EEG-based effective and functional connectivity for differentiating and predicting altered states of consciousness

How does the brain sustain consciousness? In this thesis, and in the work leading up to it, we provide new computational evidence for the importance of the posterior hot zone on one hand, and for long-distance frontoparietal connectivity on the other, in explaining the contrast between loss of consciousness and in maintaining conscious responsiveness. We adopt a factorial approach in our study, crossing two altered states of consciousness with two analytical methods for measuring changes in brain associated with these altered states. Specifically, we study healthy controls under propofol-anaesthesia and patients suffering from disorders of consciousness (DoC), employing functional and effective electroencephalographic (EEG) connectivity, thereby forming a 2-by-2 study design. We first demonstrate the power of functional EEG connectivity for predicting anaesthetic states in the healthy brain, by building a single multivariate regression model combining phase-lag brain connectivity and behaviour- and power-based dependent measures. We show that baseline alpha- and beta-connectivity, as measured prior to an anaesthetic induction, can predict both behaviour- and power-based measures during the induction and peak unresponsiveness, specifically as measured from the posterior electrodes. Next, we study patients suffering from DoC and show that the alpha-band functional connectivity over the left hemisphere, and graph-theoretic network centrality on the right, significantly predict the patient's clinical diagnosis. Our findings suggest a dissociation between mean spectral connectivity and network properties. Building on these findings, we then turn to dynamic causal modelling (DCM) to estimate modulations in effective brain connectivity due to anaesthesia, in and between the default mode network (DMN), the salience network (SAL), and the central executive network (CEN). Advancing current understanding of anaesthetic-induced LOC, we show evidence for a selective breakdown in the posterior hot zone and in medial feedforward frontoparietal connectivity within the DMN, and of parietal inter-network connectivity linking DMN and CEN. In a novel DCM-based out-of-sample cross-validation, we establish the predictive validity of our models, specifically highlighting frontoparietal connectivity as a generalisable predictor of states of consciousness. Importantly, we demonstrate a generalisation of this predictive power in an unseen dataset from the post-anaesthetic recovery state. Finally, we again use DCM to investigate changes in the effective connectivity between DoC patients and healthy controls within the DMN. Specifically, we show that the key difference between healthy controls or conscious patients and completely unresponsive patients is a reduction in left-hemispheric backward frontoparietal connectivity. Finally, with out-of-sample cross-validation, we show that left-hemispheric frontoparietal connectivity can not only distinguish patient groups from each other, it can also generalise to an unseen data subset collected from seemingly unresponsive patients who show evidence of consciousness when assessed with functional neuroimaging. This suggests that effective EEG connectivity can be used to identify covertly aware patients who seem behaviourally unresponsive. Overall, this thesis provides novel insights into the brain dynamics underlying transitions between altered states of consciousness and highlights the value of tracking these dynamics in a clinical context. DCM, though computationally more expensive, can accurately predict states of consciousness and provide causal explanations of the brain dynamics that cannot be inferred from functional connectivity alone. Functional connectivity, though correlational, is still an accurate predictive tool of altered states of consciousness. With clinically challenging, ambiguous cases like potentially covertly aware patients, we propose that the causal explanations and accurate predictions of DCM modelling could outweigh the computational complexity

The relationship between musical training and the processing of audiovisual correspondences: Evidence from a reaction time task

Numerous studies have reported both cortical and functional changes for visual, tactile, and auditory brain areas in musicians, which have been attributed to long-term training induced neuroplasticity. Previous investigations have reported advantages for musicians in multisensory processing at the behavioural level, however, multisensory integration with tasks requiring higher level cognitive processing has not yet been extensively studied. Here, we investigated the association between musical expertise and the processing of audiovisual crossmodal correspondences in a decision reaction-time task. The visual display varied in three dimensions (elevation, symbolic and non-symbolic magnitude), while the auditory stimulus varied in pitch. Congruency was based on a set of newly learned abstract rules: “The higher the spatial elevation, the higher the tone”, “the more dots presented, the higher the tone”, and “the higher the number presented, the higher the tone”, and accuracy and reaction times were recorded. Musicians were significantly more accurate in their responses than non-musicians, suggesting an association between long-term musical training and audiovisual integration. Contrary to what was hypothesized, no differences in reaction times were found. The musicians’ advantage on accuracy was also observed for rule-based congruency in seemingly unrelated stimuli (pitch-magnitude). These results suggest an interaction between implicit and explicit processing–as reflected on reaction times and accuracy, respectively. This advantage was generalised on congruency in otherwise unrelated stimuli (pitch-magnitude pairs), suggesting an advantage on processes requiring higher order cognitive functions. The results support the notion that accuracy and latency measures may reflect different processes

