Brain activation during mental rotation in school children and adults

Exploring relative strengths in people with Down syndrome: Spatial thinking and its role in mathematics

There is convincing evidence that training spatial abilities leads to improved mathematics performance in typically developing (TD) children. However, a lack of information on mathematical development and spatial-mathematical associations in people with Down syndrome (DS) hinders the translation of these interventions. Here, we established developmental trajectories of mathematics and explored whether spatial ability predicts attainment on different mathematics measures in individuals with DS. Participants with DS (n = 36; ages 9-35 years) and TD children (n = 132; ages 4-11 years) completed three groups of tasks: spatial tasks assessing different subdomains of spatial thinking; mathematics tasks assessing early mathematics skills, mathematical reasoning, arithmetic, and geometry; and IQ tasks. The developmental trajectories of mathematics performance against mental age revealed similar starting points of the trajectories and similar rates of development for DS and TD groups. Furthermore, after controlling for verbal skills, spatial skills explained 5.8% to 18.1% of the variation in mathematical performance across different mathematics tasks, and the pattern of spatial-mathematical relations was similar for DS and mental age-matched TD groups. This shows that mathematical development in DS groups appears to mirror that in TD children, indicative of delay only. Strong spatial-mathematical relations were observed for individuals with DS, like those seen for TD participants. This is the vital preliminary knowledge needed to support the design and use of spatial intervention for improving mathematics in individuals with DS.

Imaging the Spin: Disentangling the Core Processes Underlying Mental Rotation by Network Mapping of Data From Meta-analysis

Research on the mental rotation task has sparked debate regarding the specific processes that underly the capability of humans to mentally rotate objects. The spread of reported brain activations suggests that mental rotation is subserved by a neural network circle. However, no common network has yet been found that uncovers the crucial processes underlying this ability. We aimed to identify the common network crucial for mental rotation by coordinate-based network mapping of previous neuroimaging findings in mental rotation. A meta-analysis revealed 710 peak activation coordinates from 42 fMRI studies in mental rotation, which include a total 844 participants. The coordinates were mapped to a normative functional connectome (n = 1000) to identify a network of connected regions. To account for experimental factors, we examined this network against two control tasks, action imitation and symbolic number processing. A common and crucial network for mental rotation, centring on dorsal premotor, superior parietal and inferior temporal lobes was revealed. This network, separated from other experimental aspects, suggests that the crucial processes underlying mental rotation are motor rotation, visuospatial processing, and higher order visual object recognition.

Task‐related functional neuroimaging contribution to sex/gender differences in cognition and emotion during development

Recent research has shown that sex/gender (s/g) influences on cognitive functions and related brain anatomy, functional responses, and connectivity are less clear than previously assumed, and most studies investigated adult population. In this mini-review, we summarize research progress in the study of s/g differences in the human brain function as investigated by neuroimaging methods adopting a developmental perspective. In particular, we review original studies published from 2000 to 2021 investigating s/g differences in task-related brain functional activation and connectivity in healthy children and adolescents. We summarize results about studies in the domains of language, visuospatial ability, social cognition, and executive functions. Overall, a clear relation between cognition and brain activation or connectivity pattern is far from being established and the few coherent results should be considered exploratory, despite in some cases, brain function seems to present specific patterns in comparison with what reported in adults. Moreover, future studies should address methodological limitations, such as fragmentation of tasks, lack of control for confounding variables, and lack of longitudinal designs to study developmental trajectories.

Mental Rotation Skill Shapes Haptic Exploration Strategies

Haptic exploration strategies have been traditionally studied focusing on hand movements and neglecting how objects are moved in space. However, in daily life situations touch and movement cannot be disentangled. Furthermore, the relation between object manipulation as well as performance in haptic tasks and spatial skill is still little understood. In this study, we used iCube, a sensorized cube recording its orientation in space as well as the location of the points of contact on its faces. Participants had to explore the cube faces where little pins were positioned in varying number and count the number of pins on the faces with either even or odd number of pins. At the end of this task, they also completed a standard visual mental rotation test (MRT). Results showed that higher MRT scores were associated with better performance in the task with iCube both in term of accuracy and exploration speed and exploration strategies associated with better performance were identified. High performers tended to rotate the cube so that the explored face had the same spatial orientation (i.e., they preferentially explored the upward face and rotated iCube to explore the next face in the same orientation). They also explored less often twice the same face and were faster and more systematic in moving from one face to the next. These findings indicate that iCube could be used to infer subjects' spatial skill in a more natural and unobtrusive fashion than with standard MRTs.

