trend in the beginning of vegetation growing season (BGS) and a delaying trend in the end of vegetation growing season (EGS), consequently a prolonged length of vegetation growing season (LGS). Accordingly, NPP also substantially increased in most parts of the plateau. Meanwhile, the spatial patterns of the BGS, EGS, LGS and NPP varied in accordcance with the heat and water gradient across the plateau. The response modes of the NPP to phenological shifs varied within different climatic regimes, and the spatiotemporal response patterns were primarily controlled by the local climatic and topographic conditions. Moreover, temperature and precipitation played different roles in diverse responses of NPP to phenological dynamics, implying a profound effect of climate on response mechanism of the NPP to phenological changes.

Early Visual Word Processing Is Flexible: Evidence from Spatiotemporal Brain Dynamics.

Visual word recognition is often described as automatic, but the functional locus of top-down effects is still a matter of debate. Do task demands modulate how information is retrieved, or only how it is used? We used EEG/MEG recordings to assess whether, when, and how task contexts modify early retrieval of specific psycholinguistic information in occipitotemporal cortex, an area likely to contribute to early stages of visual word processing. Using a parametric approach, we analyzed the spatiotemporal response patterns of occipitotemporal cortex for orthographic, lexical, and semantic variables in three psycholinguistic tasks: silent reading, lexical decision, and semantic decision. Task modulation of word frequency and imageability effects occurred simultaneously in ventral occipitotemporal regions-in the vicinity of the putative visual word form area-around 160 msec, following task effects on orthographic typicality around 100 msec. Frequency and typicality also produced task-independent effects in anterior temporal lobe regions after 200 msec. The early task modulation for several specific psycholinguistic variables indicates that occipitotemporal areas integrate perceptual input with prior knowledge in a task-dependent manner. Still, later task-independent effects in anterior temporal lobes suggest that word recognition eventually leads to retrieval of semantic information irrespective of task demands. We conclude that even a highly overlearned visual task like word recognition should be described as flexible rather than automatic.

Strategies for optical control and simultaneous electrical readout of extended cortical circuits

BackgroundTo dissect the intricate workings of neural circuits, it is essential to gain precise control over subsets of neurons while retaining the ability to monitor larger-scale circuit dynamics. This requires the ability to both evoke and record neural activity simultaneously with high spatial and temporal resolution. New MethodIn this paper we present approaches that address this need by combining micro-electrocorticography (μECoG) with optogenetics in ways that avoid photovoltaic artifacts. ResultsWe demonstrate that variations of this approach are broadly applicable across three commonly studied mammalian species – mouse, rat, and macaque monkey – and that the recorded μECoG signal shows complex spectral and spatio-temporal patterns in response to optical stimulation. Comparison with existing methodsWhile optogenetics provides the ability to excite or inhibit neural subpopulations in a targeted fashion, large-scale recording of resulting neural activity remains challenging. Recent advances in optical physiology, such as genetically encoded Ca2+ indicators, are promising but currently do not allow simultaneous recordings from extended cortical areas due to limitations in optical imaging hardware. ConclusionsWe demonstrate techniques for the large-scale simultaneous interrogation of cortical circuits in three commonly used mammalian species.

Expression patterns of WRKY genes in di-haploid Populus simonii × P. nigra in response to osmotic stress and ABA treatment

In this study, 108 WRKY genes with complete conserved WRKY domain and zinc-finger motif were identified from poplar in silico, and they were classified into three subfamilies named I, II, and III. The WRKY members in group II were further clustered into five subgroups (IIa–e), where members in group I and III formed a single cluster. Thirteen highly expressed genes were employed to profile their spatio-temporal expression patterns in response to osmotic stress and ABA treatment by qRT-PCR. Under both osmotic stress and ABA treatment, overall gene expression displayed a dynamic pattern of “induced amplification—recover” in leaves, but not in roots and stems. Regarding individual gene expression across the seven time points and the three tissues, five genes (PthWRKY28, 56, 62, 88, and 106) were involved in regulation of both osmotic stress tolerance and ABA signaling transduction pathways. Meanwhile, four genes (PthWRKY41, 44, 51, and 116) played distinct roles in either osmotic stress or ABA treatment condition. These suggested that WRKY genes and corresponding pathways may play a critical role in regulating poplar responses to osmotic stress and ABA treatment in a dynamic and tissue-specific manner.

