Previous studies have documented that motor training improves performance on motor skill tasks an... more Previous studies have documented that motor training improves performance on motor skill tasks and related this to altered functional brain activity in cerebellum, striatum, and frontal motor cortical areas. Mental training can also improve the performance on motor tasks, but the neural basis of such facilitation is unclear. The purpose of the present study was to identify neural correlates of training-related changes on a finger-tapping task. Subjects were scanned twice, 1 week apart, with fMRI while they performed two finger-tapping sequences with the left hand. In-between scans, they practiced daily on one of the sequences. Half of the participants received motor training and the other half received mental training (motor imagery). Both training procedures led to significant increases in tapping performance. This was seen for both the trained and the untrained sequence (non-specific effect), although the gain was larger for the trained sequence (sequence-specific effect). The non-specific training effect corresponded to a reduction in the number of activated areas from an extensive set of brain regions prior to training to mainly motor cortex and cerebellum after training. The sequence-specific training effect involved the supplementary motor area and the cerebellum for motor training and visual association cortex for mental training. We conclude that gains following motor and mental training are based on distinct neuroplastic changes in the brain.
The Cognitive Neuroscience of Working Memory, 2007
Intersecting the divide between working memory and episodic memory : Evidence from sustained and ... more Intersecting the divide between working memory and episodic memory : Evidence from sustained and transient brain activity patterns
The activation of dorsolateral prefrontal cortex (dlPFC) has been suggested to reflect the engage... more The activation of dorsolateral prefrontal cortex (dlPFC) has been suggested to reflect the engagement of a control mechanism for top-down biasing of context processing in resource-demanding memory tasks. Here we tested the hypothesis that the dlPFC subserves a similar function also in attention and emotion tasks. 18 healthy young adults were tested in a functional magnetic resonance imaging (fMRI) study where the demands for context processing were manipulated in three different cognitive domains: auditory attention, episodic retrieval, and emotion regulation. We found that the right dlPFC was jointly sensitive to increased cognitive demands in the attention and memory tasks. By contrast, increased demands in the emotion task (reappraisal) were associated with increased activity in ventromedial PFC along with decreased amygdala activity. Our findings of divergent prefrontal control networks for cognitive and emotional control extend previous separations of cognition and emotion in the anterior cingulate cortex.
Previous studies have documented that motor training improves performance on motor skill tasks an... more Previous studies have documented that motor training improves performance on motor skill tasks and related this to altered functional brain activity in cerebellum, striatum, and frontal motor cortical areas. Mental training can also improve the performance on motor tasks, but the neural basis of such facilitation is unclear. The purpose of the present study was to identify neural correlates of training-related changes on a finger-tapping task. Subjects were scanned twice, 1 week apart, with fMRI while they performed two finger-tapping sequences with the left hand. In-between scans, they practiced daily on one of the sequences. Half of the participants received motor training and the other half received mental training (motor imagery). Both training procedures led to significant increases in tapping performance. This was seen for both the trained and the untrained sequence (non-specific effect), although the gain was larger for the trained sequence (sequence-specific effect). The non-specific training effect corresponded to a reduction in the number of activated areas from an extensive set of brain regions prior to training to mainly motor cortex and cerebellum after training. The sequence-specific training effect involved the supplementary motor area and the cerebellum for motor training and visual association cortex for mental training. We conclude that gains following motor and mental training are based on distinct neuroplastic changes in the brain.
To examine the relationship between neuropsychological outcome following mild head injury (MHI) a... more To examine the relationship between neuropsychological outcome following mild head injury (MHI) and APOE genotype. Data from a population-based longitudinal study (n = 3,500) were used to identify 34 adults who experienced MHI during the course of the study. Their pre- and postinjury performances on a battery of nine neuropsychological tests were compared within person, and the postinjury performance was compared with that of age- and gender-matched control subjects. The within-person comparisons showed that participants with at least one APOE epsilon4 allele (n = 11) had a significantly decreased postinjury performance on three of the tests, whereas the postinjury performance for APOE epsilon4-negative participants (n = 23) was unchanged. There was no significant difference in postinjury performance between participants with/without the epsilon4 allele, and neither group was impaired relative to controls. APOE genotype may influence the outcome following an MHI. Pre/postinjury within-person comparisons seem more sensitive than control group comparisons for detecting injury-related effects.
