ORCID Profile
0000-0001-8874-3586
Current Organisation
University of Padua
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Sensory Processes, Perception and Performance | Sensory Systems | Psychology and Cognitive Sciences not elsewhere classified | Neurosciences
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Psychology and Cognitive Sciences | Technological and Organisational Innovation |
Publisher: IEEE
Date: 2007
Publisher: Society for Neuroscience
Date: 30-01-2013
DOI: 10.1523/JNEUROSCI.3449-12.2013
Abstract: Exposure of cortical cells to sustained sensory stimuli results in changes in the neuronal response function. This phenomenon, known as adaptation, is a common feature across sensory modalities. Here, we quantified the functional effect of adaptation on the ensemble activity of cortical neurons in the rat whisker-barrel system. A multishank array of electrodes was used to allow simultaneous s ling of neuronal activity. We characterized the response of neurons to sinusoidal whisker vibrations of varying litude in three states of adaptation. The adaptors produced a systematic rightward shift in the neuronal response function. Consistently, mutual information revealed that peak discrimination performance was not aligned to the adaptor but to test litudes 3–9 μm higher. Stimulus presentation reduced single neuron trial-to-trial response variability (captured by Fano factor) and correlations in the population response variability (noise correlation). We found that these two types of variability were inversely proportional to the average firing rate regardless of the adaptation state. Adaptation transferred the neuronal operating regime to lower rates with higher Fano factor and noise correlations. Noise correlations were positive and in the direction of signal, and thus detrimental to coding efficiency. Interestingly, across all population sizes, the net effect of adaptation was to increase the total information despite increasing the noise correlation between neurons.
Publisher: Springer Science and Business Media LLC
Date: 06-03-2019
DOI: 10.1038/S41598-018-33000-1
Abstract: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
Publisher: Frontiers Media SA
Date: 21-08-2019
Publisher: IEEE
Date: 08-2008
Publisher: American Physiological Society
Date: 2011
Abstract: We used the rat whisker touch as a model system to investigate the correlation between the response function of cortical neurons and the behavior of rats in a sensory detection versus discrimination task. The rat whisker–barrel system is structurally well characterized and represents one of the main channels through which rodents collect information about the environment. In experiment 1, we recorded neuronal activity ( n = 235) in the whisker area of the rat somatosensory cortex in anesthetized rats while applying vibrotactile stimuli of varying litudes to the whiskers. Neurons showed a characteristic sigmoidal input–output function, with an accelerating nonlinearity at low stimulus litudes and a compressive nonlinearity at high stimulus litudes. We further quantified the performance of in idual neurons for stimulus detection and for discrimination across different stimulus pairs with identical litude differences. For near-threshold stimuli, the neuronal discrimination performance surpassed the detection performance despite the fact that detection and discrimination represented identical litude differences. This is consistent with the accelerating nonlinearity observed at low stimulus intensities. In the second stage of the experiment, four rats were trained to select the higher- litude stimulus between two vibrations applied to their whiskers. Similar to neuronal results, the rats' performance was better for the discrimination task compared with the detection task. The behavioral performance followed the same trend as that of the population of in idual neurons. Both behavioral and neuronal data are consistent with the “pedestal effect” previously reported in human psychophysics.
Publisher: IEEE
Date: 08-2008
Publisher: Springer Science and Business Media LLC
Date: 13-09-2017
DOI: 10.1038/S41598-017-11477-6
Abstract: Neuronal adaptation is a common feature observed at various stages of sensory processing. Here, we quantified the time course of adaptation in rat somatosensory cortex. Under urethane anesthesia, we juxta-cellularly recorded single neurons (n = 147) while applying a series of whisker deflections at various frequencies (2–32 Hz). For ~90% of neurons, the response per unit of time decreased with frequency. The degree of adaptation increased along the train of deflections and was strongest at the highest frequency. However, a subset of neurons showed facilitation producing higher responses to subsequent deflections. The response latency to consecutive deflections increased both for neurons that exhibited adaptation and for those that exhibited response facilitation. Histological reconstruction of neurons (n = 45) did not reveal a systematic relationship between adaptation profiles and cell types. In addition to the periodic stimuli, we applied a temporally irregular train of deflections with a mean frequency of 8 Hz. For 70% of neurons, the response to the irregular stimulus was greater than that of the 8 Hz regular. This increased response to irregular stimulation was positively correlated with the degree of adaptation. Altogether, our findings demonstrate high levels of ersity among cortical neurons, with a proportion of neurons showing facilitation at specific temporal intervals.