Lateral frontoparietal effective connectivity differentiates and predicts state of consciousness in a cohort of patients with traumatic disorders of consciousness

Neuroimaging studies have suggested an important role for the default mode network (DMN) in disorders of consciousness (DoC). However, the extent to which DMN connectivity can discriminate DoC states–unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS)–is less evident. Particularly, it is unclear whether effective DMN connectivity, as measured indirectly with dynamic causal modelling (DCM) of resting EEG can disentangle UWS from healthy controls and from patients considered conscious (MCS+). Crucially, this extends to UWS patients with potentially “covert” awareness (minimally conscious star, MCS*) indexed by voluntary brain activity in conjunction with partially preserved frontoparietal metabolism as measured with positron emission tomography (PET+ diagnosis; in contrast to PET- diagnosis with complete frontoparietal hypometabolism). Here, we address this gap by using DCM of EEG data acquired from patients with traumatic brain injury in 11 UWS (6 PET- and 5 PET+) and in 12 MCS+ (11 PET+ and 1 PET-), alongside with 11 healthy controls. We provide evidence for a key difference in left frontoparietal connectivity when contrasting UWS PET- with MCS+ patients and healthy controls. Next, in a leave-one-subject-out cross-validation, we tested the classification performance of the DCM models demonstrating that connectivity between medial prefrontal and left parietal sources reliably discriminates UWS PET- from MCS+ patients and controls. Finally, we illustrate that these models generalize to an unseen dataset: models trained to discriminate UWS PET- from MCS+ and controls, classify MCS* patients as conscious subjects with high posterior probability (pp > .92). These results identify specific alterations in the DMN after severe brain injury and highlight the clinical utility of EEG-based effective connectivity for identifying patients with potential covert awareness

How hot is the hot zone? Computational modelling clarifies the role of parietal and frontoparietal connectivity during anaesthetic-induced loss of consciousness

In recent years, specific cortical networks have been proposed to be crucial for sustaining consciousness, including the posterior hot zone and frontoparietal resting state networks (RSN). Here, we computationally evaluate the relative contributions of three RSNs – the default mode network (DMN), the salience network (SAL), and the central executive network (CEN) – to consciousness and its loss during propofol anaesthesia. Specifically, we use dynamic causal modelling (DCM) of 10 minutes of high-density EEG recordings (N = 10, 4 males) obtained during behavioural responsiveness, unconsciousness and post-anaesthetic recovery to characterise differences in effective connectivity within frontal areas, the posterior ‘hot zone’, frontoparietal connections, and between-RSN connections. We estimate – for the first time – a large DCM model (LAR) of resting EEG, combining the three RSNs into a rich club of interconnectivity. Consistent with the hot zone theory, our findings demonstrate reductions in inter-RSN connectivity in the parietal cortex. Within the DMN itself, the strongest reductions are in feed-forward frontoparietal and parietal connections at the precuneus node. Within the SAL and CEN, loss of consciousness generates small increases in bidirectional connectivity. Using novel DCM leave-one-out cross-validation, we show that the most consistent out-of-sample predictions of the state of consciousness come from a key set of frontoparietal connections. This finding also generalises to unseen data collected during post-anaesthetic recovery. Our findings provide new, computational evidence for the importance of the posterior hot zone in explaining the loss of consciousness, highlighting also the distinct role of frontoparietal connectivity in underpinning conscious responsiveness, and consequently, suggest a dissociation between the mechanisms most prominently associated with explaining the contrast between conscious awareness and unconsciousness, and those maintaining consciousness

The relationship between musical training and the processing of audiovisual correspondences: Evidence from a reaction time task.