Multi-modal brain imaging was used to examine the relation between individual differences in rest... more Multi-modal brain imaging was used to examine the relation between individual differences in resting-state striatal dopamine D2 binding and the magnitude of prefrontal BOLD activation during updating of long-term memory (LTM) representations. Increased activity in the left prefrontal cortex was observed when LTM updating was required, and there was a positive correlation between striatal D2 activity and the magnitude of left prefrontal activity during updating. These findings support predictions from neurocomputational models of a relation of dopaminergic neurotransmission to transient cognitive operations and related brain activity.
The catechol O-methyltransferase (COMT) gene—encoding an enzyme that is essential for the degrada... more The catechol O-methyltransferase (COMT) gene—encoding an enzyme that is essential for the degradation of dopamine (DA) in prefrontal cortex (PFC)—contains a single nucleotide polymorphism (val/met) important for cognition. According to the tonic–phasic hypothesis, individuals carrying the low-enzyme-activity allele (met) are characterized by enhanced tonic DA activity in PFC, promoting sustained cognitive representations in working memory. Val carriers have reduced tonic but enhanced phasic dopaminergic activity in subcortical regions, enhancing cognitive flexibility. We tested the tonic–phasic DA hypothesis by dissociating sustained and transient brain activity during performance on a 2-back working memory test using mixed blocked/event-related functional magnetic resonance imaging. Participants were men recruited from a random sample of the population (the Betula study) and consisted of 11 met/met and 11 val/val carriers aged 50 to 65 years, matched on age, education, and cognitiv...
A critical feature of higher cognitive functioning is the capacity to flexibly tailor information... more A critical feature of higher cognitive functioning is the capacity to flexibly tailor information processing and behaviors to current situational demands. Recent neurocognitive models have been postulated to account for the dynamic nature of human executive processing by invoking two dissociable cognitive control modes, proactive and reactive control. These may involve partially overlapping, but temporally distinct neural implementation in the prefrontal cortex. Prior brain imaging studies exploring proactive control have mainly used tasks requiring only information about single-items to be retained over unfilled delays. Whether proactive control can also be utilized to facilitate performance in more complex working memory tasks, in which concurrent processing of intervening items and updating is mandatory during contextual cue maintenance remains an open question. To examine this issue and to elucidate the extent to which overlapping neural substrates underlie proactive and reactive control we used fMRI and a modified verbal 3-back paradigm with embedded cues predictive of high-interference trials. This task requires context information to be retained over multiple intervening trials. We found that performance improved with item-specific cues predicting forthcoming lures despite increased working memory load. Temporal dynamics of activation in the right inferior frontal gyrus suggest flexible switching between proactive and reactive control in a context-dependent fashion, with greater sustained responses elicited in the 3-back task involving context maintenance of cue information and greater transient responses elicited in the 3-back task absent of cues.
The central theme of the present thesis revolves around the exploration of similarities and diffe... more The central theme of the present thesis revolves around the exploration of similarities and differences in brain activity patterns invoked by the component processes underlying mnemonic, executive ...
Marklund, P. (2004). Shared component processes in working memory and long-term memory: Insights ... more Marklund, P. (2004). Shared component processes in working memory and long-term memory: Insights from functional brain imaging. Department of Psychology, Umea University, S-901 87 Umea SwedenRecent ...
The serotonin 5-HT1B receptor subtype is involved in the modulation of serotonin release and is a... more The serotonin 5-HT1B receptor subtype is involved in the modulation of serotonin release and is a target of interest for neuroreceptor imaging. Previous studies have shown that the serotonin system is affected in Parkinsońs disease (PD). Cognitive function, frequently impaired in PD, has been linked to the serotonin system. The aim of this study was to examine whether 5-HT1B receptor availability in the brain of healthy subjects and PD patients is associated with measures of cognitive function. Twelve control subjects and ten PD patients with normal mini-mental state examination scores were included in this study. Cognitive function was evaluated by assessment of semantic, episodic, and working memory, as well as fluency and visual attention. Creative ability, a measure of divergent thinking, was examined with the alternative uses of objects task. PET measurements were performed with the 5-HT1B receptor-radioligand [(11) C]AZ10419369 using the HRRT system. PD patients showed statist...
