Publications by authors named "Vasiliki Folia"

14 Publications

  • Page 1 of 1

Pesticides, cognitive functions and dementia: A review.

Toxicol Lett 2020 Jun 4;326:31-51. Epub 2020 Mar 4.

Department of Neurology, Laboratory of Neurogenetics, University Hospital of Larissa, Greece; Faculty of Medicine, School of Health Sciences, University of Thessaly, Larissa, Greece. Electronic address:

Pesticides are widely-used chemicals commonly applied in agriculture for the protection of crops from pests. Depending on the class of pesticides, the specific substances may have a specific set of adverse effects on humans, especially in cases of acute poisoning. In past years, evidence regarding sequelae of chronic, low-level exposure has been accumulating. Cognitive impairment and dementia heavily affect a person's quality of life and scientific data has been hinting towards an association between them and antecedent chronic pesticide exposure. Here, we reviewed animal and human studies exploring the association between pesticide exposure, cognition and dementia. Additionally, we present potential mechanisms through which pesticides may act neurotoxically and lead to neurodegeneration. Study designs rarely presented homogeneity and the estimation of the exposure to pesticides has been most frequently performed without measuring the synergic effects and the possible interactions between the toxicants within mixtures, and also overlooking low exposures to environmental toxicants. It is possible that a Real-Life Risk Simulation approach would represent a robust alternative for future studies, so that the safe exposure limits and the net risk that pesticides confer to impaired cognitive function can be examined. Previous studies that evaluated the effect of low dose chronic exposure to mixtures of pesticides and other chemicals intending to simulate real life exposure scenarios showed that hormetic neurobehavioral effects can appear after mixture exposure at doses considered safe for individual compounds and these effects can be exacerbated by a coexistence with specific conditions such as vitamin deficiency. However, there is an overall indication, derived from both epidemiologic and laboratory evidence, supporting an association between exposure to neurotoxic pesticides and cognitive dysfunction, dementia and Alzheimer's disease.
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http://dx.doi.org/10.1016/j.toxlet.2020.03.005DOI Listing
June 2020

Beneficial effect of computer-based multidomain cognitive training in patients with mild cognitive impairment.

Appl Neuropsychol Adult 2019 Dec 29:1-10. Epub 2019 Dec 29.

Department of Neurology, University Hospital of Larissa, Larissa, Greece.

The purpose of the present study was to explore the effects of computer-based multidomain cognitive training program on Greek patients with Mild Cognitive Impairment (MCI). Forty-six patients with MCI were randomly divided into two groups; (a) the training group, which received a computer-based multidomain cognitive training program with the use of the RehaCom software and (b) the control group, which underwent standard-clinical care. The duration of the computer-based training program was 15 weeks, administered twice a week for approximately one hour per session. Analysis of the baseline versus endpoint performance of each group demonstrated that in the control group delayed memory and executive function had deteriorated over the observation period of 15 weeks, while improvement was observed in the training group's performance on delayed memory, word recognition, Boston Naming Test (BNT), Clock Drawing Test (CDT), Semantic Fluency (SF), Trail Making Test-A (TMT-A) and Trail Making Test-B (TMT-B). Comparison between the two groups presented asignificant effect of the intervention for most cognitive domains. These findings are promising for the development of training methods designed to delay cognitive decline in patients with MCI, which is considered to be the prodromal stage of Alzheimer's Disease (AD).
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http://dx.doi.org/10.1080/23279095.2019.1692842DOI Listing
December 2019

Modality effects in implicit artificial grammar learning: An EEG study.

Brain Res 2018 05 21;1687:50-59. Epub 2018 Feb 21.

Center for Biomedical Research, University of Algarve, Faro, Portugal; Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.

