Space-Specific Deficits in Visual Orientation Discrimination Caused by Lesions in the Midbrain Stimulus Selection Network

Knudsen, Eric I and Schwarz, Jason S and Knudsen, Phyllis F and Sridharan, Devarajan (2017) Space-Specific Deficits in Visual Orientation Discrimination Caused by Lesions in the Midbrain Stimulus Selection Network. In: CURRENT BIOLOGY, 27 (14). 2053+.

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Abstract

Perceptual decisions require both analysis of sensory information and selective routing of relevant information to decision networks. This study explores the contribution of a midbrain network to visual perception in chickens. Analysis of visual orientation information in birds takes place in the forebrain sensory area called the Wulst, as it does in the primary visual cortex (V1) of mammals. In contrast, the midbrain, which receives parallel retinal input, encodes orientation poorly, if at all. We discovered, however, that small electrolytic lesions in the midbrain severely impair a chicken's ability to discriminate orientations. Focal lesions were placed in the optic tectum (OT) and in the nucleus isthmi pars parvocellularis (Ipc)-key nodes in the midbrain stimulus selection network-in chickens trained to perform an orientation discrimination task. A lesion in the OT caused a severe impairment in orientation discrimination specifically for targets at the location in space represented by the lesioned location. Distracting stimuli increased the deficit. A lesion in the Ipc produced similar but more transient effects. We discuss the possibilities that performance deficits were caused by interference with orientation information processing (sensory deficit) versus with the routing of information in the forebrain (agnosia). The data support the proposal that the OT transmits a space-specific signal that is required to gate orientation information from the Wulst into networks that mediate behavioral decisions, analogous to the role of ascending signals from the superior colliculus (SC) in monkeys. Furthermore, our results indicate a critical role for the cholinergic Ipc in this gating process.

Item Type:	Journal Article
Publication:	CURRENT BIOLOGY
Additional Information:	Copy right for this article belongs to the CELL PRESS, 50 HAMPSHIRE ST, FLOOR 5, CAMBRIDGE, MA 02139 USA
Department/Centre:	Division of Biological Sciences > Centre for Neuroscience
Date Deposited:	24 Aug 2017 07:15
Last Modified:	24 Aug 2017 07:15
URI:	http://eprints.iisc.ac.in/id/eprint/57641

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