RESUMO
Hippocampal place cells are influenced by both self-motion (idiothetic) signals and external sensory landmarks as an animal navigates its environment. To continuously update a position signal on an internal 'cognitive map', the hippocampal system integrates self-motion signals over time, a process that relies on a finely calibrated path integration gain that relates movement in physical space to movement on the cognitive map. It is unclear whether idiothetic cues alone, such as optic flow, exert sufficient influence on the cognitive map to enable recalibration of path integration, or if polarizing position information provided by landmarks is essential for this recalibration. Here, we demonstrate both recalibration of path integration gain and systematic control of place fields by pure optic flow information in freely moving rats. These findings demonstrate that the brain continuously rebalances the influence of conflicting idiothetic cues to fine-tune the neural dynamics of path integration, and that this recalibration process does not require a top-down, unambiguous position signal from landmarks.
Assuntos
Fluxo Óptico , Células de Lugar , Ratos Long-Evans , Animais , Fluxo Óptico/fisiologia , Ratos , Masculino , Células de Lugar/fisiologia , Sinais (Psicologia) , Percepção Espacial/fisiologia , Hipocampo/fisiologia , Hipocampo/citologiaRESUMO
Optic flow provides useful information in service of spatial navigation. However, whether brain networks supporting these two functions overlap is still unclear. Here we used Activation Likelihood Estimation (ALE) to assess the correspondence between brain correlates of optic flow processing and spatial navigation and their specific neural activations. Since computational and connectivity evidence suggests that visual input from optic flow provides information mainly during egocentric navigation, we further tested the correspondence between brain correlates of optic flow processing and that of both egocentric and allocentric navigation. Optic flow processing shared activation with egocentric (but not allocentric) navigation in the anterior precuneus, suggesting its role in providing information about self-motion, as derived from the analysis of optic flow, in service of egocentric navigation. We further documented that optic flow perception and navigation are partially segregated into two functional and anatomical networks, i.e., the dorsal and the ventromedial networks. Present results point to a dynamic interplay between the dorsal and ventral visual pathways aimed at coordinating visually guided navigation in the environment.
Assuntos
Mapeamento Encefálico , Encéfalo , Fluxo Óptico , Navegação Espacial , Humanos , Fluxo Óptico/fisiologia , Encéfalo/fisiologia , Encéfalo/diagnóstico por imagem , Navegação Espacial/fisiologia , Mapeamento Encefálico/métodos , Neuroimagem/métodos , Vias Visuais/fisiologia , Vias Visuais/diagnóstico por imagem , Percepção Visual/fisiologiaRESUMO
BACKGROUND: Flight accidents caused by spatial disorientation (SD) greatly affect flight safety. OBJECTIVE: Few studies have been devoted to the evaluation of SD. METHODS: 10 pilots and 10 non-pilots were recruited for the experimental induction of SD. Videos for giving optical flow stimuli were played at two different flow speeds to induce SD. Subjective judgment and center of foot pressure (CoP) data were collected from the tests. The data were combined to determine the occurrence of SD and analyze the SD types. RESULTS: The number of self-reported SD events was slightly smaller in the pilots than in the non-pilots. The average upper bound of the confidence interval for the standard deviation of CoP was 0.32 ± 0.09 cm and 0.38 ± 0.12 cm in the pilots and non-pilots, respectively. This indicator was significantly lower in the pilots than in the non-pilots (P= 0.03). The success rate of the experimental induction of unrecognized SD was 26.7% and 45.0% in the pilots and non-pilots, respectively. CONCLUSION: The method offered a new to analyze unrecognized SD. We could determine the occurrence unrecognized SD. This is an essential means of reducing flight accidents caused by unrecognized SD.
