Left Occipital Area Research Articles

Do developmental prosopagnosics with high vs. low levels of autism traits differ in how they process faces?

Developmental prosopagnosia (DP) studies have routinely excluded individuals with high autism traits, assuming that DPs with high levels of autism traits have qualitatively different mechanisms of face recognition impairment, e.g., caused by social motivational factors. Indeed, autism spectrum disorders (ASD) are associated with face recognition memory and face emotion processing deficits but largely unimpaired face perception and holistic face processing abilities, whereas DPs without ASD have shown face perception and holistic processing deficits in addition to face memory deficits. To investigate the relationship between autism traits and face processing in DP, we administered a large behavioral battery and a face/scene/object/body fMRI localizer to 43 DPs with a wide range of Autism Quotient (AQ) scores as well as 27 healthy controls. When comparing the high (n=15; met broader autism phenotype classification) and low (n=28) AQ DP groups (AQ: 28.33 vs. 14.50; p<.001), we found a similar pattern across face processing tasks, with no differences in face matching (Cambridge Face Perception Test; p=.617), holistic face processing (Inversion effect: p=.644; Part-whole effect: p=.170), featural processing (Eyes: p=.643; Mouth: p=.984), or face memory (Cambridge Face Memory Test; p=.598). Both DP groups performed significantly worse on the face processing tasks compared to the control group (p’s<.05), with the exception of the mouth composite. As expected, the higher AQ group showed significantly decreased face emotion recognition compared to the low AQ group (p=.028). During the fMRI localizer task, both DP groups showed similarly reduced face selectivity in the left occipital and fusiform face areas compared to controls. Notably, the higher AQ DPs also showed decreased face selectivity in the bilateral posterior superior temporal sulcus compared to the lower AQ DPs. These results suggest that high autism traits do not result in qualitatively different face processing in DPs, but are associated with greater face emotion recognition impairments.

CORRELATING DESIGN PERFORMANCE TO EEG ACTIVATION: EARLY EVIDENCE FROM EXPERIMENTAL DATA

AbstractThis paper presents an EEG (Electroencephalography) study that explores correlations between the neurophysiological activations, the nature of the design task and its outputs. We propose an experimental protocol that covers several design-related tasks: including fundamental activities (e.g. idea generation and problem-solving) as well as more comprehensive task requiring the complex higher-level reasoning of designing. We clustered the collected data according to the characteristics of the design outcome and measured EEG alpha band activation during elementary and higher-level design task, whereas just the former yielded statistically significant different behaviour in the left frontal and occipital area. We also found a significant correlation between the ratings for elementary sketching task outcomes and EEG activation at the higher-level design task. These results suggested that EEG activation enables distinguishing groups according to their performance only for elementary tasks. However, this also suggests a potential application of EEG data on the elementary tasks to distinguish the designers' brain response during higher-level of design task.

Age-related differences in alpha and beta band activity in sensory association brain areas during challenging sensory tasks

Sensory challenges to postural balance are daily threats for elderly individuals. This study examined electroencephalography (EEG) in alpha and beta bands in sensory association areas during the Sensory Organization Test, involving withdrawal of visual or presenting misleading somatosensory inputs, in twelve young and twelve elderly participants. The results showed stepwise deterioration in behavioral performance in four conditions, with group effects that were amplified with combined sensory challenges. With eye closure, alpha and beta activities increased in all sensory association areas. Fast beta activity increased in the bilateral parietal-temporal-occipital areas. Misleading somatosensory information effects on EEG activity were of smaller amplitude than eye closure effects and in a different direction. Decreased alpha activity in left parietal-temporal-occipital areas and decreased beta and fast beta activities in bilateral parietal-temporal-occipital areas were significant. Elderly participants had increased fast beta activity in the left temporal-occipital and bilateral occipital areas, indicative of sustained efforts that they made in all sensory conditions. Similar to the young participants, elderly participants with eyes closed showed increased alpha activity, although to a smaller degree, in bilateral temporal-occipital and left occipital areas. This might indicate a lack of efficacy in redistributing relative sensory weights when elderly participants dealt with eye closure. In summary, EEG power changes did not match the stepwise deterioration in behavioral data, but reflected different sensory strategies adopted by young and elderly participants to cope with eye closure or misleading somatosensory information based on the efficacy of these different strategies.

