Sound predictability as a higher-order cue in auditory scene analysis

A major challenge for the auditory system is to disentangle signals emitted by two or more sound sources that are active in a temporally interleaved manner (sequential stream segregation). Besides distinct characteristics of the individual signals (e.g., their timbre, location, and pitch), one important cue for distinguishing the sound sources is how their emitted signals unfold over time. It seems intuitively plausible that signals that unfold predictably with respect to their acoustic features and time-points of occurrence, such as the repetitive signature of a train moving on the rails, can be more readily identified as originating from one sound source. Based on this rationale, predictive elements have successfully been incorporated into computational models of auditory scene analysis for many years

Perceptual bistability in auditory streaming: how much do stimulus features matter?

The auditory two-tone streaming paradigm has been used extensively to study the mechanisms that underlie the decomposition of the auditory input into coherent sound sequences. Using longer tone sequences than usual in the literature, we show that listeners hold their first percept of the sound se¬quence for a relatively long period, after which perception switches between two or more alternative sound organizations, each held on average for a much shorter duration. The first percept also differs from subsequent ones in that stimulus parameters influence its quality and duration to a far greater degree than the subsequent ones. We propose an account of auditory streaming in terms of rivalry be¬tween competing temporal associations based on two sets of processes. The formation of associations (discovery of alternative interpretations) mainly affects the first percept by determining which sound group is discovered first and how long it takes for alternative groups to be established. In contrast, sub¬sequent percepts arise from stochastic switching between the alternatives, the dynamics of which are determined by competitive interactions between the set of coexisting interpretations

Inger-vezérelt és figyelmi integrációs folyamatok az észlelésben = Stimulus-driven and attentive integration processes in perception

A beérkező szenzoros információk nagyobb egységekbe szervezése (integrációja) az észlelő és kognitív rendszer egyik legfőbb feladata. A pályázat során négy területen vizsgáltunk integrációs-szegregációs folyamatokat. 1) Megállapítottuk, hogy az akusztikus vonások egységes inger-reprezentációba integrálása figyelem nélkül is megtörténik, bár figyelmi hatások módosíthatják az integrációs folyamat eredményét. 2) Kimutattuk, hogy a hallási idői csoportosítás automatikusan készített hallási előrejelzések mentén valósul meg. 3) Elsőként találtunk olyan eseményfüggő agyi potenciál komponenst, amely integrált audiovizuális emléknyomok automatikus létrehozását mutatja az agyban. 4) Általánosítottuk a nem figyelt hangingereknek a figyelt hangok feldolgozására gyakorolt hatását vizsgáló paradigmát és átértelmeztük az egyes eseményfüggő agy potenciál komponensek által tükrözött feldolgozó részfolyamatok szerepét az elterelődés és reorientáció folyamatában. | Organizing sensory information into larger units (integration) is a primary function of the perceptual cognitive system. The funded research investigated four types of processes of integration segregation. 1) We found that acoustic features are integrated into a unitary stimulus representation even outside the focus of attention, although attentive processes may modulate the outcome of the integration process. 2) We have shown that auditory temporal grouping is guided by automatically created predictions of upcoming sounds. 3) We obtained the first event related brain potential evidence of the automatic formation of integrated audiovisual memory traces in the brain. 4) We generalized the stimulus paradigm used for studying the effects of unattended auditory stimuli on the processing of attended sounds and reinterpreted the role of the processes reflected in the various event related brain potential components in the course of distraction and reorientation

Modulation-frequency acts as a primary cue for auditory stream segregation

In our surrounding acoustic world sounds are produced by different sources and interfere with each other before arriving to the ears. A key function of the auditory system is to provide consistent and robust descriptions of the coherent sound groupings and sequences (auditory objects), which likely correspond to the various sound sources in the environment. This function has been termed auditory stream segregation. In the current study we tested the effects of separation in the frequency of amplitude modulation on the segregation of concurrent sound sequences in the auditory stream-segregation paradigm (van Noorden 1975). The aim of the study was to assess 1) whether differential amplitude modulation would help in separating concurrent sound sequences and 2) whether this cue would interact with previously studied static cues (carrier frequency and location difference) in segregating concurrent streams of sound. We found that amplitude modulation difference is utilized as a primary cue for the stream segregation and it interacts with other primary cues such as frequency and location difference

