Post-graduate theses
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| Identifier |
000463634 |
| Title |
Encoding and suppression of distracting salient stimuli in the prefrontal and parietal cortices |
| Alternative Title |
Κωδικοποίηση εξεχόντων αποσπαστικών ερεθισμάτων στο βρεγματικό και προμετωπιαίο φλοιό |
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Author
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Αντωνιάδου, Αλεξάνδρα
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Thesis advisor
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Γρηγορίου, Γεωργία
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Reviewer
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Σαπουντζής, Παναγιώτης
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| Abstract |
Ignoring visual distractors that capture attention is equally important as focusing on relevant information to guide goal-directed behavior flexibly. This ability is essential to our cognition and has played an important role in evolution. Yet, while much has been learned about selective attention, the mechanisms that underlie visual distractor suppression and its connection with goal-relevant stimulus facilitation remain poorly understood. Neural correlates of bottom-up and top-down attention have been reported in both the prefrontal and parietal cortices, however, their distinct contribution to the encoding and suppression of salient stimuli remains unclear. In the present study, we investigated how neuronal populations in the lateral intraparietal (LIP) area and the frontal eye field (FEF) of non-human primates contribute to the encoding and suppression of irrelevant, prominent distracting stimuli in a visual search task. To this end, we used simultaneous recordings from LIP and FEF to quantify the time course and magnitude of these effects, measured in the firing rate of multi units and single units in each area. We assessed whether these modulations emerge earlier in one of the two areas and whether they are prominent in specific subsets of neurons within each area or in distinct types of cells (e.g., visual, visuomovement neurons). Moreover, we used decoding analyses on the population activity to examine differences in the way distracting information is encoded and suppressed by the neuronal population in LIP and FEF. We also applied neural subspace analysis combined with decoding methods to address how neuronal activity shapes target selection and distractor filtering.
We found that the salient distractor was encoded earlier and more prominently in a subpopulation of LIP, whereas the suppression of the irrelevant salient stimulus emerged earlier and was more pronounced in the population of FEF. Furthermore, LIP’s suppressive effect was stronger and essentially present when the target was found with one saccade, unlike in FEF, where the suppression did not depend on how fast the target was identified. This finding may indicate stronger competitive mechanisms between neuronal populations encoding the location of the target and salient distractor in LIP and a more prominent role of FEF in suppressing irrelevant information to efficiently guide saccades. A cell type specific analysis did not reveal a distinct contribution of visual or visuomovement neurons to the salient distractor induced effects. Decoding analysis revealed that location information about the salient distractor emerges earlier in LIP but activity in FEF evolves to contain more information later, whereas information about the target location emerges first and more prominently in FEF. This result supports the role of FEF in identifying the location of relevant stimuli and suppressing distractors during visual search tasks. Subspace analysis showed that information about the location of the salient distractor and the target is contained in partially shared subspaces of neuronal activity in both areas, shedding light into how the representations of relevant and irrelevant stimuli are shaped at the population level during active search.
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| Language |
English |
| Subject |
Βρεγματικός |
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Προμετωπιαίος |
| Issue date |
2024-04-17 |
| Collection
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School/Department--School of Medicine--Department of Medicine--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/c/d/5/metadata-dlib-1712660562-497656-16975.tkl
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| Views |
2 |
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