Neural Latency, Critical Approach in Relation to Flash-Lag Effect - Essay Example

?Neural Latency, Critical Approach In Relation To Flash-Lag Effect By Neural Latency, Critical Approach In Relation To Flash-Lag Effect Introduction For most people it appears natural when they experience the visual environment as being spatially stable. Nonetheless, due to movements through the visual environment a sort of self-motion brings on an optic gush referred to as flash-lag effect. According to Nijhawan, a Flash-lag visual phenomenon is basically a visual illusion whereby a flash and the moving object appear in similar location, and as a result, perceived by the observer to be relocated from one another (Nijhawan,2002, p. 263).  In particular, when an object flickers briefly within a particular location, and at that instance another object in motion arrives in that similar location, then the observer perceives as being lagging at the back of the moving object. Thus, three explanations for this phenomenon have been presented and they are motion extrapolation effect, positional averaging, and the latency difference effect. However, when it comes to motor behaviors, humans just like all animals have to coordinate their neural actions across diverse regions in their motor structure. Normally, a flash of light generates neural activity within an observer brain under a delay of between 30 to 100 milliseconds, and attributed to the slow progression of visual transduction among the photoreceptors (Berry II, Brivanlou, Jordan, & Meister, 1999, p.334). This significant dispensation delays inside the motor system is compensated inside the internal replica of the motor structure. Thus, observers perceived the flash-lag phenomenon whereby the flashed item position lags behind the position of the time- shifting item along the characteristic dimension. Therefore, the aim of this paper is to elaborate on the neural latency critical model in relation to the flash-lag effect. Discussion The main issue is why should in motion visual items be processed speedier compared to flashes, since two forms of objects arouse comparable collection of neurons. Nijhawan & Kirschfeld in their assessment of neural delay compensation for time-shifting motor activities noted that flashed objects are only processed somewhat faster compared to moving objects (Nijhawan & Kirschfeld,2003, p. 752). Thus, in spite of the relative speed of proprioceptive signals, the motor-system compensation takes place only in reaction to the feedback arising from skin receptors. Accordingly, actions conducted only under feedback-control result in instability, and the forward model almost certainly compensate for holdups which would otherwise result in spatial localization faults arising from let say an observer moving hand. It is still very much unclear as to whether the differential latency theory has direct link to typical flash-lag effects (Wojtach, Sung, Truong, & Purves, 2008, p. 16341). When it comes to a steady space perception through self-motion Nijhawan notes that, an observer central nervous system needs to apply extra-retinal signals, in order to compensate for the retinal movement (Nijhawan,2002, p. 388). In such a state, the question arises as to how an observer brain merges visual signals arising from the surroundings, with the internal signals linked to self motion. Thus, when it comes to motor responses that are aimed at visual objects in motion, there occur delay difficulties inside the sensory pathways transporting critical position information. One of the explanations for the Flash-lag phenomenon is the motion-extrapolation theory for reimbursement of the 4, 5 and 6 sensory delays (Nijhawan & Kirschfeld,2003, p. 750). In this study done by Nijhawan & Kirschfeld, the observers perceived the flashed object in a co-localized manner with the object lagging behind the object in motion (Nijhawan & Kirschfeld, 2003, p.750). In that study the major features of neural delays in the nervous structure were important in the assessment of the flash-lag phenomenon. To begin with, the cumulative delays within neural signaling are momentous in situation whereby an observer is facing a time-shifting stimulus while generating a motor response within a sensory guidance. Therefore, a thriving motor behavior like those perceived by animals within a field under auditory 17, visual 15 and visual 16 facilitates the animal to get to the exact position within the appropriate time (Nijhawan & Kirschfeld,2003, p.751). In order to focus a flashed item, the observer brain needs to integrate the item retinal location using an extra retinal indicator in the eyes region of gaze. But, given that it is hard for the CNS to counterpart moving or flashed stimuli due to continuously shifting variables such as those of position or velocity signals, processing takes place at