Left Hemispace Research Articles

Visual perceptual learning is enhanced by training in the illusory far space.

Visual objects in the peripersonal space (PPS), are perceived faster than farther ones, appearing in the extrapersonal space (EPS). This shows preferential processing for visual stimuli near our body. Such an advantage should favor visual perceptual learning occurring near, as compared to far from observers, but opposite evidence has been recently provided from online testing protocols, showing larger perceptual learning in the far space. Here, we ran two laboratory-based experiments investigating whether visual training in PPS and EPS has different effects. We used the horizontal Ponzo Illusion to create a lateralized depth perspective while participants completed a visual search task in which they reported whether or not a specific target object orientation (e.g., a triangle pointing upward) was present amongst distractors. This task was completed before and after a training phase in either the (illusory) near or far space for one hour. In Experiment 1, the near space was in the left hemispace, whereas in Experiment 2 it was in the right. Results showed that, in both experiments, participants were more accurate after training in the far space, whereas training in the near space led to either improvement in the far space (Exp. 1), or no change (Exp. 2). Moreover, we found a larger visual perceptual learning when stimuli were presented in the left compared to the right hemispace. Differently from visual processing, visual perceptual learning is more effective in the far space. We propose that depth is a key dimension that can be used to improve human visual learning.

Virtual reality gameplay classification illustrates the multidimensionality of visuospatial neglect.

Brain injuries can significantly impact mental processes and lead to hidden disabilities not easily detectable. Traditional methods for assessing these impacts are imprecise, leading to unreliable prevalence estimates and treatments with uncertain effectiveness. Immersive virtual reality has shown promise for assessment, but its use as a standalone tool is rare. Our research focused on developing and validating a standalone immersive virtual reality classification system for unilateral spatial neglect, a condition common following brain injury characterized by inattention to one side of space. Our study involved 51 brain injury inpatients and 30 controls, all engaging with 'The Attention Atlas', an immersive virtual reality game for testing visual search skills. Our classification system aimed to identify patients with neglect, 'minor atypicality' (indicative of inattention not consistent enough to be labelled as neglect) or non-neglect. This categorization was based on a simple mathematical definition, utilizing gameplay to describe spatial orientation (to the left or right side) and attentional challenge (indicative of search inefficiency). These metrics were benchmarked against a normative model to detect atypical visual search, which refers to gameplay beyond the usual bounds. The combination of neglected side, orientation and challenge factors was used to categorize neglect. We discovered a strong correlation between atypical visual search patterns and neglect risk factors, such as middle cerebral artery stroke, parietal injuries and existing neglect diagnoses (Poisson regression incidence rate ratio = 7.18, 95% confidence interval = 4.41-11.90). In our study, immersive virtual reality-identified neglect in one-fourth of the patients (n = 13, 25.5%), minor atypicality in 17.6% (n = 9) and non-neglect in the majority, 56.9% (n = 29). This contrasts with standard assessments, which detected neglect in 17.6% (n = 9) of cases and had no intermediate category. Our analysis determined six categories of neglect, the most common being left hemispace neglect with above-median orientation and challenge scores. Traditional assessments were not significantly more accurate (accuracy = 84.3%, P = 0.06) than a blanket assumption of non-neglect. Traditional assessments were also relatively insensitive in detecting immersive virtual reality-identified neglect (53.8%), particularly in less severe cases and those involving right-side inattention. Our findings underline the effectiveness of immersive virtual reality in revealing various dimensions of neglect, surpassing traditional methods in sensitivity and detail and operating independently from them. To integrate immersive virtual reality into real-world clinical settings, collaboration with healthcare professionals, patients and other stakeholders is crucial to ensure practical applicability and accessibility.

