Peter Klaver
University of Surrey, Faculty of Health and Medical Sciences, Faculty Member
In this study we investigated how changes of functional connectivity over time accompanies consolidation of face memories. Based on previous research we hypothesised that particularly connectivity changes in networks initially active... more
In this study we investigated how changes of functional connectivity over time accompanies consolidation of face memories. Based on previous research we hypothesised that particularly connectivity changes in networks initially active during face perception and face encoding would be associated with individual recognition memory performance. Resting-state functional connectivity was examined shortly before, shortly after and about forty minutes after incidental learning of faces. Memory performance was assessed in a surprise recognition test shortly after the last resting-state session. Results reveal that memory performance related connectivity between the left fusiform face area and other brain areas gradually changed over the course of the experiment. Specifically, the increase in connectivity with the contralateral fusiform gyrus, the hippocampus, the amygdala and the inferior frontal gyrus correlated with recognition memory performance. Since especially the increase in connectivity in the two final resting-state sessions was associated with memory performance the present results demonstrate that memory formation is not restricted to the incidental learning phase but continues and increases in the following forty minutes. We discuss that particularly the delayed increase in inter-hemisphere connectivity between the left and right fusiform gyrus is an indicator for memory formation and consolidation processes. This article is protected by copyright. All rights reserved.
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Research Interests:
Research Interests:
Cognitive Science, Cognition, Magnetic Resonance Imaging, Face, Face recognition (Psychology), and 16 moreInformation Processing, Strategy, Temporal Lobe, Humans, Female, Face processing, Functional Imaging, Male, Magnetic Resonance, Fusiform face area, Adult, Parietal Lobe, Fusiform Gyrus, Nuclear Magnetic Resonance Imaging, Neurosciences, and Delayed Matching-to-Sample
ABSTRACT
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Cognitive Science, Statistical Analysis, Electroencephalography, Memory, Brain Mapping, and 15 moreWavelet Analysis, Hippocampus, Temporal Lobe, Evoked Potentials, Humans, Female, Male, Temporal Lobe Epilepsy, Electroencephalogram, Phase Locking, Declarative Memory, Adult, Spectrum analysis, Medial Temporal Lobe, and Neurosciences
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Attention-Deficit/Hyperactivity Disorder (ADHD) has been associated with spatial working memory as well as frontostriatal core deficits. However, it is still unclear how the link between these frontostriatal deficits and working memory... more
Attention-Deficit/Hyperactivity Disorder (ADHD) has been associated with spatial working memory as well as frontostriatal core deficits. However, it is still unclear how the link between these frontostriatal deficits and working memory function in ADHD differs in children and adults. This study examined spatial working memory in adults and children with ADHD, focusing on identifying regions demonstrating age-invariant or age-dependent abnormalities. We used functional magnetic resonance imaging to examine a group of 26 children and 35 adults to study load manipulated spatial working memory in patients and controls. In comparison to healthy controls, patients demonstrated reduced positive parietal and frontostriatal load effects, i.e., less increase in brain activity from low to high load, despite similar task performance. In addition, younger patients showed negative load effects, i.e., a decrease in brain activity from low to high load, in medial prefrontal regions. Load effect differences between ADHD and controls that differed between age groups were found predominantly in prefrontal regions. Age-invariant load effect differences occurred predominantly in frontostriatal regions. The age-dependent deviations support the role of prefrontal maturation and compensation in ADHD, while the age-invariant alterations observed in frontostriatal regions provide further evidence that these regions reflect a core pathophysiology in ADHD.
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Marked changes in brain physiology and structure take place between childhood and adulthood, including changes in functional connectivity and changes in the balance between main excitatory and inhibitory neurotransmitters glutamate (Glu)... more
Marked changes in brain physiology and structure take place between childhood and adulthood, including changes in functional connectivity and changes in the balance between main excitatory and inhibitory neurotransmitters glutamate (Glu) and GABA. The balance of these neurotransmitters is thought to underlie neural activity in general and functional connectivity networks in particular, but so far no studies have investigated the relationship between human development related differences in these neurotransmitters and concomitant changes in functional connectivity. GABA+/H2O and Glu/H2O levels were acquired in a group of healthy children, adolescents, and adults in a subcortical (basal ganglia) region, as well as in a frontal region in adolescents and adults. Our results showed higher GABA+/Glu with age in both the subcortical and the frontal voxel, which were differentially associated with significantly lower Glu/H2O with age in the subcortical voxel and by significantly higher GABA...
