Visuospatial Attention Network Research Articles

Atlas for the Lateralized Visuospatial Attention Networks (ALANs): Insights from fMRI and network analyses

Abstract Hemispheric specialization is central to human evolution and fundamental to human cognitive abilities. While being a defining feature of functional brain architecture, hemispheric specialization is overlooked to derive brain parcellations. Alongside language, which is typically lateralized in the left hemisphere, visuospatial attention is set to be its counterpart in the opposite hemisphere. However, it remains uncertain to what extent the anatomical and functional underpinnings of lateralized visuospatial attention mirror those supporting language. Building on our previous work, which established a lateralized brain atlas for language, we propose a comprehensive cerebral lateralized atlas delineating the anatomo-functional bases of visuospatial attention, Atlas for Lateralized visuospatial Attentional Networks (ALANs). Combining task and resting-state functional connectivity analyses, we identified 95 lateralized brain areas comprising three networks supporting visual (visu), motor (somato-motor), and spatial processing (posterior-medial) processes at work during a line judgment bisection task, and two large-scale networks related to integrated visuospatial attention processes, the parieto-frontal and temporo-frontal networks. We identify hubs playing a pivotal role in the intra-hemispheric interaction within visuospatial attentional networks. The rightward lateralized parieto-frontal encompasses one hub, the inferior frontal sulcus, while the temporo-frontal network encompasses two right hubs: the inferior frontal cortex (pars triangularis and the anterior insula) and the posterior part of the superior temporal sulcus. Compared with our language lateralized atlas, we demonstrated that specific regions within these networks encompass the homotope of the language network from the left hemisphere. This atlas of visuospatial attention provides valuable insights for future investigations into the variability of visuospatial attention and hemispheric specialization research. Additionally, it facilitates more effective comparisons among different studies, thereby enhancing the robustness and reliability of research in the field of attention.

Association of disruption of the right posterior arcuate fasciculus with spatial neglect.

Spatial neglect is a debilitating condition observed in patients with right-sided brain injuries in whom there is defective awareness of the contralesional space. Although classically considered a right parietal lobe deficit, there has been increasing interest in the specific white matter (WM) architecture subserving spatial neglect. Patients who have lesions associated with chronic disruptions in visuospatial networks are of significant relevance in elucidating the WM tracts associated with spatial attention. In this study, the authors used two independent analytical methods to examine the relationship between WM connectivity changes and spatial attention. Thirty patients with right-sided glioma underwent diffusion tensor imaging (DTI) tractography and neuropsychological testing prior to tumor resection. Spatial neglect was assessed using the Bells Test. Diffusion connectometry analysis was performed to calculate the probability of injury to 55 WM tracts. Next, quantitative DTI tractography was used to reconstruct 9 major WM tracts and obtain fractional anisotropy (FA) and streamline number values as indices of connectivity. Differences in connectivity were assessed between patients with neglect and controls. Of the WM tracts analyzed by diffusion connectometry, only the right posterior segment of the arcuate fasciculus (psAF) showed a higher probability of disconnection in patients with evidence of hemispatial neglect compared to tract reconstructions of previously published healthy controls (hemineglect: 42% ± 12.5%, vs control: 6.3% ± 4.8% [mean ± SEM]; p < 0.05). Of the WM tracts reconstructed by DTI tractography, only the right psAF demonstrated consistently lower indices of connectivity based on the mean streamline number (hemineglect: 550.35 ± 183.41, vs control: 1407.01 ± 319.93; p < 0.05) and FA value (hemineglect: 0.40 ± 0.013, vs control: 0.44 ± 0.0063; p < 0.05) in patients who demonstrated neglect compared to controls. The right long segment of the arcuate fasciculus, inferior frontooccipital fasciculus, and inferior longitudinal fasciculus also demonstrated a lower streamline number, but not a lower FA value, in patients with evidence of hemineglect. These findings suggest that parietotemporal networks mediated by the right psAF may play a critical role in visuospatial attention. This analysis may help to disentangle the organization of the visuospatial attention networks, predict deficits in patients with glioma, and optimize surgical planning.

