Browsing by Subject "REPRESENTATION"

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  • Tervo, Aino E.; Metsomaa, Johanna; Nieminen, Jaakko O.; Sarvas, Jukka; Ilmoniemi, Risto J. (2020)
    Transcranial magnetic stimulation (TMS) protocols often include a manual search of an optimal location and orientation of the coil or peak stimulating electric field to elicit motor responses in a target muscle. This target search is laborious, and the result is user-dependent. Here, we present a closed-loop search method that utilizes automatic electronic adjustment of the stimulation based on the previous responses. The electronic adjustment is achieved by multi-locus TMS, and the adaptive guiding of the stimulation is based on the principles of Bayesian optimization to minimize the number of stimuli (and time) needed in the search. We compared our target-search method with other methods, such as systematic sampling in a predefined cortical grid. Validation experiments on five healthy volunteers and further offline simulations showed that our adaptively guided search method needs only a relatively small number of stimuli to provide outcomes with good accuracy and precision. The automated method enables fast and user-independent optimization of stimulation parameters in research and clinical applications of TMS.
  • Niemi, Tero; Kokkonen, Teemu; Sillanpää, Nora; Setälä, Heikki; Koivusalo, Harri (2019)
    Constructing hydrological models for large urban areas is time consuming and laborious due to the requirements for high-resolution data and fine model detail. An open-source algorithm using adaptive subcatchments is proposed to automate Storm Water Management Model (SWMM) construction. The algorithm merges areas with homogeneous land cover and a common outlet into larger subcatchments, while retaining small-scale details where land cover or topography is more heterogeneous. The method was tested on an 85-ha urban catchment in Helsinki, Finland. A model with adaptive subcatchments reproduced the observed discharge at the catchment outlet with high model-performance indices emphasizing the strength of the proposed method. Computation times of the adaptive model were substantially lower than those of a corresponding model with uniformly sized high-resolution subcatchments. Given that high-resolution land cover and topography data are available, the proposed algorithm provides an advanced method for implementing SWMM models automatically even for large urban catchments without a substantial manual workload. Simultaneously, the high-resolution land cover details of the catchments can be maintained where they matter the most. (c) 2019 American Society of Civil Engineers.
  • Dawson, Caitlin; Tervaniemi, Mari; Aalto, Daniel (2018)
    Both musical training and native language have been shown to have experience-based plastic effects on auditory processing. However, the combined effects within individuals are unclear. Recent research suggests that musical training and tone language speaking are not clearly additive in their effects on processing of auditory features and that there may be a disconnect between perceptual and neural signatures of auditory feature processing. The literature has only recently begun to investigate the effects of musical expertise on basic auditory processing for different linguistic groups. This work provides a profile of primary auditory feature discrimination for Mandarin speaking musicians and nonmusicians. The musicians showed enhanced perceptual discrimination for both frequency and duration as well as enhanced duration discrimination in a multifeature discrimination task, compared to nonmusicians. However, there were no differences between the groups in duration processing of nonspeech sounds at a subcortical level or in subcortical frequency representation of a nonnative tone contour, for f(o) or for the first or second formant region. The results indicate that musical expertise provides a cognitive, but not subcortical, advantage in a population of Mandarin speakers.
  • Virtanen, Lari S.; Olkkonen, Maria; Saarela, Toni P. (2020)
    Color serves both to segment a scene into objects and background and to identify objects. Although objects and surfaces usually contain multiple colors, humans can readily extract a representative color description, for instance, that tomatoes are red and bananas yellow. The study of color discrimination and identification has a long history, yet we know little about the formation of summary representations of multicolored stimuli. Here, we characterize the human ability to integrate hue information over space for simple color stimuli varying in the amount of information, stimulus size, and spatial configuration of stimulus elements. We show that humans are efficient at integrating hue information over space beyond what has been shown before for color stimuli. Integration depends only on the amount of information in the display and not on spatial factors such as element size or spatial configuration in the range measured. Finally, we find that observers spontaneously prefer a simple averaging strategy even with skewed color distributions. These results shed light on how human observers form summary representations of color and make a link between the perception of polychromatic surfaces and the broader literature of ensemble perception.
