Neuronal Encoding of Multisensory Motion Features in the Rat Associative Parietal Cortex

Motion perception is facilitated by the interplay of various sensory channels. In rodents, the cortical areas involved in multisensory motion coding remain to be identified. Using voltage-sensitive-dye imaging, we revealed a visuo–tactile convergent region that anatomically corresponds to the associative parietal cortex (APC). Single unit responses to moving visual gratings or whiskers deflections revealed a specific coding of motion characteristics strikingly found in both sensory modalities. The heteromodality of this region was further supported by a large proportion of bimodal neurons and by a classification procedure revealing that APC carries information about motion features, sensory origin and multisensory direction-congruency. Altogether, the results point to a central role of APC in multisensory integration for motion perception.

The expression of path in three satellite-framed languages

Cross-linguistic studies of the lexicalization of motion tend to contrast satellite- with verb-framed languages (e.g. Slobin 1996; 2004; Cardini 2008; Özçalışkan & Slobin 2003; Kopecka 2004; Fargard et al. 2013, etc.) and concentrate less frequently on intra-typological analyses (but cf. e.g. Filipović 2007; Hasko 2010; Ibarretxe-Antuñano 2009; Ibarretxe-Antuñano & Hijazo-Gascón 2012). Even fewer studies contrast genetically related languages (but cf. e.g. Łozińska 2018). The main aim of this study was to establish the path-saliency cline of three satellite-framed languages: Polish, Russian, and English. The analysis was based on elicited data. The overall patterns of expressing the path of motion in the three languages were shown to be caused by their belonging to the same typological category. The differences could be attributed, to a large extent, to differences in the morphological structures and in the lexical repertoires of motion-coding expressions available to the speakers of the three languages. However, the analysis of descriptions of three specific spatial situations (i.e. vertical, boundary-crossing, and deictic relations) pointed to other factors that may influence path coding in the three languages. Thus, despite the satellite-verb character of the languages examined and the morpho-syntactic differences between them, all our participants, who were native speakers of the three languages examined, tended to code vertical relations by means of path verbs. The number of tokens of path verbs used to code this particular spatial relation was found to be higher than the number of tokens of path verbs used to code deictic or boundary-crossing motion.

Neuronal variability and tuning are balanced to optimize naturalistic self-motion coding in primate vestibular pathways

It is commonly assumed that the brain’s neural coding strategies are adapted to the statistics of natural stimuli. Specifically, to maximize information transmission, a sensory neuron’s tuning function should effectively oppose the decaying stimulus spectral power, such that the neural response is temporally decorrelated (i.e. ‘whitened’). However, theory predicts that the structure of neuronal variability also plays an essential role in determining how coding is optimized. Here, we provide experimental evidence supporting this view by recording from neurons in early vestibular pathways during naturalistic self-motion. We found that central vestibular neurons displayed temporally whitened responses that could not be explained by their tuning alone. Rather, computational modeling and analysis revealed that neuronal variability and tuning were matched to effectively complement natural stimulus statistics, thereby achieving temporal decorrelation and optimizing information transmission. Taken together, our findings reveal a novel strategy by which neural variability contributes to optimized processing of naturalistic stimuli.

Self-motion processing in visual and entorhinal cortices: inputs, integration, and implications for position coding

The sensory signals generated by self-motion are complex and multimodal, but the ability to integrate these signals into a unified self-motion percept to guide navigation is essential for animal survival. Here, we summarize classic and recent work on self-motion coding in the visual and entorhinal cortices of the rodent brain. We compare motion processing in rodent and primate visual cortices, highlighting the strengths of classic primate work in establishing causal links between neural activity and perception, and discuss the integration of motor and visual signals in rodent visual cortex. We then turn to the medial entorhinal cortex (MEC), where calculations using self-motion to update position estimates are thought to occur. We focus on several key sources of self-motion information to MEC: the medial septum, which provides locomotor speed information; visual cortex, whose input has been increasingly recognized as essential to both position and speed-tuned MEC cells; and the head direction system, which is a major source of directional information for self-motion estimates. These inputs create a large and diverse group of self-motion codes in MEC, and great interest remains in how these self-motion codes might be integrated by MEC grid cells to estimate position. However, which signals are used in these calculations and the mechanisms by which they are integrated remain controversial. We end by proposing future experiments that could further our understanding of the interactions between MEC cells that code for self-motion and position and clarify the relationship between the activity of these cells and spatial perception.