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Curr Biol. 2017 May 8;27(9):1356-1361. doi: 10.1016/j.cub.2017.03.068. Epub 2017 Apr 27.

Feedback Synthesizes Neural Codes for Motion.

Author information

1
Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada. Electronic address: stephen.elisha.clarke@gmail.com.
2
Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada; Brain and Mind Institute, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada; Center for Neural Dynamics, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada.

Abstract

In senses as diverse as vision, hearing, touch, and the electrosense, sensory neurons receive bottom-up input from the environment, as well as top-down input from feedback loops involving higher brain regions [1-4]. Through connectivity with local inhibitory interneurons, these feedback loops can exert both positive and negative control over fundamental aspects of neural coding, including bursting [5, 6] and synchronous population activity [7, 8]. Here we show that a prominent midbrain feedback loop synthesizes a neural code for motion reversal in the hindbrain electrosensory ON- and OFF-type pyramidal cells. This top-down mechanism generates an accurate bidirectional encoding of object position, despite the inability of the electrosensory afferents to generate a consistent bottom-up representation [9, 10]. The net positive activity of this midbrain feedback is additionally regulated through a hindbrain feedback loop, which reduces stimulus-induced bursting and also dampens the ON and OFF cell responses to interfering sensory input [11]. We demonstrate that synthesis of motion representations and cancellation of distracting signals are mediated simultaneously by feedback, satisfying an accepted definition of spatial attention [12]. The balance of excitatory and inhibitory feedback establishes a "focal" distance for optimized neural coding, whose connection to a classic motion-tracking behavior provides new insight into the computational roles of feedback and active dendrites in spatial localization [13, 14].

KEYWORDS:

ON and OFF cells; burst spiking; cerebellum; electric fish; gain control; motion tracking; neural coding; spatial attention; top-down processing; topographic feedback

PMID:
28457872
DOI:
10.1016/j.cub.2017.03.068
[Indexed for MEDLINE]
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