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Garagnani M, Lucchese G, Tomasello R, Wennekers T, Pulvermüller F. A Spiking Neurocomputational Model of High-Frequency Oscillatory Brain Responses to Words and Pseudowords. Front Comput Neurosci 2017; 10:145. [PMID: 28149276 PMCID: PMC5241316 DOI: 10.3389/fncom.2016.00145] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/26/2016] [Indexed: 12/22/2022] Open
Abstract
Experimental evidence indicates that neurophysiological responses to well-known meaningful sensory items and symbols (such as familiar objects, faces, or words) differ from those to matched but novel and senseless materials (unknown objects, scrambled faces, and pseudowords). Spectral responses in the high beta- and gamma-band have been observed to be generally stronger to familiar stimuli than to unfamiliar ones. These differences have been hypothesized to be caused by the activation of distributed neuronal circuits or cell assemblies, which act as long-term memory traces for learned familiar items only. Here, we simulated word learning using a biologically constrained neurocomputational model of the left-hemispheric cortical areas known to be relevant for language and conceptual processing. The 12-area spiking neural-network architecture implemented replicates physiological and connectivity features of primary, secondary, and higher-association cortices in the frontal, temporal, and occipital lobes of the human brain. We simulated elementary aspects of word learning in it, focussing specifically on semantic grounding in action and perception. As a result of spike-driven Hebbian synaptic plasticity mechanisms, distributed, stimulus-specific cell-assembly (CA) circuits spontaneously emerged in the network. After training, presentation of one of the learned "word" forms to the model correlate of primary auditory cortex induced periodic bursts of activity within the corresponding CA, leading to oscillatory phenomena in the entire network and spontaneous across-area neural synchronization. Crucially, Morlet wavelet analysis of the network's responses recorded during presentation of learned meaningful "word" and novel, senseless "pseudoword" patterns revealed stronger induced spectral power in the gamma-band for the former than the latter, closely mirroring differences found in neurophysiological data. Furthermore, coherence analysis of the simulated responses uncovered dissociated category specific patterns of synchronous oscillations in distant cortical areas, including indirectly connected primary sensorimotor areas. Bridging the gap between cellular-level mechanisms, neuronal-population behavior, and cognitive function, the present model constitutes the first spiking, neurobiologically, and anatomically realistic model able to explain high-frequency oscillatory phenomena indexing language processing on the basis of dynamics and competitive interactions of distributed cell-assembly circuits which emerge in the brain as a result of Hebbian learning and sensorimotor experience.
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Affiliation(s)
- Max Garagnani
- Department of Computing, Goldsmiths, University of LondonLondon, UK
- Brain Language Laboratory, Department of Philosophy and Humanities, Freie Universität BerlinBerlin, Germany
| | - Guglielmo Lucchese
- Brain Language Laboratory, Department of Philosophy and Humanities, Freie Universität BerlinBerlin, Germany
| | - Rosario Tomasello
- Brain Language Laboratory, Department of Philosophy and Humanities, Freie Universität BerlinBerlin, Germany
- Berlin School of Mind and Brain, Humboldt Universität zu BerlinBerlin, Germany
| | - Thomas Wennekers
- Centre for Robotics and Neural Systems, University of PlymouthPlymouth, UK
| | - Friedemann Pulvermüller
- Brain Language Laboratory, Department of Philosophy and Humanities, Freie Universität BerlinBerlin, Germany
- Berlin School of Mind and Brain, Humboldt Universität zu BerlinBerlin, Germany
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Craddock M, Oppermann F, Müller MM, Martinovic J. Modulation of microsaccades by spatial frequency during object categorization. Vision Res 2016; 130:48-56. [PMID: 27876511 DOI: 10.1016/j.visres.2016.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/20/2016] [Accepted: 10/31/2016] [Indexed: 11/16/2022]
Abstract
The organization of visual processing into a coarse-to-fine information processing based on the spatial frequency properties of the input forms an important facet of the object recognition process. During visual object categorization tasks, microsaccades occur frequently. One potential functional role of these eye movements is to resolve high spatial frequency information. To assess this hypothesis, we examined the rate, amplitude and speed of microsaccades in an object categorization task in which participants viewed object and non-object images and classified them as showing either natural objects, man-made objects or non-objects. Images were presented unfiltered (broadband; BB) or filtered to contain only low (LSF) or high spatial frequency (HSF) information. This allowed us to examine whether microsaccades were modulated independently by the presence of a high-level feature - the presence of an object - and by low-level stimulus characteristics - spatial frequency. We found a bimodal distribution of saccades based on their amplitude, with a split between smaller and larger microsaccades at 0.4° of visual angle. The rate of larger saccades (⩾0.4°) was higher for objects than non-objects, and higher for objects with high spatial frequency content (HSF and BB objects) than for LSF objects. No effects were observed for smaller microsaccades (<0.4°). This is consistent with a role for larger microsaccades in resolving HSF information for object identification, and previous evidence that more microsaccades are directed towards informative image regions.