Cerebral arterial air embolism with anterior spinal cord syndrome after CT-guided hook-wire localization of Lung mass and pulmonary nodule

Systemic arterial air embolism (SAAE) is a rare but serious complication of CT-guided hook wire localization of pulmonary nodule usually with catastrophic and poor outcome. Hook wire needle localization is done pre-operatively by placing wire around or into the pulmonary nodule to provide the thoracic surgeon accurate location guidance of the target nodule for Video-Assisted Thoracoscopic Surgery (VATS) wedge resection with safety margins. Physicians should be aware of this possible complication during the procedure in order to rescue the patient promptly as it requires rapid diagnosis and management. We describe a 55-year-old male who underwent a CT-guided hook wire needle localization of left upper lobe lung cancer and left lower lobe pulmonary nodule prior to planned VATS wedge resection who developed altered mental status and bilateral lower extremities paralysis after wire placement was completed. His CT head demonstrated small air embolism in the left occipital area, confirming the diagnosis of cerebral air embolism and follow up CT and MRI of the head revealed multiple areas of brain infarction. In addition, he was diagnosed with anterior spinal cord syndrome (ACS), most likely due to anterior spinal artery ischemia from micro air embolism on the basis of clinical findings but with negative ischemic changes on MRI of the spinal cord. His mental status recovered but he remained paraplegic and transferred to inpatient rehabilitation service.

Single-Case Neuropsychological Assessment of a Patient with a Posterior Parietal Lesion Using Behavioral Testing and Resting-State fMRI

This study integrated functional connectivity measures using resting-state fMRI and behavioral data from a single-case observation of patient (PER) one year after right-hemispheric hemorrhage in the intraparietal sulcus and superior parietal lobule (IPS/SPL). PER showed no sign of clinical neglect. Her behavioral performance in the visuo-manual pointing task and in the letter discrimination task under conditions of endogenous and exogenous attentional cueing was compared between the left (affected) and right (unaffected/control) peripheral visual fields. The resting-state fMRI demonstrated an imbalance between the right and left hemispheric frontoparietal functional connectivity within the dorsal attentional and motor networks. Although the frontal and occipital cortices were not structurally damaged, specific fronto-occipital functional connectivity was imbalanced, which was strongly associated with the behavioral changes. First, the activity in the right frontal eye field showed weaker correlations with the activity in the right inferior occipital area compared to the correlation with the activity in the left inferior occipital area. This imbalanced fronto-occipital functional connectivity was accompanied by a specific impairment in endogenous covert attention in the left visual field. Second, the activity within M1 in both hemispheres showed weaker correlations with the activity of the right cuneus compared to the correlation with the activity in the left cuneus. The imbalanced fronto-occipital functional connectivity was associated with the impairment of the reaching movement of the left and right hands towards the left visual field (optic ataxia). Altogether, our results showed that a lesion to the posterior parietal cortex affects the relationship between distal regions underlying the sensorimotor and attentional abilities

Hemispheric Asymmetry in Visual Processing: An ERP Study on Spatial Frequency Gratings

A hemispheric asymmetry for the processing of global versus local visual information is known. In this study, we investigated the existence of a hemispheric asymmetry for the visual processing of low versus high spatial frequency gratings. The event-related potentials were recorded in a group of healthy right-handed volunteers from 30 scalp sites. Six types of stimuli (1.5, 3 and 6 c/deg gratings) were randomly flashed 180 times in the left and right upper hemifields. The stimulus duration was 80 ms, and the interstimulus interval (ISI) ranged between 850 and 1000 ms. Participants paid attention and responded to targets based on their spatial frequency and location. The C1 and P1 visual responses, as well as a later selection negativity and a P300 component of event-related potentials (ERPs), were quantified and subjected to repeated-measure analyses of variance (ANOVAs). Overall, the performance was faster for the right visual field (RVF), thus suggesting a left hemispheric advantage for the attentional selection of local elements. Similarly, the analysis of the mean area amplitude of the C1 (60–110 ms) sensory response showed a stronger attentional effect (F+L+ vs. F−L+) at the left occipital areas, thus suggesting the sensory nature of this hemispheric asymmetry.

