Aging reduces surround suppression effects in a perceived speed task

It has been hypothesized that the magnocellular red nucleus (RNm) contributes to compensation for motor impairments associated with lesions of the pyramidal tract. To test this hypothesis, we used stimulus triggered averaging (StTA) of electromyographic (EMG) activity to characterize changes in motor output from the red nucleus after lesions of the pyramidal tract. Three monkeys were trained to perform a reach and prehension task. EMG activity was recorded from 11 forearm muscles including one elbow, five wrist, and five digit muscles. Microstimulation (20 μA at 20 Hz) was delivered throughout the movement task to compute StTAs. Two monkeys served as controls. In a third monkey, 65% of the left pyramidal tract had been destroyed by an electrolytic lesion method five years before recording. The results demonstrate a clear pattern of postlesion reorganization in red nucleus–mediated output effects on forearm muscles. The normally prominent extensor preference in excitatory output from the RNm (92% in extensors) was greatly diminished in the lesioned monkey (59%). Similarly, suppression effects, which are normally much more prominent in flexor than in extensor muscles (90% in flexors), were also more evenly distributed after recovery from pyramidal tract lesions. Because of the limited excitatory output from the RNm to flexor muscles that normally exists, loss of corticospinal output would leave control of flexors particularly weak. The changes in RNm organization reported in this study would help restore function to flexor muscles. These results support the hypothesis that the RNm is capable of reorganization that contributes to the recovery of forelimb motor function after pyramidal tract lesions.

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Does Cortical Inhibition Explain the Correlation Between Bistable Perception Paradigms?

i-Perception ◽

10.1177/20416695211020018 ◽

2021 ◽

Vol 12 (3) ◽

pp. 204166952110200

Author(s):

Abhilasha R. Jagtap ◽

Jan W. Brascamp

Keyword(s):

Binocular Rivalry ◽

Mediation Analysis ◽

Cortical Inhibition ◽

Behavioral Measure ◽

Observer Variability ◽

Surround Suppression ◽

Bistable Perception ◽

Visual Hierarchy ◽

Neural Inhibition ◽

Mediating Factor

When observers view a perceptually bistable stimulus, their perception changes stochastically. Various studies have shown across-observer correlations in the percept durations for different bistable stimuli including binocular rivalry stimuli and bistable moving plaids. Previous work on binocular rivalry posits that neural inhibition in the visual hierarchy is a factor involved in the perceptual fluctuations in that paradigm. Here, in order to investigate whether between-observer variability in cortical inhibition underlies correlated percept durations between binocular rivalry and bistable moving plaid perception, we used center-surround suppression as a behavioral measure of cortical inhibition. We recruited 217 participants in a test battery that included bistable perception paradigms as well as a center-surround suppression paradigm. While we were able to successfully replicate the correlations between binocular rivalry and bistable moving plaid perception, we did not find a correlation between center-surround suppression strength and percept durations for any form of bistable perception. Moreover, the results from a mediation analysis indicate that center-surround suppression is not the mediating factor in the correlation between binocular rivalry and bistable moving plaids. These results do not support the idea that cortical inhibition can explain the between-observer correlation in mean percept duration between binocular rivalry and bistable moving plaid perception.

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Highly enhanced upconversion luminescence in lanthanide-doped active-core/luminescent-shell/active-shell nanoarchitectures

Journal of Materials Chemistry C ◽

10.1039/c6tc00163g ◽

2016 ◽

Vol 4 (13) ◽

pp. 2432-2437 ◽

Cited By ~ 39

Author(s):

Mingye Ding ◽

Daqin Chen ◽

Danyang Ma ◽

Jianbin Dai ◽

Yuting Li ◽

...

Keyword(s):

Emission Intensity ◽

Upconversion Luminescence ◽

Synergistic Action ◽

Significant Enhancement ◽

Active Core ◽

Suppression Effects

Through active-core/luminescent-shell/active-shell engineering in lanthanide-doped fluoride nanocrystals, significant enhancement of UC emission intensity has been successfully realized under the synergistic action of double sensitization and suppression effects.

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