Understanding the neuronal substrates of visual cognition is one of the ultimate goals of systems neuroscience. In our lab, we investigate how visual information is processed and reformatted across the cortical visual hierarchy, by performing multi-electrode neuronal recordings from multiple visual areas of the rat brain. Our work has focused on anatomical progression of extrastriate areas that, in the rat brain, run laterally to V1 (i.e., areas LM, LI, and LL), revealing a functional homology of this pathway with the primate ventral visual stream. Specifically, we found, along this progression:

• a sharp reduction of the amount of low-level information encoded by neuronal firing, and a concomitant increase in the ability of neuronal representations to support object recognition (Tafazoli et al., 2017)
• an increase of the nonlinearity of neuronal responses, along with a reduction of orientation tuning and an increase of the tendency of neurons to be tuned for multiple orientations (Matteucci et al., 2019)
• an increase in the temporal stability of neuronal representations of visual objects, both in terms of stimulus-evoked activity responses and intrinsic activity (Piasini et al., 2021)

We have also investigated whether rat visual cortex supports high-order processing of motion information, finding evidence of nonlinear integration of motion signals by a small population of primate-like pattern cells in V1 and LM (Matteucci et al, 2023).

In addition, we have started to explore the instructive role of visual experience during early postnatal life by rearing newborn rats in visually controlled environments. This approach has revealed that experiencing a temporal continuous visual world is necessary for the proper development of complex cells in V1 - the class of visual neurons that first show the property of transformation invariance in the visual system (Matteucci and Zoccolan, 2020).

Finally, earlier studies of the PI and his collaborators have investigated the properties of visual object representations in monkey inferotemporal cortex (IT), including:

• the encoding of multiple visual objects by IT neurons (Zoccolan et al., 2005; Li et al., 2009)
• the relationship between shape selectivity and transformation tolerance in IT (Zoccolan et al., 2007)
• the encoding of shape and semantic information in IT (Baldassi et al., 2013)

See below for a complete list of our neurophysiological studies.