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Horwitz A, Mortensen EL, Osler M, Fagerlund B, Lauritzen M, Benedek K. Passive Double-Sensory Evoked Coherence Correlates with Long-Term Memory Capacity. Front Hum Neurosci 2017; 11:598. [PMID: 29311868 PMCID: PMC5735981 DOI: 10.3389/fnhum.2017.00598] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 11/24/2017] [Indexed: 01/22/2023] Open
Abstract
HIGHLIGHTS Memory correlates with the difference between single and double-sensory evoked steady-state coherence in the gamma range (ΔC).The correlation is most pronounced for the anterior brain region (ΔCA ).The correlation is not driven by birth size, education, speed of processing, or intelligence.The sensitivity of ΔCA for detecting low memory capacity is 90%. Cerebral rhythmic activity and oscillations are important pathways of communication between cortical cell assemblies and may be key factors in memory. We asked whether memory performance is related to gamma coherence in a non-task sensory steady-state stimulation. We investigated 40 healthy males born in 1953 who were part of a Danish birth cohort study. Coherence was measured in the gamma range in response to a single-sensory visual stimulation (36 Hz) and a double-sensory combined audiovisual stimulation (auditive: 40 Hz; visual: 36 Hz). The individual difference in coherence (ΔC) between the bimodal and monomodal stimulation was calculated for each subject and used as the main explanatory variable. ΔC in total brain were significantly negatively correlated with long-term verbal recall. This correlation was pronounced for the anterior region. In addition, the correlation between ΔC and long-term memory was robust when controlling for working memory, as well as a wide range of potentially confounding factors, including intelligence, length of education, speed of processing, visual attention and executive function. Moreover, we found that the difference in anterior coherence (ΔCA ) is a better predictor of memory than power in multivariate models. The sensitivity of ΔCA for detecting low memory capacity is 92%. Finally, ΔCA was also associated with other types of memory: verbal learning, visual recognition, and spatial memory, and these additional correlations were also robust enough to control for a range of potentially confounding factors. Thus, the ΔC is a predictor of memory performance may be useful in cognitive neuropsychological testing.
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Affiliation(s)
- Anna Horwitz
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.,Department of Clinical Neurophysiology, Rigshospitalet - Glostrup, Glostrup, Denmark
| | - Erik L Mortensen
- Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.,Department of Public Health, University of Copenhagen, Copenhagen, Denmark
| | - Merete Osler
- Department of Public Health, University of Copenhagen, Copenhagen, Denmark.,Research Center for Prevention and Health, Rigshospitalet - Glostrup, Glostrup, Denmark
| | - Birgitte Fagerlund
- Center for Neuropsychiatric Schizophrenia Research, Psychiatric Center Glostrup, Glostrup, Denmark.,Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research, Psychiatric Center Glostrup, Glostrup, Denmark
| | - Martin Lauritzen
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.,Department of Clinical Neurophysiology, Rigshospitalet - Glostrup, Glostrup, Denmark
| | - Krisztina Benedek
- Department of Clinical Neurophysiology, Rigshospitalet - Glostrup, Glostrup, Denmark
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Wang GY, Kydd RR, Russell BR. Quantitative EEG and Low-Resolution Electromagnetic Tomography (LORETA) Imaging of Patients Undergoing Methadone Treatment for Opiate Addiction. Clin EEG Neurosci 2016; 47:180-7. [PMID: 26002855 DOI: 10.1177/1550059415586705] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 04/20/2015] [Indexed: 11/16/2022]
Abstract
Methadone maintenance treatment (MMT) has been used as a treatment for opiate dependence since the mid-1960s. Evidence suggests that methadone binds to mu opiate receptors as do other opiates and induces changes in neurophysiological function. However, little is known, about how neural activity within the higher frequency gamma band (>30 Hz) while at rest changes in those stabilized on MMT despite its association with the excitation-inhibition balance within pyramidal-interneuron networks. Our study investigated differences in resting gamma power (37-41 Hz) between patients undergoing MMT for opiate dependence, illicit opiate users, and healthy controls subjects. Electroencephalographic data were recorded from 26 sites according to the international 10-20 system. Compared with the healthy controls subjects, people either undergoing MMT (mean difference [MD] = 0.32, 95% CI = 0.09-0.55, P < .01) or currently using illicit opiates (MD = 0.31, 95% CI = 0.06-0.56, P = .01) exhibited significant increased gamma power. The sLORETA (standardized low-resolution electromagnetic tomography) between-group comparison revealed dysfunctional neuronal activity in the occipital, parietal, and frontal lobes in the patients undergoing MMT. A more severe profile of dysfunction was observed in those using illicit opiates. Our findings suggest that long-term exposure to opioids is associated with disrupted resting state network, which may be reduced after MMT.
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Affiliation(s)
- Grace Y Wang
- Department of Psychology, Auckland University of Technology, Auckland, New Zealand
| | - Robert R Kydd
- Centre for Brain Research, University of Auckland, Auckland, New Zealand Department of Psychological Medicine, University of Auckland, Auckland, New Zealand
| | - Bruce R Russell
- Centre for Brain Research, University of Auckland, Auckland, New Zealand School of Pharmacy, University of Auckland, Auckland, New Zealand
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3
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Tan HRM, Lana L, Uhlhaas PJ. High-frequency neural oscillations and visual processing deficits in schizophrenia. Front Psychol 2013; 4:621. [PMID: 24130535 PMCID: PMC3793130 DOI: 10.3389/fpsyg.2013.00621] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 08/23/2013] [Indexed: 12/30/2022] Open
Abstract
Visual information is fundamental to how we understand our environment, make predictions, and interact with others. Recent research has underscored the importance of visuo-perceptual dysfunctions for cognitive deficits and pathophysiological processes in schizophrenia. In the current paper, we review evidence for the relevance of high frequency (beta/gamma) oscillations towards visuo-perceptual dysfunctions in schizophrenia. In the first part of the paper, we examine the relationship between beta/gamma band oscillations and visual processing during normal brain functioning. We then summarize EEG/MEG-studies which demonstrate reduced amplitude and synchrony of high-frequency activity during visual stimulation in schizophrenia. In the final part of the paper, we identify neurobiological correlates as well as offer perspectives for future research to stimulate further inquiry into the role of high-frequency oscillations in visual processing impairments in the disorder.