Numerous studies have reported both cortical and functional changes for visual, tactile, and auditory brain areas in musicians, which have been attributed to long-term training induced neuroplasticity. Previous investigations have reported advantages for musicians in multisensory processing at the behavioural level, however, multisensory integration with tasks requiring higher level cognitive processing has not yet been extensively studied. Here, we investigated the association between musical expertise and the processing of audiovisual crossmodal correspondences in a decision reaction-time task. The visual display varied in three dimensions (elevation, symbolic and non-symbolic magnitude), while the auditory stimulus varied in pitch. Congruency was based on a set of newly learned abstract rules: "The higher the spatial elevation, the higher the tone", "the more dots presented, the higher the tone", and "the higher the number presented, the higher the tone", and accuracy and reaction times were recorded. Musicians were significantly more accurate in their responses than non-musicians, suggesting an association between long-term musical training and audiovisual integration. Contrary to what was hypothesized, no differences in reaction times were found. The musicians' advantage on accuracy was also observed for rule-based congruency in seemingly unrelated stimuli (pitch-magnitude). These results suggest an interaction between implicit and explicit processing-as reflected on reaction times and accuracy, respectively. This advantage was generalised on congruency in otherwise unrelated stimuli (pitch-magnitude pairs), suggesting an advantage on processes requiring higher order cognitive functions. The results support the notion that accuracy and latency measures may reflect different processes

The relationship between musical training and the processing of audiovisual correspondences: Evidence from a reaction time task

Numerous studies have reported both cortical and functional changes for visual, tactile, and auditory brain areas in musicians, which have been attributed to long-term training induced neuroplasticity. Previous investigations have reported advantages for musicians in multisensory processing at the behavioural level, however, multisensory integration with tasks requiring higher level cognitive processing has not yet been extensively studied. Here, we investigated the association between musical expertise and the processing of audiovisual crossmodal correspondences in a decision reaction-time task. The visual display varied in three dimensions (elevation, symbolic and non-symbolic magnitude), while the auditory stimulus varied in pitch. Congruency was based on a set of newly learned abstract rules: “The higher the spatial elevation, the higher the tone”, “the more dots presented, the higher the tone”, and “the higher the number presented, the higher the tone”, and accuracy and reaction times were recorded. Musicians were significantly more accurate in their responses than non-musicians, suggesting an association between long-term musical training and audiovisual integration. Contrary to what was hypothesized, no differences in reaction times were found. The musicians’ advantage on accuracy was also observed for rule-based congruency in seemingly unrelated stimuli (pitch-magnitude). These results suggest an interaction between implicit and explicit processing–as reflected on reaction times and accuracy, respectively. This advantage was generalised on congruency in otherwise unrelated stimuli (pitch-magnitude pairs), suggesting an advantage on processes requiring higher order cognitive functions. The results support the notion that accuracy and latency measures may reflect different processes

The effect of musical training on the processing of audiovisual correspondences: Evidence from a reaction time task

Numerous studies have reported both cortical and functional changes for visual, tactile, and auditory brain areas in musicians, which have been attributed to long-term training induced neuroplasticity. Previous investigations have reported advantages for musicians in multisensory processing at the behavioural level, however, multisensory integration with tasks requiring higher level cognitive processing has not yet been extensively studied. Here, we investigated the effects of musical expertise on the processing of audiovisual crossmodal correspondences in a decision reaction-time task. The visual display varied in three dimensions (elevation, symbolic and non-symbolic magnitude), while the auditory stimulus varied in pitch. Congruency was based on a set of newly learned abstract rules: “The higher the spatial elevation, the higher the tone”, “the more dots presented, the higher the tone”, and “the higher the number presented, the higher the tone”, and accuracy and reaction times were recorded. Musicians were significantly more accurate in their responses than non-musicians, suggesting long-term training effects on audiovisual integration. Contrary to what was hypothesized, no differences in reaction times were found. The musicians’ advantage on accuracy was also observed for rule-based congruency in seemingly unrelated stimuli (pitch-magnitude). These results suggest an interaction between implicit and explicit processing – as reflected on reaction times and accuracy, respectively. This advantage was generalised on congruency in otherwise unrelated stimuli (pitch-magnitude pairs), suggesting an advantage on processes requiring higher order cognitive functions. The results support the notion that accuracy and latency measures may reflect different processes