Increased functional connectivity within alpha and theta frequency bands in dysphoria: A resting-state EEG study

Background: The understanding of neurophysiological correlates underlying the risk of developing depression may have a significant impact on its early and objective identification. Research has identified abnormal resting-state electroencephalography (EEG) power and functional connectivity patterns in major depression. However, the entity of dysfunctional EEG dynamics in dysphoria is yet unknown.Methods: 32-channel EEG was recorded in 26 female individuals with dysphoria and in 38 age-matched, female healthy controls. EEG power spectra and alpha asymmetry in frontal and posterior channels were calculated in a 4-minute resting condition. An EEG functional connectivity analysis was conducted through phase locking values, particularly mean phase coherence.Results: While individuals with dysphoria did not differ from controls in EEG spectra and asymmetry, they exhibited dysfunctional brain connectivity. Particularly, in the theta band (4-8 Hz), participants with dysphoria showed increased connectivity between right frontal and central areas and right temporal and left occipital areas. Moreover, in the alpha band (8-12 Hz), dysphoria was associated with increased connectivity between right and left prefrontal cortex and between frontal and central-occipital areas bilaterally.Limitations: All participants belonged to the female gender and were relatively young. Mean phase coherence did not allow to compute the causal and directional relation between brain areas.Conclusions: An increased EEG functional connectivity in the theta and alpha bands characterizes dysphoria. These patterns may be associated with the excessive self-focus and ruminative thinking that typifies depressive symptoms. EEG connectivity patterns may represent a promising measure to identify individuals with a higher risk of developing depression.

Structural dysconnectivity in offspring of individuals with bipolar disorder: The effect of co-existing clinical-high-risk for bipolar disorder

BackgroundBipolar disorder (BD) might be associated in disturbances in brain networks. However, little is known about the abnormalities in structural brain connectivity which might be related to vulnerability to BD and predictive of the emergence of manic symptoms. No previous study has investigated the effect of subthreshold syndromes on structural dysconnectivity in offspring of parents with BD (BDoff). MethodsWe investigated diffusion weighted images of 70 BDoff and 48 healthy controls (HC). Nineteen of the 70 BDoff had presented with subthreshold syndromes indicating a clinical high-risk (BDoff-CHR) and other 51 BDoff had no such history (BDoff-non-CHR). Global and regional network properties, rich club organization and inter-regional connectivity in BDoff and healthy controls were investigated using graph analytical methods and network-based-statistics (NBS). ResultsGlobal properties of WM networks appeared to be intact in BDoff-CHR and BDoff-non-CHR. However, decreased regional connectivity in right occipito-parietal areas and cerebellum was a common feature of both BDoff groups. Importantly, decreased interregional connectivity between nodes in right and left prefrontal regions, nodes in right prefrontal lobe and right temporal lobe and nodes in left occipital area and left cerebellum were evident in BDoff-CHR but not BDoff-non-CHR. LimitationsThe cross-sectional nature of the study was the main consideration. ConclusionDecreased regional connectivity in right posterior brain regions might be related to vulnerability to BD. On the other hand, interregional dysconnectivity in anterior frontal and limbic regions and left posterior brain regions might be evident in individuals genetically at risk for developing BD who had experienced subthreshold mood symptoms.

Holistic Integration in the Processing of Chinese Characters as Revealed by Electroencephalography Frequency Tagging.

It is debated whether perceptual expertise of nonface objects, such as visual words, is indicated by holistic processing, which is regarded as a marker of perceptual expertise of faces. We address this question by frequency-tagged electroencephalography. Different parts of real or pseudo Chinese characters are presented at distinctive frequencies (6 or 7.2 Hz), which induce frequency-tagged steady-state visual-evoked potentials at occipital brain areas. The intermodulation response (e.g., 6 + 7.2 = 13.2 Hz) would emerge when holistic integration takes place. Our results suggest that the intermodulation response to the real characters is left lateralized, which is contralateral to previous findings with faces. Furthermore, at the left occipital area, the intermodulation response to real characters is more prominent than pseudo characters, suggesting that holistic integration is enhanced for real characters than for pseudo ones. Taken together, our findings suggest that holistic integration is potentially a general expertise marker for both faces and non-face objects.

Acute administration of methylphenidate differentially affects cortical processing of emotional facial expressions in attention-deficit hyperactivity disorder children as studied by functional near-infrared spectroscopy.