different delays. For that reason, a systematic partiality of the supposed location can reveal the limits of such a process (Alais & Burr, 2004, p. 256). The flash-lag effect reveals two key features. First of all, there is dissimilarity in terms of flash localization slip-ups and which are conditional on retinal position of the flash with regard to the direction of the motion (Nijhawan, 2002, p. 264). For instance, a flash existing ahead and at the rear of an observer course of gaze is mis-localized in different ways. Notably, the interception of moving items would be unfeasible when there is no compensation for dispensation delays within the sensory or motor pathways. Thus, the delays occurring within the sensory ends as a result of photo-transduction, retinal-processing or cortical processing, do possess some potential in resulting in mislocalization or lag inside the visual location of the moving item. Similarly, the proprioceptive information arising from the observer skin, muscles or joints are exposed to major delays, given that they are moving to the cortex concurrently with neural prompts of muscles following motor commands originating from the cortex (Arrighi, Alais, & Burr, 2005, p. 2920). This then presents a similar concern as noted by Nijhawan in the study Neural delays, visual motion and the flash-lag effect regarding spatial lag inside the sensed location of the in-motion outcome even as it is controlled by the CNS (Nijhawan, 2002, p.390). Therefore, even though compensation for visual or sensori-motor delays can happen in anyplace between the sensory input or else the motor output, the interceptive behaviors can eventually breakdown. As a result, the observer would be presented with a risk of severe injury when such delays are not compensated accordingly. Given the conception that visual cortex applies delayed visual information originating from the eye, in order to extrapolate the route of any moving item which is then perceived at its real position, Berry II, et tal (1999, p. 335) report that such expectation of an in-motion stimuli starts from the retina. Thus, in the experiment a moving rod elicited an in-motion wave of pointed activities in the populace of the observer retinal-ganglion cells. But instead of falling behind the visual image, the populace activities moved near the main perimeter of the in-motion rod (Fu, Shen, & Dan, 2001, p. 5). However, such a response is only observed over an extensive collection of speeds and it only appears to compensate for the visual-response latency. Furthermore, when it comes to attaining a perceived course which is curvilinear, the attention is projected to weaken the effect of anticipatory moving signals happening on the level of deviation through a number of mechanisms. An example is in visual or the hippocampal systems, whereby the bump motion is directly compelled by exterior inputs, and consequently, the misrepresentation of the bump becomes inevitable (Nijhawan, 2002, p. 390). Nevertheless, one has to remember that a moving item in most instances will travel in a level trajectory, such that one can extrapolate from the object previous positions and velocity. This then helps to attain an estimate of the object present location. The human brain applies such a mechanism, since the ganglion cells have no direction-selective partiality, even as the width somehow amplifies during latter stage of the reaction (Nijhawan,2002, p. 388). This in the end creates an outward impression of a splash. Nijhawan in the study The flash-lag phenomenon: object motion and eye movements, notes that the expectation of an in- motion object comes about due to the cells being to the fore of the rod begin to start firing early on even as they fire as stimulation mounts when the rod overruns the receptive field (Nijhawan,2002, p. 270). The motion-extrapolation model implies that compensation for spatial-lag within the observed position of any moving item is attained inside the 4, 5 or 6 visual structure (Berry II, Brivanlou, Jordan, & Meister, 1999, p. 336). On the other hand, visual compensation model is considered problematic since compensation particularly for sensory delays can be attained through the mechanisms in the motor-system. In particular, sensory and motor delays compensation take place inside motor pathways and that delays in the registration of any flash will never be compensated for. Nijhawan & Kirschfeld, observed that the internal forward theory and the motion extrapolation theory are equivalent systems which compensate respectively for the neural delays within the motor and visual structure (Nijhawan & Kirschfeld, 2003, p.751). In that study which was conducted under total darkness, the observer when redirecting the right hand while gripping a bar, the visual flash was presented within a variety of positions with respect to the