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Biomedical subjects

Gaia Scerif

Publications and source records attributed to Gaia Scerif.

6 recordsLinked to original sources
PubMed2006

Context modulates early stimulus processing when resolving stimulus-response conflict.

When responding to stimuli in our environment, the presence of multiple items associated with task-relevant responses affects both ongoing response selection and subsequent behavior. Computational modeling of conflict monitoring and neuroimaging data predict that the recent context of response competition will bias the selection of certain stimuli over others very early in the processing stream through increased focal spatial attention. We used high-density EEG to test this hypothesis and to investigate the contextual effects on nonspatial, early stimulus processing in a modified flanker task. Subjects were required to respond to a central arrow and to ignore potentially conflicting information from flanking arrows in trials preceded by a series of either compatible or incompatible trials. On some trials, we presented the flanking arrows in the absence of the central target. The visual P1 component was selectively enhanced only for incompatible trials when preceded by incompatible ones, suggesting that contextual effects depend on feature-based processing, and not only simple enhancement of the target location. Context effects also occurred on no-target trials as evidenced by an enhanced early-evoked response when they followed compatible compared to incompatible trials, suggesting that spatial attention was also modulated by recent context. These results support a multi-componential account of spatial and nonspatial attention and they suggest that contextually driven cognitive control mechanisms can operate on specific stimulus features at extremely early stages of processing within stimulus-response conflict tasks.

Adult↗
PubMed2005

The dawn of cognitive genetics? Crucial developmental caveats.

Attempts to bridge genetics and cognition are rapidly coming to the forefront of cognitive neuroscience. It is therefore crucial to evaluate the current state of knowledge about disorders of known genetic origin as a way of assessing whether, and if so how, links between genotype and cognitive phenotype can be drawn, however indirect these links might be. We review recent empirical findings from research on genetic disorders at three levels of description--cognitive, neural systems, and cellular--that caution against simple genotype-phenotype mappings at all levels. Most importantly, interdisciplinary efforts to integrate human genetics and cognition will need to operationalize the mechanisms driving both typical and atypical developmental processes over time.

Brain↗
PubMed2005

To look or not to look? Typical and atypical development of oculomotor control.

The ability to inhibit saccades toward suddenly appearing peripheral stimuli (prosaccades) and direct them to contralateral locations instead (antisaccades) is a crucial marker of eye movement control. Typically developing infants as young as 4-month-olds can learn to inhibit reflexive saccades to peripheral stimuli, but they do not produce antisaccades, whose development later in infancy and its underlying neural computations remain unexplored. Here we tested oculomotor control in typically developing toddlers and toddlers with fragile X syndrome (FXS), a disorder of known genetic origin that allows the investigation of the neuro-computational properties contributing to the development of saccadic control. Typically developing toddlers decreased looking toward peripheral cues that predicted contralateral rewards, whose appearance they anticipated. Furthermore, this correlated with age, indicating a gradual development of saccadic control. In contrast with the typical case, toddlers with FXS did not decrease their looks to peripheral onsets that predicted contralateral events. Importantly, the atypical pattern of performance was also evident in the elimination of the correlation with mental or chronological age found in controls. Taken together, the findings suggest that control of saccades and its developmental trajectory is atypical in toddlers with FXS, consistent with inhibitory deficits previously shown at later ages in this condition. Potential implications for the neural mechanisms underlying the typical and atypical development of oculomotor control are discussed.

Age Factors↗
PubMed2004

Visual search in typically developing toddlers and toddlers with Fragile X or Williams syndrome.

Visual selective attention is the ability to attend to relevant visual information and ignore irrelevant stimuli. Little is known about its typical and atypical development in early childhood Experiment 1 investigates typically developing toddlers' visual search for multiple targets on a touch-screen. Time to hit a target, distance between successively touched items, accuracy and error types revealed changes in 2- and 3-year-olds' vulnerability to manipulations of the search display. Experiment 2 examined search performance by toddlers with Fragile X syndrome (FXS) or Williams syndrome (WS). Both of these groups produced equivalent mean time and distance per touch as typically developing toddlers matched by chronological or mental age; but both produced a larger number of errors. Toddlers with WS confused distractors with targets more than the other groups; while toddlers with FXS perseverated on previously found targets. These findings provide information on how visual search typically develops in toddlers, and reveal distinct search deficits for atypically developing toddlers.

Attention↗
PubMed2002

Different approaches to relating genotype to phenotype in developmental disorders.

In this article, we discuss the complex problem of relating genotype to phenotype and challenge the simple mapping of genes to higher level cognitive modules. We examine various methods that have been used to investigate this relation including quantitative genetics, molecular genetics, animal models, and in-depth psychological and computational studies of developmental disorders. Both single gene and multiple gene disorders indicate that the relationship between genotype and phenotype is very indirect and that, rather than identifying mere snapshots of developmental outcomes, the process of ontogenetic development itself must be taken into account.

Animals↗