Significance: It has been reported that children with attention-deficit hyperactivity disorder (ADHD) have impairment in the recognition of angry but not of happy facial expressions, and they show atypical cortical activation patterns in response to facial expressions. However, little is known about neural mechanisms underlying the impaired recognition of facial expressions in school-aged children with ADHD and the effects of acute medication on their processing of facial expressions.Aim: We aimed to investigate the possibility that acute administration of methylphenidate (MPH) affects processing of facial expressions in ADHD children.Approach: We measured the hemodynamic changes in the bilateral temporo-occipital areas of ADHD children observing the happy and angry facial expressions before and 1.5 h after MPH or placebo administration in a randomized, double-blind, placebo-controlled, crossover design study.Results: We found that, regardless of medication, happy expressions induced increased oxyhemoglobin (oxy-Hb) responses in the right inferior occipital region but not in the superior temporal region. For angry expressions, oxy-Hb responses increased after MPH administration, but not after placebo administration, in the left inferior occipital area, whereas there was no significant activation before MPH administration.Conclusions: Our results suggest that (1) ADHD children consistently recruit the right inferior occipital regions to process happy expressions and (2) MPH administration to ADHD children enhances cortical activation in the left inferior occipital regions when they process angry expressions.

Do painters need their whole brain to excel?

ABSTRACT Skilled professional artists are sometimes able to maintain their talents while other cognitive functions deteriorate due to brain diseases. The objective of this study is to asses the preserved artistry of a professional painter in spite of the presence of strokes affecting brain areas implicated in art expression. She had a neurologic evaluation and brain imaging after the stroke; painter-curators analyzed and compared the painter’s pictorial artwork created before and after the stroke. In spite of cerebellar, visuospatial, motor, cognitive, and functional deficits likely related to strokes affecting bilateral cerebellar, left occipital, and right temporal-occipital areas, the patient was able to maintain most of their artistic painting skills.. After a short period of functional recovery, our patient showed discrepancy among their impaired cerebellar cerebral functions in day activities and their preserved painting abilities.

Functional Integration and Segregation in Multiplex Brain Networks for Alzheimer's Disease.

Growing evidence links impairment of brain functions in Alzheimer's disease (AD) with disruptions of brain functional connectivity. However, whether the AD brain shows similar changes from a dynamic or cross-frequency view remains poorly explored. This paper provides an effective framework to investigate the properties of multiplex brain networks in AD considering inter-frequency and temporal dynamics. Using resting-state EEG signals, two types of multiplex networks were reconstructed separately considering the network interactions between different frequency bands or time points. We further applied multiplex network features to characterize functional integration and segregation of the cross-frequency or time-varying networks. Finally, machine learning methods were employed to evaluate the performance of multiplex-network-based indexes for detection of AD. Results revealed that the brain networks of AD patients are disrupted with reduced segregation particularly in the left occipital area for both cross-frequency and time-varying networks. However, the alteration of integration differs among brain regions and may show an increasing trend in the frontal area of AD brain. By combining the features of integration and segregation in time-varying networks, the best classification performance was achieved with an accuracy of 92.5%. These findings suggest that our multiplex framework can be applied to explore functional integration and segregation of brain networks and characterize the abnormalities of brain function. This may shed new light on the brain network analysis and extend our understanding of brain function in patients with neurological diseases.

Differences in brain surface area and cortical volume between suicide attempters and non-attempters with major depressive disorder

The neurobiological causes underlying suicidal behaviors in major depressive disorder (MDD) have not been identified. This study was performed to investigate the differences in brain cortical thickness, surface area, and volume between suicide attempters and non-attempters with MDD. We performed magnetic resonance imaging (MRI) in 38 MDD patients (18–65 years old; 18 male, 20 female) with and without a history of suicide attempts. FreeSurfer software was used to compare the cortical thickness, surface area, and volume of 19 suicide attempters with MDD and 19 suicide non-attempters with MDD, while controlling for age, sex, mean area (or volume), and severity of depression. Compared with suicide non-attempters, suicide attempters with MDD exhibited a larger surface area in the left postcentral area and left lateral occipital area and a larger cortical volume in the left postcentral area and left lateral orbitofrontal area. Suicide attempters exhibited a smaller surface area in the left superior frontal area than suicide non-attempters. The present findings provide evidence for neuroanatomical risk factors of suicide in MDD. Further research to replicate these results and determine the mechanisms underlying these findings is needed.

Post-Attentive Integration and Topographic Map Distribution During Audiovisual Processing in Dyslexia: A P300 Event-Related Component Analysis.

