Browsing by Subject "functional magnetic resonance imaging"

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  • Kauppi, Jukka-Pekka; Pajula, Juha; Tohka, Jussi (2014)
    In the inter-subject correlation (ISC) based analysis of the functional magnetic resonance imaging (fMRI) data, the extent of shared processing across subjects during the experiment is determined by calculating correlation coefficients between the fMRI time series of the subjects in the corresponding brain locations. This implies that ISC can be used to analyze fMRI data without explicitly modeling the stimulus and thus ISC is a potential method to analyze fMRI data acquired under complex naturalistic stimuli. Despite of the suitability of ISC based approach to analyze complex fMRI data, no generic software tools have been made available for this purpose, limiting a widespread use of ISC based analysis techniques among neuroimaging community. In this paper, we present a graphical user interface (GUI) based software package, ISC Toolbox, implemented in Matlab for computing various ISC based analyses. Many advanced computations such as comparison of ISCs between different stimuli, time window ISC, and inter-subject phase synchronization are supported by the toolbox. The analyses are coupled with resampling based statistical inference. The ISC based analyses are data and computation intensive and the ISC toolbox is equipped with mechanisms to execute the parallel computations in a cluster environment automatically and with an automatic detection of the cluster environment in use. Currently, SGE-based (Oracle Grid Engine, Son of a Grid Engine, or Open Grid Scheduler) and Slurm environments are supported. In this paper, we present a detailed account on the methods behind the ISC Toolbox, the implementation of the toolbox and demonstrate the possible use of the toolbox by summarizing selected example applications. We also report the computation time experiments both using a single desktop computer and two grid environments demonstrating that parallelization effectively reduces the computing time.
  • Mäntylä, Teemu; Nummenmaa, Lauri; Rikandi, Eva; Lindgren, Maija; Kieseppä, Tuula; Hari, Riitta; Suvisaari, Jaana; Raij, Tuukka T. (2018)
    BACKGROUND: Functional magnetic resonance imaging studies of psychotic disorders have reported both hypoactivity and hyperactivity in numerous brain regions. In line with the dysconnection hypothesis, these regions include cortical integrative hub regions. However, most earlier studies focused on a single cognitive function at a time, assessed by delivering artificial stimuli to patients with chronic psychosis. Thus, it remains unresolved whether these findings are present already in early psychosis and whether they translate to real-life-like conditions that require multisensory processing and integration. METHODS: Scenes from the movie Alice in Wonderland (2010) were shown to 51 patients with first-episode psychosis (16 women) and 32 community-based control subjects (17 women) during 3T functional magnetic resonance imaging. We compared intersubject correlation, a measure of similarity of brain signal time courses in each voxel, between the groups. We also quantified the hubness as the number of connections each region has. RESULTS: Intersubject correlation was significantly lower in patients with first-episode psychosis than in control subjects in the medial and lateral prefrontal, cingulate, precuneal, and parietotemporal regions, including the default mode network. Regional magnitude of between-group difference in intersubject correlation was associated with the hubness. CONCLUSIONS: Our findings provide novel evidence for the dysconnection hypothesis by showing that during complex real-life-like stimulation, the most prominent functional alterations in psychotic disorders relate to integrative brain functions. Presence of such abnormalities in first-episode psychosis rules out long-term effects of illness or medication. These methods can be used in further studies to map widespread hub alterations in a single functional magnetic resonance imaging session and link them to potential downstream and upstream pathways.
  • Mikkola, Katri (Helsingfors universitet, 2016)
    Attention-deficit/hyperactivity disorder (ADHD) is a pervasive neurodevelopmental disorder of executive functions, which affects the social, occupational, educational, and personal life of the individuals concerned. The main characteristics of this disorder are age inappropriate inattention, impulsivity and hyperactivity. The research on adult ADHD is still scarce, especially concerning the neural networks of attention. Childhood ADHD has been associated with impairment in two of the attentional network subsystems alerting and executive control, leaving the third subsystem, orienting of attention, intact. Research on adult ADHD and the subsystems of attentional network is contradicting. The aim of this study was to investigate neural activation of these attentional networks during highly demanding attentional tasks in adults with ADHD. The first hypothesis was that the ADHD group have decreased activity in the frontoparietal network during orienting of attention in contrast to the control group. The second hypothesis was that the ADHD group have decreased activity in the dorsolateral prefrontal cortex, anterior cingulate gyrus, and precuneus during divided attention in contrast to the control group. Both the ADHD group and the control group included 16 participants, aged 25 – 56 across all participants, whose brain activation was measured with functional magnetic resonance imaging during the attentional tasks. The tasks included divided and selective attention. Both conditions included task-irrelevant novel distractors. The results supported both hypotheses. The ADHD group had decreased brain activity in the frontoparietal network during top-down controlled and bottom-up triggered attention. Decreased activation in the dorsolateral prefrontal cortex, anterior cingulate gyrus and precuneus was observed during divided attention in the ADHD group. Furthermore, the default-mode network was hyperactivated in the ADHD group. Activation of this network has been related to increasing task demands and failure of maintaining an alert state. Thus, adult ADHD seems to associate with abnormally functioning attention networks. Moreover, the results indicated that in addition to dysfunctional alerting and executive control, adults with ADHD have also impaired orienting of attention. These dysfunctional attentional networks may have a connection with the inattentive symptoms of adult ADHD.