Psychopathology and Integrity of the Superior Longitudinal Fasciculus in Deficit and Nondeficit Schizophrenia.

The superior longitudinal fasciculus (SLF) is a white matter bundle that connects the frontal areas with the parietal areas. As part of the visuospatial attentional network, it may be involved in the development of schizophrenia. Deficit syndrome (DS) is characterized by primary and enduring negative symptoms. The present study assessed SLF integrity in DS and nondeficit schizophrenia (NDS) patients and examined possible relationships between it and psychopathology. Twenty-six DS patients, 42 NDS patients, and 36 healthy controls (HC) underwent psychiatric evaluation and diffusion tensor imaging (DTI). After post-processing, fractional anisotropy (FA) values within the SLF were analyzed. Psychopathology was assessed with the Positive and Negative Syndrome Scale, Brief Negative Symptom Scale, and Self-evaluation of Negative Symptoms. The PANSS proxy for the deficit syndrome was used to diagnose DS. NDS patients had lower FA values than HC. DS patients had greater negative symptoms than NDS patients. After differentiating clinical groups and HC, we found no significant correlations between DTI measures and psychopathological dimensions. These results suggest that changes in SLF integrity are related to schizophrenia, and frontoparietal dysconnection plays a role in its etiopathogenesis. We confirmed that DS patients have greater negative psychopathology than NDS patients. These results are preliminary; further studies are needed.

Anatomical Connectivity of the Visuospatial Attentional Network in Schizophrenia: A Diffusion Tensor Imaging Tractography Study.

In healthy individuals, the visuospatial attentional network consists of frontoparietal bundles; however, the anatomical organization of this network in persons with schizophrenia remains largely unknown. Using diffusion tensor imaging-based tractography, the authors investigated the white matter integrity and volume of frontoparietal and frontotemporo-occipital bundles in the right and left hemispheres and studied their structural asymmetry in persons with schizophrenia and in healthy individuals. This study included 34 participants with schizophrenia and 69 healthy individuals. Integrity parameters and volume were calculated in the three branches of the superior longitudinal fasciculus (SLF I, II, and III), the inferior longitudinal fasciculus, and the inferior fronto-occipital fasciculus in both hemispheres. In the SLF II and SLF III of the right hemisphere, healthy individuals showed greater integrity, compared with participants with schizophrenia. Both groups presented increased integrity in the SLF III of the right hemisphere, compared with the SLF III of the left hemisphere, but only healthy individuals had this pattern regarding the SLF II. Bundle volumes did not differ between groups. This study is the first to describe the structural hemispheric lateralization and organization of the visuospatial attentional network in persons with schizophrenia. The main findings indicate loss of integrity in the SLF II, associated with loss of asymmetry in participants with schizophrenia, compared with healthy individuals, suggesting a potential substrate of attentional deficits.

Changed hub and functional connectivity patterns of the posterior fusiform gyrus in chess experts.

The hubs of the brain network play a key role in integrating and transferring information between different functional modules. However, the effects of long-term practice on functional network hubs in chess experts are largely undefined. Here, we investigated whether alterations of hubs can be detected in chess experts using resting-state functional magnetic resonance imaging (rs-fMRI) and graph theory methods. We first mapped the whole-brain voxel-wise functional connectivity and calculated the functional connectivity strength (FCS) map in each of the 28 chess players and 27 gender- and age-matched healthy novice players. Whole-brain resting-state functional connectivity analyses for the changed hub areas were conducted to further elucidate the corresponding changes of functional connectivity patterns in chess players. The hub analysis revealed increased FCS in the right posterior fusiform gyrus of the chess players, which was supported by analyses of this area's regional homogeneity (ReHo), amplitude of low frequency fluctuations (ALFF), and fractional amplitude of low frequency fluctuations (fALFF). The following functional connectivity analyses revealed increased functional connectivities between the right posterior fusiform gyrus and the visuospatial attention and motor networks in chess players. These findings demonstrate that cognitive expertise has a positive influence on the functions of the brain regions associated with the chess expertise and that increased functional connections might in turn facilitate within and between networks communication for expert behavior to get superior performance.

