RTG 2175 Perception in Context and its neural Basis
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New TP Straube/Deubel

We are looking for a PhD student with a strong interest in human movement sciences and motor learning.

Task- and context-specific plasticity of multi-level, redundant sensory-motor processing


Scientific background

The stunning flexibility of human sensorimotor learning is due to plasticity on multiple levels of motor control between motor execution and sequential motor planning. Classic low level motor adaptation concerns the reshaping of muscle innervations necessary to compensate for changes in plant characteristics such as muscle recruitment or external loads. This aspect of sensory-motor learning is most important for adapting movements that are directly driven by a sensorimotor error signal (e.g. fast eye movements (saccades) to a visual target). In contrast, sequential motor planning is essential for the execution of fast automated motor sequences in which a sequence of motor actions is elicited by a context dependent trigger signal and recalled from either a motor or spatial memory (e.g. the sequence of saccades generated to scan a well known environment). These two mechanisms are partially redundant, and may both play an important role in adaptation of internally guided movements.
This project investigates the interface between low level motor adaptation and non-motor spatial learning in the adaptation of internally guided saccades. In a series of eye movement experiments we will address the question of which conditions determine whether the adaptation of internally guided saccades is achieved by low level motor adaptation (reshaping of the motor command independently of the sequential context) or by memorizing a new motor sequence (sequential motor learning).


Methods

Eye movements are measured by video-oculography allowing online detection of eye position and saccade contingent visual stimulation. Adaptation of saccades will be induced by systematic shifts of the target configuration during the saccade to induce systematic post-saccadic motor errors. Data analysis is focused on the parameterization of movement profiles and quantification of sequence learning as established in previous studies.


Contact

Dr. Ing. Thomas Eggert, Department of Neurology, LMU Munich  eggert@lrz.uni-muenchen.de

 

 

ReflexiveAdapdation_a


Adaptation of reflexive saccades in humans: During a training session, the primary target step is followed by a secondary target step which is triggered by the saccade executed in response to the primary step. The secondary step systematically reduces the primary target eccentricity by 30% and induces (at the beginning of the training) an increased post-saccadic error. A) At the end of the training session, the subject learned to decrease the primary saccade amplitude to reduce the post-saccadic error. B) In response to ordinary target steps immediately after training, the adapted saccades undershot the target and were followed by corrective saccades. C) Time course of the decrease of the saccade amplitude (crosses) during training, fitted by an exponential function (red line).


Literature


Deubel H (1995) Separate adaptive mechanisms for the control of reactive and volitional saccadic eye movements. Vision research 35:3529-3540
Drever J, Straube A, Eggert T (2011) Learning deferred imitation of long spatial sequences. Behav Brain Res 220:74-82 doi: 10.1016/j.bbr.2011.01.027
Eggert T, Drever J, Straube A (2014) Interference-free acquisition of overlapping sequences in explicit spatial memory. Behavioural brain research 262:21–30
Straube A, Deubel H (1995) Rapid gain adaptation affects the dynamics of saccadic eye movements in humans. Vision research 35:3451-3458
Straube A, Deubel H, Ditterich J, Eggert T (2001) Cerebellar lesions impair rapid saccade amplitude adaptation. Neurology 57:2105-2108