About

Simon Fischer-Baum is an Associate Professor at Rice University and a member of the Ken Kennedy Institute. His research interests include cognitive and affective neuroscience, with a focus on written and spoken language processing, short-term memory, and cognitive neuropsychology. He holds a B.A. in Neuroscience and Behavior from Columbia University, obtained in 2003, and a Ph.D. in Cognitive Science from Johns Hopkins University, earned in 2010. His academic background and research focus contribute to understanding the neural mechanisms underlying language and memory functions.

Selected publications

• The role of spatial processing in verbal serial order working memory

  Cognitive Affective & Behavioral Neuroscience · 2025-01-15 · 9 citations

  articleOpen accessSenior author

  In a sequence, at least two aspects of information-the identity of items and their serial order-are maintained and supported by distinct working memory (WM) capacities. Verbal serial order WM is modulated by spatial processing, reflected in the Spatial Position Association of Response Codes (SPoARC) effect-the left-beginning, right-end positional association between space and serial position of verbal WM memoranda. We investigated the individual differences in this modulation with both behavioral and neurobiological approaches. We administered a battery of seven behavioral tasks with 160 healthy adults and collected resting-state fMRI data from a subset of 25 participants. With a multilevel mixed-effects modeling approach, we found that the SPoARC effect's magnitude predicts individual differences in verbal serial order WM capacity and is related to spatial item WM capacity. With a graph-theory-based analytic approach, this interaction between verbal serial order WM and spatial WM was corroborated in that the level of interaction between corresponding cortical regions (indexed by modularity) was predictive of the magnitude of the SPoARC effect. Additionally, the modularity of cortical regions associated with verbal serial order WM and spatial attention predicted the SPoARC effect's magnitude, indicating the involvement of spatial attention in this modulation. Together, our findings highlight multiple sources of the interplay between verbal serial order WM and spatial processing.

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• Reorganization of motor functions within visuomotor networks subsequent to somatosensory cortical damage

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-02-26

  preprintOpen access

  Abstract Somatosensory inputs are critical to motor control. Animal studies have shown that primary somatosensory lesions cause sensorimotor deficits along with disrupted organization in primary motor cortex (M1). How does damage in primary somatosensory cortex (S1) influence motor networks in humans? Using fMRI, we examined two individuals with extensive damage to left somatosensory cortex, but primarily intact motor cortex and preserved motor abilities. Given left S1 damage, tactile detection and localization were impaired for the contralesional hand in both individuals. When moving the contralesional hand, LS, with near complete damage to the S1 hand area, showed increased activation in ipsilesional putamen and deactivation in contralesional cerebellum relative to age-matched controls. These findings demonstrate influences of S1 damage to subcortical sensorimotor areas that are distant from the lesion site, and a potential reweighting of the motor network with increased action selection in putamen and inhibition of sensory prediction in cerebellum in the face of sensory loss. In contrast, RF, who had a small island of spared S1 in the hand area, showed greater activation in contralesional S1 for movement versus rest. This same region was also activated by pure somatosensory stimulation in a second experiment, suggesting that the spared S1 area in RF still subserves sensorimotor processing. Finally, the right middle occipital gyrus was more strongly activated in both individuals compared with controls, suggesting a potential reliance on visual imagery in the face of degraded sensory feedback.

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• Reweighting of visuomotor areas during motor processing subsequent to somatosensory cortical damage

