Functional Organization of Visual Cortex in the Owl Monkey

In this study, we compared the organization of orientation preference in visual areas V1, V2, and V3. Within these visual areas, we also quantified the relationship between orientation preference and cytochrome oxidase (CO) staining patterns. V1 maps of orientation preference contained both pinwheels and linear zones. The location of CO blobs did not relate in a systematic way to maps of orientation; although, as in other primates, there were approximately twice as many pinwheels as CO blobs. V2 contained bands of high and low orientation selectivity. The bands of high orientation selectivity were organized into pinwheels and linear zones, but iso-orientation domains were twice as large as those in V1. Quantitative comparisons between bands containing high or low orientation selectivity and CO dark and light bands suggested that at least four functional compartments exist in V2, CO dense bands with either high or low orientation selectivity, and CO light bands with either high or low selectivity. We also demonstrated that two functional compartments exist in V3, with zones of high orientation selectivity corresponding to CO dense areas and zones of low orientation selectivity corresponding to CO pale areas. Together with previous findings, these results suggest that the modular organization of V1 is similar across primates and indeed across most mammals. V2 organization in owl monkeys also appears similar to that of other simians but different from that of prosimians and other mammals. Finally, V3 of owl monkeys shows a compartmental organization for orientation selectivity that remains to be demonstrated in other primates

LCD és CRT képmegjelenítők a vizuális kutatásban

A percepciós kutatásokat nagyban megkönnyítette a személyi számítógépek megjelenése. Inger megjelenítésére kezdetben könnyű hozzáférhetőségük, alacsony áruk és egyszerű használhatóságuk miatt katódsugárcsöves monitort (CRT) használtak. Később egyre jobban elterjedt az olcsóbb, Liquid Chrystal Display (LCD) monitorok használata. A tudományos világ azonban kezdetben bizalmatlansággal fogadta az új technikát. Mindkét technikának megvannak a működési elvükből eredő előnyeik és hátrányaik, amelyek nagymértékben hatást gyakorolhatnak az általunk használt inger észleletére és az arra adott válaszra egyaránt. Az alábbiakból kiderül, hogy a két megjelenítési technika közül nem lehet egyértelmű győztest hirdetni, csak az általunk használt vizsgálati kérdés fényében dönthetjük el, hogy számunkra mely technika a legmegfelelőbb

Az inferotemporális kéreg szerepe az illuzórikus kontúrok feldolgozásában

A látás egyik alapvető mozzanata az alak elkülönítés a háttértől. Az, hogy a látórendszer hogyan képes megoldani ezt a feladatot azonban még mindig kérdés. Az illuzórikus kontúrok (IC) agyi feldolgozásának vizsgálatával megoldhatónak tűnik a probléma. Fiziológiai tanulmányok támasztják alá a VIés V2 szerepét az IC percepciójában, a magasabb kérgi területek szerepére azonban csak utalások vannak, elsősorban léziós vizsgálatokból. Jelen tanulmányban egysejt regisztrációs módszerrel megvizsgáltuk makákó majmoknál az inferotemporális kéreg (IT) szerepét az IC-k feldolgozásában. Eredményeink szerint az IT-ben IC-re alakszelektív sejtek találhatók, ezzel ismét alátámasztottuk az IT szerepét a formalátásban és kiterjesztettük azt az illuzórikus kontúrok által megalkotott formákra is. Feltételezhetjük, hogy Kanizsa illúziók a különböző felületek elkülönítésével segíthetnek a határoló kontúrok azonosításában. One of the fundamental aspects of vision is the figure-ground discrimination. However, how the visual system is able to solve this problem is a yet to be answered. It seems that with the help of illusory contours (IC) the problem can be solved. Physiological studies support the role of VI and V2 in the perception of IC, however there are only a few indications about the role of the superior cortical areas from lesion examinations. In the study we examined the role of the inferotemporal cortex (IT) in the processing of the IC-s in macaque monkeys with single-cell recording. We managed to pinpoint IC figure-selective cells in the IT. Our results support the existing theory about the role of the IT in seeing figures, but we extended it to the figures created by the illusory contours too and we assume that the Kanizsa illusions may help in the identification of bordering contours through the separation of different surfaces

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

Fonološka svjesnost dvojezičnih osoba u vizualnom prepoznavanju riječi

The present study, in which the phonological awareness of bilinguals and the temporal characteristics of written word recognition are studied with mixed language lexical decision tests, is a part of a larger-scale research. The study aims to collect information about the temporal characteristics of word recognition at the orthographic, phonological, and semantic levels of processing. The current research explores the ERP-patterns during the recognition of Hungarian (L1) and English (L2) words, pseudo-words, and non-words. Twenty-three Hungarian–English bilingual participants were tested in an EEG laboratory. All of them have C1 level English proficiency and use English at work and in their everyday lives on a daily basis. In the lexical decision task, the N170 (left temporal electrodes) and N400 (central electrodes) components were more pronounced in word trials than in non-word trials. This activity probably reflects the integrational and meaning-matching processes during word recognition. In the language decision task on pseudo-words, the Hungarian-like strings elicited a late (300-600) negative component at the left frontal electrode sites, missing from the ERP of the English-like strings. Note that the task is different in the two experiments, which probably influences the stimulus processing and the elicited ERP waveforms as well. In the language decision task, phonological awareness has a crucial role, attributing to the observed differences.Ovaj rad u kojemu se istražuje fonološka svjesnost dvojezičnih osoba i vremenska obilježja prepoznavanja pisanih riječi testom mješovite leksičke odluke dio je opsežnijega istraživanja. Cilj je rada prikupiti informacije o vremenskim obilježjima prepoznavanja riječi na ortografskoj, fonološkoj i semantičkoj razini obrade. U radu se istražuju obrasci kognitivnih evociranih potencijala (engl. event-related potentials - ERP) tijekom prepoznavanja riječi, pseudoriječi i neriječi u mađarskome kao prvom (J1) i engleskome kao inom (J2) jeziku. Dvadeset troje ispitanika dvojezičnih u mađarskome i engleskome jeziku ispitani su u laboratoriju uporabom EEG-a. Svi ispitanici vladaju engleskim na razini C1 i njime se redovito služe u poslu i svakodnevnom životu. U zadatcima leksičke odluke komponente N170 (lijeve temporalne elektrode) i N400 (centralne elektrode) bile su izraženije u pokušajima prepoznavanja riječi od prepoznavanja neriječi. Ta aktivnost vjerojatno odražava integracijske procese i procese povezivanja značenja tijekom prepoznavanja riječi. U zadatcima jezične odluke za pseudoriječi, niz koji je sličan mađarskome jeziku elicitirao je kasnu (300-600) negativnu komponentu na strani lijeve frontalne elektrode, što se nije pokazalo u kognitivnim evociranim potencijalima za pseudoriječi slične engleskim riječima. Valja istaknuti da je zadatak bio drugačiji u dvama eksperimentima, što je vjerojatno utjecalo na obradu stimulusa, kao i na elicitirane oblike valova kognitivnih evociranih potencijala. U zadatcima jezične odluke fonološka svjesnost ima ključnu ulogu te doprinosi uočenim razlikama