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Affiliation(s)
- Heng-Ru May Tan
- Institute of Neuroscience and Psychology, College of Science and Engineering and College of Medical, Veterinary and Life Sciences, University of Glasgow Glasgow, UK
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4
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Abstract
It is becoming increasingly apparent that brain oscillations in various frequency bands play important roles in perceptual and attentional processes. Understandably, most of the associated experimental evidence comes from human or animal electrophysiological studies, allowing direct access to the oscillatory activities. However, such periodicities in perception and attention should, in theory, also be observable using the proper psychophysical tools. Here, we review a number of psychophysical techniques that have been used by us and other authors, in successful and sometimes unsuccessful attempts, to reveal the rhythmic nature of perceptual and attentional processes. We argue that the two existing and largely distinct debates about discrete vs. continuous perception and parallel vs. sequential attention should in fact be regarded as two facets of the same question: how do brain rhythms shape the psychological operations of perception and attention?
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Affiliation(s)
- Rufin Vanrullen
- Centre de Recherche Cerveau et Cognition, Université Paul Sabatier, Université de Toulouse Toulouse, France
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5
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Aissani C, Cottereau B, Dumas G, Paradis AL, Lorenceau J. Magnetoencephalographic signatures of visual form and motion binding. Brain Res 2011; 1408:27-40. [PMID: 21782159 DOI: 10.1016/j.brainres.2011.05.051] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 05/13/2011] [Accepted: 05/20/2011] [Indexed: 11/26/2022]
Abstract
This study investigates neural magneto-encephalographic (MEG) correlates of visual form and motion binding. Steady-state visual evoked fields (SSVEF) were recorded in MEG while observers reported their bound or unbound perception of moving bars arranged in a square shape. By using pairs of oscillating vertical and horizontal bars, "frequency-tagged" at f1 and f2, we identified a region with enhanced sustained power at 2f1+2f2 intermodulation frequency correlated with perceptual reports. Intermodulation power is more important during perceptual form/motion integration than during the perceptual segmentation of the stimulus into individual component motions, indicating that intermodulation frequency power is a neuromarker of form/motion integration. Source reconstruction of cortical activities at the relevant frequencies further reveals well segregated activity in the occipital lobe at the fundamental of the stimulation, f1 and f2, widely spread activity at 2f1 and 2f2 and a focal activity in the medial part of the right precentral sulcus region at the intermodulation component, 2f1+2f2. The present findings indicate that motion tagging provides a powerful way of investigating the processes underlying visual form/motion binding non-invasively in humans.
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Affiliation(s)
- Charles Aissani
- CRICM, Cogimage, Université Pierre and Marie Curie, UMR 7225, CNRS, INSERM, 47 Bd de l'Hôpital, 75013 Paris, France
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Differential effects of isoflurane on high-frequency and low-frequency γ oscillations in the cerebral cortex and hippocampus in freely moving rats. Anesthesiology 2011; 114:588-95. [PMID: 21293253 DOI: 10.1097/aln.0b013e31820ad3f9] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Cortical γ oscillations are thought to play a role in conscious cognitive functions. Suppression of 40-Hz γ activity was implicated in the loss of consciousness during general anesthesia. However, several experimental studies found that γ oscillations were preserved in anesthesia. The authors investigated the concentration-dependent effect of isoflurane on spontaneous γ oscillations in two frequency bands and three distinct brain regions in the rat. METHODS Adult Sprague-Dawley rats were chronically implanted with epidural and coaxial depth electrodes to record cortical field potentials in frontal cortex, visual cortex, and hippocampus in waking and at steady-state isoflurane concentrations of 0.4, 0.8, and 1.2%. The γ power was calculated for the frequency bands 30-50 and 70-140 Hz. Temporal variation and interregional synchrony of γ activity were analyzed using wavelet transform. Loss of consciousness was indexed by the loss of righting reflex. RESULTS Rats lost their righting reflex at 0.8 ± 0.1% isoflurane. High-frequency γ power was decreased by isoflurane in a concentration-dependent manner (P < 0.001, 50% decrease at 0.8% isoflurane) in all brain regions. Low-frequency γ power was unaffected by isoflurane. The duration and interregional synchrony of high-frequency γ bursts was also reduced (P l < 0.001, 40% decrease at 0.8% isoflurane). CONCLUSIONS Distinction between high- and low-frequency γ bands is important when evaluating the effect of general anesthetics on brain electrical activity. Spontaneous 40-Hz γ power does not indicate the state of consciousness. The attenuation and interregional desynchronization of high-frequency γ oscillations appear to correlate with the loss of consciousness.
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Resting frontal gamma power at 16, 24 and 36 months predicts individual differences in language and cognition at 4 and 5 years. Behav Brain Res 2011; 220:263-70. [PMID: 21295619 DOI: 10.1016/j.bbr.2011.01.048] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 01/25/2011] [Accepted: 01/27/2011] [Indexed: 11/24/2022]
Abstract
Gamma activity has been linked to a variety of different cognitive processes and exists in both transient and persistent forms. Across studies, different brain regions have been suggested to contribute to gamma activity. Multiple studies have shown that the function of gamma oscillations may be related to temporal binding of early sensory information to relevant top-down processes. Given this hypothesis, we expected gamma oscillations to subserve general brain mechanisms that contribute to the development of cognitive and linguistic systems. The present study aims to examine the predictive relations between resting-state cortical gamma power density at a critical point in language and cognitive acquisition (i.e. 16, 24 and 36 months), and cognitive and language output at ages 4 and 5 years. Our findings show that both 24- and 36-month gamma power are significantly correlated with later language scores, notably Non-Word Repetition. Further, 16-, 24- and 36-month gamma were all significantly correlated with 4-year PLS-3 and CELF-P sentence structure scores. Although associations reported here do not reflect a direct cause and effect of early resting gamma power on later language outcomes, capacity to generate higher power in the gamma range at crucial developmental periods may index better modulation of attention and allow easier access to working memory, thus providing an advantage for overall development, particularly in the linguistic domain. Moreover, measuring abilities at times when these abilities are still emergent may allow better prediction of later outcomes.
