Biology subjects

Srokova, S.

Publications and source records attributed to Srokova, S..

12 recordsLinked to original sources

bioRxiv2026

Encoding-related fMRI BOLD activity predicts subsequent memory for studied scenes, but not subsequent identification of perceptually similar lures.

Pattern separation is widely regarded as a hippocampally mediated process that reduces interference between memories of similar experiences. Performance on the Mnemonic Similarity Task (MST), where the requirement is to discriminate between studied items (targets) and perceptually similar lures, is commonly held to depend on pattern separation. Specifically, it has been proposed that similar lure identification is supported by a recall-to-reject strategy, whereby lures are identified as a result of the retrieval of the corresponding studied item. According to this proposal, therefore, the encoding operations that support successful target recollection and successful lure identification should be closely similar, since both mnemonic judgments depend upon subsequent recollection of the study item. Here, using fMRI, we examined this prediction. In samples of cognitively healthy young and older adults, we employed a three-choice MST (target/lure/new) with scene and object images as test items. Using ROI-based univariate and multivoxel analyses, we assessed whether encoding-related activity was predictive of the identification of target and similar lure items on the subsequent memory test. The activity elicited by scene images predicted memory performance for subsequently presented targets but not for corresponding similar lures, contrary to the recall-to-reject hypothesis. No effects could be identified for either class of object test items. The magnitude of the encoding effects for the scene targets was age-invariant, and, moreover, the univariate scene SMEs demonstrated a robust, age-invariant association with the target-lure discriminability metric. HighlightsO_LIEncoding fMRI activity predicted scene recognition but not lure discrimination. C_LIO_LIEncoding-related fMRI effects showed no age-related differences. C_LIO_LIEncoding fMRI effects for scenes predicted mnemonic discrimination performance. C_LIO_LINo encoding-related fMRI effects were detected for objects. C_LI

neuroscience↗

bioRxiv2026

Category-selective functional connectivity during episodic encoding and retrieval in younger and older adults

Regions within ventral occipito-temporal cortex exhibit category-selective BOLD responses during episodic encoding and retrieval of visual information. How these regions interact with other brain areas during successful encoding and retrieval, and whether these interactions relate to memory performance, remains unclear. The present study examined category-selective functional connectivity using psychophysiological interaction (PPI) analyses in younger and older adults during the encoding and retrieval of word-image associations. Seed regions comprised three scene-selective regions - the parahippocampal place area, medial place area, and occipital place area - and one object-selective region, the lateral occipital complex (LOC). During encoding, scene-selective regions exhibited greater connectivity with posterior occipital and occipitotemporal regions during scene relative to object encoding, whereas the LOC exhibited less extensive connectivity with similar posterior regions during object encoding. During retrieval, both scene- and object-selective regions demonstrated increased connectivity with left lateral prefrontal and parietal cortices during the retrieval of their preferred category. Age differences in scene-selective connectivity were evident at both phases. Moreover, associations between source memory performance and scene-selective connectivity were significant only in younger adults. These findings suggest that scene- and object-selective regions exhibit convergent patterns of functional connectivity during encoding and retrieval which, for scenes, vary with age.

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bioRxiv2026

Age-related differences in spatial memory occur alongside reduced visual fMRI BOLD but preserved viewpoint-specific scene representations