Recently, it has been proposed that sequence learning engages a combination of modality-specific operating networks and modality-independent computational principles. In the present study, we compared the behavioural and EEG outcomes of implicit artificial grammar learning in the visual vs. auditory modality. We controlled for the influence of surface characteristics of sequences (Associative Chunk Strength), thus focusing on the strictly structural aspects of sequence learning, and we adapted the paradigms to compensate for known frailties of the visual modality compared to audition (temporal presentation, fast presentation rate). The behavioural outcomes were similar across modalities. Favouring the idea of modality-specificity, ERPs in response to grammar violations differed in topography and latency (earlier and more anterior component in the visual modality), and ERPs in response to surface features emerged only in the auditory modality. In favour of modality-independence, we observed three common functional properties in the late ERPs of the two grammars: both were free of interactions between structural and surface influences, both were more extended in a grammaticality classification test than in a preference classification test, and both correlated positively and strongly with theta event-related-synchronization during baseline testing. Our findings support the idea of modality-specificity combined with modality-independence, and suggest that memory for visual vs. auditory sequences may largely contribute to cross-modal differences.
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http://dx.doi.org/10.1016/j.brainres.2018.02.020DOI Listing
May 2018

Eye movements in implicit artificial grammar learning.

J Exp Psychol Learn Mem Cogn 2017 Sep 13;43(9):1387-1402. Epub 2017 Mar 13.

Psychology Department, Center for Biomedical Research, University of Algarve.

Artificial grammar learning (AGL) has been probed with forced-choice behavioral tests (active tests). Recent attempts to probe the outcomes of learning (implicitly acquired knowledge) with eye-movement responses (passive tests) have shown null results. However, these latter studies have not tested for sensitivity effects, for example, increased eye movements on a printed violation. In this study, we tested for sensitivity effects in AGL tests with (Experiment 1) and without (Experiment 2) concurrent active tests (preference- and grammaticality classification) in an eye-tracking experiment. Eye movements discriminated between sequence types in passive tests and more so in active tests. The eye-movement profile did not differ between preference and grammaticality classification, and it resembled sensitivity effects commonly observed in natural syntax processing. Our findings show that the outcomes of implicit structured sequence learning can be characterized in eye tracking. More specifically, whole trial measures (dwell time, number of fixations) showed robust AGL effects, whereas first-pass measures (first-fixation duration) did not. Furthermore, our findings strengthen the link between artificial and natural syntax processing, and they shed light on the factors that determine performance differences in preference and grammaticality classification tests. (PsycINFO Database Record
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http://dx.doi.org/10.1037/xlm0000350DOI Listing
September 2017

The P600 in Implicit Artificial Grammar Learning.

Cogn Sci 2017 01 23;41(1):137-157. Epub 2016 Feb 23.

Cognitive Neuroscience Research Group, Centre for Biomedical Research (CBMR), University of Algarve.

The suitability of the artificial grammar learning (AGL) paradigm to capture relevant aspects of the acquisition of linguistic structures has been empirically tested in a number of EEG studies. Some have shown a syntax-related P600 component, but it has not been ruled out that the AGL P600 effect is a response to surface features (e.g., subsequence familiarity) rather than the underlying syntax structure. Therefore, in this study, we controlled for the surface characteristics of the test sequences (associative chunk strength) and recorded the EEG before (baseline preference classification) and after (preference and grammaticality classification) exposure to a grammar. After exposure, a typical, centroparietal P600 effect was elicited by grammatical violations and not by unfamiliar subsequences, suggesting that the AGL P600 effect signals a response to structural irregularities. Moreover, preference and grammaticality classification showed a qualitatively similar ERP profile, strengthening the idea that the implicit structural mere-exposure paradigm in combination with preference classification is a suitable alternative to the traditional grammaticality classification test.
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http://dx.doi.org/10.1111/cogs.12343DOI Listing
January 2017

Implicit structured sequence learning: an fMRI study of the structural mere-exposure effect.

Front Psychol 2014 4;5:41. Epub 2014 Feb 4.

Neurobiology of Language, Max Planck Institute for Psycholinguistics Nijmegen, Netherlands ; Neurocognition of Language, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Nijmegen, Netherlands ; Cognitive Neuroscience Research Group, Department of Psychology, Institute of Biotechnology and Bioengineering, Centre for Molecular and Structural Biomedicine (CBME), Universidade do Algarve Faro, Portugal.

