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Published on: August 14, 2013
Direction-specific disruption of subcortical visual behavior and receptive fields in mice lacking the beta2 subunit
Lupeng Wang1, Krsna V Rangarajan, Courtney A Lawhn-Heath
1Department of Neurobiology and Physiology and Interdepartmental Neuroscience Program, Northwestern University, Evanston, Illinois 60208, USA.
Abstract:
Retinotopic mapping is a basic feature of visual system organization, but its role in processing visual information is unknown. Mutant mice lacking the beta2 subunit of nicotinic acetylcholine receptor have imprecise maps in both visual cortex (V1) and the superior colliculus (SC) due to the disruption of spontaneous retinal activity during development. Here, we use behavioral and physiological approaches to study their visual functions. We find that beta2-/- mice fail to track visual stimuli moving along the nasotemporal axis in a subcortical optomotor behavior, but track normally along the dorsoventral axis. In contrast, these mice display normal acuity along both axes in the visual water task, a behavioral test of cortical functions. Consistent with the behavioral results, we find that V1 neurons in beta2-/- mice have normal response properties, while SC neurons have disrupted receptive fields, including enlarged structure and decreased direction and orientation selectivity along the nasotemporal axis. The subcortical-specific deficits indicate that retinotopic map disruption has different impacts on the development of functional properties in V1 and the SC.
Insights
Mice lacking the beta2 nicotinic acetylcholine receptor subunit show impaired subcortical visual processing, specifically along the nasotemporal axis, impacting the superior colliculus but not the visual cortex.
Area of Science:
- Neuroscience
- Developmental Biology
- Visual System Organization
Background:
- Retinotopic mapping is fundamental to visual system organization.
- The precise role of retinotopic maps in visual information processing remains unclear.
- Mutant mice lacking the beta2 subunit of nicotinic acetylcholine receptor exhibit developmental disruptions in spontaneous retinal activity, leading to imprecise retinotopic maps in the visual cortex (V1) and superior colliculus (SC).
Purpose of the Study:
- To investigate the functional consequences of disrupted retinotopic mapping in beta2-/- mice.
- To differentiate the impact of retinotopic map disruption on subcortical (SC) versus cortical (V1) visual processing.
- To elucidate the role of retinotopic organization in visual information processing.
Main Methods:
- Behavioral analysis using subcortical optomotor and visual water tasks.
- In vivo electrophysiological recordings of neuronal activity in V1 and SC.
- Assessment of receptive field properties, direction, and orientation selectivity.
Main Results:
- Beta2-/- mice demonstrated deficits in tracking visual stimuli along the nasotemporal axis in subcortical behavior but showed normal tracking along the dorsoventral axis.
- Normal visual acuity was observed in beta2-/- mice for both axes in the cortical visual water task.
- V1 neurons exhibited normal response properties, while SC neurons displayed disrupted receptive fields, including enlarged structures and reduced direction/orientation selectivity along the nasotemporal axis.
Conclusions:
- Disrupted retinotopic maps due to the absence of the beta2 subunit have distinct functional impacts on subcortical and cortical visual processing centers.
- Subcortical visual functions, particularly along the nasotemporal axis, are more sensitive to retinotopic map imprecision.
- These findings highlight the critical role of precise retinotopic organization for specific visual processing streams, particularly within the superior colliculus.