  NeuroImage · 2025-06-17

  articleOpen access

  • We examined motor reorganization in cases with severe left S1 damage but intact M1. • We observed increased activity in putamen, deactivation in cerebellum. • Both cases demonstrated higher activation in visual brain regions vs. controls. • One case with some spared S1 showed cross-hemispheric S1 reorganization. • These cases show long-range reweighting of visuomotor networks after S1 damage. Somatosensory inputs are critical to motor control. Animal studies have shown that primary somatosensory lesions cause sensorimotor deficits along with disrupted organization in primary motor cortex (M1). How does damage in primary somatosensory cortex (S1) influence motor networks in humans? Using fMRI, we examined two individuals, LS and RF, who had extensive damage to left somatosensory cortex, but primarily intact motor cortex and preserved motor abilities. Given left S1 damage, tactile detection and localization were impaired for the contralesional hand in both individuals. When moving the contralesional hand, LS, with near complete damage to S1 hand area, showed increased activation in ipsilesional putamen and deactivation in contralesional cerebellum relative to age-matched controls. These findings demonstrate influences of S1 damage to subcortical sensorimotor areas that are distant from the lesion site, and a potential reweighting of the motor network with increased action selection in putamen and inhibition of sensory prediction in cerebellum in the face of sensory loss. In contrast, RF, who had a small island of spared S1 in the hand area, showed greater activation in contralesional S1 for movement versus rest. This same region was also activated by pure somatosensory stimulation in a second experiment, suggesting that the spared S1 area in RF still subserves sensorimotor processing. Finally, the right middle occipital gyrus was more strongly activated in both individuals compared with controls, suggesting the potential reliance on visual imagery in the face of degraded sensory feedback.

  PublisherDOI

• On the role of stems and prefixes in reading complex nonwords: Evidence from individuals with and without acquired dyslexia

  Cognitive Neuropsychology · 2024-11-16 · 1 citations

  articleOpen accessSenior author

  ); and prefixed and non-prefixed filler words. The unimpaired readers responded fastest to nonwords containing two morphemes (prefix + stem), slower to nonwords with one morpheme (non-prefix + stem; prefix + non-stem), and slowest in the non-morphemic control condition (non-prefix + non-stem), providing evidence for the added benefit of prefixes and stems during reading. The five reading impaired individuals showed facilitatory morpheme effects across both tasks, but stem-effects were more robust than affix-effects. There was no difference between the prefixed and non-prefixed words in any of the data. The impact of morphological structure on nonword reading and repetition points to the important role of morphemes across different modalities..

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• Exploring the Dynamics Underlying Taxonomic and Thematic Semantic Organization in Picture Naming

  SSRN Electronic Journal · 2024-01-01

  preprintOpen accessSenior author
  PublisherDOI

• A shared serial order system for verbal working memory and language production: evidence from aphasia

  Cognitive Neuropsychology · 2024-08-17 · 2 citations

  articleOpen accessSenior author

  Many aspects of human performance require producing sequences of items in serial order. The current study takes a multiple-case approach to investigate whether the system responsible for serial order is shared across cognitive domains, focusing on working memory (WM) and word production. Serial order performance in three individuals with post-stroke language and verbal WM disorders (hereafter persons with aphasia, PWAs) were assessed using recognition and recall tasks for verbal and visuospatial WM, as well as error analyses in spoken and written production tasks to assess whether there was a tendency to produce the correct phonemes/letters in the wrong order. One PWA exhibited domain-specific serial order deficits in verbal and visuospatial WM. The PWA with verbal serial order WM deficit made more serial order errors than expected by chance in both repetition and writing-to-dictation tasks, whereas the other two PWAs showed no serial order deficits in verbal WM and production tasks. These findings suggest separable serial order systems for verbal and visuospatial WM and a shared system for serial order processing in verbal WM and word production. Implications for the domain-generality of WM, its connection to language production, and serial order processing across cognitive functionssc are discussed.

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• The primacy of taxonomic semantic organization over thematic semantic organization during picture naming

