Browsing by master's degree program "Master's Programme in Neuroscience"

The vagus nerve is the longest nerve of the autonomic nervous system. It innervates, among other organs, the stomach, the lungs and the heart, and it reaches several areas of the brain, including the locus coeruleus and the amygdala. The invasive stimulation of this nerve (vagus nerve stimulation, or VNS) is a currently used method for the treatment of refractory epilepsy and pharmaco-resistant depression (Englot et al. 2011; O’Reardon et al., 2006), but the impact that this technique might have on the brain physiology and functions is still under investigation. Various studies (Frangos et al., 2015; Yakunina et al., 2016; Hansen, 2019) have shown that VNS increases noradrenaline production in the brain, a neurotransmitter that is involved in several cognitive processes, such as sleep and mood control. Furthermore, in a study on patients with epilepsy, by Sun et al. in 2017, VNS appeared to have a clear effect on working memory and emotion-attention interaction. Nevertheless, VNS presents all the risks and potential complications that characterize invasive procedures requiring surgery. Therefore, research is now focusing on safer, non-invasive alternatives, such as transcutaneous vagus nerve stimulation (tVNS). This technique allows to stimulate the nerve through its sensory fibres, located in the cymba and tragus of the ear. The scope of the present study was to see whether tVNS would have the same effects on cognitive and affective functions as VNS. The sample for this single blind placebo-controlled study was composed of 30 healthy subjects between 18 and 45 years old. Exclusion criteria included a history of psychiatric, neurological or cardiovascular diseases. All subjects were asked to complete a computer-based task, the Executive Reaction Times-Test. Throughout the test the subjects alternately received an active or a placebo stimulation, and their brain activity was recorded for the whole duration of the test using a 64-channel EEG cap. The Executive-Reaction Times-Test was chosen for this study because it allows to test multiple executive functions simultaneously. The subjects were presented with a series of stimuli on a screen and were asked to react as fast and accurately as possible to “Go” signals, and to refrain from responding when “NoGo” signals appeared. The test started with a triangle pointing either up- or downwards, followed by a brief pause and a traffic light image. The traffic light showed either a red or a green light and included an emotional distractor in the form of a spider or a flower. The red and green lights were alternately used as “Go” or “NoGo” signals, and the rule changed at each test block. In order to complete the task, subjects needed to keep the image of the triangle in their working memory, stay focused on the stimuli and be ready to react or be able to inhibit any responses, thus several main executive functions are being tested: inhibitory control, working memory, attention and emotion-attention interaction. Active stimulation was delivered through clip electrodes that were attached to the tragus of the left ear, whereas placebo stimulation was delivered through clip electrodes that were attached to the left ear lobe. The subjects were not aware of the difference between the two locations. Only the data of 18 subjects was used for the results analysis, because of technical difficulties with the EEG data (some recordings were too noisy, some presented flat channels). The behavioural data was divided into reaction times and errors, which were separately analysed. The EEG data was used to extract the amplitudes of the ERP peaks N2 and P3. The former is a negative peak visible at 200-350ms; the latter is a positive peak visible at 300-500ms. Previous studies have shown the peaks to be associated with response conflict and inhibition (Falkenstein et al., 1999; Donkers et al., 2004; Smith et al., 2013). The behavioural data analysis did not show any significant effect of stimulation on reaction times or error amounts. The ERP analysis, instead, returned interesting results. We observed a main effect of stimulation (p=0.04) in “NoGo” conditions. There was a significant reduction in the N2P3 amplitude and the N2 amplitude in “NoGo” conditions, with active stimulation compared to placebo. These results seem to suggest that with tVNS, fewer cognitive resources are allocated to resolve the inhibitory task, without worsening the subjects’ performance. The lack of significance in the behavioural results might have been due to a ceiling effect, with the Executive Reaction Times-test being too easy for our sample. Overall, the number of errors was too low to conduct a reliable statistical analysis. Nevertheless, the effects we observed on brain physiology would suggest that further research is needed to explore the actual impact of tVNS on cognitive and affective functions.

