Interactions Between Afferent Channels In Vision: Basic Neurophysiology And Implications For The Pathology Of Dyslexia
Funder
National Health and Medical Research Council
Funding Amount
$423,662.00
Summary
We intend to study the interactions between different information channels in the primate visual system. The pathways from the eyes to the brain consist of different types of nerve fibres carrying distinct sorts of information. These channels have been believed to remain separate as they transmit the information through various levels of the brain. Finally, in the neocortex, it has been suggested that the visual information goes along two major streams, one dorsally to the parietal cortex and th ....We intend to study the interactions between different information channels in the primate visual system. The pathways from the eyes to the brain consist of different types of nerve fibres carrying distinct sorts of information. These channels have been believed to remain separate as they transmit the information through various levels of the brain. Finally, in the neocortex, it has been suggested that the visual information goes along two major streams, one dorsally to the parietal cortex and the other ventrally to the temporal cortex. Based upon recent studies, we question this strict segregation of the pathways and propose to study how interactions occur between the two streams and whether the two channels do come together at early levels of the visual pathway. We will also test our idea whether, of the dorsal and ventral streams, one stream might actually gate the other and decide what goes through the other stream. In fact, from our own recent studies, we have reason to believe that the way our attentional system might operate to select salient aspects of the visual scene may be through the dorsal stream selecting what goes into the ventral stream, which seems to be responsible for identifying objects. In the proposed project we will test this idea rigorously. From various lines of evidence, we also argue that the neural mechanisms that underlie this attentional spotlight is exploited by human children when they learn to read. It follows that any defect in the dorsal pathway or in the fibres and cells that feed into this will cause difficulties in reading. We believe this to be the underlying problem in dyslexic children. The project will undertake a number of experiments to test this idea.Read moreRead less
Cortical Interactions Of Parallel Afferent Channels Underlying Visual Perception, Attention And Memory
Funder
National Health and Medical Research Council
Funding Amount
$410,250.00
Summary
The visual pathways from the eyes to the brain consist of distinct groups of cells which are specialised to signal different aspects of the visual scene such as colour, contrast and movement. As the information they carry is relayed through and processed in many different regions of the brain these parallel information channels were, until recently, believed to remain completely separate from each other. Furthermore, it had been proposed that as the information reaches the visual neocortex the i ....The visual pathways from the eyes to the brain consist of distinct groups of cells which are specialised to signal different aspects of the visual scene such as colour, contrast and movement. As the information they carry is relayed through and processed in many different regions of the brain these parallel information channels were, until recently, believed to remain completely separate from each other. Furthermore, it had been proposed that as the information reaches the visual neocortex the information is channeled through two main largely parallel information processing streams, a dorsal stream to the parietal cortex (a where system) and a ventral stream to the temporal cortex (a what system). However, our recent functional studies (and anatomical studies from other laboratories) have indicated that the different information channels do interact already at a relatively early level of the visual pathway, namely in the primary visual cortex. We have shown this in two ways: (1) there is convergence of different information channels on individual neurones in the primary visual cortex; (2) signals from the faster where pathway comes back to the primary visual cortex to gate the slower channels going into the ventral what pathway. We have seen this occur in an attention paradigm and in a memory task. We will explore these interactions further to test hypotheses about: (1) how the convergence of different information channels relate to the functional and anatomical architecture of the visual cortex; (2) investigate at length the most poorly understood, the so-called koniocellular pathway from the retina to the cortex. This pathway seems to contain a specialised component which carries information about blue objects; (3) identify the source of the spotlight of attention we have discovered and (4) how and from where early visual structures receive the gating inputs in certain memory tasks.Read moreRead less
Cortical Interactions Between Afferent Channels In Macaque Visual System
Funder
National Health and Medical Research Council
Funding Amount
$380,154.00
Summary
There are three distinct groups of cells that carry the visual information from the eyes to the brain, each pathway signaling a different aspect of the visual scene. This project will study in detail the lesser known of these three pathways (koniocellular neurones): what sort of information they carry into the brain, how it is combined with the other pathways to yield our composite picture and where in the brain such combination takes place.
In the normal process of hearing, the brain actively selects sounds of interest from competing background sounds. This normal auditory function is indispensible for children and adults to cope in non-optimal listening environments, however the mechanisms by which such performance is achieved are poorly understood. This project will investigate the nerve circuits that enable this to occur and will also investigate how these circuits malfunction in various types of partial deafness. The results wi ....In the normal process of hearing, the brain actively selects sounds of interest from competing background sounds. This normal auditory function is indispensible for children and adults to cope in non-optimal listening environments, however the mechanisms by which such performance is achieved are poorly understood. This project will investigate the nerve circuits that enable this to occur and will also investigate how these circuits malfunction in various types of partial deafness. The results will improve our understanding of how we detect sounds and the impact of hearing pathologies on this process.Read moreRead less