Juan Andrés Hernández-Cabrera

Orthographic Coding: Brain Activation for Letters, Symbols, and Digits

The present experiment investigates the input coding mechanisms of 3 common printed characters: letters, numbers, and symbols. Despite research in this area, it is yet unclear whether the identity of these 3 elements is processed through the same or different brain pathways. In addition, some computational models propose that the position-in-string coding of these elements responds to general flexible mechanisms of the visual system that are not character-specific, whereas others suggest that the position coding of letters responds to specific processes that are different from those that guide the position-in-string assignment of other types of visual objects. Here, in an fMRI study, we manipulated character position and character identity through the transposition or substitution of 2 internal elements within strings of 4 elements. Participants were presented with 2 consecutive visual strings and asked to decide whether they were the same or different. The results showed: 1) that some brain areas responded more to letters than to numbers and vice versa, suggesting that processing may follow different brain pathways; 2) that the left parietal cortex is involved in letter identity, and critically in letter position coding, specifically contributing to the early stages of the reading process; and that 3) a stimulus-specific mechanism for letter position coding is operating during orthographic processing.

Tracking the Time Course of Competition During Word Production: Evidence for a Post-Retrieval Mechanism of Conflict Resolution

Producing a word is often complicated by the fact that there are other words that share meaning with the intended word. The competition between words that arises in such a situation is a well-known phenomenon in the word production literature. An ongoing debate in a number of research domains has concerned the question of how competition between words is resolved. Here, we contributed to the debate by presenting evidence that indicates that resolving competition during word production involves a postretrieval mechanism of conflict resolution. Specifically, we tracked the time course of competition during word production using electroencephalography. In the experiment, participants named pictures in contexts that varied in the strength of competition. The electrophysiological data show that competition is associated with a late, frontally distributed component that arises between 500 and 750 ms after picture presentation. These data are interpreted in terms of a model of word production that relies on a mechanism of cognitive control.

Play Context, Commitment, and Dating Violence: A Structural Equation Model

This study develops a structural equation model to describe the effect of two groups of factors (type of commitment and play context) on the violence experienced during intimate partner conflict. After contrasting the model in adolescents and university students, we have confirmed that aggressive play and the simulation of jealousy and anger increase the risk of dating victimization during conflicts through the negative reactions that they cause. Where commitment is concerned, the results are different according to whether commitment is personal or constraining. The former provides protection against dating victimization, reducing risk in the play context, whereas the latter has no effect on the violence experienced but facilitates a more dangerous play dynamic. The model can be applied in the design of programs to prevent dating violence.

Distinct subtypes of Alzheimer’s disease based on patterns of brain atrophy: longitudinal trajectories and clinical applications

Atrophy patterns on MRI can reliably predict three neuropathological subtypes of Alzheimer’s disease (AD): typical, limbic-predominant, or hippocampal-sparing. A method to enable their investigation in the clinical routine is still lacking. We aimed to (1) validate the combined use of visual rating scales for identification of AD subtypes; (2) characterise these subtypes at baseline and over two years; and (3) investigate how atrophy patterns and non-memory cognitive domains contribute to memory impairment. AD patients were classified as either typical AD (n = 100), limbic-predominant (n = 33), or hippocampal-sparing (n = 35) by using the Scheltens’ scale for medial temporal lobe atrophy (MTA), the Koedam’s scale for posterior atrophy (PA), and the Pasquier’s global cortical atrophy scale for frontal atrophy (GCA-F). A fourth group with no atrophy was also identified (n = 30). 230 healthy controls were also included. There was great overlap among subtypes in demographic, clinical, and cognitive variables. Memory performance was more dependent on non-memory cognitive functions in hippocampal-sparing and the no atrophy group. Hippocampal-sparing and the no atrophy group showed less aggressive disease progression. Visual rating scales can be used to identify distinct AD subtypes. Recognizing AD heterogeneity is important and visual rating scales may facilitate investigation of AD heterogeneity in clinical routine.

Inferior fronto-temporo-occipital connectivity: a missing link between maltreated girls and neglectful mothers

The neurobiological alterations resulting from adverse childhood experiences that subsequently may lead to neglectful mothering are poorly understood. Maternal neglect of an infant’s basic needs is the most prevalent type of child maltreatment. We tested white matter alterations in neglectful mothers, the majority of whom had also suffered maltreatment in their childhood, and compared them to a matched control group. The two groups were discriminated by a structural brain connectivity pattern comprising inferior fronto-temporo-occipital connectivity, which constitutes a major portion of the face-processing network and was indexed by fewer streamlines in neglectful mothers. Mediation and regression analyses showed that fewer streamlines in the right inferior longitudinal fasciculus tract (ILF-R) predicted a poorer quality of mother–child emotional availability observed during cooperative play and that effect depended on the respective interactions with left and right inferior fronto-occipital fasciculi (IFO-R/L), with no significant impact of psychopathological and cognitive conditions. Volume alteration in ILF-R but not in IFO-L modulated the impact of having been maltreated on emotional availability. The findings suggest the altered inferior fronto-temporal-occipital connectivity, affecting emotional visual processing, as a possible common neurological substrate linking a history of childhood maltreatment with maternal neglect.