Publisher: Public Library of Science (PLoS)
Date: 31-12-2014
Publisher: Elsevier BV
Date: 08-2005
DOI: 10.1016/J.COGBRAINRES.2005.02.012
Abstract: Configural processing could develop for non-face visual objects as one becomes familiar with those objects through repeated exposure. To explore the role of familiarity in object recognition, we studied the effect of adaptation to a visual object (adapting stimulus) on the identification performance of other objects (test stimulus) while adapting and test stimuli were exactly the same, shared parts or were completely different. We used a subset of English alphabets (p, q, d and b) as familiar objects and an unfamiliar set of symbols constructed from same parts but with different configurations. Adaptation to a member of each set led to a lower identification performance for that object in a crowding paradigm. Adaptation to each member of the unfamiliar set resulted in decreased identification performance for the same object and those members of the set that shared parts with the adapting stimulus. But no such transfer of adaptation was observed for the familiar set. Our results support the notion that processing of object parts plays an important role in the recognition of unfamiliar objects while recognition of familiar objects is mainly based on configural processing mechanisms.
Publisher: Frontiers Media SA
Date: 24-03-2016
Publisher: Proceedings of the National Academy of Sciences
Date: 04-01-2012
Abstract: Rats use their vibrissal sensory system to collect information about the nearby environment. They can accurately and rapidly identify object location, shape, and surface texture. Which features of whisker motion does the sensory system extract to construct sensations? We addressed this question by training rats to make discriminations between sinusoidal vibrations simultaneously presented to the left and right whiskers. One set of rats learned to reliably identify which of two vibrations had higher frequency ( f 1 vs. f 2 ) when litudes were equal. Another set of rats learned to reliably identify which of two vibrations had higher litude ( A 1 vs. A 2 ) when frequencies were equal. Although these results indicate that both elemental features contribute to the rats’ sensation, a further test found that the capacity to discriminate A and f was reduced to chance when the difference in one feature was counterbalanced by the difference in the other feature: Rats could not discriminate litude or frequency whenever A 1 f 1 = A 2 f 2 . Thus, vibrations were sensed as the product Af rather than as separable elemental features, A and f . The product Af is proportional to a physical entity, the mean speed. Analysis of performance revealed that rats extracted more information about differences in Af than predicted by the sum of the information in elemental differences. These behavioral experiments support the predictions of earlier physiological studies by demonstrating that rats are “blind” to the elemental features present in a sinusoidal whisker vibration instead, they perceive a composite feature, the speed of whisker motion.
Publisher: Frontiers Media SA
Date: 06-07-2016
Publisher: Cold Spring Harbor Laboratory
Date: 06-09-2022
DOI: 10.1101/2022.09.06.506303
Abstract: Motion is one of the fundamental qualities not only of vision, but also of touch. Manipulation and exploration of objects involves different forms of movement between the skin and objects. A different form of tactile motion from remote sources is through substrate vibrations, and is present in arthropods such as insects and spiders, enabling them to localise approaching preys and predators. Here, we quantify the extent to humans perceive tactile motion based on vibrations sensed by fingertips. We employed a novel stimulation paradigm in which a pair of vibrations (100 Hz) with sinusoidal envelopes (0.5 cycle/s) and various phase differences between the two vibrations were delivered to two fingertips. The phase difference between the vibrations generated perception of a virtual motion across the fingertips. The findings suggest that human tactile system possesses the sensory channel for detection of motion through substrate vibrations, which is fundamentally different from tactile motion mechanisms during active surface exploration. We propose two potential neural computations underlying processing this form of motion one based on phase difference or time delay detection, and the second based on temporal order and interval duration processing.
