Bidirectional control of a one-dimensional robotic actuator by operant conditioning of a single unit in rat motor cortex

AbstractObjectiveBrain-machine interfaces (BMIs) are promising candidates for restoring the lost motor system functions. Center-out reaching task is a commonly used BMI control paradigm in humans and monkeys and has not been available for rodents yet. In this work, our goal was to develop a behavioral paradigm which enables rats to control a neuroprosthesis in a center-out reaching task applied in one-dimensional space.ApproachThe experimental setup mainly consisted of a behavioral cage and a robotic workspace outside the cage. Two distant targets were located on the left and right sides of the central starting position of the robot endpoint. An online transform algorithm was used to convert the activity of a pair of recorded primary motor cortex units into two robotic actions. An increase in the activity of one of the units directed the robot endpoint toward left while an increase in the other moved it toward right. The task difficulty level which was proportional to the distance between the selected target and the initial position of the robot endpoint at the beginning of trials was increased gradually as the rat adapts with the transform.Main ResultsAll three rats involved in the study were capable of achieving randomly selected targets with at least 78% accuracy in the highest task difficulty level, in center-out reaching task. A total of 9 out of 16 pairs of units examined were eligible for training in center-out reaching task. Two out of three rats were capable of reversal learning where the mapping between the activity of the unit pairs and the robotic actions were reversed.SignificanceThe present behavioral paradigm enabled freely moving rats to control a robotic arm through primary motor cortex neurons in a one-dimensional center-out reaching task. It may offer a cost-effective alternative for the BMI studies requiring one-dimensional, bidirectional neuroprosthetic actions.

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Single-unit activity, threshold crossings, and local field potentials in motor cortex differentially encode reach kinematics

Journal of Neurophysiology ◽

10.1152/jn.00293.2014 ◽

2015 ◽

Vol 114 (3) ◽

pp. 1500-1512 ◽

Cited By ~ 29

Author(s):

Sagi Perel ◽

Patrick T. Sadtler ◽

Emily R. Oby ◽

Stephen I. Ryu ◽

Elizabeth C. Tyler-Kabara ◽

...

Keyword(s):

Motor Cortex ◽

Local Field ◽

Unit Activity ◽

Single Unit ◽

Primary Motor Cortex ◽

Spatial Scales ◽

Local Field Potentials ◽

Single Unit Activity ◽

Field Potentials ◽

Threshold Crossing

A diversity of signals can be recorded with extracellular electrodes. It remains unclear whether different signal types convey similar or different information and whether they capture the same or different underlying neural phenomena. Some researchers focus on spiking activity, while others examine local field potentials, and still others posit that these are fundamentally the same signals. We examined the similarities and differences in the information contained in four signal types recorded simultaneously from multielectrode arrays implanted in primary motor cortex: well-isolated action potentials from putative single units, multiunit threshold crossings, and local field potentials (LFPs) at two distinct frequency bands. We quantified the tuning of these signal types to kinematic parameters of reaching movements. We found 1) threshold crossing activity is not a proxy for single-unit activity; 2) when examined on individual electrodes, threshold crossing activity more closely resembles LFP activity at frequencies between 100 and 300 Hz than it does single-unit activity; 3) when examined across multiple electrodes, threshold crossing activity and LFP integrate neural activity at different spatial scales; and 4) LFP power in the “beta band” (between 10 and 40 Hz) is a reliable indicator of movement onset but does not encode kinematic features on an instant-by-instant basis. These results show that the diverse signals recorded from extracellular electrodes provide somewhat distinct and complementary information. It may be that these signal types arise from biological phenomena that are partially distinct. These results also have practical implications for harnessing richer signals to improve brain-machine interface control.

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Cortical neural modulation by previous trial outcome differentiates fast- from slow-learning rats on a visuomotor directional choice task

Journal of Neurophysiology ◽

10.1152/jn.00950.2016 ◽

2019 ◽

Vol 121 (1) ◽

pp. 50-60 ◽

Cited By ~ 1

Author(s):

Hongwei Mao ◽

Yuan Yuan ◽

Jennie Si

Keyword(s):

Motor Cortex ◽

Neural Activity ◽

Single Unit ◽

Choice Task ◽

Learning Rate ◽

Previous Trial ◽

Behavioral Differences ◽

Slow Learners ◽

Trial Outcome ◽

Neural Modulation

To better understand the neural cortical underpinnings that explain behavioral differences in learning rate, we recorded single-unit activity in primary motor (M1) and secondary motor (M2) areas while rats learned to perform a directional (left or right) operant visuomotor association task. Analysis of neural activity during the early portion of the cue period showed that neural modulation in the motor cortex was most strongly associated with two task factors: the previous trial outcome (success or error) and the current trial’s directional choice (left or right). Furthermore, the fast learners, defined as those who had steeper learning curves and required fewer learning sessions to reach criterion performance, encoded the previous trial outcome factor more strongly than the directional choice factor. Conversely, the slow learners encoded directional choice more strongly than previous trial outcome. These differences in task factor encoding were observed in both the percentage of neurons and the neural modulation depth. These results suggest that fast learning is accompanied by a stronger component of previous trial outcome in the modulation representation present in motor cortex, which therefore may be a contributing factor to behavioral differences in learning rate. NEW & NOTEWORTHY We chronically recorded neural activity as rats learned a visuomotor directional choice task from a naive state. Learning rates varied. Single-unit neural modulation of two motor areas revealed that the fast learners encoded previous trial outcome more strongly than directional choice, whereas the reverse was true for slow learners. This finding provides novel evidence that rat learning rate is strongly correlated with the strength of neural modulation by previous trial outcome in motor cortex.

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