Developmental changes in neural lateralization for visual-spatial function: Evidence from a line-bisection task

Studies of hemispheric specialization have traditionally cast the left hemisphere as specialized for language and the right hemisphere for spatial function. Much of the supporting evidence for this separation of function comes from studies of healthy adults and those who have sustained lesions to the right or left hemisphere. However, we know little about the developmental origins of lateralization. Recent evidence suggests that the young brain represents language bilaterally, with 4-6-year-olds activating the left-hemisphere regions known to support language in adults as well as homotopic regions in the right hemisphere. This bilateral pattern changes over development, converging on left-hemispheric activation in late childhood. In the present study, we ask whether this same developmental trajectory is observed in a spatial task that is strongly right-lateralized in adults-the line bisection (or "Landmark") task. We examined fMRI activation among children ages 5-11 years as they were asked to judge which end of a bisected vertical line was longer. We found that young children showed bilateral activation, with activation in the same areas of the right hemisphere as has been shown among adults, as well as in the left hemisphere homotopic regions. By age 10, activation was right-lateralized. This strongly resembles the developmental trajectory for language, moving from bilateral to lateralized activation. We discuss potential underlying mechanisms and suggest that understanding the development of lateralization for a range of cognitive functions can play a crucial role in understanding general principles of how and why the brain comes to lateralize certain functions.

Development of bilateral parietal activation for complex visual-spatial function: Evidence from a visual-spatial construction task

The neural representation of visual-spatial functions has traditionally been ascribed to the right hemisphere, but little is known about these representations in children, including whether and how lateralization of function changes over the course of development. Some studies suggest bilateral activation early in life that develops toward right-lateralization in adulthood, while others find evidence of right-hemispheric dominance in both children and adults. We used a complex visual-spatial construction task to examine the nature of lateralization and its developmental time course in children ages 5-11 years. Participants were shown two puzzle pieces and were asked whether the pieces could fit together to make a square; responses required either mental translation of the pieces (Translation condition) or both mental translation and rotation of the pieces (Rotation condition). Both conditions were compared to a matched Luminance control condition that was similar in terms of visual content and difficulty but required no spatial analysis. Group and single-subject analyses revealed that the Rotation and Translation conditions elicited strongly bilateral activation in the same parietal and occipital locations as have been previously found for adults. These findings show that visual-spatial construction consistently elicits robust bilateral activation from age 5 through adulthood. This challenges the idea that spatial functions are all right-lateralized, either during early development or in adulthood. More generally, these findings provide insights into the developmental course of lateralization across different spatial skills and how this may be influenced by the computational requirements of the particular functions involved.

Sexually dimorphic development in the cortical oscillatory dynamics serving early visual processing

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Visual processing dynamics continue to develop throughout childhood and adolescence.

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Visual alpha response power differed between males and females.

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Sex and age interacted to modulate visual gamma responses.

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Peak frequency predicted response power above and beyond the effects of age and sex.

Successful interaction with one’s visual environment is paramount to developing and performing many basic and complex mental functions. Although major aspects of visual development are completed at an early age, other structural and functional components of visual processing appear to be dynamically changing across a much more protracted period extending into late childhood and adolescence. However, the underlying neurophysiological changes and cortical oscillatory dynamics that support maturation of the visual system during this developmental period remain poorly understood. The present study utilized magnetoencephalography (MEG) to investigate maturational changes in the neural dynamics serving basic visual processing during childhood and adolescence (ages 9–15, n = 69). Our key results included robust sex differences in alpha oscillatory activity within the left posterior parietal cortex, and sex-by-age interactions in gamma activity in the right lingual gyrus and superior parietal lobule. Hierarchical regression revealed that the peak frequency of both the alpha and gamma responses predicted response power in parietal regions above and beyond the noted effects of age and sex. These findings affirm the view that neural oscillations supporting visual processing develop over a much more protracted period, and illustrate that these maturational trajectories are influenced by numerous elements, including age, sex, and individual variation.

Dump the "dimorphism": Comprehensive synthesis of human brain studies reveals few male-female differences beyond size

With the explosion of neuroimaging, differences between male and female brains have been exhaustively analyzed. Here we synthesize three decades of human MRI and postmortem data, emphasizing meta-analyses and other large studies, which collectively reveal few reliable sex/gender differences and a history of unreplicated claims. Males' brains are larger than females' from birth, stabilizing around 11 % in adults. This size difference accounts for other reproducible findings: higher white/gray matter ratio, intra- versus interhemispheric connectivity, and regional cortical and subcortical volumes in males. But when structural and lateralization differences are present independent of size, sex/gender explains only about 1% of total variance. Connectome differences and multivariate sex/gender prediction are largely based on brain size, and perform poorly across diverse populations. Task-based fMRI has especially failed to find reproducible activation differences between men and women in verbal, spatial or emotion processing due to high rates of false discovery. Overall, male/female brain differences appear trivial and population-specific. The human brain is not "sexually dimorphic."