Prolonged odor information in the antennal lobe of Drosophila melanogaster

Event Abstract Back to Event Prolonged odor information in the antennal lobe of Drosophila melanogaster Alja Lüdke1*, C. G. Galizia1 and Paul Szyszka1 1 Universität Konstanz, Neurobiology, Germany Trace conditioning, an associative learning task in which the behaviorally neutral stimulus and the meaningful stimulus (reward or punishment) that elicits the response do not overlap in time, requires some sort of sensory memory which keeps information about the neutral stimulus after its termination, e.g. a stimulus trace. In this study, we investigated whether and how olfactory information is maintained and changed on a short temporal scale in the first olfactory brain area, the antennal lobe, of Drosophila. Using in vivo calcium imaging and the GAL4/UAS system, we selectively measured responses from two types of the olfactory network neurons: the receptor neurons itself, and the projection neurons that pass the information to higher brain areas. We analyzed the spatio-temporal response patterns that are elicited during the stimulation, as well as the subsequent patterns after stimulus offset. Odors evoked stimulus specific response patterns of activated and inhibited functional subunits of the antennal lobe, the glomeruli, which convey information in a combinatorial manner (see http://neuro.uni-konstanz.de/DoOR). With the stimulus offset, the odor response pattern changed to a new and dissimilar post-odor pattern. Although odor specific, these post-odor activity patterns differed from the initial response pattern, and were invariant to changes of the preceding stimulus length. Taken together, these results show that odors elicit a specific trace in the antennal lobe network activity of Drosophila. Whether this activity trace is used as a substrate for the trace found in behavioral responses remains to be determined. Keywords: calcium imaging, Drosophila, Memory, Olfaction, trace conditioning Conference: Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012. Presentation Type: Poster Topic: Learning, plasticity, memory Citation: Lüdke A, Galizia CG and Szyszka P (2012). Prolonged odor information in the antennal lobe of Drosophila melanogaster. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference 2012. doi: 10.3389/conf.fncom.2012.55.00125 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 11 May 2012; Published Online: 12 Sep 2012. * Correspondence: Dr. Alja Lüdke, Universität Konstanz, Neurobiology, Konstanz, D-78464, Germany, alja.luedke@uni.konstanz.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Alja Lüdke C. G Galizia Paul Szyszka Google Alja Lüdke C. G Galizia Paul Szyszka Google Scholar Alja Lüdke C. G Galizia Paul Szyszka PubMed Alja Lüdke C. G Galizia Paul Szyszka Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Keeping their distance? Odor response patterns along the concentration range

We investigate the interplay of odor identity and concentration coding in the antennal lobe (AL) of the honeybee Apis mellifera. In this primary olfactory center of the honeybee brain, odors are encoded by the spatio-temporal response patterns of olfactory glomeruli. With rising odor concentration, further glomerular responses are recruited into the patterns, which affects distances between the patterns. Based on calcium-imaging recordings, we found that such pattern broadening renders distances between glomerular response patterns closer to chemical distances between the corresponding odor molecules. Our results offer an explanation for the honeybee's improved odor discrimination performance at higher odor concentrations.

Spatiotemporal representation of the pitch of harmonic complex tones in the auditory nerve.

The pitch of harmonic complex tones plays an important role in speech and music perception and the analysis of auditory scenes, yet traditional rate-place and temporal models for pitch processing provide only an incomplete description of the psychophysical data. To test physiologically a model based on spatiotemporal pitch cues created by the cochlear traveling wave (Shamma, 1985), we recorded from single fibers in the auditory nerve of anesthetized cat in response to harmonic complex tones with missing fundamentals and equal-amplitude harmonics. We used the principle of scaling invariance in cochlear mechanics to infer the spatiotemporal response pattern to a given stimulus from a series of measurements made in a single fiber as a function of fundamental frequency F0. We found that spatiotemporal cues to resolved harmonics are available for F0 values between 350 and 1100 Hz and that these cues are more robust than traditional rate-place cues at high stimulus levels. The lower F0 limit is determined by the limited frequency selectivity of the cochlea, whereas the upper limit is caused by the degradation of phase locking to the stimulus fine structure at high frequencies. The spatiotemporal representation is consistent with the upper F0 limit to the perception of the pitch of complex tones with a missing fundamental, and its effectiveness does not depend on the relative phase between resolved harmonics. The spatiotemporal representation is thus consistent with key trends in human psychophysics.