In this event-related fMRI study we investigated the effect of 5 days of implicit acquisition on preference classification by means of an artificial grammar learning (AGL) paradigm based on the structural mere-exposure effect and preference classification using a simple right-linear unification grammar. This allowed us to investigate implicit AGL in a proper learning design by including baseline measurements prior to grammar exposure. After 5 days of implicit acquisition, the fMRI results showed activations in a network of brain regions including the inferior frontal (centered on BA 44/45) and the medial prefrontal regions (centered on BA 8/32). Importantly, and central to this study, the inclusion of a naive preference fMRI baseline measurement allowed us to conclude that these fMRI findings were the intrinsic outcomes of the learning process itself and not a reflection of a preexisting functionality recruited during classification, independent of acquisition. Support for the implicit nature of the knowledge utilized during preference classification on day 5 come from the fact that the basal ganglia, associated with implicit procedural learning, were activated during classification, while the medial temporal lobe system, associated with explicit declarative memory, was consistently deactivated. Thus, preference classification in combination with structural mere-exposure can be used to investigate structural sequence processing (syntax) in unsupervised AGL paradigms with proper learning designs.
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http://dx.doi.org/10.3389/fpsyg.2014.00041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3912435PMC
February 2014

Sleep promotes the extraction of grammatical rules.

PLoS One 2013 5;8(6):e65046. Epub 2013 Jun 5.

Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.

Grammar acquisition is a high level cognitive function that requires the extraction of complex rules. While it has been proposed that offline time might benefit this type of rule extraction, this remains to be tested. Here, we addressed this question using an artificial grammar learning paradigm. During a short-term memory cover task, eighty-one human participants were exposed to letter sequences generated according to an unknown artificial grammar. Following a time delay of 15 min, 12 h (wake or sleep) or 24 h, participants classified novel test sequences as Grammatical or Non-Grammatical. Previous behavioral and functional neuroimaging work has shown that classification can be guided by two distinct underlying processes: (1) the holistic abstraction of the underlying grammar rules and (2) the detection of sequence chunks that appear at varying frequencies during exposure. Here, we show that classification performance improved after sleep. Moreover, this improvement was due to an enhancement of rule abstraction, while the effect of chunk frequency was unaltered by sleep. These findings suggest that sleep plays a critical role in extracting complex structure from separate but related items during integrative memory processing. Our findings stress the importance of alternating periods of learning with sleep in settings in which complex information must be acquired.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065046PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673983PMC
January 2014

The neuropharmacology of implicit learning.

Curr Neuropharmacol 2010 Dec;8(4):367-81

Max Planck Institute for Psycholinguistics, Nijmegen, the Netherlands.

Two decades of pharmacologic research on the human capacity to implicitly acquire knowledge as well as cognitive skills and procedures have yielded surprisingly few conclusive insights. We review the empirical literature of the neuropharmacology of implicit learning. We evaluate the findings in the context of relevant computational models related to neurotransmittors such as dopamine, serotonin, acetylcholine and noradrenalin. These include models for reinforcement learning, sequence production, and categorization. We conclude, based on the reviewed literature, that one can predict improved implicit acquisition by moderately elevated dopamine levels and impaired implicit acquisition by moderately decreased dopamine levels. These effects are most prominent in the dorsal striatum. This is supported by a range of behavioral tasks in the empirical literature. Similar predictions can be made for serotonin, although there is yet a lack of support in the literature for serotonin involvement in classical implicit learning tasks. There is currently a lack of evidence for a role of the noradrenergic and cholinergic systems in implicit and related forms of learning. GABA modulators, including benzodiazepines, seem to affect implicit learning in a complex manner and further research is needed. Finally, we identify allosteric AMPA receptors modulators as a potentially interesting target for future investigation of the neuropharmacology of procedural and implicit learning.
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http://dx.doi.org/10.2174/157015910793358178DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3080593PMC
December 2010

What artificial grammar learning reveals about the neurobiology of syntax.

Brain Lang 2012 Feb 12;120(2):83-95. Epub 2010 Oct 12.

