Biology subjects

Czigler, I.

Publications and source records attributed to Czigler, I..

6 recordsLinked to original sources

bioRxiv2025

Deficient processing of regularity violations during visuospatial neglect: a visual mismatch negativity study

Visuospatial neglect (VSN) after right-hemisphere stroke causes reduced engagement with left-sided stimuli, but how VSN affects automatic processes, i.e. the registration of regularities and regularity violations is still equivocal. This study investigated these processes using event-related potential components C1, C2/N1, and the visual mismatch negativity (vMMN), and how they differ in VSN compared to stroke and healthy controls, and their changes with time and rehabilitation. We applied a passive oddball paradigm, where diamond patterns periodically disappeared (OFF events) and reappeared (ON events) on the lower left and right sides, creating two simultaneous but independent sequences with standard and deviant events. The study included a VSN group (N=17, M=53.88{+/-}0.28 yrs); stroke patients (N=16, M = 56.81 {+/-} 13.26 yrs); and healthy participants (N=17, M=53.89{+/-}10.79 yrs). The VSN group underwent measurements three times: pre- and post-rehabilitation, and at a 4-month follow-up. Our results show that the C1 component emerged reliably in healthy participants and as a tendency in stroke controls, but not in VSN at any measurement point. The C2/N1 component emerged for all events without group differences. VSN patients showed no reliable vMMN, while it emerged in stroke patients for left-sided OFF events. Healthy controls showed vMMN in every condition. Our results suggest that both stroke and VSN impair the automatic detection of regularity violations, but VSN does so in a more substantial way, and this deficit does not improve with time or rehabilitation. Furthermore, the missing C1 component in VSN may indicate an early-stage deficiency even in visual processing.

neuroscience↗

bioRxiv2025

Revisiting object contextual cueing: A replication study on implicit learning

Object contextual cueing is an implicit learning paradigm in which the repeated co-occurrence of certain objects facilitates target detection, even when their spatial arrangement varies. In two experiments - where participants performed a visual search task in which the target was accompanied by either consistently repeated or randomly varying distractors - we attempted to replicate Chun and Jiangs (1999) study. In Experiment 1 (N = 25, M = 20.8 years), although participants became faster and more accurate over time, no significant difference emerged between repeated and new configurations. Thus, using the same experimental design, we were unable to replicate the object contextual cueing effect. In Experiment 2, we tested whether search strategy influences the effect by instructing one group to adopt an active search strategy and another to use a passive one (N = 20 per group, M = 21.8 and 21.7 years, respectively; active: actively search for the target, passive: let the unique item pop out). However, the manipulation had no effect: the contextual cueing effect did not emerge in either group. Importantly, within each group we observed substantial individual differences - some participants showed a facilitation effect, others no effect, and some even showed a reverse pattern. These findings suggest that object contextual cueing may not be a robust or universal phenomenon and may instead depend on individual cognitive styles or learning tendencies. Highlights- Replication of Chun and Jiangs (1999) object cueing study was unsuccessful. - Active vs. passive strategy instructions had no effect on object contextual cueing. - Large individual differences emerged in the contextual cueing effect.

neuroscience↗

bioRxiv2025

Automatic pairing of complex stimuli in younger and older adults: An event-related potential study

Contextual information can influence object perception, even when it is irrelevant to the task. When two unrelated stimuli frequently occur in close temporal succession, they may become associated. This process might be stronger in older adults due to age-related decline in inhibitory control, leading to deeper processing of irrelevant context. Automatic associations and their violations can be studied using visual mismatch negativity (vMMN), an event-related potential component reflecting the detection of violations of regularity in unattended stimuli. In our study, younger (n=18, M=21.2 {+/-} 2.1 yrs) and older (n=17, M=69.8 {+/-} 2.8 yrs) adults viewed pairs of images presented in succession: a scene (forest or street) followed by an emotional face (happy or angry). One scene-emotional face combination occurred frequently, the other rarely, forming a contextual oddball sequence. All individual stimuli appeared equally often. Participants performed an unrelated colour-change detection task, ensuring that the scene-emotional face pairs were unattended. We expected a vMMN to the emotional face in rare pairings, especially in older adults if they formed stronger associations. A control oddball condition with only emotional faces verified automatic emotion discrimination. In the control condition, vMMN emerged for both deviant emotions (in various ranges within the 94-276 ms post-stimulus time window). However, no vMMN was observed in the scene-emotional face pair condition. Instead, younger adults showed an early posterior positivity (90-161 ms) to rare pairings, while older adults exhibited a later negativity (356-384 ms). These results suggest that task-irrelevant, thematically unrelated visual events can become associated through temporal proximity. However, violations of these associations evoke neural responses distinct from vMMN and vary across age groups, with older adults relying on later, potentially semantic-related mechanisms rather than early visual processes to detect the regularity.

neuroscience↗

bioRxiv2025

Cognitive training effects are shaped more by individual brain dynamics than age - Evidence from younger and older women