This thesis explores the relationship between neuropathic pain and the circadian clock through the investigation of GSK4112 administration to a mouse model of neuropathic pain. Neuropathic pain, arising from a lesion or disease of the somatosensory system, historically posed treatment challenges due to narrow research approaches focusing solely on the pain system. Recent insights highlight connections between neuropathic pain and the circadian clock, including circadian rhythmicity in neuropathic pain and shared genetic expressions and pathways. The study aimed to investigate the effects of GSK4112, an agonist of Rev-erbα and a small molecule modulator of the circadian clock. This was done through a blinded experiment design in mice modelling neuropathic pain induced by spared nerve injury. The study involved tracking locomotive activity to assess alterations in circadian rhythm and infer effects on the circadian clock. In addition, behavioural tests that measure mechanical and thermal sensitivity were employed to investigate the potential analgesic effects of GSK4112 administration. As a result, no change to circadian activity or mechanical and thermal sensitivity was observed as a result of GSK4112 administration to mice with spared nerve injury.

Neural Oscillations at large-scale local and global neural synchrony levels can be detected at the scalp using electroencephalography. This neural activity presents itself in a varied range of frequencies referred to as ‘Brain Waves’. These frequency bands have cognitive significance and have been implicated in several neural functions due to its important role in communicating with functionally-similar but spatially-distinct brain regions. Frontal Asymmetry is the difference in activity between the right and left hemispheres in frontal areas of the brain recorded via EEG and is seen to be a strong indicator of emotional states. Specifically, approach and withdrawal motivation which have been associated with positive and negative emotions respectively. Using a combination of behavioural and physiological methods in measuring preference and responses gives us an accurate representation of the participant responses. In this study, three tests were conducted during a continuous EEG recording. Test 1: The implication of inducing a positive mood before the onset of stimulus line-up and the extent of its effect on emotions and alpha asymmetry is not extensively studied. In this test, we employed the use of an instrumental soundscape for one experimental group before beginning the stimulus presentation to test this effect against a ‘silent’ control group. Test 2: This test aims to compare the participants’ physiological measures (EEG) and behavioural self-reports to audio advertisement stimuli consisting of different categories of music: ‘Brand music’ vs. ‘Campaign’ music or ‘No music’ Controls. Test 3: There is ambiguity in research regarding how frontal alpha asymmetry as measured by EEG and self-report preferences might change with changing the format of the advertisement to: only Audio, Audiovisual and Silent videos. There has been contradictory evidence regarding the impact of music on an individual’s emotions and consequent memory and decision-making. This thesis delves into these questions through the post-study behavioural test and simple binary choice paradigm that measure the above-mentioned in relation with the stimuli presented to participants. Our results did not show a significant difference in frontal asymmetry in the stimulus presentation across the three tests conducted during EEG recording. The behavioural data however indicated significant preference in behavioural self-report ratings for Brand Music- associated stimuli in Test 2 and for Audiovisual advertisement stimuli in Test 3. Results also revealed a significant correlation between ratings given to a stimulus and post-study memorability. The final binary choice paradigm test indicated higher preference to products related to stimulus presentation (‘advertised’ brand) vs similar products not related to the presented stimulus (‘non-advertised’ brand). We anticipate that these results will further help us understand and predict general preferences that can help companies, government policy-makers and the general public be more aware and better equipped to manage their valuable resources of money, time, attention and memory.