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Affiliation(s)
- Matt Craddock
- Institute of Psychology, University of Leipzig, Germany; School of Psychology, University of Leeds, UK
| | - Frank Oppermann
- Institute of Psychology, University of Leipzig, Germany; Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands
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Wynn JK, Roach BJ, Lee J, Horan WP, Ford JM, Jimenez AM, Green MF. EEG findings of reduced neural synchronization during visual integration in schizophrenia. PLoS One 2015; 10:e0119849. [PMID: 25785939 PMCID: PMC4364708 DOI: 10.1371/journal.pone.0119849] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 01/17/2015] [Indexed: 12/22/2022] Open
Abstract
Schizophrenia patients exhibit well-documented visual processing deficits. One area of disruption is visual integration, the ability to form global objects from local elements. However, most studies of visual integration in schizophrenia have been conducted in the context of an active attention task, which may influence the findings. In this study we examined visual integration using electroencephalography (EEG) in a passive task to elucidate neural mechanisms associated with poor visual integration. Forty-six schizophrenia patients and 30 healthy controls had EEG recorded while passively viewing figures comprised of real, illusory, or no contours. We examined visual P100, N100, and P200 event-related potential (ERP) components, as well as neural synchronization in the gamma (30-60 Hz) band assessed by the EEG phase locking factor (PLF). The N100 was significantly larger to illusory vs. no contour, and illusory vs. real contour stimuli while the P200 was larger only to real vs. illusory stimuli; there were no significant interactions with group. Compared to controls, patients failed to show increased phase locking to illusory versus no contours between 40-60 Hz. Also, controls, but not patients, had larger PLF between 30-40 Hz when viewing real vs. illusory contours. Finally, the positive symptom factor of the BPRS was negatively correlated with PLF values between 40-60 Hz to illusory stimuli, and with PLF between 30-40 Hz to real contour stimuli. These results suggest that the pattern of results across visual processing conditions is similar in patients and controls. However, patients have deficits in neural synchronization in the gamma range during basic processing of illusory contours when attentional demand is limited.
