My current research interests revolve around neurophysiological mechanisms underlying cognition in birds, in particular fast electrical ones involved in auditory cognition and sleep.Some illustrations of current work
My work thus far includes the following topics:
- Electrophysiology of auditory cognition
- Electrophysiology of sleep
- Dynamics of communicative interaction
- Phonetic perception
- Mechanisms of vocal production
- Scientific computing of vocal behavior
Figure 1: Multi-unit action potential responses in the auditory forebrain to repeated social call stimuli (aligned at 0 s.), simultaneously recorded with a 32-electrode matrix array. The figure consists of 32-bipartite subfigures, each of which corresponds to a locus in the brain. Color codes spike rate. Time is on the horizontal axes, stimulus repetition number on the vertical axes. The distances between loci are 200 microns vertically, and 400 microns horizontally. Each subfigure consists of an upper and lower part, which correspond to the responses to common calls (100 random responses out of 900 presented) and rare ones ('oddball', all 100 responses that were interspersed with the 900 common ones), respectively. Note the strong response in the left-lower and right-upper areas. the oddball, which is absent in the common call. Click on figure to see large version
Figure 2: Local field potentials from the same recordings as in Figure 1. Click on figure to see large version
Figure 3: A Two contact calls were played in a switching-oddball design, where each stimulus alternates between standard (expected) and deviant (unexpected) roles. B Multi-unit activity (MUA) was recorded in L2, NCM and CMM from 32 sites simultaneously (parasagittal view of medial auditory forebrain). C To obtain an activity profile, the amplitude of the raw MUA signal was averaged into 2.5-ms bins for each site, and the result is colour-coded and displayed in an image plot where pixels represent electrodes (mean of 25 events). The tripartite image plot represents the activity to call Q when it was expected (left), and when it was unexpected (middle); the right part is simply the difference between the two, and shows that sites in NCM/CMM (cf. B) are active predominantly only when a call is unexpected. The indicated time in ms is relative to the start of the call. The series of image plots represents the evolution of activity over time and space at resolutions of 2.5 ms and 200 µm. For reasons of space, only results up to 75 ms are shown, but deviant event related activity can be observed up to seconds after call start. Click on figure to see large version
Figure 4: Scatterplot of delivery time against mean fundamental frequency of all vocalization elements (between 400-700 Hz) of two communicating zebra finches over the period of one week, as an example of the type of information that can be explored and analyzed with NoteLab. Social calls have been identified on the basis of multivariate techniques applied to acoustic features. The other sound elements (grey) are either song syllables, other call types, or non-vocal noise.
Figure 5: Zebra finch song motif visualized by a sparse time-frequency representation (see work of Gardner and Magnasco).
Between the end of my MSc research and the beginning of my PhD work, I designed and carried out applied research projects for rain forest conservation, through Bioproca Foundation, an organization that my colleague biologist and friend Koen Verhoeven and I founded for this purpose. We focused on the ecology of canopy epiphytes such as orchids and bromeliads, and based our field work in Rara Avis, Costa Rica. Canopy orchids and bromiliads can have a high value as ornamental plants, but are often very difficult to cultivate artificially. Ultimately, our research was aimed at the cultivation of highly specialised species by using their natural habitat in part of the production process. Traditionally, the gathering of valuable non-wood rainforest products is considered as a valuable source of additional income to local communities. By focusing on local cultivation and production, rather than mere collection, the economic potential is enhanced considerably, which provides local communities living in or near rainforests with a new and realistic opportunity for sustainable socio-economic development, based on their biodiversity resources.