Gamma oscillations organize top-down signalling to hypothalamus and enable food seeking

Nature ◽  
2017 ◽  
Vol 542 (7640) ◽  
pp. 232-236 ◽  
Author(s):  
Marta Carus-Cadavieco ◽  
Maria Gorbati ◽  
Li Ye ◽  
Franziska Bender ◽  
Suzanne van der Veldt ◽  
...  
Keyword(s):  
Gamma Oscillations ◽  
Top Down ◽  
Food Seeking

scholarly journals Top-down Control of Inhibition Reshapes Neural Dynamics Giving Rise to a Diversity of Computations

2020 ◽  
Author(s):  
Zhen Chen ◽  
Krishnan Padmanabhan
Keyword(s):  
Network Dynamics ◽  
Gamma Oscillations ◽  
Sensory Systems ◽  
Pattern Separation ◽  
Inhibitory Neurons ◽  
Top Down ◽  
Brain Areas ◽  
Excitatory Neurons ◽  
Local Circuits

AbstractGrowing evidence shows that top-down projections from excitatory neurons in higher brain areas selectively synapse onto local inhibitory interneurons in sensory systems. While this connectivity is conserved across sensory modalities, the role of this feedback in shaping the dynamics of local circuits, and the resultant computational benefits it provides remains poorly understood. Using rate models of neuronal firing in a network consisting of excitatory, inhibitory and top-down populations, we found that changes in the weight of feedback to inhibitory neurons generated diverse network dynamics and complex transitions between these dynamics. Additionally, modulation of the weight of top-down feedback supported a number of computations, including both pattern separation and oscillatory synchrony. A bifurcation analysis of the network identified a new mechanism by which gamma oscillations could be generated in a model of neural circuits, which we termed Top-down control of Inhibitory Neuron Gamma (TING). We identified the unique roles that top-down feedback of inhibition plays in shaping network dynamics and computation, and the ways in which these dynamics can be deployed to process sensory inputs.Significance StatementThe functional role of feedback projections, connecting excitatory neurons in higher brain areas to inhibitory neurons in primary sensory regions, remains a fundamental open question in neuroscience. Growing evidence suggests that this architecture is recapitulated across a diverse array of sensory systems, ranging from vision to olfaction. Using a rate model of top-down feedback onto inhibition, we found that changes in the weight of feedback support both pattern separation and oscillatory synchrony, including a mechanism by which top-down inputs could entrain gamma oscillations within local networks. These dual functions were accomplished via a codimension-2 bifurcation in the dynamical system. Our results highlight a key role for this top-down feedback, gating inhibition to facilitate often diametrically different local computations.

scholarly journals Synchronous spiking associated with high gamma oscillations in prefrontal cortex exerts top-down control over a 5Hz-rhythmic modulation of spiking in locus coeruleus

2020 ◽  
Author(s):  
Nelson K. Totah ◽  
Nikos K. Logothetis ◽  
Oxana Eschenko
Keyword(s):  
Prefrontal Cortex ◽  
Locus Coeruleus ◽  
Field Potential ◽  
Gamma Oscillations ◽  
Neuronal Population ◽  
Excitatory Input ◽  
Top Down ◽  
Population Activity ◽  
Oscillation Analysis ◽  
High Gamma

AbstractThe brainstem noradrenergic locus coeruleus (LC) is reciprocally connected with the prefrontal cortex (PFC). Strong coupling between LC spiking and depolarizing phase of slow (1 – 2 Hz) waves in the PFC field potentials during sleep and anesthesia suggests that the LC drives cortical state transition. Reciprocal LC-PFC connectivity should also allow interactions in the opposing (top-down) direction, but prior work has only studied prefrontal control over LC activity using direct electrical (or optogenetic) stimulation paradigms. Here, we describe the physiological characteristics of naturally occurring top-down prefrontal-coerulear interactions. Specifically, we recorded LC multi-unit activity (MUA) simultaneously with PFC single unit and local field potential (LFP) activity in urethane-anesthetized rats. We observed cross-regional coupling between the phase of ~5 Hz oscillations in LC population spike rate and the power of PFC LFP oscillations within the high Gamma (hGamma) range (60 – 200 Hz). Specifically, transient increases in PFC hGamma power preceded peaks in the ~5 Hz LC-MUA oscillation. Analysis of cross-regional transfer entropy demonstrated that the PFC hGamma transients were predictive of a transient increase in LC-MUA. A ~29 msec delay between these signals was consistent with the conduction velocity from the PFC to the LC. Finally, we showed that PFC hGamma transients are associated with synchronized spiking of a subset (27%) of PFC single units. Our data suggest that, PFC hGamma transients may indicate the timing of the top-down excitatory input to LC, at least under conditions when LC neuronal population activity fluctuates rhythmically at ~5 Hz. Synchronized PFC neuronal spiking that occurs during hGamma transients may provide a previously unknown mode of top-down control over the LC.

