Sensory and motor representations of internalized rhythms in the cerebellum and basal ganglia

The Relationship Between Physical Activity and Gait Rhythm with Motor Imagery -Trial Using the Finger Tap Test

OBJECTIVES

The purpose of this study was to investigate the relationship of any error (delta; ∆) between the image of one's own walking rhythm and the actual walking rhythm and physical activity, as a new motor imagery assessment.

METHODS

The subjects were classified into two groups: a high activity group (HA-Group) having high physical activity with less than four hours of sitting time per day, and a low activity group (LA-Group) having low physical activity with more than four hours of daily sitting time. Visual rhythm, auditory rhythm, mental comfortable walking rhythm, and mental maximum walking rhythm were used to assess new motor imagery. Their beats per minute were measured and any error (delta; ∆) from the actual rhythm was calculated: ∆ visual rhythm, ∆ auditory rhythm, ∆ mental normal gait rhythm, and ∆ mental maximal gait rhythm.

RESULTS

When comparing the two groups, the HA-Group had significantly higher ∆ visual rhythm, lower ∆ auditory rhythm, higher ∆ mental comfortable walking rhythm, and lower ∆ mental maximum walking rhythm ability than the LA-Group. Furthermore, in an ANCOVA with age, ∆visual rhythm, and ∆auditory rhythm as adjustment factors, the HA-Group had significantly lower ∆mental maximum walking rhythm than the LA-Group.

CONCLUSIONS

These results showed that the rhythmic assessment of the imagery of maximum walking was associated with stationery time. It is possible that the more inaccurate the imagery of maximum walking, the longer the sitting or lying time.

Histamine Modulation of the Basal Ganglia Circuitry in the Motor Symptoms of Parkinson's Disease

PURPOSE OF REVIEW

Parkinson's disease (PD) is characterized by dopaminergic system dysfunction that results from the degeneration of neurons in the substantia nigra. However, studies suggest that other neurotransmitters, especially histamine, may also play a role in the development of PD.

RECENT FINDINGS

Numerous studies show that histamine levels in the basal ganglia significantly change in PD pathology, correlating with motor symptoms observed in animal models of PD. Histamine activates H1R or H4R on microglia in the substantia nigra, triggering an inflammatory response and promoting dopaminergic neuron degeneration. Additionally, histamine modulates neuronal excitability and firing activity (firing rate and pattern) by activating H1R, H2R, or H3R on neurons in the basal ganglia nucleus, ultimately impacting normal motor behavior as well as motor symptoms in models of PD.

SUMMARY

This review presents the role of histamine and its receptor ligands in the basal ganglia nuclei, along with downstream ion channels linked to histamine receptors that influence immune response, neuronal excitability, and firing activity in PD. It highlights their effects on neuronal firing and their connection to PD motor symptoms. Investigating new ligands targeting basal ganglia histamine receptors and associated ion channels may facilitate the development of novel treatments for PD.

Neurobiological mechanism of music improving gait disorder in patients with Parkinson's disease: a mini review

Walking ability is essential for human survival and health. Its basic rhythm is mainly generated by the central pattern generator of the spinal cord. The rhythmic stimulation of music to the auditory center affects the cerebral cortex and other higher nerve centers, and acts on the central pattern generator. By means of rhythm entrainment, the central pattern generator can produce walking rhythm synchronized with music rhythm, control muscle tension, and then regulate human gait. Basal ganglia dysfunction is the main cause of abnormal gait in patients with Parkinson's disease. Music therapy provides external rhythmic stimulation, recruits neural networks to bypass the basal ganglia and synchronizes gait with external rhythms in both time and space through auditory-motor neural networks, helping to promote the improvement of abnormal gait patterns in patients with Parkinson's disease.

Organization of reward and movement signals in the basal ganglia and cerebellum

The basal ganglia and the cerebellum are major subcortical structures in the motor system. The basal ganglia have been cast as the reward center of the motor system, whereas the cerebellum is thought to be involved in adjusting sensorimotor parameters. Recent findings of reward signals in the cerebellum have challenged this dichotomous view. To compare the basal ganglia and the cerebellum directly, we recorded from oculomotor regions in both structures from the same monkeys. We partitioned the trial-by-trial variability of the neurons into reward and eye-movement signals to compare the coding across structures. Reward expectation and movement signals were the most pronounced in the output structure of the basal ganglia, intermediate in the cerebellum, and the smallest in the input structure of the basal ganglia. These findings suggest that reward and movement information is sharpened through the basal ganglia, resulting in a higher signal-to-noise ratio than in the cerebellum.