  • Nuortimo, Antti (Helsingfors universitet, 2015)
    Aims. Understanding of emotional processing is important for the research of mental states. A better understanding of the visual system would facilitate understanding the functioning of the entire brain. Emotions are processed in a complex neural network. The aim of the present Master's thesis is to explore the effective connectivity of the occipital face areas (OFAs) and fusiform face areas (FFAs) during the processing of visual stimuli eliciting negative emotion. Methods. The subjects (n = 16) were young adult male students. Negative and neutral emotion were elicited using visual stimuli from the International Affective Picture System (IAPS). Functional magnetic resonance imaging (fMRI) data were acquired using an MRI scanner. The fMRI data were preprocessed and analyzed using SPM8 software. In order to proceed to the psycho-physiological interaction (PPI) analyses, imaging sessions were concatenated and entered into the analyses as one single session. Subject-level model comprised the following regressors: negative emotion, neutral emotion, baseline and a binary regressor for each functional session to model session effects. An effects of interest F-contrast and a negative emotion t-contrast were defined. Spherical volumes of interest (VOIs) were computed for each subject for the left and the right occipital face area (OFA) and for the left and the right fusiform face area (FFA). The PPI variables were computed for each statistically significant VOI. A standard PPI model was defined. Each of the 4 VOIs was used as source region for all other VOIs. A group-level whole brain analysis was done for each PPI source VOI. Group-level VOI analyses were conducted for all PPI source VOIs. Results and conclusions. In the whole brain analyses statistically significant group-level PPIs were found in the following brain regions: left cuneus, right middle occipital gyrus, right and left inferior occipital gyrus, left lingual gyrus, and the left culmen. VOI analyses demonstrated the strong connectivity in the network consisting of the right OFA and left and right FFAs. Negative emotional content enhances effective connectivity in the bilateral OFA-FFA network.
  • Saalasti, Satu; Alho, Jussi; Bar, Moshe; Glerean, Enrico; Honkela, Timo; Kauppila, Minna; Sams, Mikko; Jääskeläinen, Iiro P. (2019)
    Introduction: When listening to a narrative, the verbal expressions translate into meanings and flow of mental imagery. However, the same narrative can be heard quite differently based on differences in listeners' previous experiences and knowledge. We capitalized on such differences to disclose brain regions that support transformation of narrative into individualized propositional meanings and associated mental imagery by analyzing brain activity associated with behaviorally assessed individual meanings elicited by a narrative. Methods: Sixteen right-handed female subjects were instructed to list words that best described what had come to their minds while listening to an eight-minute narrative during functional magnetic resonance imaging (fMRI). The fMRI data were analyzed by calculating voxel-wise intersubject correlation (ISC) values. We used latent semantic analysis (LSA) enhanced with Wordnet knowledge to measure semantic similarity of the produced words between subjects. Finally, we predicted the ISC with the semantic similarity using representational similarity analysis. Results: We found that semantic similarity in these word listings between subjects, estimated using LSA combined with WordNet knowledge, predicting similarities in brain hemodynamic activity. Subject pairs whose individual semantics were similar also exhibited similar brain activity in the bilateral supramarginal and angular gyrus of the inferior parietal lobe, and in the occipital pole. Conclusions: Our results demonstrate, using a novel method to measure interindividual differences in semantics, brain mechanisms giving rise to semantics and associated imagery during narrative listening. During listening to a captivating narrative, the inferior parietal lobe and early visual cortical areas seem, thus, to support elicitation of individual meanings and flow of mental imagery.