BackgroundResearch on audiovisual post-attentive integration has been carried out using a variety of experimental paradigms and experimental groups but not yet studied in dyslexia. We investigated post-attentive integration and topographic voltage distribution in children with dyslexia by analysing the P300 event-related potential (ERP) component.MethodsWe used a 128-child ERP net for the ERP experiment. Two types of stimuli were presented as either congruent or incongruent stimuli. Congruent stimuli included a matching auditory sound with an animal image, whereas incongruent stimuli included unmatched animal sounds. A total of 24 age-matched children were recruited in the control (n = 12) and dyslexia (n = 12) groups. Children pressed button ‘1’ or ‘2’ when presented with congruent or incongruent stimuli, respectively. The P300 amplitudes and latencies with topographic voltage distribution were analysed for both groups.ResultsThe dyslexia group evoked significantly higher P300 amplitudes at the T4 area than the control group. No significant differences were found in cases of P300 latency. Moreover, the dyslexia group demonstrated a higher intensity of P300 voltage distribution in the right parietal and left occipital areas than the control group.ConclusionPost-attentive integration for children with dyslexia is higher and that this integration process implicated the parietal and occipital areas.

Cortical and subcortical gray matter alterations in first-episode drug-naïve adolescents with major depressive disorder.

Major depressive disorder is a major mental disorder affecting adolescents. Cortical thickness provides a sensitive measure of age-associated changes. Previous studies using cortical thickness analysis reported inconsistent results on brain structural changes in adolescent major depressive disorder. The neuroanatomical substrates of major depressive disorder in adolescents are not fully understood. We aimed to compare the anatomical structures of the brain in first-onset drug-naïve adolescents with major depressive disorder to normal controls. Twenty-seven first-episode drug-naïve adolescents with major depressive disorder and an equal number of age-matched control subjects were scanned on a 3T MRI scanner. Comparisons between those two groups were performed using surface-based morphometry analysis for cortical thickness and volumetric analysis of subcortical gray matter. The correlations between morphometric indexes and clinical measures (Hamilton depression rating scale score or children’s depression inventory score) were also calculated. We found that the cortical area is thinner in major depressive disorder patients than in controls, specifically in the left occipital area (precuneus and cuneus, cluster-level family-wise corrected P < 0.05). The hippocampus volume was also smaller in major depressive disorder patients than in the control group. No significant correlations were found between morphometric indexes (average cortical thickness extracted from the left precuneus cluster and hippocampal volume) and clinical measures. The left occipital cortical regions may have a role in the pathophysiology of adolescent major depressive disorder, and the involvement of the hippocampus is important for pathogenic changes even in the early stages of major depressive disorder.

Neurophysiological Features of Perception of Roman and Arabic Numerals in Paranoid Schizophrenia Patients

Latencies and amplitudes of the Р100, N170 and P200 components of event-related potentials (ERPs) derived during visual presentation of Roman and Arabic numerals from healthy subjects and in patients with paranoid schizophrenia were studied. The activation level was estimated as the ratio of the values in response to Arabic and Roman numerals. The Р100 latency in response to Arabic numerals in controls was shorter in the occipital and parietal areas, while the amplitude was higher in the left posterior temporal area. In schizophrenia patients, the Р100 amplitude in response to Arabic numerals was higher in the left temporal area and lower in the right central area. The intergroup analysis showed that the Р100 amplitude in the central parietal, left temporal and right posterior temporal areas in response to Arabic numerals in the control was greater than in schizophrenia patients. The N170 latency in response to Arabic numerals in the control group was shorter in the left occipital, right temporal and parietal areas, while the amplitude was lower in the right posterior temporal area. In schizophrenia patients, the N170 latency of response to Arabic numerals was shorter only in the middle parietal area. Intergroup analysis showed that the N170 latency of responses to both types of stimuli was shorter in the occipital areas in controls compared to the patients, and the amplitude of this wave in response to Roman numerals was higher in the right posterior temporal area. The P200 latency in response to Arabic numerals in control group was shorter in the left frontal area, while the amplitude was higher in the middle frontal and left temporal areas. In schizophrenia patients, the P200 latency in response to Arabic numerals was longer in the left occipital region and the amplitude was lower in the middle central and right occipital areas. Intergroup analysis showed that the latency in response to Arabic numerals was shorter in the left parietal area in the control group compared to the patients, and the amplitude in the right central and left temporal areas was higher. The P200 amplitude in response to Roman numerals in the right prefrontal and left frontal areas was higher in the control compared to the patients. Thus, in norm and in schizophrenia patients different levels of cortical areas activation to the two types of stimuli were revealed reflecting the differences of these stimuli characteristics.

