
Lukas KunzUniversity of Bonn | Uni Bonn · Epileptologische Klinik
Lukas Kunz
Dr. rer. nat. Dr. med.
About
45
Publications
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Introduction
Lukas Kunz currently works at the Department of Epileptology at the University Hospital Bonn. His research focuses on the neural foundations of spatial navigation and memory in humans.
Publications
Publications (45)
Spatial memory is a fundamental cognitive function that enables humans and other species to encode and recall the locations of items in their environments. Humans employ diverse strategies to support spatial memory, including the use of cognitive maps. Cognitive maps are mental representations of the environment that organize its content along two...
The precise timing of single-neuron activity in relation to local field potentials may support various cognitive functions. Extensive research in rodents, along with some evidence in humans, suggests that single-neuron activity at specific phases of theta oscillations plays a crucial role in memory processes. Our fundamental understanding of such t...
Associative memory enables the encoding and retrieval of relations between
different stimuli. To better understand its neural basis, we investigated
whether associative memory involves temporally correlated spiking
of medial temporal lobe (MTL) neurons that exhibit stimulus-specific
tuning. Using single-neuron recordings from patients with epilepsy...
Early signs of dementia
There is currently no cure for Alzheimer's disease. One of the reasons could be that interventions start too late, when there is already irreversible damage to the brain. Developing a biomarker that would help to effectively start therapy at very early stages of the disease is thus of high interest. Kunz et al. studied neura...
Spatial navigation and memory rely on neural systems that encode places, distances, and directions in relation to the external world or relative to the navigating organism. Place, grid, and head-direction cells form key units of world-referenced, allocentric cognitive maps, but the neural basis of self-centered, egocentric representations remains p...
Background
The medial temporal lobe (MTL) is the first cortical region affected by tauopathy in Alzheimer’s disease (AD) and is implicated in spatial orientation. In early AD stages, navigation deficits, including path integration deficits, could be present, even before memory deficits. We investigated whether these deficits were related to AD path...
Background Early Alzheimer’s disease diagnosis is crucial for preventive therapy development. Standard neuropsychological evaluation does not identify clinically normal individuals with brain amyloidosis, the first stage of the pathology, defined as preclinical Alzheimer’s disease. Spatial navigation assessment, in particular path integration, appe...
Temporal memory enables us to remember the temporal order of events happening in our life. The human medial temporal lobe (MTL) appears to contain neural representations supporting temporal memory formation, but the cellular mechanisms that preserve temporal order information for recall are largely unknown. Here, we examined whether human MTL neuro...
Visual working memory depends on both material-specific brain areas in the ventral visual stream (VVS) that support the maintenance of stimulus representations and on regions in the prefrontal cortex (PFC) that control these representations. How executive control prioritizes working memory contents and whether this affects their representational fo...
When subjects navigate through spatial environments, grid cells exhibit firing fields that are arranged in a triangular grid pattern. Direct recordings of grid cells from the human brain are rare. Hence, functional magnetic resonance imaging (fMRI) studies proposed an indirect measure of entorhinal grid-cell activity, quantified as hexadirectional...
Physical exercise studies are generally underrepresented in young adulthood. Seventeen subjects were randomized into an intervention group (24.2 ± 3.9 years; 3 trainings/week) and 10 subjects into a passive control group (23.7 ± 4.2 years), over a duration of 6 months. Every two months, performance diagnostics, computerized spatial memory tests, an...
Background
The entorhinal cortex (EC) is the first cortical region affected by tauopathy in Alzheimer’s disease (AD) and is implicated in path integration. In early stages of AD, path integration deficits could be present, even before overt memory deficits. Furthermore, path integration deficits are found among older individuals at risk for AD, suc...
Deep-brain stimulation (DBS) is a potential novel treatment for memory dysfunction. Current attempts to enhance memory focus on stimulating human hippocampus or entorhinal cortex. However, an alternative strategy is to stimulate brain areas providing modulatory inputs to medial temporal memory-related structures, such as the nucleus accumbens (NAc)...
When animals move through space, neurons in their entorhinal cortex activate periodically at multiple locations to form a map of the spatial environment. These grid cells may also map non-physical, conceptual spaces to support various other complex behaviors. Here, using intracranial recordings in neurosurgical patients performing an emotional memo...
