Title : Design of a chip mimicking binocular rivalry-A perceptual cognitive function
Abstract:
The human brain is able to adapt to new situations and learn new things. The purpose of the work is to investigate human brain adaptability and learning tendencies. The ability of the brain to learn, program, and adapt has been replicated using CMOS-based circuitry, Neuromorphic Circuits (NCs). NCs can be used to create chips that can help people heal (adaptive technology) from severe brain injuries, improve their memory, learn more effectively, and improve various other cognitive capacities. Our eyes construct a single coherent vision from two slightly different images that are supplied to both of them during daily visual perception (Harwerth & Schor, 2011)[1]. Binocular rivalry (BR) happens when two mismatched pictures are simultaneously given to both eyes. When mismatched images are shown to each eye, BR is a perceptual cognitive function in which perception changes [2, 3, 4]. According to the illustration in figure 1, there will be alternate periods of dominance (supremacy) when one eye is presented with a flat green grating and the other eye is presented with an orthogonal red grating. In this case one of the gratings will be visible while the other is either fully invisible or only partially visible (suppression).
The alternating periods of perceptual dominance that take place during competition have been modelled computationally in a number of ways [5, 6, 7, 8, 9]. Due to mutual inhibition between the neurons encoding the two perceptions in these models, the other perception is repressed when one is dominant. The second law of Levelt's (Levelt, 1965), which states that if the contrast of one eye is reduced, it raises the dominant level in other eyes while dominating interval in the eye having weak stimuli relatively remains unchanged, explains another important aspect of the rivalry[10]. Neural adaptation is the third characteristic of BR. According to Clifford et al. (2007), neural adaptation is a common feature of the visual system that enables our visual system to suppress the signal from one eye in order to resolve this conflict and produce a cohesive conscious perception [11]. It is employed as a potent feature for analysing the relative contributions of low-level, eye-based factors and high-level, feature-based elements in BR (e.g., Blake et al., 2006; van Boxtel et al., 2008)[12, 13]. Binocular rivalry is a heritable perceptual cognitive function that is impaired in patients with schizophrenia (SZ). Binocular rivalry is also slower in the autistic brain [14]. This phenomenon, known as binocular rivalry, has been used as a powerful tool to investigate mechanisms of visual awareness. In the work a CMOS based circuit have been designed using 45nm CMOS process which can emulate all the features of Binocular rivalry. It shows neural adaption; that is winning cell looses after some time (0.2ms) and allows other cell to win. This cognitive ability of visual brain can be controlled. User to user competition can be somewhat curbed by meditation and other factors like drugs etc. which increases concentration. Meditation-specific ERP results as evidence that extensive meditation practice provides control of frontal brain areas over early sensory processing steps. This may allow mediators to overcome phylogenetically evolved perceptual and attention processing automatisms [15]. In future research work the circuits can be modified to provide a concentration level factor (some threshold voltage) that can control self-adaptation in the suggested architecture. The hardware/chip if fabricated it could show; superimposition of images when same image shown to two eyes, suppression and dominance when different images are shown to eyes; neural adaption where self-adaption of images takes place and can finally regulate this self-adaptation/switching of images after reaching a certain amount of learning/ concentration(threshold voltage). The work is to attempt and to understand through simulations Binocular Rivalry a perceptual cognitive behaviour of visual brain.
