Bridging the gap: a model of common neural mechanisms underlying the Fröhlich effect, the flash-lag effect, and the representational momentum effect

In recent years, the study and interpretation of mislocalization phenomena observed with moving objects have caused an intense debate about the processing mechanisms underlying the encoding of position. We use a neurophysiologically plausible recurrent network model to explain visual illusions that occur at the start, midposition, and end of motion trajectories known as the Fröhlich, the flash-lag, and the representational momentum effect, respectively. The model implements the idea that trajectories are internally represented by a traveling activity wave in position space, which is essentially shaped by local feedback loops within pools of neurons. We first use experimentally observed trajectory representations in the primary visual cortex of cat to adjust the spatial ranges of lateral interactions in the model.We then show that the readout of the activity profile at adequate points in time during the build-up, midphase, and decay of the wave qualitatively and quantitatively explain the known dependence of the mislocalization errors on stimulus attributes such as contrast and speed. We conclude that cooperative mechanisms within the network may be responsible for the three illusions, with a possible intervention of top-down influences that modulate the efficacy of the lateral interactions.Deutscher Akademischer Austauschdienst (DAAD) / Conselho de Reitores das Universidades Portuguesas (CRUP) - As Acções Integradas Luso - AlemãsBundesministerium für Bildung und Forschungthe (BMBF

A Dynamic Neural Field Model of Mesoscopic Cortical Activity Captured with Voltage-Sensitive Dye Imaging

A neural field model is presented that captures the essential non-linear characteristics of activity dynamics across several millimeters of visual cortex in response to local flashed and moving stimuli. We account for physiological data obtained by voltage-sensitive dye (VSD) imaging which reports mesoscopic population activity at high spatio-temporal resolution. Stimulation included a single flashed square, a single flashed bar, the line-motion paradigm – for which psychophysical studies showed that flashing a square briefly before a bar produces sensation of illusory motion within the bar – and moving squares controls. We consider a two-layer neural field (NF) model describing an excitatory and an inhibitory layer of neurons as a coupled system of non-linear integro-differential equations. Under the assumption that the aggregated activity of both layers is reflected by VSD imaging, our phenomenological model quantitatively accounts for the observed spatio-temporal activity patterns. Moreover, the model generalizes to novel similar stimuli as it matches activity evoked by moving squares of different speeds. Our results indicate that feedback from higher brain areas is not required to produce motion patterns in the case of the illusory line-motion paradigm. Physiological interpretation of the model suggests that a considerable fraction of the VSD signal may be due to inhibitory activity, supporting the notion that balanced intra-layer cortical interactions between inhibitory and excitatory populations play a major role in shaping dynamic stimulus representations in the early visual cortex

Nasal Chemosensory-Stimulation Evoked Activity Patterns in the Rat Trigeminal Ganglion Visualized by In Vivo Voltage-Sensitive Dye Imaging

Mammalian nasal chemosensation is predominantly mediated by two independent neuronal pathways, the olfactory and the trigeminal system. Within the early olfactory system, spatiotemporal responses of the olfactory bulb to various odorants have been mapped in great detail. In contrast, far less is known about the representation of volatile chemical stimuli at an early stage in the trigeminal system, the trigeminal ganglion (TG), which contains neurons directly projecting to the nasal cavity. We have established an in vivo preparation that allows high-resolution imaging of neuronal population activity from a large region of the rat TG using voltage-sensitive dyes (VSDs). Application of different chemical stimuli to the nasal cavity elicited distinct, stimulus-category specific, spatiotemporal activation patterns that comprised activated as well as suppressed areas. Thus, our results provide the first direct insights into the spatial representation of nasal chemosensory information within the trigeminal ganglion imaged at high temporal resolution

The role of action plans and other cognitive factors in motion extrapolation : a modelling study

When observers are asked to remember the final location of an object undergoing apparent or implied motion, a forward displacement is observed. The magnitude of this form of motion extrapolation is known to depend on various factors including stimulus attributes, action plans and other cognitive cues. Here we present a modelling approach which aims at bridging different existing theories of displacement within a single theoretical framework. A network model consisting of interacting excitatory and inhibitory cell populations coding for stimulus attributes like position or orientation is used to study the response to motion displays. The intrinsic network dynamics can be modulated by additional information sources representing action plans directed at the moving target or cognitive cues such as prior knowledge about the trajectory. These factors decide the extent to which the dynamic representation overshoots the final position. The model predictions are quantitatively compared with the experimental findings. The results are discussed in relation to theoretical ideas about processing principles underlying motion extrapolation and a comparison with neurophysiological findings linked to movement prediction is made.ArteSimit - IST-2000-29689