Advancements in both calcium indicators and optical instrumentation have led to new in vivo techniques, such as Miniscopes, capable of recording the spatiotemporal activity of multiple neurons during unrestrained behaviour in rodents. With these microendoscopic techniques, neuronal populations can be stably recorded over multiple sessions. As a result, Miniscopes allow for the investigation of a brain region’s changing activity patterns as a result of disease progression or behaviour. Recently, open source Miniscope initiatives have led to affordable and accessible versions of this technique. In addition, the collaborative open-source community facilitates rapidly evolving modifications, implementations and designs. Notwithstanding the potential and ever-increasing popularity of Miniscopes, the technique is still in its infancy and not widespread. This study consisted of a background review and a pilot study attempting to image neuronal ensembles in the central nucleus of the amygdala (CeA) using the open-source UCLA V3 Miniscope in mice. Despite not being able to successfully record neuronal activity in the CeA, the study has made progress in generating a protocol for Miniscope implementation at the Pharmacology department of Helsinki. Moreover, the study proposes different adjustments that might be implemented in the future. With the continuation of a synergistic collaboration with the Department of Psychology at the university of Jyväskylä, it is likely that both departments will be able to effectively implement the Miniscope technique in the foreseeable future.

Semantics is a study of meaning in language and basis for language comprehension. How these phenomena are processed in the brain is still unclear especially in naturalistic context. In this study, naturalistic language comprehension, and how semantic processing in a narrative context is reflected in brain activity were investigated. Subjects were measured with functional magnetic resonance imaging (fMRI) while listening to a narrative. The semantic content of the narrative was modelled computationally with word2vec and compared to voxel-wise blood-oxygen-level dependent (BOLD) brain signal time courses using ridge regression. This approach provides a novel way to extract more detailed information from the brain data based on semantic content of the stimulus. Inter-subject correlation (ISC) of voxel-wise BOLD signals alone showed both hemispheres taking part in language comprehension. Areas involved in this task overlapped with networks of mentalisation, memory and attention suggesting comprehension requiring other modalities of cognition for its function. Ridge regression suggested cerebellum, superior, middle and medial frontal, inferior and medial parietal and visual cortices bilaterally and temporal cortex on right hemisphere having a role in semantic processing of the narrative. As similar results have been found in previous research on semantics, word2vec appears to model semantics sufficiently and is an applicable tool in brain research. This study suggests contextual language recruiting brain areas in both hemispheres and semantic processing showing as distributed activity on the cortex. This activity is likely dependent on the content of language, but further studies are required to distinguish how strongly brain activity is affected by different semantic contents.

Major depressive disorder (MDD) is characterized by both psychological and physiological changes with debilitating consequences, that lead to significant impairments in daily functioning and overall quality of life. With limited progress in treatment outcomes, there is a growing need to identify robust biomarkers that address the physiological underpinnings of MDD. Combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) is a means of directly evaluating the function of excitatory and inhibitory systems in the stimulated area, with high spatiotemporal resolution. However, large interindividual variability and presence of artifacts in measurements limit potential use of TMS – EEG for biomarker identification. In this thesis, the aim was to identify optimized stimulation targets in the left dorsolateral prefrontal cortex (L-DLPFC), to observe TMS evoked potentials (TEPs), and to investigate whether these TEP characteristics correlate with subjective depressive symptoms. Firstly, early TEPs in the L-DLPFC (<60ms) were successfully obtained by using TMS mapping, which represent genuine neuronal activity of the stimulated area. Secondly, the present study identified an altered excitation / inhibition balance in MDD. The ratio of the second peak-to-peak over the first peak-to-peak of the TEP waveform significantly correlated with MDD symptoms, as measured by the Patient Health Questionnaire (PHQ-9) and Quick Inventory of Depressive Symptomatology (QIDS). Consequently, this altered ratio has significant potential to be used as an objective biomarker, alongside existing subjective symptom scores.