S1-11 CEREBRAL PERFUSION IN SIMPLE CRANIOSYNOSTOSIS USING ARTERIAL SPIN LABELLING MRI.

Introduction: Isolated craniosynostosis is often thought to be a benign condition with mainly aesthetic repercussions but psychomotor delay has been reported. A few studies have assessed the impact of this condition on cerebral perfusion using SPECT. We hypothesized that craniosynostosis can influence the cerebral blood flow by constricting or deforming the brain. Arterial spin labelling MRI is a validated technique to assess the cerebral perfusion. The aim of this study was to measure the perfusion of various areas of the brain using ASL MRI in patients with craniosynostosis. Methods: Seven groups of 10 patients each had pre-operative MRI with ASL-sequence: (1) scaphocephaly less than 6 month of age, (2) scaphocephaly between 6 and 12 months of age, (3) scaphocephaly between 12 and 24 months of age, (4) right plagiocephaly, (5) left plagiocephaly and age-matched control groups. None of the patients had other brain conditions or known mutations. ASL measurements were performed on pre-operative MRI by the same operator for all the patients using 100 mm2 ROI for each of the following areas on both sides: frontal, parietal, temporal, occipital, insula, brainstem, and cerebellum. Results: In patients with sagittal craniosynostosis aged less than 6 months, a right significant occipital hypoperfusion was observed compared to the age-matched control group (p<0,05). A lower perfusion was observed in the occipital area compared to the frontal area in this group on both sides (p<0.01) contrary to the age-matched control group. In the 20 patients older than 6 months, an occipital decreased perfusion compared to the frontal area was only observed on the right side (p<0.05). In the group of 30 patients with sagittal craniosynostosis, lower cerebral perfusion was observed in the occipital area compared to the frontal area in both sides (p<0.01). In patients with plagiocephaly, no difference of cerebral perfusion was shown between the side of the coronal fusion and the other side. In patients with left plagiocephaly, a lower cerebral perfusion was observed in left parietal, temporal and occipital areas compared to left frontal area (p<0.05). In patients with right plagiocephaly, the only difference was observed between right frontal and parietal areas (p<0.01). Conclusion: Premature fusion of skull sutures influences brain perfusion. Sagittal synostosis seems to lower the posterior perfusion of the brain. The impact of unilateral coronal synostosis needs further investigations because of the physiological difference of ASL between the right and the left hemisphere. A pre/post-operative study is furthermore needed to assess the benefits of surgery.

Auditory cues for somatosensory targets invoke visuomotor transformations: Behavioral and electrophysiological evidence.

Prior to goal-directed actions, somatosensory target positions can be localized using either an exteroceptive or an interoceptive body representation. The goal of the present study was to investigate if the body representation selected to plan reaches to somatosensory targets is influenced by the sensory modality of the cue indicating the target’s location. In the first experiment, participants reached to somatosensory targets prompted by either an auditory or a vibrotactile cue. As a baseline condition, participants also performed reaches to visual targets prompted by an auditory cue. Gaze-dependent reaching errors were measured to determine the contribution of the exteroceptive representation to motor planning processes. The results showed that reaches to both auditory-cued somatosensory targets and auditory-cued visual targets exhibited larger gaze-dependent reaching errors than reaches to vibrotactile-cued somatosensory targets. Thus, an exteroceptive body representation was likely used to plan reaches to auditory-cued somatosensory targets but not to vibrotactile-cued somatosensory targets. The second experiment examined the influence of using an exteroceptive body representation to plan movements to somatosensory targets on pre-movement neural activations. Cortical responses to a task-irrelevant visual flash were measured as participants planned movements to either auditory-cued somatosensory or auditory-cued visual targets. Larger responses (i.e., visual-evoked potentials) were found when participants planned movements to somatosensory vs. visual targets, and source analyses revealed that these activities were localized to the left occipital and left posterior parietal areas. These results suggest that visual and visuomotor processing networks were more engaged when using the exteroceptive body representation to plan movements to somatosensory targets, than when planning movements to external visual targets.

Development of spatial orientation skills: an fMRI study.