Pointing in cervical dystonia patients

IntroductionThe normal hemispheric balance can be altered by the asymmetric sensorimotor signal elicited by Cervical Dystonia (CD), leading to motor and cognitive deficits.MethodsDirectional errors, peak velocities, movement and reaction times of pointing towards out-of-reach targets in the horizontal plane were analysed in 18 CD patients and in 11 aged-matched healthy controls.ResultsCD patients displayed a larger scatter of individual trials around the average pointing direction (variable error) than normal subjects, whatever the arm used, and the target pointed. When pointing in the left hemispace, all subjects showed a left deviation (constant error) with respect to the target position, which was significantly larger in CD patients than controls, whatever the direction of the abnormal neck torsion could be. Reaction times were larger and peak velocities lower in CD patients than controls.DiscussionDeficits in the pointing precision of CD patients may arise from a disruption of motor commands related to the sensorimotor imbalance, from a subtle increase in shoulder rigidity or from a reduced agonists activation. Their larger left bias in pointing to left targets could be due to an increased right parietal dominance, independently upon the direction of head roll/jaw rotation which expands the left space representation and/or increases left spatial attention. These deficits may potentially extend to tracking and gazing objects in the left hemispace, leading to reduced skills in spatial-dependent motor and cognitive performance.

Comparison of uni- and multimodal motion stimulation on visual neglect: A proof-of-concept study

Spatial neglect is characterized by the failure to attend stimuli presented in the contralesional space. Typically, the visual modality is more severely impaired than the auditory one. This dissociation offers the possibility of cross-modal interactions, whereby auditory stimuli may have beneficial effects on the visual modality. A new auditory motion stimulation method with music dynamically moving from the right to the left hemispace has recently been shown to improve visual neglect. The aim of the present study was twofold: a) to compare the effects of unimodal auditory against visual motion stimulation, i.e., smooth pursuit training, which is an established therapeutical approach in neglect therapy and b) to explore whether a combination of auditory + visual motion stimulation, i.e., multimodal motion stimulation, would be more effective than unimodal auditory or visual motion stimulation. 28 patients with left-sided neglect due to a first-ever, right-hemispheric subacute stroke were included. Patients either received auditory, visual, or multimodal motion stimulation. The between-group effect of each motion stimulation condition as well as a control group without motion stimulation was investigated by means of a one-way ANOVA with the patient’s visual exploration behaviour as an outcome variable. Our results showed that unimodal auditory motion stimulation is equally effective as unimodal visual motion stimulation: both interventions significantly improved neglect compared to the control group. Multimodal motion stimulation also significantly improved neglect, however, did not show greater improvement than unimodal auditory or visual motion stimulation alone. Besides the established visual motion stimulation, this proof-of-concept study suggests that auditory motion stimulation seems to be an alternative promising therapeutic approach to improve visual attention in neglect patients. Multimodal motion stimulation does not lead to any additional therapeutic gain. In neurorehabilitation, the implementation of either auditory or visual motion stimulation seems therefore reasonable.

Feasibility of hemispatial neglect rehabilitation with virtual reality-based visual exploration therapy among patients with stroke: randomised controlled trial.

Hemispatial neglect (HSN) was diagnosed using a virtual reality-based test (FOPR test) that explores the field of perception (FOP) and field of regard (FOR). Here, we developed virtual reality-visual exploration therapy (VR-VET) combining elements from the FOPR test and visual exploration therapy (VET) and examined its efficacy for HSN rehabilitation following stroke. Eleven participants were randomly assigned to different groups, training with VR-VET first then waiting without VR-VET training (TW), or vice versa (WT). The TW group completed 20 sessions of a VR-VET program using a head-mounted display followed by 4 weeks of waiting, while the WT group completed the opposite regimen. Clinical HSN measurements [line bisection test (LBT), star cancellation test (SCT), Catherine Bergego Scale (CBS), CBS perceptual-attentional (CBS-PA), and CBS motor-explanatory (CBS-ME)] and FOPR tests [response time (RT), success rate (SR), and head movement (HM) for both FOP and FOR] were assessed by blinded face-to-face assessments. Five and six participants were allocated to the TW and WT groups, respectively, and no dropout occurred throughout the study. VR-VET considerably improved LBT scores, FOR variables (FOR-RT, FOR-SR), FOP-LEFT variables (FOP-LEFT-RT, FOP-LEFT-SR), and FOR-LEFT variables (FOR-LEFT-RT, FOR-LEFT-SR) compared to waiting without VR-VET. Additionally, VR-VET extensively improved FOP-SR, CBS, and CBS-PA, where waiting failed to make a significant change. The VR-VET made more improvements in the left hemispace than in the right hemispace in FOP-RT, FOP-SR, FOR-RT, and FOR-SR. The observed improvements in clinical assessments and FOPR tests represent the translatability of these improvements to real-world function and the multi-dimensional effects of VR-VET training. https://clinicaltrials.gov/ct2/show/NCT03463122, identifier NCT03463122.

