Decoding Cortical Motor Goal Representations in a 3D Real-World Environment
by Michael Berger
Date of Examination:2017-10-26
Date of issue:2018-10-10
Advisor:Prof. Dr. Alexander Gail
Referee:Prof. Dr. Hansjörg Scherberger
Referee:Prof. Dr. Fred Wolf
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Description:Dissertation
Abstract
English
In sensorimotor neuroscience a certain motor behavior, and its underlying neuronal mechanism, is usually studied in isolation and tightly constrained by the experimental setting to provide interpretable results. When studying goal-directed arm movements, human participants or non-human primates are seated in front of an experimental workspace and instructed to perform a behavioral task while being prevented from performing undesired behavior such as leg or body movements. Thus, previous research about spatial processing related to goal-directed primate behavior focused primarily on the immediate reachable space in front of the body. It is unclear how the primate brain encodes motor goals beyond the immediate reach to which body relocation is necessary to reach the goal. Moreover, there is no experimental environment that allows studying motor goal encoding in primates involving walking. The studies described in this thesis investigated goal-directed walk-and-reach movements to far-located targets. New experimental environments were developed that allow sensorimotor neuroscience studies without using physical restraint. This approach is also used to refine the behavioral training of rhesus macaques leading to an improvement of animal welfare for non-human primates in neuroscience. This thesis contains five original manuscripts. First: Visuo-tactile integration of healthy human participants performing goal-directed walk-and-reach movements was investigated. This study shows that the peri-personal space, defined by a high level of multisensory integration, extends towards motor goals even beyond the immediate reachable space. Second: Description of the Reach Cage; An experimental environment for unrestrained rhesus macaques that allows wireless electrophysiology while the animal performs a behavioral task involving whole-body movements such as walk-and-reach movements. Third: The Reach Cage was used to study the encoding of walk-and-reach motor goals in the three cortical areas of the frontoparietal reach network (posterior parietal reach region PRR, dorsal premotor cortex PMd and primary motor cortex M1) in one rhesus macaque. Fourth: Description of the eXperimental Behavioral Instrument (XBI); A cage-based training device allowing the training of rhesus macaques to typical behavioral tasks used in sensorimotor neuroscience without the need for the animals to leave their housing environment. Fifth: The XBI was used to develop a fully automatized training regime for which the training progress was controlled only by the task performance of the individual animal rather than a human trainer. Such an automatized approach allows the comparison of animals’ training progress without the influence of subjective decisions. In conclusion, the work described in this thesis emphasizes the importance of experimental environments without physical restraint to A) study motor behavior and motor goal encoding involving whole-body movements, such as walk-and-reach movements and B) improve animal welfare for non-human primates in neuroscience.
Keywords: Neuroscience; Rhesus Macaque; Animal Welfare; Electrophysiology; Sensorimotor; PRR; PMd; M1; Multisensory Integration; Spatial Cognition; Psychophysics