Information Technology Reference
In-Depth Information
after 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) injection. A reduction
in the number of reciprocally organized cells (neurons showing a reciprocal dis-
charge pattern for flexion and extension movements; 49% in the pre-MPTP state and
18% in the post-MPTP state) and an increase in the number of unidirectional cells
(cells whose activities change in only one direction; 19% in the pre-MPTP state and
50% in the post-MPTP state) without an alteration of the overall excitation were re-
ported. It was suggested that there was a lift of inhibition from cells that are normally
inhibited during movement resulting in an extra-imposed load on the limb [23].
11.5.2 Reduction of Neuronal Intensity and of Rate
of Development of Neuronal Discharge in the Primary
Motor Cortex
Watts and Mandir [50] examined the effects of MPTP-induced Parkinsonism on the
primary motor cortex task-related neuronal activity and motor behavior of monkeys.
Two monkeys were trained in the pre-MPTP state with the help of visual cues, deliv-
ered via a panel of light-emitting diodes (LEDs), to make fast, wrist flexion move-
ments of 60. Once the animals were fully trained on the task and the M1 neuronal
and EMG activities were recorded, intracarotid injection of MPTP was administered
to induce a stable state of Parkinsonism. Single neuronal recordings were repeated
during the experimentally induced Parkinsonian state for many months. They re-
ported a decrease in the percentage of movement onset-related neurons and an in-
crease in the latency between the start of M1 neuronal activity and the movement
onset and in the duration of after-discharge following movement onset in the hemi-
Parkinsonian state.
Similarly, Gross and colleagues [36] trained monkeys to perform a rapid elbow
movement (
30) of extension or flexion in response to an auditory signal. The
unit activity of the primary motor cortical cells was recorded 500 ms before and
1,500 ms after the beginning of the auditory signal, before and after an electrolytic
lesion of the substantia nigra pars compacta (SNc). They reported that the maximum
discharge frequency in lesioned animals was lower than in normal animals.
Doudet and colleagues [23] observed a similar change in discharge rate of pri-
mary motor cortical cells as well as a prolongation of their total response duration.
They reported that the time between the start of the alterations in the neuronal dis-
charge and the onset of movement was increased by 20%.
>
11.5.3 Significant Increase in Mean Duration of Neuronal
Discharge in Primary Motor Cortex Preceding and
Following Onset of Movement
In the experimental paradigm described earlier, Gross and colleagues [36] observed
that the latency between the onset of neuronal discharge and the beginning of fore-
Search WWH ::




Custom Search