Evaluating Self-Directed Behaviours and Their Association with Emotional Arousal across Two Cognitive Tasks in Bonobos (Pan paniscus).

Self-directed behaviours (SDBs) are widely used as markers of emotional arousal in primates, and are commonly linked to negative arousal, or are used as indicators of stress or poor welfare. However, recent studies suggest that not all SDBs have the same function. Moreover, lateralisation in the production of these behaviours has been suggested to be associated with emotional processing. Hence, a better understanding of the production and the asymmetry of these displacement behaviours is needed in a wider range of species in order to confirm their reliability as indicators of emotional arousal. In the current study, we experimentally evaluated the production and asymmetry of SDBs in zoo-housed bonobos during two cognitive touchscreen tasks. Overall, nose wipes were most commonly observed, followed by gentle self-scratches, and rough self-scratches. The rates of nose wipes and rough self-scratches increased with incorrect responses, suggesting that these behaviours indicate arousal and possibly frustration. Rough self-scratching was additionally more directed towards the left hemispace after incorrect responses. In contrast, gentle self-scratching increased after correct responses in one study, possibly linking it with positive arousal. We also tested if left-handed bonobos showed greater behavioural reactivity towards incorrect responses, but found no evidence to confirm this hypothesis. Our results shed light on potential different mechanisms behind separate SDBs. We therefore provide nuance to the use of SDBs as indicator of emotional arousal in bonobos.

Using visual speech at the cocktail-party: CNV evidence for early speech extraction in younger and older adults

The comprehension of spoken language benefits from visual speech information. One reason for this is the temporal lead of mouth and lip movements over the onset of acoustic speech utterance. Here, we investigated EEG event-related potentials preceding acoustic speech, focusing on a fronto-central contingent negative variation (CNV) prior to the onset of acoustic speech. We explored influences of expectation and visual speech content as well as age-related differences. In a multi-talker two-alternative speech discrimination task, younger and older subjects responded to short words presented simultaneously to competing speech under free-field conditions. Subjects were always presented with audiovisual speech stimuli, while the modality containing the task-relevant information was modulated in a block-wise fashion. Thus, task-relevant speech information was either available as audio-visually congruent stimuli or only in the visual (visual-valid) or the auditory (auditory-valid) modality. Subjects were instructed to fixate a pre-specified position in the left or right hemispace. In each task block, task-relevant stimuli appeared either at the pre-specified position (standard trials, 80%) or at a rare deviant position (20%). Target words were recognized faster and more accurately when visual speech information was available. The CNV prior to the acoustic speech onset was more pronounced with visual-informative than with visually non-informative speech. Especially in the younger group, a less pronounced CNV occurred with purely visual speech in deviant trials, that is, when a task-irrelevant speech stimulus appeared instead of the expected target stimulus. The results indicate that processes preceding the onset of acoustic speech are modulated by expectations and visual speech content, while age differences are rather small.

Ambiguous handedness and visuospatial pseudoneglect in schizotypy in physical and computer-generated virtual environments

Virtual reality (VR) technology has increased clinical attention in the health care of schizophrenia spectrum disorders in both diagnoses of the symptoms and assessment of schizotypal traits. However, the exact nature of VR-induced positive treatment effect in schizotypy is still unknown. In this study, VR technology was used as a non-invasive neurocognitive trigger to test the asymmetric visuospatial representational instability found in individuals with high schizotypy. The study aimed to reveal the brain functional hemispheric laterality in physical and virtual realities in individuals with schizotypal traits. Fifty-one healthy, right-handed participants (24 males and 27 females) were enrolled through public advertisements. Hemispheric functional asymmetry was measured by the Line Bisection Task (LBT). The results revealed that (a) LBT bias in the physical reality showed a handedness-related leftward pseudoneglect, however, similar handedness-related pseudoneglect in VR has not been found. (b) Comparing LBT bias in physically real and VR environments showed rightward drift in VR environments independently to the degree of handedness. (c) The schizotypy has no association with handedness, however, the cognitive schizotypy is related to the LBT bias. Higher cognitive schizotypy in VR associated with left hemispatial pseudoneglect. In conclusion, schizotypy is associated with ambiguous behavioral and cognitive functional laterality. In individuals with high cognitive schizotypy, the VR environment enhanced the representational articulation of the left hemispace. This effect may be originated from the enhancement of the right hemisphere overactivation and is followed by a lower mental control of the overt behavior.

