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Response (% dF/F)
43210 - 1
100 individual cells
They have selectively activated 100 neurons in the brain of an awake and behaving mouse (see https://youtu.be/dh T8-Ri-
06wQ). The animal’s running activity is
coupled to movement around a virtual re-
ality environment, allowing it to perform
complex spatial tasks while being head-fixed to enable effective and accurate imaging and stimulation.
The current example uses 1040 nm fem-
tosecond pulses—at an average power of
6 m W per cell and 100 ms exposure dura-
tion—to trigger neural activity. Since the
photoactivation process is based on multi-
photon absorption of the near-infrared wave-
length laser, the resulting high spatial resolution ensures the ability to address selected
neurons without affecting neighboring cells.
The video-recorded experiment shows
the average fluorescence response of the
calcium sensitive protein to 10 stimulation
cycles. To isolate the effect of the stimulus
on the cell activity, the change in fluorescence (∆F) is divided by the fluorescence (F).
Figure 4 captures the average ∆F/F 0.3 s af-
ter photostimulation, and depicts the tem-
poral progress of the fluorescence increase
∆F/F in each cell resulting from the stimu-
lating laser pulse. On average, the signal in-
creases by more than 130%.
The all-optical technique being developed by Prof. Häusser’s group promises
to enable great progress in neuroscientif-ic research. It allows targeting of neurons
based not just on anatomy or genetic properties, but on functional attributes. It also
allows the recording and manipulation of
neural circuits at both spatial and tempo-
ral resolution that correlates with normal
operation as the subject moves. Thus, it
offers a new approach to understanding
how activity in defined groups of neurons
have a causative effect on behavior.
Patrizia Krok is marketing manager and Michael Mei is CEO, both at Menlo
Systems, Martinsried, Germany; e-mail:
firstname.lastname@example.org; www.menlosys-tems.com, while Nick Robinson is a research
associate at the Wolfson Institute for Biomedical
Research, Division of Medicine, at University
College London; www.ucl.ac.uk/wibr.
FIGURE 4. Fluorescence increase of brain
cells 0.3 s after photostimulation, average
over 10 stimulation cycles; temporal evolution
of the fluorescence increase in 100 individual
cells (grey) and the average signal (black)
after photostimulation (blue bar).