Hemispheric asymmetries in the split-fovea model of semantic processing

We report a series of neural network models of semantic processing of single English words in the left and the right hemispheres of the brain. We implement the foveal splitting of the visual field and assess the influence of this splitting on a mapping from orthography to semantic representations in single word reading. The models were trained on English four-letter words, presented according to their frequency in all positions encountered during normal reading. The architecture of the model interacted with the training set to produce processing asymmetries comparable to those found in behavioral studies. First, the cueing effects of dominant and subordinate meanings of ambiguous words were different for words presented to the left or to the right of the input layer. Second, priming effects of groups of related words were stronger in the left input than the right input of the model. These effects were caused by coarser-coding in the right half compared with the left half of the model, an emergent effect of the split model interacting with informational asymmetries in the left and right parts of words in the lexicon of English. Some or all of the behavioral data for reading single words in English may have a similar origin.     

Meaning construction and integration in children with hydrocephalus

Text comprehension processes were investigated in children with hydrocephalus, a neurodevelopmental disorder associated with good word decoding, but deficient reading comprehension. In Experiment 1, hydrocephalus and control groups were similar in processes related to activating word meanings and using context to enhance meaning. The hydrocephalus group was poorer at suppressing contextually irrelevant meanings. In Experiment 2, the hydrocephalus group had difficulty integrating information from an earlier read sentence to understand a new sentence as textual distance between the two propositions increased, suggesting difficulty in reactivation processes related to comprehension. Results are discussed in relation to cognitive and neurocognitive models of comprehension.     

Neuromotor speech deficits in children and adults with spina bifida and hydrocephalus

Acquired cerebellar lesions are associated with motor speech deficits. Spina bifida with hydrocephalus (SBH) is a neurodevelopmental disorder that involves significant dysmorphology of the cerebellum. Videotaped narratives produced by 40 children and adults with SBH and their 40 age-matched controls were coded for three motor speech deficits: dysfluency, ataxic dysarthria (articulatory inaccuracy, prosodic excess, and phonatory-prosodic insufficiency) (Brown, Darley, & Aronson, 1970; Darley, Aronson, & Brown, 1969a), and speech rate. Individuals with SBH had more motor speech deficits than controls. Dysfluency was related to an interaction between chronological age and SBH. Speech rate was related independently to chronological age and SBH. Ataxic dysarthria was related to the biology of SBH, and was associated with both physical phenotype (level of spinal cord lesion) and medical history (number of shunt revisions). The data show that developmental as well as acquired lesions of the cerebellum disrupt motor speech, and add to the developmental role of the cerebellum in the automatization of motor skills, including speech.     

Ties to influential adults among black and white adolescents: culture,social class,and family networks

Although prior research suggests the importance of nonparental adults to adolescents, the ecological context of those relationships has received little attention. This study examined ties to influential adults among 122 adolescents who varied by race, family structure, and gender. The strongest effects were for race. Blacks reported stronger ties than Whites to the maternal grandmother as well as more supportive interactions with adult males. While race differences in grandparental ties were robust across social class (SES), ties to an influential adult male became nonsignificant upon controlling for SES. African American girls from divorced families consistently reported the strongest ties. Discussion considers the role of culture versus SES in explaining race differences. Implications for mentoring interventions are proposed, with special attention to the role of actualizing latent ties to already existing network members.     

Division of labor between the hemispheres for complex but not simple tasks: an implemented connectionist model

When stimuli have to be matched in a complex task (such as whether 2 letters have the same name), then performance is better when stimuli are presented across the hemispheres of the brain, whereas for simpler tasks (such as whether 2 letters have the same shape), better performance is achieved when stimuli are presented unilaterally. The authors show that this bilateral distribution advantage effect emerged spontaneously in a neural network model learning to solve simple and complex tasks with separate input layers and separate, but interconnected, resources in a hidden layer. The authors show that relating computational models to behavioral and imaging data proves fruitful for understanding hemispheric processing and generating testable hypotheses.     

Hemispheric asymmetries in cognitive modeling: connectionist modeling of unilateral visual neglect

Neglect is an acquired cognitive disorder characterized by a lack of processing of one side of a stimulus or representational space. There are hemispheric asymmetries in its cause and in its effects, but implemented computational models of neglect have tended not to incorporate this fact. The authors report a series of neural network simulations of the line-bisection task. They test the hypothesis that simple, neuroanatomically realistic principles of connectivity in the nervous system can produce emergent behaviors that capture a wide range of quantitative and qualitative data observed in neglect patients presenting with general visuospatial neglect. They demonstrate that exploring low-level architectural principles in implemented computational models is both a productive avenue of research and offers the most parsimonious explanations of behaviors observed in patients.     

Patients’ Opinions on Genetic Counseling on the Increased Risk of Parkinson Disease among Gaucher Disease Carriers

Gaucher disease (GD) is an autosomal recessive disease caused by GBA mutations that is especially common in the Ashkenazi Jewish (AJ) population. The link between GBA mutations and Parkinson disease (PD), a later-onset neurodegenerative condition, is well established, and studies have shown that GBA carriers have an increased lifetime risk of developing PD. Carrier screening for GD is frequently offered to couples during or prior to pregnancy, especially to those of AJ descent. However, no studies have been performed to assess if prospective parents would want to learn about their risk of developing PD incidentally through carrier screening. It is also unknown if pre-test counseling on this topic would affect screening uptake. In order to answer these questions, a survey was administered to individuals who screened negative for GBA mutations. Of the 75 participants, 86.7% believed that patients should be informed about the increased risk of PD prior to having GD carrier screening, and 93.3% responded that this information would not have changed their decision to have carrier screening. These results indicate that healthcare providers should take into consideration patient preferences when determining how to counsel about GD carrier screening. Additionally, these results have implications for genetic counseling about other later-onset conditions that may be incidentally ascertained through carrier screening.     

Functional connectivity of reflective and brooding rumination in depressed and healthy women

Ruminative thinking is related to an increased risk for major depressive disorder (MDD) and perpetuates negative mood states. Rumination, uncontrollable negative thoughts about the self, may comprise both reflective and brooding components. However, only brooding rumination is consistently associated with increased negativity bias and negative coping styles, while reflective rumination has a less clear relationship with negative outcomes in healthy and depressed participants. The current study examined seed-to-voxel (S2.V) resting-state functional connectivity (FC) in a sample of healthy (HC) and depressed (MDD) adult women (HC: n=50, MDD: n=33). The S2V FC of six key brain regions, including the left and right amygdala, anterior and posterior cingulate cortex (ACC, PCC), and medial and dorsolateral prefrontal cortices (mPFC, dlPFC), was correlated with self-reported reflective and brooding rumination. Results indicate that HC and MDD participants had increased brooding rumination associated with decreased FC between the left amygdala and the right temporal pole. Moreover, reflective rumination was associated with distinct FC of the mPFC, PCC, and ACC with parietal, occipital, and cingulate regions. Depressed participants, compared with HC, exhibited decreased FC between the PCC and a region in the right middle frontal gyrus. The results of the current study add to the understanding of the neural underpinnings of different forms of self-related cognition—brooding and reflective rumination—in healthy and depressed women.