Temporal Information Processing in the Cerebellum and Basal Ganglia

Temporal information processing in the range of a few hundred milliseconds to seconds involves the cerebellum and basal ganglia. In this chapter, we present recent studies on nonhuman primates. In the studies presented in the first half of the chapter, monkeys were trained to make eye movements when a certain amount of time had elapsed since the onset of the visual cue (time production task). The animals had to report time lapses ranging from several hundred milliseconds to a few seconds based on the color of the fixation point. In this task, the saccade latency varied with the time length to be measured and showed stochastic variability from one trial to the other. Trial-to-trial variability under the same conditions correlated well with pupil diameter and the preparatory activity in the deep cerebellar nuclei and the motor thalamus. Inactivation of these brain regions delayed saccades when asked to report subsecond intervals. These results suggest that the internal state, which changes with each trial, may cause fluctuations in cerebellar neuronal activity, thereby producing variations in self-timing. When measuring different time intervals, the preparatory activity in the cerebellum always begins approximately 500 ms before movements, regardless of the length of the time interval being measured. However, the preparatory activity in the striatum persists throughout the mandatory delay period, which can be up to 2 s, with different rate of increasing activity. Furthermore, in the striatum, the visual response and low-frequency oscillatory activity immediately before time measurement were altered by the length of the intended time interval. These results indicate that the state of the network, including the striatum, changes with the intended timing, which lead to different time courses of preparatory activity. Thus, the basal ganglia appear to be responsible for measuring time in the range of several hundred milliseconds to seconds, whereas the cerebellum is responsible for regulating self-timing variability in the subsecond range. The second half of this chapter presents studies related to periodic timing. During eye movements synchronized with alternating targets at regular intervals, different neurons in the cerebellar nuclei exhibit activity related to movement timing, predicted stimulus timing, and the temporal error of synchronization. Among these, the activity associated with target appearance is particularly enhanced during synchronized movements and may represent an internal model of the temporal structure of stimulus sequence. We also considered neural mechanism underlying the perception of periodic timing in the absence of movement. During perception of rhythm, we predict the timing of the next stimulus and focus our attention on that moment. In the missing oddball paradigm, the subjects had to detect the omission of a regularly repeated stimulus. When employed in humans, the results show that the fastest temporal limit for predicting each stimulus timing is about 0.25 s (4 Hz). In monkeys performing this task, neurons in the cerebellar nuclei, striatum, and motor thalamus exhibit periodic activity, with different time courses depending on the brain region. Since electrical stimulation or inactivation of recording sites changes the reaction time to stimulus omission, these neuronal activities must be involved in periodic temporal processing. Future research is needed to elucidate the mechanism of rhythm perception, which appears to be processed by both cortico-cerebellar and cortico-basal ganglia pathways.

Sensory and motor representations of internalized rhythms in the cerebellum and basal ganglia

Both the cerebellum and basal ganglia are involved in rhythm processing, but their specific roles remain unclear. During rhythm perception, these areas may be processing purely sensory information, or they may be involved in motor preparation, as periodic stimuli often induce synchronized movements. Previous studies have shown that neurons in the cerebellar dentate nucleus and the caudate nucleus exhibit periodic activity when the animals prepare to respond to the random omission of regularly repeated visual stimuli. To detect stimulus omission, the animals need to learn the stimulus tempo and predict the timing of the next stimulus. The present study demonstrates that neuronal activity in the cerebellum is modulated by the location of the repeated stimulus and that in the striatum (STR) by the direction of planned movement. However, in both brain regions, neuronal activity during movement and the effect of electrical stimulation immediately before stimulus omission were largely dependent on the direction of movement. These results suggest that, during rhythm processing, the cerebellum is involved in multiple stages from sensory prediction to motor control, while the STR consistently plays a role in motor preparation. Thus, internalized rhythms without movement are maintained as periodic neuronal activity, with the cerebellum and STR preferring sensory and motor representations, respectively.