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Valtteri Kaasinen

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13 papers
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13

YNICL Journal 2026 Journal Article

Striatal dopamine synthesis capacity in Parkinson’s disease: Effects of age, sex, and body mass index in a large [18F]fluorodopa PET cohort

  • Tuulia Malén
  • Jouni Tuisku
  • Marco Bucci
  • Severi Santavirta
  • Valtteri Kaasinen
  • Sakari Kaasalainen
  • Janne Isojärvi
  • Jarmo Hietala

BACKGROUND: F]fluorodopa detects reduced striatal dopamine synthesis capacity in Parkinson's disease (PD) patients. Demographic factors such as sex and BMI are also associated with dopamine synthesis capacity. The combined contribution of demographic and clinical effects however remains elusive. MATERIAL, AIMS, AND METHODS: C]raclopride PET scan, and (3) scanner effects and atlas- versus MRI-based quantification approaches. We provide the mean dopamine synthesis brain maps of healthy controls and PD patients in NeuroVault. RESULTS: estimates for most subjects. CONCLUSIONS: Dopamine synthesis capacity is independently affected by PD and demographic factors and correlated between the striatal and thalamic regions in both controls and PD patients. Adjusting for scanner effects in multi-scanner datasets is recommended. When subject-specific MRI is unavailable, atlas-based normalization may be used with caution to prevent major data loss.

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YNICL Journal 2024 Journal Article

Alterations in type 2 dopamine receptors across neuropsychiatric conditions: A large-scale PET cohort

  • Tuulia Malén
  • Severi Santavirta
  • Sven De Maeyer
  • Jouni Tuisku
  • Valtteri Kaasinen
  • Tuomas Kankare
  • Janne Isojärvi
  • Juha Rinne

PURPOSE: Aberrant dopaminergic function is linked with motor, psychotic, and affective symptoms, but studies have typically compared a single patient group with healthy controls. METHODS: R availability within each group. RESULTS: R availability, while this pattern was weaker in violent offenders. Subjects with schizophrenia, pathological gambling, depression, or overweight did not show clear changes in either the regional receptor availability or the interregional correlation. CONCLUSION: We conclude that the dopaminergic changes in neuropsychiatric conditions might not only affect the overall receptor availability but also how coupled regions are across people. The region-specific receptor availability more profoundly links to the motor symptoms, while the between-region coupling might be disrupted in violence.

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JBHI Journal 2023 Journal Article

Budget-Based Classification of Parkinson's Disease From Resting State EEG

  • Ilkka Suuronen
  • Antti Airola
  • Tapio Pahikkala
  • Mika Murtojärvi
  • Valtteri Kaasinen
  • Henry Railo

Early detection is vital for future neuroprotective treatments of Parkinson's disease (PD). Resting state electroencephalographic (EEG) recording has shown potential as a cost-effective means to aid in detection of neurological disorders such as PD. In this study, we investigated how the number and placement of electrodes affects classifying PD patients and healthy controls using machine learning based on EEG sample entropy. We used a custom budget-based search algorithm for selecting optimized sets of channels for classification, and iterated over variable channel budgets to investigate changes in classification performance. Our data consisted of 60-channel EEG collected at three different recording sites, each of which included observations collected both eyes open (total N = 178) and eyes closed (total N = 131). Our results with the data recorded eyes open demonstrated reasonable classification performance (ACC =. 76; AUC =. 76) with only 5 channels placed far away from each other, the selected regions including right-frontal, left-temporal and midline-occipital sites. Comparison to randomly selected subsets of channels indicated improved classifier performance only with relatively small channel-budgets. The results with the data recorded eyes closed demonstrated consistently worse classification performance (when compared to eyes open data), and classifier performance improved more steadily as a function of number of channels. In summary, our results suggest that a small subset of electrodes of an EEG recording can suffice for detecting PD with a classification performance on par with a full set of electrodes. Furthermore our results demonstrate that separately collected EEG data sets can be used for pooled machine learning based PD detection with reasonable classification performance.

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YNIMG Journal 2022 Journal Article

Atlas of type 2 dopamine receptors in the human brain: Age and sex dependent variability in a large PET cohort

  • Tuulia Malén
  • Tomi Karjalainen
  • Janne Isojärvi
  • Aki Vehtari
  • Paul-Christian Bürkner
  • Vesa Putkinen
  • Valtteri Kaasinen
  • Jarmo Hietala

BACKGROUND: The dopamine system contributes to a multitude of functions ranging from reward and motivation to learning and movement control, making it a key component in goal-directed behavior. Altered dopaminergic function is observed in neurological and psychiatric conditions. Numerous factors have been proposed to influence dopamine function, but due to small sample sizes and heterogeneous data analysis methods in previous studies their specific and joint contributions remain unresolved. METHODS: R) availability in the human brain. We analyzed a large historical dataset (n=156, 120 males and 36 females) of [11C]raclopride PET scans performed between 2004 and 2018. RESULTS: R. The observed effects were independent of regional volumes. These results were validated using two different spatial normalization methods, and the age and sex effects also replicated in an independent sample (n=135). CONCLUSIONS: R expression.

