Cognitive and Perceptual Functions of the Visual Thalamus

The thalamus is classically viewed as passively relaying information to the cortex. However, there is growing evidence that the thalamus actively regulates information transmission to the cortex and between cortical areas using a variety of mechanisms, including the modulation of response magnitude, firing mode, and synchrony of neurons according to behavioral demands. We discuss how the visual thalamus contributes to attention, awareness, and visually guided actions, to present a general role for the thalamus in perception and cognition

Communication between Brain Areas Based on Nested Oscillations

Contains fulltext : 168625.pdf (publisher's version ) (Open Access)14 p

Transcranial magnetic stimulation studies of visuospatial attentional control

Transcranial magnetic stimulation (TMS) is an established technique in cognitive neuroscience which is used to interrupt processing in the brain, creating a brief ‘virtual lesion’. Here, we review recent studies that have employed TMS to gain insight into the roles of frontal and parietal cortex in visuospatial attention control

How to Create and Use Binocular Rivalry

Each of our eyes normally sees a slightly different image of the world around us. The brain can combine these two images into a single coherent representation. However, when the eyes are presented with images that are sufficiently different from each other, an interesting thing happens: Rather than fusing the two images into a combined conscious percept, what transpires is a pattern of perceptual alternations where one image dominates awareness while the other is suppressed; dominance alternates between the two images, typically every few seconds. This perceptual phenomenon is known as binocular rivalry. Binocular rivalry is considered useful for studying perceptual selection and awareness in both human and animal models, because unchanging visual input to each eye leads to alternations in visual awareness and perception. To create a binocular rivalry stimulus, all that is necessary is to present each eye with a different image at the same perceived location. There are several ways of doing this, but newcomers to the field are often unsure which method would best suit their specific needs. The purpose of this article is to describe a number of inexpensive and straightforward ways to create and use binocular rivalry. We detail methods that do not require expensive specialized equipment and describe each method's advantages and disadvantages. The methods described include the use of red-blue goggles, mirror stereoscopes and prism goggles

Mechanisms of visual attention in the human cortex.

Abstract A typical scene contains many different objects that, because of the limited processing capacity of the visual system, compete for neural representation. The competition among multiple objects in visual cortex can be biased by both bottom-up sensory-driven mechanisms and top-down influences, such as selective attention. Functional brain imaging studies reveal that, both in the absence and in the presence of visual stimulation, biasing signals due to selective attention can modulate neural activity in visual cortex in several ways. Although the competition among stimuli for representation is ultimately resolved within visual cortex, the source of top-down biasing signals derives from a network of areas in frontal and parietal cortex

FEF-controlled alpha delay activity precedes stimulus-induced gamma-band activity in visual cortex

Recent findings in the visual system of nonhuman primates have demonstrated an important role of gamma-band activity (40–100 Hz) in the feedforward flow of sensory information, whereas feedback control appears to be established dynamically by oscillations in the alpha (8–13 Hz) and beta (13–18 Hz) bands (van Kerkoerle et al., 2014; Bastos et al., 2015). It is not clear, however, how alpha oscillations are controlled and how they interact with the flow of visual information mediated by gamma-band activity. Using noninvasive human MEG recordings in subjects performing a visuospatial attention task, we show that fluctuations in alpha power during a delay period in a spatial attention task preceded subsequent stimulus-driven gamma-band activity. Importantly, these interactions correlated with behavioral performance. Using Granger analysis, we further show that the right frontal-eye field (rFEF) exerted feedback control of the visual alpha oscillations. Our findings suggest that alpha oscillations controlled by the FEF route cortical information flow by modulating gamma-band activity

Взаимодействие ОАО «Гомсельмаш» с учреждениями высшего образования при организации практического обучения студентов

This paper aims to improve our understanding of how and where global supply-chains linkconsumers of agricultural and forest commodities across the world to forest destruction in tropicalcountries. A better understanding of these linkages can help inform and support the design ofdemand-side interventions to reduce tropical deforestation. To that end, we map the link betweendeforestation for four commodities (beef, soybeans, palm oil, and wood products) in eight casecountries (Argentina, Bolivia, Brazil, Paraguay, Democratic Republic of the Congo, Indonesia,Malaysia, and Papua New Guinea) to consumption, through international trade. Although few,the studied countries comprise a large share of the internationally traded volumes of the analyzedcommodities: 83% of beef and 99% of soybean exports from Latin America, 97% of global palmoil exports, and roughly half of (official) tropical wood products trade. The analysis covers theperiod 2000-2009. We find that roughly a third of tropical deforestation and associated carbonemissions (3.9 Mha and 1.7 GtCO2) in 2009 can be attributed to our four case commodities in oureight case countries. On average a third of analyzed deforestation was embodied in agriculturalexports, mainly to the EU and China. However, in all countries but Bolivia and Brazil, exportmarkets are dominant drivers of forest clearing for our case commodities. If one excludes Brazilianbeef on average 57% of deforestation attributed to our case commodities was embodied in exports.The share of emissions that was embodied in exported commodities increased between 2000 and2009 for every country in our study except Bolivia and Malaysia.Working Paper 384</p

Electrophysiological Low-Frequency Coherence and Cross-Frequency Coupling Contribute to BOLD Connectivity

SummaryBrain networks are commonly defined using correlations between blood oxygen level-dependent (BOLD) signals in different brain areas. Although evidence suggests that gamma-band (30–100 Hz) neural activity contributes to local BOLD signals, the neural basis of interareal BOLD correlations is unclear. We first defined a visual network in monkeys based on converging evidence from interareal BOLD correlations during a fixation task, task-free state, and anesthesia, and then simultaneously recorded local field potentials (LFPs) from the same four network areas in the task-free state. Low-frequency oscillations (<20 Hz), and not gamma activity, predominantly contributed to interareal BOLD correlations. The low-frequency oscillations also influenced local processing by modulating gamma activity within individual areas. We suggest that such cross-frequency coupling links local BOLD signals to BOLD correlations across distributed networks

Interacting rhythms enhance sensitivity of target detection in a fronto-parietal computational model of visual attention

Even during sustained attention, enhanced processing of attended stimuli waxes and wanes rhythmically, with periods of enhanced and relatively diminished visual processing (and subsequent target detection) alternating at 4 or 8 Hz in a sustained visual attention task. These alternating attentional states occur alongside alternating dynamical states, in which lateral intraparietal cortex (LIP), the frontal eye field (FEF), and the mediodorsal pulvinar exhibit different activity and functional connectivity at α, β, and γ frequencies—rhythms associated with visual processing, working memory, and motor suppression. To assess whether and how these multiple interacting rhythms contribute to periodicity in attention, we propose a detailed computational model of FEF and LIP, which reproduced the rhythmic dynamics and behavioral consequences of observed attentional states when driven by θ-rhythmic inputs simulating experimentally-observed pulvinar activity. This model reveals that the frequencies and mechanisms of the observed rhythms allow for peak sensitivity in visual target detection while maintaining functional flexibility.https://www.biorxiv.org/content/10.1101/2021.02.18.431872v