Semantic parafoveal-on-foveal effects and preview benefits in reading: Evidence from Fixation Related Potentials

During reading parafoveal information can affect the processing of the word currently fixated (parafovea-on-fovea effect) and words perceived parafoveally can facilitate their subsequent processing when they are fixated on (preview effect). We investigated parafoveal processing by simultaneously recording eye movements and EEG measures. Participants read word pairs that could be semantically associated or not. Additionally, the boundary paradigm allowed us to carry out the same manipulation on parafoveal previews that were displayed until readers gaze moved to the target words. Event Related Potentials time-locked to the prime-preview presentation showed a parafoveal-on-foveal N400 effect. Fixation Related Potentials time locked to the saccade offset showed an N400 effect related to the prime-target relationship. Furthermore, this later effect interacted with the semantic manipulation of the previews, supporting a semantic preview benefit. These results demonstrate that at least under optimal conditions foveal and parafoveal information can be simultaneously processed and integrated.

The interactive effect of demographic and clinical factors on hippocampal volume: A multicohort study on 1958 cognitively normal individuals

Alzheimers disease is characterized by hippocampal atrophy. Other factors also influence the hippocampal volume, but their interactive effect has not been investigated before in cognitively healthy individuals. The aim of this study is to evaluate the interactive effect of key demographic and clinical factors on hippocampal volume, in contrast to previous studies frequently investigating these factors in a separate manner. Also, to investigate how comparable the control groups from ADNI, AIBL, and AddNeuroMed are with five population‐based cohorts. In this study, 1958 participants were included (100 AddNeuroMed, 226 ADNI, 155 AIBL, 59 BRC, 295 GENIC, 279 BioFiNDER, 398 PIVUS, and 446 SNAC‐K). ANOVA and random forest were used for testing between‐cohort differences in demographic‐clinical variables. Multiple regression was used to study the influence of demographic‐clinical variables on hippocampal volume. ANCOVA was used to analyze whether between‐cohort differences in demographic‐clinical variables explained between‐cohort differences in hippocampal volume. Age and global brain atrophy were the most important variables in explaining variability in hippocampal volume. These variables were not only important themselves but also in interaction with gender, education, MMSE, and total intracranial volume. AddNeuroMed, ADNI, and AIBL differed from the population‐based cohorts in several demographic‐clinical variables that had a significant effect on hippocampal volume. Variability in hippocampal volume in individuals with normal cognition is high. Differences that previously tended to be related to disease mechanisms could also be partly explained by demographic and clinical factors independent from the disease. Furthermore, cognitively normal individuals especially from ADNI and AIBL are not representative of the general population. These findings may have important implications for future research and clinical trials, translating imaging biomarkers to the general population, and validating current diagnostic criteria for Alzheimers disease and predementia stages.

Disentangling meaning in the brain: Left temporal involvement in agreement processing

Sentence comprehension is successfully accomplished by means of a form-to-meaning mapping procedure that relies on the extraction of morphosyntactic information from the input and its mapping to higher-level semantic-discourse representations. In this study, we sought to determine whether neuroanatomically distinct brain regions are involved in the processing of different types of information contained in the propositional meaning of a sentence, namely person and number. While person information indexes the role that an individual has in discourse (i.e., the speaker, the addressee or the entity being talked about by speaker and addressee), number indicates its cardinality (i.e., a single entity vs a multitude of entities). An event-related functional magnetic resonance imaging (fMRI) experiment was run using agreement-Correct and Person- and Number-violated sentences in Spanish, to disentangle the processing mechanisms and neural substrates associated with the building of discourse and cardinality representations. The contrast between Person and Number Violations showed qualitative and quantitative differences. A greater response for person compared to number was found in the left middle temporal gyrus (LMTG). However, critically, a posterior-to-anterior functional gradient emerged within this region. While the posterior portion of the LMTG was sensitive to both Person and Number Violations, the anterior portion of this region showed selective response for Person Violations. These results confirm that the comprehension of the propositional meaning of a sentence results from a composite, feature-sensitive mechanism of form-to-meaning mapping in which the nodes of the language network are differentially involved.

Verbal and nominal agreement: An fMRI study.

Agreement computation is one of the pillars of language comprehension. In this fMRI study, we investigated the neuro-cognitive processes of agreement associated with number feature covariance in subject-verb agreement and determiner-noun concord in Spanish by creating mismatches (ella/*ellas corre, she/*they dances vs. el/*los anillo, thesg/*thepl ring). The results evidenced the engagement of a common bilateral fronto-parietal monitoring system, not language specific, and a left fronto-temporal system that seems to be specifically related to different aspects of phrase and sentence processing. In particular, the major difference was found in the anterior portion of the left MTG-STG, which we relate to fine-grained syntactic-combinatorial building mechanisms apparently controlled by the pars opercularis within the LIFG. These results suggest that general conflict-monitoring processes operate in parallel with language-specific mechanisms that are sensitive to the specificity of agreement type for the detection of feature covariance among sentence constituents. Specifically, the coupling between these frontal and temporal regions seems to be flexible enough to show sensitivity to the fine-grained combinatorial mechanisms that underlie nominal and subject-verb agreement.

Syllabic Strategy as Opposed to Coda Optimization in the Segmentation of Spanish Letter-Strings Using Word Spotting

ABSTRACT A word-spotting task is used in Spanish to test the way in which polysyllabic letter-strings are parsed in this language. Monosyllabic words (e.g., bar) embedded at the beginning of a pseudoword were immediately followed by either a coda-forming consonant (e.g., barto) or a vowel (e.g., baros). In the former case, the embedded word corresponds to the first spoken syllable, whereas it cuts across the syllable boundary in the latter case. Unlike a previous study in English using the same methodology (Taft & Álvarez, 2014), the embedded word was found to be easier to detect when followed by a consonant than a vowel, at least for low-frequency words. It was concluded that phonological recoding is more important in the parsing of Spanish words than English words, where maximization of the coda dominates instead.