Exploring the inner speech process in verbal working memory

Verbal working memory (VWM) is the ability to dynamically preserve and manipulate verbal information for brief periods of time. VWM is maintained through a silent "inner speech" process (Baddeley, 1986; Baddeley & Hitch, 1974). It is well established in the behavioral and neuroimaging literature that VWM can be disrupted by the simultaneous (concurrent) performance of simple speech tasks (e.g. overt concurrent articulation of a word or digit) (Caplan et al., 2000; Larsen & Baddeley, 2003). Our primary goal in these experiments is to test whether VWM and overt concurrent articulation will have one or more overlapping regions of activation in areas commonly associated with speech processing, and to determine whether such regions are active during simple tapping tasks. Due to concerns about overt movement artifacts, we also explore covert version of speech and tapping tasks. Experiment 1 was a behavioral study that examined the effects of overt and covert concurrent articulation and finger tapping on VWM. We found that overtly and covertly concurrently articulating "the" were the most detrimental to subjects' recall ability. These effects could be attributed to dual-task interference effects at the level of inner speech in VWM, thus, indicating a shared set of neural regions for all speech and VWM. At the same time, the effect sizes were different for the overt and covert versions of our tasks, raising questions about the common assumption of shared substrates. Experiment 2 was an imaging study designed to examine whether there were shared neural regions between simple speech tasks and VWM and to further explore differences between overt and covert tasks. The results from this experiment provided only weak evidence implicating two candidate regions as the shared locus of activation: the left cerebellum and left superior temporal gyrus. We also found interesting evidence in support of distinct sets of regions for overt versus covert versions of the tasks

The VWFA Is the Home of Orthographic Learning When Houses Are Used as Letters

Learning to read specializes a portion of the left mid-fusiform cortex for printed word recognition, the putative visual word form area (VWFA). This study examined whether a VWFA specialized for English is sufficiently malleable to support learning a perceptually atypical second writing system. The study utilized an artificial orthography, HouseFont, in which house images represent English phonemes. House images elicit category-biased activation in a spatially distinct brain region, the so-called parahippocampal place area (PPA). Using house images as letters made it possible to test whether the capacity for learning a second writing system involves neural territory that supports reading in the first writing system, or neural territory tuned for the visual features of the new orthography. Twelve human adults completed two weeks of training to establish basic HouseFont reading proficiency and underwent functional neuroimaging pre and post-training. Analysis of three functionally defined regions of interest (ROIs), the VWFA, and left and right PPA, found significant pre-training versus post-training increases in response to HouseFont words only in the VWFA. Analysis of the relationship between the behavioral and neural data found that activation changes from pre-training to post-training within the VWFA predicted HouseFont reading speed. These results demonstrate that learning a new orthography utilizes neural territory previously specialized by the acquisition of a native writing system. Further, they suggest VWFA engagement is driven by orthographic functionality and not the visual characteristics of graphemes, which informs the broader debate about the nature of category-specialized areas in visual association cortex

Navigating infection risk during oviposition and cannibalistic foraging in a holometabolous insect

Deciding where to eat and raise offspring carries important fitness consequences for all animals, especially if foraging, feeding and reproduction increase pathogen exposure. In insects with complete metamorphosis, foraging mainly occurs during the larval stage, while oviposition decisions are made by adult females. Selection for infection avoidance behaviours may therefore be developmentally uncoupled. Using a combination of experimental infections and behavioral choice assays, we tested if Drosophila melanogaster fruit flies avoid infectious environments at distinct developmental stages. When given conspecific fly carcasses as a food source, larvae did not discriminate between carcasses that were clean or infected with the pathogenic Drosophila C Virus (DCV), even though cannibalism was a viable route of DCV transmission. When laying eggs, DCV-infected females did not discriminate between infectious and non-infectious carcasses. Healthy mothers however, laid more eggs near a clean rather than an infectious carcass. Avoidance during oviposition changed over time: after an initial oviposition period, healthy mothers stopped avoiding infectious carcasses. We attribute this to a trade-off between infection risk and reproduction. Laying eggs near potentially infectious carcasses was always preferred to sites containing only fly food. Our findings suggest infection avoidance contributes to how mothers provision their offspring and underline the need to consider infection avoidance behaviors at multiple life-stages

Interactions among Drosophila larvae before and during collision

In populations of Drosophila larvae, both, an aggregation and a dispersal behavior can be observed. However, the mechanisms coordinating larval locomotion in respect to other animals, especially in close proximity and during/after physical contacts are currently only little understood. Here we test whether relevant information is perceived before or during larva-larva contacts, analyze its influence on behavior and ask whether larvae avoid or pursue collisions. Employing frustrated total internal reflection-based imaging (FIM) we first found that larvae visually detect other moving larvae in a narrow perceptive field and respond with characteristic escape reactions. To decipher larval locomotion not only before but also during the collision we utilized a two color FIM approach (FIM(2c)), which allowed to faithfully extract the posture and motion of colliding animals. We show that during collision, larval locomotion freezes and sensory information is sampled during a KISS phase (german: Kollisions Induziertes Stopp Syndrom or english: collision induced stop syndrome). Interestingly, larvae react differently to living, dead or artificial larvae, discriminate other Drosophila species and have an increased bending probability for a short period after the collision terminates. Thus, Drosophila larvae evolved means to specify behaviors in response to other larvae

From Epigenetic Associations to Biological and Psychosocial Explanations in Mental Health

The development of mental disorders constitutes a complex phenomenon driven by unique social, psychological and biological factors such as genetics and epigenetics, throughout an individual's life course. Both environmental and genetic factors have an impact on mental health phenotypes and act simultaneously to induce changes in brain and behavior. Here, we describe and critically evaluate the current literature on gene-environment interactions and epigenetics on mental health by highlighting recent human and animal studies. We furthermore review some of the main ethical and social implications concerning gene-environment interactions and epigenetics and provide explanations and suggestions on how to move from statistical and epigenetic associations to biological and psychological explanations within a multi-disciplinary and integrative approach of understanding mental health

Dryad_Experiment_4

Data for Experiments 4A-4C

Dryad_Experiment_1

Data for Experiment 1A-1E. Collected in the lab. Created in microsoft excel

Dryad_Experiment_2

Covers Experiments 2A-2C. Collected in the lab. Created in Microsoft Excel

Dryad_Experiment_3

Covers Experiments 3A and 3B. Collected in the lab. Created in Microsoft excel