Right Hemisphere Lateralization Research Articles

La neuroprotection périnatale en 2015

Perinatal brain injury is a significant cause of adverse neurodevelopmental outcomes. The objective of this systematic review was to identify patterns of altered brain function, quantified using functional connectivity (FC) changes in resting-state fMRI (rs-fMRI) data, that were associated with motor and language outcomes in individuals with a history of perinatal brain injury. A systematic search using electronic databases was conducted to identify relevant studies. A total of 10 studies were included in the systematic review, representing 260 individuals with a history of perinatal brain injury. Motor and language outcomes were measured at time points ranging from 4 months to 29 years 1 month. Relations between FC and motor measures revealed increased intra-hemispheric FC, reduced inter-hemispheric FC and impaired lateralization of motor-related brain regions associated with motor outcomes. Altered FC within sensorimotor, visual, cerebellum and frontoparietal networks, and between sensorimotor, visual, auditory and higher-order networks, including cerebellum, frontoparietal, default-mode, salience, self-referential and attentional networks were also associated with motor outcomes. In studies assessing the relationship between rs-fMRI and language outcome, reduced intra-hemispheric FC, increased inter-hemispheric FC and right-hemisphere lateralization of language-related brain regions correlated with language outcomes. Evidence from this systematic review suggests a possible association between diaschisis and motor and language impairments in individuals after perinatal brain lesions. These findings support the need to explore the contributions of additional brain regions functionally connected but remote from the primary lesioned brain area for targeted treatments and appropriate intervention, though more studies with increased standardization across neuroimaging and neurodevelopmental assessments are needed.

Variable left-hemisphere language and orthographic lateralization reduces right-hemisphere face lateralization.

It is commonly believed that, in right-handed individuals, words and faces are processed by distinct neural systems: one in the left hemisphere (LH) for words and the other in the right hemisphere (RH) for faces. Emerging evidence suggests, however, that hemispheric selectivity for words and for faces may not be independent of each other. One recent account suggests that words become lateralized to the LH to interact more effectively with language regions, and subsequently, as a result of competition with words for representational space, faces become lateralized to the RH. On this interactive account, left-handed individuals, who as a group show greater variability with respect to hemispheric language dominance, might be expected to show greater variability in their degree of RH lateralization of faces as well. The current study uses behavioral measures and ERPs to compare the hemispheric specialization for both words and faces in right- and left-handed adult individuals. Although both right- and left-handed groups demonstrated LH over RH superiority in discrimination accuracy for words, only the right-handed group demonstrated RH over LH advantage in discrimination accuracy for faces. Consistent with this, increased right-handedness was related to an increase in RH superiority for face processing, as measured by the strength of the N170 ERP component. Interestingly, the degree of RH behavioral superiority for face processing and the amplitude of the RH N170 for faces could be predicted by the magnitude of the N170 ERP response to words in the LH. These results are discussed in terms of a theoretical account in which the typical RH face lateralization fails to emerge in individuals with atypical language lateralization because of weakened competition from the LH representation of words.

On the relationship between degree of hand-preference and degree of language lateralization

Language lateralization and hand-preference show inter-individual variation in the degree of lateralization to the left- or right, but their relation is not fully understood. Disentangling this relation could aid elucidating the mechanisms underlying these traits. The relation between degree of language lateralization and degree of hand-preference was investigated in extended pedigrees with multi-generational left-handedness (n=310). Language lateralization was measured with functional Transcranial Doppler, hand-preference with the Edinburgh Handedness Inventory. Degree of hand-preference did not mirror degree of language lateralization. Instead, the prevalence of right-hemispheric and bilateral language lateralization rises with increasing strength of left-handedness. Degree of hand-preference does not predict degree of language lateralization, thus refuting genetic models in which one mechanism defines both hand-preference and language lateralization. Instead, our findings suggest a model in which increasing strength of left-handedness is associated with increased variation in directionality of cerebral dominance.

Lateralization of music processing with noises in the auditory cortex: an fNIRS study.

