1,721,018 research outputs found
Occipital Transcranial magnetic stimulation has opposing effects on visual and auditory stimulus detection: Implications for multisensory interactions
No full textMultisensory interactions occur early in time and in low-level cortical areas, including primary cortices. To test current models of early auditory–visual (AV) convergence in unisensory visual brain areas, we studied the effect of transcranial magnetic stimulation (TMS) of visual cortex on behavioral responses to unisensory (auditory or visual) or multisensory (simultaneous auditory–visual) stimulus presentation. Single-pulse TMS was applied over the occipital pole at short delays (30–150 ms) after external stimulus onset. Relative to TMS over a control site, reactions times (RTs) to unisensory visual stimuli were prolonged by TMS at 60–75 ms poststimulus onset (visual suppression effect), confirming stimulation of functional visual cortex. Conversely, RTs to unisensory auditory stimuli were significantly shortened when visual cortex was stimulated by TMS at the same delays (beneficial interaction effect of auditory stimulation and occipital TMS). No TMS-effect on RTs was observed for AV stimulation. The beneficial interaction effect of combined unisensory auditory and TMS-induced visual cortex stimulation matched and was correlated with the RT-facilitation after external multisensory AV stimulation without TMS, suggestive of multisensory interactions between the stimulus-evoked auditory and TMS-induced visual cortex activities. A follow-up experiment showed that auditory input enhances excitability within visual cortex itself (using phosphene-induction via TMS as a measure) over a similarly early time-window (75–120 ms). The collective data support a mechanism of early auditory–visual interactions that is mediated by auditory-driven sensitivity changes in visual neurons that coincide in time with the initial volleys of visual input
The spatial representation of number, time, and serial order following sensory deprivation: A systematic review
No full textThe spatial representation of numerical and temporal information is thought to be rooted in our multisensory experiences. Accordingly, we may expect visual or auditory deprivation to affect the way we represent numerical magnitude and time spatially. Here, we systematically review recent findings on how blind and deaf individuals represent abstract concepts such as magnitude and time (e.g., past/future, serial order of events) in a spatial format. Interestingly, available evidence suggests that sensory deprivation does not prevent the spatial "re-mapping" of abstract information, but differences compared to normally sighted and hearing individuals may emerge depending on the specific dimension considered (i.e., numerical magnitude, time as past/future, serial order). Herein we discuss how the study of sensory deprived populations may shed light on the specific, and possibly distinct, mechanisms subserving the spatial representation of these concepts. Furthermore, we pinpoint unresolved issues that need to be addressed by future studies to grasp a full understanding of the spatial representation of abstract information associated with visual and auditory deprivation
Visual intervention in early onset visual impairment: A review
No full textVision is a primary and motivating sense. Early visual experience derived from the external world is known to have an important impact on the development of central visual pathways, and not surprisingly, visual impairment constitutes a risk factor for overall development. In light of the role of vision in early brain development, infants and young children with visual impairment should be thus entitled to early and effective visual intervention programmes. In this review, we discuss early visual interventions in infants and young children with visual impairment, focusing on their contents and outcomes. We defined a PICO format to critically review different models with a particular focus on parent-mediated and therapist-mediated approaches. We consider protocols that involved direct manipulation or improvement of the infants' visual inputs or were based on behavioural strategies and communication towards infants with visual impairment. We also provide an overview of the effectiveness of these protocols. A total of nine intervention protocols were selected for the purposes of this review. Substantial agreement regarding the importance of promoting the enrichment of infant environments, and more specifically in the context of active play that engages the whole family, has been reported in most of the studies. However, there is no clear agreement on methodological aspects, including clinical population characteristics, outcome measures, length of treatment and follow-up programmes. Further high-quality, carefully designed and adequately reported studies are needed in order to improve the clinical efficacy of these approaches to treating infants with visual impairment
The effect of hand movements on numerical bisection judgments in early blind and sighted individuals
No full textRecent evidence suggests that in representing numbers blind individuals might be affected differently by proprioceptive cues (e.g., hand positions, head turns) than are sighted individuals. In this study, we asked a group of early blind and sighted individuals to perform a numerical bisection task while executing hand movements in left or right peripersonal space and with either hand. We found that in bisecting ascending numerical intervals, the hemi-space in which the hand was moved (but not the moved hand itself) influenced the bisection bias similarly in both early blind and sighted participants. However, when numerical intervals were presented in descending order, the moved hand (and not the hemi-space in which it was moved) affected the bisection bias in all participants. Overall, our data show that the operation to be performed on the mental number line affects the activated spatial reference frame, regardless of participants' previous visual experience. In particular, both sighted and early blind individuals' representation of numerical magnitude is mainly rooted in world-centered coordinates when numerical information is given in canonical orientation (i.e., from small to large), whereas hand-centered coordinates become more relevant when the scanning of the mental number line proceeds in non-canonical direction
White matter changes associated with cognitive visual dysfunctions in children with cerebral palsy: A diffusion tensor imaging study
No full textThe effect of musical expertise on the representation of space
Get PDFConsistent evidence suggests that pitch height may be represented in a spatial format, having both a vertical and a horizontal representation. The spatial representation of pitch height results into response compatibility effects for which high pitch tones are preferentially associated to up-right responses, and low pitch tones are preferentially associated to down-left responses (i.e., the Spatial-Musical Association of Response Codes (SMARC) effect), with the strength of these associations depending on individuals’ musical skills. In this study we investigated whether listening to tones of different pitch affects the representation of external space, as assessed in a visual and haptic line bisection paradigm, in musicians and non musicians. Low and high pitch tones affected the bisection performance in musicians differently, both when pitch was relevant and irrelevant for the task, and in both the visual and the haptic modality. No effect of pitch height was observed on the bisection performance of non musicians. Moreover, our data also show that musicians present a (supramodal) rightward bisection bias in both the visual and the haptic modality, extending previous findings limited to the visual modality, and consistent with the idea that intense practice with musical notation and bimanual instrument training affects hemispheric lateralization.Version of Recor
