Gamma oscillations in visual statistical learning correlate with individual behavioral differences

Statistical learning is assumed to be a fundamentally general sensory process across modalities, age, other cognitive functions, and even species. Despite this general role, behavioral testing on regularity acquisition shows great variance among individuals. The current study aimed to find neural correlates of visual statistical learning showing a correlation with behavioral results. Based on a pilot study, we conducted an EEG study where participants were exposed to associated stimulus pairs; the acquisition was tested through a familiarity test. We identified an oscillation in the gamma range (40–70 Hz, 0.5–0.75 s post-stimulus), which showed a positive correlation with the behavioral results. This change in activity was located in a left frontoparietal cluster. Based on its latency and location, this difference was identified as a late gamma activity, a correlate of model-based learning. Such learning is a summary of several top-down mechanisms that modulate the recollection of statistical relationships such as the capacity of working memory or attention. These results suggest that, during acquisition, individual behavioral variance is influenced by dominant learning processes which affect the recall of previously gained information

Schizophrenia and oral health: a literature review [Skizofrénia és szájhigiénia: irodalmi áttekintés]

Az általános betegségek közvetlenül vagy közvetve befolyásolhatják a fogak egészségét és a páciens szájhigiénéjét.A fogorvosi rendelőben megjelenő betegek körében a pszichiátriai kórképek a leggyakoribb rendellenességek közé tartoznak.A fogászati kezelések során az érintetteknek speciális igényeik vannak. A skizofrénia egy olyan krónikus mentálisbetegség, amely a személyes érzelmek és érzések zavaraival jár, illetve mentális és bizonyos tudati funkciók romlásáhozvezet. A tünetek közé tartoznak a téveszmék, a hallucinációk, a rendezetlen gondolkodás és a következetlenség.Amennyiben hasadásos elmezavarban szenvedő páciens jelentkezik kezelésre a fogorvosi rendelőben, pszichiátriaikonzultációt kell biztosítani. Az elektív fogászati beavatkozásokat el kell halasztani mindaddig, amíg a páciens tüneteikontroll alá kerülnek. A gyógyszerek mellékhatásai súlyosak lehetnek, ezért elengedhetetlen a beteg gondos és folyamatosellenőrzése

Illusory flashes and perception

Information from the environment can be based on a single or several modalities. The simultaneous processing of information separated in space and/or time depends on multiple factors. Visual illusions serve as a good tool with which to investigate the parallel processing of information and their interactions. This study was designed to gain information about a unimodal illusion: a target that flashes once seems to flash more as a result of a simultaneously presented inducer flashing several times nearby. The first aim of this work was to understand whether the number of perceived flashes is merely a result of a bias in the criterion level or whether it is based on a real percept. We then clarified how the illusion finds its way into the percept. The final step was designed to establish the logic of the processing in the background by determining whether the modality appropriateness hypothesis, the information reliability hypothesis, or the discontinuity theory best explains the predominant role of the inducer

Statistical learning signals in macaque inferior temporal cortex

Humans are sensitive to statistical regularities in their visual environment, but the nature of the underlying neural statistical learning signals still remains to be clarified. As in human behavioral and neuroimaging studies of statistical learning, we exposed rhesus monkeys to a continuous stream of images, presented without interstimulus interval or reward association. The stimulus set consisted of 3 groups of 5 images each (quintets). The stimulus order within each quintet was fixed, but the quintets were presented repeatedly in a random order without interruption. Thus, only transitional probabilities defined quintets of images. Postexposure recordings in inferior temporal (IT) cortex showed an enhanced response to stimuli that violated the exposed sequence. This enhancement was found only for stimuli that were not predicted by the just preceding stimulus, reflecting a temporally adjacent stimulus relationship, and was sensitive to stimulus order. By comparing IT responses with sequences with and without statistical regularities, we observed a short latency, transient response suppression for stimuli of the sequence with regularities, in addition to a later sustained response enhancement to stimuli that violated the sequence with regularities. These findings constrain models of mechanisms underlying neural responses in predictable temporal sequences, such as predictive coding.status: publishe

Neural correlates of statistical learning in the inferior-temporal cortex of rhesus monkeys

We learn to implicitly extract the statistical regularities in the environment around us, e.g. sequences of stimuli that follow each other (e.g. letters in specific words). In the visual domain, human observers can extract regular sequences of visual stimuli from a continuous stream of visual shapes. The neural correlates of such visual sequence learning are still unclear. Here, we determined whether a neural correlate of short sequences of visual images, presented in a continuous stream, is present in macaque inferior temporal (IT) cortex. Two monkeys passively fixated while a continuous stream of 3 fixed sequences of 5 grayscale images of animals of various species each were presented in a random order. After a passive exposure of two months, we assessed whether the responses of IT neurons showed a correlate of the sequences by introducing deviant stimuli in the fixed standard sets. We compared the multiunit neuronal responses for the deviant stimuli with identical stimuli when presented in the standard, learned sequence. We observed a significant enhancement of the responses to the deviant stimulus and the trailing standard stimuli, when the deviant was either from the same sequence (p <0.05 for each monkey) or from the other two sequences (p <0.05 for each monkey). The neuronal responses to a second deviant stimulus (which followed the first deviant in the standard set) did not differ significantly from the standard. These results demonstrate that monkey IT cortex encodes at least part of a learned temporal sequence in which a stimulus is presented.status: publishe

Encoding of Predictable and Unpredictable Stimuli by Inferior Temporal Cortical Neurons

Animals and humans learn statistical regularities that are embedded in sequences of stimuli. The neural mechanisms of such statistical learning are still poorly understood. Previous work in macaque inferior temporal (IT) cortex demonstrated suppressed spiking activity to visual images of a sequence in which the stimulus order was defined by transitional probabilities (labeled as "standard" sequence), compared with a sequence in which the stimulus order was random ("random" sequence). Here, we asked whether IT neurons encode the images of the standard sequence more accurately compared with images of the random sequence. Previous human fMRI studies in different sensory modalities also found a suppressed response to expected relative to unexpected stimuli but obtained various results regarding the effect of expectation on encoding, with one study reporting an improved classification accuracy of expected stimuli despite the reduced activation level. We employed a linear classifier to decode image identity from the spiking responses of the recorded IT neurons. We found a greater decoding accuracy for images of the standard compared with the random sequence during the early part of the stimulus presentation, but further analyses suggested that this reflected the sustained, stimulus-selective activity from the previous stimulus of the sequence, which is typical for IT neurons. However, the peak decoding accuracy was lower for the standard compared with the random sequence, in line with the reduced response to the former compared with the latter images. These data suggest that macaque IT neurons represent less accurately predictable compared with unpredictable images