Search results for "Stimulus"
showing 10 items of 555 documents
Analysis of the human a-wave ERG component
2006
The a-wave is one of the main issues of research in the field of ocular electrophysiology, since it is strictly connected with early photoreceptoral activities. The present study proposes mathematical methods that analyse this component in human subjects, and supports experimental evidence relating to possible correlations among the responses of photoreceptoral units under a light stimulus. The investigation is organized in two parts: the first part concerns the onset and the initial slope, up to the first minimum (about 10-15 ms), the second part deals with the main portion of the wave, up to about 30 ms. In both cases, the a-waves, recorded at various levels of luminance, have been fitted…
How to validate similarity in linear transform models of event-related potentials between experimental conditions?
2014
Abstract Background It is well-known that data of event-related potentials (ERPs) conform to the linear transform model (LTM). For group-level ERP data processing using principal/independent component analysis (PCA/ICA), ERP data of different experimental conditions and different participants are often concatenated. It is theoretically assumed that different experimental conditions and different participants possess the same LTM. However, how to validate the assumption has been seldom reported in terms of signal processing methods. New method When ICA decomposition is globally optimized for ERP data of one stimulus, we gain the ratio between two coefficients mapping a source in brain to two…
Free Word Associations Correspond to Contiguities Between Words in Texts*
2005
A free associative response is the first word a person comes up with after perceiving another word, the so-called associative stimulus. People commonly associate hot to cold, church to priest, and hard to work. According to traditional association theory this behaviour is the result of learning by contiguity: “Objects once experienced together tend to become associated in the imagination, so that when any one of them is thought of, the others are likely to be thought of also, in the same order of sequence or coexistence as before” (James, 1890). This explanation has been rejected by cognitive psychologists who explain the production of associations as the result of symbolic processes which …
Text type attribution modulates pre-stimulus alpha power in sentence reading
2021
Prior knowledge and context-specific expectations influence the perception of sensory events, e.g., speech, as well as complex higher-order cognitive operations like text reading. Here, we focused on pre-stimulus neural activity during sentence reading to examine text type-dependent attentional bias in anticipation of written stimuli, capitalizing on the functional relevance of brain oscillations in the alpha (8–12 Hz) frequency range. Two sex- and age-matched groups of participants (n = 24 each) read identical sentences on a screen at a fixed per-constituent presentation rate while their electroencephalogram was recorded; the groups were differentially instructed to read “sentences” (genre…
Neuronal activity triggers uptake of hematopoietic extracellular vesicles in vivo
2019
Communication with the hematopoietic system is a vital component of regulating brain function in health and disease. Traditionally, the major routes considered for this neuroimmune communication are by individual molecules such as cytokines carried by blood, by neural transmission, or, in more severe pathologies, by the entry of peripheral immune cells into the brain. In addition, functional mRNA from peripheral blood can be directly transferred to neurons via extracellular vesicles (EVs), but the parameters that determine their uptake are unknown. Using varied animal models that stimulate neuronal activity by peripheral inflammation, optogenetics, and selective proteasome inhibition of dop…
Infants' hedonic responsiveness to food odours: a longitudinal study during and after weaning (8, 12 and 22 months)
2013
Abstract Background Olfaction is a highly salient sensory modality in early human life. Neonates show keen olfactory sensitivity and hedonic responsiveness. However, little is known about hedonic olfactory responsiveness between the neonatal period and 2 years of age. In an attempt to fill this gap, this longitudinal follow-up study aimed at investigating hedonic responses to food odours in infants during the first 2 years of life. The second objective was to evaluate whether gender has an influence on hedonic responses during this early period. Four control stimuli and eight odours (four rated by adults as a priori pleasant and four a priori unpleasant) were presented in bottles to 235 inf…
The effects of morphine on the temporal structure of Wistar rat behavioral response to pain in hot-plate
2016
Rationale: The largest amount of researches on the hot-plate test was carried out using quantitative assessments. However, the evaluation of the relationships among the different elements that compose the behavioral response to pain requires different approaches. Although previous studies have provided clear information on the behavioral structure of the response, no data are available on its temporal structure. Objectives: The objective of this study was to investigate the temporal structure of the behavioral response to pain in Wistar rat tested in hot-plate and how this structure was influenced by morphine-induced analgesia. Methods: The behavior of four groups of subjects tested in hot-…
Spontaneous Cingulate High-Current Spikes Signal Normal and Pathological Pain States
2019
Prominent 7–12 Hz oscillations in frontal cortical networks in rats have been reported. However, the mechanism of generation and the physiological function of this brain rhythm have not yet been clarified. Multichannel extracellular field potentials of the ACC were recorded and analyzed using the current source density method in halothane-anesthetized rats. Spontaneous high-current spikes (HCSs) were localized in the deep part of layer II/III and upper part of layer V of the ACC. The frequency of HCSs in the ACC was 7–12 Hz, with an amplitude of 6.5 ± 0.76 mV/mm(2) and duration of 55.24 ± 2.43 ms. The power density significantly decreased (84.56 ± 6.93%, p < 0.05, t test) after pinching the…
Dark exposure affects plasticity-related molecules and interneurons throughout the visual system during adulthood
2020
Several experimental manipulations, including visual deprivation, are able to induce critical period-like plasticity in the visual cortex of adult animals. In this regard, many studies have analyzed the effects of dark exposure in adult animals, but still little is known about the role of interneurons and plasticity-related molecules on such mechanisms. In this study, we analyzed the effects of 10 days of dark exposure on the connectivity and structure of interneurons, both in the primary visual cortex and in the rest of cerebral regions implicated in the transmission of visual stimulus. We found that this environmental manipulation induces changes in the expression of synaptic molecules th…
Attentional processes in typically developing children as revealed using brain event-related potentials and their source localization in Attention Ne…
2019
AbstractAttention-related processes include three functional sub-components: alerting, orienting, and inhibition. We investigated these components using EEG-based, brain event-related potentials and their neuronal source activations during the Attention Network Test in typically developing school-aged children. Participants were asked to detect the swimming direction of the centre fish in a group of five fish. The target stimulus was either preceded by a cue (centre, double, or spatial) or no cue. An EEG using 128 electrodes was recorded for 83 children aged 12–13 years. RTs showed significant effects across all three sub-components of attention. Alerting and orienting (responses to double …