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I Czigler

Publications and source records attributed to I Czigler.

At least 19 recordsLinked to original sources
PubMed2001

Organizing sound sequences in the human brain: the interplay of auditory streaming and temporal integration.

The present study examined the relationship between two of the early brain processes of sound organization: auditory streaming and the temporal window of integration (TWI). Presented at a fast stimulus delivery rate, two tones alternating in frequency are perceived as separate streams of high and low sounds. However, when two sounds are presented within a ca. 200 ms temporal window, they are often processed as a single auditory event. Both stream segregation and temporal integration occur even in the absence of focused attention as was shown by their effect on the mismatch negativity (MMN) event-related potential. The goal of the present study was to determine the precedence between these two sound organization processes by using the stimulus-omission MMN paradigm. Infrequently omitting one stimulus from a homogeneous tone sequence only elicits an MMN when the stimulus onset asynchrony separating successive tones is shorter than 170 ms. This demonstrates the effect of the TWI. Magnetic brain responses elicited by infrequent stimulus omissions appearing in a sequence of two alternating tones were recorded. The magnetic MMN was elicited by tone omission when the alternating tones formed a single stream (with no or only small frequency separation between the two tones) but not when separate high and low streams emerged in perception (large frequency separation between the two alternating tones). This result shows that auditory streaming takes precedence over the processes of temporal integration.

Acoustic Stimulation↗
PubMed2001

Event-related potentials and audiovisual stimuli: multimodal interactions.

In a discrimination task event-related potentials (ERPs) were recorded in human participants to simultaneously presented visual and auditory stimuli with relevant and irrelevant auditory and visual features. Stimuli consisted of combinations of a sine-wave tone (either target or non-target frequency) and a rectangle of particular (target or non-target) orientation. In two conditions either the auditory or the visual discrimination was easier. Stimuli with just one target feature elicited attention-related ERP components (selection negativity and N2b in the visual, and N2b in the auditory modality) only if that feature could be easily discriminated. This finding shows the hierarchical organization of attentional processing of auditory and visual features. Target stimuli in both conditions elicited visual and auditory attention-related components. This finding, together with the similarity of ERPs to stimuli without target features suggest, that these components cannot be considered as on-line correlates of elementary discrimination processes.

Acoustic Stimulation↗
PubMed2001

Simultaneously active pre-attentive representations of local and global rules for sound sequences in the human brain.

Regular sequences of sounds (i.e., non-random) can usually be described by several, equally valid rules. Rules allowing extrapolation from one sound to the next are termed local rules, those that define relations between temporally non-adjacent sounds are termed global rules. The aim of the present study was to determine whether both local and global rules can be simultaneously extracted from a sound sequence even when attention is directed away from the auditory stimuli. The pre-attentive representation of a sequence of two alternating tones (differing only in frequency) was investigated using the mismatch negativity (MMN) auditory event-related potential. Both local- and global-rule violations of tone alternation elicited the MMN component while subjects ignored the auditory stimuli. This finding suggests that (a) pre-attentive auditory processes can extract both local and global rules from sound sequences, and (b) that several regularity representations of a sound sequence are simultaneously maintained during the pre-attentive phase of auditory stimulus processing.

Acoustic Stimulation↗
PubMed1999

Pre-attentive detection of vowel contrasts utilizes both phonetic and auditory memory representations.

Event-related brain potentials (ERP) were recorded to infrequent changes of a synthesized vowel (standard) to another vowel (deviant) in speakers of Hungarian and Finnish language, which are remotely related to each other with rather similar vowel systems. Both language groups were presented with identical stimuli. One standard-deviant pair represented an across-vowel category contrast in Hungarian, but a within-category contrast in Finnish, with the other pair having the reversed role in the two languages. Both within- and across-category contrasts elicited the mismatch negativity (MMN) ERP component in the native speakers of either language. The MMN amplitude was larger in across- than within-category contrasts in both language groups. These results suggest that the pre-attentive change-detection process generating the MMN utilized both auditory (sensory) and phonetic (categorical) representations of the test vowels.

Acoustic Stimulation↗
PubMed1999

Brain responses reveal the learning of foreign language phonemes.

Learning to speak a new language requires the formation of recognition patterns for the speech sounds specific to the newly acquired language. The present study demonstrates the dynamic nature of cortical memory representations for phonemes in adults by using the mismatch negativity (MMN) event-related potential. We studied Hungarian and Finnish subjects, dividing the Hungarians into a naive (no knowledge of Finnish) and a fluent (in Finnish) group. We found that the MMN for a contrast between two Finnish phonemes was elicited in the fluent Hungarians but not in the naive Hungarians. This result indicates that the fluent Hungarians developed cortical memory representations for the Finnish phoneme system that enabled them to preattentively categorize phonemes specific to this language.

Adult↗
PubMed1999

Effects of cue information on response production and inhibition measured by event-related potentials.