Spatiotemporal mapping of ENSO and PDO surface meteorological signals in British Columbia, Yukon, and southeast Alaska

We assessed the impacts of some key Pacific ocean‐atmosphere circulation patterns on annual cycles of temperature and precipitation across British Columbia, Yukon, and southeast Alaska. The El Niño‐Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and ENSO conditional on PDO states were considered in composite analyses of 71 long, high‐quality datasets from surface meteorological stations. Month‐by‐month, station‐by‐station Monte Carlo bootstrap tests were employed to assess statistical significance. The results trace precipitation and temperature responses as a function of location, season, and climate mode. In summary, temperature responses were relatively uniform, with higher (lower) temperatures during the warm (cool) phases of these circulation patterns. Nevertheless, strength and seasonal persistence varied considerably with location and climate mode. Impacts were generally most consistent in winter and spring but could extend through most of the year. Overall spatiotemporal patterns in precipitation response were decoupled from those in temperature and were far more heterogeneous. Complexities in precipitation signals included north‐south inverse teleconnectivity along the Pacific coast, with a zero‐response hinge point in the approximate vicinity of northern Vancouver Island; seasonally opposite anomalies in several interior regions, which might conceivably reflect contrasting effects of Pacific climate modes on wintertime frontal storms versus summertime convective storms; and a consistent lack of substantial response in northwestern British Columbia and possibly southwestern Yukon, conjectured to reflect complications associated with the Icefield Ranges. The product is intended primarily as a basic‐level set of climate response maps for hydrologists, biologists, foresters, and others who require empirical assessments of relatively local‐scale, year‐round ENSO and PDO effects across this broad region.

Polymers with embedded chemical indicators as an artificial olfactory mucosa

Physiological investigations suggest that the olfactory mucosa probably plays an ancillary role in the recognition of odours introducing a sort of chromatographic separation that, together with the zonal distribution of olfactory receptors, gives place to selective spatio-temporal response patterns. It has been recently suggested that this behaviour may be simulated by chemical sensors embedded in continuous polymer layers. In this paper, in analogy to the biology of olfaction, a simple and compact platform able to separate and detect gases and vapours on the basis of their diffusion properties is proposed. In such a system, broadly selective colour indicators, such as metalloporphyrins, are embedded in continuous layers of polymers with different sorption properties. The exposure to various alcohols and amines shows that the porphyrins are mainly responsible for the recognition of the molecular family, while the occurring spatio-temporal signal patterns make possible the identification of the individual chemical species.

Relation between derived-band auditory brainstem response latencies and behavioral frequency selectivity

Derived-band click-evoked auditory brainstem responses (ABRs) were obtained for normal-hearing (NH) and sensorineurally hearing-impaired (HI) listeners. The latencies extracted from these responses, as a function of derived-band center frequency and click level, served as objective estimates of cochlear response times. For the same listeners, auditory-filter bandwidths at 2 kHz were estimated using a behavioral notched-noise masking paradigm. Generally, shorter derived-band latencies were observed for the HI than for the NH listeners. Only at low click sensation levels, prolonged latencies were obtained for some of the HI listeners. The behavioral auditory-filter bandwidths accounted for the across-listener variability in the ABR latencies: Cochlear response time decreased with increasing filter bandwidth, consistent with linear-system theory. The results link cochlear response time and frequency selectivity in human listeners and offer a window to better understand how hearing impairment affects the spatiotemporal cochlear response pattern.

Estimation of cochlear response times using lateralization of frequency-mismatched tones

Behavioral and objective estimates of cochlear response times (CRTs) and traveling-wave (TW) velocity were compared for three normal-hearing listeners. Differences between frequency-specific CRTs were estimated via lateralization of pulsed tones that were interaurally mismatched in frequency, similar to a paradigm proposed by Zerlin [(1969). J. Acoust. Soc. Am. 46, 1011-1015]. In addition, derived-band auditory brainstem responses were obtained as a function of derived-band center frequency. The latencies extracted from these responses served as objective estimates of CRTs. Estimates of TW velocity were calculated from the obtained CRTs. The correspondence between behavioral and objective estimates of CRT and TW velocity was examined. For frequencies up to 1.5 kHz, the behavioral method yielded reproducible results, which were consistent with the objective estimates. For higher frequencies, CRT differences could not be estimated with the behavioral method due to limitations of the lateralization paradigm. The method might be useful for studying the spatiotemporal cochlear response pattern in human listeners.