  • Aitamurto, Kaarina (2019)
    Transnational Islam is increasingly presented in the Russian political rhetoric as a security threat. Therefore, Russian politicians and authorities attempt to support indigenous or national forms of Islam. Similar policies are implemented in several western European countries. Yet they tend to disregard the heterogeneity of the Muslim community, they create exclusions and they are often conceived as imposing outside evaluations and interpretations on Islam. This contribution analyses initiatives intended to develop a national Islam in post-Soviet Russia. While the aims, methods and problems in different countries are often quite similar, the values and norms underlying these initiatives vary and reflect the societies from which they emerge. This contribution argues that since the 1990s, the changes in the political line of the Kremlin have impacted the project for a ‘national’ Islam by placing less emphasis on liberal values and more emphasis on adherence to loyalism and political conservatism.
  • Teivainen, Teivo (2019)
    Based on conversations with and publications of Samir Amin, the article explores connections between his ideas on global political strategy and sexual self-determination. One of the questions is about struggles related to homosexuality in Africa. To what extent did he believe that some of the demands for sexual self-determination, including certain forms of feminism and LGBT rights, were so overly embedded in Eurocentrism that they were not fully suitable for popular struggles in many parts of the Global South? The question is framed in the context of state-centric conceptions of the political. Even if some of the analysis includes a critical tone toward his strategical options, it also highlights the continuing importance of Samir Amin as a point of reference for future struggles to create transnational and global instruments for democratic transformations.
  • Kyttala, Aija; Moraghebi, Roksana; Valensisi, Cristina; Kettunen, Johannes; Andrus, Colin; Pasumarthy, Kalyan Kumar; Nakanishi, Mahito; Nishimura, Ken; Ohtaka, Manami; Weltner, Jere; Van Handel, Ben; Parkkonen, Olavi; Sinisalo, Juha; Jalanko, Anu; Hawkins, R. David; Woods, Niels-Bjarne; Otonkoski, Timo; Trokovic, Ras (2016)
    Reports on the retention of somatic cell memory in induced pluripotent stem cells (iPSCs) have complicated the selection of the optimal cell type for the generation of iPSC biobanks. To address this issue we compared transcriptomic, epigenetic, and differentiation propensities of genetically matched human iPSCs derived from fibroblasts and blood, two tissues of the most practical relevance for biobanking. Our results show that iPSC lines derived from the same donor are highly similar to each other. However, genetic variation imparts a donor-specific expression and methylation profile in reprogrammed cells that leads to variable functional capacities of iPSC lines. Our results suggest that integration-free, bona fide iPSC lines from fibroblasts and blood can be combined in repositories to form biobanks. Due to the impact of genetic variation on iPSC differentiation, biobanks should contain cells from large numbers of donors.
  • Pitkanen, Minna; ShogoYazawa,; Airaksinen, Katja; Lioumis, Pantelis; Nurminen, Jussi; Pekkonen, Eero; Makela, Jyrki P. (2019)
    The mapping of the sensorimotor cortex gives information about the cortical motor and sensory functions. Typical mapping methods are navigated transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG). The differences between these mapping methods are, however, not fully known. TMS center of gravities (CoGs), MEG somatosensory evoked fields (SEFs), corticomuscular coherence (CMC), and corticokinematic coherence (CKC) were mapped in ten healthy adults. TMS mapping was performed for first dorsal interosseous (FDI) and extensor carpi radialis (ECR) muscles. SEFs were induced by tactile stimulation of the index finger. CMC and CKC were determined as the coherence between MEG signals and the electromyography or accelerometer signals, respectively, during voluntary muscle activity. CMC was mapped during the activation of FDI and ECR muscles separately, whereas CKC was measured during the waving of the index finger at a rate of 3-4 Hz. The maximum CMC was found at beta frequency range, whereas maximum CKC was found at the movement frequency. The mean Euclidean distances between different localizations were within 20 mm. The smallest distance was found between TMS FDI and TMS ECR CoGs and longest between CMC FDI and CMC ECR sites. TMS-inferred localizations (CoGs) were less variable across participants than MEG-inferred localizations (CMC, CKC). On average, SEF locations were 8 mm lateral to the TMS CoGs (p <0.01). No differences between hemispheres were found. Based on the results, TMS appears to be more viable than MEG in locating motor cortical areas.