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Neuroscience, Nonparametric Statistics, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Adolescent, and 15 moreBrain Mapping, Humans, Child, Female, Male, Young Adult, D-Aspartic Acid, Middle Aged, Oxygen, Adult, Basal ganglia, Short Term Memory, Glutamic Acid, Gamma-Aminobutyric Acid, and Cohort Studies
Developmental dyscalculia (DD) is a specific learning disability affecting the normal acquisition of arithmetic skills. Current studies estimate that 3-6% of the school population is affected by DD. Genetic, neurobiological, and... more
Developmental dyscalculia (DD) is a specific learning disability affecting the normal acquisition of arithmetic skills. Current studies estimate that 3-6% of the school population is affected by DD. Genetic, neurobiological, and epidemiologic evidence indicates that dyscalculia is a brain-based disorder. Imaging studies suggest the involvement of parietal and prefrontal cortices in arithmetic tasks. The aim of the present study was to analyze if children with DD show structural differences in parietal, frontal, and cingulate areas compared to typically achieving children. Magnetic resonance imaging was obtained from 12 children with DD aged 9.3+/-0.2 years and 12 age-matched control children without any learning disabilities on a 1.5 T whole-body scanner. Voxel-based morphometry analysis with an optimization of spatial segmentation and normalization procedures was applied to compare the two groups in order to find differences in cerebral gray and white matter. Compared to controls, ...
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Genetics, Mathematics, Spatial Memory, Magnetic Resonance Imaging, Working Memory, and 20 moreBrain, Humans, Child, Female, Neuroimage, Voxel Based Morphometry, Male, Three Dimensional Imaging, Developmental disabilities, Specific Learning Disabilities, White matter, Image Enhancement, Reproducibility of Results, Parahippocampal Gyrus, Sensitivity and Specificity, Learning Disabled, Gray Matter, Frontal Lobe, Whole Body, and Cognition disorders
We employed a source memory task in an event related fMRI study to dissociate MTL processes associated with either contextual retrieval or item recognition. To introduce context during study, stimuli (photographs of buildings and natural... more
We employed a source memory task in an event related fMRI study to dissociate MTL processes associated with either contextual retrieval or item recognition. To introduce context during study, stimuli (photographs of buildings and natural landscapes) were transformed into one of four single-color-scales: red, blue, yellow, or green. In the subsequent old/new recognition memory test, all stimuli were presented as gray scale photographs, and old-responses were followed by a four-alternative source judgment referring to the color in which the stimulus was presented during study. Our results suggest a clear-cut process dissociation within the human MTL. While an activity increase accompanies successful retrieval of contextual information, an activity decrease provides a familiarity signal that is sufficient for successful item recognition.
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In rodents, cyclically fluctuating levels of gonadal steroid hormones modulate neural plasticity by altering synaptic transmission and synaptogenesis. Alterations of mood and cognition observed during the menstrual cycle suggest that... more
In rodents, cyclically fluctuating levels of gonadal steroid hormones modulate neural plasticity by altering synaptic transmission and synaptogenesis. Alterations of mood and cognition observed during the menstrual cycle suggest that steroid-related plasticity also occurs in humans. Cycle phase-dependent differences in cognitive performance have almost exclusively been found in tasks probing lateralized neuronal domains, i.e., cognitive domains such as language, which are predominantly executed by one hemisphere. To search for neural correlates of hormonally mediated neural plasticity in humans, we thus conducted a functional magnetic resonance imaging study measuring brain activity related to a semantic decision task in the language domain. This was contrasted with a letter-matching task in the perceptual domain, in which we expected no steroid hormone-mediated effect. We investigated 12 young healthy women in a counterbalanced repeated-measure design during low-steroid menstruatio...
