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

Az éntudat kialakulása

Jelen dolgozat az éntudattal rendelkező élőlények tudatának fejlődését vizsgálja. Az első rész főemlősök és csecsemők tükörképükre adott viselkedéses reakcióit elemzi, a hangsúlyt az éntudat jelenlétére utaló viselkedésformák fokozatosan fejlődő jellegére helyezve. Áttekintést nyújt a különböző modalitásokhoz tartozó testsémák eltérő reprezentációiról és magyarázatot kíván nyújtani az éntudat önszervező kialakulására. A második rész a testsémák és az éntudat önszervező folyamatait a matematikai csoportelmélet és az eltérő logikai szintek elméletével írja le, valamint a környezet és az éntudat közti információáramlás többszintű, komplex modelljét mutatja be.Present paper investigates the development of mind in living creatures showing the signs of having self-awareness. Behavioral phenomena of primates and human infants appearing to their mirror image are analised in the first part of the paper, laying the emphasis on the gradual quality of development of self-awareness. A survey of different representations belonging to variant sense modalities is provided in order to explain the self-organizing emergence of self-awareness. The second part describes the self-modifying process of body-schemes and self-awareness using mathematical group-theory and the theory of sets as metaphorical devices. A multi-level complex model of information-flow between the mind and environment is outlined. The main purpose of the paper is to provide a better understanding of the phenomenon of downward causation and to fill the gap of the ancient question of the body-mind (brain-mind) problem. This rather ambitious contribution to mind research also implies vague hints for the ones that are concerned about the research of artificial intelligence

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

EEG and ERP biomarkers of Alzheimer's disease: a critical review

Here we critically review studies that used electroencephalography (EEG) or event-related potential (ERP) indices as a biomarker of Alzheimer's disease. In the first part we overview studies that relied on visual inspection of EEG traces and spectral characteristics of EEG. Second, we survey analysis methods motivated by dynamical systems theory (DST) as well as more recent network connectivity approaches. In the third part we review studies of sleep. Next, we compare the utility of early and late ERP components in dementia research. In the section on mismatch negativity (MMN) studies we summarize their results and limitations and outline the emerging field of computational neurology. In the following we overview the use of EEG in the differential diagnosis of the most common neurocognitive disorders. Finally, we provide a summary of the state of the field and conclude that several promising EEG/ERP indices of synaptic neurotransmission are worth considering as potential biomarkers. Furthermore, we highlight some practical issues and discuss future challenges as well

Emotion-Related Visual Mismatch Responses in Schizophrenia: Impairments and Correlations with Emotion Recognition.

BACKGROUND AND OBJECTIVES:Mismatch negativity (MMN) is an event-related potential (ERP) measure of preattentional sensory processing. While deficits in the auditory MMN are robust electrophysiological findings in schizophrenia, little is known about visual mismatch response and its association with social cognitive functions such as emotion recognition in schizophrenia. Our aim was to study the potential deficit in the visual mismatch response to unexpected facial emotions in schizophrenia and its association with emotion recognition impairments, and to localize the sources of the mismatch signals. EXPERIMENTAL DESIGN:The sample comprised 24 patients with schizophrenia and 24 healthy control subjects. Controls were matched individually to patients by gender, age, and education. ERPs were recorded using a high-density 128-channel BioSemi amplifier. Mismatch responses to happy and fearful faces were determined in 2 time windows over six regions of interest (ROIs). Emotion recognition performance and its association with the mismatch response were also investigated. PRINCIPAL OBSERVATIONS:Mismatch signals to both emotional conditions were significantly attenuated in patients compared to controls in central and temporal ROIs. Controls recognized emotions significantly better than patients. The association between overall emotion recognition performance and mismatch response to the happy condition was significant in the 250-360 ms time window in the central ROI. The estimated sources of the mismatch responses for both emotional conditions were localized in frontal regions, where patients showed significantly lower activity. CONCLUSIONS:Impaired generation of mismatch signals indicate insufficient automatic processing of emotions in patients with schizophrenia, which correlates strongly with decreased emotion recognition

Short GSM mobile phone exposure does not alter human auditory brainstem response

<p>Abstract</p> <p>Background</p> <p>There are about 1.6 billion GSM cellular phones in use throughout the world today. Numerous papers have reported various biological effects in humans exposed to electromagnetic fields emitted by mobile phones. The aim of the present study was to advance our understanding of potential adverse effects of the GSM mobile phones on the human hearing system.</p> <p>Methods</p> <p>Auditory Brainstem Response (ABR) was recorded with three non-polarizing Ag-AgCl scalp electrodes in thirty young and healthy volunteers (age 18–26 years) with normal hearing. ABR data were collected before, and immediately after a 10 minute exposure to 900 MHz pulsed electromagnetic field (EMF) emitted by a commercial Nokia 6310 mobile phone. Fifteen subjects were exposed to genuine EMF and fifteen to sham EMF in a double blind and counterbalanced order. Possible effects of irradiation was analyzed by comparing the latency of ABR waves I, III and V before and after genuine/sham EMF exposure.</p> <p>Results</p> <p>Paired sample t-test was conducted for statistical analysis. Results revealed no significant differences in the latency of ABR waves I, III and V before and after 10 minutes of genuine/sham EMF exposure.</p> <p>Conclusion</p> <p>The present results suggest that, in our experimental conditions, a single 10 minute exposure of 900 MHz EMF emitted by a commercial mobile phone does not produce measurable immediate effects in the latency of auditory brainstem waves I, III and V.</p

Visual mismatch negativity (vMMN): A review and meta-analysis of studies in psychiatric and neurological disorders

The visual mismatch negativity (vMMN) response is an event-related potential (ERP) component, which is automatically elicited by events that violate predictions based on prior events. VMMN experiments use visual stimulus repetition to induce predictions, and vMMN is obtained by subtracting the response to rare unpredicted stimuli from those to frequent stimuli. One increasingly popular interpretation of the mismatch response postulates that vMMN, similar to its auditory counterpart (aMMN), represents a prediction error response generated by cortical mechanisms forming probabilistic representations of sensory signals. Here we discuss the physiological and theoretical basis of vMMN and review thirty-three studies from the emerging field of its clinical applications, presenting a meta-analysis of findings in schizophrenia, mood disorders, substance abuse, neurodegenerative disorders, developmental disorders, deafness, panic disorder and hypertension. Furthermore, we include reports on aging and maturation as they bear upon many clinically relevant conditions. Surveying the literature we found that vMMN is altered in several clinical populations which is in line with aMMN findings. An important potential advantage of vMMN however is that it allows the investigation of deficits in predictive processing in cognitive domains which rely primarily on visual information; a principal sensory modality and thus of vital importance in environmental information processing and response, and a modality which arguably may be more sensitive to some pathological changes. However, due to the relative infancy of research in vMMN compared to aMMN in clinical populations its potential for clinical application is not yet fully appreciated. The aim of this review and meta-analysis therefore is to present, in a detailed systematic manner, the findings from clinically-based vMMN studies, to discuss their potential impact and application, to raise awareness of this measure and to improve our understanding of disease upon fundamental aspects of visual information processing

Visual mismatch negativity: a predictive coding view

An increasing number of studies investigate the visual mismatch negativity (vMMN) or use the vMMN as a tool to probe various aspects of human cognition. This paper reviews the theoretical underpinnings of vMMN in the light of methodological considerations and provides recommendations for measuring and interpreting the vMMN. The following key issues are discussed from the experimentalist's point of view in a predictive coding framework: (1) experimental protocols and procedures to control “refractoriness” effects; (2) methods to control attention; (3) vMMN and veridical perception