scholarly journals Noninvasively Decoding the Contents of Visual Working Memory in the Human Prefrontal Cortex within High-gamma Oscillatory Patterns

2012 ◽  
Vol 24 (2) ◽  
pp. 304-314 ◽  
Author(s):  
Rafael Polanía ◽  
Walter Paulus ◽  
Michael A. Nitsche
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Animal Studies ◽  
Gamma Oscillations ◽  
Specific Information ◽  
Top Down ◽  
Population Activity ◽  
High Gamma ◽  
Long Time ◽  
Eeg Recordings

The temporal maintenance and subsequent retrieval of information that no longer exists in the environment is called working memory. It is believed that this type of memory is controlled by the persistent activity of neuronal populations, including the prefrontal, temporal, and parietal cortex. For a long time, it has been controversially discussed whether, in working memory, the PFC stores past sensory events or, instead, its activation is an extramnemonic source of top–down control over posterior regions. Recent animal studies suggest that specific information about the contents of working memory can be decoded from population activity in prefrontal areas. However, it has not been shown whether the contents of working memory during the delay periods can be decoded from EEG recordings in the human brain. We show that by analyzing the nonlinear dynamics of EEG oscillatory patterns it is possible to noninvasively decode with high accuracy, during encoding and maintenance periods, the contents of visual working memory information within high-gamma oscillations in the human PFC. These results are thus in favor of an active storage function of the human PFC in working memory; this, without ruling out the role of PFC in top–down processes. The ability to noninvasively decode the contents of working memory is promising in applications such as brain computer interfaces, together with computation of value function during planning and decision making processes.

scholarly journals COSMO-Onset: A Neurally-Inspired Computational Model of Spoken Word Recognition, Combining Top-Down Prediction and Bottom-Up Detection of Syllabic Onsets

2021 ◽  
Vol 15 ◽  
Author(s):  
Mamady Nabé ◽  
Jean-Luc Schwartz ◽  
Julien Diard
Keyword(s):  
Word Recognition ◽  
Computational Models ◽  
Spoken Word Recognition ◽  
Gamma Oscillations ◽  
Spoken Word ◽  
Theta Oscillations ◽  
Onset Detection ◽  
Top Down ◽  
Bottom Up ◽  
Oscillatory Processes

Recent neurocognitive models commonly consider speech perception as a hierarchy of processes, each corresponding to specific temporal scales of collective oscillatory processes in the cortex: 30–80 Hz gamma oscillations in charge of phonetic analysis, 4–9 Hz theta oscillations in charge of syllabic segmentation, 1–2 Hz delta oscillations processing prosodic/syntactic units and the 15–20 Hz beta channel possibly involved in top-down predictions. Several recent neuro-computational models thus feature theta oscillations, driven by the speech acoustic envelope, to achieve syllabic parsing before lexical access. However, it is unlikely that such syllabic parsing, performed in a purely bottom-up manner from envelope variations, would be totally efficient in all situations, especially in adverse sensory conditions. We present a new probabilistic model of spoken word recognition, called COSMO-Onset, in which syllabic parsing relies on fusion between top-down, lexical prediction of onset events and bottom-up onset detection from the acoustic envelope. We report preliminary simulations, analyzing how the model performs syllabic parsing and phone, syllable and word recognition. We show that, while purely bottom-up onset detection is sufficient for word recognition in nominal conditions, top-down prediction of syllabic onset events allows overcoming challenging adverse conditions, such as when the acoustic envelope is degraded, leading either to spurious or missing onset events in the sensory signal. This provides a proposal for a possible computational functional role of top-down, predictive processes during speech recognition, consistent with recent models of neuronal oscillatory processes.

Top-Down Processing and Visual Reorientation Illusions in a Virtual Reality Environment

2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman
Keyword(s):  
Virtual Reality ◽  
Visual Processing ◽  
Line Length ◽  
Perceptual Cues ◽  
Virtual Reality Environment ◽  
Top Down ◽  
Test Conditions ◽  
The Subject ◽  
Processing Mechanisms

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.