bar. However, when the visual flash was brought into line with the bar, the observer perceived the bar as lagging behind the immediate felt location of the invisible bar. Hence, such results reveal that re-compensation for neural delays, under time-shifting motor behavior mirror the compensation in holdup for time-shifting visual stimulation. This observation can be explained by the occurrence of neural delays during transmission of sensed observer location of a moving hand, and which are compensated for inside the observer motor pathways. As a result, the observer rightly senses the present instantaneous location of the moving bar. Nevertheless, the discernment of the flash is overdue resulting in the perceived location of the flash, to fall behind the perceived position of the bar. Notably, in the background of the thriftiness, the resemblance of the existing flash lag to the typical visual flash lag implies a general existence of analogous systems that compensate for holdups in different sections of the observer nervous system (Nijhawan, 2002, p. 264). Internal forward models are mostly considered as the plausible mechanisms in which compensation of the neural delays take place in the motor structure. In particular, the forward model merges the efference commands with predictable sensory outcomes of movements. Even though substantiation for internal model is by and large strong, the empirical evidence sustaining the model is not evident, and even those studies that have examined forward model within the kinematics of the observer arm movements during dynamic fine-tuning of force of an object-sliding or visual-motor rod balancing, leave a question as to whether the nervous- system applies forward theory in compensating for the neural holdups (Berry II, Brivanlou, Jordan, & Meister, 1999, p. 337). However, both motion-extrapolation theory and visual flash-lag are similar to internal-forward theory during compensation for the neural delays. Notably, the standard flash-lag phenomenon seems to imply that the visual outcome is as a result of speedier processing of the motion relative to the flashed-stimuli. This then raises the question as to whether minor delays might be the cause of current flash-lags during diffusion of signals from the bar, in relation to the conveyance of signals prompted by the flash (Enns & Oriet, 2007, p. 222). Interestingly, the forward model of visual coordination is engaged in scenarios whereby the observer neither conducts nor plans to conduct any motor response. Hence, the flash-lag outcome is observed under stationary but time-varying stimuli, similar to stimulus patch turning out continuously darker and even brighter after a while (Baldo, Kihara, Namba, & Klein, 2002, p. 22). During a study done by Nijhawan & Kirschfeld, the time-varying spaces seems darker or in some instances brighter compared to flashed adjacent patches of similar brightness (2003, p.751). This is attributed to forward model being positioned within the ventral or striate cortex, and towards the infero-temporal cortex course for visual processing. Such an effect is linked to detection of perceptual characteristics, as the forward model is set off even when the observer is simply recognizing the shifting perceptual nature of the time-varying stimulus. As a result, this then generates a flash-lag phenomenon under non-motion characteristic dimensions. Similarly, the forward model situated inside the auditory system can explain the so called auditory flash-lags, since there seems to occur numerous forward models but within different levels of the nervous system (Nijhawan,2002, p.270). The integration time under visual probe or auditory motion scenario condition, generates a rather longer integration time, implying that it generates the greatest flash-lag effects. This has been explained by Nijhawan & Kirschfeld, as the effect of ventriloquism outcome, whereby there is visual confinement of auditory through visual stimuli and when in motion (Nijhawan & Kirschfeld, 2003, p.752). Nijhawan, in the study The flash-lag phenomenon: object motion and eye movements observed that a powerful flash-lag effect occurs when an observer easily pursues a point target that is in-motion, past a continuously observable stationary loop (Nijhawan,2002, p. 266). This is because the flashed disk seems to appear to incompletely fill the middle of the endlessly visible motionless ring, thus, generating a vivid but perceived empty space. This then leads to the question as to whether two stimuli when combined can generate a new stimulus within a flash-lag tow moving color stimuli. Notably, motion processing takes place inside the cortex instead of retina, and as such, the capability of motion cues to impact discernment of color is dependable on Young-Helmholtz-Maxwell model of a central blend of yellow (Nijhawan, 1997, p. 67). Nijhawan