Pitch-Luminance Crossmodal Correspondence in the Baby Chick: An Investigation on Predisposed and Learned Processes.

Our senses are constantly reached by a multitude of stimuli from all different sensory modalities. To create a coherent representation of the environment, we must integrate the various unimodal inputs that refer to the same object into a single multimodal representation. In some cases, however, we tend to bind certain properties of the stimuli without any apparent reason, which is a phenomenon named crossmodal correspondence. For instance, we match a spiky or a rounded shape with the sound “Kiki” or “Bouba”, respectively. Similarly, we associate the left hemispace with low luminance and the right one with high luminance. Instances of crossmodal correspondences were described also in other mammals, and recently, a case of space-luminance crossmodal correspondence was reported in birds (i.e., domestic chicks). Here, we investigate the presence of pitch–luminance crossmodal correspondence in three-day-old chicks, employing experimental methods that exploit either predisposed or learned processes. While failing to report evidence for this phenomenon, we discuss the difference between statistical and structural crossmodal correspondences and the possible role of environmental factors in determining their emergence. Moreover, we discuss the importance of the different experimental methodologies to investigate distinct aspects of this perceptual phenomenon to reach a deeper understanding and unveil the role of innate vs. learned mechanisms.

Leftward Spatial Bias in Dialyzed Patients With End-Stage Renal Disease: A Sign of Right Hemispheric Attentional Activation or Impaired Left-Sided Disengagement?

In the horizontal line bisection task, patients with end-stage renal disease (ESRD) treated with dialysis typically have an increase in the normal leftward attentional bias. It is not clear, however, whether this increased bias is related to an increase of attention toward left hemispace or impaired disengagement from left-sided stimuli. Non-demented patients with ESRD who were being treated with dialysis and demographically matched healthy controls attempted to bisect series of horizontal lines composed of two segments of unequal length and width, with the longer segment placed to the right or left. To test for the presence of a global spatial attentional bias, participants attempted to find the middle of the whole line. To test for focal attentional engagement and attentional disengagement, participants were asked to bisect only the longer segment of these compound lines. For the global condition, both patients and healthy controls were biased toward the longer segment and more so to the left. In the focal condition, when the longer segment was on the right side, both groups deviated their bisections toward the shorter segment. However, when in the focal condition the longer segment was on the left healthy controls deviated their bisection significantly more rightwards than did the patients, whereas with the longer segment on the right, the patients and healthy controls did not differ in their bias. These results suggest that the previously recognized dysfunction of the right fronto-subcortical attentional network in dialyzed patients might account for the results of the current study.

Rhythmic and non-rhythmic auditory precues: Multiple mechanisms mediating movement performance

Rhythmic auditory stimuli presented before a goal-directed movement have been found to improve temporal and spatial movement outcomes. However, little is known about the mechanisms mediating these benefits. The present experiment used three types of auditory stimuli to probe how improved scaling of movement parameters, temporal preparation and an external focus of attention may contribute to changes in movement performance. Three types of auditory stimuli were presented for 1200ms before movement initiation; three metronome beats (RAS), a tone that stayed the same (tone-same), a tone that increased in pitch (tone-change) and a no sound control, were presented with and without visual feedback for a total of eight experimental conditions. The sound was presented before a visual go-signal, and participants were instructed to reach quickly and accurately to one of two targets randomly identified in left and right hemispace. Twenty-two young adults completed 24 trials per blocked condition in a counterbalanced order. Movements were captured with an Optotrak 3D Investigator, and a 4(sound) by 2(vision) repeated measures ANOVA was used to analyze dependant variables. All auditory conditions had shorter reaction times than no sound. Tone-same and tone-change conditions had shorter movement times and higher peak velocities, with no change in trajectory variability or endpoint error. Therefore, rhythmic and non-rhythmic auditory stimuli impacted movement performance differently. Based on the pattern of results we propose multiple mechanisms impact movement planning processes when rhythmic auditory stimuli are present.