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Schadow J, Dettler N, Paramei GV, Lenz D, Fründ I, Sabel BA, Herrmann CS. Impairments of Gestalt perception in the intact hemifield of hemianopic patients are reflected in gamma-band EEG activity. Neuropsychologia 2008; 47:556-68. [PMID: 18996403 DOI: 10.1016/j.neuropsychologia.2008.10.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 09/26/2008] [Accepted: 10/03/2008] [Indexed: 10/21/2022]
Abstract
Gamma-band responses (GBRs) are associated with Gestalt perception processes. In the present EEG study, we investigated the effects of perceptual grouping on the visual GBR in the perimetrically intact visual field of patients with homonymous hemianopia and compared them to healthy participants. All observers were presented either random arrays of Gabor elements or arrays with an embedded circular arrangement. For the hemianopic patients, the circle was presented in their intact hemifield only. For controls, the hemifield for the circle presentation was counterbalanced across subjects. The participants were instructed to detect the circle by pressing a corresponding button. A wavelet transform based on Morlet wavelets was employed for the calculation of oscillatory GBRs. The early evoked GBR exhibited a larger amplitude and shorter latency for the healthy group compared to hemianopic patients and was associated with behavioral measures. The late total GBR between 200 and 400ms after stimulus onset was significantly increased for Gestalt-like patterns in healthy participants. This effect was not manifested in patients. The present findings indicate deficits in the early and late visual processing of Gestalt patterns even in the intact hemifield of hemianopic patients compared to healthy participants.
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Affiliation(s)
- Jeanette Schadow
- Department of Biological Psychology, Otto-von-Guericke-University of Magdeburg, Germany
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Cocchi L, Schenk F, Volken H, Bovet P, Parnas J, Vianin P. Visuo-spatial processing in a dynamic and a static working memory paradigm in schizophrenia. Psychiatry Res 2007; 152:129-42. [PMID: 17512986 DOI: 10.1016/j.psychres.2006.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Revised: 12/23/2005] [Accepted: 02/05/2006] [Indexed: 10/23/2022]
Abstract
Recent findings suggest that the visuo-spatial sketchpad (VSSP) may be divided into two sub-components processing dynamic or static visual information. This model may be useful to elucidate the confusion of data concerning the functioning of the VSSP in schizophrenia. The present study examined patients with schizophrenia and matched controls in a new working memory paradigm involving dynamic (the Ball Flight Task - BFT) or static (the Static Pattern Task - SPT) visual stimuli. In the BFT, the responses of the patients were apparently based on the retention of the last set of segments of the perceived trajectory, whereas control subjects relied on a more global strategy. We assume that the patients' performances are the result of a reduced capacity in chunking visual information since they relied mainly on the retention of the last set of segments. This assumption is confirmed by the poor performance of the patients in the static task (SPT), which requires a combination of stimulus components into object representations. We assume that the static/dynamic distinction may help us to understand the VSSP deficits in schizophrenia. This distinction also raises questions about the hypothesis that visuo-spatial working memory can simply be dissociated into visual and spatial sub-components.
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Affiliation(s)
- Luca Cocchi
- Institute of Sport science and physical education, Lausanne, Switzerland.
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10
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Vidal JR, Chaumon M, O'Regan JK, Tallon-Baudry C. Visual grouping and the focusing of attention induce gamma-band oscillations at different frequencies in human magnetoencephalogram signals. J Cogn Neurosci 2006; 18:1850-62. [PMID: 17069476 DOI: 10.1162/jocn.2006.18.11.1850] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Neural oscillatory synchrony could implement grouping processes, act as an attentional filter, or foster the storage of information in short-term memory. Do these findings indicate that oscillatory synchrony is an unspecific epiphenomenon occurring in any demanding task, or that oscillatory synchrony is a fundamental mechanism involved whenever neural cooperation is requested? If the latter hypothesis is true, then oscillatory synchrony should be specific, with distinct visual processes eliciting different types of oscillations. We recorded magnetoencephalogram (MEG) signals while manipulating the grouping properties of a visual display on the one hand, and the focusing of attention to memorize part of this display on the other hand. Grouping-related gamma oscillations were present in all conditions but modulated by the grouping properties of the stimulus (one or two groups) in the high gamma-band (70-120 Hz) at central occipital locations. Attention-related gamma oscillations appeared as an additional component whenever attentional focusing was requested in the low gamma-band (44-66 Hz) at parietal locations. Our results thus reveal the existence of a functional specialization in the gamma range, with grouping-related oscillations showing up at higher frequencies than attention-related oscillations. The pattern of oscillatory synchrony is thus specific of the visual process it is associated with. Our results further suggest that both grouping processes and focused attention rely on a common implementation process, namely, gamma-band oscillatory synchrony, a finding that could account for the fact that coherent percepts are more likely to catch attention than incoherent ones.
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Affiliation(s)
- Juan R Vidal
- LENA CNRS UPR640, MEG-EEG Center Pitié-Salpétrière, Paris, France.