  Cognition · 2024-09-13 · 6 citations

  articleSenior authorCorresponding
  PublisherDOI

• 149 Dynamical Network State Sequences for Human Language Production

  Neurosurgery · 2024-03-15 · 1 citations

  article

  INTRODUCTION: Speech requires the selection of a conceptual representation, the construction of a word form, and the execution of a complex articulatory plan. Investigating this global system requires high-resolution recordings with an analytic approach to resolve discrete cognitive states. We integrated autoregressive hidden Markov models to resolve trial-by-trial state transition sequences in distributed networks derived from a large-scale electrocorticographic dataset with complete coverage of language-dominant cortex. METHODS: Intracranial electrodes (n = 25810, 134 patients), including both surface grids and stereotactic depths, were implanted for the evaluation of epilepsy. Patients performed picture naming of common objects and underwent systematic cortical stimulation mapping of language function. We used cross-validated autoregressive hidden Markov models – combining the interpretability of multivariate autoregressive analysis with the nonlinear embedding of the switching Markov characteristic – to distinguish cognitive states defined by causal interactional motifs of distributed cortical substrates and to simulate in silico lesions of dynamical network structures. RESULTS: We created a detailed spatiotemporal atlas of word production spanning the entire language-dominant cortex. From this map, we resolved network dynamics comprising sequences of state space transitions for each word articulated. This identified five essential states for speech production, each defined by a unique pattern of directed interactions within the language network. We then derived a computational lesion model for state dynamics and compared its predictions with causal perturbation by direct cortical stimulation. We assembled a global dynamical state model for language production and resolved the fine-scale interregional dynamics of conceptualization and lexical access. CONCLUSIONS: The distributed network dynamics detailed within this comprehensive interactional map of speech production advance our understanding of how both local and disconnection injuries yield complex neurological deficits, facilitating the development of novel therapeutic approaches for aphasia.

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• Critical role of the ventral temporal lobe in naming

  Epilepsia · 2023-02-20 · 26 citations

  articleOpen access

  OBJECTIVE: Lexical retrieval deficits are characteristic of a variety of different neurological disorders. However, the exact substrates responsible for this are not known. We studied a large cohort of patients undergoing surgery in the dominant temporal lobe for medically intractable epilepsy (n = 95) to localize brain regions that were associated with anomia. METHODS: We performed a multivariate voxel-based lesion-symptom mapping analysis to correlate surgical lesions within the temporal lobe with changes in naming ability. Additionally, we used a surface-based mixed-effects multilevel analysis to estimate group-level broadband gamma activity during naming across a subset of patients with electrocorticographic recordings and integrated these results with lesion-deficit findings. RESULTS: We observed that ventral temporal regions, centered around the middle fusiform gyrus, were significantly associated with a decline in naming. Furthermore, we found that the ventral aspect of temporal lobectomies was linearly correlated to a decline in naming, with a clinically significant decline occurring once the resection extended 6 cm from the anterior tip of the temporal lobe on the ventral surface. On electrocorticography, the majority of these cortical regions were functionally active following visual processing. These loci coincide with the sites of susceptibility artifacts during echoplanar imaging, which may explain why this region has been previously underappreciated as the locus responsible for postoperative naming deficits. SIGNIFICANCE: Taken together, these data highlight the crucial contribution of the ventral temporal cortex in naming and its important role in the pathophysiology of anomia following temporal lobe resections. As such, surgical strategies should attempt to preserve this region to mitigate postoperative language deficits.

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• Representational Similarity Analysis for Tracking Neural Correlates of Haptic Learning on a Multimodal Device

  IEEE Transactions on Haptics · 2023-07-01 · 2 citations

  articleOpen access

  A goal of wearable haptic devices has been to enable haptic communication, where individuals learn to map information typically processed visually or aurally to haptic cues via a process of cross-modal associative learning. Neural correlates have been used to evaluate haptic perception and may provide a more objective approach to assess association performance than more commonly used behavioral measures of performance. In this article, we examine Representational Similarity Analysis (RSA) of electroencephalography (EEG) as a framework to evaluate how the neural representation of multifeatured haptic cues changes with association training. We focus on the first phase of cross-modal associative learning, perception of multimodal cues. A participant learned to map phonemes to multimodal haptic cues, and EEG data were acquired before and after training to create neural representational spaces that were compared to theoretical models. Our perceptual model showed better correlations to the neural representational space before training, while the feature-based model showed better correlations with the post-training data. These results suggest that training may lead to a sharpening of the sensory response to haptic cues. Our results show promise that an EEG-RSA approach can capture a shift in the representational space of cues, as a means to track haptic learning.

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