Odor coding by modules of coherent mitral/tufted cells in the vertebrate olfactory bulb

Odor representation in the olfactory bulb (OB) undergoes a transformation from a combinatorial glomerular map to a distributed mitral/tufted (M/T) cell code. To understand this transformation, we analyzed the odor representation in large populations of individual M/T cells in the Xenopus OB. The spontaneous [Ca(2+)] activities of M/T cells appeared to be irregular, but there were groups of spatially distributed neurons showing synchronized [Ca(2+)] activities. These neurons were always connected to the same glomerulus. Odorants elicited complex spatiotemporal response patterns in M/T cells where nearby neurons generally showed little correlation. But the responses of neurons connected to the same glomerulus were virtually identical, irrespective of whether the responses were excitatory or inhibitory, and independent of the distance between them. Synchronous neurons received correlated EPSCs and were coupled by electrical conductances that could account for the correlated responses. Thus, at the output stage of the OB, odors are represented by modules of distributed and synchronous M/T cells associated with the same glomeruli. This allows for parallel input to higher brain centers.

Olfactory Information Processing in theDrosophilaAntennal Lobe: Anything Goes?

When an animal smells an odor, olfactory sensory neurons generate an activity pattern across olfactory glomeruli of the first sensory neuropil, the insect antennal lobe or the vertebrate olfactory bulb. Here, several networks of local neurons interact with sensory neurons and with output neurons--insect projection neurons, or vertebrate mitral/tufted cells. The extent and form of information processing taking place in these local networks has been subject of controversy. To investigate the role of local neurons in odor information processing we have used the calcium sensor G-CaMP to perform in vivo recordings of odor-evoked spatiotemporal activity patterns in five genetically defined neuron populations of the antennal lobe of Drosophila melanogaster: three distinct populations of local neurons (two GABAergic and one cholinergic), as well as sensory neurons and projection neurons. Odor-specific and concentration dependent spatiotemporal response patterns varied among neuron populations. Activity transfer differed along the olfactory pathway for different glomerulus-odor combinations: we found cases of profile broadening and of linear and complex transfer. Moreover, the discriminability between the odors also varied across neuron populations and was maximal in projection neurons. Discriminatory power increased with higher odor concentrations over a wide dynamic range, but decreased at the highest concentration. These results show the complexity and diversity of odor information processing mechanisms across olfactory glomeruli in the fly antennal lobe.

Robust Reservoir Generation by Correlation‐Based Learning

Reservoir computing (RC) is a new framework for neural computation. A reservoir is usually a recurrent neural network with fixed random connections. In this article, we propose an RC model in which the connections in the reservoir are modifiable. Specifically, we consider correlation‐based learning (CBL), which modifies the connection weight between a given pair of neurons according to the correlation in their activities. We demonstrate that CBL enables the reservoir to reproduce almost the same spatiotemporal activity patterns in response to an identical input stimulus in the presence of noise. This result suggests that CBL enhances the robustness in the generation of the spatiotemporal activity pattern against noise in input signals. We apply our RC model to trace eyeblink conditioning. The reservoir bridged the gap of an interstimulus interval between the conditioned and unconditioned stimuli, and a readout neuron was able to learn and express the timed conditioned response.

Representation of the verb's argument-structure in the human brain

BackgroundA verb's argument structure defines the number and relationships of participants needed for a complete event. One-argument (intransitive) verbs require only a subject to make a complete sentence, while two- and three-argument verbs (transitives and ditransitives) normally take direct and indirect objects. Cortical responses to verbs embedded into sentences (correct or with syntactic violations) indicate the processing of the verb's argument structure in the human brain. The two experiments of the present study examined whether and how this processing is reflected in distinct spatio-temporal cortical response patterns to isolated verbs and/or verbs presented in minimal context.ResultsThe magnetoencephalogram was recorded while 22 native German-speaking adults saw 130 German verbs, presented one at a time for 150 ms each in experiment 1. Verb-evoked electromagnetic responses at 250 – 300 ms after stimulus onset, analyzed in source space, were higher in the left middle temporal gyrus for verbs that take only one argument, relative to two- and three-argument verbs. In experiment 2, the same verbs (presented in different order) were preceded by a proper name specifying the subject of the verb. This produced additional activation between 350 and 450 ms in or near the left inferior frontal gyrus, activity being larger and peaking earlier for one-argument verbs that required no further arguments to form a complete sentence.ConclusionLocalization of sources of activity suggests that the activation in temporal and frontal regions varies with the degree by which representations of an event as a part of the verbs' semantics are completed during parsing.

Pitch representations in the auditory nerve: two concurrent complex tones.