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Behavior, Magnetic Resonance Imaging, Sex Hormones, Menstruation, Linear models, and 22 moreBrain Mapping, Brain, Progesterone, Humans, Testosterone, Female, Hormones, Reaction Time, Verbal behavior, Neuronal Plasticity, Frontal Cortex, The, Synaptic Transmission, Menstrual Cycle, Human Brain, Cognitive Performance, Neural plasticity, Repeated Measures, Adult, Reference Values, Estradiol, and Follicle stimulating hormone
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Little is known about the functional development of dorsal and ventral visual streams. The right posterior superior temporal sulcus (pSTS) represents a pivotal point of the two streams and is involved in the perception of biological... more
Little is known about the functional development of dorsal and ventral visual streams. The right posterior superior temporal sulcus (pSTS) represents a pivotal point of the two streams and is involved in the perception of biological motion. Here, we compared brain activity between children (aged 5-7 years) and adults (aged 20-32 years) while they were viewing point-light dot animations of biological motion. Biological motion-related activation was found in right pSTS of adults, and in right fusiform gyrus and left middle temporal lobe of children. Group comparisons revealed increased activity in pSTS for adults and in fusiform gyrus for children. Only poorly performing children showed fusiform gyrus activity. These findings indicate that pSTS functioning is not adult-like at the age of 6 years.
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A central question in developmental psychology is how a child acquires knowledge about the surrounding world. Is it important for learning to know what an object represents, before a child knows how to deal with it? Or does a child learn... more
A central question in developmental psychology is how a child acquires knowledge about the surrounding world. Is it important for learning to know what an object represents, before a child knows how to deal with it? Or does a child learn because it is improving haptic skills to act upon an object, to follow its actions and predict how it behaves? Behavioral research investigating such questions distinguished the role of dorsal and ventral visual streams in learning to "know how" and "know what" about objects, but these studies did not unequivocally resolve how these functions mature. Recent functional, structural, and microstructural neuroimaging research has shed a novel light on the normal development of the human visual system, particularly during later stages of child development. This chapter reviews these neuroimaging studies and interrogates them on the question of whether dorsal and ventral visual streams mature at different rates. Structural gray matter properties within the ventral visual stream show prolonged development compared to the dorsal stream, whereas white matter connectivity within dorsal visual stream structures matures later. Functionally specialized areas in the ventral visual stream show increased size during development, whereas parietal dorsal stream areas show increasing activity associated with high-order visual perception. Such results emphasize the importance of neuroimaging techniques for research on visual cognitive development. They suggest that high-order visual functions mature late and that dorsal and ventral visual streams follow different neurodevelopmental trajectories.
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Cognitive Science, Developmental Psychology, Cognitive development, Child Development, Visual perception, and 18 moreVisual development, Magnetic Resonance Imaging, Diffusion Tensor Imaging, Adolescent, Visual Cortex, Brain Mapping, Humans, Child, Visual System, Infant, White matter, Ventral Stream, Dorsal Stream, Microstructures, Typical Development, Human Visual System, Neurosciences, and Gray Matter
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Cognitive Science, Human Memory, Nature, Memory, Hippocampus, and 22 moreHumans, Female, Male, Nature Neuroscience, Verbal behavior, Temporal Lobe Epilepsy, Phase Synchronization, Oscillations, Gamma Band, Synaptic Transmission, Electroencephalogram, Neurons, Declarative Memory, Entorhinal Cortex, Adult, Medial Temporal Lobe, Neural pathways, Biological clocks, Action Potentials, Memory Disorders, Neurosciences, and Magnetic resonance angiography
The EEG during deep sleep exhibits a distinct cortically generated slow oscillation of around and below 1 Hz which can be distinguished from other delta (0.5-3.5 Hz) activity. Intracranial studies showed that this slow oscillation... more
The EEG during deep sleep exhibits a distinct cortically generated slow oscillation of around and below 1 Hz which can be distinguished from other delta (0.5-3.5 Hz) activity. Intracranial studies showed that this slow oscillation triggers and groups cortical network firing. In the present study, we examined whether the phases of the slow oscillation during sleep stage 4 are correlated with the magnitude of sigma (12-16 Hz) and gamma (> 20 Hz) scalp activity. For this purpose, 10-min segments of uninterrupted stage 4 sleep EEG from 9 subjects were analyzed by applying wavelet techniques. We found that scalp recorded sigma, but not gamma, activity is modulated by the phases of the slow oscillation during deep sleep. Enhancement of sigma activity was observed to be triggered by the peak of the surface positive slow wave component, whereas reduction of sigma activity started around the peak of the negative component.