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Pammer K, Hansen P, Holliday I, Cornelissen P. Attentional shifting and the role of the dorsal pathway in visual word recognition. Neuropsychologia 2006; 44:2926-36. [PMID: 16950456 DOI: 10.1016/j.neuropsychologia.2006.06.028] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Revised: 06/15/2006] [Accepted: 06/17/2006] [Indexed: 11/30/2022]
Abstract
A substantial amount of evidence has been collected to propose an exclusive role for the dorsal visual pathway in the control of guided visual search mechanisms, specifically in the preattentive direction of spatial selection [Vidyasagar, T. R. (1999). A neuronal model of attentional spotlight: Parietal guiding the temporal. Brain Research and Reviews, 30, 66-76; Vidyasagar, T. R. (2001). From attentional gating in macaque primary visual cortex to dyslexia in humans. Progress in Brain Research, 134, 297-312]. Moreover, it has been suggested recently that the dorsal visual pathway is specifically involved in the spatial selection and sequencing required for orthographic processing in visual word recognition. In this experiment we manipulate the demands for spatial processing in a word recognition, lexical decision task by presenting target words in a normal spatial configuration, or where the constituent letters of each word are spatially shifted relative to each other. Accurate word recognition in the Shifted-words condition should demand higher spatial encoding requirements, thereby making greater demands on the dorsal visual stream. Magnetoencephalographic (MEG) neuroimaging revealed a high frequency (35-40Hz) right posterior parietal activation consistent with dorsal stream involvement occurring between 100 and 300ms post-stimulus onset, and then again at 200-400ms. Moreover, this signal was stronger in the shifted word condition, compared to the normal word condition. This result provides neurophysiological evidence that the dorsal visual stream may play an important role in visual word recognition and reading. These results further provide a plausible link between early stage theories of reading, and the magnocellular-deficit theory of dyslexia, which characterises many types of reading difficulty.
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Affiliation(s)
- Kristen Pammer
- The School of Psychology, The Australian National University, Canberra, ACT 0200, Australia.
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Nakatani H, van Leeuwen C. Transient synchrony of distant brain areas and perceptual switching in ambiguous figures. BIOLOGICAL CYBERNETICS 2006; 94:445-57. [PMID: 16532332 DOI: 10.1007/s00422-006-0057-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Accepted: 02/01/2006] [Indexed: 05/07/2023]
Abstract
We studied the relationship between perceptual switching in the Necker cube and long-distance transient phase synchronization in EEG. Transient periods of response related synchrony between parietal and frontal areas were observed. They start 800-600, ms prior to the switch response and occur in pairs. Four types of pairs could be distinguished, two of which are accompanied by transient alpha band activity in the occipital area. The results indicate that perceptual switching processes involve parietal and frontal areas; these are the ones that are normally associated with various cognitive processes. Sensory information in the visual areas is involved in some, but not in all, of switching processes. The intrinsic variability, as well as the participating areas, points to the role of strategic cognitive processes in perceptual switching.
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Affiliation(s)
- Hironori Nakatani
- Laboratory for Perceptual Dynamics, RIKEN Brain Science Institute 2-1, Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
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VanRullen R, Reddy L, Koch C. The continuous wagon wheel illusion is associated with changes in electroencephalogram power at approximately 13 Hz. J Neurosci 2006; 26:502-7. [PMID: 16407547 PMCID: PMC6674399 DOI: 10.1523/jneurosci.4654-05.2006] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Continuously moving objects sometimes appear to spontaneously reverse their motion direction. The mechanisms underlying this bistable phenomenon (the "continuous wagon wheel illusion") are heavily debated, but one interpretation suggests that motion information is perceived in discrete episodes at a rate between 10 and 15 Hz. Here, we asked observers to report the perceived direction of a continuously rotating wheel while 32-channel electroencephalogram (EEG) was recorded. We then separated periods of perceived true from illusory (reversed) motion and compared the EEG power spectrum under these two perceptually distinct yet physically identical conditions. The only reliable difference was observed approximately 13 Hz over centroparietal electrodes, independent of the temporal frequency of the wheel. Thus, it is likely to reflect internal processes rather than purely stimulus-driven activity. EEG power (13 Hz) decreased before the onset of illusory motion and increased before transitions back to real motion. Using this relationship, it was possible to predict above chance, on a trial-by-trial basis, the direction of the upcoming perceptual transition. These data are compatible with the idea that motion perception occurs in snapshots <100 ms in duration.
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Affiliation(s)
- Rufin VanRullen
- Centre National de la Recherche Scientifique, Centre de Recherche Cerveau et Cognition, Unité Mixte de Recherche 5549, Faculté de Médecine Rangueil, 31062 Toulouse Cedex 9, France.
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Tallon-Baudry C, Bertrand O, Hénaff MA, Isnard J, Fischer C. Attention Modulates Gamma-band Oscillations Differently in the Human Lateral Occipital Cortex and Fusiform Gyrus. Cereb Cortex 2004; 15:654-62. [PMID: 15371290 DOI: 10.1093/cercor/bhh167] [Citation(s) in RCA: 268] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We studied the existence, localization and attentional modulation of gamma-band oscillatory activity (30-130 Hz) in the human intracranial region. Two areas known to play a key role in visual object processing: the lateral occipital (LO) cortex and the fusiform gyrus. These areas consistently displayed large gamma oscillations during visual stimulus encoding, while other extrastriate areas remained systematically silent, across 14 patients and 291 recording sites scattered throughout extrastriate visual cortex. The lateral extent of the responsive regions was small, in the range of 5 mm. Induced gamma oscillations and evoked potentials were not systematically co-localized. LO and the fusiform gyrus displayed markedly different patterns of attentional modulation. In the fusiform gyrus, attention enhanced stimulus-driven gamma oscillations. In LO, attention increased the baseline level of gamma oscillations during the expectation period preceding the stimulus. Subsequent gamma oscillations produced by attended stimuli were smaller than those produced by unattended, irrelevant stimuli. Attentional modulations of gamma oscillations in LO and the fusiform gyrus were thus very different, both in their time-course (preparatory period and/or stimulus processing) and direction of modulation (increase or decrease). Our results thus suggest that the functional role of gamma oscillations depends on the area in which they occur.