Elemi szabályosságok reprezentációja a látásban: Pszichofiziológiai vizsgálatok = Representation of elementary rules in vision: Psychophysiological investigations

Fő célunk a vizuális automatikus emlékezeti rendszer sajátságainak vizsgálata volt a vizuális eltérési negativitás eseményhez (EN) kötött potenciál összetevő elemzésével. Mivel az eltérési negativitás annak jele, ha egy esemény megszegi az ingersorozat szabályszerűségeit, jelentkezése rámutat arra, ha az emlékezeti regisztrálta a szabályszerűséget. Eredményeink szerint az emlékezeti rendszer nem egyedi vizuális sajátságokat tárol, hanem eseményeket, azaz egy objektum több sajátságának egyidejű változása nem növeli az eltérő negativitást. Additív hatás mutatkozik viszont, ha egyidejűleg több esemény változik. Az aktuálsi viselkedés és az automatikus változás detekciója nem független: a feladat azonos típusú változások esetén az eltérési negativitás csökken. Eltérően a hallás hasonló rendszeréhet, a vizuális rendszer nem érzékeny hosszabb tartamú emlékezeti reaktivációs hatásaira. Valódi és látszólagos eltérések hasonló EN hatásokkal járnak. A rendszer képes perceptuális és érzelmi kategóriák (horizontális szimmetria) regisztrációjára, viszont nem jön létre EN, ha az események sorozatából nem jön létre szabályszerűség reprezentációja. Mivel az emlékezeti rendszer képes feltételes szabályszerűségek tárolására, így valószínűsíthető, hogy a vizuális észlelésben prediktív funkcióval rendelkezik. | As the main purpose of the project was the investigation of the characteristics of an implicit visual memory system. The method was the analysis of the visual mismatch negativity (vMMN) event-related potential component. VMMN emerges whenever an event violates the regularity of stimulus sequences, therefore vMMN appearance is an indicator of registered regularity. As our results show, beyond the registration of individual visual features, the system is capable of storing deviant events, i.e., vMMN to event with simultaneous deviant features does not elicit increased vMMN. However, simultaneous deviancy of two events elicits additive vMMN. VMMN is not independent of the task-related stimuli. Irrelevant stimuli shearing the characteristics of task-relevant ones elicit vMMN with decreased amplitude. Contrary to the homolog auditory memory, the system underlying vMMN is insensitive to long-term memory effects (reactivation). Real and apparent (illusory) deviancies elicit similar vMMN. The system is capable of registering perceptual (horizontal symmetry) and emotional categories. However, without the acquisition of category, no vMMN emerges. The system is sensitive to conditional regularities; therefore it is possible that it has a predictive function in visual perceptio

Transitional probabilities are prioritized over stimulus/pattern probabilities in auditory deviance detection: Memory basis for predictive sound processing

Representations encoding the probabilities of auditory events do not directly support predictive processing. In contrast, information about the probability with which a given sound follows another (transitional probability) allows predictions of upcoming sounds. We tested whether behavioral and cortical auditory deviance detection (the latter indexed by the mismatch negativity event-related potential) relies on probabilities of sound patterns or on transitional probabilities. We presented healthy adult volunteers with three types of rare tone-triplets among frequent standard triplets of High-Low-High (HLH) or LHL pitch structure: proximity deviant (HHH/LLL), reversal deviant (LHL/HLH), and first-tone deviant (LLH/HHL). If deviance detection was based on pattern probability, reversal and first-tone deviants should be detected with similar latency because both differ from the standard at the first pattern position. If deviance detection was based on transitional probabilities, then reversal deviants should be the most difficult to detect, because, unlike the other two deviants, they contain no low-probability pitch transitions. The data clearly showed that both behavioral and cortical auditory deviance detection utilizes transitional probabilities. Thus the memory traces underlying cortical deviance detection may provide a link between stimulus-probability based change/novelty detectors operating at lower levels of the auditory system and higher auditory cognitive functions that involve predictive processing

