Vision and retina evolution: how to develop a retina

Harmony in the Molecular Orchestra of Hearing: Developmental Mechanisms from the Ear to the Brain

Auditory processing in mammals begins in the peripheral inner ear and extends to the auditory cortex. Sound is transduced from mechanical stimuli into electrochemical signals of hair cells, which relay auditory information via the primary auditory neurons to cochlear nuclei. Information is subsequently processed in the superior olivary complex, lateral lemniscus, and inferior colliculus and projects to the auditory cortex via the medial geniculate body in the thalamus. Recent advances have provided valuable insights into the development and functioning of auditory structures, complementing our understanding of the physiological mechanisms underlying auditory processing. This comprehensive review explores the genetic mechanisms required for auditory system development from the peripheral cochlea to the auditory cortex. We highlight transcription factors and other genes with key recurring and interacting roles in guiding auditory system development and organization. Understanding these gene regulatory networks holds promise for developing novel therapeutic strategies for hearing disorders, benefiting millions globally.

Retinal primary cilia and their dysfunction in retinal neurodegenerative diseases: beyond ciliopathies

Primary cilia are sensory organelles that extend from the cellular membrane and are found in a wide range of cell types. Cilia possess a plethora of vital components that enable the detection and transmission of several signaling pathways, including Wnt and Shh. In turn, the regulation of ciliogenesis and cilium length is influenced by various factors, including autophagy, organization of the actin cytoskeleton, and signaling inside the cilium. Irregularities in the development, maintenance, and function of this cellular component lead to a range of clinical manifestations known as ciliopathies. The majority of people with ciliopathies have a high prevalence of retinal degeneration. The most common theory is that retinal degeneration is primarily caused by functional and developmental problems within retinal photoreceptors. The contribution of other ciliated retinal cell types to retinal degeneration has not been explored to date. In this review, we examine the occurrence of primary cilia in various retinal cell types and their significance in pathology. Additionally, we explore potential therapeutic approaches targeting ciliopathies. By engaging in this endeavor, we present new ideas that elucidate innovative concepts for the future investigation and treatment of retinal ciliopathies.

The Development of Speaking and Singing in Infants May Play a Role in Genomics and Dementia in Humans

The development of the central auditory system, including the auditory cortex and other areas involved in processing sound, is shaped by genetic and environmental factors, enabling infants to learn how to speak. Before explaining hearing in humans, a short overview of auditory dysfunction is provided. Environmental factors such as exposure to sound and language can impact the development and function of the auditory system sound processing, including discerning in speech perception, singing, and language processing. Infants can hear before birth, and sound exposure sculpts their developing auditory system structure and functions. Exposing infants to singing and speaking can support their auditory and language development. In aging humans, the hippocampus and auditory nuclear centers are affected by neurodegenerative diseases such as Alzheimer's, resulting in memory and auditory processing difficulties. As the disease progresses, overt auditory nuclear center damage occurs, leading to problems in processing auditory information. In conclusion, combined memory and auditory processing difficulties significantly impact people's ability to communicate and engage with their societal essence.

Neurosensory development of the four brainstem-projecting sensory systems and their integration in the telencephalon

Somatosensory, taste, vestibular, and auditory information is first processed in the brainstem. From the brainstem, the respective information is relayed to specific regions within the cortex, where these inputs are further processed and integrated with other sensory systems to provide a comprehensive sensory experience. We provide the organization, genetics, and various neuronal connections of four sensory systems: trigeminal, taste, vestibular, and auditory systems. The development of trigeminal fibers is comparable to many sensory systems, for they project mostly contralaterally from the brainstem or spinal cord to the telencephalon. Taste bud information is primarily projected ipsilaterally through the thalamus to reach the insula. The vestibular fibers develop bilateral connections that eventually reach multiple areas of the cortex to provide a complex map. The auditory fibers project in a tonotopic contour to the auditory cortex. The spatial and tonotopic organization of trigeminal and auditory neuron projections are distinct from the taste and vestibular systems. The individual sensory projections within the cortex provide multi-sensory integration in the telencephalon that depends on context-dependent tertiary connections to integrate other cortical sensory systems across the four modalities.