Given the well-established structural and functional changes in the aging brain, it is widely assumed that cognitive aging is primarily driven by robust group-level differences between young and older adults. However, our individual-level EEG functional connectivity analysis challenges this notion. We investigated the impact of cognitive training on functional brain connectivity using task-switching paradigms in 39 younger (18-25 years) and 40 older (60-75 years) women. Participants were randomly assigned to either a training group, which completed eight individualized one-hour cognitive training sessions, or a no-contact control group. EEG was recorded at both pre- and post-training sessions across three task-switching paradigms (trained and near-transfer versions). Unique functional connectivity of different sources of variation was examined by calculating how much variance was shared across stable traits (e.g., individual, age, and common factors), or dynamic states (e.g., task and training effects). Our results revealed that age accounted for only a modest proportion of variance, whereas self-similarity was a dominant factor - particularly in older adults. Similarly, group-level training effects were small but strongly modulated by individual neural profiles, suggesting person-specific trajectories. Participants recruited distinct neural networks across tasks, and even within the same task engaged unique, individual-specific network configurations, reflecting personalised brain adaptations to cognitive demands. Importantly, older adults displayed a shift from common to individual network patterns, consistent with increased neural specialization and compensatory mechanisms. These findings underscore the importance of moving beyond group-level contrasts toward models that capture the complexity of individual brain dynamics in cognitive aging and training responsiveness. Significance StatementWhy do cognitive training programs work for some individuals but not for others? And is aging really the main factor driving changes in brain function? Using individual-level EEG functional connectivity analyses, we show that individual differences - not chronological age, task, or training - are the primary drivers of similarity in brain connectomes. While training effects are modest on average, their impact strongly depends on the individuals unique neural profile. Older adults, in particular, rely more on personalized brain network configurations. These results help explain why cognitive training studies often yield inconsistent findings and point toward a more individualized approach to understanding and enhancing brain function across the lifespan.

neuroscience↗

bioRxiv2024

Age-related differences in working memory subprocesses decomposed by the reference-back paradigm

We used a data-driven approach to study the electrophysiological correlates of the working memory subprocesses revealed by the reference-back paradigm. In the absence of prior research, we focused on how aging affects the four subprocesses: updating, substitution, gate opening, and gate closing. We conducted our experiment with 25 younger adults (M=20.17{+/-}1.47) and 23 older adults (M=67.35{+/-}4.01) using the reference-back paradigm. Significant reaction time costs were observed for all four subprocesses, but age-related differences were found only in substitution, which was larger in older than younger adults, indicating it as being the most vulnerable subprocess in aging. Using difference waves, we identified event-related potential components that characterize the subprocesses we studied. Regarding updating: three occipital negativities between 80-180 ms, 300-400 ms, and 400-1,000 ms were observed, with only the latter range showing age group differences. Source analysis showed larger activity differences in the right frontal and temporal areas for younger adults. Regarding substitution: a frontal positivity between 250-600 ms emerged in younger adults, while a posterior positivity between 550-750 ms was found in older adults indicating different underlying processes supported by sLORETA results. Regarding gate opening: three parieto-occipital components were identified: a negativity between 150-250 ms, a positivity between 300-500 ms, and a positivity between 500-700 ms, all showing age-related differences. Regarding gate closing: we found an occipital negativity between 150-300 ms and a frontal positivity between 300-600 ms, neither of which changed between the age groups. From our findings, we conclude that the process of protecting information (gate closing) remains stable with age, despite older adults sensitivity to interference. Conversely, gate opening is sensitive to age-related changes, likely to be resulting in different brain activity patterns during substitution being the updating of working memory with new information.

neuroscience↗

bioRxiv2018

Visual mismatch negativity to disappearing parts of objects and textures

Visual mismatch negativity (vMMN), an event-related signature of automatic detection of events violating sequential regularities is traditionally investigated to the onset of frequent (standard) and rare (deviant) events. In a previous study [4] we obtained vMMN to vanishing parts of continuously presented objects (diamonds with diagonals), and we concluded that the offset-related vMMN is a model of sensitivity to irregular partial occlusion of objects. In the present study we replicated the previous results, but to test the object-related interpretation we applied a new condition with a set of separate visual stimuli: a texture of bars with two orientations. In the texture condition (offset of bars with irregular vs. regular orientation) we obtained vMMN, showing that the continuous presence of objects is unnecessary for offset-related vMMN. However, unlike in the object-related condition, reappearance of the previously vanishing lines also elicited vMMN. In a formal way reappearance of the stimuli is an event with probability 1.0, and according to the results, object condition reappearance is an expected event. However, offset and onset of texture elements seems to be treated separately by the system underlying vMMN. As an advantage of the present method, the whole stimulus set during the inter-stimulus interval saturates the visual structures sensitive to stimulus input. Accordingly, the offset-related vMMN is less sensitive to low-level adaptation difference between the deviant and standard stimuli.

neuroscience↗