Limits...
Cortical output to fast and slow muscles of the ankle in the rhesus macaque.

Hudson HM, Griffin DM, Belhaj-Saïf A, Cheney PD - Front Neural Circuits (2013)

Bottom Line: Although it is generally agreed that cortical stimulation yields short latency facilitation of fast muscles, the effects on the slow muscle, soleus, remain controversial.However, while poststimulus suppression (PStS) was observed in all muscles, it was more common in the slow muscle compared to the fast muscles and was as common as facilitation at low stimulus intensities.Overall, our results demonstrate that cortical facilitation of soleus has an organization that is very similar to that of the fast ankle muscles.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City KS, USA.

ABSTRACT
The cortical control of fast and slow muscles of the ankle has been the subject of numerous reports yielding conflicting results. Although it is generally agreed that cortical stimulation yields short latency facilitation of fast muscles, the effects on the slow muscle, soleus, remain controversial. Some studies have shown predominant facilitation of soleus from the cortex while others have provided evidence of differential control in which soleus is predominantly inhibited from the cortex. The objective of this study was to investigate the cortical control of fast and slow muscles of the ankle using stimulus triggered averaging (StTA) of EMG activity, which is a sensitive method of detecting output effects on muscle activity. This method also has relatively high spatial resolution and can be applied in awake, behaving subjects. Two rhesus macaques were trained to perform a hindlimb push-pull task. Stimulus triggered averages (StTAs) of EMG activity (15, 30, and 60 μA at 15 Hz) were computed for four muscles of the ankle [tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus] as the monkeys performed the task. Poststimulus facilitation (PStF) was observed in both the fast muscles (TA, MG, and LG) as well as the slow muscle (soleus) and was as common and as strong in soleus as in the fast muscles. However, while poststimulus suppression (PStS) was observed in all muscles, it was more common in the slow muscle compared to the fast muscles and was as common as facilitation at low stimulus intensities. Overall, our results demonstrate that cortical facilitation of soleus has an organization that is very similar to that of the fast ankle muscles. However, cortical inhibition is organized differently allowing for more prominent suppression of soleus motoneurons.

Show MeSH

Related in: MedlinePlus

Maps of individual ankle muscle representations in hindlimb primary motor cortex in two monkeys (F and C), represented in two dimensions after unfolding the medial wall and central sulcus. Maps of hindlimb muscles were based on PStF effects at 15, 30, and 60 μA. Heavy horizontal black line: midline, above the heavy black line represents the bank of the medial wall of the hemisphere. Solid black curved line: central sulcus. Dotted black curved line: fundus of the central sulcus. A, anterior; P, posterior; M, medial; and L, lateral. Muscle abbreviations are the same as in Figure 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3585439&req=5

Figure 6: Maps of individual ankle muscle representations in hindlimb primary motor cortex in two monkeys (F and C), represented in two dimensions after unfolding the medial wall and central sulcus. Maps of hindlimb muscles were based on PStF effects at 15, 30, and 60 μA. Heavy horizontal black line: midline, above the heavy black line represents the bank of the medial wall of the hemisphere. Solid black curved line: central sulcus. Dotted black curved line: fundus of the central sulcus. A, anterior; P, posterior; M, medial; and L, lateral. Muscle abbreviations are the same as in Figure 1.

Mentions: Figure 6 shows the representation of each muscle in M1 of both monkeys based on PStF effects. All muscles were represented in both monkeys. There was massive overlap in the territories for each muscle, not only of the extensors (MG, LG, and SOL) but also of the flexor muscle, TA. While monkey F had considerably fewer effects than monkey C, the same trends were apparent in both monkeys.


Cortical output to fast and slow muscles of the ankle in the rhesus macaque.

Hudson HM, Griffin DM, Belhaj-Saïf A, Cheney PD - Front Neural Circuits (2013)

Maps of individual ankle muscle representations in hindlimb primary motor cortex in two monkeys (F and C), represented in two dimensions after unfolding the medial wall and central sulcus. Maps of hindlimb muscles were based on PStF effects at 15, 30, and 60 μA. Heavy horizontal black line: midline, above the heavy black line represents the bank of the medial wall of the hemisphere. Solid black curved line: central sulcus. Dotted black curved line: fundus of the central sulcus. A, anterior; P, posterior; M, medial; and L, lateral. Muscle abbreviations are the same as in Figure 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3585439&req=5

Figure 6: Maps of individual ankle muscle representations in hindlimb primary motor cortex in two monkeys (F and C), represented in two dimensions after unfolding the medial wall and central sulcus. Maps of hindlimb muscles were based on PStF effects at 15, 30, and 60 μA. Heavy horizontal black line: midline, above the heavy black line represents the bank of the medial wall of the hemisphere. Solid black curved line: central sulcus. Dotted black curved line: fundus of the central sulcus. A, anterior; P, posterior; M, medial; and L, lateral. Muscle abbreviations are the same as in Figure 1.
Mentions: Figure 6 shows the representation of each muscle in M1 of both monkeys based on PStF effects. All muscles were represented in both monkeys. There was massive overlap in the territories for each muscle, not only of the extensors (MG, LG, and SOL) but also of the flexor muscle, TA. While monkey F had considerably fewer effects than monkey C, the same trends were apparent in both monkeys.

Bottom Line: Although it is generally agreed that cortical stimulation yields short latency facilitation of fast muscles, the effects on the slow muscle, soleus, remain controversial.However, while poststimulus suppression (PStS) was observed in all muscles, it was more common in the slow muscle compared to the fast muscles and was as common as facilitation at low stimulus intensities.Overall, our results demonstrate that cortical facilitation of soleus has an organization that is very similar to that of the fast ankle muscles.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City KS, USA.

ABSTRACT
The cortical control of fast and slow muscles of the ankle has been the subject of numerous reports yielding conflicting results. Although it is generally agreed that cortical stimulation yields short latency facilitation of fast muscles, the effects on the slow muscle, soleus, remain controversial. Some studies have shown predominant facilitation of soleus from the cortex while others have provided evidence of differential control in which soleus is predominantly inhibited from the cortex. The objective of this study was to investigate the cortical control of fast and slow muscles of the ankle using stimulus triggered averaging (StTA) of EMG activity, which is a sensitive method of detecting output effects on muscle activity. This method also has relatively high spatial resolution and can be applied in awake, behaving subjects. Two rhesus macaques were trained to perform a hindlimb push-pull task. Stimulus triggered averages (StTAs) of EMG activity (15, 30, and 60 μA at 15 Hz) were computed for four muscles of the ankle [tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus] as the monkeys performed the task. Poststimulus facilitation (PStF) was observed in both the fast muscles (TA, MG, and LG) as well as the slow muscle (soleus) and was as common and as strong in soleus as in the fast muscles. However, while poststimulus suppression (PStS) was observed in all muscles, it was more common in the slow muscle compared to the fast muscles and was as common as facilitation at low stimulus intensities. Overall, our results demonstrate that cortical facilitation of soleus has an organization that is very similar to that of the fast ankle muscles. However, cortical inhibition is organized differently allowing for more prominent suppression of soleus motoneurons.

Show MeSH
Related in: MedlinePlus