Genetically Defined Functional Modules for Spatial Orienting in the Mouse Superior Colliculus.
Curr Biol 2019;
29:2892-2904.e8. [PMID:
31474533 PMCID:
PMC6739420 DOI:
10.1016/j.cub.2019.07.083]
[Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 07/26/2019] [Accepted: 07/30/2019] [Indexed: 01/27/2023]
Abstract
In order to explore and interact with their surroundings, animals need to orient toward specific positions in space. Throughout the animal kingdom, head movements represent a primary form of orienting behavior. The superior colliculus (SC) is a fundamental structure for the generation of orienting responses, but how genetically distinct groups of collicular neurons contribute to these spatially tuned behaviors remains largely to be defined. Here, through the genetic dissection of the murine SC, we identify a functionally and genetically homogeneous subclass of glutamatergic neurons defined by the expression of the paired-like homeodomain transcription factor Pitx2. We show that the optogenetic stimulation of Pitx2ON neurons drives three-dimensional head displacements characterized by stepwise, saccade-like kinematics. Furthermore, during naturalistic foraging behavior, the activity of Pitx2ON neurons precedes and predicts the onset of spatially tuned head movements. Intriguingly, we reveal that Pitx2ON neurons are clustered in an orderly array of anatomical modules that tile the entire intermediate layer of the SC. Such a modular organization gives origin to a discrete and discontinuous representation of the motor space, with each Pitx2ON module subtending a defined portion of the animal’s egocentric space. The modularity of Pitx2ON neurons provides an anatomical substrate for the convergence of spatially coherent sensory and motor signals of cortical and subcortical origins, thereby promoting the recruitment of appropriate movement vectors. Overall, these data support the view of the superior colliculus as a selectively addressable and modularly organized spatial-motor register.
Pitx2 expression labels a functionally homogeneous class of projecting SC neurons
Pitx2ON neurons drive three-dimensional head movements during foraging behavior
Pitx2ON neurons are organized in an orderly array of anatomical modules
Modularity of Pitx2ON neurons defines a discrete motor map for spatial orienting
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