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YNIMG Journal 2021 Journal Article

Cerebral grey matter density is associated with neuroreceptor and neurotransporter availability: A combined PET and MRI study

  • Sandra Manninen
  • Tomi Karjalainen
  • Lauri J. Tuominen
  • Jarmo Hietala
  • Valtteri Kaasinen
  • Juho Joutsa
  • Juha Rinne
  • Lauri Nummenmaa

Positron emission tomography (PET) can be used for in vivo measurement of specific neuroreceptors and transporters using radioligands, while voxel-based morphometric analysis of magnetic resonance images allows automated estimation of local grey matter densities. However, it is not known how regional neuroreceptor or transporter densities are reflected in grey matter densities. Here, we analyzed brain scans retrospectively from 328 subjects and compared grey matter density estimates with neuroreceptor and transporter availabilities. µ-opioid receptors (MORs) were measured with [11C]carfentanil (162 scans), dopamine D2 receptors with [11C]raclopride (92 scans) and serotonin transporters (SERT) with [11C]MADAM (74 scans). The PET data were modelled with simplified reference tissue model. Voxel-wise correlations between binding potential and grey matter density images were computed. Regional binding of all the used radiotracers was associated with grey matter density in region and ligand-specific manner independently of subjects’ age or sex. These data show that grey matter density and MOR and D2R neuroreceptor / SERT availability are correlated, with effect sizes (r2) ranging from 0. 04 to 0. 69. This suggests that future studies comparing PET outcome measure different groups (such as patients and controls) should also analyze interactive effects of grey matter density and PET outcome measures.

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YNICL Journal 2021 Journal Article

Dopamine transporter binding in symptomatic controls and healthy volunteers: Considerations for neuroimaging trials

  • Emma A. Honkanen
  • Mikael Eklund
  • Simo Nuuttila
  • Tommi Noponen
  • Elina Jaakkola
  • Elina Mäkinen
  • Risto Hirvilammi
  • Marko Seppänen

OBJECTIVE: To evaluate possible differences between brain dopamine transporter (DAT) binding in a group of symptomatic parkinsonism patients without dopaminergic degeneration and healthy individuals. BACKGROUND: Dopaminergic neuroimaging studies of Parkinson's disease (PD) have often used control groups formed from symptomatic patients with apparently normal striatal dopamine function. We sought to investigate whether symptomatic patients can be used to represent dopaminergically normal healthy controls. METHODS: I]FP-CIT SPECT and compared to 69 age- and sex-matched symptomatic patients with nondegenerative conditions (including essential tremor, drug-induced parkinsonism and vascular parkinsonism). An automated region-of-interest based analysis of the caudate nucleus and the anterior/posterior putamen was performed. Specific binding ratios (SBR = [ROI-occ]/occ) were compared between the groups. RESULTS: DAT binding in symptomatic patients was 8.6% higher in the posterior putamen than in healthy controls (p = 0.03). Binding correlated negatively with age in both groups but not with motor symptom severity, cognitive function or depression ratings. CONCLUSIONS: I]FP-CIT SPECT.

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YNIMG Journal 2020 Journal Article

Interindividual variability and lateralization of μ-opioid receptors in the human brain

  • Tatu Kantonen
  • Tomi Karjalainen
  • Janne Isojärvi
  • Pirjo Nuutila
  • Jouni Tuisku
  • Juha Rinne
  • Jarmo Hietala
  • Valtteri Kaasinen

Alterations in the brain’s μ-opioid receptor (MOR) system have been associated with several neuropsychiatric disorders. Central MOR availability also varies considerably in healthy individuals. Multiple epidemiological factors have been proposed to influence the MOR system, but due to small sample sizes the magnitude of their influence remains inconclusive. We compiled [11C]carfentanil positron emission tomography scans from 204 individuals with no neurologic or psychiatric disorders, and estimated the effects of sex, age, body mass index (BMI) and smoking on [11C]carfentanil binding potential using between-subject regression analysis. We also examined hemispheric differences in MOR availability. Older age was associated with increase in MOR availability in frontotemporal areas but decrease in amygdala, thalamus, and nucleus accumbens. The age-dependent increase was stronger in males. MOR availability was globally lowered in smokers but independent of BMI. Finally, MOR availability was higher in the right versus the left hemisphere. The presently observed variation in MOR availability may explain why some individuals are prone to develop MOR-linked pathological states, such as chronic pain or psychiatric disorders. Lateralized MOR system may reflect hemispheric work specialization in central emotion and pain processes.