Alpha and alpha-beta phase synchronization mediate the recruitment of the visuospatial attention network through the Superior Longitudinal Fasciculus

It is well known that attentional selection of relevant information relies on local synchronization of alpha band neuronal oscillations in visual cortices for inhibition of distracting inputs. Additionally, evidence for long-range coupling of neuronal oscillations between visual cortices and regions engaged in the anticipation of upcoming stimuli has been more recently provided. Nevertheless, on the one hand the relation between long-range functional coupling and anatomical connections is still to be assessed, and, on the other hand, the specific role of the alpha and beta frequency bands in the different processes underlying visuo-spatial attention still needs further clarification.We address these questions using measures of linear (frequency-specific) and nonlinear (cross-frequency) phase-synchronization in a cohort of 28 healthy subjects using magnetoencephalography. We show that alpha band phase-synchronization is modulated by the orienting of attention according to a parieto-occipital top-down mechanism reflecting behavior, and its hemispheric asymmetry is predicted by volume's asymmetry of specific tracts of the Superior-Longitudinal-Fasciculus. We also show that a network comprising parietal regions and the right putative Frontal-Eye-Field, but not the left, is recruited in the deployment of spatial attention through an alpha-beta cross-frequency coupling. Overall, we demonstrate that the visuospatial attention network features subsystems indexed by characteristic spectral fingerprints, playing different functional roles in the anticipation of upcoming stimuli and with diverse relation to fiber tracts.

The visuospatial attention network recruitment is mediate by alpha and alpha-beta phase synchronization through the Superior Longitudinal Fasciculus

The visuospatial attention network recruitment is mediate by alpha and alpha-beta phase synchronization through the Superior Longitudinal Fasciculus

S167. ANATOMICAL CONNECTIVITY OF THE VISUOSPATIAL ATTENTIONAL NETWORK IN SCHIZOPHRENIA: A DTI-BASED TRACTOGRAPHY STUDY

BackgroundIn healthy controls (HCs), the visuospatial attentional network consists of fronto-parietal bundles distributed across both hemispheres, but the anatomical organization of this network remains largely unknown in patients with schizophrenia (SZPs). Using diffusion tensor imaging (DTI)-based tractography, we investigated both white matter integrity and the volume of visuospatial attentional pathways in the right and left hemispheres (RH and LH), as well as their structural asymmetry in SZPs and HCs and hypothesized that SZPs would have WM pathway alterations and abnormal structural asymmetry.MethodsThis study included 34 SZPs and 69 HCs. Integrity parameters (fractional anisotropy [FA], radial and mean diffusivity [RD and MD]) and volume were calculated in each fasciculus of this network: the three branches of the superior longitudinal fasciculus (SLFI–III), the inferior longitudinal fasciculus, and the inferior fronto-occipital fasciculus in the RH and LH.ResultsIn SLFII and SLFIII, compared to RH and LH values for SZPs, HCs presented increased FA and/or decreased RD/MD in RH and/or LH. Both SZPs and HCs presented increased FA and decreased RD/MD in the RH compared to the LH in the SLFIII, whereas only HCs had this pattern in the SLFII. Volumes did not differ between groups.DiscussionTo our knowledge, this study is the first to describe the structural hemispheric lateralization/organization of the visuospatial attentional network in SZPs. Our main findings are disrupted structural connectivity in the SLFII associated with abnormal anatomical asymmetry in patients, which could be a substrate of attentional deficits.

