Arrow Research search

Author name cluster

Thomas Gruber

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

13 papers
1 author row

Possible papers

13

YNIMG Journal 2026 Journal Article

Encoding of modality-specific face engrams promotes distinct recruitment of mnemonic processing mechanisms: A mobile-EEG study comparing encoding and retrieval of 2D and 3D avatars under virtual reality conditions

  • Merle Sagehorn
  • Joanna Kisker
  • Rainer Düsing
  • Thomas Gruber
  • Benjamin Schöne

The processing of faces under realistic virtual conditions engages distinct cognitive mechanisms that are attuned to their inherent conceptual and socially relevant characteristics. To more closely approximate real-life circumstances of personal encounters, the degree of realism is increased by situational context and further varied with respect to the stimuli's dimensionality and dynamics. To this end, a mobile-EEG study was conducted in which the participants encountered dynamic 3D virtual avatars and static 2D images of the avatars and were then asked to recognize their faces in a 2D old/new task, all within the same virtual environment. Stimulus processing during encoding and mnemonic mechanisms engaged during retrieval were investigated based on relevant event-related potentials (ERPs) as well as induced oscillatory responses. Although cognitive load did not differ between processing 2D and 3D faces, as indexed by comparable induced theta-band responses, recognition performance during retrieval showed that 3D faces were recognized more accurately. Investigation of the underlying cognitive processing revealed distinct recruitment of mnemonic mechanisms for the retrieval of 3D encoded faces, reflected in the face-specific frontal and centro-parietal ERP old/new effects (N400f, P600f) and characteristic responses in the induced theta and alpha bands. Specifically, the reactivation of the 3D face representations was characterized by concurrent identity-related and semantic recognition processing as well as increased attentional resource allocation. The realistic characteristics of the 3D faces, in terms of visual complexity and social quality, led to the formation of modality-specific engrams, which ultimately enabled better recognition of these faces than their 2D counterparts.

Details DOI

YNIMG Journal 2019 Journal Article

Memory entrainment by visually evoked theta-gamma coupling

  • Moritz Köster
  • Ulla Martens
  • Thomas Gruber

The wake human brain constantly encodes novel information and integrates them into existing neuronal representations. It is posited that the formation of new memory traces is orchestrated by the synchronization of neuronal activity in the theta rhythm (3–8 Hz), theta coupled gamma activity (40–120 Hz), and decreases in the alpha rhythm (8–12 Hz). Critically, given the correlative nature of neurophysiological recordings, the functional relevance of oscillatory processes is not well understood. Here, we experimentally enhanced memory formation processes by a rhythmic visual stimulation at an individual theta frequency, in contrast to the stimulation at an individual alpha frequency. This memory entrainment effect was not explained by theta power per se, but was driven by a visually evoked theta-gamma coupling pattern. This underlines the functional role of the theta rhythm and the theta-gamma neuronal code in human episodic memory. The entrainment of mnemonic network mechanisms by a visual stimulation technique provides a proof of concept that visual pacemakers can entrain complex cognitive processes in the wake human brain.

Details DOI

YNIMG Journal 2017 Journal Article

Oscillatory EEG dynamics underlying automatic chunking during sentence processing

  • Corinna E. Bonhage
  • Lars Meyer
  • Thomas Gruber
  • Angela D. Friederici
  • Jutta L. Mueller

Sentences are easier to remember than random word sequences, likely because linguistic regularities facilitate chunking of words into meaningful groups. The present electroencephalography study investigated the neural oscillations modulated by this so-called sentence superiority effect during the encoding and maintenance of sentence fragments versus word lists. We hypothesized a chunking-related modulation of neural processing during the encoding and retention of sentences (i. e. , sentence fragments) as compared to word lists. Time–frequency analysis revealed a two-fold oscillatory pattern for the memorization of sentences: Sentence encoding was accompanied by higher delta amplitude (4Hz), originating both from regions processing syntax as well as semantics (bilateral superior/middle temporal regions and fusiform gyrus). Subsequent sentence retention was reflected in decreased theta (6Hz) and beta/gamma (27–32Hz) amplitude instead. Notably, whether participants simply read or properly memorized the sentences did not impact chunking-related activity during encoding. Therefore, we argue that the sentence superiority effect is grounded in highly automatized language processing mechanisms, which generate meaningful memory chunks irrespective of task demands.

Details DOI

YNIMG Journal 2017 Journal Article

Visual cortical networks align with behavioral measures of context-sensitivity in early childhood

  • Moritz Köster
  • Johanna Castel
  • Thomas Gruber
  • Joscha Kärtner

This study investigates how visual cortical networks align with context-sensitivity, namely the relative focus on the object versus the background of a visual scene, in early childhood. Context-sensitivity was assessed by a picture description and a recognition memory task. To segregate object and background processing in the visual cortex in 5- and 7-year-old children, object and background were presented at different frequencies (12 Hz or 15 Hz), evoking disparate neuronal responses (steady state visually evoked potentials, SSVEPs) in the electroencephalogram. In younger compared to older children the background elicited higher SSVEPs. Visual cortical processing of object versus background was associated with behavioral measures for older but not for younger children. This relation was strongest for verbal descriptions and generalized to the cortical processing of abstract stimuli and object and background presented alone. Thus, visual cortical networks restructure and align with behavioral measures of context-sensitivity in early childhood.

Details DOI

YNIMG Journal 2014 Journal Article

Glutamatergic correlates of gamma-band oscillatory activity during cognition: A concurrent ER-MRS and EEG study

  • Níall Lally
  • Paul G. Mullins
  • Mark V. Roberts
  • Darren Price
  • Thomas Gruber
  • Corinna Haenschel

Frequency specific synchronisation of neuronal firing within the gamma-band (30–70Hz) appears to be a fundamental correlate of both basic sensory and higher cognitive processing. In-vitro studies suggest that the neurochemical basis of gamma-band oscillatory activity is based on interactions between excitatory (i. e. glutamate) and inhibitory (i. e. GABA) neurotransmitter concentrations. However, the nature of the relationship between excitatory neurotransmitter concentration and changes in gamma band activity in humans remains undetermined. Here, we examine the links between dynamic glutamate concentration and the formation of functional gamma-band oscillatory networks. Using concurrently acquired event-related magnetic resonance spectroscopy and electroencephalography, during a repetition-priming paradigm, we demonstrate an interaction between stimulus type (object vs. abstract pictures) and repetition in evoked gamma-band oscillatory activity, and find that glutamate levels within the lateral occipital cortex, differ in response to these distinct stimulus categories. Importantly, we show that dynamic glutamate levels are related to the amplitude of stimulus evoked gamma-band (but not to beta, alpha or theta or ERP) activity. These results highlight the specific connection between excitatory neurotransmitter concentration and amplitude of oscillatory response, providing a novel insight into the relationship between the neurochemical and neurophysiological processes underlying cognition.

Details DOI