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YNIMG Journal 2018 Journal Article

Dopamine synthesis capacity correlates with µ-opioid receptor availability in the human basal ganglia: A triple-tracer PET study

  • Joonas Majuri
  • Juho Joutsa
  • Eveliina Arponen
  • Sarita Forsback
  • Valtteri Kaasinen

Animal studies have suggested that dopamine and opioid neurotransmitter systems interact in brain regions that are relevant for reward functions, but data in humans are very limited. The interaction is potentially important in disorders affecting these neurotransmitter systems, such as addiction. Here, we investigated whether subcortical μ-opioid receptor (MOR) availability and presynaptic dopamine synthesis capacity are correlated in the healthy human brain or in pathological gamblers (PGs) using positron emission tomography with 6-[18F]fluoro-l-dopa and [11C]carfentanil. The specificity of the findings was further investigated by including a serotonin transporter ligand, [11C]MADAM, as a negative control. Thirteen PG patients and 15 age-, sex- and weight-matched controls underwent the scans. In both groups, presynaptic dopamine synthesis capacity was associated with MOR availability in the putamen, caudate nucleus and globus pallidus. No similar associations were observed between dopamine synthesis capacity and [11C]MADAM binding, supporting a specific interplay between presynaptic dopamine neurotransmission and opioid receptor function in the basal ganglia. Correlations were similar between the groups, suggesting that the dopamine-opioid link is general and unaffected by behavioral addiction. The results provide in vivo human evidence of a connection between endogenous opioid and dopamine signaling in the brain.

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YNIMG Journal 2014 Journal Article

Overlapping activity periods in early visual cortex and posterior intraparietal area in conscious visual shape perception: A TMS study

  • Mika Koivisto
  • Mikko Lähteenmäki
  • Valtteri Kaasinen
  • Riitta Parkkola
  • Henry Railo

Parietal cortex is often activated in brain imaging studies on conscious visual processing, but its causal role and timing in conscious and nonconscious perception are poorly understood. We studied the role of posterior intraparietal sulcus (IPS) and early visual areas (V1/V2) in conscious and nonconscious vision by interfering with their functioning with MRI-guided transcranial magnetic stimulation (TMS). The observers made binary forced-choice decisions concerning the shape or color of the metacontrast masked targets and rated the quality of their conscious perception. TMS was applied 30, 60, 90, or 120ms after stimulus-onset. In the shape discrimination task, TMS of V1/V2 impaired conscious perception at 60, 90, and 120ms and nonconscious perception at 90ms. TMS of IPS impaired only conscious shape perception, also around 90ms. Conscious color perception was facilitated or suppressed depending on the strength of the TMS-induced electric field in V1/V2 at 90ms. The results suggest that simultaneous activity in V1/V2 and IPS around 90ms is necessary for visual awareness of shape but not for nonconscious perception. The overlapping activity periods of IPS and V1/V2 may reflect recurrent interaction between parietal cortex and V1 in conscious shape perception.

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YNIMG Journal 2012 Journal Article

Mesolimbic dopamine release is linked to symptom severity in pathological gambling

  • Juho Joutsa
  • Jarkko Johansson
  • Solja Niemelä
  • Antti Ollikainen
  • Mika M. Hirvonen
  • Petteri Piepponen
  • Eveliina Arponen
  • Hannu Alho

Background Brain dopamine neurons code rewarding environmental stimuli by releasing endogenous dopamine, a transmission signal that is important for reinforcement learning. Human reward-seeking gambling behavior, and especially pathological gambling, has been presumed to be modulated by brain dopamine. Methods Striatal dopamine release was studied with [11C]raclopride positron emission tomography (PET) during gambling with an ecologically valid slot machine gambling task. Twenty-four males with and without pathological gambling (DSM-IV) were scanned three times, and the effects of different gambling outcomes (high-reward and low-reward vs. control task) on dopamine release were evaluated. Results Striatal dopamine was released in both groups during high-reward but also low-reward tasks. The dopamine release during the low-reward task was located in the associative part of the caudate nucleus. During the high-reward task, the effect was also seen in the ventral striatum and the magnitude of dopamine release was associated with parallel gambling “high”. Furthermore, there was a positive correlation between dopamine release during the low-reward and the high-reward task. There was no general difference in the magnitude of dopamine release between pathological gamblers and controls. However, in pathological gamblers, dopamine release correlated positively with gambling symptom severity. Conclusions Striatal dopamine is released during gambling irrespective of gambling outcome suggesting that the mere expectation/prediction of reward is sufficient to induce dopaminergic changes. Although dopamine release during slot machine gambling is comparable between healthy controls and pathological gamblers, greater gambling symptom severity is associated with greater dopaminergic responses. Thus, as the dopamine reward deficiency theory predicts blunted mesolimbic dopamine responses to gambling in addicted individuals, our results question the validity of the reward deficiency hypothesis in pathological gambling.

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v2026.09.13