Evaluating the Feature Similarity Gain and Biased Competition Models of Attentional Modulation
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1
Bernstein Center for Computational Neuroscience, Germany
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2
German Primate Center, Germany
Visual attention enables the brain to enhance the behaviorally relevant neuronal population responses and suppresses the irrelevant information. In the past several models have been proposed for the mechanisms of attention. Two more general theories include the biased competition model (BCM) and the feature similarity gain model (FSGM), The BCM assumes that stimuli compete for neuronal responses and attention biases this competition towards the behaviorally relevant stimulus. The response to two different stimuli inside the same receptive field is therefore biased towards the attended stimulus, i.e. a neuron’s response under those attentional conditions approaches the response evoked by the attended stimulus alone. The FSGM states that the gain of attentional modulation is a function of the similarity between the attended feature and a cell’s preferred feature. Comparing responses when attending to one or the other of two stimuli inside a receptive field causes the higher response for the condition where the attended stimulus is better matched to the preferences of the neuron, such as its preferred direction of motion. Here, we evaluated the two models using by designing a paradigm which yields different predictions for each model. We placed two coherently moving random dot patterns (RDPs) inside the receptive field (RF) of direction-selective neurons in the medial-temporal area MT of two macaque monkeys. Both patterns moved in the preferred direction of the neuron but elicited different responses because they differed in their contrast. In a given trial the animal was cued to attend either the low or the high-contrast patterns and to release a lever as soon as a direction change occurred in the cued pattern while ignoring changes in the uncued stimulus. Because the two RDPs evoke different responses when presented alone, the BCM predicts a lower response when the animals attended to the low contrast RDP. Because the two RDPs move in the same direction, the similarity between the attended and preferred feature does not change when the animals attend to one vs. the other RDP in the RF. The FSGM therefore predicts the same response in both conditions. We recorded the responses of 81 MT cells of two macaque monkeys. Their responses were significantly modulated by spatial attention. On average these neurons showed a response increase of approx. 20% when the monkeys switched their attention from outside of the receptive field (RF) to a stimulus inside the RF. But in the relevant comparison, i.e. when attention was directed to the low vs. the high contrast pattern inside the receptive field, no significant change in responses was observed. In conclusion our data demonstrates an attentional modulation in primate extrastriate visual cortex that is not consistent with the biased competition model of attention but rather is better accounted for by the feature similarity gain model.
Acknowledgments:This work was supported by grant 01GQ0433 from the Federal Ministry of Education and Research to the Bernstein Center for Computational Neuroscience Goettingen.
Conference:
Bernstein Conference on Computational Neuroscience, Frankfurt am Main, Germany, 30 Sep - 2 Oct, 2009.
Presentation Type:
Poster Presentation
Topic:
Sensory processing
Citation:
Daliri
MR,
Kozyrev
V and
Treue
S
(2009). Evaluating the Feature Similarity Gain and Biased Competition Models of Attentional Modulation.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference on Computational Neuroscience.
doi: 10.3389/conf.neuro.10.2009.14.134
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Received:
27 Aug 2009;
Published Online:
27 Aug 2009.
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Correspondence:
Mohammad R Daliri, Bernstein Center for Computational Neuroscience, Göttingen, Germany, mdaliri@gwdg.de