Assuntos
Confusão , Fluxo Óptico , Humanos , Masculino , Adulto , Fluxo Óptico/fisiologia , Pilotos , FemininoRESUMO
In mice, retinal direction selectivity is organized in a map that aligns to the body and gravitational axes of optic flow, and little is known about how this map develops. We find direction selectivity maps are largely present at eye opening and develop normally in the absence of visual experience. Remarkably, in mice lacking the beta2 subunit of neuronal nicotinic acetylcholine receptors (ß2-nAChR-KO), which exhibit drastically reduced cholinergic retinal waves in the first postnatal week, selectivity to horizontal motion is absent while selectivity to vertical motion remains. We tested several possible mechanisms that could explain the loss of horizontal direction selectivity in ß2-nAChR-KO mice (wave propagation bias, FRMD7 expression, starburst amacrine cell morphology), but all were found to be intact when compared with WT mice. This work establishes a role for retinal waves in the development of asymmetric circuitry that mediates retinal direction selectivity via an unknown mechanism.
Assuntos
Percepção de Movimento/fisiologia , Retina/metabolismo , Potenciais de Ação/fisiologia , Animais , Animais Recém-Nascidos , Dendritos/metabolismo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL/embriologia , Movimento (Física) , Fluxo Óptico/fisiologia , Receptores Nicotínicos/genética , Receptores Nicotínicos/metabolismo , Retina/embriologia , Células Ganglionares da Retina/metabolismo , Transmissão Sináptica/fisiologia , Acuidade Visual/genética , Vias Visuais/fisiologiaRESUMO
Optokinetic responses function to maintain retinal image stabilization by minimizing optic flow that occurs during self-motion. The hovering ability of hummingbirds is an extreme example of this behavior. Optokinetic responses are mediated by direction-selective neurons with large receptive fields in the accessory optic system (AOS) and pretectum. Recent studies in hummingbirds showed that, compared with other bird species, 1) the pretectal nucleus lentiformis mesencephali (LM) is hypertrophied, 2) LM has a unique distribution of direction preferences, and 3) LM neurons are more tightly tuned to stimulus velocity. In this study, we sought to determine if there are concomitant changes in the nucleus of the basal optic root (nBOR) of the AOS. We recorded the visual response properties of nBOR neurons to large-field-drifting random dot patterns and sine-wave gratings in Anna's hummingbirds and zebra finches and compared these with archival data from pigeons. We found no differences with respect to the distribution of direction preferences: Neurons responsive to upward, downward, and nasal-to-temporal motion were equally represented in all three species, and neurons responsive to temporal-to-nasal motion were rare or absent (<5%). Compared with zebra finches and pigeons, however, hummingbird nBOR neurons were more tightly tuned to stimulus velocity of random dot stimuli. Moreover, in response to drifting gratings, hummingbird nBOR neurons are more tightly tuned in the spatiotemporal domain. These results, in combination with specialization in LM, support a hypothesis that hummingbirds have evolved to be "optic flow specialists" to cope with the optomotor demands of sustained hovering flight.NEW & NOTEWORTHY Hummingbirds have specialized response properties to optic flow in the pretectal nucleus lentiformis mesencephali (LM). The LM works with the nucleus of the basal optic root (nBOR) of the accessory optic system (AOS) to process global visual motion, but whether the neural response specializations observed in the LM extend to the nBOR is unknown. Hummingbird nBOR neurons are more tightly tuned to visual stimulus velocity, and in the spatiotemporal domain, compared with two nonhovering species.
Assuntos
Aves/fisiologia , Mesencéfalo/fisiologia , Percepção de Movimento/fisiologia , Neurônios/fisiologia , Fluxo Óptico/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Animais , Comportamento Animal/fisiologia , Columbidae/fisiologia , Tentilhões/fisiologia , Técnicas de Patch-Clamp , Área Pré-Tectal/fisiologia , Especificidade da EspécieRESUMO
Precise heading perception requires integration of optic flow and vestibular cues, yet the two cues often carry distinct temporal dynamics that may confound cue integration benefit. Here, we varied temporal offset between the two sensory inputs while macaques discriminated headings around straight ahead. We find the best heading performance does not occur under natural condition of synchronous inputs with zero offset but rather when visual stimuli are artificially adjusted to lead vestibular by a few hundreds of milliseconds. This amount exactly matches the lag between the vestibular acceleration and visual speed signals as measured from single-unit-activity in frontal and posterior parietal cortices. Manually aligning cues in these areas best facilitates integration with some nonlinear gain modulation effects. These findings are consistent with predictions from a model by which the brain integrates optic flow speed with a faster vestibular acceleration signal for sensing instantaneous heading direction during self-motion in the environment.
