A correlation of basic science and clinical symptoms in the human to propose a new theory for how the vestibular system works Neil S. Longridge Professor Emeritus, Division of Otolaryngology Department of Surgery, Faculty of Medicine, University of British Columbia Vancouver, BC CANADA *Arthur I. Mallinson, Clinical Associate Professor, Division of Otolaryngology Department of Surgery, Faculty of Medicine, University of British Columbia Vancouver, BC CANADA NS Longridge † *AI Mallinson † These authors contributed equally to this work. ABSTRACT; Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires instantaneous decision-making. The vestibular system plays an essential role in this process, initiating an emergency response. The afferent otolithic neural response is the first directionally oriented information to reach the cortex, and can then be used to initiate an appropriate protective response. Some vestibular efferent axons feed directly into the type I vestibular hair cells. This allows for rapid vestibular feedback via the striated organelle (STO), which has been largely ignored in most texts. We propose that this structure is essential in emergency fall prevention, and also that the system of sensory detection and resultant motor response works by having efferent movement information transmitted to the maculae simultaneously with the movement commands. This results in the otolithic membrane positioning itself precisely for the planned movement, and any error is due to an unexpected external cause. Error is fed back via the vestibular afferent system. The efferent system through the STO causes macular otolithic membrane movement which occurs simultaneously with the initiating motor command. As a result, no vestibular afferent activity occurs unless an error must be dealt with.

Both auditory and vestibular primary afferent neurons can be activated by sound and vibration. This review relates differences between them to the different receptor/synaptic mechanisms of the two systems as shown by indicators of peripheral function – cochlear and vestibular compound action potentials (cCAPs and vCAPs) to click stimulation as recorded in animal studies. Sound and vibration sensitive type 1 receptors at the striola of the utricular macula are enveloped by the unique calyx afferent ending which has three modes of synaptic transmission. Glutamate is the transmitter for both cochlear and vestibular primary afferents, however blocking glutamate transmission has very little effect on vCAPs but greatly reduces cCAPs. We suggest that the ultrafast non-quantal synaptic mechanism called resistive coupling is the cause of the short latency vestibular afferent responses and related results – failure of transmitter blockade, masking, and temporal precision. This “ultrafast” non-quantal transmission is effectively electrical coupling dependent on the membrane potentials of the calyx and the type 1 receptor. The major clinical implication is that decreasing stimulus rise-time increases vCAP response, corresponding to the increased VEMP response in human subjects . Short rise-times are optimum in human clinical VEMP testing, whereas long rise-times are mandatory for audiometric threshold testing.

The black-chinned tilapia Sarotherodon melanotheron is the most abundant fish species in the Nakwa (a closed lagoon) and Brenu (an open lagoon) in the Central region of Ghana. Aspects of the life history characteristics and the ecology of the fish populations in both lagoons were studied to assess the bio-ecological status of this important resource. The estimated von Bertalanffy growth parameters were L∞ = 12.04 cm; K =2.76 year-1 for the Nakwa Lagoon samples and L∞ = 13.44 cm; K = 3.27 years-1 for Brenu Lagoon samples. Daily otolith incremental rate ranged from 0.01-0.03mm per day and 0.01-0.02mm per day for Nakwa and Brenu lagoons respectively. Stomach content analysis of the fish samples revealed that the species are planktivorous and the range of food varied between the lagoons. Green algae was the most prevalent food item in the stomachs of the fish samples from Nakwa with frequency of 69% while diatoms (80.5%) were most prevalent phytoplanktonic food item in for the fish in Brenu lagoon. The results of this study of Sarotherodon melanotheron from the two lagoons and can be used to improve on management policies, maximize yield and to sustain the fishery resources.