Local field potentials (LFPs) can provide biomarkers of cognitive function at the meso-scale level of brain organization. LFPs represent the aggregation of thousands of transmembrane currents from local and non-local brain regions and it is thus still not understood how LFP fluctuations relate to action potentials of single neurons. Because these a...
Path integration is a spatial navigation ability that requires the integration of information derived from self-motion cues and stable landmarks, when available, to return to a previous location. Path integration declines with age and Alzheimer's disease (AD). Here, we sought to separate the effects of age and AD risk on path integration, with and...
Goal-directed navigation relies on both coarse and fine-grained coding of spatial distance between the current position of a navigating subject and a goal destination. However, the neural signatures underlying goal distance coding remain poorly understood. Using intracranial EEG recordings from the hippocampus of drug-resistant epilepsy patients wh...
Investigations of hippocampal functions have revealed a dizzying array of findings, from lesion-based behavioral deficits, to a diverse range of characterized neural activations, to computational models of putative functionality. Across these findings, there remains an ongoing debate about the core function of the hippocampus and the generality of...
Distinct lines of research in both humans and animals point to a specific role of the hippocampus in both spatial and episodic memory function. The discovery of concept cells in the hippocampus and surrounding medial-temporal lobe (MTL) regions suggests that the MTL maps physical and semantic spaces with a similar neural architecture. Here, we stud...
Visual working memory depends on both material-specific brain areas in ventral visual stream (VVS) that support the maintenance of stimulus representations and on regions in prefrontal cortex (PFC) that control these representations. These two areas putatively support bottom-up information processing vs. top-down control functions that rely on osci...
Repeated exposure to stress (chronic stress) can cause excess levels of circulating cortisol and has detrimental influences on various cognitive functions including long-term memory and navigation. However, it remains an open question whether chronic stress affects path integration, a navigational strategy that presumably relies on the functioning...
Grid cells are neurons in the entorhinal cortex that play a key role in spatial navigation. When subjects navigate through spatial environments, grid cells exhibit firing fields that are arranged in a triangular grid pattern. As direct recordings of grid cells from the human brain are only rarely possible, functional magnetic resonance imaging (fMR...
Alzheimer’s disease (AD) is associated with cognitive impairment, including spatial disorientation. Disorientation may be an early indicator of AD because spatial navigation relies on entorhinal cortex, the first cortical region affected by AD pathology. To test the hypothesis that spatial navigation declines in preclinical AD, we investigated age...
Memory for aversive events is central to survival but can become maladaptive in psychiatric disorders. Memory enhancement for emotional events is thought to depend on amygdala modulation of hippocampal activity. However, the neural dynamics of amygdala-hippocampal communication during emotional memory encoding remain unknown. Using simultaneous int...
Associative memory is the ability to encode and retrieve relations between different stimuli. To better understand its neural basis, we investigated whether associative memory involves precisely timed spiking of neurons in the medial temporal lobes that exhibit stimulus-specific tuning. Using single-neuron recordings from epilepsy patients performi...
Local field potentials (LFPs) can provide biomarkers of cognitive function at the meso-scale level of brain organization. LFPs represent the aggregation of thousands of transmembrane currents from local and non-local brain regions and it is thus still not understood how LFPfluctuations relate to action potentials of single neurons. Because these ac...
Background
The entorhinal cortex (EC) contains spatially modulated cells, so called grid cells, and plays a central role in spatial navigation. Studies show that tauopathy in the EC is already observed in the early stages of Alzheimer's disease (AD) and is responsible for impairments in spatial memory performance. Moreover, recent studies demonstra...
The hippocampus is implicated in novelty detection, thought to be important for regulating entry of information into long-term memory. Whether electrophysiological responses to novelty differ along the human hippocampal long axis is currently unknown. By recording from electrodes implanted longitudinally in the hippocampus of epilepsy patients, her...
Grid cells and theta oscillations are fundamental constituents of the brain's navigation system and have been described in the entorhinal cortex (EC). Recent fMRI studies reveal that the ventromedial prefrontal cortex (vmPFC) contains grid-like representations. However, the neural mechanisms underlying human vmPFC grid-like representations and thei...
