Fig 1 - uploaded by Marcelo Dias
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Representative examples of receptive field properties in the visual wulst of the awake burrowing owl. Top panels show results of a quantitative receptive field-mapping procedure applied to (A) a binocular cell (the type of cell most frequently encountered in our experiments) and (B) a monocular cell, driven by the contralateral eye (a type of cell rarely found). The mapping procedure consisted of constructing two-dimensional maps of neuronal responses to a binocularly presented single bar (10° in length and 0.5° in width) swept across the screen in 16 different orientations with 10 repetitions of each. The maps were normalized to the maximum amplitude of the responses. The centre of the receptive field was defined as the point in the two-dimensional map of maximal responsiveness indicated by the solid-line circle. In the case of the binocular unit shown in A, two distinct but partially overlapping patches of more intense activity can be seen, indicating the presence of two receptive fields, one for each eye. Stimuli subsequently used in the main experimental protocols were always monocularly presented in the centre of the receptive field of the dominant eye, i.e. the eye for which greater responses were obtained (dotted-line circle). (C) Spatial-frequency tuning curve of a cell, measured with a full-contrast grating drifting in the preferred direction at a rate of 1 Hz. (D) Temporal tuning curve of the same cell shown in C, measured with the same grating at a fixed spatial frequency of 2 cycles ⁄ °. In both tuning curves, data points represent the mean spike rate (spikes ⁄ s) for 10 repetitions of 2 s stimulus presentations minus spontaneous activity. Error bars indicate ± SEM. The arrows indicate the optimal frequency values.

Representative examples of receptive field properties in the visual wulst of the awake burrowing owl. Top panels show results of a quantitative receptive field-mapping procedure applied to (A) a binocular cell (the type of cell most frequently encountered in our experiments) and (B) a monocular cell, driven by the contralateral eye (a type of cell rarely found). The mapping procedure consisted of constructing two-dimensional maps of neuronal responses to a binocularly presented single bar (10° in length and 0.5° in width) swept across the screen in 16 different orientations with 10 repetitions of each. The maps were normalized to the maximum amplitude of the responses. The centre of the receptive field was defined as the point in the two-dimensional map of maximal responsiveness indicated by the solid-line circle. In the case of the binocular unit shown in A, two distinct but partially overlapping patches of more intense activity can be seen, indicating the presence of two receptive fields, one for each eye. Stimuli subsequently used in the main experimental protocols were always monocularly presented in the centre of the receptive field of the dominant eye, i.e. the eye for which greater responses were obtained (dotted-line circle). (C) Spatial-frequency tuning curve of a cell, measured with a full-contrast grating drifting in the preferred direction at a rate of 1 Hz. (D) Temporal tuning curve of the same cell shown in C, measured with the same grating at a fixed spatial frequency of 2 cycles ⁄ °. In both tuning curves, data points represent the mean spike rate (spikes ⁄ s) for 10 repetitions of 2 s stimulus presentations minus spontaneous activity. Error bars indicate ± SEM. The arrows indicate the optimal frequency values.

Contexts in source publication

Context 1
... properties of the cells that we encountered were consistent with those previously described in other owl species (Pettigrew & Konishi, 1976;Pettigrew, 1979). Visual receptive fields were usually well defined and small; they never exceeded 5° in their largest dimension. Almost all cells in our sample were responsive to stimulation of either eye (Fig. 1A). Only three cells were found to be exclusively driven by one eye (Fig. 1B). At this point, it is important to reiterate that the grating and plaid stimuli that we subsequently used to characterize the directional responses of neurones were only presented to the dominant eye. Cells in our sample also typically showed tuned profiles for ...
Context 2
... described in other owl species (Pettigrew & Konishi, 1976;Pettigrew, 1979). Visual receptive fields were usually well defined and small; they never exceeded 5° in their largest dimension. Almost all cells in our sample were responsive to stimulation of either eye (Fig. 1A). Only three cells were found to be exclusively driven by one eye (Fig. 1B). At this point, it is important to reiterate that the grating and plaid stimuli that we subsequently used to characterize the directional responses of neurones were only presented to the dominant eye. Cells in our sample also typically showed tuned profiles for the spatial and temporal frequency of optimally moving full-contrast ...
Context 3
... of neurones were only presented to the dominant eye. Cells in our sample also typically showed tuned profiles for the spatial and temporal frequency of optimally moving full-contrast gratings. In some cases, we determined quantitatively the preferred value for these two dimensions and found them to be consistent with our qualitative estimates ( Fig. 1C and D). Pettigrew (1979) reported the presence of several cell classes in the owl visual wulst, most of them having their correspondent in the mammalian V1. The response profiles that we encountered were consistent with many of these classes. Most notably, this also includes a cell type known as 'black bar specialists', unique for their ...
Context 4
... DI values were concentrated around a mean of 0.9, indicating a tendency towards unidirectionality without inhibition in the antipreferred direction, which was seen only in 20% of cells. The variability of tuning bandwidth values, which was apparent in the tuning curves shown in Fig. 2B and D, was reflected in the broad distribution shown in Fig. 2F (range 14.2-61.0°). The mean for the whole sample was 28.0° and roughly 45% of the cells had bandwidth values ranging between 20 and 30°. Values for directionally selective cells were not significantly different from those of nondirection-selective cells (27.8 ± 1.25° vs. 29.0 ± 3.0°, respectively; Wilcoxon rank sum test, P ¼ ...
Context 5
... using a different approach, the way in which component selectivity varied during the time course of the entire stimulus presentation. For this, we calculated the average component index for each of a series of 100 ms windows sliding over the whole period of stimulus presentation in 50 ms increments. Results from this analysis are presented in Fig. 10A. Despite a fair amount of variability among cells, it is clear that the strength of component selectivity dynamically unfolds as an initial transient followed by a relatively steady component that remains well above the level observed at stimulus onset and offset. A sharp increase is already noticeable during the first 100 ms response ...
Context 6
... selectivity is a process that builds up during the first 150 ms of the neurones' response, confirming the results presented in Fig. 9. Furthermore, it shows that, although higher during the early phase of the response, the strength of component selectivity settles to a sustained level throughout the response to stimulus motion. As can be seen in Fig. 10B, the firing rate of the CDS neurone population in response to both gratings and plaids shows a fairly similar temporal profile, indicating that the strength of component selectivity is somehow linked to changes in neuronal ...

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