The NIDCD supports studies of the chemical senses—taste, smell, and chemethesis (chemically provoked irritation)—to enhance our understanding of how individuals communicate with their environment and how human chemosensory disorders can be diagnosed and treated.
Smell and taste receptor cells are continually replaced throughout life and are replaced rapidly in response to injury such as exposure to pollutants and airborne toxins. These are the only known mammalian sensory cells with this native regenerative capability. Further studies are needed to advance our knowledge of the process of receptor cell regeneration, including those focused on stem cell differentiation and maintenance.
The regenerative capability of the olfactory system declines with age, with important consequences for our increasingly aged population. Although estimates of the prevalence of olfactory impairment vary, researchers estimate that more than one-third of adults over age 70 have olfactory deficits. Since both taste and smell contribute to flavor, olfactory deficits affect the flavor of foods and consequently food intake, diet and overall nutrition, and health status. The NIDCD encourages further studies of this age-related decline in olfactory sensitivity, including the development of better diagnostic tests and animal models for use in studying why this decline occurs and how to prevent it.
Great advances have been made in understanding how receptors cells detect chemical cues and how this information is transmitted to the brain. The NIDCD encourages further molecular and cellular studies of the peripheral mechanisms underlying chemosensation, including studies aimed at characterizing vertebrate and invertebrate chemoreceptors with respect to their structure, function, signaling pathways, patterns of gene expression, and regulation.
The NIDCD supports studies of the central processing of chemosensory information including the underlying neural circuitry of central olfactory and gustatory brain regions and how these circuits fail in pathology. NIDCD investigators have been at the forefront of developing and applying state-of-the-art recording, imaging, computational, and behavioral approaches to examine neural circuit function in awake, behaving animals.
The NIDCD's interest in central chemosensory processing remains broad. Further studies are encouraged to examine the development and plasticity of neural circuits, the functions and connectivity of cortical structures that interpret chemical senses information, the complex multisensory aspects of flavor perception and eating behavior, and the top-down modulation of sensory input and ways in which this is shaped by motivational or cognitive factors. The NIDCD also supports the continued development of tools for the analysis of chemosensory neurons, circuits, and behaviors.
The NIDCD encourages clinical chemosensory research for improved diagnosis, prevention, and treatment of chemosensory disorders. Further research is needed to develop validated hedonic and other measures and methods for assessing and diagnosing chemosensory deficits in adult, pediatric, and disordered populations for both research purposes and in-the-field clinical assessments. Additional clinical and epidemiological studies will allow researchers to better understand the effects of factors such as diet, early dietary experiences, individual genetic variation, aging, infection, and disease on chemosensory sensitivities and to link chemosensory deficits to other clinical disorders. The NIDCD also supports research on the development of bitter-taste blockers in an effort to identify compounds that can mask the bitter taste of essential medications, especially for young children.