Frequency-specific Transcranial Modulation of Oscillatory Dynamics in Visuospatial Attention Networks

The ability to deploy neural resources to discrete stimulus features or groupings of features within the visual space is important to normative cognitive function. Population-level neural oscillatory activity across multiple frequencies and spatial locations has been linked to attentional deployment, but the inherent temporal dynamics of these neural oscillations have stymied efforts to image these responses in humans. Further, the impact of modulating neural activity in these networks on attentional performance remains unknown. Herein, we apply 2.0 mA transcranial direct current stimulation (tDCS) for 20 minutes over key nodes of the visual attention network (i.e., the visual and prefrontal cortices) using two opposite polarity current configurations, as well as a sham condition. Participants then performed an offline visuospatial discrimination task during concurrent recording with magnetoencephalography (MEG). Recordings were decomposed into time-frequency space and significant changes from baseline were identified and imaged. Time-series were then extracted from peak voxels for subsequent analysis, including functional connectivity analyses. Stimulation significantly altered behavioral performance in the attention task and basal activity in a polarity specific way, such that cathodal and anodal stimulation each affected the dynamics of attention circuits at distinct frequencies. Interestingly, the magnitudes of oscillatory neural responses at these frequencies were not significantly different between stimulation conditions, meaning that the tDCS-induced shifts in basal activity (i.e., baseline) carried through to the absolute amplitude of neural responses during attentional deployment. These findings shed light on the multi-spectral effects of tDCS on human neural circuits, particularly within and between prototypical attention network hubs.

Age-related reduction of hemispheric lateralisation for spatial attention: An EEG study

A group-level visuospatial attention bias towards the left side of space (pseudoneglect) is consistently observed in young adults, which is likely to be a consequence of right parieto-occipital dominance for spatial attention. Conversely, healthy older adults demonstrate a rightward shift of this behavioural bias, hinting that an age-related reduction of lateralised neural activity may occur within visuospatial attention networks. We compared young (aged 18–25) and older (aged 60–80) adults on a computerised line bisection (landmark) task whilst recording event-related potentials (ERPs). Full-scalp cluster mass permutation tests identified a larger right parieto-occipital response for long lines compared to short in young adults (confirming Benwell et al., 2014a) which was not present in the older group. To specifically investigate age-related differences in hemispheric lateralisation, cluster mass permutation tests were then performed on a lateralised EEG dataset (RH-LH electrodes). A period of right lateralisation was identified in response to long lines in young adults, which was not present for short lines. No lateralised clusters were present for either long or short lines in older adults. Additionally, a reduced P300 component amplitude was observed for older adults relative to young. We therefore report here, for the first time, an age-related and stimulus-driven reduction of right hemispheric control of spatial attention in older adults. Future studies will need to determine whether this is representative of the normal aging process or an early indicator of neurodegeneration.

The Influence of Alertness on the Spatial Deployment of Visual Attention is Mediated by the Excitability of the Posterior Parietal Cortices.

With a reduced level of alertness, healthy individuals typically show a rightward shift when deploying visual attention in space. The impact of alertness on the neural networks governing visuospatial attention is, however, poorly understood. By using a transcranial magnetic stimulation twin-coil approach, the present study aimed at investigating the effects of an alertness manipulation on the excitability of the left and the right posterior parietal cortices (PPCs), crucial nodes of the visuospatial attentional network. Participants’ visuospatial attentional deployment was assessed with a free visual exploration task and concurrent eye tracking. Their alertness level was manipulated through the time of the day, that is, by testing chronotypically defined evening types both during their circadian on- and off-peak times. The results revealed an increased excitability of the left compared with the right PPC during low alertness. On the horizontal dimension, these results were accompanied by a significant rightward shift in the center and a bilateral narrowing in the periphery of the visual exploration field, as well as a central upward shift on the vertical dimension. The findings show that the manipulation of non-spatial attentional aspects (i.e., alertness) can affect visuospatial attentional deployment and modulate the excitability of areas subtending spatial attentional control.