Previous studies have documented that motor training improves performance on motor skill tasks an... more Previous studies have documented that motor training improves performance on motor skill tasks and related this to altered functional brain activity in cerebellum, striatum, and frontal motor cortical areas. Mental training can also improve the performance on motor tasks, but the neural basis of such facilitation is unclear. The purpose of the present study was to identify neural correlates of training-related changes on a finger-tapping task. Subjects were scanned twice, 1 week apart, with fMRI while they performed two finger-tapping sequences with the left hand. In-between scans, they practiced daily on one of the sequences. Half of the participants received motor training and the other half received mental training (motor imagery). Both training procedures led to significant increases in tapping performance. This was seen for both the trained and the untrained sequence (non-specific effect), although the gain was larger for the trained sequence (sequence-specific effect). The non-specific training effect corresponded to a reduction in the number of activated areas from an extensive set of brain regions prior to training to mainly motor cortex and cerebellum after training. The sequence-specific training effect involved the supplementary motor area and the cerebellum for motor training and visual association cortex for mental training. We conclude that gains following motor and mental training are based on distinct neuroplastic changes in the brain.
The Cognitive Neuroscience of Working Memory, 2007
Intersecting the divide between working memory and episodic memory : Evidence from sustained and ... more Intersecting the divide between working memory and episodic memory : Evidence from sustained and transient brain activity patterns
The activation of dorsolateral prefrontal cortex (dlPFC) has been suggested to reflect the engage... more The activation of dorsolateral prefrontal cortex (dlPFC) has been suggested to reflect the engagement of a control mechanism for top-down biasing of context processing in resource-demanding memory tasks. Here we tested the hypothesis that the dlPFC subserves a similar function also in attention and emotion tasks. 18 healthy young adults were tested in a functional magnetic resonance imaging (fMRI) study where the demands for context processing were manipulated in three different cognitive domains: auditory attention, episodic retrieval, and emotion regulation. We found that the right dlPFC was jointly sensitive to increased cognitive demands in the attention and memory tasks. By contrast, increased demands in the emotion task (reappraisal) were associated with increased activity in ventromedial PFC along with decreased amygdala activity. Our findings of divergent prefrontal control networks for cognitive and emotional control extend previous separations of cognition and emotion in the anterior cingulate cortex.
Previous studies have documented that motor training improves performance on motor skill tasks an... more Previous studies have documented that motor training improves performance on motor skill tasks and related this to altered functional brain activity in cerebellum, striatum, and frontal motor cortical areas. Mental training can also improve the performance on motor tasks, but the neural basis of such facilitation is unclear. The purpose of the present study was to identify neural correlates of training-related changes on a finger-tapping task. Subjects were scanned twice, 1 week apart, with fMRI while they performed two finger-tapping sequences with the left hand. In-between scans, they practiced daily on one of the sequences. Half of the participants received motor training and the other half received mental training (motor imagery). Both training procedures led to significant increases in tapping performance. This was seen for both the trained and the untrained sequence (non-specific effect), although the gain was larger for the trained sequence (sequence-specific effect). The non-specific training effect corresponded to a reduction in the number of activated areas from an extensive set of brain regions prior to training to mainly motor cortex and cerebellum after training. The sequence-specific training effect involved the supplementary motor area and the cerebellum for motor training and visual association cortex for mental training. We conclude that gains following motor and mental training are based on distinct neuroplastic changes in the brain.
To examine the relationship between neuropsychological outcome following mild head injury (MHI) a... more To examine the relationship between neuropsychological outcome following mild head injury (MHI) and APOE genotype. Data from a population-based longitudinal study (n = 3,500) were used to identify 34 adults who experienced MHI during the course of the study. Their pre- and postinjury performances on a battery of nine neuropsychological tests were compared within person, and the postinjury performance was compared with that of age- and gender-matched control subjects. The within-person comparisons showed that participants with at least one APOE epsilon4 allele (n = 11) had a significantly decreased postinjury performance on three of the tests, whereas the postinjury performance for APOE epsilon4-negative participants (n = 23) was unchanged. There was no significant difference in postinjury performance between participants with/without the epsilon4 allele, and neither group was impaired relative to controls. APOE genotype may influence the outcome following an MHI. Pre/postinjury within-person comparisons seem more sensitive than control group comparisons for detecting injury-related effects.