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Affiliation(s)
- Catherine Tallon-Baudry
- LENA CNRS UPR 640, Hôpital de la Pitié-Salpétrière, 47 Boulevard de l'Hôpital, 75013 Paris, France.
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15
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Fitzgibbon SP, Pope KJ, Mackenzie L, Clark CR, Willoughby JO. Cognitive tasks augment gamma EEG power. Clin Neurophysiol 2004; 115:1802-9. [PMID: 15261859 DOI: 10.1016/j.clinph.2004.03.009] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2004] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Gamma EEG oscillations are low amplitude rhythms in the 30-100 Hz range that correlate with cognitive task execution. They are usually reported using time-locked averaging of EEG during repetitive tasks. We tested the hypothesis that continuous gamma EEG would be measurable during mental tasks. METHODS We investigated sustained human gamma EEG oscillations induced by 8 cognitive tasks (Visual Checkerboard, Expectancy, Reading, Subtraction, Music, Expectancy, Word learning, Word recall, and a Video Segment) in 20 subjects using standard digital EEG recording and power spectral analysis. RESULTS All of the cognitive tasks augmented gamma power relative to a control condition (eyes open watching a blank computer screen). This enhancement was statistically significant at more than one scalp site for all tasks except checkerboard. The Expectancy, Learning, Reading and Subtraction tasks expressed the most impressive gamma response, up to 5 fold above the control condition and there was some task-related specificity of the distribution of increased gamma power, especially in posterior cortex with visual tasks. CONCLUSIONS Widespread gamma activation of cortical EEG can easily be demonstrated during mental activity. SIGNIFICANCE These results establish the feasibility of measuring high frequency EEG rhythms with trans-cranial recordings, demonstrate that sustained gamma EEG activity correlates with mentation, and provides evidence consistent with the temporal binding model.
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Affiliation(s)
- S P Fitzgibbon
- Centre for Neuroscience and Department of Medicine (Neurology), Flinders University, P.O. Box 2100, Adelaide, SA, Australia
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Abstract
Oscillatory synchrony could be used to establish dynamic links between the various cortical areas participating in the same cognitive process. Is it possible to detect oscillatory synchrony in humans, and is it relevant to behavior? There is now converging evidence for the existence of a transient oscillatory activity in the gamma range (30-60 Hz), obtained in response to static visual objects, and having only a loose temporal relationship to stimulus onset. This so-called "induced" gamma response is much larger in response to coherent static or moving objects. However, functional variations of gamma and/or beta (15-20 Hz) oscillations are not restricted to perceptive, bottom-up mechanisms, but are also observed during visual imagery or short-term memory maintenance. Oscillations at the scalp level thus seem to reflect large-scale neural cooperativity in a variety of task-dependent networks. Human intra-cranial recordings in a short-term memory paradigm further reveal the existence and the task-dependency of oscillatory synchrony in the beta range, between focal sites separated by several centimeters and with a few milliseconds time-lag. These findings thus confirm experimentally the hypothesis of a functional role of synchronized oscillatory activity in the coordination of distributed neural activity in humans, and support Hebb's concept of short-term memory maintenance by reentrant activity within the activated network. In addition, the intra-cranial data obtained in humans and monkeys also help to better understand the neural mechanisms generating scalp-recorded oscillations.
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17
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Herrmann CS, Lenz D, Junge S, Busch NA, Maess B. Memory-matches evoke human gamma-responses. BMC Neurosci 2004; 5:13. [PMID: 15084225 PMCID: PMC419345 DOI: 10.1186/1471-2202-5-13] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Accepted: 04/13/2004] [Indexed: 11/15/2022] Open
Abstract
Background Human brain activity in the gamma frequency range has been shown to be a correlate of numerous cognitive functions like attention, perception and memory access. More specifically, gamma activity has been found to be enhanced when stimuli are stored in or match with short-term memory (STM). We tested the hypothesis that gamma activity is also evoked when stimuli match representations in long-term-memory (LTM). EEG was recorded from 13 subjects performing a choice reaction task. Visual stimuli were either known real-world objects with a memory representation or novel configurations never seen before. Results All stimuli evoked an early gamma response which was maximal over occipital electrodes. This evoked gamma activity was significantly larger for items that matched memory templates. Conclusions Therefore, we argue that gamma activity results from the feedback from memory into perception systems. This assumption seems to be true for STM as well as LTM.
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Affiliation(s)
- Christoph S Herrmann
- Otto-von-Guericke University, Dept. of Biological Psychology P.O. Box 4120, 39016 Magdeburg, Germany
- Max-Planck-Institute of Cognitive Neuroscience P.O. Box 500 355, 04303 Leipzig, Germany
| | - Daniel Lenz
- Otto-von-Guericke University, Dept. of Biological Psychology P.O. Box 4120, 39016 Magdeburg, Germany
| | - Stefanie Junge
- Otto-von-Guericke University, Dept. of Biological Psychology P.O. Box 4120, 39016 Magdeburg, Germany
| | - Niko A Busch
- Otto-von-Guericke University, Dept. of Biological Psychology P.O. Box 4120, 39016 Magdeburg, Germany
- Max-Planck-Institute of Cognitive Neuroscience P.O. Box 500 355, 04303 Leipzig, Germany
| | - Burkhard Maess
- Max-Planck-Institute of Cognitive Neuroscience P.O. Box 500 355, 04303 Leipzig, Germany
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Shigemura J, Yoshino A, Kobayashi Y, Takahashi Y, Nomura S. Spatiotemporal differences between cognitive processes of spatially possible and impossible objects: a high-density electrical mapping study. BRAIN RESEARCH. COGNITIVE BRAIN RESEARCH 2004; 18:301-5. [PMID: 14741316 DOI: 10.1016/j.cogbrainres.2003.10.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Differences in cognitive processing between spatially possible and impossible figures were investigated using event-related potentials (ERPs). Two types of figures with identical luminance and equivalent spatial frequency were used as visual stimuli: possible three-dimensional figures (drawn with perspective and existing in the three-dimensional world) and impossible figures (drawn with perspective but not existing in the three-dimensional world). High-density electroencephalographic recording (72 channels) was performed for analysis of ERPs accompanying perception of each figure type; amplitude differences between the conditions were considered neurophysiologic correlates to perceptual differences between possible and impossible objects. Low-resolution brain electromagnetic tomography (LORETA) was used to identify the current source related to the differences. Compared with impossible three-dimensional figures, perception of possible figures showed a significant negative potential increase in the right inferior occipitotemporal region between 350 and 389 ms of latency. The current source was localized to the right fusiform gyrus. The results suggest that right fusiform gyrus is involved in discrimination between spatially possible and impossible objects.