  • Kilpeläinen, Markku; Georgeson, Mark A. (2018)
    The locations of objects in our environment constitute arguably the most important piece of information our visual system must convey to facilitate successful visually guided behaviour. However, the relevant objects are usually not point-like and do not have one unique location attribute. Relatively little is known about how the visual system represents the location of such large objects as visual processing is, both on neural and perceptual level, highly edge dominated. In this study, human observers made saccades to the centres of luminance defined squares (width 4 deg), which appeared at random locations (8 deg eccentricity). The phase structure of the square was manipulated such that the points of maximum luminance gradient at the square’s edges shifted from trial to trial. The average saccade endpoints of all subjects followed those shifts in remarkable quantitative agreement. Further experiments showed that the shifts were caused by the edge manipulations, not by changes in luminance structure near the centre of the square or outside the square. We conclude that the human visual system programs saccades to large luminance defined square objects based on edge locations derived from the points of maximum luminance gradients at the square’s edges.
  • Rantala, Maaria; Lassas, M.; Sampo, J.; Takalo, J.; Timonen, J.; Siltanen, Mikko Samuli (2014)
  • Leminen, Alina; Verwoert, Maxime; Moisala, Mona; Salmela, Viljami; Wikman, Patrik; Alho, Kimmo (2020)
    In real-life noisy situations, we can selectively attend to conversations in the presence of irrelevant voices, but neurocognitive mechanisms in such natural listening situations remain largely unexplored. Previous research has shown distributed activity in the mid superior temporal gyrus (STG) and sulcus (STS) while listening to speech and human voices, in the posterior STS and fusiform gyrus when combining auditory, visual and linguistic information, as well as in left-hemisphere temporal and frontal cortical areas during comprehension. In the present functional magnetic resonance imaging (fMRI) study, we investigated how selective attention modulates neural responses to naturalistic audiovisual dialogues. Our healthy adult participants (N = 15) selectively attended to video-taped dialogues between a man and woman in the presence of irrelevant continuous speech in the background. We modulated the auditory quality of dialogues with noise vocoding and their visual quality by masking speech-related facial movements. Both increased auditory quality and increased visual quality were associated with bilateral activity enhancements in the STG/STS. In addition, decreased audiovisual stimulus quality elicited enhanced fronto-parietal activity, presumably reflecting increased attentional demands. Finally, attention to the dialogues, in relation to a control task where a fixation cross was attended and the dialogue ignored, yielded enhanced activity in the left planum polare, angular gyrus, the right temporal pole, as well as in the orbitofrontal/ventromedial prefrontal cortex and posterior cingulate gyrus. Our findings suggest that naturalistic conversations effectively engage participants and reveal brain networks related to social perception in addition to speech and semantic processing networks.
  • Hytönen, Tuomas; Martikainen, Henri; Vuorinen, Emil (2019)
    We prove the mixed-norm LpLq-boundedness of a general class of singular integral operators having a multi-parameter singularity and acting on vector-valued (UMD Banach lattice-valued) functions. Moreover, families of such operators with uniform assumptions are shown to be not only uniformly bounded but R-bounded, a genuinely stronger property that is often needed in applications. Previous results of this nature only dealt with convolution-type or slightly more general paraproduct-free singular integrals. In contrast, our analysis specifically targets the array of different partial paraproducts that arise in the multi-parameter setting by interpreting them as paraproduct-valued one-parameter operators. This new point-of-view provides a conceptual simplification over the existing representation results for multi-parameter operators, which is a key to the proof of the boundedness of these operators.
  • Dawson, Caitlin; Aalto, Daniel; Simko, Juraj; Vainio, Martti; Tervaniemi, Mari (2017)
    Musical experiences and native language are both known to affect auditory processing. The present work aims to disentangle the influences of native language phonology and musicality on behavioral and subcortical sound feature processing in a population of musically diverse Finnish speakers as well as to investigate the specificity of enhancement from musical training. Finnish speakers are highly sensitive to duration cues since in Finnish, vowel and consonant duration determine word meaning. Using a correlational approach with a set of behavioral sound feature discrimination tasks, brainstem recordings, and a musical sophistication questionnaire, we find no evidence for an association between musical sophistication and more precise duration processing in Finnish speakers either in the auditory brainstem response or in behavioral tasks, but they do show an enhanced pitch discrimination compared to Finnish speakers with less musical experience and show greater duration modulation in a complex task. These results are consistent with a ceiling effect set for certain sound features which corresponds to the phonology of the native language, leaving an opportunity for music experience-based enhancement of sound features not explicitly encoded in the language (such as pitch, which is not explicitly encoded in Finnish). Finally, the pattern of duration modulation in more musically sophisticated Finnish speakers suggests integrated feature processing for greater efficiency in a real world musical situation. These results have implications for research into the specificity of plasticity in the auditory system as well as to the effects of interaction of specific language features with musical experiences.