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Affiliation(s)
- Jonathan K. Wynn
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States of America
- Psychiatry and Biobehavioral Sciences, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Brian J. Roach
- Veterans Affairs San Francisco Medical Center, San Francisco, CA, United States of America
| | - Junghee Lee
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States of America
- Psychiatry and Biobehavioral Sciences, University of California Los Angeles, Los Angeles, CA, United States of America
| | - William P. Horan
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States of America
- Psychiatry and Biobehavioral Sciences, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Judith M. Ford
- Veterans Affairs San Francisco Medical Center, San Francisco, CA, United States of America
- University of California San Francisco, San Francisco, CA, United States of America
| | - Amy M. Jimenez
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States of America
| | - Michael F. Green
- Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, United States of America
- Psychiatry and Biobehavioral Sciences, University of California Los Angeles, Los Angeles, CA, United States of America
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Kosilo M, Wuerger SM, Craddock M, Jennings BJ, Hunt AR, Martinovic J. Low-level and high-level modulations of fixational saccades and high frequency oscillatory brain activity in a visual object classification task. Front Psychol 2014; 4:948. [PMID: 24391611 PMCID: PMC3867122 DOI: 10.3389/fpsyg.2013.00948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 11/30/2013] [Indexed: 11/24/2022] Open
Abstract
Until recently induced gamma-band activity (GBA) was considered a neural marker of cortical object representation. However, induced GBA in the electroencephalogram (EEG) is susceptible to artifacts caused by miniature fixational saccades. Recent studies have demonstrated that fixational saccades also reflect high-level representational processes. Do high-level as opposed to low-level factors influence fixational saccades? What is the effect of these factors on artifact-free GBA? To investigate this, we conducted separate eye tracking and EEG experiments using identical designs. Participants classified line drawings as objects or non-objects. To introduce low-level differences, contours were defined along different directions in cardinal color space: S-cone-isolating, intermediate isoluminant, or a full-color stimulus, the latter containing an additional achromatic component. Prior to the classification task, object discrimination thresholds were measured and stimuli were scaled to matching suprathreshold levels for each participant. In both experiments, behavioral performance was best for full-color stimuli and worst for S-cone isolating stimuli. Saccade rates 200–700 ms after stimulus onset were modulated independently by low and high-level factors, being higher for full-color stimuli than for S-cone isolating stimuli and higher for objects. Low-amplitude evoked GBA and total GBA were observed in very few conditions, showing that paradigms with isoluminant stimuli may not be ideal for eliciting such responses. We conclude that cortical loops involved in the processing of objects are preferentially excited by stimuli that contain achromatic information. Their activation can lead to relatively early exploratory eye movements even for foveally-presented stimuli.
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Affiliation(s)
- Maciej Kosilo
- School of Psychology, University of Aberdeen Aberdeen, UK ; Department of Psychology, City University London London, UK
| | - Sophie M Wuerger
- Department of Psychological Sciences, Institute of Psychology, Health and Society, University of Liverpool Liverpool, UK
| | - Matt Craddock
- Institute for Experimental Psychology and Methods, University of Leipzig Leipzig, Germany
| | - Ben J Jennings
- School of Psychology, University of Aberdeen Aberdeen, UK ; Department of Ophthalmology, McGill Vision Research, McGill University Montreal, QC, Canada
| | - Amelia R Hunt
- School of Psychology, University of Aberdeen Aberdeen, UK
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Hassler U, Friese U, Martens U, Trujillo-Barreto N, Gruber T. Repetition priming effects dissociate between miniature eye movements and induced gamma-band responses in the human electroencephalogram. Eur J Neurosci 2013; 38:2425-33. [DOI: 10.1111/ejn.12244] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 03/18/2013] [Accepted: 04/03/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Uwe Hassler
- Institute of Psychology; Osnabrück University; Seminarstrasse 20 49074 Osnabrück Germany
| | - Uwe Friese
- Department of Neurophysiology and Pathophysiology; University Medical Center Hamburg-Eppendorf; Hamburg Germany
| | - Ulla Martens
- Institute of Psychology; Osnabrück University; Seminarstrasse 20 49074 Osnabrück Germany
| | | | - Thomas Gruber
- Institute of Psychology; Osnabrück University; Seminarstrasse 20 49074 Osnabrück Germany
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Induced gamma-band response to fragmented images: An intracranial EEG study. Neuropsychologia 2013; 51:584-91. [PMID: 23320980 DOI: 10.1016/j.neuropsychologia.2013.01.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 12/11/2012] [Accepted: 01/05/2013] [Indexed: 11/21/2022]
Abstract
Induced gamma-band response (iGBR) has been linked to coherent perception of images and is thought to represent the synchronisation of neuronal populations mediating binding of elements composing the image and the comparisons with memory for proper recognition. This study uses fragmented images with intracranial electroencephalography to investigate the precise spatio-temporal dynamic of iGBR elicited by the recognition of objects presented for the first time and 24h later. Results show an increased iGBR at recognition in regions involved in bottom-up processes such as the cuneus and the lateral occipital complex. Top-down facilitation involved the lingual gyrus, the precuneus and the superior parietal lobule when images were presented for the first time. Twenty-four hours later, top-down facilitation was mediated by frontal areas involved in retrieval from episodic memory. This study showed that the classically reported iGBR is related to object recognition and that top-down processes vary according to task demand.
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