Current evidence suggests that older adults perform worse at tasks involving spatial memory and navigation, yet the underlying reasons remain unclear. Here, we tested the hypothesis that age-related declines in spatial memory stem from difficulties in recognizing spatial environments from rotated perspectives. Young and older adults underwent fMRI as they encoded virtual scenes which were later viewed either from the same or rotated perspective. Older adults were worse at identifying changes in these scenes, although the age effect was equally robust across perspective conditions. Neural specificity of scene representations was examined with the phenomenon of fMRI repetition adaptation. We predicted that young adults would show significant fMRI adaptation to the same but not rotated perspective, indicative of intact viewpoint specificity, while older adults show would adaptation effects to both. While analyses of raw fMRI BOLD produced results consistent with these predictions, follow-up analyses revealed a general attenuation of activity in older adults across both perspective conditions. Additionally, although older adults showed both lower fMRI BOLD and worse spatial memory, lower trial-wise BOLD was associated with better performance independent of age. This suggests that the variance associated with fMRI adaptation is reflective of two independent sources of variance: age and cognition. Our results suggest that age differences in spatial memory may manifest due to cognitive and neural factors that are shared across same and rotated perspectives, and thus they cannot be explained by a selective deficit in allocentric (viewpoint-independent) processing. Significance StatementIncreasing age is often associated with reduced spatial memory and navigation. Prior research suggests that age differences in spatial memory could be exacerbated by changes in perspective, possibly due to increased difficulties in the ability to construct allocentric (viewpoint-independent) representations from previously encoded egocentric perspectives. Here, we demonstrate that older adults are equally disadvantaged when recognizing layouts across same and rotated perspectives. FMRI analyses indicate that older age is associated with reduced fMRI BOLD in higher-level visual cortex across both perspective conditions, as opposed to altered specificity of perspective coding. Consequently, the present study challenges the notion that aging is associated with a selective decline in allocentric spatial memory and instead supports a more general age-related difficulty with scene processing.

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bioRxiv2025

Retrieval-related eye movements are predictive of memory precision

Eye movements are predictive of successful episodic memory encoding and retrieval, but it is unclear whether they reflect the precision of retrieved memory content. Here, we examined relationships between eye fixations, memory precision and fMRI BOLD activity. At study, participants were presented with object images, each placed at a random location on an invisible circle. At test, both studied and new images were presented. Participants were instructed to make a covert recognition memory judgment to each image, recall and then signal its studied location, guessing if necessary. Simultaneous fMRI and eye-tracking data were acquired during the test phase. For correctly recognized images, the trial-wise angular distance between the studied and reported locations was fitted to a two-component mixture model. Based on the model-derived parameters, correctly recognized images were categorized as those associated with successful location retrieval (location hits) or guesses. Location hits were further divided into high- and low precision trials. At retrieval, fixations predicted both successful retrieval and the precision of the retrieved location memory. Additionally, across-trial fixation patterns were more similar for location hits than for guesses, and for high- than for low-precision trials. The association between retrieval success and eye fixation precision was evident across almost the entire recall phase, whereas memory precision effects emerged around 1-1.5s after image onset. Fixation precision and fixation pattern similarity each predicted trial-wise memory precision independently of hippocampal BOLD activity, which also predicted precision. These findings suggest that eye fixations during retrieval track the fidelity of mnemonic content.

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bioRxiv2025

Moderating effects of cortical thickness, volume, and memory performance on age differences in neural reinstatement of scene information

The strength of neural reinstatement, a correlate of episodic memory retrieval, reportedly reflects the amount and fidelity of mnemonic content and is weaker in older than younger adults, especially for scene memoranda. Based on evidence that age-related declines in cortical thickness and volume contribute to age-related cognitive decline, we analyzed fMRI data acquired from healthy young and older adults to examine relationships between cortical thickness, cortical volume, age, and scene-related reinstatement in three cortical regions implicated in scene processing: the parahippocampal place area (PPA), medial place area (MPA), and occipital place area (OPA). A reinstatement index was estimated from fMRI data collected during tests of source memory for scene images, and multiple regression analyses were employed to examine the effects of the variables of interest on scene reinstatement. There were robust age differences in reinstatement, cortical thickness, and cortical volume. In the PPA and MPA, cortical volume fully mediated the effects of age on reinstatement. Additionally, PPA reinstatement strength predicted source memory performance independently of cortical volume or age. These findings suggest that age differences in scene reinstatement are mediated by cortical volume and that memory performance and cortical volume are associated with unique components of variance in reinstatement strength.

