Occlusion of LTP-Like Plasticity in Human Primary Motor Cortex by Action Observation

Passive observation of motor actions induces cortical activity in the primary motor cortex (M1) of the onlooker, which could potentially contribute to motor learning. While recent studies report modulation of motor performance following action observation, the neurophysiological mechanism supporting these behavioral changes remains to be specifically defined. Here, we assessed whether the observation of a repetitive thumb movement – similarly to active motor practice – would inhibit subsequent long-term potentiation-like (LTP) plasticity induced by paired-associative stimulation (PAS). Before undergoing PAS, participants were asked to either 1) perform abductions of the right thumb as fast as possible; 2) passively observe someone else perform thumb abductions; or 3) passively observe a moving dot mimicking thumb movements. Motor evoked potentials (MEP) were used to assess cortical excitability before and after motor practice (or observation) and at two time points following PAS. Results show that, similarly to participants in the motor practice group, individuals observing repeated motor actions showed marked inhibition of PAS-induced LTP, while the “moving dot” group displayed the expected increase in MEP amplitude, despite differences in baseline excitability. Interestingly, LTP occlusion in the action-observation group was present even if no increase in cortical excitability or movement speed was observed following observation. These results suggest that mere observation of repeated hand actions is sufficient to induce LTP, despite the absence of motor learning

The triple helix: 50 years later, the outcome

Triplex-forming oligonucleotides constitute an interesting DNA sequence-specific tool that can be used to target cleaving or cross-linking agents, transcription factors or nucleases to a chosen site on the DNA. They are not only used as biotechnological tools but also to induce modifications on DNA with the aim to control gene expression, such as by site-directed mutagenesis or DNA recombination. Here, we report the state of art of the triplex-based anti-gene strategy 50 years after the discovery of such a structure, and we show the importance of the actual applications and the main challenges that we still have ahead of us

Raw MEP values (mV). Data are presented as mean and SD.

<p>Raw MEP values (mV). Data are presented as mean and SD.</p

Corticospinal excitability before (black) and after (white) observation of moving dots, observation of thumb movements, or execution of thumb movements.

<p>Bars indicate standard error of the mean.</p

Interaction between observation of moving dots, observation of thumb movements and execution of thumb movements with PAS.

<p>Data are expressed as a percent change from pre-PAS values (T2) immediately (T3) and ten minutes (T4) after the end of PAS. Bars indicate standard error of the mean. * p<0.01.</p

Speed of fastes thumb abduction before (T1, black) and after (T2, white) observation of moving dots, observation of thumb movements, or execution of thumb movements.

<p>Bars indicate standard error of the mean. * p<0.05.</p