Assuntos
Percepção de Movimento/fisiologia , Fluxo Óptico/fisiologia , Equilíbrio Postural/fisiologia , Animais , Encéfalo/fisiologia , Sinais (Psicologia) , Orelha Interna/fisiologia , Macaca mulatta , Masculino , Lobo Parietal/fisiologia , Estimulação Luminosa , Vestíbulo do Labirinto/fisiologia , Percepção Visual/fisiologiaRESUMO
For the human observer, it can be difficult to follow the motion of small objects, especially when they move against background clutter. In contrast, insects efficiently do this, as evidenced by their ability to capture prey, pursue conspecifics, or defend territories, even in highly textured surrounds. We here recorded from target selective descending neurons (TSDNs), which likely subserve these impressive behaviors. To simulate the type of optic flow that would be generated by the pursuer's own movements through the world, we used the motion of a perspective corrected sparse dot field. We show that hoverfly TSDN responses to target motion are suppressed when such optic flow moves syn-directional to the target. Indeed, neural responses are strongly suppressed when targets move over either translational sideslip or rotational yaw. More strikingly, we show that TSDNs are facilitated by optic flow moving counterdirectional to the target, if the target moves horizontally. Furthermore, we show that a small, frontal spatial window of optic flow is enough to fully facilitate or suppress TSDN responses to target motion. We argue that such TSDN response facilitation could be beneficial in modulating corrective turns during target pursuit.
Assuntos
Dípteros/fisiologia , Neurônios/fisiologia , Fluxo Óptico/fisiologia , Animais , Dípteros/genética , Insetos/fisiologia , Percepção de Movimento/fisiologia , Visão Ocular/fisiologia , Percepção Visual/fisiologiaRESUMO
Animals' self-motion generates a drifting movement of the visual scene in the entire field of view called optic flow. Animals use the sensation of optic flow to estimate their own movements and accordingly adjust their body posture and position and stabilize the direction of gaze. In zebrafish and other vertebrates, optic flow typically drives the optokinetic response (OKR) and optomotor response (OMR). Recent functional imaging studies in larval zebrafish have identified the pretectum as a primary center for optic flow processing. In contrast to the view that the pretectum acts as a relay station of direction-selective retinal inputs, pretectal neurons respond to much more complex visual features relevant to behavior, such as spatially and temporally integrated optic flow information. Furthermore, optic flow signals, as well as motor signals, are represented in the cerebellum in a region-specific manner. Here we review recent findings on the circuit organization that underlies the optic flow processing driving OKR and OMR.
Assuntos
Cerebelo/fisiologia , Rede Nervosa/fisiologia , Fluxo Óptico/fisiologia , Vias Visuais/fisiologia , Animais , Movimentos Oculares/fisiologia , Humanos , Estimulação Luminosa/métodos , Peixe-ZebraRESUMO
Successful interaction with the environment requires the dissociation of self-induced from externally induced sensory stimulation. Temporal proximity of action and effect is hereby often used as an indicator of whether an observed event should be interpreted as a result of own actions or not. We tested how the delay between an action (press of a touch bar) and an effect (onset of simulated self-motion) influences the processing of visually simulated self-motion in the ventral intraparietal area (VIP) of macaque monkeys. We found that a delay between the action and the start of the self-motion stimulus led to a rise of activity above the baseline activity before motion onset in a subpopulation of 21% of the investigated neurons. In the responses to the stimulus, we found a significantly lower sustained activity when the press of a touch bar and the motion onset were contiguous compared to the condition when the motion onset was delayed. We speculate that this weak inhibitory effect might be part of a mechanism that sharpens the tuning of VIP neurons during self-induced motion and thus has the potential to increase the precision of heading information that is required to adjust the orientation of self-motion in everyday navigational tasks.NEW & NOTEWORTHY Neurons in macaque ventral intraparietal area (VIP) are responding to sensory stimulation related to self-motion, e.g. visual optic flow. Here, we found that self-motion induced activation depends on the sense of agency, i.e., it differed when optic flow was perceived as self- or externally induced. This demonstrates that area VIP is well suited for study of the interplay between active behavior and sensory processing during self-motion.