Max Planck Institute for Psycholinguistics, P.O. Box 310, NL-6500 AH Nijmegen, The Netherlands.

In this paper we examine the neurobiological correlates of syntax, the processing of structured sequences, by comparing FMRI results on artificial and natural language syntax. We discuss these and similar findings in the context of formal language and computability theory. We used a simple right-linear unification grammar in an implicit artificial grammar learning paradigm in 32 healthy Dutch university students (natural language FMRI data were already acquired for these participants). We predicted that artificial syntax processing would engage the left inferior frontal region (BA 44/45) and that this activation would overlap with syntax-related variability observed in the natural language experiment. The main findings of this study show that the left inferior frontal region centered on BA 44/45 is active during artificial syntax processing of well-formed (grammatical) sequence independent of local subsequence familiarity. The same region is engaged to a greater extent when a syntactic violation is present and structural unification becomes difficult or impossible. The effects related to artificial syntax in the left inferior frontal region (BA 44/45) were essentially identical when we masked these with activity related to natural syntax in the same subjects. Finally, the medial temporal lobe was deactivated during this operation, consistent with the view that implicit processing does not rely on declarative memory mechanisms that engage the medial temporal lobe. In the context of recent FMRI findings, we raise the question whether Broca's region (or subregions) is specifically related to syntactic movement operations or the processing of hierarchically nested non-adjacent dependencies in the discussion section. We conclude that this is not the case. Instead, we argue that the left inferior frontal region is a generic on-line sequence processor that unifies information from various sources in an incremental and recursive manner, independent of whether there are any processing requirements related to syntactic movement or hierarchically nested structures. In addition, we argue that the Chomsky hierarchy is not directly relevant for neurobiological systems.
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http://dx.doi.org/10.1016/j.bandl.2010.08.003DOI Listing
February 2012

Implicit learning and dyslexia.

Ann N Y Acad Sci 2008 Dec;1145:132-50

Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.

Several studies have reported an association between dyslexia and implicit learning deficits. It has been suggested that the weakness in implicit learning observed in dyslexic individuals may be related to sequential processing and implicit sequence learning. In the present article, we review the current literature on implicit learning and dyslexia. We describe a novel, forced-choice structural "mere exposure" artificial grammar learning paradigm and characterize this paradigm in normal readers in relation to the standard grammaticality classification paradigm. We argue that preference classification is a more optimal measure of the outcome of implicit acquisition since in the preference version participants are kept completely unaware of the underlying generative mechanism, while in the grammaticality version, the subjects have, at least in principle, been informed about the existence of an underlying complex set of rules at the point of classification (but not during acquisition). On the basis of the "mere exposure effect," we tested the prediction that the development of preference will correlate with the grammaticality status of the classification items. In addition, we examined the effects of grammaticality (grammatical/nongrammatical) and associative chunk strength (ACS; high/low) on the classification tasks (preference/grammaticality). Using a balanced ACS design in which the factors of grammaticality (grammatical/nongrammatical) and ACS (high/low) were independently controlled in a 2 x 2 factorial design, we confirmed our predictions. We discuss the suitability of this task for further investigation of the implicit learning characteristics in dyslexia.
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http://dx.doi.org/10.1196/annals.1416.012DOI Listing
December 2008

The inferior frontal cortex in artificial syntax processing: an rTMS study.

Brain Res 2008 Aug 6;1224:69-78. Epub 2008 Jun 6.

Max Planck Institute for Psycholinguistics, P.O. Box 310, NL-6500 AH Nijmegen, The Netherlands.