Auditory spatial attention gradients and cognitive control as a function of vigilance.

Selection and effort are central to attention, yet it is unclear whether they draw on a common pool of cognitive resources, and if so, whether there are differences for early versus later stages of cognitive processing. This study assessed effort by quantifying the vigilance decrement, and spatial processing at early and later stages as a function of time-on-task. Participants performed an auditory spatial attention task, with occasional "catch" trials requiring no response. Psychophysiological measures included bilateral cerebral blood flow (transcranial Doppler), pupil dilation, and blink rate. The shape of attention gradients using reaction time indexed early processing, and did not significantly vary over time. Later stimulus-response conflict was comparable over time, except for a reduction to left hemispace stimuli. Target and catch trial accuracy decreased with time, with a more abrupt decrease for catch versus target trials. Diffusion decision modeling found progressive decreases in information accumulation rate and non-decision time, and the adoption of more liberal response criteria. Cerebral blood flow increased from baseline and then decreased over time, particularly in the left hemisphere. Blink rate steadily increased over time, while pupil dilation increased only at the beginning and then returned towards baseline. The findings suggest dissociations between resources for selectivity and effort. Measures of high subjective effort and temporal declines in catch trial accuracy and cerebral blood flow velocity suggest a standard vigilance decrement was evident in parallel with preserved selection. Different attentional systems and classes of computations that may account for dissociations between selectivity versus effort are discussed.

Impaired visual search in posterior cortical atrophy vs. typical Alzheimer's disease

BackgroundPosterior cortical atrophy (PCA) is a neurocognitive disorder characterized by difficulty localizing in space. Recognizing PCA is important because it is usually missed early in its course and may result from a number of neurological disorders other than Alzheimer's disease (AD). ObjectiveThis study aimed to clarify whether impaired visual search tasks of spatial localization distinguished patients with PCA from those with other more typical dementias as well as from healthy control (HC) subjects. MethodsTwelve patients meeting neuroimaging-supported Consensus Criteria for PCA, 12 comparably advanced patients with amnestic-predominant typical AD (tAD), and 24 HC participants were compared on tests of untimed and timed visual search, spatial neglect, mental rotation, environmental orientation, visuospatial construction, and face recognition. ResultsOnly abnormalities in untimed and timed visual search and environmental orientation distinguished the PCA patients from both the tAD group and the HC group without also distinguishing the tAD patients from HC's. The PCA patients also had a tendency to greater difficulty scanning left hemispace compared to HC's. Visuospatial constructions, although worse in PCA, and face recognition were impaired in both dementia groups. ConclusionsThese findings support the concept of PCA as a disorder of spatial processing and localization, indicating that visual search tasks are particularly sensitive and specific for detecting PCA and distinguishing it from more typical dementia syndromes.

Spatial artistic displays of emotional valence

ABSTRACT Background: While right-left hemispheric valence dichotomies have been demosntrated in various lesion stidues, it not entirely known if these dichotomies are portrayed in art. Methods: We examined 192 paintings to learn if there is an association between paintings that portray happy-positive or sad-negative scenes and the agent looking to the right or left side relative to their head’s midsagittal plane. Results: There were 38 paintings with a positive valence and 32 with a negative valence in which the eyes were turned rightward or leftward. Of 38 positive valence paintings, 28 had the agent looking rightward, and 10 looking leftward. Of 32 negative valence paintings, 15 had the agent looking rightward and 17 leftward. Discussion: Hemisphere activation is associated with contralateral deviation of the eyes. Whereas the right hemisphere mediates negative emotions allocates spatial attention to both left and right hemispace, the left hemisphere primarily allocates attention to the right. Since the left hemisphere appears to mediate positive emotions and the right hemisphere negative emotions, results from this study are consistent with hemispheric emotional valence attentional hypotheses. However, the relationship between artist knowledge about gaze and the utilization of gaze direction to portray emotional experiences is not known.