Assuntos
Cinestesia/fisiologia , Percepção de Movimento/fisiologia , Atividade Motora/fisiologia , Fluxo Óptico/fisiologia , Lobo Parietal/fisiologia , Animais , Eletrocorticografia , Macaca mulatta , Masculino , Neurônios/fisiologiaRESUMO
Aging is associated with a gradual decline in the sensory systems and noisier sensory information. Some research has found that older adults compensate for this with enhanced multisensory integration. However, less is known about how aging influences visual-vestibular integration, an ability that underlies self-motion perception. We examined how visual-vestibular integration changes in participants from across the lifespan (18-79 years old) with a simple reaction time task. Participants were instructed to respond to visual (optic flow) and vestibular (inertial motion) acceleration cues, presented either alone or at a stimulus onset asynchrony. We measured reaction times and computed the violation area relative to the race model inequality as a measure of visual-vestibular integration. Across all ages, the greatest visual-vestibular integration occurred when the vestibular cue was presented first. Age was associated with longer reaction times and a significantly lower detection rate in the vestibular-only condition, a finding that is consistent with an age-related increase in vestibular noise. Although the relationship between age and visual-vestibular integration was positive, the effect size was very small and did not reach statistical significance. Our results suggest that although age is associated with a significant increase in vestibular perceptual threshold, the relative amount of visual-vestibular integration remains largely intact.
Assuntos
Envelhecimento Saudável/fisiologia , Envelhecimento Saudável/psicologia , Percepção de Movimento , Fluxo Óptico/fisiologia , Vestíbulo do Labirinto/patologia , Aceleração , Adolescente , Adulto , Idoso , Sinais (Psicologia) , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa , Desempenho Psicomotor , Tempo de Reação , Adulto JovemRESUMO
When two different images are presented separately to each eye, one experiences smooth transitions between them-a phenomenon called binocular rivalry. Previous studies have shown that exposure to signals from other senses can enhance the access of stimulation-congruent images to conscious perception. However, despite our ability to infer perceptual consequences from bodily movements, evidence that action can have an analogous influence on visual awareness is scarce and mainly limited to hand movements. Here, we investigated whether one's direction of locomotion affects perceptual access to optic flow patterns during binocular rivalry. Participants walked forwards and backwards on a treadmill while viewing highly-realistic visualisations of self-motion in a virtual environment. We hypothesised that visualisations congruent with walking direction would predominate in visual awareness over incongruent ones, and that this effect would increase with the precision of one's active proprioception. These predictions were not confirmed: optic flow consistent with forward locomotion was prioritised in visual awareness independently of walking direction and proprioceptive abilities. Our findings suggest the limited role of kinaesthetic-proprioceptive information in disambiguating visually perceived direction of self-motion and indicate that vision might be tuned to the (expanding) optic flow patterns prevalent in everyday life.
Assuntos
Percepção de Movimento/fisiologia , Fluxo Óptico/fisiologia , Percepção Visual/fisiologia , Caminhada/fisiologia , Adolescente , Adulto , Estado de Consciência/fisiologia , Feminino , Humanos , Locomoção/fisiologia , Masculino , Estimulação Luminosa/métodos , Propriocepção/fisiologia , Adulto JovemRESUMO
Visual segregation of moving objects is a considerable computational challenge when the observer moves through space. Recent psychophysical studies suggest that directionally congruent, moving auditory cues can substantially improve parsing object motion in such settings, but the exact brain mechanisms and visual processing stages that mediate these effects are still incompletely known. Here, we utilized multivariate pattern analyses (MVPA) of MRI-informed magnetoencephalography (MEG) source estimates to examine how crossmodal auditory cues facilitate motion detection during the observer's self-motion. During MEG recordings, participants identified a target object that moved either forward or backward within a visual scene that included nine identically textured objects simulating forward observer translation. Auditory motion cues 1) improved the behavioral accuracy of target localization, 2) significantly modulated the MEG source activity in the areas V2 and human middle temporal complex (hMT+), and 3) increased the accuracy at which the target movement direction could be decoded from hMT+ activity using MVPA. The increase of decoding accuracy by auditory cues in hMT+ was significant also when superior temporal activations in or near auditory cortices were regressed out from the hMT+ source activity to control for source estimation biases caused by point spread. Taken together, these results suggest that parsing object motion from self-motion-induced optic flow in the human extrastriate visual cortex can be facilitated by crossmodal influences from auditory system.