Functional Anatomy of Intensity Aspects of Attention

2003 ◽  
Vol 14 (3) ◽  
pp. 181-190 ◽  
Author(s):  
Walter Sturm
Keyword(s):  
Right Hemisphere ◽  
Functional Anatomy ◽  
Fmri Data ◽  
Functional Networks ◽  
Top Down ◽  
Stimulus Modality ◽  
Spatial Orienting ◽  
Phasic Alertness ◽  
Co Activation ◽  
Attention System

Abstract: Behavioral and PET/fMRI-data are presented to delineate the functional networks subserving alertness, sustained attention, and vigilance as different aspects of attention intensity. The data suggest that a mostly right-hemisphere frontal, parietal, thalamic, and brainstem network plays an important role in the regulation of attention intensity, irrespective of stimulus modality. Under conditions of phasic alertness there is less right frontal activation reflecting a diminished need for top-down regulation with phasic extrinsic stimulation. Furthermore, a high overlap between the functional networks for alerting and spatial orienting of attention is demonstrated. These findings support the hypothesis of a co-activation of the posterior attention system involved in spatial orienting by the anterior alerting network. Possible implications of these findings for the therapy of neglect are proposed.

Auswirkungen eines Aufmerksamkeitstrainings auf die aphasische Symptomatik bei Schlaganfallpatienten

2011 ◽  
Vol 22 (1) ◽  
pp. 21-32 ◽  
Author(s):  
Julia Graf ◽  
Hartwig Kulke ◽  
Christa Sous-Kulke ◽  
Wilfried Schupp ◽  
Stefan Lautenbacher
Keyword(s):  
Top Down

Aufmerksamkeit kann als Kontrollsystem neuronaler Aktivität verstanden werden, welches Neuroplastizität top-down modulieren hilft. Bisher wurde selten versucht, durch deren gezielte Förderung Funktionswiederherstellungen nach Hirnschädigung zu begünstigen. In vorliegender Studie wurde dies am Beispiel der Aphasie erprobt. 15 Schlaganfallpatienten erhielten ein dreiwöchiges Training der selektiven Aufmerksamkeit mit den PC-Programmen CogniPlus und „Konzentration“ bei fünf Sitzungen pro Woche zusätzlich zur Standardtherapie, 13 weitere bildeten eine Kontrollgruppe ohne Aufmerksamkeitstraining. Zur Effektivitätskontrolle dienten zwei Versionen des Untertests Go/Nogo (Testbatterie zur Aufmerksamkeitsprüfung) und die Kurze Aphasieprüfung. Nach dem Training manifestierte sich zwischen den Untersuchungsgruppen kein Unterschied in Aufmerksamkeits- und Sprachfunktionen; das zusätzliche Aufmerksamkeitstraining war also wirkungslos. Allerdings zeigten Patienten mit deutlichen Aufmerksamkeitsverbesserungen tendenziell weniger Aphasie-Symptome, was die Hypothese aufmerksamkeitsvermittelter Plastizitätsmodulation nach Hirnschädigung partiell stützt.

Aufmerksamkeitswechsel und Konzentration: Von den Funktionen zum Mechanismus

2001 ◽  
Vol 209 (1) ◽  
pp. 34-53 ◽  
Author(s):  
Rainer Bösel
Keyword(s):  
Top Down ◽  
Eeg Alpha

Zusammenfassung. Aufmerksamkeit wird sowohl als Selektivität in der bewußter Verarbeitung oder auch als selektive neuronale Aktivierung verstanden. Die neuronalen Strukturen, die Objektdiskrimination ermöglichen, erlauben eine Interaktion von datengetriebenen und endogenen top-down Prozessen, die zu einer selektiven Bereitstellung von Verarbeitungs-Ressourcen führen. Zielgerichtetes Verhalten erfordert manchmal einen Wechsel in der Ressourcen-Bereitstellung und eine Konzentration von mentaler Aktivität. Aufmerksamkeitswechsel kann als ein zweiphasiger Prozeß verstanden werden, der aus einer breiten Mobilisierung von Gedächtnis-Ressourcen besteht (angezeigt durch EEG-Theta), gefolgt von einer re-organisierenden Einengung neuronaler Aktivität (angezeigt durch langsames EEG-Alpha). Dieser Beitrag unterstützt die Annahme, daß die Analyse des gekoppelten Wechselspiels aus Mobilisierung und Konzentration in bestimmten Teilen der posterioren und anterioren Rindenregionen ein Schlüssel für das Verständnis von Aufmerksamkeitswechsel sein könnte.

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