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Cognitive Science, Child Development, Visual perception, Adolescent Development, Magnetic Resonance Imaging, and 17 moreAttention, Adolescent, Individual Differences, Brain Mapping, Hippocampus, Humans, Child, Female, Male, Cortex, Posterior Parietal Cortex, Young Adult, Adult, Parietal Lobe, Short Term Memory, Visual Short Term Memory, and Neurosciences
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Cognitive Science, Electrophysiology, Magnetic Resonance Imaging, Imagination, Face recognition (Psychology), and 17 moreRecognition memory, Information Processing, Hippocampus, Evoked Potentials, Humans, Word Recognition, Female, Drug Resistance, Male, Word Frequency, Verbal behavior, Temporal Lobe Epilepsy, Middle Aged, Adult, Medial Temporal Lobe, Memory Disorders, and Neurosciences
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Human declarative memory formation crucially depends on processes within the medial temporal lobe (MTL). These processes can be monitored in real-time by recordings from depth electrodes implanted in the MTL of patients with epilepsy who... more
Human declarative memory formation crucially depends on processes within the medial temporal lobe (MTL). These processes can be monitored in real-time by recordings from depth electrodes implanted in the MTL of patients with epilepsy who undergo presurgical evaluation. In our studies, patients performed a word memorization task during depth EEG recording. Afterwards, the difference between event-related potentials (ERPs) corresponding to subsequently remembered versus forgotten words was analyzed. These kind of studies revealed that successful memory encoding is characterized by an early process generated by the rhinal cortex within 300 ms following stimulus onset. This rhinal process precedes a hippocampal process, which starts about 200 ms later. Further investigation revealed that the rhinal process seems to be a correlate of semantic preprocessing which supports memory formation, whereas the hippocampal process appears to be a correlate of an exclusively mnemonic operation. These studies yielded only indirect evidence for an interaction of rhinal cortex and hippocampus. Direct evidence for a memory related cooperation between both structures, however, has been found in a study analyzing so called gamma activity, EEG oscillations of around 40 Hz. This investigation showed that successful as opposed to unsuccessful memory formation is accompanied by an initial enhancement of rhinal-hippocampal phase synchronization, which is followed by a later desynchronization. Present knowledge about the function of phase synchronized gamma activity suggests that this phase coupling and decoupling initiates and later terminates communication between the two MTL structures. Phase synchronized rhinal-hippocampal gamma activity may, moreover, accomplish Hebbian synaptic modifications and thus provide an initial step of declarative memory formation on the synaptic level.
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Neuroscience, Psychology, Cognitive Science, Semantics, Electroencephalography, and 19 moreSemantic association, Low Frequency, Memory, High Frequency, Brain Mapping, Hippocampus, Humans, Female, Male, Temporal Lobe Epilepsy, Phase Synchronization, Gamma Band, Declarative Memory, Middle Aged, Entorhinal Cortex, Adult, Medial Temporal Lobe, Neural pathways, and Neurosciences
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Research Interests:
Cognitive Science, Cognition, Magnetic Resonance Imaging, Face, Face recognition (Psychology), and 16 moreInformation Processing, Strategy, Temporal Lobe, Humans, Female, Face processing, Functional Imaging, Male, Magnetic Resonance, Fusiform face area, Adult, Parietal Lobe, Fusiform Gyrus, Nuclear Magnetic Resonance Imaging, Neurosciences, and Delayed Matching-to-Sample
Event-related potentials (ERPs) were recorded as 12 subjects performed a delayed matching to sample task. We presented two bilateral abstract shapes and cued spatially which had to be memorized for a subsequent matching task: left, right... more
Event-related potentials (ERPs) were recorded as 12 subjects performed a delayed matching to sample task. We presented two bilateral abstract shapes and cued spatially which had to be memorized for a subsequent matching task: left, right or both. During memorization a posterior slow negative ERP wave developed over the hemisphere contralateral to the memorized shape. This effect was similar in high and low memory load trials while the memory figures were visible (for 1000 ms). As the figures disappeared (for 1500 ms), the effect persisted only in the low memory load conditions. We suggest that the contralateral negativity reflects a visual short-term memory process and that capacity limitation in the high memory load condition causes this process to collapse.