Assuntos
Percepção Auditiva/fisiologia , Percepção de Movimento/fisiologia , Córtex Visual/fisiologia , Adulto , Córtex Auditivo/fisiologia , Sinais (Psicologia) , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Magnetoencefalografia/métodos , Masculino , Movimento (Física) , Movimento/fisiologia , Fluxo Óptico/fisiologia , Estimulação Luminosa/métodos , Projetos Piloto , Percepção Visual/fisiologia , Adulto JovemRESUMO
Many animals use visual cues to navigate their environment. To encode the large input ranges of natural signals optimally, their sensory systems have adapted to the stimulus statistics experienced in their natural habitats1. A striking example, shared across animal phyla, is the retinal tuning to the relative abundance of blue light from the sky, and green light from the ground, evident in the frequency of each photoreceptor type in the two retinal hemispheres2. By adhering only to specific regions of the visual field that contain the relevant information, as for the high-acuity dorsal regions in the eyes of male flies chasing females3, the neural investment can be further reduced. Regionalisation can even lead to activation of the appropriate visual pathway by target location, rather than by stimulus features. This has been shown in fruit flies, which increase their landing attempts when an expanding disc is presented in their frontal visual field, while lateral presentation increases obstacle avoidance responses4. We here report a similar switch in behavioural responses for extended visual scenes. Using a free-flight paradigm, we show that the hummingbird hawkmoth (Macroglossum stellatarum) responds with flight-control adjustments to translational optic-flow cues exclusively in their ventral and lateral visual fields, while identical stimuli presented dorsally elicit a novel directional flight response. This response split is predicted by our quantitative imaging data from natural visual scenes in a variety of habitats, which demonstrate higher magnitudes of translational optic flow in the ventral hemisphere, and the opposite distribution for contrast edges containing directional information.
Assuntos
Voo Animal/fisiologia , Manduca/fisiologia , Fluxo Óptico/fisiologia , Campos Visuais/fisiologia , Animais , Feminino , MasculinoRESUMO
When we move through our environment, objects in the visual scene create optic flow patterns on the retina. Even though optic flow is ubiquitous in everyday life, it is not well understood how our eyes naturally respond to it. In small groups of human and non-human primates, optic flow triggers intuitive, uninstructed eye movements to the focus of expansion of the pattern (Knöll, Pillow, & Huk, 2018). Here, we investigate whether such intuitive oculomotor responses to optic flow are generalizable to a larger group of human observers and how eye movements are affected by motion signal strength and task instructions. Observers (N = 43) viewed expanding or contracting optic flow constructed by a cloud of moving dots radiating from or converging toward a focus of expansion that could randomly shift. Results show that 84% of observers tracked the focus of expansion with their eyes without being explicitly instructed to track. Intuitive tracking was tuned to motion signal strength: Saccades landed closer to the focus of expansion, and smooth tracking was more accurate when dot contrast, motion coherence, and translational speed were high. Under explicit tracking instruction, the eyes aligned with the focus of expansion more closely than without instruction. Our results highlight the sensitivity of intuitive eye movements as indicators of visual motion processing in dynamic contexts.