The aim of this study was to investigate how information carried by a cue stimulus modulate event-related potentials (ERPs) to a subsequent target stimulus which either calls for an overt response (Go stimulus) or no response (Nogo stimulus). One of the cues predicted the likely appearance of the Go stimulus (Go cue) whereas the other cue predicted the likely appearance of the Nogo stimulus (Nogo cue). Our results showed that unpredicted Nogo stimuli elicited enlarged N200 component. This finding supports the notion that Nogo N200 reflects response inhibition processes, i.e., the amplitude of the N200 is a function of the difficulty of response inhibition. In other words, increased N200 to Nogo stimuli following Go cues might be related to increased efforts in activating the response inhibition system thereby interrupting preparations to respond.

Adolescent↗
PubMed1998

Mismatch negativity: deviance detection or the maintenance of the 'standard'.

Electric brain responses were measured to infrequent tones that broke the frequency alternation of two tones, deviated in duration or violated both regularities (alternation and constant duration). Mismatch negativity (MMN) was elicited by both simple deviants with the duration-related MMN peaking approximately 130 ms later than the alternation-related MMN. The double deviant elicited two successive MMNs. Thus violation of each regularity elicited a separate MMN, whereas previous studies showed that multiple temporally separate deviations from a single repetitive standard elicit one MMN only. These results suggest that the primary function of the MMN-generating process is more closely related to maintaining the representation of auditory regularities than to deviance detection per se.

Acoustic Stimulation↗
PubMed1998

Temporal constraints of auditory event synthesis: evidence from ERPs.

The temporal constraints of auditory event synthesis were investigated using event-related potentials. Standard stimuli consisted of an initial constant-frequency segment followed by a frequency glide. Occasionally, stimuli deviating from this standard both in intensity and within the direction of the glide were presented in the otherwise repetitive sound sequence. Previous results suggested that such 'double' deviants elicit only a single mismatch negativity (MMN) if the two temporally separate deviant elements were integrated within a common unit. Two successive MMNs were elicited by double deviants when the initial constant-frequency segment of the sound was 250 ms long, but only one when this segment was 150 ms in duration. The results support the hypothesis that the auditory input is processed in approximately 200 ms long temporal integration windows.

Acoustic Stimulation↗
PubMed1998

Object-related attention: an event-related potential study.

In two experiments reaction time (RT) and event-related potentials (ERPs) were measured to visual stimuli consisting of two objects (Duncan, 1984; Vecera & Farah, 1994). Target stimuli were defined by two features, which either were distributed between the two objects or belonged to a single object. In Experiment 1 the two objects appeared in spatial overlap, whereas in Experiment 2 the two objects were spatially separated. In both experiments RT was shorter in the single-object condition. The late positive component of the ERP (P3) emerged, peaked, and declined earlier in the single-object condition. It is suggested that object-related attention may facilitate the earlier onset of search for the relevant features.

Adult↗
PubMed1998

Attention to features of separate objects: an ERP study of target-shooters and control participants.

In a visual discrimination task stimuli consisted of a color circle and a grating pattern, i.e. target features were distributed between two objects. The relation (hierarchical vs. parallel) between the attentional processing of the task-related features (color and spatial frequency) was investigated by using the methods of event-related potentials (ERPs). Participants with considerable practice in visual attention (target shooters; n = 13) were compared to control subjects (n = 11). Attention-related ERP components, i.e. selection (anterior) positivity (SP), selection negativity (SN), N2 (N2b), furthermore the late positivity (P3b) emerged only if the circle had relevant color. These results suggest preponderance of color processing. Target shooters were faster and more accurate than the control group. Attention-related components (SP, N2b) and the late positivity (P3b) were larger in shooters, but the relations among the attention-related components were the same in two groups, showing similar progression of the target selection process.

Adolescent↗
PubMed1996

Preattentive auditory change detection relies on unitary sensory memory representations.

Event-Related potentials (ERPs) were recorded to series of frequent (standard) and three types of rare (deviant) tones differing from the standard in frequency, duration, or in both features. All deviants elicited the mismatch negativity (MMN) ERP component, indexing the deviation of a sound from the transient auditory memory trace of the standard. Duration deviance could be detected only after the offset of the duration deviant delaying the MMN to this deviant by 70 ms compared with the MMN of the frequency deviant. The MMN to the double deviant extended only to the latency range of the frequency MMN, revealing that feature-MMNs were coordinated by a memory trace integrating the outcome of the various feature analysers.

Acoustic Stimulation↗
PubMed1996

Aging, stimulus identification and the effect of probability: an event-related potential study.

Event-related potentials (ERPs) of younger and older subjects were compared in a simple reaction time (SRT) and in two GoNogo (20% and 80% target probability) tasks. At the T5 location, the NA component (the difference between the ERPs elicited by the frequent stimuli in the GoNogo tasks on the one hand, and the ERPs in the SRT task on the other hand) emerged earlier in the younger group. The N2b was larger in the younger group, and in this group the rare stimuli of the 80% GoNogo task elicited an enlarged N2. When compared to the older group, the stimulus probability in the younger group had a larger effect on the amplitude of the late positivity. The results show age-related changes at an early stage of the information processing activity, and larger sensitivity of the orienting system in the younger subjects.