Pupil-size asymmetry is a physiologic trait related to gender, attentional function, and personality

ABSTRACTA small difference in the size of the two pupils is common in healthy individuals, a condition termed benign or physiologic anisocoria (BA). Past research indicates that BA is probably caused by asymmetry in sympathetic nervous system (SNS) function [e.g., Rosenberg (2008). Physiologic anisocoria: A manifestation of a physiologic sympathetic asymmetry. Neuro-Ophthalmology, 32, 147–149]. This study is the first to show that BA varies with psychological factors linked to brain asymmetry and autonomic arousal, including gender, attention, and personality. Males exhibited a more directional BA than females, consistent with greater hemispheric lateralization in males. BA also varied with a self-report measure of attentional function, consistent with evidence of hemispheric asymmetry in visuospatial attention networks. Finally, BA varied with personality traits linked to autonomic arousal. Individuals exhibiting higher Meanness and Boldness, and lower Empathy scores tended to show more directional BA. This link between personality traits and BA may be related to brain asymmetries in autonomic arousal and emotion-related processing. If future studies employing direct measures of lateralized brain activity confirm the link between BA and SNS asymmetries, this new metric may prove useful in discovering new relationships between brain organization and psychological function, and how these relationships vary across individuals.

Brain changes within the visuo-spatial attentional network in posterior cortical atrophy.

Posterior cortical atrophy (PCA) is characterized by basic visual and high order visual-spatial dysfunctions. In this study, we investigated long-distance deafferentation processes within the frontal-parietal-occipital network in ten PCA patients using a MRI-PET combined approach. Objective voxel-based [18F]FDG-PET imaging measured metabolic changes in single patients. Comprehensive investigation of diffusion tensor imaging (DTI) metrics and grey-matter density with voxel-based morphometry were obtained in a subgroup of 6 patients. Fractional anisotropy in the superior longitudinal fasciculus correlated with the PET metabolic changes within the inferior parietal and frontal eye field regions. [18F]FDG-PET analysis showed in each PCA case the typical bilateral hypometabolic pattern, involving posterior temporal, parietal, and occipital cortex, with additional hypometabolic foci in the frontal eye fields. Voxel-based morphometry showed right-sided atrophy in the parieto-occipital cortex, as well as a limited temporal involvement. DTI revealed extensive degeneration of the major anterior-posterior connecting fiber bundles and of commissural frontal lobe tracts. Microstructural measures in the superior longitudinal fasciculus were correlated with the PET metabolic changes within the inferior parietal and frontal eye field regions. Our results confirmed the predominant occipital-temporal and occipital-parietal degeneration in PCA patients. [18F]FDG-PET and DTI-MRI combined approaches revealed neurodegeneration effects well beyond the classical posterior cortical involvement, most likely as a consequence of deafferentation processes within the occipital-parietal-frontal network that could be at the basis of visuo-perceptual, visuo-spatial integration and attention deficits in PCA.

The frequency and severity of extinction after stroke affecting different vascular territories

We examined the frequency and severity of visual versus tactile extinction based on data from a large group of sub-acute patients (n=454) with strokes affecting different vascular territories. After right hemisphere damage visual and tactile extinction were equally common. However, after left hemisphere damage tactile extinction was more common than visual. The frequency of extinction was significantly higher in patients with right compared to left hemisphere damage in both visual and tactile modalities but this held only for strokes affecting the MCA and PCA territories and not for strokes affecting other vascular territories. Furthermore, the severity of extinction did not differ as a function of either the stimulus modality (visual versus tactile), the affected hemisphere (left versus right) or the stroke territory (MCA, PCA or other vascular territories). We conclude that the frequency but not severity of extinction in both modalities relates to the side of damage (i.e. left versus right hemisphere) and the vascular territories affected by the stroke, and that left hemisphere dominance for motor control may link to the greater incidence of tactile than visual extinction after left hemisphere stroke. We discuss the implications of our findings for understanding hemispheric lateralization within visuospatial attention networks.

