Optogenetic stimulation of visual inputs to posterior parietal cortex biases choice behavior of rats on a multisensory decision task.

Sheppard, J. P., Ryan, M.B., Churchland, A. K. (November 2013) Optogenetic stimulation of visual inputs to posterior parietal cortex biases choice behavior of rats on a multisensory decision task. In: Neuroscience 2013, Nov 9th-13th 2013, San Diego, CA.

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Abstract

A central question in neuroscience concerns how the brain transforms sensory information into decisions. Microstimulation of specific cortical areas in monkeys during motion discrimination tasks has established causal links between neural activity within a particular cortical area and behavior. Here, we seek to establish a causal link between neural activity and behavior not in a single area, but in a pathway linking two areas. Specifically, we tested whether the pathway from primary visual cortex (V1) to posterior parietal cortex (PPC) plays a causal role in decision-making. To test whether the V1-PPC pathway drives decisions, we optically stimulated the axon terminals of V1 neurons that project to PPC. First, we injected an adeno-associated virus that constitutively expresses GFP-tagged Channelrhodopsin-2 (AAV2/9-CAGS-ChR2-eGFP) into left V1 of male Long Evans rats, and histologically confirmed expression in axons projecting to left PPC. Next, we repeated this procedure on an animal trained to report decisions about whether a series of auditory clicks or visual flashes was repeating at a high or low rate. The animal reported decisions by moving to a left or right reward port in response to the sensory stimuli. Finally, we implanted the animal with a microdrive in left PPC for tetrode recording and optogenetic stimulation. Subsequent optical stimulation in PPC generates action potentials in the axon terminals of V1-PPC projection neurons. Neurons from other cortical areas that project to PPC (e.g. auditory or somatosensory cortices) are unaffected by stimulation because those neurons do not express ChR2. Likewise, V1 neurons that do not project to PPC are unaffected because the optical stimulation is confined to PPC. Optical stimulation was presented alongside natural auditory or visual stimuli. Optical and control trials were interleaved; animals were rewarded on optical trials according to the normal task contingencies. Optical stimulation caused a consistent contralateral bias in the rat’s decisions. This effect was present across multiple stimulation sites and was approximately equal in magnitude when optical stimulation was paired with visual or auditory stimuli. To ensure that the bias was not driven by an inadvertent visual cue provided by laser light escaping from the sealed implant enclosure, we performed control experiments with the laser connected to a ferrule with no implanted fiber. During control sessions, optical stimulation had no effect on behavior. We draw two main conclusions: (1) The V1-PPC pathway of rats is causally involved in decisions on the task; (2) The V1-PPC pathway selectively affects contralateral movements.

Item Type: Conference or Workshop Item (Poster)
Subjects: organism description > animal behavior
organism description > animal behavior > decision making
Investigative techniques and equipment > optogenetics
organs, tissues, organelles, cell types and functions > tissues types and functions > parietal cortex
organism description > animal > mammal > rodent > rat
organism description > animal > mammal > rodent > rat
CSHL Authors:
Communities: CSHL labs > Churchland lab
Depositing User: Matt Covey
Date: November 2013
Date Deposited: 14 Nov 2013 21:00
Last Modified: 14 Nov 2013 21:00
Related URLs:
URI: http://repository.cshl.edu/id/eprint/28864

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