The role of prefrontal and parietal cortices in esthetic appreciation of representational and abstract art: a TMS study
No full textTo explain the biological foundations of art appreciation is to explain one of our species' distinctive traits. Previous neuroimaging and electrophysiological studies have pointed to the prefrontal and the parietal cortex as two critical regions mediating esthetic appreciation of visual art. In this study, we applied transcranial magnetic stimulation (TMS) over the left prefrontal cortex and the right posterior parietal cortex while participants were evaluating whether they liked, and by how much, a particular painting. By depolarizing cell membranes in the targeted regions, TMS transiently interferes with the activity of specific cortical areas, which allows clarifying their role in a given task. Our results show that both regions play a fundamental role in mediating esthetic appreciation. Critically though, the effects of TMS varied depending on the type of art considered (i.e. representational vs. abstract) and on participants' a-priori inclination toward one or the other
The Ego-Moving Metaphor of Time Relies on Visual Experience: No Representation of Time Along the Sagittal Space in the Blind
Get PDFIn many cultures, humans conceptualize the past as behind the body and the future as in front. Whether this spatial mapping of time depends on visual experience is still not known. Here, we addressed this issue by testing early-blind participants in a space-time motor congruity task requiring them to classify a series of words as referring to the past or the future by moving their hand backward or forward. Sighted participants showed a preferential mapping between forward movements and future-words and backward movements and past-words. Critically, blind participants did not show any such preferential time-space mapping. Furthermore, in a questionnaire requiring participants to think about past and future events, blind participants did not appear to perceive the future as psychologically closer than the past, as it is the case of sighted individuals. These findings suggest that normal visual development is crucial for representing time along the sagittal spac
Assessing visuospatial processing in cerebral visual impairment using a novel and naturalistic static visual search task
Get PDFBackground: Cerebral visual impairment (CVI) is a brain based visual disorder associated with the maldevelopment of central visual pathways. Individuals with CVI often report difficulties finding a target of interest in cluttered and crowded visual scenes. However, it remains unknown how manipulating task demands and other environmental factors influence visual search performance in this population.Aim: We developed a novel and naturalistic virtual reality (VR) based static visual search task combined with eye tracking called the "virtual toy box" to objectively assess visual search per-formance in CVI.Methods and procedures: A total of 38 individuals with CVI (mean age 13.18 years +/- 3.58 SD) and 53 controls with neurotypical development (mean age 15.25 years +/- 5.72 SD) participated in the study. In a first experiment, study subjects were instructed to search for a preselected toy pre-sented among a varying number of surrounding distractor toys (set size ranging from 1 to 36 items). In a second experiment, we assessed the effects of manipulating item spacing and the size of the visual area explored (field of view; FOV).Outcomes and results: Behavioral outcomes collected were success rate, reaction time, gaze error, visual search area, and off-screen percent (an index of task compliance). Compared to age -matched controls, participants with CVI showed an overall impairment with respect to all the visual search outcomes of interest. Specifically, individuals with CVI were less likely and took longer to find the target, and search patterns were less accurate and precise compared to controls. Visual search response profiles were also comparatively less efficient and were associated with a slower initial pre-search (visual orienting) response as indexed by higher slope and intercept values derived from the analysis of reaction time x set size functions. Search performance was also more negatively affected in CVI at the smallest as well as largest spacing conditions tested, while increasing FOV was associated with greater decreased gaze accuracy and precisionConclusions and implications: These results are consistent with a general profile of impaired visual search abilities in CVI as well as worsening performance with increased visual task demands and an overall sensitivity to visual clutter and crowding. The observed profile of impaired visual search performance may be associated with dysfunctions related to how visual selective attention is deployed in individuals with CVI
Developmental coordination disorder and cerebral visual impairment: What is the association?
Get PDFIntroduction: Children with Developmental Coordination Disorder (DCD) experience impairments beyond motor planning, affecting visual perceptual and visual-motor integration abilities, similar to children with Cerebral Visual Impairment (CVI), making it challenging to distinguish between the two conditions. This study aimed to identify convergences and divergences in the clinical, neuropsychological, and functional vision-related skills of children with DCD and CVI. Methods: An assessment of the neuropsychological profile (cognitive, visual cognitive, and motor coordination skills) and visual acuity were conducted on 65 children with DCD (mean age: 8 years, 1 month; SD: 1 year, 6 months) and 35 children with CVI (mean age: 8 years, 5 months; SD: 2 years, 6 months) and compared between the two groups. The CVI-Inventory (CVI-I) was used to evaluate functional vision-related problems and to cluster subjects. Results: Visual attention, visual perception, global motor coordination, and visual constructive scores didn't differ between the two groups even if children with CVI showed lower scores in the intellectual, visual, visual cognitive, and motor abilities. The overlap index confirmed an overlap on most of the variables considered. Six discriminative questions from the CVI-I clustered subjects into two groups: the first, with more children with CVI (62.9 %) and a more compromised neuropsychological profile, and the second, with more children with DCD (86.7 %). Conclusion: DCD and CVI share both similarities and differences. Low visual acuity, low IQ scores, severe visual-motor integration challenges, and difficulties with fine motor and balance skills should prompt clinicians to screen for CVI in children with DCD. Specific functional vision-related problems can assist in this differentiation
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