Ipsilateral corticotectal projections from the primary, premotor and supplementary motor cortical areas in adult macaque monkeys: a quantitative anterograde tracing study

Ipsilateral corticotectal projections from the primary, premotor and supplementary motor cortical areas in adult macaque monkey

Corticotectal Projections From the Premotor or Primary Motor Cortex After Cortical Lesion or Parkinsonian Symptoms in Adult Macaque Monkeys: A Pilot Tracing Study

The corticotectal projections, together with the corticobulbar (corticoreticular) projections, work in parallel with the corticospinal tract (CST) to influence motoneurons in the spinal cord both directly and indirectly via the brainstem descending pathways. The tectospinal tract (TST) originates in the deep layers of the superior colliculus. In the present study, we analyzed the corticotectal projections from two motor cortical areas, namely the premotor cortex (PM) and the primary motor cortex (M1) in eight macaque monkeys subjected to either a cortical lesion of the hand area in M1 (n = 4) or Parkinson’s disease-like symptoms PD (n = 4). A subgroup of monkeys with cortical lesion was subjected to anti-Nogo-A antibody treatment whereas all PD monkeys were transplanted with Autologous Neural Cell Ecosystems (ANCEs). The anterograde tracer BDA was used to label the axonal boutons both en passant and terminaux in the ipsilateral superior colliculus. Individual axonal boutons were charted in the different layers of the superior colliculus. In intact animals, we previously observed that corticotectal projections were denser when originating from PM than from M1. In the present M1 lesioned monkeys, as compared to intact ones the corticotectal projection originating from PM was decreased when treated with anti-Nogo-A antibody but not in untreated monkeys. In PD-like symptoms’ monkeys, on the other hand, there was no consistent change affecting the corticotectal projection as compared to intact monkeys. The present pilot study overall suggests that the corticotectal projection is less affected by M1 lesion or PD symptoms than the corticoreticular projection previously reported in the same animals

Assessment of the effect of continuous theta burst stimulation of the motor cortex on manual dexterity in non-human primates in a direct comparison with invasive intracortical pharmacological inactivation

Non-invasive reversible perturbation techniques of brain output such as continuous theta burst stimulation (cTBS), commonly used to modulate cortical excitability in humans, allow investigation of possible roles in functional recovery played by distinct intact cortical areas following stroke. To evaluate the potential of cTBS, the behavioural effects of this non-invasive transient perturbation of the hand representation of the primary motor cortex (M1) in non-human primates (two adult macaques) were compared with an invasive focal transient inactivation based on intracortical microinfusion of GABA-A agonist muscimol. The effects on the contralateral arm produced by cTBS or muscimol were directly compared based on a manual dexterity task performed by the monkeys, the “reach and grasp” drawer task, allowing quantitative assessment of the grip force produced between the thumb and index finger and exerted on the drawer's knob. cTBS only induced modest to moderate behavioural effects, with substantial variability on manual dexterity whereas the intracortical muscimol microinfusion completely impaired manual dexterity, producing a strong and clear cortical inhibition of the M1 hand area. In contrast, cTBS induced mixed inhibitory and facilitatory/excitatory perturbations of M1, though with predominant inhibition. Although cTBS impacted on manual dexterity, its effects appear too limited and variable in order to use it as a reliable proof of cortical vicariation mechanism (cortical area replacing another one) underlying functional recovery following a cortical lesion in the motor control domain, in contrast to potent pharmacological block generated by muscimol infusion, whose application is though limited to an animal model such as non-human primate

Variability of manual dexterity performance in non-human primates (Macaca fascicularis)

The goal of this study was to quantify the inter-individual and intra-individual variability of manual (digits) skill in adult macaque monkeys, over a motor learning phase and, lateron, when motor skills were consolidated. The hypothesis is that several attributes of the stable manual dexterity performance can be predicted from learning characteristics. The behavioral data were collected from 20 adult Macaca fascicularis, derived from their dominant hand, defined as the hand exhibiting a better performance than theother. Two manual dexterity tasks were tested: (i) the modified Brinkman board task, consisting in the retrieval of food pellets placed in 50 slots ina board, using the precision grip (opposition of the thumb and index finger);(ii) the reach and grasp drawer task, in which the grip force and the load force were continuously monitored while the monkey opened a drawer against a resistance, before grasping a pellet inside the drawer. The hypothesis was verified for the performance of manual dexterity after consolidation, correlated with the initial score before learning. Motor habit, reflected by the temporal order of sequential movements executed in the modified Brinkman board task, was established very early during the learning phase. As mostly expected, motor  learning led to an optimization of manual dexterity parameters, such as score, contact time, as well as a decrease in intra-individual variability. Overall,the data demonstrate the substantial inter-individual variability of manual dexterity in non-human primates, to be considered for further pre-clinical applications based on this animal model

Variability of manual dexterity performance in non-human primates ( Macaca fascicularis )

The goal of this study was to quantify the inter-individual and intra-individual variability of manual (digits) skill in adult macaque monkeys, over a motor learning phase and, lateron, when motor skills were consolidated. The hypothesis is that several attributes of the stable manual dexterity performance can be predicted from learning characteristics. The behavioral data were collected from 20 adult Macaca fascicularis, derived from their dominant hand, defined as the hand exhibiting a better performance than theother. Two manual dexterity tasks were tested: (i) the modified Brinkman board task, consisting in the retrieval of food pellets placed in 50 slots ina board, using the precision grip (opposition of the thumb and index finger);(ii) the reach and grasp drawer task, in which the grip force and the load force were continuously monitored while the monkey opened a drawer against a resistance, before grasping a pellet inside the drawer. The hypothesis was verified for the performance of manual dexterity after consolidation, correlated with the initial score before learning. Motor habit, reflected by the temporal order of sequential movements executed in the modified Brinkman board task, was established very early during the learning phase. As mostly expected, motor  learning led to an optimization of manual dexterity parameters, such as score, contact time, as well as a decrease in intra-individual variability. Overall,the data demonstrate the substantial inter-individual variability of manual dexterity in non-human primates, to be considered for further pre-clinical applications based on this animal model