Pitch differences between concurrent sounds are important cues used in auditory scene analysis and also play a major role in music perception. To investigate the neural codes underlying these perceptual abilities, we recorded from single fibers in the cat auditory nerve in response to two concurrent harmonic complex tones with missing fundamentals and equal-amplitude harmonics. We investigated the efficacy of rate-place and interspike-interval codes to represent both pitches of the two tones, which had fundamental frequency (F0) ratios of 15/14 or 11/9. We relied on the principle of scaling invariance in cochlear mechanics to infer the spatiotemporal response patterns to a given stimulus from a series of measurements made in a single fiber as a function of F0. Templates created by a peripheral auditory model were used to estimate the F0s of double complex tones from the inferred distribution of firing rate along the tonotopic axis. This rate-place representation was accurate for F0s greater, similar900 Hz. Surprisingly, rate-based F0 estimates were accurate even when the two-tone mixture contained no resolved harmonics, so long as some harmonics were resolved prior to mixing. We also extended methods used previously for single complex tones to estimate the F0s of concurrent complex tones from interspike-interval distributions pooled over the tonotopic axis. The interval-based representation was accurate for F0s less, similar900 Hz, where the two-tone mixture contained no resolved harmonics. Together, the rate-place and interval-based representations allow accurate pitch perception for concurrent sounds over the entire range of human voice and cat vocalizations.

Time-frequency feature extraction from frequency-modulated sounds in a population of auditory cortical neurons

This research is aimed at understanding how time-frequency features are extracted from frequency-modulated (FM) sounds in auditory cortical neurons. We investigated spatiotemporal response patterns in the primary auditory cortex in the guinea pig, using an optical recording method (MiCAM Ultima; Brain Vision) with a voltage-sensitive dye (RH795). Experiments were performed under anesthesia (ketamine, 100 mg/kg and xylazine, 25 mg/kg). A pure tone (PT) evoked a strong on-response that was followed by an inhibitory phase lasting approximately for 100 ms. An exponential FM sound evoked an additional activity moving along the frequency axis. Such an FM response became more evident when the frequency of the FM sound was modulated in a wider range. The position of the peak amplitude of the later FM response was shifted in accordance with the direction of the FM sweep, but the distance of the shift tended to be in the range of around 1 mm. Accordingly, the FM response sometimes appeared in isofrequency areas outside those covering the frequency range of the FM sound. These results indicate that interactions between excitatory and inhibitory neurons provide a robust FM detector that utilizes maximally the frequency-response area (FRA) of neurons distributed along the frequency axis in the auditory cortex.

Extraction of sounds’ time‐frequency features in the auditory cortex

Although ‘‘time‐frequency feature extraction’’ is a fundamental cue that is used to recognize speech sounds, its physiological mechanisms remain largely unknown. This research is aimed at understanding what time‐frequency features of sounds are extracted by auditory cortical neurons. We investigated spatiotemporal response patterns in the guinea‐pig auditory cortex, using an optical recording method (MiCAM Ultima; Brain Vision) with a voltage‐sensitive dye (RH795). Experiments were performed under anesthesia (ketamine, 100 mg/kg, and xylazine, 25 mg/kg). Pure tones (PTs), frequency‐modulated (FM) sounds with various modulation rates, and their combinations were presented to the animals. Cortical activation was induced at the onset and offset of PTs along the isofrequency contours. The onset response was followed by strong inhibition. In contrast, FM sounds evoked an additional activation moving across the isofrequency contours in the cortex, with locations corresponding to the instantaneous frequency inpu...

Study-level wavelet cluster analysis and data-driven signal models in pharmacological MRI

In pharmacological MRI (phMRI) studies tracking signal changes following the acute administration of a compound, the spatiotemporal pattern of response is often unknown a priori. Moreover, when analysed within a general linear model (GLM) framework, the experimental paradigm of a single injection point under-informs the construction of an appropriate signal model, and information from pharmacokinetics or ancillary in vivo studies may be unavailable or insufficient to accurately describe the dynamic signal changes observed following injection of the drug. Here, we extend the application of a data-driven clustering algorithm, wavelet cluster analysis (WCA), to phMRI data from one or more groups of subjects in a study. A WCA decomposition of spatially concatenated time series’ provides a compact overview of spatiotemporal response patterns across cohorts, highlighting typical temporal signatures, brain regions implicated in the response and inter-subject variability. Further, we demonstrate the use of regressors based on selected temporal components as suitable signal models in GLM-based analyses, resulting in a close fit to dynamic phMRI signal changes. This approach is illustrated with simulated data and two representative in vivo phMRI studies in the rat (nicotine and apomorphine challenges).