The cortical pathway responsible for motion processing is relatively well defined (see e.g. Britten, 2003 for review). However, an understanding of the precise mechanisms involved in encoding the speed of a moving image has proven evasive. A variety of models have been proposed, including labelled line, ratio and Bayesian models (e.g. Priebe & Lisberger, 2004; Smith & Edgar, 1994; Thompson, Brooks, & Hammett, 2006; Hammett, Champion, Thompson, & Morland, 2007; Stocker & Simoncelli, 2006; Langley & Anderson, 2007) but there is still no clear, agreed picture of exactly where in the pathway speed-tuning arises, nor how it is achieved. The location of an unambiguous speed signal is not only of anatomical interest but is likely to constrain models of how the spatio-temporally separable signals generated in the retina are transformed to provide behaviourally relevant cues to speed. Unfortunately previous attempts to determine the locus of speed encoding using both electrophysiological and imaging techniques have yielded inconclusive results.
There is considerable electrophysiological evidence to suggest that the early stages of visual processing are mediated by neurones whose responses are spatio-temporally separable (e.g. Tolhurst & Movshon, 1975; Foster, Gaska, Nagler & Pollen, 1985). Such neurones are tuned for limited ranges of spatial and temporal frequency and thus do not provide an unambiguous code for speed. More recent evidence of the speed tuning of many neurones in MT (e.g. Perrone & Thiele, 2001) and a direct link between their activity and speed perception (e.g. Rudolph & Pasternak, 1999; Liu & Newsome, 2005) raises the possibility that an explicit code for speed may be extracted from early spatially and temporally ...
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... response. The expectation of such a coupling, at least in MT, seems reasonable in light of evidence (Liu & Newsome, 2005) that individual neurons in MT play a direct role in speed perception. Thus examining the effect of a stimulus attribute that is known to affect perceived speed on BOLD responses may render a clearer picture of how and where cortical speed encoding occurs.
Recently, Hammett et al. (2007) have shown that perceived speed is modulated by mean luminance such that low luminance stimuli appear significantly faster at high speeds. Any coupling of the BOLD response to perceived speed should therefore be manifested by systematic differences in areas that encode speed. We have therefore measured the BOLD response to drifting sinusoidal gratings at a range of speeds and at two luminance levels above the scotopic range, in areas from the LGN to MST.
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One wonders what takes place in the brain to cause such phenomenal differences in perception. The cause is unknown for certain, like many things in the realm of science it has not been researched nearly enough, but there are some indications.
The ‘where visual pathway’ is concerned with constructing three dimensional representations of the environment and helps our brain to navigate where things are, independently of what they are, in space in relation to itself (Mishkin & Ungerleider & Macko, 1983).... ... middle of paper ... ... The 'Standard' of the 'Standard'.
Vision plays a huge role in the lives of non-human primates. Non-human primates have exceptional binocular vision, due to forward-facing eyes with overlapping visual fields (Prescott). This binocular stereoscopic color vision allows primates to see the world in terms of height, width, and depth, also known as three-dimensional vision (Haviland et al. 2010). Highly developed vision allows the later arboreal primates to judge depth, distance, and location when moving at speed from branch to branch (Haviland et al. 2010). This bino...
The researchers’ hypothesis is premised on a theory first proposed by Charles Darwin called the “facial feedback hypothesis” (Finzi et. al., 2014). Darwin suggested that the feedback our brains receive from the contraction of our facial muscles plays a casual role in cont...
...ce for increased activity in visual areas or the fusiform gyrus, which is connected with color perception. These results have shown that spoken words result in co-activation of color processing areas, but not visual areas connected with the perceptual process of color. Sadly, the conclusions don’t reveal which perceptual or cognitive processes might cause the difference with people with synaesthesia and the controls.
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This paper aims to endorse physicalism over dualism by means of Smart’s concept of identity theory. Smart’s article Sensations and the Brain provides a strong argument for identity theory and accounts for many of it primary objections. Here I plan to first discuss the main arguments for physicalism over dualism, then more specific arguments for identity theory, and finish with further criticisms of identity theory.
Bergmann, K., Schubert, A., Hagemann, D., & Schankin, A. (2015). Age-related differences in the P3 amplitude in change blindness. Psychological Research, 80(4), 660-676. doi:10.1007/s00426-015-0669-6
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The human body is divided into many different parts called organs. All of the parts are controlled by an organ called the brain, which is located in the head. The brain weighs about 2. 75 pounds, and has a whitish-pink appearance. The brain is made up of many cells, and is the control centre of the body. The brain flashes messages out to all the other parts of the body.