Assuntos
Movimentos Oculares/fisiologia , Fluxo Óptico/fisiologia , Adulto , Humanos , Masculino , Percepção de Movimento/fisiologia , Estimulação Luminosa , Retina/fisiologia , Percepção Visual , Adulto JovemRESUMO
Just one superorder of insects is known to possess a neuronal network that mediates extremely rapid reactions in flight in response to changes in optic flow. Research on the identity and functional organization of this network has over the course of almost half a century focused exclusively on the order Diptera, a member of the approximately 300-million-year-old clade Holometabola defined by its mode of development. However, it has been broadly claimed that the pivotal neuropil containing the network, the lobula plate, originated in the Cambrian before the divergence of Hexapoda and Crustacea from a mandibulate ancestor. This essay defines the traits that designate the lobula plate and argues against a homologue in Crustacea. It proposes that the origin of the lobula plate is relatively recent and may relate to the origin of flight.
Assuntos
Crustáceos , Fluxo Óptico , Animais , Crustáceos/anatomia & histologia , Voo Animal/fisiologia , Insetos/anatomia & histologia , Neurônios , Neurópilo , Fluxo Óptico/fisiologiaRESUMO
During self-motion, an independently moving object generates retinal motion that is the vector sum of its world-relative motion and the optic flow caused by the observer's self-motion. A hypothesized mechanism for the computation of an object's world-relative motion is flow parsing, in which the optic flow field due to self-motion is globally subtracted from the retinal flow field. This subtraction generates a bias in perceived object direction (in retinal coordinates) away from the optic flow vector at the object's location. Despite psychophysical evidence for flow parsing in humans, the neural mechanisms underlying the process are unknown. To build the framework for investigation of the neural basis of flow parsing, we trained macaque monkeys to discriminate the direction of a moving object in the presence of optic flow simulating self-motion. Like humans, monkeys showed biases in object direction perception consistent with subtraction of background optic flow attributable to self-motion. The size of perceptual biases generally depended on the magnitude of the expected optic flow vector at the location of the object, which was contingent on object position and self-motion velocity. There was a modest effect of an object's depth on flow-parsing biases, which reached significance in only one of two subjects. Adding vestibular self-motion signals to optic flow facilitated flow parsing, increasing biases in direction perception. Our findings indicate that monkeys exhibit perceptual hallmarks of flow parsing, setting the stage for the examination of the neural mechanisms underlying this phenomenon.
Assuntos
Percepção de Movimento , Fluxo Óptico/fisiologia , Animais , Haplorrinos , Humanos , Macaca mulatta , Masculino , Retina/fisiologiaRESUMO
Older adults have difficulty adapting to new visual information, posing a challenge to maintain balance during walking. Virtual reality can be used to study gait adaptability in response to discordant sensorimotor stimulations. This study aimed to investigate age-related modifications and propensity for visuomotor adaptations due to continuous visual perturbations during overground walking in a virtual reality headset. Twenty old and twelve young subjects walked on an instrumented walkway in real and virtual environments while reacting to antero-posterior and medio-lateral oscillations of the visual field. Mean and variability of spatiotemporal gait parameters were calculated during the first and fifth minutes of walking. A 3-way mixed-design ANOVA was performed to determine the main and interaction effects of group, condition and time. Both groups modified gait similarly, but older adults walked with shorter and slower strides and did not reduce stride velocity or increase stride width variability during medio-lateral perturbations. This may be related to a more conservative and anticipatory strategy as well as a reduced perception of the optic flow. Over time, participants adapted similarly to the perturbations but only younger participants reduced their stride velocity variability. Results provide novel evidence of age- and context-dependent visuomotor adaptations in response to visual perturbations during overground walking and may help to establish new methods for early identification and remediation of gait deficits.