Adolescent↗
PubMed1996

Effects of colour and lexical relevance on irrelevant stimuli: event-related potential results.

Event-related potentials (ERPs) were recorded in a warning stimulus-imperative stimulus (S1-S2) situation where S1 was either a coloured bar followed by a letter string (S2), or vice versa. When S1 was a coloured bar, reaction time (RT) response was required only to words which were preceded by a bar of a particular colour. When S1 was a letter string, response was required only to bars in a particular colour which were preceded by a word. Contingent negative variation (CNV) appeared only after those S1s which could be followed by a target stimulus. However, bars in the colour of the target elicited attention-related ERP components even if these stimuli were preceded by non-words, i.e. when the subjects could be certain in advance of the appearance of a non-target stimulus.

Adult↗
PubMed1994

Effects of stimulus alternation, repetition and response requirements on event-related potentials to patterned visual stimuli.

Event-related potentials (ERPs) were recorded to square-pattern stimuli presented either to the upper or the lower half of the visual field. In the Same task the subjects had to respond to the fifth stimulus of a microsequence of stimuli that appeared on the same half field, whereas in the Different task the target stimulus was the alternation of stimulus location after a microsequence of four stimuli to the same half field. The pattern-specific CII component (a negative wave to lower half-field stimulation with 100 ms latency) appeared to be insensitive to task variables. N1 increased to the uncertain alternations of stimulus location. An N2 component with temporal maximum emerged to Nogo stimuli (to the fifth stimulus in the same location in the Different task and the alternation after four identical stimuli in the Same task). An anterior N2 was characteristic to the Nogo stimuli of the Different task. P3 latency was longer, and it had more anterior distribution to the Nogo stimuli.

Adolescent↗
PubMed1992

Age and inter-stimulus interval effects on event-related potentials to frequent and infrequent auditory stimuli.

The aim of this study was to investigate aging effects on non-attended changes of auditory stimulation, by using psychophysiological methods. Event-related potentials (ERPs) were recorded to frequent (standard; 950 Hz, p = 0.9) and infrequent (deviant; 1045 Hz, p = 0.1) auditory stimuli in older (mean age = 60.8 years) and younger (mean age = 21.3 years) subjects. In various blocks the inter-stimulus interval (ISI) was either 800, 2400 or 7200 ms. During the experimental sessions the subjects read books, and ignored the auditory stimuli. As a function of ISI, the amplitude of the N1 and the amplitude and latency of the P2 increased. The P2 amplitude was larger in the younger group. In the 120-180 ms latency range the deviant stimuli elicited more negative ERPs (mismatch negativity, MMN) than the standard stimuli. The amplitude of the MMN did not change as a function of ISI. MMN was larger in the younger group. Thus the younger subjects were more sensitive to the deviant stimuli. In the younger group, at the two shorter ISIs, the MMN was followed by a positive wave (P3a). The emergence of this component is an indication of the increased activity of the orienting system in the younger subjects, in comparison to the older age group.

Acoustic Stimulation↗
PubMed1992

Event-related potentials and the identification of deviant visual stimuli.

The effects of deviant visual stimuli on event-related potentials were investigated in a counting task (Experiment 1) and in a reaction time task (Experiment 2). In Experiment 2 the interstimulus interval was either short or long (340 vs. 1020 ms). The stimuli (two angles within a frame) were frequent (Standard) or deviant (differing from the Standard either in the orientation of the two angles, or in the thickness of the frame, or in both of these features). In various conditions the target stimuli were defined by one of the deviant features or by the conjunction of these features. Subjects were more accurate in the counting task, and the reaction time was shortest when the target feature was the deviant angle orientation. Performance was lowest for the conjunction of the deviant features. The deviant angle orientation elicited a posterior negative wave in the 140-180 ms range. As the interstimulus interval increased, the magnitude of this component decreased. All stimuli with relevant (attended) deviant features elicited another posterior negative wave in the 180-260 ms range, as well as an anterior positivity with similar latency. When the interstimulus interval was short, and the only target was the Conjunction Deviant, the summed occipital activity to the relevant features of deviant nontarget stimuli was larger than the negativity to the Conjunction Deviant. Target stimuli elicited late positive waves, which were sometimes preceded by central negativity.

Adolescent↗
PubMed1991

Event-related potentials to irrelevant deviant motion of visual shapes.

Event-related potentials to visual shapes moving across the visual field were recorded from 10 subjects. The subjects had to respond to the appearance of one of the shapes, while other shapes were irrelevant. On the periphery some of the shapes changed their orientation or their form. Sometimes the direction of movement was different from the standard direction. Subjects did not detect the changes of the pattern on the visual periphery, and the ERPs to these non-detected deviants were identical to the ERPs to the standard stimuli. Six subjects detected the irrelevant direction of movement. In these subjects the deviant direction of motion elicited a fronto-central positive wave (P3s) with 322 ms mean latency. There was no such sharp positive peak in the four subjects who did not detect the deviant direction of movement. Unlike the non-target stimuli, the targets elicited a large positive wave (P3b) with 530 ms mean latency.

Adult↗