Publisher: IEEE
Date: 2010
Publisher: Frontiers Media SA
Date: 29-10-2021
DOI: 10.3389/FNINS.2021.770011
Abstract: In the natural environment, organisms are constantly exposed to a continuous stream of sensory input. The dynamics of sensory input changes with organism's behaviour and environmental context. The contextual variations may induce & -fold change in the parameters of the stimulation that an animal experiences. Thus, it is vital for the organism to adapt to the new diet of stimulation. The response properties of neurons, in turn, dynamically adjust to the prevailing properties of sensory stimulation, a process known as “neuronal adaptation.” Neuronal adaptation is a ubiquitous phenomenon across all sensory modalities and occurs at different stages of processing from periphery to cortex. In spite of the wealth of research on contextual modulation and neuronal adaptation in visual and auditory systems, the neuronal and computational basis of sensory adaptation in somatosensory system is less understood. Here, we summarise the recent finding and views about the neuronal adaptation in the rodent whisker-mediated tactile system and further summarise the functional effect of neuronal adaptation on the response dynamics and encoding efficiency of neurons at single cell and population levels along the whisker-mediated touch system in rodents. Based on direct and indirect pieces of evidence presented here, we suggest sensory adaptation provides context-dependent functional mechanisms for noise reduction in sensory processing, salience processing and deviant stimulus detection, shift between integration and coincidence detection, band-pass frequency filtering, adjusting neuronal receptive fields, enhancing neural coding and improving discriminability around adapting stimuli, energy conservation, and disambiguating encoding of principal features of tactile stimuli.
Publisher: IEEE
Date: 2007
Publisher: Society for Neuroscience
Date: 11-09-2013
DOI: 10.1523/JNEUROSCI.1313-13.2013
Abstract: We showed recently that exposure to whisker vibrations enhances coding efficiency in rat barrel cortex despite increasing correlations in variability (Adibi et al., 2013). Here, to understand how adaptation achieves this improvement in sensory representation, we decomposed the stimulus information carried in neuronal population activity into its fundamental components in the framework of information theory. In the context of sensory coding, these components are the entropy of the responses across the entire stimulus set (response entropy) and the entropy of the responses conditional on the stimulus (conditional response entropy). We found that adaptation decreased response entropy and conditional response entropy at both the level of single neurons and the pooled activity of neuronal populations. However, the net effect of adaptation was to increase the mutual information because the drop in the conditional entropy outweighed the drop in the response entropy. The information transmitted by a single spike also increased under adaptation. As population size increased, the information content of in idual spikes declined but the relative improvement attributable to adaptation was maintained.
Publisher: Public Library of Science (PLoS)
Date: 02-01-2014
Publisher: IEEE
Date: 07-2008
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.JTBI.2019.02.024
Abstract: A neuron is the fundamental unit of the nervous system and the brain, crucial for transducing information in form of trains of electrical pulses known as action potentials. The connection between neurons is through synapses, enabling communication between neurons. This communication link is one of the key elements in processing of information from a neuron to another neuron. The strength of the synapses may vary over time, a phenomenon known as synaptic plasticity. This is the process by which it is believed memory and learning is governed. Recent studies revealed environmental factors affect the strength of synapses, and the way neurons communicate to each other. This poses the question as to what extent the pre- and post- synaptic neurons sense the environmental changes, and in turn adjust their synaptic link. Here, we model the behavior of an interconnected neuronal network in various environmental conditions as a multi-agent system in a game theoretic framework. We focus on a CA1 lattice subfield as an ex le plastic neuronal network. Our analysis revealed the neuronal network converges to different equilibria depending on the environmental changes. The model well-predicts the behavior of the network compared to a well-known theoretical model of in idual neurons.
Publisher: IEEE
Date: 2007
Location: Iran (Islamic Republic of)
Location: Iran (Islamic Republic of)
Start Date: 2016
End Date: 2020
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2020
End Date: 2022
Funder: Australian Research Council
View Funded ActivityStart Date: 2020
End Date: 2022
Funder: Università degli Studi di Padova
View Funded ActivityStart Date: 12-2020
End Date: 06-2024
Amount: $413,614.00
Funder: Australian Research Council
View Funded Activity