The present study is to determine the effects of background noise on the hemispheric lateralization in music processing by exposing 14 subjects to four different auditory environments: music segments only, noise segments only, music + noise segments, and the entire music interfered by noise segments. The hemodynamic responses in both hemispheres caused by the perception of music in 10 different conditions were measured using functional near-infrared spectroscopy. As a feature to distinguish stimulus-evoked hemodynamics, the difference between the mean and the minimum value of the hemodynamic response for a given stimulus was used. The right-hemispheric lateralization in music processing was about 75% (instead of continuous music, only music segments were heard). If the stimuli were only noises, the lateralization was about 65%. But, if the music was mixed with noises, the right-hemispheric lateralization has increased. Particularly, if the noise was a little bit lower than the music (i.e., music level 10~15%, noise level 10%), the entire subjects showed the right-hemispheric lateralization: This is due to the subjects' effort to hear the music in the presence of noises. However, too much noise has reduced the subjects' discerning efforts.

Let's face it: reading acquisition, face and word processing.

A TIGHT LINK BETWEEN READING ACQUISITION AND CHANGES IN FACE PROCESSING The invention of writing is one of the most important cultural changes of mankind. Notably, because reading was invented only 5000 years ago, there was not sufficient time to evolve a brain system devoted to visual word recognition. Nevertheless, learning to read leads to the development of a strong response to written materials in the left fusiform gyrus, in the “visual word form area” (VWFA, e.g., Dehaene, 2009). Consequently, reading must rely on pre-existing neural systems for vision and language, which may be partially “recycled” for the specific problems posed by reading (Dehaene, 2005; Dehaene and Cohen, 2007). This consistent localization is related to prior properties of the corresponding tissue, which make it particularly suitable to the specific problems posed by the invariant visual recognition of written words (Dehaene, 2009): bias for foveal stimuli (Hasson et al., 2002), posterior-toanterior increase in perceptual invariance (Grill-Spector et al., 1998; Lerner et al., 2001), and more direct projection fibers to language areas (Cohen et al., 2000; Epelbaum et al., 2008). The neuronal recycling model predicts that, as cortical territories dedicated to evolutionarily older functions are invaded by novel cultural objects, their prior organization should slightly shift away from the original function (though the original function is never entirely erased). As a result, reading acquisition should displace whichever evolutionary older function is implemented in the site of the VWFA. In a recent fMRI study (Dehaene et al., 2010) comparing illiterate to literate adults, we showed that learning to read competes with the cortical representation of other visual objects, especially faces. With increasing literacy, cortical responses to faces decrease slightly in the left fusiform region, while increasing strongly in the right fusiform area (FFA). Thus, right-hemispheric lateralization for faces is increased in literates compared to illiterates. Consistent evidence was also reported when comparing 9-year-old normal readers and dyslexic children. Not only did responses to written words showed a greater left lateralization in normal readers, but responses to faces were also more strongly right lateralized (Monzalvo et al., 2012; cf. also Monzalvo, 2011). Further developmental studies also reveal a tight link between reading acquisition and changes in face processing. Cantlon et al. (2011) demonstrated that 4-year-old-children show decreasing responses to faces in the left fusiform gyrus with increasing knowledge of letter and number symbols. Li et al. (2013) found for Chinese preschooler’s a facilitative effect of early exposure to reading in neural responses to visual words. Such a facilitative effect had a temporary cost in neural response to faces, which did not show the mature pattern seen in adults. Dundas et al. (2012) studied the development of hemispheric specialization for written words and faces in children, adolescents and adults, and found that the left-hemispheric specialization for words develops prior to the right-hemispheric specialization for faces, with face lateralization related to reading comprehension ability (cf. also Pinel et al., 2014). The competition between different categories seems to rely on enhanced neuronal specificity, namely on decreased responses to non-preferred stimuli as opposed to an increased response to the preferred category. Indeed, Cantlon et al. (2011) found a decrease for non-preferred stimuli in VWFA and FFA during child development. Joseph et al. (2011) reported both progressive changes, i.e., increasing face-specialization in a brain region with age, and regressive changes, i.e., decreasing face-specialization with age. Indeed, many brain regions recruited in children for face processing showed reduced specialization for faces by adulthood. Such regressive changes support the idea that some areas of the face network may lose out, at a cellular and a functional level, to promote specialization. Consistent with this scenario, in Pinel et al. (2014)’s study stronger leftward asymmetry for the VWFA and rightward asymmetry for the FFA were characterized by reduced activation in homolog areas of the contralateral hemisphere. All these observations support the existence of competition for cortical space between the VWFA and the preexisting neural coding of faces (Dehaene, 2005; Dehaene and Cohen, 2007; Plaut and Behrmann, 2011), with some displacement of fusiform face-sensitive areas toward the right hemisphere. A similar theoretical perspective (Nestor et al., 2012; Behrmann and Plaut, 2013) espouses a competitive interaction between distributed circuits for faces and word recognition for foveally-biased cortex, constrained by the need to integrate reading with the language system primarily left-lateralized. Recently, we investigated the behavioral consequences of this brain reorganization (Ventura et al., 2013). Using the face composite task, we found that literates are consistently less holistic than illiterate