The Neural Underpinings of Simultanagnosia: Disconnecting the Visuospatial Attention Network

Because of our limited processing capacity, different elements of the visual scene compete for the allocation of processing resources. One of the most striking deficits in visual selection is simultanagnosia, a rare neuropsychological condition characterized by impaired spatial awareness of more than one object at time. To decompose the neuroanatomical substrates of the syndrome and to gain insights into the structural and functional organization of visuospatial attention, we performed a systematic evaluation of lesion patterns in a group of simultanagnosic patients compared with patients with either (i) unilateral visuospatial deficits (neglect and/or extinction) or (ii) bilateral posterior lesions without visuospatial deficits, using overlap/subtraction analyses, estimation of lesion volume, and a lesion laterality index. We next used voxel-based morphometry to assess the link between different visuospatial deficits and gray matter and white matter (WM) damage. Lesion overlap/subtraction analyses, lesion laterality index, and voxel-based morphometry measures converged to indicate that bilateral parieto-occipital WM disconnections are both distinctive and necessary to create symptoms associated with simultanagnosia. We also found that bilateral gray matter damage within the middle frontal area (BA 46), cuneus, calacarine, and parieto-occipital fissure as well as right hemisphere parietal lesions within intraparietal and postcentral gyri were associated with simultanagnosia. Further analysis of the WM based on tractography revealed associations with bilateral damage to major pathways within the visuospatial attention network, including the superior longitudinal fasciculus, the inferior fronto-occipital fasciculus, and the inferior longitudinal fasciculus. We conclude that damage to the parieto-occipital regions and the intraparietal sulcus, together, with bilateral WM disconnections within the visuosptial attention network, contribute to poor visual processing of multiple objects and the loss of processing speed characteristic of simultanagnosia.

The central role of the temporo-parietal junction and the superior longitudinal fasciculus in supporting multi-item competition: Evidence from lesion-symptom mapping of extinction

The present study examined the relations between the lesions linked to visual and tactile extinction (VE and TE), and those related to visual field defects and spatial neglect. Continuous variations in patients’ performance were used to assess the link between behavioural scores and integrity of both grey and white matter (GM and WM). We found both common and distinct neural substrates associated with extinction and neglect. Damage to angular and middle occipital gyri, superior temporal sulcus (STS) and insula were linked to VE. Lesions involving the supramarginal gyrus (SMG), intraparietal sulcus, middle frontal and superior temporal gyri (MFG and STG) were associated exclusively with spatial neglect. Lesions affecting the temporo-parietal junction (TPJ), the middle temporal region, middle frontal area (BA46) as well as the insula and putamen were linked to both spatial neglect and VE. Analysis of the relations between VE and TE highlighted the TPJ as the common site for both modalities. These findings suggest that the TPJ plays a general role in identifying salient events in the sensory environment across multiple modalities. Furthermore, WM analyses pointed to superior longitudinal fasciculus (SLF) as critical for interconnecting components of the visuospatial attention network. We demonstrated that functional disconnections resulting from SLF damage contribute to altered performance on attention tasks measuring not only neglect but also VE and TE. We propose that the SLF supports interactions between functionally specialized regions involved in attentional control across multiple sensory modalities.

Maximizing the imaginary part of coherency to detect cortico-cortical interactions