The human capacity to implicitly acquire knowledge of structured sequences has recently been investigated in artificial grammar learning using functional magnetic resonance imaging. It was found that the left inferior frontal cortex (IFC; Brodmann's area (BA) 44/45) was related to classification performance. The objective of this study was to investigate whether the IFC (BA 44/45) is causally related to classification of artificial syntactic structures by means of an off-line repetitive transcranial magnetic stimulation (rTMS) paradigm. We manipulated the stimulus material in a 2 x 2 factorial design with grammaticality status and local substring familiarity as factors. The participants showed a reliable effect of grammaticality on classification of novel items after 5 days of exposure to grammatical exemplars without performance feedback in an implicit acquisition task. The results show that rTMS of BA 44/45 improves syntactic classification performance by increasing the rejection rate of non-grammatical items and by shortening reaction times of correct rejections specifically after left-sided stimulation. A similar pattern of results is observed in FMRI experiments on artificial syntactic classification. These results suggest that activity in the inferior frontal region is causally related to artificial syntax processing.
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http://dx.doi.org/10.1016/j.brainres.2008.05.070DOI Listing
August 2008

Lexical processing in illiteracy: effect of literacy or education?

Cortex 2006 Oct;42(7):1021-7

Department of Psychology, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Difficulties in phonological processing in illiterates have been attributed to their limited phonological awareness, a consequence of their lack of literacy. We sought to explore the potential influence of education on auditory lexical processing above and beyond literacy per se. In order to achieve this goal, we compared a lexical decision making paradigm with a repetition paradigm using words and pseudo-words. We based this choice of tasks on previous research, which has shown that pseudo-word repetition is dependent on the phonological loop; such studies have thus demonstrated a literacy effect on repetition. Instead, lexical decision making is known to depend on the size of one's vocabulary, which is influenced by the level of education attained. Our sample comprised three groups: illiterate no education, literate/low education and literate/high education, individuals. The pattern of our findings confirmed that literacy has an effect on the capacity of the phonological loop, as our illiterate group alone had difficulty with repetition, as compared with both literate/educated groups. Also, our findings suggested an education effect on lexical decision making, as we found a gradation in the performance of the three groups. Therefore, we succeeded in dissecting the effect of literacy and education on auditory lexical processing through the application and comparison of two simple paradigms.
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http://dx.doi.org/10.1016/s0010-9452(08)70208-9DOI Listing
October 2006

Semantic and phonological processing in illiteracy.

J Int Neuropsychol Soc 2004 Oct;10(6):818-27

Department of Psychology, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Researchers of cognitive processing in illiteracy have proposed that the acquisition of literacy modifies the functional organization of the brain. They have suggested that, while illiterate individuals have access only to innate semantic processing skills, those who have learned the correspondence between graphemes and phonemes have several mechanisms available to them through which to process oral language. We conducted 2 experiments to verify that suggestion with respect to language processing, and to elucidate further the differences between literate and illiterate individuals in the cognitive strategies used to process oral language, as well as hemispheric specialization for these processes. Our findings suggest that semantic processing strategies are qualitatively the same in literates and illiterates, despite the fact that overall performance is augmented by increased education. In contrast, explicit processing of oral information based on phonological characteristics appears to be qualitatively different between literates and illiterates: effective strategies in the processing of phonological information depend upon having had a formal education, regardless of the level of education. We also confirmed the differential abilities needed for the processing of semantic and phonological information and related them to hemisphere-specific processing.
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http://dx.doi.org/10.1017/s1355617704106036DOI Listing
October 2004

Assessment of memory skills in illiterates: strategy differences or test artifact?

Clin Neuropsychol 2003 May;17(2):143-52

Department of Psychology, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Previous studies have reported that illiterates perform more poorly than literates on a variety of neuropsychological measures. We investigated the hypothesis that putative memory deficits in illiterates are an artifact of the assessment tools used rather than a reflection of an 'underdeveloped' ability. In order to accomplish this, we designed two tests, a word list learning test and an object learning test. The illiterate group performed more poorly than semiliterate and literate groups on most variables of the word list learning test, but only on delayed recall and semantic clustering on the object learning test. Our findings suggest that poor memory performance among illiterates can be attributed both to the nature of the task, as well as to the use of different cognitive mechanisms to recall learned information. Presumably, formal education may enhance the innate ability of learning through training individuals in efficient learning and retrieval strategies. We emphasize the importance of developing and using ecologically valid neuropsychological tests to assess illiterate individuals.
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http://dx.doi.org/10.1076/clin.17.2.143.16505DOI Listing
May 2003