  • Virtala, P.; Huotilainen, M.; Partanen, E.; Tervaniemi, Mari (2014)
  • Zora, Hatice; Riad, Tomas; Ylinen, Sari; Csepe, Valeria (2021)
    Dealing with phonological variations is important for speech processing. This article addresses whether phonological variations introduced by assimilatory processes are compensated for at the pre-lexical or lexical level, and whether the nature of variation and the phonological context influence this process. To this end, Swedish nasal regressive place assimilation was investigated using the mismatch negativity (MMN) component. In nasal regressive assimilation, the coronal nasal assimilates to the place of articulation of a following segment, most clearly with a velar or labial place of articulation, as in utan mej "without me" > [MODIFIER LETTER TRIANGULAR COLONtam mejMODIFIER LETTER TRIANGULAR COLON]. In a passive auditory oddball paradigm, 15 Swedish speakers were presented with Swedish phrases with attested and unattested phonological variations and contexts for nasal assimilation. Attested variations - a coronal-to-labial change as in utan "without" > [MODIFIER LETTER TRIANGULAR COLONtam] - were contrasted with unattested variations - a labial-to-coronal change as in utom "except" > *[MODIFIER LETTER TRIANGULAR COLONtLATIN SMALL LETTER OPEN On] - in appropriate and inappropriate contexts created by mej "me" [mejMODIFIER LETTER TRIANGULAR COLON] and dej "you" [dejMODIFIER LETTER TRIANGULAR COLON]. Given that the MMN amplitude depends on the degree of variation between two stimuli, the MMN responses were expected to indicate to what extent the distance between variants was tolerated by the perceptual system. Since the MMN response reflects not only low-level acoustic processing but also higher-level linguistic processes, the results were predicted to indicate whether listeners process assimilation at the pre-lexical and lexical levels. The results indicated no significant interactions across variations, suggesting that variations in phonological forms do not incur any cost in lexical retrieval; hence such variation is compensated for at the lexical level. However, since the MMN response reached significance only for a labial-to-coronal change in a labial context and for a coronal-to-labial change in a coronal context, the compensation might have been influenced by the nature of variation and the phonological context. It is therefore concluded that while assimilation is compensated for at the lexical level, there is also some influence from pre-lexical processing. The present results reveal not only signal-based perception of phonological units, but also higher-level lexical processing, and are thus able to reconcile the bottom-up and top-down models of speech processing.
  • Seddon, Alistair W. R.; Festi, Daniela; Nieuwkerk, Mayke; Gya, Ragnhild; Hamre, Borge; Kruger, Linn Cecilie; Ostman, Silje A. H.; Robson, T. Matthew (2021)
    Research indicates that phenolic compounds (e.g. para-coumaric acid) found within pollen grains may be useful as a proxy to reconstruct the UV-B radiation received at the Earth's surface in the geological past. However, application of this method to the plant-fossil record currently relies on a series of untested assumptions surrounding the ecological factors driving the response of pollen grains in the contemporary environment. Here, we investigate the relationship of Pinus spp. pollen to UV-B radiation using individuals of five populations sampled from three elevation gradients across Europe. We develop a novel radiation-modelling approach, which allows us to estimate the UV-B radiation dose of individual trees, weighted by different UV-B action spectra. We then use linear mixed-effects modelling to investigate: (a) whether the variations in UV-B-absorbing compounds in Pinus pollen are best described by models using coarser (subgenus) or finer (population) taxonomic levels; and (b) the duration of the period of accumulation of UV-B-absorbing compounds in pollen, ranging from 8 to 28 days. Our results demonstrate an overall positive relationship between para-coumaric acid and UV-B radiation, best described by applying a UV-B-accumulation period spanning 12-19 days. However, we also show clear evidence for population-level factors influencing this relationship across the study locations. Synthesis. Our multidisciplinary approach, which combines expertise from palaeoecology, plant physiology and atmospheric physics, provides clear evidence that pollen-grain chemistry is subject to population-level variations. We suggest that quantitative reconstructions of long-term changes in springtime UV-B radiation are still achievable using fossil reconstructions, but only with careful consideration of the factors leading to pollen representation in sediments. Future improvements are dependent on mechanistic understanding of the local factors which mediate the UV-B response across different populations, and on upscaling knowledge at the plant level to incorporate longer-term chemical variations represented within sediment samples.