Metsätuhot vuonna 2019

Valtakunnan metsien 13. inventoinnin mukaan metsikön laatua alentavien tuhojen osuus oli vuonna 2019 vähentynyt vuoteen 2018 verrattuna noin 0,15 miljoonaa hehtaaria. Kaikkiaan tuhoja esiintyi vajaat 5 miljoonalla hehtaarilla. Abioottisista tuhoista erityisesti lumituhot lisääntyivät ja eläinperäisistä tuhoista hirvituhot vähenivät. Koko maan tasolla lumi- ja hirvituhot ovat edelleen ylivoimaisesti yleisimpiä metsikön laatua alentavia tunnistettuja tuhoja, kuten ovat myös lahottajasienet, tuuli ja tervasroso. Maakunnittain tarkasteltuna lumituhot olivat suhteellisesti pahimpia Lapissa, Kainuussa ja Pohjois-Pohjanmaalla sekä tuulituhot Pirkanmaalla. Pohjanmaan mäntypistiäistuhot olivat laantumaan päin. Luke jatkoi yhdessä Metsäkeskuksen ja metsänhoitoyhdistysten kanssa vuonna 2012 aloitettua kirjanpainajakantojen seurantaa feromonipyydyksin 36 paikkakunnalla Etelä-Suomessa. Kirjanpainajan ns. epidemian riskiraja ylittyi kahdeksalla paikkakunnalla; Vihti, Pornainen, Mäntsälä, Lapinjärvi, Elimäki, Orimattila, Punkalaidun ja Loimaa. Ennätyslämmin kesä 2018 ei aiheuttanut laajoja tuhoja Suomessa vuonna 2019. Metsäkeskukselle ilmoitettiin vuonna 2019 yhteensä 450 ha hyönteistuhon vuoksi hakattavaa pinta-alaa, josta määrästä kaikki ei kokonaisuudessaan ollut kirjanpainajan vioittamaa puustoa. Kirjanpainajien sukuun kuuluva mäntyihin iskeytyvä okakaarnakuoriainen on yleistynyt Etelä-Suomessa viime vuosina. Kesällä 2019 Maskussa merenrantakalliotontilla ruskettui ja kuoli noin kaksikymmentä varttunutta mäntyä muutamassa viikossa. Tuhomäntyjen oksisto ja runkojen yläosat olivat kauttaaltaan okakaarnakuoriaisten valtaamia. Syitä tuholaisen äkilliseen runsastumiseen Suomessa ei varmuudella tiedetä. Laji saattaa hyötyä kesän helle- ja kuivuusjaksoista tai iskeytyä muiden tuhonaiheuttajien heikentämiin puihin. Maskun tuhopuista eristettiin okakaarnakuoriaisten mukanaan tuomia sinistäjäsieniä jatkokokeisiin, joista raportoidaan myöhemmin erikseen. Luke aloitti havununnan yksilömäärien seurannan feromonipyydysten avulla vuonna 2018, jota laajennettiin vuonna 2019. Runsaimmat perhossaaliit saatiin Kaakkois- ja Lounais-Suomesta. Suurimmillaan saalismäärät olivat sellaisia, joiden esim. Keski-Euroopassa on todettu olevan tuhoriskiä lisääviä. Seurantaa on aiheellista pitää yllä jatkossakin kannan kehittymisen ja pohjoiseen leviämisen ennustamiseksi. Lumimittarin toukat aiheuttivat tuhoja koivikoissa Etelä- ja Keski-Suomessa. Vuonna 2019 voimakas syönti kohdistui pääasiassa harvennettuihin 30–50-vuotiaisiin pellolle istutettuihin rauduskoivikoihin. Kuusella pihkavuotoa, koroja ja latva/oksakuolemaa aiheuttavaa mustakoroa havaittiin erityisesti Päijät-Hämeen alueella. Tauti varmistettiin myös Kemiön saaresta, mistä mustakoroa ei ole aiemmin raportoitu. Pihdan korotaudin uusia esiintymiä varmistettiin vuonna 2019 Helsingistä, Järvenpäästä ja Kauniaisista. Sienen sairastuttamat