The thalamocortical vestibular system in animals and humans

The origins of cerebral lateralization in humans are traced to the asymmetric prenatal development of the ear and labyrinth. Aural lateralization is hypothesized to result from an asymmetry in craniofacial development, whereas vestibular dominance is traced to the position of the fetus during the final trimester. A right-ear sensitivity advantage may contribute to a left-hemispheric advantage in speech perception and language functions, whereas left-otolithic dominance may independently promote right-sided motoric dominance and a right-hemispheric superiority in most visuospatial functions. The emergence of handedness is linked to the assumption of an upright posture in the early hominids, whereas the failure to develop clear vestibular asymmetry may underlie the poor motoric lateralization found in several neurodevelopmental disorders.

A general theory concerning the prenatal origins of cerebral lateralization in humans.

The sections in this article are:


1
Anatomical Background
1.1
Striatum

1.2
Pallidal-Subthalamic Relations

1.3
Basal Ganglia Output

1.4
Thalamocortical Projections




2
Motor Effects of Lesions
2.1
General Considerations

2.2
Lesions of Individual Nuclei




3
Motor Effects of Electrical Stimulation
3.1
Electrical Stimulation in Alert Animals

3.2
Electrical Stimulation in Anesthetized Animals

3.3
Do Basal Ganglia Exert Inhibitory Influence on Motor Mechanisms?




4
Single-Cell Studies in The Basal Ganglia
4.1
Spontaneous Activity

4.2
Temporal Relation to Movement

4.3
Somatotopic Organization

4.4
Relations to Parameters of Movement

4.5
Vestibular and Postural Mechanisms

4.6
Responses to Peripheral Stimuli

4.7
Relations to Specific Behaviors

4.8
Summary




5
Lesioning and Recording in Human Subjects

6
Motor Behavioral Studies
6.1
Reaction Time

6.2
Speed of Movement

6.3
Other Aspects of Motor Performance

6.4
Continuous Pursuit Movements




7
Pathophysiological Mechanisms of Basal Ganglia Disorders
7.1
Akinesia and Hyperactivity

7.2
Dyskinesias and Stereotyped Behavior

7.3
Rigidity

7.4
Resting Tremor




8
Interpretative Summary

Motor Functions of the Basal Ganglia

Recent discoveries have emphasized the role of the vestibular system in cognitive processes such as memory, spatial navigation and bodily self-consciousness. A precise understanding of the vestibular pathways involved is essential to understand the consequences of vestibular diseases for cognition, as well as develop therapeutic strategies to facilitate recovery. The knowledge of the “vestibular cortical projections areas”, defined as the cortical areas activated by vestibular stimulation, has dramatically increased over the last several years from both anatomical and functional points of view. Four major pathways have been hypothesized to transmit vestibular information to the vestibular cortex: 1) the vestibulo-thalamo-cortical pathway, which probably transmits spatial information about the environment via the parietal, entorhinal and perirhinal cortices to the hippocampus and is associated with spatial representation and self-versus object motion distinctions; 2) the pathway from the dorsal tegmental nucleus via the lateral mammillary nucleus, the anterodorsal nucleus of the thalamus to the entorhinal cortex, which transmits information for estimations of the head direction; 3) the pathway via the nucleus reticularis pontis oralis, the supramammillary nucleus and the medial septum to the hippocampus, which transmits information supporting hippocampal theta rhythm and memory; and 4) a possible pathway via the cerebellum, and the ventral lateral nucleus of the thalamus (perhaps to the parietal cortex), which transmits information for spatial learning. Finally a new pathway is hypothesized via the basal ganglia, potentially involved in spatial learning and spatial memory. From these pathways, progressively emerges the anatomical network of vestibular cognition.

/pdf/vestibular-pathways-involved-in-cognition-gqwdxdic03.pdf

Vestibular pathways involved in cognition.

To investigate the spatial and behavioral correlates of striatal neurons during displacement movements, the rostromedial dorsal striata (AP 1.0–2.2, ML 1.5–2.0) of five rats were surgically implanted with advanceable bundles of fine wire electrodes. After recovery, the rats were deprived of water and trained in a square-walled open field in a dark room. The behavioral task required alternating visits to water reservoirs in the center and in the four corners. A certain corner contained the first reward for each trial; after this reward, a cue card appeared in this corner for the rest of the trial. The firing rates of striatal units were compared as the rat moved between the center and the four corners of the arena. Analyses were made of 30 units. Eight of these had firing rates that significantly increased or decreased by 62–480% while the rat was in one or more quadrants of the arena. Six of these manifested such firing rate changes only as the rat performed certain behavioral sequences in the quadrant. Three other units fired as the rat's head was in a certain orientation relative to the arena walls, in all parts of the arena. To determine the principal controlling cues and hence the frame of reference of spatial selectivity of these units, the arena, while the rat was still inside, was rotated in total darkness. The first water reward was then presented at the same position relative to the outside room as before the rotation. The cue card was then illuminated in this corner as a visual cue for the extra-arena reference frame. All 11 neurons demonstrated spatial selectivity that rotated with the arena; thus, this activity was in the frame of reference of the arena and was not controlled by the visual cue. Six other units fired at rates up to six times their resting discharge or stopped firing completely in synchrony with initiation or execution of displacement movements, and two of these were also location selective. Four other units were silent as the rat performed the task, but fired tonically following arena rotations or other interruptions of the session, independent of the rat's location or movements. Nine analyzed units had very low firing rates (< 1 impulse/sec) and showed no discernible changes in activity as the rat performed the task. These patterns of unit activity indicate that fundamental informational components required for navigation are coded in the striatum.(ABSTRACT TRUNCATED AT 400 WORDS)

https://www.jneurosci.org/content/jneuro/13/9/3802.full.pdf

M. Potegal

Papers

Vestibular input to the caudate nucleus