Neural Correlates of Mental Rotation in Preschoolers With High or Low Working Memory Capacity: An fNIRS Study

This study explored the differentiated neural correlates of mental rotation (MR) in preschoolers with high and low working memory capacity using functional near-infrared spectroscopy (fNIRS). Altogether 38 Chinese preschoolers (M = 5.0 years, SD = 0.69 years) completed the Working Memory Capacity (WMC) test, the Mental Rotation (MR), and its Control tasks (without MR). They were divided into High-WMC (N₁ = 9) and Low-WMC (N₂ = 18) groups based on the WMC scores. The behavioral and fNIRS results indicated that: (1) there were no significant differences in MR task performance between the High-WMC (M_mr = 23.44, SD = 0.88) and Low-WMC group (M_mr = 23.67, SD = 0.59); (2) the Low-WMC group activated BA6, BA8, BA 9, and BA 44, whereas the High-WMC group activated BA8, BA10 and BA 44 during mental rotation; (3) significant differences were found in the activation of BA44 and BA9 between the High-WMC and Low-WMC groups during mental rotation; and (4) the High-WMC and Low-WMC groups differed significantly in the activation of BA 9 and BA10 during the control tasks, indicating that both areas might be responsible for the group differences in working memory.

Sex differences and brain development during puberty and adolescence

Sex differences in behavior, and whether these behavioral differences are related to sex differences in brain development, has been a longstanding topic of debate. Presumably, sex differences can provide critically important leads for explaining the etiology of various illnesses that show (i) large sex differences in prevalence and (ii) have an origin before or during adolescence. The general aim of this chapter is to provide an overview of scientific studies on sex differences in normative brain and behavioral development across puberty and adolescence, including the (sex) hormone-driven transition phase of puberty. Moreover, we describe the literature on brain and behavioral development in gender dysphoria, a severe and persistent incongruence between the self-identified gender and the assigned sex at birth. From the literature it becomes clear there is evidence for a specific link between pubertal maturation and developmental changes in arousal, motivation, and emotion. However, this link is rather similar between boys and girls. Moreover, although there is substantial evidence for sex differences in mean brain structure, these have not always been linked to sex differences in behavior, cognition, or psychopathology. Furthermore, there is little evidence for sex differences in brain development and thus, studies so far have been unable to explain sex differences in cognition. Suggestions for future research and methodologic considerations are provided.

Shared and Distinct Neural Bases of Large- and Small-Scale Spatial Ability: A Coordinate-Based Activation Likelihood Estimation Meta-Analysis

Background: Spatial ability is vital for human survival and development. However, the relationship between large-scale and small-scale spatial ability remains poorly understood. To address this issue from a novel perspective, we performed an activation likelihood estimation (ALE) meta-analysis of neuroimaging studies to determine the shared and distinct neural bases of these two forms of spatial ability. Methods: We searched Web of Science, PubMed, PsycINFO, and Google Scholar for studies regarding "spatial ability" published within the last 20 years (January 1988 through June 2018). A final total of 103 studies (Table 1) involving 2,085 participants (male = 1,116) and 2,586 foci were incorporated into the meta-analysis. Results: Large-scale spatial ability was associated with activation in the limbic lobe, posterior lobe, occipital lobe, parietal lobe, right anterior lobe, frontal lobe, and right sub-lobar area. Small-scale spatial ability was associated with activation in the parietal lobe, occipital lobe, frontal lobe, right posterior lobe, and left sub-lobar area. Furthermore, conjunction analysis revealed overlapping regions in the sub-gyrus, right superior frontal gyrus, right superior parietal lobule, right middle occipital gyrus, right superior occipital gyrus, left inferior occipital gyrus, and precuneus. The contrast analysis demonstrated that the parahippocampal gyrus, left lingual gyrus, culmen, right middle temporal gyrus, left declive, left superior occipital gyrus, and right lentiform nucleus were more strongly activated during large-scale spatial tasks. In contrast, the precuneus, right inferior frontal gyrus, right precentral gyrus, left inferior parietal lobule, left supramarginal gyrus, left superior parietal lobule, right inferior occipital gyrus, and left middle frontal gyrus were more strongly activated during small-scale spatial tasks. Our results further indicated that there is no absolute difference in the cognitive strategies associated with the two forms of spatial ability (egocentric/allocentric). Conclusion: The results of the present study verify and expand upon the theoretical model of spatial ability proposed by Hegarty et al. Our analysis revealed a shared neural basis between large- and small-scale spatial abilities, as well as specific yet independent neural bases underlying each. Based on these findings, we proposed a more comprehensive version of the behavioral model.