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Affiliation(s)
- Jun Shigemura
- Department of Psychiatry, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan
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19
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Ojanen V, Revonsuo A, Sams M. Visual awareness of low-contrast stimuli is reflected in event-related brain potentials. Psychophysiology 2003; 40:192-7. [PMID: 12820860 DOI: 10.1111/1469-8986.00021] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Visual awareness was studied in 11 subjects by using coherent and scrambled objects as stimuli. The stimuli were presented near the subjective perceptual threshold. Explicitly recognized stimuli elicited a specific negative ERP deflection peaking at 460 ms. Our reaction time experiment suggests that this visual awareness negativity (VAN) is similar to that found previously at a shorter latency. We propose that VAN might reflect the exact moment of becoming aware of the task-relevant stimulus properties and provide an online marker of the temporal dynamics of visual awareness.
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Affiliation(s)
- Ville Ojanen
- Laboratory of Computational Engineering, Helsinki University of Technology, Helsinki, HUT, Finland.
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20
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Abstract
Here we summarize our present approach to the problem of consciousness. After an introduction outlining our general strategy, we describe what is meant by the term 'framework' and set it out under ten headings. This framework offers a coherent scheme for explaining the neural correlates of (visual) consciousness in terms of competing cellular assemblies. Most of the ideas we favor have been suggested before, but their combination is original. We also outline some general experimental approaches to the problem and, finally, acknowledge some relevant aspects of the brain that have been left out of the proposed framework.
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Affiliation(s)
- Francis Crick
- Francis Crick is at the Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, California 92037, USA
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21
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Lee KH, Williams LM, Breakspear M, Gordon E. Synchronous gamma activity: a review and contribution to an integrative neuroscience model of schizophrenia. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2003; 41:57-78. [PMID: 12505648 DOI: 10.1016/s0165-0173(02)00220-5] [Citation(s) in RCA: 368] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Synchronous high frequency (Gamma band) activity has been proposed as a candidate mechanism for the integration or 'binding' of distributed brain activities. Since the first descriptions of schizophrenia, attempts to characterize this disorder have focused on disturbances in such integrative processing. Here, we review both micro- and macroscopic neuroscience research into Gamma synchrony, and its application to understanding schizophrenia. The review encompasses evidence from both animal and human studies for the functional significance of Gamma activity, the association between Gamma dysfunction and information processing disturbances, and the relevance of specific Gamma dysfunctions to the integration and extension of previous disconnection models of schizophrenia. Attention is given to the relationship between Gamma activity and the heterogeneous symptoms of schizophrenia. Existing studies show that measures of Gamma activity have the potential to explain far more of the variance in schizophrenia performance than previous neurophysiological measures. It is concluded that measures of Gamma synchrony offer a valuable window into the core integrative disturbance in schizophrenia cognition.
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Affiliation(s)
- Kwang-Hyuk Lee
- Cognitive Neuroscience Unit, Department of Psychology, University of Sydney, and The Brain Dynamics Centre, Westmead Hospital, 2145, Sydney, NSW, Australia
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22
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Lutz A, Lachaux JP, Martinerie J, Varela FJ. Guiding the study of brain dynamics by using first-person data: synchrony patterns correlate with ongoing conscious states during a simple visual task. Proc Natl Acad Sci U S A 2002; 99:1586-91. [PMID: 11805299 PMCID: PMC122234 DOI: 10.1073/pnas.032658199] [Citation(s) in RCA: 180] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Even during well-calibrated cognitive tasks, successive brain responses to repeated identical stimulations are highly variable. The source of this variability is believed to reside mainly in fluctuations of the subject's cognitive "context" defined by his/her attentive state, spontaneous thought process, strategy to carry out the task, and so on... As these factors are hard to manipulate precisely, they are usually not controlled, and the variability is discarded by averaging techniques. We combined first-person data and the analysis of neural processes to reduce such noise. We presented the subjects with a three-dimensional illusion and recorded their electrical brain activity and their own report about their cognitive context. Trials were clustered according to these first-person data, and separate dynamical analyses were conducted for each cluster. We found that (i) characteristic patterns of endogenous synchrony appeared in frontal electrodes before stimulation. These patterns depended on the degree of preparation and the immediacy of perception as verbally reported. (ii) These patterns were stable for several recordings. (iii) Preparatory states modulate both the behavioral performance and the evoked and induced synchronous patterns that follow. (iv) These results indicated that first-person data can be used to detect and interpret neural processes.
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Affiliation(s)
- Antoine Lutz
- Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale (LENA), Hôpital de La Salpêtrière, Centre National de la Recherche Scientifique, UPR 640, 75651 Paris Cedex 13, France.