Attention capture by salient object groupings in the neglected visual field

The integration of fragmentary parts into coherent whole objects has been proposed either to rely on the availability of attentional resources or to arise automatically, that is, from preattentive processing (prior to the engagement of selective attention). In the present study, these two alternative accounts were tested in a group of neglect patients with right-hemisphere parietal brain damage and associated deficits of selective attention in the left (visual) hemispace. The reported experiment employed a search task that required detection of targets in the left and/or right hemifields, which were embedded in configurations that consisted of variants of Kanizsa figures. The results showed that a salient, grouped Kanizsa triangle presented within the unattended, left hemifield can substantially improve contralesional target detection, though the very same triangle configuration does not facilitate target detection in the impaired hemifield when presented together with an ipsilesional, but non-salient (i.e., structurally non-integrated, isolated) target. That is, attention is captured by the grouped object in the impaired hemispace only when it is not engaged in the processing of an (isolated) object in the attended hemispace. This demonstrates that both part-to-whole-object integration and search guidance by salient, integrated objects crucially require attentional resources.

FOPR test: a virtual reality-based technique to assess field of perception and field of regard in hemispatial neglect

BackgroundWe previously proposed a novel virtual reality-based method to assess human field of perception (FOP) and field of regard (FOR), termed the FOPR test. This study assessed the diagnostic validity of the FOPR test for hemispatial neglect (HSN).MethodsWe included 19 stroke patients with a lesion in the right hemisphere and with HSN (HSN+SS), 22 stroke patients with a lesion in the right hemisphere and without HSN (HSN−SS), and 22 healthy controls aged 19–65 years. The success rate (SR) and response time (RT) in the FOPR test for both FOP and FOR were assessed (FOP-SR, FOR-SR, FOP-RT, and FOR-RT, respectively). Using a Bland–Altman plot, agreements between the FOPR test and conventional tests were confirmed, and the FOPR test accuracy was verified using the support vector machine (SVM). Measured values were analysed using ANOVA and Kruskall–Wallis tests for group comparison.ResultsThe Bland–Altman plot showed good agreement between FOPR test and conventional tests; individuals within 95% agreement limits were within the range of 94.8–100.0%. The SVM classification accuracy, using FOP and FOR variables from the left hemispace, ranged from 83.3 to 100.0% in a binary classification (HSN vs non-HSN). The FOPR test demonstrated differences in SR and RT for both FOP and FOR across the groups.ConclusionThe FOPR test was valid for the HSN diagnosis and provided quantitative and intuitive information regarding visuospatial function. Furthermore, it might enhance our understanding of visuospatial function including HSN by applying the time relative component and concepts of perception and exploration, FOP and FOR.Trial registration: NCT03463122. Registered 13 March 2018, retrospectively registered.

Tactile numerosity is coded in external space

Humans, and several non-human species, possess the ability to make approximate but reliable estimates of the number of objects around them. Alike other perceptual features, numerosity perception is susceptible to adaptation: exposure to a high number of items causes underestimation of the numerosity of a subsequent set of items, and vice versa. Several studies have investigated adaptation in the auditory and visual modality, whereby stimuli are preferentially encoded in an external coordinate system. As tactile stimuli are primarily coded in an internal (body-centered) reference frame, here we ask whether tactile numerosity adaptation operates based on internal or external spatial coordinates as it occurs in vision or audition. Twenty participants performed an adaptation task with their right hand located either in the right (uncrossed) or left (crossed) hemispace, in order for the two hands to occupy either two completely different positions, or the same position in space, respectively. Tactile adaptor and test stimuli were passively delivered either to the same (adapted) or different (non-adapted) hands. Our results show a clear signature of tactile numerosity adaptation aftereffects with a pattern of over- and under-estimation according to the adaptation rate (low and high, respectively). In the uncrossed position, we observed stronger adaptation effects when adaptor and test stimuli were delivered to the “adapted” hand. However, when both hands were aligned in the same spatial position (crossed condition), the magnitude of adaptation was similar irrespective of which hand received adaptor and test stimuli. These results demonstrate that numerosity information is automatically coded in external coordinates even in the tactile modality, suggesting that such a spatial reference frame is an intrinsic property of numerosity processing irrespective of the sensory modality.