Age and Sex Differences in Verbal and Visuospatial Abilities

In order to explore the developmental patterns of sex differences in verbal and visuospatial abilities, the present study investigated sex differences in various cognitive abilities among children and adults. Three hundred and twenty-six children and adults completed a battery of six cognitive tasks testing two sets of abilities: The verbal cognitive battery tested verbal fluency and short-term memory tasks. The visuospatial battery tested mental rotation, localization, and form-completion tasks. Results showed a significant Sex × Age interaction on the mental rotation task, with men outperforming women in the 3D task, but with no sex differences shown in childhood in the 2D task. Sex differences in verbal fluency were found, with girls and women outperforming boys and men in this task. Findings are discussed within an integrative approach of biological as well as environmental factors.

Laterality-Specific Training Improves Mental Rotation Performance in Young Soccer Players

This study investigates the influence of specific soccer training with the non-dominant leg on mental rotation performance of 20 adolescent soccer players between 10 and 11 years of age. While the experimental group performed soccer specific tasks only with the non-dominant foot once a week for 10 weeks, the control group absolved the same exercises with the dominant foot for the same period of time. Both groups performed a mental rotation task and shot, dribbling and ball control tests before and after the 10 week intervention. The most relevant result was that the experimental group showed a significantly larger increase in mental rotation ability than the control group.

Heterogeneity of Developmental Dyscalculia: Cases with Different Deficit Profiles

Developmental Dyscalculia (DD) has long been thought to be a monolithic learning disorder that can be attributed to a specific neurocognitive dysfunction. However, recent research has increasingly recognized the heterogeneity of DD, where DD can be differentiated into subtypes in which the underlying cognitive deficits and neural dysfunctions may differ. The aim was to further understand the heterogeneity of developmental dyscalculia (DD) from a cognitive psychological perspective. Utilizing four children (8–9 year-old) we administered a comprehensive cognitive test battery that shed light on the cognitive-behavioral profile of each child. The children were compared against norm groups of aged-matched peers. Performance was then contrasted against predominant hypotheses of DD, which would also give insight into candidate neurocognitive correlates. Despite showing similar mathematical deficits, these children showed remarkable interindividual variability regarding cognitive profile and deficits. Two cases were consistent with the approximate number system deficit account and also the general magnitude-processing deficit account. These cases showed indications of having domain-general deficits as well. One case had an access deficit in combination with a general cognitive deficit. One case suffered from general cognitive deficits only. The results showed that DD cannot be attributed to a single explanatory factor. These findings support a multiple deficits account of DD and suggest that some cases have multiple deficits, whereas other cases have a single deficit. We discuss a previously proposed distinction between primary DD and secondary DD, and suggest hypotheses of dysfunctional neurocognitive correlates responsible for the displayed deficits.

Male-typical visuospatial functioning in gynephilic girls with gender dysphoria - organizational and activational effects of testosterone

BACKGROUND

Sex differences in performance and regional brain activity during mental rotation have been reported repeatedly and reflect organizational and activational effects of sex hormones. We investigated whether adolescent girls with gender dysphoria (GD), before and after 10 months of testosterone treatment, showed male-typical brain activity during a mental rotation task (MRT).

METHODS

Girls with GD underwent fMRI while performing the MRT twice: when receiving medication to suppress their endogenous sex hormones before onset of testosterone treatment, and 10 months later during testosterone treatment. Two age-matched control groups participated twice as well.

RESULTS

We included 21 girls with GD, 20 male controls and 21 female controls in our study. In the absence of any group differences in performance, control girls showed significantly increased activation in frontal brain areas compared with control boys (p_FWE = 0.012). Girls with GD before testosterone treatment differed significantly in frontal brain activation from the control girls (p_FWE = 0.034), suggesting a masculinization of brain structures associated with visuospatial cognitive functions. After 10 months of testosterone treatment, girls with GD, similar to the control boys, showed increases in brain activation in areas implicated in mental rotation.

