Spatiotemporal frequency and speed tuning in the owl visual wulst

Abstract

The avian visual wulst is hodologically equivalent to the mammalian primary visual cortex (V1). In contrast to most birds, owls have a massive visual wulst, which shares striking functional similarities with V1. To provide a better understanding of how motion is processed within this area, we used sinusoidal gratings to characterize the spatiotemporal frequency and speed tuning profiles of 131 neurones recorded from awake burrowing owls. Cells were found to be clearly tuned to both spatial and temporal frequencies, and in a way that is similar to what has been reported in the striate cortex of primates and carnivores. Our results also suggest the presence of spatial frequency tuning domains in the wulst. Speed tuning was assessed by several methods devised to measure the degree of dependence between spatial and temporal frequency tuning. Although many neurones were found to be independently tuned, a significant proportion of cells showed at least some degree of dependence, compatible with the idea that some kind of initial transformation towards an explicit representation of speed is being carried out by the owl wulst. Interestingly, under certain constraints, a higher incidence of spatial frequency-invariant speed tuned profiles was obtained by combining our experimentally measured responses using a recent cortical model of speed tuning. Overall, our findings reinforce the notion that, like V1, the owl wulst is an important initial stage for motion processing, a function that is usually attributed to areas of the tectofugal pathway in lateral-eyed birds.

Distinct Functional Properties of Primary and Posteromedial Visual Area of Mouse Neocortex

“…The statistical level t for this test is 1.28 equivalent to a p value of 0.1 as previously described (Levitt et al, 1994;Priebe et al, 2003;Pinto and Baron, 2009). This approach allows us to split the neurons into three categories: (1) speed tuned when R d is significantly larger than R i or zero, (2) independently tuned when R i is significantly larger than R d or zero, and (3) "unclassed" if R d and R i are not different from each other or from zero (see Fig.…”

“…5) were averaged. To estimate the speed tuning of each neuron, we used a method described previously (Levitt et al, 1994;Priebe et al, 2003;Pinto and Baron, 2009). This approach first fits SF and TF tuning independently with Gaussian functions.…”

“…Their 2D spatiotemporal frequency tuning profiles showed similar peaks at high SF but the 2D shapes of the intensity bands were different, more vertically for the first neuron and more diagonally for the second neuron. For quantification, we followed a previously described approach (Levitt et al, 1994;Priebe et al, 2003;Pinto and Baron, 2009), determining whether the 2D response matrix of a neuron is better explained by independence or dependence of its SF and TF tuning (see Materials and Methods). Using the individual tuning profiles to SF (at the preferred TF) and TF (at the preferred SF), we then determined the matrix profiles for independent tuning (imatrix) (Fig.…”

Encoding of global visual motion in the nidopallium caudolaterale of behaving crows

“…Cells of the pigeon entopallium showed broad ranges of bandpass tuned speed filter functions ranging from 16 to 128 dva/s, with an average optimal speed of 55 dva/s (Gu et al ., ). In contrast, cells of the owl visual Wulst prefer much slower speeds in the range of 0.5–16 deg/s (Pinto & Baron, ). NCL seems to combine these two speed processing streams.…”

Spatiotemporal Frequency Tuning Dynamics of Neurons in the Owl Visual Wulst

“…The latter constitutes a very interesting comparative model to the study of V1 as these two structures, albeit presumably not having originated from common ancestry, show remarkable physiological and hodological similarities (Karten et al 1973;Shimizu and Bowers 1999). For instance, owl wulst neurons are tuned to stimulus orientation, binocular disparity, direction of motion, SF and TF, in ways that closely parallel their striate cortical counterparts (Baron et al 2007;Wagner 2000, 2001a,b;Pettigrew 1979;Pinto and Baron 2009). Studying the visual wulst of the owl may thus provide important insights on the constraints that have driven such evolutionary convergence.…”