Multi-modal brain imaging was used to examine the relation between individual differences in rest... more Multi-modal brain imaging was used to examine the relation between individual differences in resting-state striatal dopamine D2 binding and the magnitude of prefrontal BOLD activation during updating of long-term memory (LTM) representations. Increased activity in the left prefrontal cortex was observed when LTM updating was required, and there was a positive correlation between striatal D2 activity and the magnitude of left prefrontal activity during updating. These findings support predictions from neurocomputational models of a relation of dopaminergic neurotransmission to transient cognitive operations and related brain activity.
The catechol O-methyltransferase (COMT) gene—encoding an enzyme that is essential for the degrada... more The catechol O-methyltransferase (COMT) gene—encoding an enzyme that is essential for the degradation of dopamine (DA) in prefrontal cortex (PFC)—contains a single nucleotide polymorphism (val/met) important for cognition. According to the tonic–phasic hypothesis, individuals carrying the low-enzyme-activity allele (met) are characterized by enhanced tonic DA activity in PFC, promoting sustained cognitive representations in working memory. Val carriers have reduced tonic but enhanced phasic dopaminergic activity in subcortical regions, enhancing cognitive flexibility. We tested the tonic–phasic DA hypothesis by dissociating sustained and transient brain activity during performance on a 2-back working memory test using mixed blocked/event-related functional magnetic resonance imaging. Participants were men recruited from a random sample of the population (the Betula study) and consisted of 11 met/met and 11 val/val carriers aged 50 to 65 years, matched on age, education, and cognitiv...
A critical feature of higher cognitive functioning is the capacity to flexibly tailor information... more A critical feature of higher cognitive functioning is the capacity to flexibly tailor information processing and behaviors to current situational demands. Recent neurocognitive models have been postulated to account for the dynamic nature of human executive processing by invoking two dissociable cognitive control modes, proactive and reactive control. These may involve partially overlapping, but temporally distinct neural implementation in the prefrontal cortex. Prior brain imaging studies exploring proactive control have mainly used tasks requiring only information about single-items to be retained over unfilled delays. Whether proactive control can also be utilized to facilitate performance in more complex working memory tasks, in which concurrent processing of intervening items and updating is mandatory during contextual cue maintenance remains an open question. To examine this issue and to elucidate the extent to which overlapping neural substrates underlie proactive and reactive control we used fMRI and a modified verbal 3-back paradigm with embedded cues predictive of high-interference trials. This task requires context information to be retained over multiple intervening trials. We found that performance improved with item-specific cues predicting forthcoming lures despite increased working memory load. Temporal dynamics of activation in the right inferior frontal gyrus suggest flexible switching between proactive and reactive control in a context-dependent fashion, with greater sustained responses elicited in the 3-back task involving context maintenance of cue information and greater transient responses elicited in the 3-back task absent of cues.
The central theme of the present thesis revolves around the exploration of similarities and diffe... more The central theme of the present thesis revolves around the exploration of similarities and differences in brain activity patterns invoked by the component processes underlying mnemonic, executive ...
Marklund, P. (2004). Shared component processes in working memory and long-term memory: Insights ... more Marklund, P. (2004). Shared component processes in working memory and long-term memory: Insights from functional brain imaging. Department of Psychology, Umea University, S-901 87 Umea SwedenRecent ...
The serotonin 5-HT1B receptor subtype is involved in the modulation of serotonin release and is a... more The serotonin 5-HT1B receptor subtype is involved in the modulation of serotonin release and is a target of interest for neuroreceptor imaging. Previous studies have shown that the serotonin system is affected in Parkinsońs disease (PD). Cognitive function, frequently impaired in PD, has been linked to the serotonin system. The aim of this study was to examine whether 5-HT1B receptor availability in the brain of healthy subjects and PD patients is associated with measures of cognitive function. Twelve control subjects and ten PD patients with normal mini-mental state examination scores were included in this study. Cognitive function was evaluated by assessment of semantic, episodic, and working memory, as well as fluency and visual attention. Creative ability, a measure of divergent thinking, was examined with the alternative uses of objects task. PET measurements were performed with the 5-HT1B receptor-radioligand [(11) C]AZ10419369 using the HRRT system. PD patients showed statist...
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