LIMITATIONS

Since all girls with GD identified as gynephilic, their resemblance in spatial cognition with the control boys, who were also gynephilic, may have been related to their shared sexual orientation rather than their shared gender identity. We did not account for menstrual cycle phase or contraceptive use in our analyses.

CONCLUSION

Our findings suggest atypical sexual differentiation of the brain in natal girls with GD and provide new evidence for organizational and activational effects of testosterone on visuospatial cognitive functioning.

Effects of Stimulus Type and Strategy on Mental Rotation Network: An Activation Likelihood Estimation Meta-Analysis

We can predict how an object would look like if we were to see it from different viewpoints. The brain network governing mental rotation (MR) has been studied using a variety of stimuli and tasks instructions. By using activation likelihood estimation (ALE) meta-analysis we tested whether different MR networks can be modulated by the type of stimulus (body vs. non-body parts) or by the type of tasks instructions (motor imagery-based vs. non-motor imagery-based MR instructions). Testing for the bodily and non-bodily stimulus axis revealed a bilateral sensorimotor activation for bodily-related as compared to non-bodily-related stimuli and a posterior right lateralized activation for non-bodily-related as compared to bodily-related stimuli. A top-down modulation of the network was exerted by the MR tasks instructions with a bilateral (preferentially sensorimotor left) network for motor imagery- vs. non-motor imagery-based MR instructions and the latter activating a preferentially posterior right occipito-temporal-parietal network. The present quantitative meta-analysis summarizes and amends previous descriptions of the brain network related to MR and shows how it is modulated by top-down and bottom-up experimental factors.

[fMRI and DTI in delayed development of number processing]

The neuronal correlate of the current cultural performance arose from developmental processes that can be observed by functional and anatomical magnetic resonance imaging. The velocity of these maturation processes occurs differently between adolescents, causing implications for both school career and academic performance. Regarding spatial-numerical cognition the myelinization of the superior longitudinal bundle appears to be crucial because this fiber connection intermediates between the linguistic nature of number words and conception of their spatial-numerical magnitude. The neuroscientific observation of anatomical brain maturation and its influence on school-relevant number processing may be helpful for educational purposes as well as for school psychology.

Neurocognitive impairment of mental rotation in major depressive disorder: evidence from event-related brain potentials

Mental rotation performance may be used as an index of mental slowing or bradyphrenia and may reflect speed of motor preparation. Previous studies suggest that major depressive disorder (MDD) presents correlates of impaired behavioral performance for mental rotation and psychomotor disturbance. Very little is known about the electrophysiological mechanism underlying this deficit. The present study was the first to investigate the event-related brain potential (ERP) correlates of mental rotation and their mental slowing or bradyphrenia in MDD. ERPs were recorded while we tested 25 MDD patients and 26 healthy controls by evaluating the performance of MDD patients on hand and letter rotation tasks at different orientations, and their 400-to-600-msec time window was measured and analyzed for latencies and peak amplitudes over the electrodes. First, individuals with MDD were slower and made more errors in mentally rotating hands and letters than healthy controls did, and individuals with MDD exhibited a greater difference in response times and errors than controls did between hands and letters. Second, the mean peak amplitude was significantly lower and the mean latency was significantly longer in the 400-to-600-msec time window at the parietal site in the hand tasks in MDD patients than in controls, but this was not seen in the letter task, with only lower mean peak amplitude. MDD patients present the absence of a typical mental rotation function for the amplitude of the rotation-related negativity in the hand and letter tasks. Third, the scalp activity maps in MDD patients exhibited the absence of activation in the left parietal site for the mental rotation of hands, as shown in healthy participants. In contrast, their brain activation for the letter task was similar to those of healthy participants. These data suggest that mental imagery of hands and letters relies on different cognitive and neural mechanisms and indicate that the left posterior parietal lobe is a necessary structure for mental transformations of human hands. Importantly, MDD deficits were more seriously present specific to the hands than the letters. Such impairment may also be an important and possibly defining marker of MDD in particular.

Development of magnitude processing in children with developmental dyscalculia: space, time, and number

Developmental dyscalculia (DD) is a learning disorder associated with impairments in a preverbal non-symbolic approximate number system (ANS) pertaining to areas in and around the intraparietal sulcus (IPS). The current study sought to enhance our understanding of the developmental trajectory of the ANS and symbolic number processing skills, thereby getting insight into whether a deficit in the ANS precedes or is preceded by impaired symbolic and exact number processing. Recent work has also suggested that humans are endowed with a shared magnitude system (beyond the number domain) in the brain. We therefore investigated whether children with DD demonstrated a general magnitude deficit, stemming from the proposed magnitude system, rather than a specific one limited to numerical quantity. Fourth graders with DD were compared to age-matched controls and a group of ability-matched second graders, on a range of magnitude processing tasks pertaining to space, time, and number. Children with DD displayed difficulties across all magnitude dimensions compared to age-matched peers and showed impaired ANS acuity compared to the younger, ability-matched control group, while exhibiting intact symbolic number processing. We conclude that (1) children with DD suffer from a general magnitude-processing deficit, (2) a shared magnitude system likely exists, and (3) a symbolic number-processing deficit in DD tends to be preceded by an ANS deficit.

