May 2012: This Month in JoVE

The May issue of JoVE (Journal of Visualized Experiments) includes a handful of articles that deal with the senses and perception. Specifically, articles involving gustation (taste), olfaction (smell), nociception (pain), and the vestibular senses (balance and inertial movement) will be released.

The vestibular system is important for perceiving inertial movement, and inertial information is an important component of path integration. Path integration is a process by which the brain integrates multisensory information during movement, so that we maintain a sense of our body’s position, relative to a starting point. In nature, many organisms make use of this process, in order to find their way back to their nests or burrows after looking for food.

This May, JoVE will publish a method filmed at the Max Plank Institute of Biological Cybernetics , which explores how path integration occurs in three dimensions. Most studies of this phenomenon are conducted in two dimensions, but thanks to a motion simulator with a large range of motion, path integration can be assessed in the horizontal and vertical planes. By controlling the sensory stimuli delivered to subjects in this device, our authors can dissect the relative contributions of visual and inertial information to estimations of starting position.

Through an elegantly designed series of experiments, these investigators find that subjects are more likely to overestimate angles of movement in the horizontal plane versus the verticals. They also find that subjects were slower to point to the starting position when they had to rely only on inertial stimuli. The underlying neuronal mechanism behind path integration is poorly understood, and further experiments using this system will provide insight into how humans maintain spatial orientation during movement, which has implications that range from understanding vestibular disorders and training better pilots.

Concerning gustation, JoVE will publish a procedure for isolating and culturing human fungiform taste cells this May. Back in 2010, we published an article that dealt with isolation of human fungiform papillae – a subtype of the tiny stuctures on our tongues that contain tastebuds. While papillae collection is suitable for acute experiments, long-term studies of taste cells require them to be isolated and cultured.

For the first time ever reported, our authors demonstrate the isolation and culture of human fungiform taste cells and show that they can be maintained in culture for up to 8 passages, or one year. The ability to culture these cells for an extended period of time enables studies of proliferation and regeneration, and obviates the need to repeatedly collect papillae from donors.

Regarding olfaction, JoVE will release an article from the Department of Agriculture, which describes an experiment that transforms the antennae of insects into a screening tool for new pesticide alternatives. After isolating plant volatile compounds via gas chromatography and mass spectrometry, these investigators screen the compounds for biological activity using the electroantennagram (EAG).

Because not all of the volatile compounds emitted by plants elicit biological responses, such a bioassay is incredibly important for finding candidate molecules that can affect insect behavior. In turn, behavioral experiments, can determine whether or not a plant volatile can attract an insect. Plant volatile attractants can be used to confuse insects and potentially could serve as a safe alternative to pesticides.

Thermal nociception, or the perception of noxious thermal stimuli, is the focus of an article from the University of Texas this May. Specifically, thermal nociception is investigated in Drosophila larvae using two methods: the heat probe assay and the heat plate assay. Interestingly, for both methods, larvae must first be treated with UV radiation to induce tissue damage and sensitize thermal nociceptive neurons, which usually respond with a very high threshold.

As its name implies, the heat probe assay, uses a custom-built thermal probe to locally administer thermal stimuli. Nociception is quantified by recording the latency between stimulus onset and withdraw behavior. Intuitively, the second method, or heat plate assay, involves placing drosophila larvae on a heating plate within a drop of water to test whole body responses to noxious heat. Upon placement, drosophila exhibit a series of characteristic behaviors including rolling, whipping, or even seizure-like activity. When combined with genetic manipulation, these assays can provide information about the genes underlying thermal nociception – a highly conserved process, from larvae to mammals.

Naturally, an exploration of the senses is not all JoVE has to offer this may. Other notable publications involve painting the pancreas to maintain orientation during histology, using an automated operant device to test multi-cognitive functions in mice, examining tamoxifen-induced apoptosis using timelapse video microscopy, and creating a convenient tool for fishing out lost samples from liquid nitrogen tanks. Stay tuned.