Bottom-up retinotopic organization supports top-down mental imagery

Finding a path between locations is a routine task in daily life. Mental navigation is often used to plan a route to a destination that is not visible from the current location. We first used functional magnetic resonance imaging (fMRI) and surface-based averaging methods to find high-level brain regions involved in imagined navigation between locations in a building very familiar to each participant. This revealed a mental navigation network that includes the precuneus, retrosplenial cortex (RSC), parahippocampal place area (PPA), occipital place area (OPA), supplementary motor area (SMA), premotor cortex, and areas along the medial and anterior intraparietal sulcus. We then visualized retinotopic maps in the entire cortex using wide-field, natural scene stimuli in a separate set of fMRI experiments. This revealed five distinct visual streams or ‘fingers’ that extend anteriorly into middle temporal, superior parietal, medial parietal, retrosplenial and ventral occipitotemporal cortex. By using spherical morphing to overlap these two data sets, we showed that the mental navigation network primarily occupies areas that also contain retinotopic maps. Specifically, scene-selective regions RSC, PPA and OPA have a common emphasis on the far periphery of the upper visual field. These results suggest that bottom-up retinotopic organization may help to efficiently encode scene and location information in an eye-centered reference frame for top-down, internally generated mental navigation. This study pushes the border of visual cortex further anterior than was initially expected

Investigating Spatial Memory and Navigation in Developmental Amnesia: Evidence from a Google Street View Paradigm, Mental Navigation Tasks, and Route Descriptions

This dissertation examined the integrity of spatial representations of extensively travelled environments in developmental amnesia, thereby elucidating the role of the hippocampus in forming and retrieving spatial memories that enable flexible navigation. Previous research using mental navigation tasks found that developmental amnesic case H.C., an individual with atypical hippocampal development, could accurately estimate distance and direction between landmarks, but her representation of her environment was fragmented, inflexible, and lacked detail (Rosenbaum, Cassidy, & Herdman, 2015). Study 1 of this dissertation examined H.C.s spatial memory of her home environment using an ecologically valid virtual reality paradigm based on Google Street View. H.C. and control participants virtually navigated routes of varying familiarity within their home environment. To examine whether flexible navigation requires the hippocampus, participants also navigated familiar routes that had been mirror-reversed. H.C. performed similarly to control participants on all route conditions, suggesting that spatial learning of frequently travelled environments can occur despite compromised hippocampal system function. H.C.s unexpected ability to successfully navigate mirror-reversed routes might reflect the accumulation of spatial knowledge of her environment over the 6 years since she was first tested with mental navigation tasks. As such, Study 2 investigated how spatial representations of extensively travelled environments change over time in developmental amnesia by re-testing H.C. on mental navigation tasks 8 years later. H.C. continued to draw sketch maps that lacked cohesiveness and detail and had difficulty sequencing landmarks and generating detours on a blocked route task, suggesting that her overall representation of the environment did not improve over 8 years. Study 3 thoroughly examined the integrity of H.C.s detailed representation of the environment using a route description task. H.C. accurately described perceptual features of landmarks along a known route, but provided inaccurate information regarding the spatial relations of landmarks, resulting in a fragmented mental representation of the route. Taken together, these results contribute meaningfully to our current understanding of the integrity of spatial representations of extensively travelled environments in developmental amnesia. Non-spatial factors that could influence performance on navigation and spatial memory tasks are discussed, as is the impact of these results on theories of hippocampal function

Imagination through virtuality for in-depth learning

Based on the fast growing technologies to allow students to explore and experience three-dimensional worlds, the question becomes relevant if and how technology offers essentially new dimensions to the learning process. In a number of prototypes this paper demonstrates how learners may undergo immersive experiences that complement the predominantly verbal expositions how complex realities like the many-facetted processes in living creatures work. Based upon the model of a mammal's heart, pre- and postsynaptic processing and finally the apprehension of cultural signs on migration, identity, culture and communication, this paper aims at provoking the discussion in how far we may already rely on visual semiotics that may complement traditional learning material and further stimulate the further evolution into perceptual learning. Based on experiments into the relation between cognitive style (holistic versus serialistic) and various memory capacities, the thesis is brought forward that we need to explore further the various concept-mapping techniques, both for the designer and the user of educational learning environment

Anterior Hippocampus and Goal-Directed Spatial Decision Making

Contains fulltext : 115487.pdf (publisher's version ) (Open Access

Anterior Hippocampus and Goal-Directed Spatial Decision Making

Contains fulltext : 115487.pdf (publisher's version ) (Open Access

TGVizTab: An ontology visualisation extension for Protégé

Ontologies are gaining a lot of interest and many are being developed to provide a variety of knowledge services. There is an increasing need for tools to graphically and in-teractively visualise such modelling structures to enhance their clarification, verification and analysis. Protégé 2000 is one of the most popular ontology modelling tools currently available. This paper introduces TGVizTab; a new Protégé plugin based on TouchGraph technology to graphically visualise Protégé?s ontologies

Topological Schemas of Memory Spaces

Hippocampal cognitive map---a neuronal representation of the spatial environment---is broadly discussed in the computational neuroscience literature for decades. More recent studies point out that hippocampus plays a major role in producing yet another cognitive framework that incorporates not only spatial, but also nonspatial memories---the memory space. However, unlike cognitive maps, memory spaces have been barely studied from a theoretical perspective. Here we propose an approach for modeling hippocampal memory spaces as an epiphenomenon of neuronal spiking activity. First, we suggest that the memory space may be viewed as a finite topological space---a hypothesis that allows treating both spatial and nonspatial aspects of hippocampal function on equal footing. We then model the topological properties of the memory space to demonstrate that this concept naturally incorporates the notion of a cognitive map. Lastly, we suggest a formal description of the memory consolidation process and point out a connection between the proposed model of the memory spaces to the so-called Morris' schemas, which emerge as the most compact representation of the memory structure.Comment: 24 pages, 8 Figures, 1 Suppl. Figur

Allocentric directional processing in the rodent and human retrosplenial cortex

Copyright © 2014 Knight and Hayman. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these termsHead direction (HD) cells in the rodent brain have been investigated for a number of years, providing us with a detailed understanding of how the rodent brain codes for allocentric direction. Allocentric direction refers to the orientation of the external environment, independent of one’s current (egocentric) orientation. The presence of neural activity related to allocentric directional coding in humans has also been noted but only recently directly tested. Given the current status of both fields, it seems beneficial to draw parallels between this rodent and human research. We therefore discuss how findings from the human retrosplenial cortex (RSC), including its “translational function” (converting egocentric to allocentric information) and ability to code for permanent objects, compare to findings from the rodent RSC. We conclude by suggesting critical future experiments that derive from a cross-species approach to understanding the function of the human RSCPeer reviewedFinal Published versio