feedback. Several projects in the lab are aimed at deciphering this
ubiquitous, but poorly understood, aspect of cortical connectivity. We have
recently shown that feedback from V2 and V3 has a relatively selective
effect on the non-classical surrounds of V1 receptive fields (Nassi et al.
2013; Nassi et al. 2014). These surrounds are critical for vision, because
they allow local, feature-selective responses to be modulated by the
context in which they occur. This modulation is surprisingly sophisticated,
and appears well suited to reduce redundancy and create sparse
representations in visual cortex via input-gain control (Trott & Born
multi-electrode arrays and cortical cooling, we are exploring the role of
feedback in creating feature-specific surround suppression (Alex Trott, PiN Graduate Student; collaboration with Dr. Steve Lomber).
multi-contact “V-probes” to record across layers in V1 while inactivating
MT with a new class of MRI-compatible cryoloops,
we are testing hypotheses regarding layer-specific feedback and the role of
MT feedback in generating motion-selective surround suppression (Till
Hartmann, Postdoctoral Fellow).
animals trained to discriminate the orientation of noisy Gabor stimuli, we
are testing the predictions of a hierarchical Bayesian model of perceptual
inference. This involves recordings in V1 with multi-electrode arrays while
inactivating V2 feedback (Camille Gomez-Laberge, Postdoctoral Fellow;
collaboration with Dr.
trans-synaptically transported viruses and immunocytochemistry, we are
examining how feedback interacts with local cortical circuits (Vladimir
Berezovskii, Imaging Specialist; collaboration with Dr. Connie Cepko).
We are developing computational
models to help us understand how inactivating inputs to a region of the
cortex dramatically affect neuronal variability (Camille Gomez-Laberge,
Postdoctoral Fellow; collaboration with Dr. Gabriel Kreiman).