Cortical response field dynamics in cat visual cortex

Little is known about the ‘‘inverse’ ’ of the receptive field—the region of cortical space whose spatiotemporal pattern of electrical activity is influenced by a given sensory stimulus. We refer to this activated area as the cortical response field, the properties of which remain unexplored. Here, the dynamics of cortical response fields evoked in visual cortex by small, local drifting-oriented gratings were explored using voltage-sensitive dyes. We found that the cortical response field was often characterized by a plateau of activity, beyond the rim of which activity diminished quickly. Plateau rim location was largely independent of stimulus orientation. However, approximately 20 ms following plateau onset, 1--3 peaks emerged on it and were amplified for 25 ms. Spiking was limited to the peak zones, whose location strongly depended on stimulus orientation. Thus, alongside selective amplification of a spatially restricted suprathreshold response, wider activation to just below threshold encompasses all orientation domains within a well-defined retinotopic vicinity of the current stimulus, priming the cortex for processing of subsequent stimuli

Bridging the gap between single receptor type activity and whole-brain dynamics

Data de publicació electrònica: 02-04-2021What is the effect of activating a single modulatory neuronal receptor type on entire brain network dynamics? Can such effect be isolated at all? These are important questions because characterizing elementary neuronal processes that influence network activity across the given anatomical backbone is fundamental to guide theories of brain function. Here, we introduce the concept of the cortical ‘receptome’ taking into account the distribution and densities of expression of different modulatory receptor types across the brain's anatomical connectivity matrix. By modelling whole‐brain dynamics in silico, we suggest a bidirectional coupling between modulatory neurotransmission and neuronal connectivity hardware exemplified by the impact of single serotonergic (5‐HT) receptor types on cortical dynamics. As experimental support of this concept, we show how optogenetic tools enable specific activation of a single 5‐HT receptor type across the cortex as well as in vivo measurement of its distinct effects on cortical processing. Altogether, we demonstrate how the structural neuronal connectivity backbone and its modulation by a single neurotransmitter system allow access to a rich repertoire of different brain states that are fundamental for flexible behaviour. We further propose that irregular receptor expression patterns—genetically predisposed or acquired during a lifetime—may predispose for neuropsychiatric disorders like addiction, depression and anxiety along with distinct changes in brain state. Our long‐term vision is that such diseases could be treated through rationally targeted therapeutic interventions of high specificity to eventually recover natural transitions of brain states.Deutsche Forschungsgemeinschaft (DFG): Dirk Jancke, JA 945/5‐1; JA 945/4‐1; Deutsche Forschungsgemeinschaft (DFG): Stefan Herlitze, HE 2471/12‐1; 2471/18‐1; Deutsche Forschungsgemeinschaft (DFG): Stefan Herlitze, Dirk Jancke, Project ID 122679504 ‐ SFB 874, (project part A2, DJ and project part B10, SH); Deutsche Forschungsgemeinschaft (DFG): Dirk Jancke, JA 945/3‐1 and Hamutal Slovin SL 185/1‐1, German‐Israeli Project Cooperation (DIP); Deutsche Forschungsgemeinschaft (DFG): Melanie D Mark, MA 5806/1‐2; MA 5806/2‐1; Deutsche Forschungsgemeinschaft (DFG): Stefan Herlitze, SFB 1280, DFG project no. 316803389; GD is supported by a Spanish national research project (ref. PID2019‐105772GB‐I00 MCIU AEI) funded by the Spanish Ministry of Science, Innovation and Universities (MCIU), State Research Agency (AEI); HBP SGA3 Human Brain Project Specific Grant Agreement 3 (grant agreement no. 945539), funded by the EU H2020 FET Flagship programme; SGR Research Support Group support (ref. 2017 SGR 1545), funded by the Catalan Agency for Management of University and Research Grants (AGAUR); Neurotwin Digital twins for model‐driven noninvasive electrical brain stimulation (grant agreement ID: 101017716) funded by the EU H2020 FET Proactive programme; euSNN European School of Network Neuroscience (grant agreement ID: 860563) funded by the EU H2020 MSCA‐ITN Innovative Training Networks; CECH The Emerging Human Brain Cluster (ID: 001‐P‐001682) within the framework of the European Research Development Fund Operational Program of Catalonia 2014‐2020; Brain‐Connects: Brain Connectivity during Stroke Recovery and Rehabilitation (ID: 201725.33) funded by the Fundacio La Marato TV3; Corticity, FLAG–ERA JTC 2017, (ref. PCI2018‐092891) funded by the Spanish Ministry of Science, Innovation and Universities (MCIU), State Research Agency (AEI). The funders had no role in study design, decision to publish, or preparation of the manuscript