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bioRxiv2025

The relationship between neural differentiation and exploratory eye movements in healthy young and older adults

Age-related neural dedifferentiation, characterized by lower selectivity of neural responses in the high-level sensory cortex, is thought to be a major contributor to age-related cognitive decline. However, the mechanisms that underlie dedifferentiation are poorly understood. Building on prior evidence that exploratory eye movements differ with age, we investigated the role that eye movement might play in age-related declines in neural selectivity. Healthy young and older adults of both sexes underwent fMRI with simultaneous eye-tracking as they viewed words paired with images of scenes and objects prior to a memory test. Consistent with numerous prior reports, multivoxel pattern similarity analysis (PSA) of the fMRI data revealed age-related neural dedifferentiation in scene-selective, but not object-selective cortex. Eye movements, operationalized as the number of gaze fixations made during stimulus viewing, were elevated in older adults. Analyses examining the relationship between trial-wise estimates of neural selectivity and fixation count revealed an age-invariant positive relationship in the object-selective lateral occipital complex. However, this association was found to be age-dependent in scene-selective cortex, such that there was a robust positive relationship between scene selectivity and fixation count in young, but not older adults. Lastly, scene-related selectivity in the parahippocampal place area predicted subsequent memory performance independently of age group and fixation counts at encoding. These findings suggest that age-related neural dedifferentiation in scene-selective cortex may relate to declines in the functional specialization of exploratory eye movements during scene viewing. Significance statementHealthy aging is associated with lower neural selectivity in brain regions responsive to distinct categories of perceptual stimuli. This phenomenon is most commonly observed in scene-selective cortex, although the underlying reasons remain unknown. Here, we report that trial-wise estimates of neural selectivity positively covary with the number of eye movements made during stimulus viewing. However, we also report an age-related breakdown in this relationship within scene-selective cortex, consistent with the notion that age differences in eye movements and neural selectivity reflect deficits in the extraction and binding of visual information into memory. The present findings highlight the complex interactions that occur between age, neural selectivity and eye movements, and provide novel insights into neural and behavioral mechanisms underlying cognitive aging.

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bioRxiv2025

Effects of age in the strategic control of recollected content as reflected by modulation of scene reinstatement

A previous study employing fMRI measures of retrieval-related cortical reinstatement reported that young, but not older, adults employ retrieval gating to attenuate aspects of an episodic memory that are irrelevant to the retrieval goal. We examined whether the weak memories of the older adults in that study rendered goal-irrelevant memories insufficiently intrusive to motivate retrieval gating. Young and older participants studied words superimposed on rural or urban scenes, or on pixelated backgrounds. To strengthen memory for background information, word-image pairs were studied twice, initially centrally, and then in one of three locations. During scanning, one retrieval test probed memory for the test words studied backgrounds and another test assessed memory for their location. Background memory performance was markedly higher than in the prior study. Retrieval gating was examined in two scene-selective regions of interest, the parahippocampal place area (PPA) and the medial place area (MPA). In the background task, robust retrieval-related scene reinstatement effects were identified in both age groups. These effects were attenuated ( gated) in the location task in the young age group only, replicating the prior finding. The results did not differ when the two groups were sub-sampled to match strength of scene reinstatement when scene information was goal relevant. The findings indicate that older adults failure to gate goal-irrelevant scene information does not reflect age differences in memory strength and may instead reflect an age-related decline in top-down inhibitory control.