Clozapine and visuospatial processing in treatment-resistant schizophrenia

INTRODUCTION

Clozapine, the most widely used option in treatment-resistant schizophrenia, has been shown to be superior to other antipsychotic medications in improving cognitive function in patients. However, the results have not been consistent and the mechanisms underlying this effect have not been elucidated. Thus, the purpose of the present study was to evaluate verbal and nonverbal cognition (using visuospatial processing tests) in patients treated with clozapine (initially treatment resistant) and those treated with other second-generation antipsychotics, relative healthy control subjects. Furthermore, we examined neural correlates of visuospatial processing in the three groups.

METHODS

Twenty schizophrenia patients treated with clozapine (TR-C group), 23 patients stabilised with atypical antipsychotics other than clozapine (NTR group), and 21 healthy control participants completed a battery of verbal and visuospatial cognitive tests. In addition, participants underwent functional magnetic resonance imaging (fMRI) while performing one of the visuospatial tests (the mental rotation task). The fMRI data were analysed separately in each group using Statistical Parametric Mapping software (SPM5).

RESULTS

Overall, schizophrenia patients exhibited deficit on verbal and nonverbal processing relative to the healthy controls, but we observed some interesting differences between the two groups of patients. Specifically, the NTR group performed better than the TR-C group on the Block Design and the Raven's Progressive Matrices. With respect to brain function during mental rotation, the NTR group showed significant activations in regions of the temporal and occipital cortex, whereas the TR-C patients did not. The relative deactivations associated with the task were also more robust in NTR compared to the other group of patients, despite a similar performance.

CONCLUSION

Present results suggest better visuospatial processing in the NTR relative to the TR-C group. This difference could be attributed to the treatment resistance itself or a lack of beneficial effect of clozapine relative to other atypical antipsychotics in ameliorating nonverbal abilities. Future studies of the relationship between clozapine and cognition, as well as between treatment resistance and cognition, are warranted.

The association between the disruption of motor imagery and the number of depressive episodes of major depression

BACKGROUND

Mental rotation performance may be used as an index of mental slowing or bradyphrenia, and may reflect, in particular, speed of motor preparation. Previous studies suggest depressive patients present the correlates of impaired behavioural performance for mental rotation and psychomotor disturbance. The aim of this study is to compare the mental rotation abilities of patients with a first episode of depression, recurrent depression and healthy control subjects with regard to hand tasks.

METHODS

We tested 32 first episode of depression, 38 recurrent depression and 36 healthy control subjects by evaluating the performance of depressed patients with regard to the hand mental rotation tasks.

RESULTS

First, the first episode and recurrent depression subjects were significantly slower and made more errors than controls in mentally rotating hands. Second, the first depressive episode but not the recurrent depression displayed the same pattern of response times to stimuli at various orientations relative to control subjects in the hand task. Third, in particular, recurrent depression subjects were significantly slower and made more errors during the mental transformation of hands than first depressive episode relative to control subjects and the differences were significantly larger in female than male subjects in the mental rotation hand task.

LIMITATIONS

Patients were on antidepressant medication.

CONCLUSIONS

These results suggest that the impaired behavioural performance for mental representation processing are related to the number of previous episodes. Moreover, the recurrent major depressive episodes may contribute to the reinforcement of cognitive impairments and further the development or maintenance of mental representation dysfunctions, especially in female patients. A deficit on mental rotation in the depressive patients may be potential biomarkers for recurrence chronically.

