1. Journal of Cerebral Blood Flow & Metabolism (2010), 1–2
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Feature Article Commentary
A new technique for functional imaging
in songbirds and beyond
Henning U Voss
Pre-Clinical Imaging Division, Citigroup Biomedical Imaging Center, Weill Cornell Medical College,
New York, New York, USA
Journal of Cerebral Blood Flow & Metabolism advance online publication, 20 October 2010; doi:10.1038/jcbfm.2010.190
Keywords: functional MRI; functional optical imaging; hemodynamics; songbirds
The quantitative study of cerebral hemodynamics information to more classical methods of birdsong
requires measurement methods with high spatial and research based on electrical recordings or functional
temporal resolution. In the best case, these methods MRI by virtue of its quantitative nature. For example,
are noninvasive or even contact free. Mottin et al could it be used to get a better picture of how the
(2010, this issue) propose picosecond optical tomo- song system works as a network of connected song
graphy, or POT, to quantitatively image hemody- nuclei by quantitatively analyzing the hemodynamic
namics in a contact-free way. POT relies on white response dynamics?
laser light spectral absorption in the near-infrared Besides further applications in songbird research,
measured with a streak camera. The tens-of- these advantages could also play out in functional
femtosecond temporal resolution of the streak cam- studies of neurovascular plasticity, as has been
era enables depth-specific imaging of oxy- and observed for example after focal cerebral injury
deoxy-hemoglobin concentration with submillimeter (Whitaker et al, 2007), or in neurovascular repair
resolution. The authors validate their technique on a mechanisms after induction of small-scale cortical
songbird model of auditory perception and show vascular lesions (Nishimura et al, 2006) that are
results consistent with previous findings that were believed to have a function in aging-related cognitive
obtained using functional magnetic resonance ima- decline. As they point out at the end of the article,
ging (MRI). Furthermore, they shed new light onto this is a field worth studying for Mottin et al too, by
brain oxygen recoupling in these tachymetabolic using their technology to investigate a proposed link
animals, results that would be difficult to obtain with between brain aging and changes in vascular reac-
conventional functional MRI. tivity found by functional MRI. However, it remains
The songbird model is an interesting choice for to be seen if POT can compete with the very powerful
demonstrating the validity of POT, as songbirds imaging techniques already used in this field, such
provide a versatile model for studying neuronal as multiphoton microscopy and voltage sensitive dye
plasticity (Brenowitz, 2004). This includes the ability imaging (Brown et al, 2009).
to generate a significant amount of new neurons in Finally, the authors propose a way to expand POT
adult life (Nottebohm, 2002), as well as the rare trait into a true two-dimensional imaging method (so far
of vocal learning (Mooney, 2009). Songbirds produce it can only image line segments) by sweeping
behavioral patterns of high complexity (song) that the optical field over the sample. In the long
can be precisely recorded and related to neuronal term, functional imaging methods like this could,
dynamics from time scales of milliseconds to a time once developed for human applications, become
spanning several generations (Hahnloser et al, 2002; more relevant clinically (Prakash et al, 2009). As
Feher et al, 2009). It might be possible that POT adds functional MRI maps of the human cortex display a
considerable amount of interindividual variability, it
is necessary to map, for example, eloquent sensor-
Correspondence: Dr HU Voss, Pre-Clinical Imaging Division, imotor areas before or during brain tumor surgery.
Citigroup Biomedical Imaging Center, Weill Cornell Medical Often, a combination of electrocortical stimulation
College, 516 E 72nd Street, New York, NY 10021, USA. mapping on the exposed brain and functional MRI is
E-mail: hev2006@med.cornell.edu
This study was supported by NSF award 0956306 and Nancy M
used to identify eloquent sensorimotor areas
and Samuel C Fleming Research Scholar Award in Intercampus and thus to reduce surgical risks (Holodny, 2008). It
Collaborations, Cornell University. can be envisioned that optical imaging methods
Received 30 September 2010; accepted 30 September 2010 based on POT could be used in the operating room to

2. Commentary
2
rapidly map individual eloquent cortical areas Hahnloser RHR, Kozhevnikov AA, Fee MS (2002) An ultra-
during surgery. sparse code underlies the generation of neural se-
quences in a songbird. Nature 419:65–70
Holodny AI (2008) Functional Neuroimaging—A Clinical
Disclosure/conflict of interest Approach. New York: Informa Healthcare
Mooney R (2009) Neural mechanisms for learned birdsong.
The author declares no conflict of interest. Learn Mem 16:655–69
Mottin S, Montcel B, de Chatellus HG, Ramstein S (2010)
Functional white laser imaging to study brain oxygen
uncoupling/recoupling in songbirds. J Cereb Blood Flow
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Journal of Cerebral Blood Flow & Metabolism (2010), 1–2