Attention and location effects on spatial memory: Testing the predictions of a computational model
Byrne, Becker, and Burgess (2007) proposed a computational model of the neural mechanisms underlying spatial memory and mental imagery, which we shall refer to as the BBB model. They proposed that egocentric information about space from the dorsal visual pathway is combined with object information from the ventral visual pathway to form allocentric representations of spatial scenes in long-term memory at the level of the hippocampus. Similarly, memories about spatial locations can be retrieved from allocentric (view-invariant) long-term memory in the hippocampus and mapped through reciprocal neuronal pathways to generate egocentric mental images. The BBB model postulates some of the neural mechanisms that may underlie allocentric spatial memory, but it does not tell us what sort of features might contribute to the creation of these memories.
We conducted five experiments using a virtual driving task to further elucidate the conditions under which objects would be encoded as part of an allocentric spatial map as per the BBB model, versus an egocentric visual snapshot memory. We found that the spatial locations of objects at navigationally relevant points (i.e. decision points) were generally better remembered than were the locations of other objects, despite equivalent recognition memory for both types of objects. Additionally, the variance in spatial memory errors across viewpoints was significantly smaller for the decision-point objects than for the non-decision-point objects, indicating that the participants were more likely to have employed egocentric representations to encode the non-decision-point objects and allocentric representations to encode the decision-point objects, as predicted. However, some participants appeared to use predominantly an allocentric strategy (as identified by performance on a subsequent mapping test -- "good mappers") while others used an egocentric strategy ("poor mappers"). The good mappers showed decreasing variability in spatial memory errors between the tested viewpoints across experimental blocks, while the poor mappers showed increasing variability across blocks. Interestingly, manipulating attention to the non-decision-point objects eliminated the navigational relevance effect in good mappers, but enhanced it in poor mappers. Overall, these results are consistent with the predictions of the BBB model. Information about identity and location are stored separately and integrated at the level of the hippocampus and peri-hippocampal regions (e.g. perirhinal and parahippocampal cortices). Objects may either be processed within the ventral visual stream when treated as independent objects, or within the dorsal visual stream when treated as landmarks integrated into a large-scale allocentric spatial representation, or both. However, the results reported here suggest a further refinement of the BBB model, that is, objects in the environment may or may not be treated as landmarks, depending on where they are located (i.e. relevant to navigation or not) and how they are attended to. It would be of interest to know which neural structures are more active in our task. Whereas Janzen and van Turrenout (2004) found more hippocampal and parahippocampal activation for decision-point objects than non-decision-point objects, we predict that non-decision-point objects could evoke equally strong hippocampal activation when attention to those objects is appropriately manipulated.
Conference:
Computational and systems
neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009.
Presentation Type:
Poster Presentation
Topic:
Poster Presentations
Citation:
(2009). Attention and location effects on spatial memory: Testing the predictions of a computational model.
Front. Syst. Neurosci.
Conference Abstract:
Computational and systems
neuroscience 2009.
doi: 10.3389/conf.neuro.06.2009.03.023
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Received:
30 Jan 2009;
Published Online:
30 Jan 2009.