Effects of Recurrent Acute Otitis Media on Cortical Speech-Sound Processing in 2-Year Old Children

To investigate at the age of 2 years the effects of childhood recurrent acute otitis media (RAOM) on central auditory processing by using cortical event-related potentials elicited by syllable stimuli. During a 1-year period, 22- to 26-month-old children fulfilling the criteria for tympanostomy tube insertion in Oulu University Hospital, Oulu, Finland, were recruited to the RAOM group (N = 20). The control group (N = 19) was matched by age, sex, and mother's educational level. In both groups, children were typically developing and had no family history of language disorder or developmental language problems. Finnish syllables /ke:/ and /pi:/ as standards and their variants with changes in frequency, intensity, vowel, consonant, and vowel duration as deviants were used to record P1, N2, and mismatch negativity (MMN) responses in the multifeature paradigm. The clinically healthy ears at the time of registration were a prerequisite for the participation. Children with RAOM and their controls showed the age-typical P1 and N2 responses with no differences in the amplitudes or latencies between the groups, which suggests unaffected basic encoding of sound features and sound representation formation. However, the groups showed different auditory discrimination profiles. In children with RAOM, frequency and vowel MMN amplitudes were increased. Furthermore, the MMN latency for the frequency change was shorter and the frequency MMN amplitude lateralized to the left hemisphere in the RAOM group instead of an adult-like right-hemispheric lateralization observed in the controls. The children with RAOM had a more anterior MMN amplitude scalp distribution for the intensity change than control children. In addition, the MMN amplitude elicited by consonant change was evenly distributed unlike in controls, who had a left-side preponderant lateralization. Taken together, these results suggest an elevated responsiveness for frequency, vowel, and intensity changes, and an immature pattern of discriminating small speech sound contrasts in children with RAOM. The results suggest that childhood RAOM does not affect the central auditory pathway integrity or sound encoding. However, RAOM may lead to aberrant preattentive discrimination of sound features even when the peripheral auditory input is normal. These results are clinically significant because even transient problems with auditory processing may delay language development.

A different view on the checkerboard? Alterations in early and late visually evoked EEG potentials in Asperger observers.