Assuntos
Adaptação Fisiológica/fisiologia , Marcha/fisiologia , Campos Visuais/fisiologia , Caminhada/fisiologia , Adulto , Idoso , Teste de Esforço/métodos , Feminino , Humanos , Masculino , Fluxo Óptico/fisiologia , Equilíbrio Postural/fisiologia , Realidade Virtual , Adulto JovemRESUMO
Moving around safely relies critically on our ability to detect object movement. This is made difficult because retinal motion can arise from object movement or our own movement. Here we investigate ability to detect scene-relative object movement using a neural mechanism called optic flow parsing. This mechanism acts to subtract retinal motion caused by self-movement. Because older observers exhibit marked changes in visual motion processing, we consider performance across a broad age range (N = 30, range: 20-76 years). In Experiment 1 we measured thresholds for reliably discriminating the scene-relative movement direction of a probe presented among three-dimensional objects moving onscreen to simulate observer movement. Performance in this task did not correlate with age, suggesting that ability to detect scene-relative object movement from retinal information is preserved in ageing. In Experiment 2 we investigated changes in the underlying optic flow parsing mechanism that supports this ability, using a well-established task that measures the magnitude of globally subtracted optic flow. We found strong evidence for a positive correlation between age and global flow subtraction. These data suggest that the ability to identify object movement during self-movement from visual information is preserved in ageing, but that there are changes in the flow parsing mechanism that underpins this ability. We suggest that these changes reflect compensatory processing required to counteract other impairments in the ageing visual system.
Assuntos
Envelhecimento/fisiologia , Percepção de Movimento/fisiologia , Fluxo Óptico/fisiologia , Retina/fisiologia , Adulto , Idoso , Feminino , Humanos , Longevidade , Masculino , Pessoa de Meia-Idade , Estimulação Luminosa/métodos , Adulto JovemRESUMO
Heading estimation from optic flow is crucial for safe locomotion but becomes inaccurate if independent object motion is present. In ecological settings, such motion typically involves other animals or humans walking across the scene. An independently walking person presents a local disturbance of the flow field, which moves across the flow field as the walker traverses the scene. Is the bias in heading estimation produced by the local disturbance of the flow field or by the movement of the walker through the scene? We present a novel flow field stimulus in which the local flow disturbance and the movement of the walker can be pitted against each other. Each frame of this stimulus consists of a structureless random dot distribution. Across frames, the body shape of a walker is molded by presenting different flow field dynamics within and outside the body shape. In different experimental conditions, the flow within the body shape can be congruent with the walker's movement, incongruent with it, or congruent with the background flow. We show that heading inaccuracy results from the local flow disturbance rather than the movement through the scene. Moreover, we show that the local disturbances of the optic flow can be used to segment the walker and support biological motion perception to some degree. The dichotomous result that the walker can be segmented from the scene but that heading perception is nonetheless influenced by the flow produced by the walker confirms separate visual pathways for heading estimation, object segmentation, and biological motion perception.
Assuntos
Percepção de Movimento/fisiologia , Movimento/fisiologia , Fluxo Óptico/fisiologia , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Masculino , Caminhada , Adulto JovemRESUMO
Neuroimaging studies have revealed two separate classes of category-selective regions specialized in optic flow (egomotion-compatible) processing and in scene/place perception. Despite the importance of both optic flow and scene/place recognition to estimate changes in position and orientation within the environment during self-motion, the possible functional link between egomotion- and scene-selective regions has not yet been established. Here we reanalyzed functional magnetic resonance images from a large sample of participants performing two well-known "localizer" fMRI experiments, consisting in passive viewing of navigationally relevant stimuli such as buildings and places (scene/place stimulus) and coherently moving fields of dots simulating the visual stimulation during self-motion (flow fields). After interrogating the egomotion-selective areas with respect to the scene/place stimulus and the scene-selective areas with respect to flow fields, we found that the egomotion-selective areas V6+ and pIPS/V3A responded bilaterally more to scenes/places compared to faces, and all the scene-selective areas (parahippocampal place area or PPA, retrosplenial complex or RSC, and occipital place area or OPA) responded more to egomotion-compatible optic flow compared to random motion. The conjunction analysis between scene/place and flow field stimuli revealed that the most important focus of common activation was found in the dorsolateral parieto-occipital cortex, spanning the scene-selective OPA and the egomotion-selective pIPS/V3A. Individual inspection of the relative locations of these two regions revealed a partial overlap and a similar response profile to an independent low-level visual motion stimulus, suggesting that OPA and pIPS/V3A may be part of a unique motion-selective complex specialized in encoding both egomotion- and scene-relevant information, likely for the control of navigation in a structured environment.