09 - Attention 2
- Sensory information processing is a highly evolved and very powerful feed-forward system. In primate visual cortex it consists of a hierarchy of areas that consist of increasingly selective neurons.
- In higher mammals this feed-forward system is influenced by top-down attentional influences that cause a selective modulation of sensory information processing based on the behavioral relevance of a stimulus.
- The modulation can be directed under automatic or voluntary control. Voluntary visual attention can be directed to a location in space or a non-spatial feature (such as a particular color or a particular direction of visual motion, etc.).
- Allocating attention changes the sensory gain of neurons, i.e. has a multiplicative effect of neuronal responses to a given stimulus.
- The magnitude of this gain change depends on the similarity of the attended stimulus’ properties and the sensory preferences of the neuron.
- These gain changes enhance the neural representation of attended sensory input and weaken the representation of unattended sensory input (‘push-pull’).
- The enhanced responses to attended stimuli also improve the discriminability of these stimuli.
Topics, concepts and teaching aims:
Treue S, Martinez-Trujillo JC. Feature-based attention influences motion processing gain in macaque visual cortex. Nature. 1999; 399:575-9.
Martinez-Trujillo JC, Treue S. Feature-based attention increases the selectivity of population responses in primate visual cortex. Current Biology. 2004;14:744-51.
- The two publications investigate feature-based attention in primate visual cortex. The first study reveals the existence of this form of attentional modulation and proposes a model of attention (feature similarity gain model). The second study is a follow up where the authors document that the effect of a simple gain change can be a non- multiplicative effect on the responses to a stimulus across a population of neurons.
- Teaching aims (Lernziele): Understand how an effect of feature-based attention can be shown at the level of single neurons (first publication), how it is similar to spatial attention (first publication), how the ‘feature similarity gain model’ integrates spatial- and feature-based attention (first publication) and how the ‘feature similarity gain model’ predicts the consequences of feature-based attentional modulation on the population response of an unattended vs. attended stimulus (second publication).
Womelsdorf T, Anton-Erxleben K, Pieper F, Treue S. Dynamic shifts of visual receptive fields in cortical area MT by spatial attention. Nature Neuroscience. 2006;9(9):1156-60.
Anton-Erxleben K, Henrich C, Treue S. Attention changes perceived size of moving visual patterns. Journal of Vision. 2007; 7(11):5, 1-9.
- The two publications share a common question from cognitive neuroscience but take two methodological approaches.
- Scientific question: Both publications are trying to determine the effects of spatial attention on the representation/perception of space. The first one investigates the effect of spatial attention on receptive field profiles in the visual cortex of rhesus monkeys and the second study investigates human spatial perception to determine if the receptive field changes observed in the first study have the hypothesized perceptual consequences.
- Method: The first study maps receptive fields while the animal is performing an attention task. The second study determines perceived size of objects in human studies when spatial attention is allocated near the object. Note that the method used in the second study is adapted from one of the publications (Carrasco_2004) discussed in the previous seminar. Note also that the second study is based on the ‘linking hypothesis’ (see seminar presentations attention I) that neuronal responses are causally related to perception. Therefore changes in neuronal responses should have characteristic perceptual consequences.
- Teaching aims (Lernziele): Understand how receptive fields can be mapped while an animal is performing a behavioral task and how a perceptual hypothesis based on the first study can be tested in human subjects.
Last update of this page: Jan 13, 2020