Exploring the coding space of tactile localization in the antennal system of the stick insect
-
1
Bielefeld University, Department of Biological Cybernetics, Germany
-
2
Bielefeld University, Cognitive Interaction Technology - Center of Excellence (CITEC), Germany
Stick insects (Carausius morosus) use their antennae as actively movable, tactile sensors to search the space ahead for obstacles during locomotion. Antennal contact positions reliably predict subsequent foot contact positions when stick insects climb an obstacle (Schütz and Dürr, Phil.Trans.R.Soc.Lond, 2011). This indicates that information about antennal posture during contact with an external object is mediated to thoracic neural networks controlling front leg movement. In search of the mediating neurons, we characterize a population of descending interneurons (DINs) which are sensitive to antennal posture and movement, and potentially connect the head to thoracic ganglia. These DINs could be part of the neural pathways connecting antennal mechanoreceptors and front legs.
We recorded from 100 DINs with sharp microelectrodes while stimulating the distal of the two antennal joints (the scape-pedicel-joint, SP-joint). Based on their sensitivity to different parameters of imposed SP-joint movement, we subdivided the population of DINs into five groups.
1) The spike rate of simple position-sensitive DINs was correlated with the current SP-joint angle, independent of whether the antenna was moving or not. The group of simple position-sensitive DINs showed range fractionation, and individual DINs fired either preferentially at ventral, dorsal, or both extreme angles. 2) Unspecific movement-sensitive DINs exhibited a high, stimulus-independent background activity. However, antennal movement reliably elicited additional spikes in these DINs, independent of movement velocity, direction, and amplitude. 3) Dynamic position-sensitive DINs fired only during SP-joint movement within a certain joint angle range. They exhibited very low spike rates (< 0.5 Hz) when SP-joint movement stopped, which separated them from simple position-sensitive DINs. 4) Positive velocity-sensitive DINs had a low baseline frequency in the absence of antennal movement, and started spiking vigorously as soon as the antenna was moved. Their spike rate was positively correlated with joint angle velocity. 5) Negative velocity-sensitive DINs had a high spike frequency in the absence of antennal movement (around 20 Hz), and were inhibited during SP-joint movement. Their spike rate was negatively correlated with joint angle velocity. Simultaneous recordings from positive and negative velocity-sensitive DINs revealed synchronous input to both neuron types.
We calculated the sensitivity of a subset of 70 DINs to three parameters of SP-joint stimulation (movement, direction, and position) at four movement velocities and analyzed the ‘sensitivity space’ of the DIN population using Principal Component Analysis (PCA). The DINs clustered according to the functional groups. However, PCA also revealed that most DINs were sensitive to several parameters of SP-joint movement, rather than just one. For example, velocity- and dynamic position-sensitive DINs were also sensitive to movement direction, and simple position-sensitive DINs were weakly sensitive to movement direction and velocity. The co-sensitivity of some DINs to the direction of movement might compensate for the absence of purely direction-sensitive DINs, which we did not find.
In summary, our data show that the population of DINs conveys detailed information about antennal position, movement, and movement velocity to thoracic networks, where it could be used in front-leg targeting during obstacle negotiation.
Keywords:
antenna,
descending interneuron,
Electrophysiology,
mechanosensory processing,
motor control,
Principal Component Analysis,
stick insect,
Touch
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for participant symposium and student poster award)
Topic:
Sensorimotor Integration
Citation:
Ache
JM and
Dürr
V
(2012). Exploring the coding space of tactile localization in the antennal system of the stick insect.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00147
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
27 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Mr. Jan M Ache, Bielefeld University, Department of Biological Cybernetics, Bielefeld, 33615, Germany, jan_marek.ache@uni-bielefeld.de