Előbb az összetett, később az egyszerű: Csecsemők magasabb szintű hangfeldolgozási képességei a beszédértés előtti időszakban

Bár a legalapvetőbb hangjellemzők észlelt felbontása fiatal csecsemőknél messze elmarad a felnőttek hasonló képességeitől, a fejlettebb hangfeldolgozási funkciókat tekintve minőségileg nem különböznek tőlük. A csecsemők kompetens észlelők a hangok világában, hallási tárgyreprezentációkat alkotnak, és képesek kiemelni a beérkező hangok bonyolult belső összefüggéseit. Áttekintve a hangfeldolgozási képességek mintázatát fiatal csecsemőknél, a cikk amellett érvel, hogy e képességek jelentős része a hangokkal történő kommunikáció, azon belül is a dialógusok felépítésének és fenntartásának szolgálatában áll. Az emberi fejlődésben a szociális kommunikációnak kiemelt jelentősége van, mivel lehetővé teszi, hogy az élet kezdetén rövid idő alatt igen nagy mennyiségű kész tudást vehessünk át. Ez indokolja, hogy a fiatal csecsemők hallórendszere az első pillanattól kezdve készen áll az emberi tanulás e leghatékonyabb formájának támogatására

Feature predictability flexibly supports auditory stream segregation or integration

Many sound sources emit series of discrete sounds. Auditory perception must bind these sounds together (stream integration) while separating them from sounds emitted by other sources (stream segregation). One cue for identifying successive sounds that belong together is the predictability between their feature values. Previous studies have demonstrated that independent predictable patterns appearing separately in two interleaved sound sequences support perceptual segregation. The converse case, whether a joint predictable pattern in a mixture of interleaved sequences supports perceptual integration, has not yet been put to a rigorous empirical test. This was mainly due to difficulties in manipulating the predictability of the full sequence independently of the predictability of the interleaved subsequences. The present study implemented such an independent manipulation. Listeners continuously indicated whether they perceived a tone sequence as integrated or segregated, while predictable patterns set up to support one or the other percept were manipulated without the participants’ knowledge. Perceptual reports demonstrate that predictability supports stream segregation or integration depending on the type of predictable pattern that is present in the sequence. The effects of predictability were so pronounced as to qualitatively flip perception from predominantly (62%) integrated to predominantly (73%) segregated. These results suggest that auditory perception flexibly responds to encountered regular patterns, favoring predictable perceptual organizations over unpredictable ones. Besides underlining the role of predictability as a cue within auditory scene analysis, the present design also provides a general framework that accommodates previous investigations focusing on sub-comparisons within the present set of experimental manipulations. Results of intermediate conditions shed light on why some previous studies have obtained little to no effects of predictability on auditory scene analysis

Different roles of similarity and predictability in auditory stream segregation

Sound sources often emit trains of discrete sounds, such as a series of footsteps. Previously, two dif¬ferent principles have been suggested for how the human auditory system binds discrete sounds to¬gether into perceptual units. The feature similarity principle is based on linking sounds with similar characteristics over time. The predictability principle is based on linking sounds that follow each other in a predictable manner. The present study compared the effects of these two principles. Participants were presented with tone sequences and instructed to continuously indicate whether they perceived a single coherent sequence or two concurrent streams of sound. We investigated the influence of separate manipulations of similarity and predictability on these perceptual reports. Both grouping principles affected perception of the tone sequences, albeit with different characteristics. In particular, results suggest that whereas predictability is only analyzed for the currently perceived sound organization, feature similarity is also analyzed for alternative groupings of sound. Moreover, changing similarity or predictability within an ongoing sound sequence led to markedly different dynamic effects. Taken together, these results provide evidence for different roles of similarity and predictability in auditory scene analysis, suggesting that forming auditory stream representations and competition between alter¬natives rely on partly different processes