  • Leminen, Miika; Leminen, Alina; Smolander, Sini; Arkkila, Eva; Shtyrov, Yury; Laasonen, Marja; Kujala, Teija (2020)
    Formation of neural mechanisms for morphosyntactic processing in young children is still poorly understood. Here, we addressed neural processing and rapid online acquisition of familiar and unfamiliar combinations of morphemes. Three different types of morphologically complex words - derived, inflected, and novel (pseudostem + real suffix) - were presented in a passive listening setting to 16 typically developing 3-4-year old children (as part of a longitudinal Helsinki SLI follow-up study). The mismatch negativity (MMN) component of event-related potentials (ERP), an established index of long-term linguistic memory traces in the brain, was analysed separately for the initial and final periods of the exposure to these items. We found MMN response enhancement for the inflected words towards the end of the recording session, whereas no response change was observed for the derived or novel complex forms. This enhancement indicates rapid build-up of a new memory trace for the combination of real morphemes, suggesting a capacity for online formation of whole-form lexicalized representations as one of the morphological mechanisms in the developing brain. Furthermore, this enhancement increased with age, suggesting the development of automatic morphological processing circuits in the age range of 3-4 years.
  • Piitulainen, Harri; Illman, Mia; Laaksonen, Kristina; Jousmäki, Veikko; Forss, Nina (2018)
    Corticokinematic coherence (CKC) between limb kinematics and magnetoencephalographic (MEG) signals reflects cortical processing of proprioceptive afference. However, it is unclear whether strength of CKC is reproducible across measurement sessions. We thus examined reproducibility of CKC in a follow-up study. Thirteen healthy right-handed volunteers (7 females, 21.7 +/- 4.3 yrs) were measured using MEG in two separate sessions 12.6 +/- 1.3 months apart. The participant was seated and relaxed while his/her dominant or non-dominant index finger was continuously moved at 3 Hz (4 min for each hand) using a pneumatic movement actuator. Finger kinematics were recorded with a 3-axis accelerometer. Coherence was computed between finger acceleration and MEG signals. CKC strength was defined as the peak coherence value at 3 Hz form a single sensor among 40 pre-selected Rolandic gradiometers contralateral to the movement. Pneumatic movement actuator provided stable proprioceptive stimuli and significant CKC responses peaking at the contralateral Rolandic sensors. In the group level, CKC strength did not differ between the sessions in dominant (Day-1 0.40 +/- 0.19 vs. Day-2 0.41 +/- 0.17) or non-dominant (0.35 +/- 0.16 vs. 0.36 +/- 0.17) hand, nor between the hands. Intraclass-correlation coefficient (ICC) values indicated excellent inter-session reproducibility for CKC strength for both dominant (0.86) and non-dominant (0.97) hand. However, some participants showed pronounced inter-session variability in CKC strength, but only for the dominant hand. CKC is a promising tool to study proprioception in long-term longitudinal studies in the group level to follow, e.g., integrity of cortical proprioceptive processing with motor functions after stroke.
  • Xu, Guanglang; Gritsevich, Maria; Peltoniemi, Jouni; Penttilä, Antti; Ihalainen, Olli; Wilkman, Olli; Muinonen, Karri (2020)
    The spectral bidirectional reflectance distribution function (BRDF) maps incident radiation of a surface to its outgoing counterpart at different wavelengths. This function plays a fundamental role in characterizing the various types of earth surfaces. Due to its high dimensionality, the measurements, analysis, and simulation of spectral BRDF are challenging. In this letter, we introduce a new method for processing spectral reflectance using the so-called data-adjacency, i.e., the correlation between adjacent wavelengths and viewing directions. The results show that the benefits of efficient representation, noise reduction, and analysis capability can all be integrated to the data.
  • Lehtonen, Minna; Harrer, Gabor; Wande, Erling; Laine, Matti (2014)