Emergence of transformation-tolerant representations of visual objects in rat lateral extrastriate cortex

Abstract

Rodents are emerging as increasingly popular models of visual functions. Yet, evidence that rodent visual cortex is capable of advanced visual processing, such as object recognition, is limited. Here we investigate how neurons located along the progression of extrastriate areas that, in the rat brain, run laterally to primary visual cortex, encode object information. We found a progressive functional specialization of neural responses along these areas, with: (1) a sharp reduction of the amount of low-level, energy-related visual information encoded by neuronal firing; and (2) a substantial increase in the ability of both single neurons and neuronal populations to support discrimination of visual objects under identity-preserving transformations (e.g., position and size changes). These findings strongly argue for the existence of a rat object-processing pathway, and point to the rodents as promising models to dissect the neuronal circuitry underlying transformation-tolerant recognition of visual objects.DOI: http://dx.doi.org/10.7554/eLife.22794.001

Economic Choice as an Untangling of Options into Actions

“…When information passes from one region to the next, it is untangled (DiCarlo and Cox, 2007; DiCarlo et al, 2012; Pagan et al, 2013; Tafazoli et al, 2017). In other words, the information is preserved in an information-theoretic sense, but its format is transformed so that it is more readily decodable.…”

Intrinsic dynamics enhance temporal stability of stimulus representation along rodent visual cortical hierarchies

“…To investigate the temporal structure of neural representations of dynamic visual scenes, we used 32-channel silicon probes to record from V1 of anesthetized rats, as well as from three distinct areas within the lateral extrastriate cortex -the lateromedial (LM), laterointermediate (LI) and laterolateral (LL) areas (see Tafazoli et al (2017) for the anatomical layout of these areas). These target regions were chosen because, according to earlier findings by us and other groups (Kaliukhovich and Op de Beeck 2018;Tafazoli et al 2017;Vermaercke et al 2014;Vinken et al 2016;Vinken et al 2017), they are organized in a functional hierarchy (V1→LM→LI→LL) that is the homologous of the primate ventral stream. During the recordings, the animals were kept under anesthesia and were passively exposed to repeated presentations of nine 20s-long movies, which included six natural dynamic scenes (see example frames in Figure 1A), as well as three synthetic movies -namely, a random sequence of white noise patterns and the Fourier phase-scrambled versions of two of the natural movies (see Methods and supplementary videos).…”

“…During the recordings, the animals were kept under anesthesia and were passively exposed to repeated presentations of nine 20s-long movies, which included six natural dynamic scenes (see example frames in Figure 1A), as well as three synthetic movies -namely, a random sequence of white noise patterns and the Fourier phase-scrambled versions of two of the natural movies (see Methods and supplementary videos). In addition, drifting bars, displayed over a grid of visual field locations, were used to map the receptive fields (RFs) of the units recorded along a probe Niell and Stryker 2008;Tafazoli et al 2017). This allowed identifying the area from which each unit was recorded by tracking the polarity of the retinotopic map, which, in rodents, reverses at the borders between adjacent visual areas (Andermann et al 2011;Marshel et al 2011;Tafazoli et al 2017;Vermaercke et al 2014;Wang and Burkhalter 2007).…”

“…In addition, drifting bars, displayed over a grid of visual field locations, were used to map the receptive fields (RFs) of the units recorded along a probe Niell and Stryker 2008;Tafazoli et al 2017). This allowed identifying the area from which each unit was recorded by tracking the polarity of the retinotopic map, which, in rodents, reverses at the borders between adjacent visual areas (Andermann et al 2011;Marshel et al 2011;Tafazoli et al 2017;Vermaercke et al 2014;Wang and Burkhalter 2007). Overall, a total of 294 well-isolated single units were recorded in 18 rats: 168 from V1, 20 from LM, 36 from LI, and 70 from LL.…”

“…A popular conceptual framework posits that such invariance emerges progressively, as the outcome of largely feedforward processing, along a hierarchy of visual cortical areas that, in primates, is known as the ventral stream (DiCarlo and Cox 2007;DiCarlo et al 2012;Riesenhuber and Poggio 1999). This invariance hypothesis has been extensively validated in primates (Hong et al 2016;Li et al 2009;Pagan et al 2013;Rust and Dicarlo 2010;Yamins et al 2014) and, more recently, in rodents (Kaliukhovich and Op de Beeck 2018;Tafazoli et al 2017;Vermaercke et al 2014;Vinken et al 2016). However, existing studies have mainly focused on brief, static visual stimuli, designed to engage feedforward processing.…”