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bioRxiv2023

Dissociative effects of age on neural differentiation at the category and item level

Increasing age is associated with age-related neural dedifferentiation, a reduction in the selectivity of neural representations which has been proposed to contribute to cognitive decline in older age. Recent findings indicate that when operationalized in terms of selectivity for different perceptual categories, age-related neural dedifferentiation, and the apparent age-invariant association of neural selectivity with cognitive performance, are largely restricted to the cortical regions typically recruited during scene processing. It is currently unknown whether this category-level dissociation extends to metrics of neural selectivity defined at the level of individual stimulus items. Here, we examined neural selectivity at the category and item levels using multivoxel pattern similarity analysis (PSA) of fMRI data. Healthy young and older male and female adults viewed images of objects and scenes. Some items were presented singly, while others were either repeated or followed by a similar lure. Consistent with recent findings, category-level PSA revealed robustly lower differentiation in older than younger adults in scene-selective, but not object-selective, cortical regions. By contrast, at the item level, robust age-related declines in neural differentiation were evident for both stimulus categories. Moreover, we identified an age-invariant association between category-level scene-selectivity in the parahippocampal place area and subsequent memory performance, but no such association was evident for item-level metrics. Lastly, category and item-level neural metrics were uncorrelated. Thus, the present findings suggest that age-related category- and item-level dedifferentiation depend on distinct neural mechanisms. Significance StatementCognitive aging is associated with a decline in the selectivity of the neural responses within cortical regions that respond differentially to distinct perceptual categories (age-related neural dedifferentiation). However, prior research indicates that while scene-related selectivity is reduced in older age and is correlated with cognitive performance independently of age, selectivity for object stimuli is typically not moderated by age or memory performance. Here, we demonstrate that neural dedifferentiation is evident for both scene and object exemplars when it is defined in terms of the specificity of neural representations at the level of individual exemplars. These findings suggest that neural selectivity metrics for stimulus categories and for individual stimulus items depend on different neural mechanisms.

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bioRxiv2022

Cortical thickness, gray matter volume and cognitive performance: a cross-sectional study of the moderating effects of age on their inter-relationships

In a sample comprising younger, middle-aged and older cognitively healthy adults (N = 375), we examined associations between mean cortical thickness, gray matter volume (GMV) and performance in four cognitive domains - memory, speed, fluency and crystallized intelligence. In almost all cases, the associations were moderated significantly by age, with the strongest associations in the older age group. An exception to this pattern was identified in a younger adult sub-group aged less than 23 yrs, when a negative association between cognitive performance and cortical thickness was identified. Other than for speed, all associations between structural metrics and performance in specific cognitive domains were fully mediated by mean cognitive ability. Cortical thickness and GMV explained unique fractions of the variance in mean cognitive ability, speed and fluency. In no case, however, did the amount of variance jointly explained by the two metrics exceed 7% of the total variance. These findings suggest that cortical thickness and GMV are distinct correlates of domain-general cognitive ability, that the strength and, for cortical thickness, the direction of these associations is moderated by age, and that these structural metrics offer only limited insights into the determinants of individual differences in cognitive performance across the adult lifespan.

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bioRxiv2021

The Retrieval-related Anterior shift is Moderated by Age and Correlates with Memory Performance

Recent research suggests that episodic memory is associated with systematic differences in the localization of neural activity observed during memory encoding and retrieval. The retrieval-related anterior shift is a phenomenon whereby the retrieval of a stimulus event (e.g., a scene image) is associated with a peak neural response which is localized more anteriorly than the response elicited when the stimulus is experienced directly. Here, we examine whether the magnitude of the anterior shift, i.e., the distance between encoding- and retrieval-related response peaks, is moderated by age, and also whether the shift is associated with memory performance. Younger and older human subjects of both sexes underwent fMRI as they completed encoding and retrieval tasks on word-face and word-scene pairs. We localized peak scene- and face-selectivity for each individual participant within the face-selective precuneus (PCU) and in three scene-selective (parahippocampal place area [PPA], medial place area [MPA], occipital place area [OPA]) regions of interest (ROIs). In line with recent findings, we identified an anterior shift in PPA and OPA in both age groups and, in older adults only, in MPA and PCU also. Of importance, the magnitude of the anterior shift was larger in older than in younger adults. The shift within the PPA exhibited an age-invariant across-participant negative correlation with source memory performance, such that a smaller displacement between encoding- and retrieval-related neural activity was associated with better performance. These findings provide novel insights into the functional significance of the anterior shift, especially in relation to memory decline in older age. Significance StatementCognitive aging is associated with reduced ability to retrieve precise details of previously experienced events. The retrieval-related anterior shift is a phenomenon in which category-selective cortical activity at retrieval is localized anterior to the peak activity at encoding. The shift is thought to reflect a bias at retrieval in favor of semantic and abstract information at the expense of low-level perceptual detail. Here, we report that the anterior shift is exaggerated in older relative to younger adults, and we demonstrate that a large shift in the parahippocampal place area is associated with poorer memory performance. These findings suggest that the shift is sensitive to increasing age and that it is moderated by the quality and content of the retrieved episode.

