Directional responses of visual wulst neurones to grating and plaid patterns in the awake owl

Abstract

The avian retinothalamofugal pathway reaches the telencephalon in an area known as visual wulst. A close functional analogy between this area and the early visual cortex of mammals has been established in owls. The goal of the present study was to assess quantitatively the directional selectivity and motion integration capability of visual wulst neurones, aspects that have not been previously investigated. We recorded extracellularly from a total of 101 cells in awake burrowing owls. From this sample, 88% of the units exhibited modulated directional responses to sinusoidal gratings, with a mean direction index of 0.74 +/- 0.03 and tuning bandwidth of 28 +/- 1.16 degrees . A direction index higher than 0.5 was observed in 66% of the cells, thereby qualifying them as direction selective. Motion integration was tested with moving plaids, made by adding two sinusoidal gratings of different orientations. We found that 80% of direction-selective cells responded optimally to the motion direction of the component gratings, whereas none responded to the global motion of plaids, whose direction was intermediate to that of the gratings. The remaining 20% were unclassifiable. The strength of component motion selectivity rapidly increased over a 200 ms period following stimulus onset, maintaining a relatively sustained profile thereafter. Overall, our data suggest that, as in the mammalian primary visual cortex, the visual wulst neurones of owls signal the local orientated features of a moving object. How and where these potentially ambiguous signals are integrated in the owl brain might be important for understanding the mechanisms underlying global motion perception.

Comparative Study of Visual Pathways in Owls (Aves: Strigiformes)

“…Several studies show that cells in the visual wulst of owls respond to binocular disparity which suggest that this structure is involved in stereopsis [e.g. Pettigrew and Konishi, 1976;Pettigrew, 1979;Wagner and Frost, 1994;Nieder and Wagner, 2001;Baron et al, 2007]. This is further supported by the presence of an enlarged wulst in owls and other bird species with large binocular fields [Iwaniuk et al, 2008].…”

Affinity-Matrix representation of spike train activities in the early visual pathway

“…We used standard extracellular recording techniques in awake burrowing owls [7] to measure the responses of isolated forebrain neurons to moving sinusoidal grating of 10 different sizes (0.48, 0.72, 1.08, 2.04, 3, 3.6, 6, 8.99, 11.99 and 17.99 degrees of visual angle) presented at high (97%) and low contrasts (10%). Manual mapping was initially used to determine the location of the receptive field center, and all subsequent measurements were made trough the dominant eye, with gratings optimizaed for direction, spatial and temporal frequencies.…”

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

“…In the thalamofugal pathway, on the other hand, the optic nucleus of the thalamus receives retinal input and projects to the telencephalic visual Wulst. The visual Wulst shows prominent motion‐selective responses (Pettigrew, ; Nieder & Wagner, ; Baron et al ., ) and plays an important role in avian binocular vision (Nieder & Wagner, , ,b).…”