Evidence for the Persistence of Visual Guidance Information - Lab Report Example

Lab Report Week 9 Name: Lecturer: Course name: Course code: Date: Introduction Humans are able to orient and move through an environment they have recently seen even without simultaneous visual information to aid their movements. Visuo-spatial memory engages in reinforcing this skill. The phenomenological experience normally seen when one moves around the environment, is that, updates of information from all the senses coherently configures. According to spatial cues save, 2003) and humans (e.g., Pasqualotto, Finucane, & Newell, 2005; Simons & Wang, 1998), there little knowledge on how spatial updating in the entire human senses affects by the blinding process. Visuo-spatial ability influences ones brain processing speed, its dominant executive function and associated with growing intra-individual gait deviations in twin support phase, a determination of balance during gait. To start with, time needed to make a first lateral movement is essentially the first and effective measure of gait initiation, provided its reliable associations with falls-risk and cognition surrogates. It also happens through responsiveness to cognitive interference from dual-tasking like clapping and walking while blind-folded. The surrogate measure of falls-risk influences executive function, processing speed and visuospatial ability. It has no direct connection to cognitive function, the memory. In addition, poor visuospatial abilities occasionally predict the risk of unbalancing and falls. The connection between all cognitive functions and the uncertainty of falling or reducing walking speed are magnifies in situations of poor sensor motor function, lowered gait speed or ambulatory activity. Various studies have yielded significant inferences on the relationships between cognitive functions in the brain, gait and the reduction in walking speed due to fear of falling. In tandem with prior studies, brain processing speed may either be engaged in gait control or have a common neural substrate. It is possible that visuospatial ability contributes a lot in the cortical function through reflection of a person’s sense of space and position. This associates with gait. Brain memory has least influence on gait. The objectives of this study were to determine the anthropometric difference that may influence the walking performance (e.g., wide vs. narrow hip). It also established the cognitive method such as counting the steps used to reach the target. Others were to assess past experience (e.g., gymnastics) and how they might influence the performance of walking straight. Finally, it evaluates the cognitive effort might be reduced in 4s blind time (BT) and enhanced in 64s BT which brought about the reverse pattern in walking performance. Methods The experiment used equipments such as a tape, blindfold, and measuring tape. The students were organized into groups of three. In each group, one was a participant; while the other two were experimenters (spotter and recorder). Two strips of tape were applied to a floor with a separation of 35cm to define a straight 6-m-Iong path. The goal for the participant was to walk blindfolded at a normal pace as far as possible within the path. The participant was assured that he/she would be stopped by an experimenter (spotter) before contacting a wall. Prior to beginning the actual experiment, the participant was walked the path with normal visual feedback, and then while wearing a blindfold. At the start of each trial, the participant positioned his/her feet behind a starting line, and square up toward the path. After viewing the path for 10 seconds, the participant was then blindfolded. Two trials at each of five Blind Times (4, 8, 16, 32, and 64) will be tested in a random order. In both tasks, the subject was aware of the range of BTs, but not the BT of any given trial. One trial involved normal blind walking and other was added continuous clapping (dual tasking) while walking blind. Following the blind time (BT), the participant was instructed to "begin walking (with or without clapping)." Two experimenters followed the subject down the path. One experimenter measured the distance that the participant walked within the path-the distance from the starting line to the point at which any part of feet landed outside the path. The second experimenter played the role of a "spotter" and stopped the subject before contact was made with a wall. Results The results of walking performance to a target which was 5 m away from the starting position (n=13). The pathway was 35 cm wide. The results were illustrated in the figure below. In the first four seconds of blind time, the dual task with clapping and walking could take one further than just walking. The performance of the participant doing the dual task was gradually reducing while that of the participant doing the single task rose steadily within the first 8 seconds and dropped considerably within the next 24 seconds. Thereafter, the performance of the single task participant gained gradually. The dual task participant experienced reduced walking performance especially in the last 48 seconds. Figure 1: Walking performance against blind time Discussion From the above results it can be deduced that walking performance reduces when one engages the memory which already is in active mode. The brain uses the stimuli from the previous sight to follow the path during blindness. The processing speed of the brain is considerably reduced when the psychomotor is disturbed in which case the activity of walking is substantially reduced. The possible explanation to these phenomena is the activity of the spinal central pattern generator (CPG). Earlier experiment done by Tyrrell and his colleagues showed that there was reduced performance when blindness was increased. It invokes tonic activation from the brain to generate locomotive pattern in humans and other animals. The entire signals that originate from the brain are integrated by activating various parts of the brain such as mesencephalic locomotors region (MLR), sub thalamic locomotors region and die cephalic locomotors region. These are the regions that send signal to the spinal CPG to prompt, control and stop the movement. The concentration is on the MLR located next to inferior colliculus. When this part is stimulated, the medial reticular formation is activated. Thus, the reticulospinal tract tot the spinal CPGs is activated. Any person with damaged inferior colliculus portrays symptoms called astasia. This is the inability to walk. Research shows that MLR gets inputs that are exciting from hypothalamus and inhibitory input from