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Behavioral/Systems/Cognitive Gain Mechanisms for Contextually Guided
 

Summary: Behavioral/Systems/Cognitive
Gain Mechanisms for Contextually Guided
Visuomotor Transformations
Marina Brozovic´,1* Alexander Gail,1,2* and Richard A. Andersen1
1Division of Biology, California Institute of Technology, Pasadena, California 91125, and 2Bernstein Center for Computational Neuroscience, German
Primate Center, 37077 Go¨ttingen, Germany
Aprevailingquestioninsensorimotorresearchistheintegrationofsensorysignalswithabstractbehavioralrules(contexts)andhowthis
results in decisions about motor actions. We used neural network models to study how context-specific visuomotor remapping may
depend on the functional connectivity among multiple layers. Networks were trained to perform different rotational visuomotor associ-
ations,dependingonthestimuluscolor(anonspatialcontextsignal).InnetworkI,thecontextsignalwaspropagatedforwardthroughthe
network (bottom-up), whereas in network II, it was propagated backwards (top-down). During the presentation of the visual cue stim-
ulus, both networks integrate the context with the sensory information via a mechanism similar to the classic gain field. The recurrence
in the networks hidden layers allowed a simulation of the multimodal integration over time. Network I learned to perform the proper
visuomotor transformations based on a context-modulated memory of the visual cue in its hidden layer activity. In network II, a brief
visual response, which was driven by the sensory input, is quickly replaced by a context-modulated motor-goal representation in the
hiddenlayer.Thishappensbecauseofadominantfeedbacksignalfromtheoutputlayerthatfirstconveyscontextinformation,andthen,
after the disappearance of the visual cue, conveys motor goal information. We also show that the origin of the context information is not
necessarilycloselytiedtothetop-downfeedback.However,wesuggestthatthepredominanceofmotor-goalrepresentationsfoundinthe
parietal cortex during context-specific movement planning might be the consequence of strong top-down feedback originating from
within the parietal lobe or from the frontal lobe.

  

Source: Andersen, Richard - Division of Biology, California Institute of Technology
Crawford, Doug - York Centre for Vision Research, York University (Toronto)

 

Collections: Biology and Medicine