How Somatotopic Is the Motor Cortex Hand Area?

Schieber, Marc H.; Hibbard, Lyndon S.

doi:10.1126/science.8332915

Cited by 412 publications

(274 citation statements)

References 26 publications

Supporting

Mentioning

245

Contrasting

Unclassified

Order By: Relevance

“…As opposed to the traditional somatotopically ordered representational map for muscles outputs (Penfield and Rasmussen 1950;Woolsey et al 1992), current data reveal that the internal organization of each body part is best described as a network having broadly distributed functions (Sanes and Donoghue 1997). Each neuron within M1 appears to participate in the projection to multiple muscles (Buys et al 1986;Fetz et al 1989) and motor actions (Schieber and Hibbard 1993). Evidence of this notion has been obtained not only from neural recordings and intracortical electrical stimulation, but also from pharmacological inactivation, connectional studies, and neuroimaging studies (Sanes and Donoghue 2000).…”

Section: Discussionmentioning

confidence: 99%

Motor Facilitation While Observing Hand Actions: Specificity of the Effect and Role of Observer's Orientation

Maeda

Kleiner‐Fisman

Pascual‐Leone

2002

Journal of Neurophysiology

366

219

View full text Add to dashboard Cite

Maeda, Fumiko, Galit Kleiner-Fisman, and Alvaro Pascual-Leone. Motor facilitation while observing hand actions: specificity of the effect and role of observer's orientation. J Neurophysiol 87: 1329 -1335, 2002; 10.1152/jn.00773.2000. Action observation enhances cortico-spinal excitability. Here we tested the specificity of this effect and the role played by the orientation of the observer. Ten normal subjects observed video clips of right hand performing three different finger movements (thumb ab-/adduction, index ab-/adduction, index extens-/flexion) in two different orientations (Away, i.e., natural hand-orientation facing out from the observer; or Toward, i.e., unnatural hand-orientation facing toward the observer). Motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) were recorded from the abductor pollicis brevis (APB) and the first dorsal interosseus (FDI) muscles. Movement direction of the index finger was recorded using force transducers. Facilitation of MEP size was significantly greater for APB during observation of thumb movements and for FDI during observation of index finger movements. Facilitation of MEP size was significantly greater when the hand presented on screen was facing out from and corresponding to that of the observer (Away orientation). The direction of the index finger movement evoked by TMS shifted toward extension/flexion versus ab-/adduction matching the observed movement. Our results give further evidence that observation of a movement enhances motor output to the muscles involved in the movement and facilitates the observed action. In addition, we provide novel evidence about the high degree of specificity of this observation-induced motor cortical modulation. The degree of modulation depends on hand orientation. The modulation is maximal when the observed action corresponds to the orientation of the observer.

show abstract

Section: Discussionmentioning

confidence: 99%

Motor Facilitation While Observing Hand Actions: Specificity of the Effect and Role of Observer's Orientation

Maeda

Kleiner‐Fisman

Pascual‐Leone

2002

Journal of Neurophysiology

366

219

View full text Add to dashboard Cite

show abstract

“…The increment in slave fingers could be ascribed to the complex and unique organization of the human hand in M1. Each finger has multiple representations in M1 that are highly interconnected (Schieber and Hibbard 1993). A single-finger movement could lead to activation of representations distributed throughout the M1 hand area (Porter and Lemon 1993;Schieber 1999).…”

Section: Discussionmentioning

confidence: 99%

“…Another study by ) extended this finding and showed that subjects were able to distinguish one-vs. four-finger imagined force production tasks. Given the existence of multiple finger representations that are highly interconnected in the motor cortex (Schieber and Hibbard 1993), the ability to imagine individual finger movements suggests that neural centers and motor pathways are specifically activated during motor imagery. These studies lead to an alternative hypothesis of specific involvement (cf.…”

Section: Introductionmentioning

confidence: 99%

Movement-specific enhancement of corticospinal excitability at subthreshold levels during motor imagery

2006

Exp Brain Res

View full text Add to dashboard Cite

This study examined modulation of corticospinal excitability during both actual and imagined movements. Seven young healthy subjects performed actual (3% to 50% maximal voluntary contraction) and imagined index finger force production, and rest. Individual responses to focal transcranial magnetic stimulation (TMS) in four fingers (index, middle, ring, and little) were recorded for all three tested conditions. The force increments at the threshold of activation were derived from regression analysis, representing the TMS-induced response at the threshold activation of the corticospinal pathways. The increment in the index finger during motor imagery was larger than that at rest, but smaller than that at the threshold of activation. On the other hand, the increment in the uninstructed (middle, ring and little), slave fingers during motor imagery was larger than that at rest, but not different from that at the threshold of activation. These contrasting results suggest that the degree of imagery-induced enhancement in corticospinal excitability was significantly less than what could be predicted for threshold levels from regression analysis, but only for the index finger, and not the adjacent slave fingers. It is concluded that corticospinal excitability for the explicitly instructed index finger is specifically enhanced at subthreshold levels during motor imagery.

show abstract

“…We showed that multijoint synergies begin to be encoded in motor cortex by 10 weeks in the cat (Chakrabarty and Martin, 2000), which is when facilitation is well developed. Single-unit and mapping experiments in mature motor cortex have revealed territories containing neurons that control multiple digits during manipulation (Schieber and Hibbard, 1993) and multiple forelimb joints dur- ing reaching (Georgopoulos et al, 1982). During postnatal development, the amount of facilitation could thus be a critical determinant of the degree and pattern of control the CS system is able to exert over limb movements.…”

Section: The Transition To Corticospinal Motor Control Functionsmentioning

confidence: 99%

The Transition from Development to Motor Control Function in the Corticospinal System

Meng¹,

Li²,

Martin³

2004

J. Neurosci.

View full text Add to dashboard Cite

During early postnatal development, corticospinal (CS) system stimulation, electrical or transcranial magnetic, is minimally effective in producing muscle contraction, despite having axon terminals that excite spinal neurons. Later, after stimulation becomes more effective, the cortical motor representation develops, and movements the system controls in maturity are expressed. We determined whether development of temporal facilitation (response enhancement produced by the second of a pair of pyramidal tract stimuli, or a higher stimulus multiple of a train of stimuli) correlated with these changes. Facilitation of the monosynaptic CS response was larger in older kittens and adults than younger kittens. When facilitation was strong, strong motor responses were evoked by pyramidal stimulation with small currents and few pulses. With strong facilitation in older kittens, corticospinal axon varicosities colocalize synaptophysin like adults, suggesting a presynaptic mechanism. With effective facilitation, control signals from the cortex can be sufficiently effective to provoke muscle contraction for guiding movements.

show abstract

How Somatotopic Is the Motor Cortex Hand Area?

Cited by 412 publications

References 26 publications

Motor Facilitation While Observing Hand Actions: Specificity of the Effect and Role of Observer's Orientation

Motor Facilitation While Observing Hand Actions: Specificity of the Effect and Role of Observer's Orientation

Movement-specific enhancement of corticospinal excitability at subthreshold levels during motor imagery

The Transition from Development to Motor Control Function in the Corticospinal System

Contact Info

Product

Resources

About