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bioRxiv2020

Effects of age on goal-dependent modulation of episodic memory retrieval

Retrieval gating refers to the ability to modulate the retrieval of features of a single memory episode according to behavioral goals. Recent findings demonstrate that younger adults engage retrieval gating by attenuating the representation of task-irrelevant features of an episode. Here, we examine whether retrieval gating varies with age. Younger and older adults incidentally encoded words superimposed over scenes or scrambled backgrounds that were displayed in one of three spatial locations. Participants subsequently underwent fMRI as they completed two memory tasks: the background task, which tested memory for the words background, and the location task, testing memory for the words location. Employing univariate and multivariate approaches, we demonstrated that younger, but not older adults, exhibited attenuated reinstatement of scene information when it was goal-irrelevant (during the location task). Additionally, in younger adults only, the strength of scene reinstatement in the parahippocampal place area during the background task was related to item and source memory performance. Together, these findings point to an age-related decline in the ability to engage retrieval gating.

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bioRxiv2020

Neural differentiation is moderated by age in scene- but not face-selective cortical regions

The aging brain is characterized by neural dedifferentiation - an apparent decrease in the functional selectivity of category-selective cortical regions. Age-related reductions in neural differentiation have been proposed to play a causal role in cognitive aging. Recent findings suggest, however, that age-related dedifferentiation is not equally evident for all stimulus categories and, additionally, that the relationship between neural differentiation and cognitive performance is not moderated by age. In light of these findings, in the present experiment younger and older human adults (males and females) underwent fMRI as they studied words paired with images of scenes or faces prior to a subsequent memory task. Neural selectivity was measured in two scene-selective (parahippocampal place area and retrosplenial cortex) and two face-selective (fusiform and occipital face areas) regions of interest using both a univariate differentiation index and multivoxel pattern similarity analysis. Both methods provided highly convergent results which revealed evidence of age-related reductions in neural dedifferentiation in scene-selective but not face-selective cortical regions. Additionally, neural differentiation in the parahippocampal place area demonstrated a positive, age-invariant relationship with subsequent source memory performance (recall of the image category paired with each recognized test word). These findings extend prior findings suggesting that age-related neural dedifferentiation is not a ubiquitous phenomenon, and that the specificity of neural responses to scenes is predictive subsequent memory performance independently of age. Significance StatementIncreasing age is associated with reduced neural specificity in cortical regions that are selectively responsive to a given perceptual stimulus category (age-related neural dedifferentiation), a phenomenon which has been proposed to contribute to cognitive aging. Recent findings reveal that age-related neural dedifferentiation is not present for all types of visual stimulus categories, and the factors which determine when the phenomenon arises remain unclear. Here, we demonstrate that scene- but not face-selective cortical regions exhibit age-related neural dedifferentiation during an attentionally-demanding task. Additionally, we report that higher neural selectivity in the scene-selective parahippocampal place area is associated with better memory performance after controlling for variance associated with age group, adding to evidence that neural differentiation impacts cognition across the adult lifespan.

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