in the research paper Visual decomposition of color through motion extrapolation observed that, when there is presentation of light made up of red and green stimuli, an observer experienced an equal overlap of intensity balance from the two rods (Nijhawan, 1997, p.68). Thus, the observer perceives the overlapping area as being yellow in color at the retina. However, when the motion of the rods became visible, the observer noted the flashed line color falling back the two rods. This then implies that a system for the flash-lag outcome exist soon enough within the visual conduit, such that uncombined red color signals together with green color signals can still be salvaged. In order to perceive an even eye velocity following a flash, the total eye displacement, or the combination of even eye velocity, relied on the observer eye rapidity during the instance of the flash (Nijhawan, 2002, p. 270). For that reason, Nijhawan in the study neural delays, visual motion and the flash-lag effect observed that the elevated the eye velocity during the instance of the flash, the greater the whole even eye displacement (Nijhawan, 2002, p.388). During the flash-induced half sequence, the motion commencement takes place concurrently with the flash, and as a result, the flash-lag is observed with the end product being similar to an entire cycle display. On the whole, displays whereby an in-motion stimulus exist prior to and following a flash can be attained through varying both the speed and direction for the double half-cycles (Lim & Choe, 2008, p. 1683). Based on the above critical account, future studies should now focus on examining separate but present flash-lag effects conducted by predictable shifts in proprioceptive input and which comes about from either wrist or hand motions, but in contrast to efferent motor instructions occurring under wrist-joint rotation. Conclusion This per concludes that the flash-lag effect does seem not limited to objects in motion but also seems to occur during smooth eye trail movements in both head and entire body movements. In both situation, the retinal signals in the region of the motion are not present and in certain scenarios the flash-lag occurs in the absent of any motion. Thus, illusory motion discernment can bring on a perceptual preconceived notion of a flashed object. This should involve movement of observer hand using external appliances but in a passive manner, in an attempt to effectively eliminate motor command effects. What is unclear from the findings in these studies is whether there is a single mechanism which can entirely explain every recognized flash-lag effect. Secondly, it is also unclear whether two seemingly dissimilar mechanisms can be operationally distinct. A case in point is whether latency correction model or the latency-reduction models can occur simultaneously under similar timeframe after motion inception. Thus, answering such questions will determine whether flash lag effect models are distinct or not. List of References Alais, D., & Burr, D. (2004). The ventriloquist effect results from near optimalnear optimal bimodal integration. Current Biology , 14 (3), 257–262. Arrighi, R., Alais, D., & Burr, D. (2005). Neural latencies do not explain the auditory and audio-visual flash-lag effect. Vision Research , 45, 2917–2925. Baldo, M. V., Kihara, A. H., Namba, J., & Klein, S. (2002). Evidence for an attentional component of the perceptual misalignment between moving and flashing stimuli.-, 31(1),. Perception-London , 31 (1), 17-30. Berry II, M. J., Brivanlou, I. H., Jordan, T. A., & Meister, M. (1999). Anticipation of moving stimuli by the retina. Nature , 398, 334-338. Enns, J. T., & Oriet, C. (2007). Visual similarity in masking and priming: The critical role of task relevance. Advances in Cognitive Psychology , 3 (1), 211-226. Fu, Y. X., Shen, Y., & Dan, Y. (2001). Motion-induced perceptual extrapolation of blurred visual targets. The Journal of Neuroscience , 21, 1–5. Lim, H., & Choe, Y. (2008). Extrapolative Delay Compensation Through Facilitating Synapses and Its Relation to theFlash-lag Effect. Neural Transactions , 19 (10), 1678-1688. Nijhawan, R. (2002). Neural delays, visual motion and the flash-lag effect. Trends in Cognitive Sciences , 6 (9), 387-393. Nijhawan, R. (2002). The flash-lag phenomenon: object motion and eye movements. Perception , 30 (3), 263-282. Nijhawan, R. (1997). Visual decomposition of colour through motion extrapolation. Nature , 386, 66-69. Nijhawan, R., & Kirschfeld, K. (2003). Analogous Mechanisms Compensate for Neural Delays in the Sensory and the Motor Pathways: Evidence from Motor Flash-Lag. Curr Biol , 13 (9), 749-753. Wojtach, W. T., Sung, K., Truong, S., & Purves, D. (2008). An empirical explanation of the flash-lag effect. Proceedings of the National Academy of Sciences, 105, pp. 16338-16343. Read More