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23
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Sannita WG, Bandini F, Beelke M, De Carli F, Carozzo S, Gesino D, Mazzella L, Ogliastro C, Narici L. Time dynamics of stimulus- and event-related gamma band activity: contrast-VEPs and the visual P300 in man. Clin Neurophysiol 2001; 112:2241-9. [PMID: 11738194 DOI: 10.1016/s1388-2457(01)00700-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVES To investigate the time dynamics and phase relationship with the stimulus of the onset/offset visual evoked potentials (VEPs), P300 and gamma band oscillatory responses to visual (contrast) stimulation. Gamma band oscillatory activity mediates in sensory and cognitive operations, with a role in stimulus-related cortical synchronization, but is reportedly reduced in the time window of the P300 response. METHODS Ten healthy volunteers were studied. VEPs and P300 were obtained in a stimulus condition combining standard contrast stimulation and a visual odd-ball paradigm. Visual stimuli were gratings with a sinusoidal luminance profile (9.0 degrees central retina; 1.3 cycles/degree; 70% contrast) that were presented monocularly in onset/offset mode, with vertical orientation (frequent stimulus; 80%) or with a 15 degrees rotation to the right (infrequent, target stimulus). The total signal activity (temporal spectral evolution), the activity phase-locked to the stimulus onset (rectified integrated average), and the 'locking index' (ratio of the activity phase-locked to the stimulus to the total signal activity) were computed over time and across frequencies on the signals recorded at occipital (visual responses) and central locations (P300). RESULTS Oscillatory activity centered around approximately 20.0-35.0 Hz and phase-locked to the stimulus was recorded at occipital locations with time dynamics anticipating the conventional VEPs. Phase-locking was higher after frequent than in response to target stimuli and after the stimulus offset compared to onset, while the phase-locking of the VEP frequency components was higher after the stimulus onset. The low frequency components of the P300 recorded at Cz (below approximately 8.0-10.0 Hz) were almost totally phase-locked to the stimulus, while the gamma band activity at the P300 location did not vary over time in amplitude or phase-locking and was mostly non-locked to the target stimulus. CONCLUSIONS These observations add to the evidence of a role of the gamma band oscillatory responses (centered at approximately 20.0-35.0 Hz) in visual information processing and suggest that the increment in gamma band activity during cognitive operations also depends on task characteristics, vigilance or selective attention, and brain functional state. The visual P300 appears to reflect low frequency synchronization mechanisms.
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Affiliation(s)
- W G Sannita
- Neurophysiopathology, Department of Motor Science and Rehabilitation, University of Genoa, Genoa, Italy.
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24
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Shahani U, Lang G, Mansfield DC, Halliday DM, Weir AI, Maas P, Donaldson GB. Magnetoencephalography and stereopsis: rhythmic cortical activity in humans recorded over the parieto-occipital cortex. Neurosci Lett 2001; 315:154-8. [PMID: 11716986 DOI: 10.1016/s0304-3940(01)02319-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied human stereopsis by analysing magnetoencephalographic signals during the presentation of stereograms using frequency analysis. The study of synchronised firing of cortical neurones is a new way of understanding information processing in the brain and it is hypothesised that frequencies greater than 35 Hz are used for higher-order processing. We report the response of cortical neurones involved in stereopsis recorded from over the occipital and parietal cortices using a single channel axial superconducting quantum interference device neuromagnetometer. Our main result was increased cortical activity in the gamma-band at frequencies apparently related to stereopsis and the perception of depth. Our results are consistent with reports in the literature that suggest that frequencies above 40 Hz are involved in attention, pattern recognition and higher order visual activity.
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Affiliation(s)
- U Shahani
- Department of Vision Sciences, Glasgow Caledonian University, City Campus, Cowcaddens Road, Glasgow G4 0BA, Scotland, UK.
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25
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Freiwald WA, Kreiter AK, Singer W. Synchronization and assembly formation in the visual cortex. PROGRESS IN BRAIN RESEARCH 2001; 130:111-40. [PMID: 11480271 DOI: 10.1016/s0079-6123(01)30009-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- W A Freiwald
- Institute for Brain Research, University of Bremen, FB2, P.O. Box 330440, D-28334 Bremen, Germany.
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26
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Keil A, Gruber T, Müller MM. Functional correlates of macroscopic high-frequency brain activity in the human visual system. Neurosci Biobehav Rev 2001; 25:527-34. [PMID: 11595272 DOI: 10.1016/s0149-7634(01)00031-8] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The present article reviews empirical findings of large-scale gamma oscillations in the human brain, in the context of their functional correlates. Evidence supporting the fact that high-frequency neuronal oscillations are involved in several aspects of visual processing is presented, with a focus on bottom-up and top-down visual feature processing, selective attention, and emotional evaluation. This evidence suggests that visual processing involves the integrated activity of wide spread neuronal assemblies that can be studied with respect to time course and topography, employing frequency-domain analyses. Possible mechanisms underlying these phenomena are considered. Furthermore, the effects of attention and motivation, as well as characteristics of experimental paradigms are discussed as determinants of reliability and validity of measures of high-frequency oscillations.
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Affiliation(s)
- A Keil
- Department of Psychology, University of Konstanz, Box D25, D-78434 Konstanz, Germany.
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27
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Crone NE, Boatman D, Gordon B, Hao L. Induced electrocorticographic gamma activity during auditory perception. Brazier Award-winning article, 2001. Clin Neurophysiol 2001; 112:565-82. [PMID: 11275528 DOI: 10.1016/s1388-2457(00)00545-9] [Citation(s) in RCA: 374] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE To define the spatial, temporal, and functional characteristics of induced gamma (>30 Hz) activity during functional activation of the left superior temporal gyrus. METHODS Electrocorticographic (ECoG) recordings were made in 4 clinical subjects during auditory tone and phoneme discrimination tasks, and event-related changes in the ECoG band power were calculated. The topography and temporal sequence of event-related power changes in different gamma bands were contrasted with those of auditory evoked potentials (AEPs), and with those of event-related power changes in the alpha band (8-12 Hz). RESULTS Auditory stimuli induced a broadband power augmentation that included 40 Hz, as well as higher (80-100 Hz) gamma frequencies. The topography of gamma augmentation was similar, but not identical, to that of the AEP, and was more focused than that of alpha power suppression. Its temporal onset coincided with the N100, but outlasted it. Phonemes produced greater gamma augmentation than tones, while a similar difference was not observed in the N100. CONCLUSIONS Auditory perception induces ECoG gamma activity not only at 40 Hz, but also in higher gamma frequencies. This activity appears to be an index of cortical activation that reflects task-specific processing in the human auditory cortex more closely than the AEP or alpha power suppression.