BackgroundAsperger Autism is a lifelong psychiatric condition with highly circumscribed interests and routines, problems in social cognition, verbal and nonverbal communication, and also perceptual abnormalities with sensory hypersensitivity. To objectify both lower-level visual and cognitive alterations we looked for differences in visual event-related potentials (EEG) between Asperger observers and matched controls while they observed simple checkerboard stimuli.MethodsIn a balanced oddball paradigm checkerboards of two checksizes (0.6° and 1.2°) were presented with different frequencies. Participants counted the occurrence times of the rare fine or rare coarse checkerboards in different experimental conditions. We focused on early visual ERP differences as a function of checkerboard size and the classical P3b ERP component as an indicator of cognitive processing.ResultsWe found an early (100–200 ms after stimulus onset) occipital ERP effect of checkerboard size (dominant spatial frequency). This effect was weaker in the Asperger than in the control observers. Further a typical parietal/central oddball-P3b occurred at 500 ms with the rare checkerboards. The P3b showed a right-hemispheric lateralization, which was more prominent in Asperger than in control observers.DiscussionThe difference in the early occipital ERP effect between the two groups may be a physiological marker of differences in the processing of small visual details in Asperger observers compared to normal controls. The stronger lateralization of the P3b in Asperger observers may indicate a stronger involvement of the right-hemispheric network of bottom-up attention. The lateralization of the P3b signal might be a compensatory consequence of the compromised early checksize effect. Higher-level analytical information processing units may need to compensate for difficulties in low-level signal analysis.

Literacy acquisition reduces the influence of automatic holistic processing of faces and houses

Writing was invented too recently to have influenced the human genome. Consequently, reading acquisition must rely on partial recycling of pre-existing brain systems. Prior fMRI evidence showed that in literates a left-hemispheric visual region increases its activation to written strings relative to illiterates and reduces its response to faces. Increasing literacy also leads to a stronger right-hemispheric lateralization for faces. Here, we evaluated whether this reorganization of the brain's face system has behavioral consequences for the processing of non-linguistic visual stimuli. Three groups of adult illiterates, ex-illiterates and literates were tested with the sequential composite face paradigm that evaluates the automaticity with which faces are processed as wholes. Illiterates were consistently more holistic than participants with reading experience in dealing with faces. A second experiment replicated this effect with both faces and houses. Brain reorganization induced by literacy seems to reduce the influence of automatic holistic processing of faces and houses by enabling the use of a more analytic and flexible processing strategy, at least when holistic processing is detrimental to the task.

P 156. Deficient speech motor preparation in stuttering

Introduction Persistent developmental stuttering (PDS) is a speech fluency disorder that affects 1% of the population, predominantly males. Its etiology is unclear and likely multifactoral, with contributions from intrinsic factors pertaining to brain anatomy and neurophysiology, particularly abnormal right-hemispheric lateralization of blood flow in motor and premotor areas. Clinically, a major feature of stuttering is the paroxysmal inability to smoothly sequence articulatory gestures, resulting in frustraneous partial repetitions of the initial gestures. Objectives Attempting to further clarify the pathophysiology of the intermittent losses of motor control, we investigated changes in motor cortex excitability in the transition phase between articulatory gestures. We therefore studied speech-related modulation of excitability in the motor representation of the tongue. Materials and methods Thirteen fluent speakers and 13 adults who stutter were asked to build compound verbs with the verbal prefix “auf”. Single-pulse transcranial magnetic stimulation was applied over the primary motor cortex during the transition phase between a fixed labiodental articulatory configuration towards various articulatory configurations at five different latencies after transition onset. Bilateral electromyography was recorded from self-adhesive electrodes placed on the upper top of the tongue. Off-line, we extracted the motor evoked potential amplitudes and normalized these amplitudes to the individual baseline excitability during pronouncing of the prefix. Results Fluent-speaking control subjects showed a gradual increase of motor evoked potential amplitudes before the target articulatory gesture in the left motor cortex, and to a much lesser extent after stimulation of the right motor cortex. By contrast, stuttering adults lacked any premovement facilitation in the left motor cortex, but showed some premovement facilitation in the right motor cortex. Conclusion For decades theories of speech production postulate that the selection and the execution of speech units arise from facilitation of target units & inhibition of others. We present the first measurement of motor unit facilitation during speaking in real time. Excitability tuning of layer V pyramidal cell populations is quantified by MEP recordings from the tongue. Such data can guide the much needed integration of psycholinguistic and motor control approaches to speech production at a neurobiological level. Excitability tuning was absent in adults afflicted with PDS, indicating that the internal, speech-related signals triggering motor cortex facilitation were insufficient in strength or timing. This corroborates a disconnection hypothesis of speech-related brain areas in individuals suffering from PDS.