puut olivat harmaapihtoja, joissa esiintyi pihkavuotoisia runko- ja oksakoroja, harsuuntumista sekä oksien kuivumista. Lukessa on selvitetty kuuselle osittaisen juurikäävänkestävyyden aiheuttavan Lar3B-alleelin vaikutusta juurikäävän kasvuun. Ensimmäisten tulosten mukaan juurikäävälle kestävyyttä aiheuttava Lar3B- geenimuoto esiintyy noin joka kolmannessa eteläisimmän Suomen jalostuspopulaatioon kuuluvassa kuusessa. Lopella sijaitsevalla tyvitervastautikohteella on selvitetty taudin siirtymistä istutusmännikköön yhdeksän vuoden ajan. Taimikossa havaittiin ensimmäiset juurikäävän tappamat taimet viisi vuotta istutuksen jälkeen. Yksi edellisestä puusukupolvesta siirtynyt juurikääpäyksilö tappoi enimmillään 38 seuraavan puusukupolven mäntyä. Pesäkkeiden laajenemisen seurauksena taimikko on aukkoinen eikä tuhon laantumisesta näy vielä merkkejä. Juurikääpätuhojen tunnistamisesta ja torjunnasta valmistui opas yhteistyössä Metsäkeskuksen kanssa. Aapeli-myrskyn aiheuttama puustotuho Ahvenanmaalla tammikuussa 2019 oli VMI-mittausten mukaan 1,1 miljoonaa kuutiometriä. Tuhopuuston määrä oli noin 2,5-kertainen verrattuna Ahvenanmaan puuston vuotuiseen kasvuun ja 3,5-kertainen verrattuna viime vuosien vuotuiseen poistumaan. Hirvikanta ja yksityisille metsänomistajille korvatut hirvituhot olivat laskusuunnassa. Mäntytaimikoiden määrän väheneminen ja tuhojen ilmeneminen kuusivaltaisilla alueilla merkittävässä määrin myös varttuneissa puustoissa osoittaa, että tuhonäkökulmasta hirvien määrän suhteen sietää viime vuosien laskusuunnasta huolimatta olla hereillä. Luken vuoden 2019 myyräseurannat kertovat, että myyrät olivat syksyllä kannanvaihtelunsa huippuvaiheessa Itä-Suomessa, ylimmässä Lapissa ja laajalti myös Etelä-Suomessa. Keskisessä Suomessa ja laajalti Pohjanmaan pohjoisimmissa osissa ja Metsä-Lapissa myyräkannat ovat runsastumassa kohti huippua vuonna 2020. Pohjanmaan myyräkannat olivat alhaiset. Paikallisia tuhoja esiintyi keväällä 2019 Oulun ja Kemin seuduilla. Siemenviljelysten käpy- ja siementuhoja tutkittiin MMM:n rahoittamassa Metsäpuiden siementuotannon kehittäminen (MESIKE) -projektissa. Käpykoisa, kuusenkäpykärpänen, kuusenkäpykääriäinen ja kuusentuomiruoste vähensivät vaihtelevassa määrin kuusenkäpyjen siementuotantoa. Käpyruosteista kuusentuomiruosteen, kuusentalvikkiruosteen ja kuusensuopursuruosteen itiötuotantoa tutkittiin usealla siemenviljelmällä. Pohjois-Pohjanmaalla kuusensuopursuruostetta esiintyi erittäin vähän, eikä uutta versosurmaa männyissä havaittu kesällä 2019. Loppukesästä esiintyi runsaasti koivunlehtilaikkutautia, mutta koivunruostetta ja uutta tervasrosotuhoa männyissä vain vähän. Kuivan kesän seurauksena männyn punavyökaristetta esiintyi vähemmän edellisiin vuosiin verrattuna. Ruskopilkkukaristetta esiintyi taimikoissa yleisesti aina Kuusamon korkeudelle saakka. Männyn harmaakaristetta esiintyi lievänä ja voimakkaampana lähinnä yksittäisissä puissa