Ego-rotation and object-rotation in major depressive disorder

Mental rotation (MR) performance provides a direct insight into a prototypical higher-level visuo-spatial cognitive operation. Previous studies suggest that progressive slowing with an increasing angle of orientation indicates a specific wing of object-based mental transformations in the psychomotor retardation that occurs in major depressive disorder (MDD). It is still not known, however, whether the ability of object-rotation is associated with the ability of ego-rotation in MDD. The present study was designed to investigate the level of impairment of mental transformation abilities in MDD. For this purpose we tested 33 MDD (aged 18-52 years, 16 women) and 30 healthy control subjects (15 women, age and education matched) by evaluating the performance of MDD subjects with regard to ego-rotation and object-rotation tasks. First, MDD subjects were significantly slower and made more errors than controls in mentally rotating hands and letters. Second, MDD and control subjects displayed the same pattern of response times to stimuli at various orientations in the letter task but not the hand task. Third, in particular, MDD subjects were significantly slower and made more errors during the mental transformation of hands than letters relative to control subjects and were significantly slower and made more errors in physiologically impossible angles than physiologically possible angles in the mental rotation hand task. In conclusion, MDD subjects present with more serious mental rotation deficits specific to the hand than the letter task. Importantly, deficits were more present during the mental transformation in outward rotation angles, thus suggesting that the mental imagery for hands and letters relies on different processing mechanisms which suggest a module that is more complex for the processing of human hands than for letters during mental rotation tasks. Our study emphasises the necessity of distinguishing different levels of impairment of action in MDD subjects.

Sex differences during humor appreciation in child-sibling pairs

The developmental origin of sex differences in adult brain function is poorly understood. Elucidating neural mechanisms underlying comparable cognitive functionality in both children and adults is required to address this gap. Humor appreciation represents a particularly relevant target for such developmental research because explanatory theories apply across the life span, and underlying neurocircuitry shows sex differences in adults. As a positive mood state, humor is also of interest due to sex differences in rates of depression, a disorder afflicting twice as many women as men. In this study, we employed functional magnetic resonance imaging (fMRI) to investigate brain responses to funny versus positive (and neutral) video clips in 22 children, ages 6-13 years, including eight sibling-pairs. Our data revealed increased activity to funny clips in bilateral temporo-occipital cortex, midbrain, and amygdala in girls. Conversely, we found heightened activation to positive clips in bilateral inferior parietal lobule, fusiform gyrus, inferior frontal gyrus, amygdala, and ventromedial prefrontal cortex in boys. Many of these effects persisted when looking at sibling-pairs only. We interpret such findings as reflecting the presence of early sex divergence in reward saliency or expectation and stimulus relevance attribution. These findings are discussed in the context of evolutionary and developmental theories of humor function.

Rearranging the world: neural network supporting the processing of temporal connectives

Temporal connectives (before/after) give us the freedom to describe a sequence of events in different orders. Studies have suggested that 'before-initiating' sentences, in which events are expressed in an order inconsistent with their actual order of occurrence, might need additional computation(s) during comprehension. The results of independent component analysis suggest that these computations are supported by a neural network connecting the bilateral caudate nucleus with the right middle frontal gyrus, left precentral gyrus, bilateral parietal lobule and inferior temporal gyrus. Among those regions, the caudate nucleus and the left middle frontal gyrus showed greater activations for 'before' than 'after' sentences. The functional network observed in this study may support sequence learning and processing in a general sense.

Disturbed sexual dimorphism of brain activation during mental rotation in schizophrenia

BACKGROUND

Sex differences in visuo-spatial abilities have been well documented in the general population, but there are only a few inconsistent reports in schizophrenia. The purpose of the present study was to examine potential sex differences in performance and pattern of brain activations during mental rotation in schizophrenia patients relative to control participants.

METHODS

Thirty three schizophrenia patients (17 women and 16 men) were compared to thirty five healthy control participants (17 women and 18 men), while performing a classic mental rotation task (3-D figures). Blood oxygen level dependent (BOLD) echo-planar images were acquired on a 3-Tesla Siemens TRIO system. Random-effect analyses were performed using SPM5 (UK Wellcome Institute).

RESULTS

Behavioural data revealed a diagnosis-by-sex interaction with healthy men (HM) performing significantly better than schizophrenia men (SZ-M) and no significant difference between healthy women (HW) and schizophrenia women (SZ-W). fMRI results revealed an overall similar pattern of extensive cerebral activations (in the parietal and lateral prefrontal cortex) and deactivations (in the medial prefrontal cortex) in HM and SZ-W during performance of the mental rotation versus control task. In contrast, both HW and SZ-M showed much more restricted activations and no significant deactivations.

CONCLUSIONS

Sex differences in performance and cerebral activations during mental rotation in schizophrenia patients deviated significantly from what we observed in healthy volunteers. This finding supports and extends existing evidence of a disturbed sexual dimorphism in schizophrenia. Moreover, the results emphasize the importance of including both sexes in neurocognitive and neuroimaging studies of schizophrenia.