Memory for aversive events is central to survival, but can also become maladaptive in psychiatric disorders. Emotional memory relies on the amygdala and hippocampus, but the neural dynamics of their communication during emotional memory encoding remain unknown. Using simultaneous intracranial recordings from both structures in human patients, we sh...
Interictal epileptiform discharges (IEDs) are a widely used biomarker in patients with epilepsy but lack specificity. It has been proposed that there are truly epileptogenic and less pathologic or even protective IEDs. Recent studies suggest that highly pathologic IEDs are characterized by high-frequency oscillations (HFOs). Here, we aimed to disse...
Effective seizure control remains challenging for about 30% of epilepsy patients who are resistant to present-day pharmacotherapy. Novel approaches that not only reduce the severity and frequency of seizures, but also have limited side effects are therefore desirable. Accordingly, various neuromodulation approaches such as cortical electrical stimu...
Human High-Frequency-Oscillations (HFO) in the ripple band are oscillatory brain activity in the frequency range between 80 and 250 Hz. HFOs may comprise different subgroups that either play a role in physiologic or pathologic brain functions. An exact differentiation between physiologic and pathologic HFOs would help elucidate their relevance for...
Alzheimer’s disease (AD) manifests with progressive memory loss and spatial disorientation. Neuropathological studies suggest early AD pathology in the entorhinal cortex (EC) of young adults at genetic risk for AD ( APOE ε4-carriers). Because the EC harbors grid cells, a likely neural substrate of path integration (PI), we examined PI performance i...
Distinct lines of research in both humans and animals point to a specific role of the hippocampus in both spatial and episodic memory function. The discovery of concept cells in the hippocampus and surrounding medial-temporal lobe (MTL) regions suggests that the MTL maps physical and semantic spaces with a similar neural architecture. Here, we stud...
Spatial navigation relies on neural systems that encode information about places, distances, and directions in relation to the external world or relative to the navigating organism. Since the proposal of cognitive maps, the neuroscience of navigation has focused on allocentric (world-referenced) neural representations including place, grid, and hea...
Alzheimer's disease (AD) manifests with progressive memory loss and spatial disorientation. Neuropathological studies suggest early AD pathology in the entorhinal cortex (EC) of young adults at genetic risk for AD (APOE ϵ4-carriers). Because the EC harbors grid cells, a likely neural substrate of path integration (PI), we examined PI performance in...
Humans are adept in simultaneously following multiple goals, but the neural mechanisms for maintaining specific goals and distinguishing them from other goals are incompletely understood. For short time scales, working memory studies suggest that multiple mental contents are maintained by theta-coupled reactivation, but evidence for similar mechani...
Recent evidence suggests that mesoscopic neural oscillations measured via intracranial electroencephalography exhibit spatial representations, which were previously only observed at the micro- and macroscopic level of brain organization. Specifically, theta (and gamma) oscillations correlate with movement, speed, distance, specific locations, and g...
The concept of stimulus-specific memory traces, or engrams, suggests that the fate of individual memories can be tracked via empirically observable brain states. Recent advances in neuroscience have made it possible to discern these brain states in various ways. In animals, transgenics and optogenetics have allowed identifying distinct cell populat...
Grid cells and theta oscillations are fundamental components of the brain’s navigation system. Grid cells provide animals and humans with a spatial map of the environment by exhibiting multiple firing fields arranged in a regular grid of equilateral triangles. This unique firing pattern presumably con- stitutes the neural basis for path integration...
The etiology of late onset Alzheimer's disease (LOAD) depends on multiple factors, among which the APOEɛ4 allele is the most adverse genetic determinant and conscientiousness represents an influential personality trait. A potential association of both factors with brain structure in young adulthood may constitute a constellation that sets the cours...
Background / Purpose:
An early diagnosis of Alzheimer's disease is of considerable interest, especially in healthy people who carry Alzheimer's genetic risk factors; among which the ε4 allele of the ApoE protein is the most relevant genetic determinant. The entorhinal cortex is the first brain region affected by Alzheimer's disease and it has bee...
Background
A recent study yielded first evidence that personality plays an important role in explaining the influence of a prominent APOE polymorphism on cognitive decline and Alzheimer’s disease (AD) in elderly humans. Adding to this, two earlier studies examined this polymorphism in the context of individual differences in temperament traits in y...