Yakovenko & Drew (2009)

A motor cortical contribution to the anticipatory postural adjustments that precede reaching in the cat.

S Yakovenko, T Drew.

We tested the hypothesis that pyramidal tract neurons (PTNs) in the motor cortex contribute to the anticipatory postural adjustments (APAs) that precede the onset of a reach in the standing cat. We recorded the discharge activity of 151 PTNs in area 4 of the pericruciate cortex during reaches of both the contralateral and the ipsilateral limbs in an instructed delay task. A total of 70/151 PTNs were identified as showing an initial short-latency period of discharge following the Go signal. Linear regression analysis showed that in many of these PTNs the short-latency discharge was time-locked to the Go signal and temporally dissociated from the subsequent voluntary movement of the limb. The onset of the change in activity of most of those Go-related neurons that we could test (62/70) was temporally related to the onset of the change in the center of vertical pressure. In 33/70 PTNs, Go-related activity was observed only during contralateral reach, in 13/70 only during ipsilateral reach, and in 24/70 during movements of each limb; most of these latter cells (20/24) showed nonreciprocal changes in activity. Although 35/151 (23%) cells showed significant changes during the instructed delay period for reaches made with at least one of the limbs, only one neuron showed a significant reciprocal change during reaches with either limb. We suggest that the discharge characteristics of these PTNs are compatible with our hypothesis that the motor cortex contributes to the production of the APAs preceding movement. - J Neurophysiol (2009) vol. 102 (2) pp. 853-74

Sinkjaer et al (1995)

Synaptic linkages between red nucleus cells and limb muscles during a multi-joint motor task.

T Sinkjær, L Miller, T Andersen, JC Houk.

Exp Brain Res (1995) 102:546-550

Van Kan & McCurdy (2002)

Contribution of primate magnocellular red nucleus to timing of hand preshaping during reaching to grasp.

PL Van Kan, ML McCurdy.

Magnocellular red nucleus (RNm) is involved in controlling goal-directed limb movements such as reaching to grasp. We tested two hypotheses related to RNm's role in controlling reach-to-grasp movements. One hypothesis is that forelimb RNm neurons are grasp specific, and the other is that they specify the timing of metacarpi-phalangeal (MCP) extension to preshape the hand during the appropriate phase of the reach. We recorded single-unit discharge while monkeys performed two behavioral tasks that elicited similar reaches but differed in grasp. One task consisted of a reach with a precision grasp that elicited independent use of thumb and forefinger; the other included a whole-hand grasp that elicited concerted use of the four fingers. Most RNm neurons tested were engaged strongly during both the whole-hand and precision tasks, and the magnitude of discharge modulation did not differ between tasks. Thus most RNm neurons are not grasp specific but, instead, may contribute to behavioral features common to the two tasks. Two methods were used to investigate relations between single-unit discharge and kinematic data from the same individual trials of the whole-hand and precision tasks for a subset of forelimb RNm neurons. One method focused on correlations between parameters of RNm discharge and the duration, amplitude, and velocity of rotation of forelimb joints for each of the tasks. The second method compared between-task differences in times of peak neuronal discharge to between-task differences in times of rotations of forelimb joints. Parameters of reach-related RNm discharge were more frequently correlated with parameters of MCP extension than with parameters of rotation of wrist, elbow, and shoulder joints. Analyses of temporal relations between discharge and kinematic data during both the whole-hand and precision tasks indicate that discharge was time locked most frequently to MCP extension and, to a lesser extent, elbow extension during both tasks. We conclude that RNm may command muscle synergies that provide a basic preshape of the hand at the appropriate phase of limb transport. In addition, the timing of RNm's contribution to hand preshaping varies with the behavioral requirements of the task. - J Neurophysiol (2002) vol. 87 (3) pp. 1473-87

Gibson et al. (1985)

Magnocellular red nucleus activity during different types of limb movement in the macaque monkey.

AR Gibson, JC Houk, NJ Kohlerman.

Three hundred and thirty-four neurones located in the magnocellular division of red nucleus (r.n.m.) were studied in three alert macaque monkeys. These cells had low discharge rates at rest and produced high frequency bursts during movement. Single cells were selectively active for movement of one body part, and a motor somatotopy was evident. From dorsal to ventral we encountered cells related to movements of the face, contralateral upper limb, contralateral lower limb and, in one case, the tail. Free-form tests indicated that 76% of upper-limb cells were preferentially related to hand and finger movements, and 84% of lower limb cells were preferentially related to foot and toe movements. Quantitative tests of movement relations were based on depths of modulation in discharge rate recorded while the monkeys operated several devices that served as manipulanda in a tracking task; each device elicited a different movement. We conducted 220 tests on eighty-one cells using eleven devices. The modulation in discharge rate exceeded a 50 pulses/s criterion level in seventy-nine cases; eleven were well related to proximal movements, twenty-two to movements of the digits and forty-six to a co-ordinated hand movement elicited by a device called the twister. Both unidirectional and bidirectional patterns of bursting were frequent. A few cells showed reciprocal patterns consisting of a large increase in rate for one direction of movement and a small decrease for the other. The bursts in discharge preceded movement onset (97% of 132 cases) by an average of 135 ms. Electromyographic activity in forearm muscles preceded movement by about 55 ms. In some cases we recorded from a single cell while the monkey operated two, three or four devices. Depth of modulation on the twister device was twice that on a proximal device in nine cases whereas one case showed a proximal device preference; five cases showed overlap. Comparison between twister and digits yielded ten cases of twister preference, four of digit preference and twenty cases of overlap. A directional preference was found for ten out of eleven cells responsive during active movement restricted to the metacarpo-phalangeal joints, and in all cases the preferred direction was extension. Responses to natural somatosensory stimulation were weak or absent for the majority of cells. When present, sensory fields were confined to the same limb but were frequently out of register with motor fields.(ABSTRACT TRUNCATED AT 400 WORDS) - J Physiol (Lond) (1985) vol. 358 pp. 527-49

http://jp.physoc.org/content/358/1/527.long