P 151. The right (but not the left) lateral occipital complex is causally implicated in visual mirror symmetry detection: An fMRI-guided TMS study

Despite the fact that bilateral mirror symmetry is an important characteristic of the visual world, few studies have investigated its neural basis. Here we addressed this issue by investigating whether the object-selective lateral occipital cortex (LO), a key brain region in object and shape processing, is causally involved in this kind of symmetry detection. Participants were asked to discriminate between symmetric and asymmetric dot patterns, while fMRI-guided repetitive TMS was delivered online over either the left LO, the right LO or two control sites in the occipital cortex. We found that the application of TMS over the right LO slowed down symmetry judgments, whereas stimulation of the left LO, or of two control sites, had no impact. Our results thus indicate that the right (but not the left) LO is causally implicated in symmetry detection. This finding may relate to the previously reported right-hemisphere lateralization of holistic processing of stimuli, including faces for which symmetry is a critical cue.

Simulating the neural correlates of stuttering

For functional neuroimaging studies of stuttering, two challenges are (1) the elicitation of naturally stuttered versus fluent speech and (2) the separation of activation associated with abnormal motor execution from activation that reflects the cognitive substrates of stuttering. This paper reports on a proof-of-concept study, in which a single-subject approach was applied to address these two issues. A stuttering speaker used his insight into his own stuttering behavior to create a list of stutter-prone words versus a list of “fluent” words. He was then matched to a non-stuttering speaker, who imitated the specific articulatory and orofacial motor pattern of the stuttering speaker. Both study participants performed a functional MRI experiment of single word reading, each being presented with the same lexical items. Results suggest that the generally observed right-hemisphere lateralization appears to reflect a true neural correlate of stuttering. Some of the classically reported activation associated with stuttering appears to be driven more by nonspecific motor patterns than by cognitive substrates of stuttering, while anterior cingulate activation may reflect awareness of (upcoming) dysfluencies. This study shows that it is feasible to match stuttering speakers’ utterances more closely to simulated stutters for the investigation of neural correlates of real stuttering. Significant main effects and contrast effects were obtained for the differences between fluent and stuttered speech, and right-hemisphere lateralization associated with real stuttered speech was shown in a single subject.

Does cerebral lateralization develop? A study using functional transcranial Doppler ultrasound assessing lateralization for language production and visuospatial memory

In the majority of people, language production is lateralized to the left cerebral hemisphere and visuospatial skills to the right. However, questions remain as to when, how, and why humans arrive at this division of labor. In this study, we assessed cerebral lateralization for language production and for visuospatial memory using functional transcranial Doppler ultrasound in a group of 60 typically developing children between the ages of six and 16 years. The typical pattern of left-lateralized activation for language production and right-lateralized activation for visuospatial memory was found in the majority of the children (58%). No age-related change in direction or strength of lateralization was found for language production. In contrast, the strength of lateralization (independent of direction) for visuospatial memory function continued to increase with age. In addition, boys showed a trend for stronger right-hemisphere lateralization for visuospatial memory than girls, but there was no gender effect on language laterality. We tested whether having language and visuospatial functions in the same hemisphere was associated with poor cognitive performance and found no evidence for this “functional crowding” hypothesis. We did, however, find that children with left-lateralized language production had higher vocabulary and nonword reading age-adjusted standard scores than other children, regardless of the laterality of visuospatial memory. Thus, a link between language function and left-hemisphere lateralization exists, and cannot be explained in terms of maturational change.