The ability to orient and navigate in spatial surroundings is a cognitive process that undergoes a prolonged maturation with progression of skills, strategies and proficiency over much of childhood. In the present study, we used functional Magnetic Resonance Imaging (fMRI) to investigate the neurological mechanisms underlying the ability to orient in a virtual interior environment in children aged 10 to 12years of age, a developmental stage in which children start using effective spatial orientation strategies in large-scale surroundings. We found that, in comparison to young adults, children were not as proficient at the spatial orientation task, and revealed increased neural activity in areas of the brain associated with visuospatial processing and navigation (left cuneus and mid occipital area, left inferior parietal region and precuneus, right inferior parietal cortex, right precentral gyrus, cerebellar vermis and bilateral medial cerebellar lobes). When functional connectivity analyses of resting state fMRI data were performed, using seed areas that were associated with performance, increased connectivity was seen in the adults from the right hippocampal/parahippocampal gyrus to the contralateral caudate, the insular cortex, and the posterior supramarginal gyrus; children had increased connectivity from the right paracentral lobule to the right superior frontal gyrus as compared to adults. These findings support the hypothesis that, as children are maturing in their navigation abilities, they are refining and increasing the proficiency of visuospatial skills with a complimentary increase in connectivity of longer-range distributed networks allowing for flexible use of efficient and effective spatial orientation strategies.

Dissociating the role of dorsal and ventral visual streams in object lifting and weight perception

Event Abstract Back to Event Dissociating the role of dorsal and ventral visual streams in object lifting and weight perception Vonne Van Polanen1*, Guy Rens1 and Marco Davare1 1 KU Leuven, Belgium When sequentially lifting a series of differently weighted objects, our fingertip forces are typically scaled according to the weight of the previously lifted object, an effect often referred to as sensorimotor memory [2]. For instance, force rates are higher after the lift of a heavy compared to a light object. Recently, we showed that this effect on force parameters also changes perceptual estimates, where objects are judged lighter after the lift of a heavy compared to a light weight [3]. Here, we aimed to investigate the causal role of the dorsal vs. ventral visual streams in these processes, given they are classically involved in computing motor vs. perceptual parameters, respectively. We used transcranial magnetic stimulation (TMS) to investigate the contribution of the left anterior intraparietal sulcus (aIPS) and lateral occipital (LO) areas, which are important nodes for processing hand-object interactions in the dorsal and ventral streams. Subjects received TMS to either aIPS or LO. Neuronavigation (Brainsight) was used to localize our TMS targets on individual structural brain imaging scans. The left aIPS was defined anatomically as the intersection between the intraparietal and postcentral sulci and LO was located using previously published functional coordinates [1]. Subjects were asked to grip and lift equally sized but differently weighted (light, 2N, or heavy, 6N) objects in a pseudo-randomized order and provide a weight estimate on a self-chosen scale. During object lifting, TMS was applied in a burst of 3 pulses (10Hz) at 120% of the active motor threshold. Three stimulation conditions were compared for each brain area, with stimulation at object contact (dynamic phase), 500 ms after object lift-off (static phase) or no stimulation. We quantified the effect of TMS on perceptual weight estimates, peak grip and load force rates, loading phase duration and mean grip force during stable hold. For each parameter, a mixed ANOVA was performed with TMS target (aIPS or LO) as between-subject factor and TMS condition (dynamic, static, or no stimulation) and object order (light-light, heavy-light, light-heavy, or heavy-heavy) as within-subject factors. When previously lifting a heavy object, peak grip and load force rates were higher and loading phase durations were shorter compared to previously lifting a light object, in line with classical sensorimotor memory effects. It is noteworthy that TMS did not alter this order effect. We only found a general effect of TMS when applied during the dynamic phase, with increased force rate peaks compared to the other TMS conditions. Furthermore, stable grip forces were higher after lifting a heavy object compared to a light one. Interestingly, this effect was cancelled in the aIPS group. No general effect of TMS condition on stable grip force was found. Finally, weight estimations were lower when a light object was preceded by a heavy object compared to a light one, replicating our earlier findings [3]. TMS led to overall lighter weight ratings, independently of the targeted area or timing. Remarkably, the order effect on weight estimations was cancelled when TMS was applied during the static phase over either aIPS or LO. These findings suggest that both aIPS and LO are involved in late phases of object weight perception. Moreover, the role of dorsal and ventral stream areas in mediating sensorimotor memory effects seems limited to aIPS for controlling grip forces in later phases of lifting. Overall, this sheds new light on the interactions between brain networks mediating action and perception during object manipulation.