Whole Shape or Feature Representation?
Neuronal Coding of Dynamic Partial Shape Views in Macaque Anterior Body Patch.
Humans easily recognize objects even if only a small part of the object is available in every instant at the same retinal position (Parks TE, 1965; Anstis SM and Atkinson J, 1967). This requires a strong spatiotemporal integration of the shortly available visual features. Previous fMRI studies suggested that the lateral occipital complex represents a whole shape percept under these slit viewing conditions (Yin C et al., 2002; Orlov T and Zohary E, 2018). To investigate the neuronal mechanisms, we measured neuronal activity in the macaque anterior body patch, presenting animal silhouettes moving behind a narrow 0.48° horizontal or vertical slit in both directions.
To search for responsive neurons, we used a set of seventy silhouettes of animals. For each neuron we selected three shapes based on their responses: one with the highest activity, another one with the lowest firing rates and a third in between the two. The selected stimuli were presented in anorthoscopic viewing conditions. The trials started with the presentation of a fixation spot for 300 ms on top of a noise background (10 deg size), then a vertical or horizontal empty slit inside the noise pattern was presented 1° to the right in the contralateral field or under the fixation spot for 480 ms. The shape moved behind the slit for 773 ms, with a 6.2°/s speed. At any instant only 1/10 of the shape was visible through the slit. We used two control conditions: a feature-preserved temporal randomized stimuli presentation in which the duration of the stimulus presentation was the same, but slit-views of 80 ms duration were presented in a randomized order to eliminate the coherent form percept, and another one, where the same slit-views were presented in their correct order.
Single neurons showed diverse activity. At the population level, firing activity for the slit-views was significantly lower than the response to the static whole shape stimuli. For testing the neuronal activities of all slit-conditions we used a three-factor analysis of variance design with the following factors: shape (best, medium, worst), stimulus type (original, correct order control, random control), motion direction (rightward, leftward, upward, downward motion). The shape selectivity of the static stimuli was preserved for the slit-views. We observed a significantly higher firing activity for the slit-views of the original than for their randomized presentation. However, the shape selectivity was preserved in the responses to the random stimuli and we also found a significant effect of motion direction.
The differences between the coherent shape and randomized presentation can be explained by the temporal summation of responses for the neighboring views of the effective features, which are presented in a succession in the original presentation, while these features may be split or followed by ineffective body parts causing masking effects in the randomized condition. Altogether our results did not confirm the existence of a slit-invariant whole shape representation in the anterior body patch. A preferred feature coding explains better our results.
References
1. Anstis SM, Atkinson J (1967) Distortions in moving figures viewed through a stationary slit. Am J Psychol 80:572–585.
2. Orlov T, Zohary E (2018) Object representations in human visual cortex formed through temporal integration of dynamic partial shape views. J Neurosci 38(3):659 – 678.
3. Parks TE (1965) Post-retinal visual storage. Am JPsychol 78:145–147.
4. Yin C, Shimojo S, Moore C, Engel SA (2002) Dynamic shape integration inextrastriate cortex. Curr Biol 12:1379 –1385.
Keywords:
Temporal Integration,
anterior body patch,
shape representation,
Feature representation,
anorthoscopic perception
Conference:
13th National Congress of the Belgian Society for Neuroscience , Brussels, Belgium, 24 May - 24 May, 2019.
Presentation Type:
Poster presentation
Topic:
Behavioral/Systems Neuroscience
Citation:
Bognár
A and
Vogels
R
(2019). Whole Shape or Feature Representation?
Neuronal Coding of Dynamic Partial Shape Views in Macaque Anterior Body Patch..
Front. Neurosci.
Conference Abstract:
13th National Congress of the Belgian Society for Neuroscience .
doi: 10.3389/conf.fnins.2019.96.00057
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Received:
25 Apr 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
PhD. Anna Bognár, KU Leuven, Leuven, Belgium, anna.bognar@kuleuven.be