The neural correlates of impaired collision avoidance in hemianopic patients

The aim of this study was to assess the brain regions associated with impaired performance in a virtual, dynamic collision avoidance task, in a group of patients with homonymous visual field defects (HVFDs) because of unilateral vascular brain lesions. Overall task performance was quantitatively assessed as the number of collisions while crossing an intersection at two levels of traffic density. Twenty-six patients were divided into two subgroups using the median split method: patients with 'performance above average' (HVFD(A), i.e. lower number of collisions) and patients with 'performance below average' (HVFD(B), i.e. higher number of collisions). In order to identify the anatomical structures that might be specifically affected in HVFD(B) patients but spared in HVFD(A) patients, overlap, subtraction and voxel-based lesion-symptom mapping analyses were performed using the MRIcron software. No significant difference in collision avoidance between patients with left- and right-hemispheric lesions was revealed. Separate lesion analysis in 12 patients with right- and 14 patients with left-hemispheric lesions showed that the cortical structures associated with impaired collision avoidance were the parieto-occipital region and posterior cingulate gyrus in the right hemisphere and the inferior occipital cortex and parts of the fusiform (occipito-temporal) gyrus in the left hemisphere. In the present collision avoidance paradigm, impaired performance of patients with right-hemispheric lesions is associated with damage in the dorsal processing stream and potential impact on the visual spatial working memory (WM), while impaired performance of patients with left-hemispheric lesions is associated with damage in the ventral stream and potential impact on the visual object WM.

Left-handedness and language lateralization in children

This fMRI study investigated the development of language lateralization in left- and righthanded children between 5 and 18 years of age. Twenty-seven left-handed children (17 boys, 10 girls) and 54 age- and gender-matched right-handed children were included. We used functional MRI at 3 T and a verb generation task to measure hemispheric language dominance based on either frontal or temporo-parietal regions of interest (ROIs) defined for the entire group and applied on an individual basis. Based on the frontal ROI, in the left-handed group, 23 participants (85%) demonstrated left-hemispheric language lateralization, 3 (11%) demonstrated symmetric activation, and 1 (4%) demonstrated right-hemispheric lateralization. In contrast, 50 (93%) of the right-handed children showed left-hemispheric lateralization and 3 (6%) demonstrated a symmetric activation pattern, while one (2%) demonstrated a right-hemispheric lateralization. The corresponding values for the temporo-parietal ROI for the left-handed children were 18 (67%) left-dominant, 6 (22%) symmetric, 3 (11%) right-dominant and for the right-handed children 49 (91%), 4 (7%), 1 (2%), respectively. Left-hemispheric language lateralization increased with age in both groups but somewhat different lateralization trajectories were observed in girls when compared to boys. The incidence of atypical language lateralization in left-handed children in this study was similar to that reported in adults. We also found similar rates of increase in left-hemispheric language lateralization with age between groups (i.e., independent of handedness) indicating the presence of similar mechanisms for language lateralization in left- and right-handed children.

Holistic Processing and Right Hemisphere Lateralization Do Not Always Go Together—Evidence from Computational Modeling

Studies on face recognition have suggested a relationship between holistic processing and right hemisphere (RH) lateralization. Thus, it has long been assumed that holistic processing is a property of RH processing. Nevertheless, recent studies showed reduced holistic processing and increased RH lateralization in Chinese character recognition expertise, suggesting that these two effects may be separate processes. Through computational modeling, in which we implement a theory of hemispheric asymmetry in perception that posits a low spatial frequency bias in the RH and a high spatial frequency bias in the left hemisphere (i.e. the Double Filtering by Frequency Theory, Ivry & Robertson, 1998), here we show that when the recognition task relies purely on featural information, holistic processing increases whereas RH lateralization decreases with increasing stimulus similarity, and there is a negative correlation between them. In contrast, when the recognition task relies purely on configural information, although holistic processing also increases whereas RH lateralization decreases with increasing stimulus similarity, there is no correlation between them. This result suggests that holistic processing and RH lateralization are separate processes that can be influenced differentially by task requirements.