  • Hakonen, Maria; May, Patrick J. C.; Jaaskelainen, Iiro P.; Jokinen, Emma; Sams, Mikko; Tiitinen, Hannu (2017)
    Introduction: We examined which brain areas are involved in the comprehension of acoustically distorted speech using an experimental paradigm where the same distorted sentence can be perceived at different levels of intelligibility. This change in intelligibility occurs via a single intervening presentation of the intact version of the sentence, and the effect lasts at least on the order of minutes. Since the acoustic structure of the distorted stimulus is kept fixed and only intelligibility is varied, this allows one to study brain activity related to speech comprehension specifically. Methods: In a functional magnetic resonance imaging (fMRI) experiment, a stimulus set contained a block of six distorted sentences. This was followed by the intact counterparts of the sentences, after which the sentences were presented in distorted form again. A total of 18 such sets were presented to 20 human subjects. Results: The blood oxygenation level dependent (BOLD)-responses elicited by the distorted sentences which came after the disambiguating, intact sentences were contrasted with the responses to the sentences presented before disambiguation. This revealed increased activity in the bilateral frontal pole, the dorsal anterior cingulate/paracingulate cortex, and the right frontal operculum. Decreased BOLD responses were observed in the posterior insula, Heschl's gyrus, and the posterior superior temporal sulcus. Conclusions: The brain areas that showed BOLD-enhancement for increased sentence comprehension have been associated with executive functions and with the mapping of incoming sensory information to representations stored in episodic memory. Thus, the comprehension of acoustically distorted speech may be associated with the engagement of memory-related subsystems. Further, activity in the primary auditory cortex was modulated by prior experience, possibly in a predictive coding framework. Our results suggest that memory biases the perception of ambiguous sensory information toward interpretations that have the highest probability to be correct based on previous experience.
  • Renvall, Hanna; Seol, Jaeho; Tuominen, Riku; Sorger, Bettina; Riecke, Lars; Salmelin, Riitta (2021)
    Rapid recognition and categorization of sounds are essential for humans and animals alike, both for understanding and reacting to our surroundings and for daily communication and social interaction. For humans, perception of speech sounds is of crucial importance. In real life, this task is complicated by the presence of a multitude of meaningful non-speech sounds. The present behavioural, magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) study was set out to address how attention to speech versus attention to natural non-speech sounds within complex auditory scenes influences cortical processing. The stimuli were superimpositions of spoken words and environmental sounds, with parametric variation of the speech-to-environmental sound intensity ratio. The participants' task was to detect a repetition in either the speech or the environmental sound. We found that specifically when participants attended to speech within the superimposed stimuli, higher speech-to-environmental sound ratios resulted in shorter sustained MEG responses and stronger BOLD fMRI signals especially in the left supratemporal auditory cortex and in improved behavioural performance. No such effects of speech-to-environmental sound ratio were observed when participants attended to the environmental sound part within the exact same stimuli. These findings suggest stronger saliency of speech compared with other meaningful sounds during processing of natural auditory scenes, likely linked to speech-specific top-down and bottom-up mechanisms activated during speech perception that are needed for tracking speech in real-life-like auditory environments.
  • Rinne, Teemu; Koistinen, Sonja; Salonen, Oili; Alho, Kimmo (2009)
    "The functional organization of auditory cortex (AC) is still poorly understood. Previous studies suggest segregation of auditory processing streams for spatial and nonspatial information located in the posterior and anterior AC, respectively (Rauschecker and Tian, 2000; Arnott et al., 2004; Lomber and Malhotra, 2008). Furthermore, previous studies have shown that active listening tasks strongly modulate AC activations (Petkov et al., 2004; Fritz et al., 2005; Polley et al., 2006). However, the task dependence of AC activations has not been systematically investigated. In the present study, we applied high-resolution functional magnetic resonance imaging of the AC and adjacent areas to compare activations during pitch discrimination and n-back pitch memory tasks that were varied parametrically in difficulty. We found that anterior AC activations were increased during discrimination but not during memory tasks, while activations in the inferior parietal lobule posterior to the AC were enhanced during memory tasks but not during discrimination. We also found that wide areas of the anterior AC and anterior insula were strongly deactivated during the pitch memory tasks. While these results are consistent with the proposition that the anterior and posterior AC belong to functionally separate auditory processing streams, our results show that this division is present also between tasks using spatially invariant sounds. Together, our results indicate that activations of human AC are strongly dependent on the characteristics of the behavioral task."