Developmental sex differences in basic visuospatial processing: differences in strategy use?

Functional neuroimaging studies investigating sex differences in visuospatial processing traditionally focus on mental rotation tasks in adults, as it is a consistently robust finding, with a limited number of studies examining tasks tapping visuospatial skills at a more basic level. Furthermore, fewer studies have examined this issue in conjunction with investigating whether differences exist in younger populations. Therefore, functional neuroimaging was used to examine whether sex-based differences exist and/or develop during childhood. Thirty-two participants, matched on performance, participated in this study. Overall, both groups showed overlapping activation in bilateral superior parietal lobe, extrastriate cortex, and cerebellum; differences between the sexes showed that males had significantly greater activation in right lingual gyrus and cerebellum. Formal comparisons between age groups revealed that older males show engagement of left hemisphere regions, while females show greater bilateral (R>L) engagement of regions traditionally associated with visuospatial processing. Together, these results suggest that older males, as compared to younger males, may engage regions that are associated with a visuomotor network, whereas females utilize areas indicated in spatial attention and working memory. Furthermore, these results could also suggest that there may be differences in strategy use that are evident early on and may continue to develop over time evident by differential engagement of networks associated with visuospatial processing. Our data provide evidence for sex-based differences in the neural basis of visuospatial processing.

Early category-specific cortical activation revealed by visual stimulus inversion

Visual categorization may already start within the first 100-ms after stimulus onset, in contrast with the long-held view that during this early stage all complex stimuli are processed equally and that category-specific cortical activation occurs only at later stages. The neural basis of this proposed early stage of high-level analysis is however poorly understood. To address this question we used magnetoencephalography and anatomically-constrained distributed source modeling to monitor brain activity with millisecond-resolution while subjects performed an orientation task on the upright and upside-down presented images of three different stimulus categories: faces, houses and bodies. Significant inversion effects were found for all three stimulus categories between 70-100-ms after picture onset with a highly category-specific cortical distribution. Differential responses between upright and inverted faces were found in well-established face-selective areas of the inferior occipital cortex and right fusiform gyrus. In addition, early category-specific inversion effects were found well beyond visual areas. Our results provide the first direct evidence that category-specific processing in high-level category-sensitive cortical areas already takes place within the first 100-ms of visual processing, significantly earlier than previously thought, and suggests the existence of fast category-specific neocortical routes in the human brain.

Impaired imagery for upper limbs

The brain processes associated with mental imagery have long been a matter of debate. Neuroimaging and neuropsychological studies have yielded diverging evidence of mental transformation activating the right hemisphere, the left hemisphere, or both. Here, using a mirror/normal discrimination task with rotated body parts (BPs) and external objects (EOs), we describe the case of a patient who developed a selective deficit in mental imagery of such BPs due to left posterior parietal brain damage. In addition, the patient's deficit predominated for pictures of right arms (i.e., arms corresponding to the patient's imagined contralesional arm) and was further characterised by an inability to distinguish between anatomically possible and impossible arm positions. This neuropsychological deficit was corroborated by neuroimaging evidence revealing the absence of activation in the left parietal lobe for the mental rotation of body parts as shown in healthy participants. In contrast, his behavioural performance and brain activation for EOs were similar to those of healthy participants. These data suggest that mental imagery of BPs and EOs relies on different cognitive and neural mechanisms and indicate that the left posterior parietal lobe is a necessary structure for mental transformations of human BPs.

Effects of cross-sex hormones on cerebral activation during language and mental rotation: An fMRI study in transsexuals

Androgens and estrogens affect the performance on certain cognitive tests, particularly those measuring verbal fluency and mental rotation. Their effects on cognition have frequently been attributed to changes in cerebral lateralization. This study tested the impact of a reversal of the sex steroid milieu on cerebral activation and lateralization during verbal and spatial tasks in transsexuals. fMRI scans were obtained from 6 female-to-male and 8 male-to-female transsexuals at baseline and after cross-sex steroid treatment. Activation was measured during language and mental rotation tasks. Language activation increased after sex steroid treatment in both groups (F(1,12) =3.7, p=0.08), and total language activity was correlated to post-treatment estradiol levels (rho=0.54, p=0.05). Lateralization was not affected by the reversal of sex steroid milieus (F(1,12)=1.47, p=0.25). Activation during mental rotation did not increase during treatment (F(1,12)=0.54, p=0.34), but post-treatment testosterone levels correlated to total activation during mental rotation (rho=0.64, p=0.01). Findings suggest that sex steroids may influence cerebral activation, but lateralization remains stable.