The effects of mothers’ past infant-holding preferences on their adult children’s face processing lateralisation

Face processing development is negatively affected when infants have not been exposed to faces for some time because of congenital cataract blocking all vision (Le Grand, Mondloch, Maurer, & Brent, 2001). It is not clear, however, whether more subtle differences in face exposure may also have an influence. The present study looked at the effect of the mother’s preferred side of holding an infant, on her adult child’s face processing lateralisation. Adults with a mother who had a left-arm preference for holding infants were compared with adults with a mother who had a right-arm holding preference. All participants were right-handed and had been exclusively bottle-fed during infancy. The participants were presented with two chimeric faces tests, one involving emotion and the other one gender. The left-arm held individuals showed a normal left-bias on the chimeric face tests, whereas the right-arm held individuals a significantly decreased left-bias. The results might suggest that reduced exposure to high quality emotional information on faces in infancy results in diminished right-hemisphere lateralisation for face processing.

Does a neuropsychological index of hemispheric lateralization predict onset of upper respiratory tract infectious symptoms?

Past studies demonstrate relationships between hemispheric lateralization (HL) and immunity. However, the relevance of HL-immune relationships to health and illness has rarely been investigated. This study tested whether a neuropsychological index of right-hemispheric lateralization (right-HL) predicts development of upper respiratory tract infectious (URTI) symptoms. We used a prospective, matched, case-control design. Initially, 80 URTI symptom free adults underwent neuropsychological assessment including right-HL (picture vs. word recognition), and were then followed-up during 10 weeks for development of URTI symptoms and objective signs of URTI. Participants reporting URTI symptoms (Ill; N=21) were matched on age, gender, and IQ with 21 participants remaining well. At baseline, the right-HL index was significantly higher in participants who later became ill (9.9%) compared to well participants (3.9%, p<.05). Health behaviour also predicted URTI symptoms. In a logistic regression, right-HL significantly predicted self-reported URTI, independent of health behaviour and neuroticism. Greater right-HL predicted URTI symptom development during follow-up, independent of important confounders. These findings expand previous HL-immune relationships to a common immune-related illness.

Hemispheric Asymmetries during Processing of Immoral Stimuli

Evolutionary approaches to dissecting our psychological architecture underscore the importance of both function and structure. Here we focus on both the function and structure of our neural circuitry and report a functional bilateral asymmetry associated with the processing of immoral stimuli. Many processes in the human brain are associated with functional specialization unique to one hemisphere. With respect to emotions, most research points to right-hemispheric lateralization. Here we provide evidence that not all emotional stimuli share right-hemispheric lateralization. Across three studies employing different paradigms, the processing of negative morally laden stimuli was found to be highly left-lateralized. Regions of engagement common to the three studies include the left medial prefrontal cortex, left temporoparietal junction, and left posterior cingulate. These data support the hypothesis that processing of immoral stimuli preferentially engages left hemispheric processes and sheds light on our evolved neural architecture.

Muscarinic antagonist effects on executive control of attention

Acetylcholine plays a major role in mediating attention processes. We investigated the muscarinic antagonist effect of scopolamine on functional neuro-anatomy of attention and cognition. We assessed 12 healthy volunteers while performing the Attention Network Task on 0.4 mg scopolamine and placebo in a single-blind randomized trial in a 1.5 T magnetic resonance scanner. Neurocognitive measures included verbal learning, verbal memory, verbal fluency, trail making, digit span, a continuous performance task and a planning task (Tower of London). When compared to placebo, scopolamine increased reaction times for conflicting stimulus processing, together with decreasing brain activation in the anterior cingulate cortex (a brain region involved in conflict processing) suggestive of a muscarinic antagonist effect on executive control of attention. Contrary to the notion of a predominantly right-hemispheric lateralization of cognitive processes associated with orienting attention, scopolamine reduced brain activity in left superior and left middle frontal brain areas. Our neuropsychological test data revealed a selective effect of scopolamine on verbal learning and memory while other cognitive domains, such as planning and working memory, were unaffected. These findings are consistent with muscarinic modulation of dopaminergic neurotransmission in frontal attention networks when processing conflicting information.

17. Right-hemispheric lateralization during explicit somatosensory shape discrimination

17. Right-hemispheric lateralization during explicit somatosensory shape discrimination