Alzheimer's disease (AD) is a degenerative brain disorder that exhibits deterioration as one gets older. Although much remains to be learned about the pathophysiology of AD, there is strong evidence links amyloid beta (Aβ) plaques, which are responsible for cognitive impairment, to GABAergic interneurons. Model systems are of prime importance for adequately studying the pathophysiology of this disorder; however, existing in vitro models have limitations in producing patient-specific cells. The development of induced pluripotent stem cell (iPSC) technology has provided a novel opportunity for the effective production of disease-relevant cell types while preserving the molecular traits of the patient. In this thesis, the differentiation protocol established by Nicholas et al. (2013) was used to promote the development of interneurons derived from iPSCs. To enhance the efficiency of differentiation, the protocol was modified with the use of small molecules combined in different ways. The end result of the differentiation was characterized using immunocytochemistry (ICC) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The combination of molecules that produced greater efficiency in differentiation was selected, and the optimized protocol was carried out with iPSCs derived from an AD patient harbouring the APP Swedish mutation. The differentiation of cortical interneurons, demonstrated by the expression of pan-neuronal and specific GABAergic neuronal markers, signifies the successful generation of differentiated interneurons in the context of AD. AD iPSCs upregulated several markers related to AD pathology, such as APP and BACE1. However, the cell lines tolerated the small molecules differently, and thus, the protocol needs more optimization in the future. In summary, iPSC-based differentiation protocols are capable of producing disease-specific cell types that would be helpful in developing accurate AD models for revealing the mechanisms of Aβ pathology.

Female breast cancer incidence rate has been growing world-wide and it is the most common cancer in women. In the battle against the breast cancer mortality, early detection is the strongest tool. This is the reason why national mammography screening programs are widely established for selected age groups, usually for women between 50 to 70 years old. Although it is well established that these programs save lives, mammography screening is not feasible to apply to younger and/or older groups due to increasing radiation load as well as economically. There is a room for a non-invasive, easy and cost-effective breast imaging modality, which could be used for all age groups e.g. in connection with regular health checks. In this theses breast cancer as a disease and its present clinical diagnostic tools are presented. As a possible new pre-diagnostic tool, infrared imaging combined with modern analytical and machine learning tools, is introduced. Also, preliminary results of an on-going study are presented, which encourage to continue the development.

Binge eating disorder (BED) is a common eating disorder that includes eating a large amount of food in a short period of time and is often associated with obesity. Patients can suffer from stress, anxiety, and metabolic syndrome caused by the weight gain, but no effective medication for both psychological and physiological issues have been discovered. This thesis studies the potential of short-chain fatty acids (SCFA) in reducing binge-like eating behaviour in a mouse model that does not include food restriction. The model includes a 24 h bingeing period with high-fat food once a week. SCFA butyrate, propionate, and acetate were administered to mice via 1 g/kg i.p. injections or 200 mM drinking water for three days, and their effects on energy intake during the bingeing period were measured. The results show that SCFA can significantly reduce binge-like eating behaviour in mice in the short term, but long-term effects vary. I.p. butyrate, propionate, and acetate decreased energy intake by 68%, 57%, and 62% during the first hour, respectively. SCFA via drinking water did not decrease energy intake a lot, and the results were inconsistent between animals. These results suggest a potential for SCFA to attenuate bingeing episodes when administered acutely, but the mechanisms remain to be discovered.

Understanding the link between the gut microbiota, diet and the enteric nervous system is of significant importance in the prevention of gastrointestinal disorders. The aim of the study was to answer two questions: Firstly, is butyrate able to stimulate the luminal release of serotonin? Secondly, in which parts of the gastrointestinal tract does this possibly occur? These questions are of interest, due to the importance of the serotonergic signalling in the enteric nervous system. We created a luminal perfusion system to investigate the effect of butyrate in the gastrointestinal tract of male Wistar rats (500-550g). We isolated the stomach and 4 cm long segments of the duodenum, jejunum and colon. To our knowledge this form of physiological ex vivo studies investigating the entire gastrointestinal tract have not been done previously. The isolated stomach and the isolated intestinal segments were luminally perfused with 100 mM butyrate for 10 min respectively 45 min. The tissues were homogenized after the luminal perfusion. Serotonin and its main metabolite 5-hydroxyindoleacetic acid (5-HIAA) were assayed using commercial ELISA kits. Our results showed that butyrate significantly stimulates the release of 5-HIAA in the stomach, duodenum, jejunum and colon. Butyrate seems also to have a positive trend-effect on the release of serotonin itself in the stomach, duodenum, jejunum and colon. Although, there is a future potential for preventing gastrointestinal disorders with the help of diet and gut microbiota, the possible clinical significance of our results should be considered carefully.