A leftward bias negatively correlated with performance is selectively displayed by domestic chicks during rule reversal (not acquisition)

ABSTRACT In order to face a constantly changing environment, animals need to be able to update their knowledge of the world on the basis of new information. Often, this means to inhibit a previously acquired response and flexibly change their behaviour to produce a new response. Here, we measured such abilities in young domestic chicks, employing a Colour Reversal Learning Task. During the acquisition phase, 17 one-week-old male chicks had to learn to peck on one of two coloured boxes to obtain a food reward. After reaching criterion, chicks underwent a reversal phase in which the previously learned colour-reward contingency was swapped. As expected from the literature, chicks performed better in the acquisition phase with respect to the reversal phase. Results moreover highlighted the presence of a lateralized bias selectively during reversal: chicks performed better if the stimulus rewarded was located in the left hemispace (processed by the right hemisphere). Interestingly, the bias correlated with the individual difficulty, i.e., it was stronger in those chicks which needed more trials to complete the reversal session. The present study contributes evidence in support of behavioural flexibility in young chicks, along with a novel perspective on lateralized mechanisms that might underlie such ability.

The effects of hemispheric dominance, literacy acquisition, and handedness on the development of visuospatial attention: A study in preschoolers and second graders

A tendency to over-attend the left side of the space (i.e., pseudoneglect) has been repeatedly reported in Western adult populations and is supposed to reflect a right hemisphere dominance in the control of visuospatial attention. This neurobiological hypothesis has been partially challenged by growing evidence showing that pseudoneglect is profoundly triggered by cultural practices such as reading and writing habits. Accordingly, more recent theoretical accounts suggest a strict coupling between nature and nurture dimensions at the origins of such bias. To further explore this possibility, here we first administered a digitized cancellation task to right-handed Western children before and after literacy acquisition. Results showed an incremental leftward shift of attention in the cancellation of the first target and an increasing preference for a left-to-right visual search from preschoolers to second graders. Yet, despite these differences, the overall distribution of visuospatial attention was biased to the left in both groups. To explore the role of handedness in visuospatial asymmetries, we also tested a group of left-handed second graders. Results showed an impact of handedness on visuospatial performance, with an accentuated rightward-oriented visual search for left-handed children, although the overall distribution of attention was again biased to the left hemispace. Taken together, these findings do not provide support to a pure neurobiological view of visuospatial biases. Rather, our study indicates that the control of visuospatial attention is mediated by a dynamic interplay among biological (i.e., right hemisphere dominance), biomechanical (i.e., hand dominance), and cultural (i.e., reading habits) factors.

Peritoneal Cysts and Ovary: A Potential Anatomic Dead Spaces for Ovarian Entrapment

Many names have been used across the medical literature for peritoenal cysts. Pelvic peritoenal cysts may occur mostly after surgery or any pelvic pathology. History of surgery seems the main cause that traumatized surfaces, especially peritoneal edges and exposed retroperitoneal tissue become adhesive and can lead to the formation of new pouches. The occurrence of pelvic peritoneal cysts is rare but almost all affected patients are premenopausal women. It brings to mind that functioning ovaries are related to pelvic peritoneal cyst. On the other hand, peritoenal cysts are mostly located on left side of pelvis. The pelvic space is separated into right and left hemi-spaces in midline by their border with recto-sigmoid and uterus or in cases with a previous hysterectomy, with vaginal cuff and bladder. These spaces create potential anatomic dead spaces for peritoneal cyst housed an ovary. The role of the pelvic dead spaces and their surrounding anatomic structures has never been questioned before why peritoenal cysts mostly prefer to develop on left side of pelvis. Nowadays, as the functioning ovaries are left during hysterectomies and visceral peritoneum left unclosed, pelvic peritoneal cysts may occur more frequently in the future than that of in the past. We would like to share our comments on the subject in this new era. Keywords: Hysterectomy; peritoneal cyst; ovarian cyst Special Issue of Health Sciences DOI: 10.7176/JSTR/6-03-27