basal ganglia. The same organization of locomotors control is found in all vertebrate animals – stimulation of MLR in a fish will cause it to swim, while a bird will begin to walk or fly. At relatively slow level of stimulation, it will walk, and with the increase in strength of stimulation, it will increase the speed of walk. If the strength is increased further, the animal will break into a trot and ultimately to run. This demonstrates that MLR not only initiates or terminates the gait but can control the pattern and speed of locomotion. Other roles of descending signals on CPGs are as follows: adapting locomotion to the requirements of the task and environment, coordinating locomotion with other voluntary actions, and maintaining postural equilibrium during locomotion. Especially adapting to external requirements is typically achieved with vision. Different magnitude of GRF will be generated with different size of base of support (BoS). For example, a certain stance width will facilitate one person to jump higher. He suggested that overall optimal muscle lengths from whole joints from particular posture will be the modulating factor that links greater GRF with a particular size of BoS. Friction and GRF due to gravity are two main forces acting on the body in locomotion. On the slipper surface, people tend to decrease the step length, cycle duration, and horizontal shear forces (Figure 9.1). The head orientation tends to be stabilized in space. But arm movements, trunk rotations, and lateral trunk inclinations are considerably increased. Foot motion and gait pattern tends to resemble those of a digitigrades gait (Cappellini, Ivanenko, Dominici, Poppele, & Lacquaniti). Animals can adapt to different task and environment – different surface, slopes, obstacles, or loads to carry – while walking or running. These adaptations require constant flux of afferent information to spinal cord and brain. When afferent inputs are not available, a spinal animal only produces a rather stereotyped pattern of muscle activation for locomotion. On the other hand, decelerate cats with intact some sensation can adapt to increase or decrease in speed when on the treadmill. This adaptation can be explained by the afferent inputs controlling the timing of swing to stance phase through spinal CPGs. During stance, the load sensing receptors such as Golgi tendon organs (GTOs) in the limb is active. As the leg moves back and hip extension increases, the stretch sensing receptors (muscle spindle) in the flexors is active. Hence, these changes in afferent signals can inform CPGs of the stance duration and transition between stance-to-swing phases. There is a proposal of the GTO signals to excite the extensor rhythm generator. A substantive evidence of this proposal originates from analysis and studies of GTO afferents artificial stimulation that can extend period of instance phase when there is persistence in the stimulus. Ideally, slow down of gait in the decelerate cat with intact afferents is stimulated by GTO. When the body is adapting to increase speed, the muscle uses input from hip flexor to notify. The termination of the stand phase CPG and enables stance-to-swing swing transition. If the treadmill increases its speed, the flexor stretch quickens and the apparent notify the CPGs to translate the pattern to the swing of the leg. In such a case, either I or II afferents suppress the extensors and excite the flexor rhythm. The sometosensation and CPG that discussed were in relation to decerebrated animals. The intact animals’ afferent inputs emanating from somatosensation are relatively weaker. This portrays small alteration of how the phase modulates with the extensor loading. There are a number of signals that contributes to stance timing to swing transition and stance duration control. And therefore it is exceptionally difficult to detect the specific effects of somatosensation in a control study. The result showed that the limb loading in human infant that receive less descending signal input are significantly less. The stance duration and transition is influenced by the hip position just like decerebrated cats and spinal. Stumbling corrective reaction the reflexes correct one from falling when tripping or stumbling. The responses called stumbling corrective reaction. Usually in a trip, the contact with an object is likely to occur on the top of the paw or on the fount of the lower leg for a cat. Such stimulus stimulates coetaneous receptors and elicits a flexor withdrawal type response that lifts the foot up and over the obstacle. Even a light touch is enough to elicit the response from a cat. The response can be evoked during the swing phase, but if the same stimulus is delivered to the same location of the foot during the stance phase, no flexor withdrawal response is elicited. Instead, the stimulus tends to enhance extensor activity in the stimulated leg which is an opposite response. This is an example of reflex reversal where the same stimulus elicits one response in one context but opposite response in different context. As this reflex reversal is dependent on the phase of locomotion, it is called phase-dependent reflex reversal. If contact occurred early in the swing phase, a flexor withdrawal response was shown – participants lifted their foot up and over the obstacle. But when the contact occurred in the late swing phase, the foot would be put down rapidly on the ground to terminate the swing phase, and the foot would overcome the obstacle on the next stride. If the contact occurred in mid swing, flexor withdrawal response would occur often, but sometimes placing response was elicited (Schillings, Van Wezel, & Duysens, 1996). A more precise control of afferent input can be done by electrically stimulating the peripheral nerves. Non-noxious stimulus of the superficial personal nerve mimics the cetaceous contact of the top of the foot, which has been found to elicit responses similar to those from studies using real blocks (Zehr, Komiyama, & Stein, 1997). The phase dependent modulation of reflex can be explained in association with the CPG modules. During swing, the withdrawal reflex pathway involving coetaneous afferents from the top of the foot is activated and the effect of CPG module excitation by coetaneous afferent signals enhances the action as well. During stance, the reflex is not activated as there is no excitation from the extensor rhythm generator, and so afferent input cannot elicit withdrawal of the foot. References Tyrrell, R.A., Rudolph, K.K., Eggers, B.G., Leibowitz, H.W. (1993). Evidence for the persistence of visual guidance information. Perception & Psychophysics, 54, 431-438. Read More