Event Abstract Back to Event Maximizing the imaginary part of coherency to detect cortico-cortical interactions Laura Marzetti1*, Stefania D. Penna1, Vittorio Pizzella1, Gian L. Romani1 and Guido Nolte2 1 G. D`Annunzio University Foundation, ITAB, Italy 2 Fraunhofer FIRST, Athena project team, Germany In order to understand brain function, it is fundamental to describe interactions between functionally specialized brain regions. To this end, MEG is an ideal technique thanks to its whole head coverage and temporal resolution that allow reconstruction of source activity at millisecond scale. Thus, neuronal interactions can be studied on the estimated brain source rather than at sensor level where severe limitations arise by volume conduction or field spread self-interaction effects[1]. Nevertheless, since this effect can never be completely abolished because unmixing of the sources bis never perfect, we estimate seed based cortico-cortical interaction by the imaginary part of coherency (IPC) which cannot be generated by independent sources [1]. When estimating brain sources without introducing anatomical constraints on dipole orientation, e.g. limiting sources to be normal to the cortex surface, brain signals along x, y and z spatial directions are obtained at each voxel using weighted minimum norm solutions. Principal component analysis (PCA) can be used to reduce dimensionality, but since PC is related to power an alternate approach can be used when analysing interaction. We propose an approach to find for each pair of voxels the respective dipole orientations which maximize the IPC between those voxels. The problem can be solved analytically in closed form. In this way we find for a given seed the largest possible interaction with any other voxel as measured by IPC. The method is tested on subjects performing a force controlled motor task (squeeze and release a water filled pump) with the left hand. As a seed region the contralateral primary motor area M1 is chosen and the IPC is estimated for various frequencies. Frequency specific preferential directions are found that correspond to patterns showing e.g. a somato-motor circuit involved in low alpha and a visuo-spatial attention network in high alpha.

Plasticity of the Attentional Network After Brain Injury and Cognitive Rehabilitation

Background. This study aimed to delineate the cerebral attentional network in patients with traumatic brain injury (TBI) and assess for adaptations in this network in response to a rehabilitation intervention. Methods. Seventeen patients with TBI and 15 healthy subjects underwent functional magnetic resonance imaging (fMRI) using a visuospatial attention task. Ten TBI patients who successfully completed attentional training had a follow-up fMRI. Results. In the TBI patients, fMRI analysis showed more activation in the frontal and temporoparietal lobes, as well as less activation in the anterior cingulated gyrus, SMA, and temporooccipital regions compared to the healthy subjects. Following cognitive training, the TBI patients improved performance of attention tasks accompanied by changes in attentional network activation; the activity of the frontal lobe decreased, whereas activation of the anterior cingulate cortices and precuneus increased. Conclusions. These findings demonstrate the plasticity and training induced redistribution of the visuospatial attentional network in TBI patients.

Recognition and reading aloud of kana and kanji word: An fMRI study

It has been proposed that different brain regions are recruited for processing two Japanese writing systems, namely, kanji (morphograms) and kana (syllabograms). However, this difference may depend upon what type of word was used and also on what type of task was performed. Using fMRI, we investigated brain activation for processing kanji and kana words with similar high familiarity in two tasks: word recognition and reading aloud. During both tasks, words and non-words were presented side by side, and the subjects were required to press a button corresponding to the real word in the word recognition task and were required to read aloud the real word in the reading aloud task. Brain activations were similar between kanji and kana during reading aloud task, whereas during word recognition task in which accurate identification and selection were required, kanji relative to kana activated regions of bilateral frontal, parietal and occipitotemporal cortices, all of which were related mainly to visual word-form analysis and visuospatial attention. Concerning the difference of brain activity between two tasks, differential activation was found only in the regions associated with task-specific sensorimotor processing for kana, whereas visuospatial attention network also showed greater activation during word recognition task than during reading aloud task for kanji. We conclude that the differences in brain activation between kanji and kana depend on the interaction between the script characteristics and the task demands.

Transient and sustained brain activity during anticipatory visuospatial attention

In this study, we determined whether the visuospatial attention network of frontal, parietal, and occipital cortex can be parsed into two different subsets of active regions associated with transient and sustained processes within the same cue-to-target delay period of an endogenously cued visuospatial attention task. We identified regions with early transient activity and regions with later sustained activity during the same trials using a general linear model analysis of event-related BOLD functional MRI data with two timecourse covariates for the same cue-to-target delay period. During the delay between the cue and target, we observed significant transient activity in right frontal eye field and right occipital-parietal junction, and significant sustained activity in right ventral intraparietal sulcus and right dorsolateral and anterior prefrontal cortex.