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Affiliation(s)
- N E Crone
- Department of Neurology, The Johns Hopkins University School Of Medicine, N. Wolfe St., Meyer Building, Baltimore, MD 21287-7247, USA.
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28
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Knief A, Schulte M, Bertran O, Pantev C. The perception of coherent and non-coherent auditory objects: a signature in gamma frequency band. Hear Res 2000; 145:161-8. [PMID: 10867289 DOI: 10.1016/s0378-5955(00)00091-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pertinence of gamma band activity in magnetoencephalographic and electroencephalographic recordings for the performance of a gestalt recognition process is a question at issue. We investigated the functional relevance of gamma band activity for the perception of auditory objects. An auditory experiment was performed as an analog to the Kanizsa experiment in the visual modality, comprising four different coherent and non-coherent stimuli. For the first time functional differences of evoked gamma band activity due to the perception of these stimuli were demonstrated by various methods (localization of sources, wavelet analysis and independent component analysis, ICA). Responses to coherent stimuli were found to have more features in common compared to non-coherent stimuli (e.g. closer located sources and smaller number of ICA components). The results point to the existence of a pitch processor in the auditory pathway.
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Affiliation(s)
- A Knief
- Biomagnetism Center, Institute for Experimental Audiology, University of Münster, Münster, Germany
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29
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Sannita WG. Stimulus-specific oscillatory responses of the brain: a time/frequency-related coding process. Clin Neurophysiol 2000; 111:565-83. [PMID: 10727907 DOI: 10.1016/s1388-2457(99)00271-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
OBJECTIVES To review the coherent, rhythmic oscillations above approximately 20 Hz that occur in response to sensory inputs in the firing rate and membrane or local field potentials of distributed neuron aggregates of CNS layered structures. RESULTS Oscillatory activity at approximately 20-80 Hz occurs in response to either olfactory, auditory and visual (contrast) stimuli; oscillations at frequencies centered on 100-120 Hz or 600 Hz are recorded, respectively, from the visual system (luminance stimulation) and from the somatosensory cortex. Experimental evidence suggests sources/mechanisms of generation that depend on inhibitory interneurons and pyramidal cells and are partially independent from those of conventional (broadband) evoked responses. In the olfactory and visual systems, the oscillatory responses reflect the global stimulus properties. A time/phase correlation between firing rate, spiking coincidence and oscillatory field responses has been documented. The oscillatory responses are postsynaptic both in cortex and in precortical structures (e.g. retina; LGN). Evidence indicates intracortical and thalamocortical interacting mechanisms of regulation as well as GABAergic and cholinergic modulation. In the visual cortex the oscillatory responses are driven by oscillations in the synaptic input. Oscillatory potentials are dependent on resonance phenomena and produce narrow-band synchronization of activated neurons. They may have a role in the 'binding' of separate neuronal aggregates into sensory units. CONCLUSIONS Oscillatory responses contribute as a time/frequency coding mechanism to pacing neurons selectively for the physical properties of stimulus and are involved in sensory information processing.
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Affiliation(s)
- W G Sannita
- Center for Neuroactive Drugs, DISMR University, 16132, Genova, Italy.
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Sauvé K. Gamma-band synchronous oscillations: recent evidence regarding their functional significance. Conscious Cogn 1999; 8:213-24. [PMID: 10448003 DOI: 10.1006/ccog.1999.0383] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
How do our brains represent distinct objects in consciousness? In order to consciously distinguish between objects, our brains somehow selectively bind together activity patterns of spatially intermingled neurons that simultaneously represent similar and dissimilar features of distinct objects. Gamma-band synchronous oscillations (GSO) of neuroelectrical activity have been hypothesized to be a mechanism used by our brains to generate and bind conscious sensations to represent distinct objects. Most experiments relating GSO to specific features of consciousness have been published only in the last several years. This brief review focuses on a wide variety experiments in which animals, including humans, discriminate between sensory stimuli and make these discriminations evident in their behavior. Performance of these tasks, in humans, is invariably accompanied by conscious awareness of both stimuli and behavior. Results of these experiments indicate that specific patterns of GSO correlate closely with specific aspects of conscious sensorimotor processing. That is, GSO appear to be closely correlated with neural generation of our most paradigmatic cognitive state: consciousness.
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Affiliation(s)
- K Sauvé
- Department of Physiology and Neuroscience, New York University School of Medicine, 550 First Avenue, New York, New York, 10016, USA.
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31
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Engel AK, Fries P, König P, Brecht M, Singer W. Does time help to understand consciousness? Conscious Cogn 1999; 8:260-8. [PMID: 10448005 DOI: 10.1006/ccog.1999.0400] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- A K Engel
- Max-Planck-Institut für Hirnforschung, Deutschordenstrasse 46, Frankfurt, 60528, Germany.
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Abstract
The binding problem is frequently discussed in consciousness research. However, it is by no means clear what the problem is supposed to be and how exactly it relates to consciousness. In the present paper the nature of the binding problem is clarified by distinguishing between different formulations of the problem. Some of them make no mention of consciousness, whereas others are directly related to aspects of phenomenal experience. Certain formulations of the binding problem are closely connected to the classical philosophical problem of the unity of consciousness and the currently fashionable search for the neural correlates of consciousness. Nonetheless, only a part of the current empirical research on binding is directly relevant to the study of consciousness. The main message of the present paper is that the science of consciousness needs to establish a clear theoretical view of the relation between binding and consciousness and to encourage further empirical work that builds on such a theoretical foundation.
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Affiliation(s)
- A Revonsuo
- Department of Philosophy, University of Turku, Turku, FIN-20014, Finland.
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